Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Straiga on April 07, 2004, 09:07:41 PM
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I have noticed in AH, say your in cruise flight and set the prop RPM, say at 2000 RPM and manifold pressure set constant that when you push the nose over and increase the speed of the plane that the prop RPM will increase too! This dicription is a fixed pitch prop not a constant speed prop like the ones used on WWII fighters
When you set the prop RPM on a constant speed prop system, you move the prop handle to set the rpm then the prop governer maintains that rpm with either oil pressure through the the prop governer to set blade pitch or by counter weights.
The points is when the prop governer is set to a rpm setting and with an unchanged manifold pressure setting(No throttle change) what ever your going to do rolls, spins, loops, high speed nose dives, slow speed climbs the prop rpm will remain the same as it is set until a new rpm setting is set.
I have also noticed that in accellerated stall condition the airplanes rolls to the inside of the turn when the stall accurs, this should be opposite.
The lower wings has less angle of attack then the high sided wing when high Gs are pulled to a stalled condition the high side wing stalls the lower wing is still producing lift so the airplane rolls in the opposite directions of the turn. This is an accellerated stall condition.
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Surprise! When you increase speed far enough to allow airflow to turn your prop, it becomes a fixed-pitch prop. Why is this? If you set 2,000 RPM and then dive to 450mph, the airflow is moving so fast that it pushes more air against the prop blades. This increases RPM. The prop governor then dials the prop pitch clear down to the stop in an effort to maintain last-set RPM. Unfortunately, you're going so fast that it has no effect because the governor can't feather the prop. So your prop is now fixed-pitch. Congrats! You melted the main crankshaft bearing and ruined the engine. See this article for a more thorough explination...
http://www.avweb.com/news/columns/186778-1.html
Also, your description of a prop governor is all wrong. A prop governor uses fly-weights on a central shaft to actuate an oil valve that controls oil pressure to the prop hub. At least on Hamilton-Standard props. The Aeroproducts (P-51's) used a system enclosed behind the prop hub, while the Curtiss Electric used an electric motor. By moving the oil control valve (or electric motor) the prop blades engaged a central shaft via a beveled gear. Only the Curtiss could go to full feather without dumping oil. Late-model Ham-Standards used an oil dump system that ported oil from behind the hub overboard in an emergency. Otherwise there was always enough oil behind the hub plate for idle-RPM.
Accelerated stall are not a "high/low" wing condition. An accelerated stall happens when you crank the wing AoA up so fast that the airflow over the wing becomes disrupted. One wing (usually the left) will stall out first because the prop wash is not even. It spirals off the prop and over the wings, creating uneven lift.
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Flakbait [Delta6]
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During my LOA for a P-51, this was demonstrated . The prop govener works the way its supposed to, set the RPM then it maintains the RPM Hence the name Constant Speed Props. We set a constant manifold pressure and a sett RPM we did power on stalls, rolls, dives, chandels you name it the prop maintain the same RPM.
Pilots in WWII did not have time to adjust rpm all the time they usually set RPM and had there hand on the trottle for power when they need it. They didnt have to worry about RPM settings is was set already.
This article you are mentioning is about prop pull and prop push on the were and tear on the bearing assemble and crank and piston. When Either the Engine pulls or Prop push on the engine assembly. It also talks about shock cooling in big radials on desent. What power and RPM settings to maintain a constant Temp on an normal asperated engine not as bad of problem on a supercharged engine they run hotter and you can maintain cooling better on desents.
There are also vibration settings to stay away from that would set up bad resonence in the engine and do major damage. But nothing said anything about prop over speed because of airflow through the prop disk. This is a problem on an fixed pitch prop but not on an constant speed prop.
A constant speed prop is what it means constant speed. Prop pitch varies to maintain a constant speed to a set RPM. Airflow then pushes the prop into the crank (prop push) this is what the article is talking about where you ruin bearings and the such, but prop RPM remains the same. With a constant speed prop system you can shut down the engine and go to full feather anytime you want, when you start the engine and go to prop pitch again the accumilaters will take it out of feather so you can set the RPM again.
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Accererated stalls are yes an ubrubt disturbance of airflowover the wing. You can stall an airplane at any airspeed any altitude and any angle of attack. But in a high "G" turn the lower wing is at a lower angle of attack then the high sided wing which has stalled first and the low wing climbs and rolls the airplane in the opposite direction of the turn. Power or power of no matter.
This is demonstrate to all my student pilots so they can demonstrate this to the FAA so they can get there Pilot certificate. Its in the PTS for certification.
Its funny that the airplane either in a left or right hand turn always rolls to the high sided wing every time. Try it.
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Hi Straiga,
>The prop govener works the way its supposed to, set the RPM then it maintains the RPM Hence the name Constant Speed Props.
From the Pilot's Notes for the Spitfire II:
"(i) Constant-speed airscrew.- At maximum r.p.m. 3,000 , the throttle must be 1/3 open. The pitch control need not be brought back to reduce r.p.m., the range of pitch is enough to hold down the r.p.m. at any airspeed."
Note that this is at reduced throttle. Add more throttle, and the propeller will overspeed.
Regards,
Henning (HoHun)
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Originally posted by HoHun
"(i) Constant-speed airscrew.- At maximum r.p.m. 3,000 , the throttle must be 1/3 open. The pitch control need not be brought back to reduce r.p.m., the range of pitch is enough to hold down the r.p.m. at any airspeed."
Note that this is at reduced throttle. Add more throttle, and the propeller will overspeed.
Regards,
Henning (HoHun)
If the pilot has separate pitch control (rather than pitch control from a governer driven by rpm setting) is it really a constant speed prop? isn't it really a variable pitch prop?
The difference is between a pilot that has to balance throttle and pitch (ignoring mixture) to arrive at optimum rpm and boost whilst ensuring that neither exceed limits and a pilot that sets rpm and then varies throttle to set boost confident that neither will exceed max setting whilst always able to reach it.
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Originally posted by Straiga
But in a high "G" turn the lower wing is at a lower angle of attack then the high sided wing
Still tryin to get my mind round this............... I am going to have to draw it........ I always thought that the lower wing had the higher angle of attack and was marginally slower than the higher wing. (assuming the turn is maintained in the horizontal plain)
Hence I believed the lower wing lost lift...............
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This may explain something .........
Students are taught to avoid steeply banked turns at low altitude. If you overshoot the extended centreline on a turn from base to final, there is a tendency to “cheat” by applying inside rudder to increase the rate of turn – which requires opposite aileron to maintain the bank angle. The skidding turn tends to make the nose drop requiring back pressure on the control column.
In an extreme case, the result can be a full back control column with full opposite aileron and full inside rudder. The inside wing will stall first resulting in a sudden incipient spin. This is sometimes referred to as an “under the bottom stall”.
A top-rudder stall or “over the top stall” can occur when the aircraft is slipping. The aircraft should roll towards the higher wing at the point of stall.
From elsewhere it seems that the direction of roll is more dependant upon the element and direction of "cross control".
We all know we can induce a very unstable but high rate of turn thru ruddering with a turn (ie down wards)and compensating for lift with aileron and increased elevator. It seems this induces a different roll direction upon stall to that of a more conventional turn where rudder is used to kep the nose up.
I wonder if the use of a twisty grip rudder influences the type of cross contol used when in combat.
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Surprise! When you increase speed far enough to allow airflow to turn your prop, it becomes a fixed-pitch prop. Why is this? If you set 2,000 RPM and then dive to 450mph, the airflow is moving so fast that it pushes more air against the prop blades. This increases RPM. The prop governor then dials the prop pitch clear down to the stop in an effort to maintain last-set RPM. Unfortunately, you're going so fast that it has no effect because the governor can't feather the prop. So your prop is now fixed-pitch. Congrats! You melted the main crankshaft bearing and ruined the engine. See this article for a more thorough explination...
AHHHHH so this is why in IL2 when you are in a steep fast dive you hear the RPMs increase. It is a very cool affect and heightens the immersion factor.
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Originally posted by Tilt
If the pilot has separate pitch control (rather than pitch control from a governer driven by rpm setting) is it really a constant speed prop? isn't it really a variable pitch prop?
The difference is between a pilot that has to balance throttle and pitch (ignoring mixture) to arrive at optimum rpm and boost whilst ensuring that neither exceed limits and a pilot that sets rpm and then varies throttle to set boost confident that neither will exceed max setting whilst always able to reach it.
If you have a direct pitch control, instead of an RPM control, then it's a variable pitch prop instead of a constant speed prop. I think the only AC we have that used this sort of system was the Bf-109. All the rest had a constant-speed.
Constand speed props set engine RPM to a given point, and through either oil or an electric motor the prop pitch is changed to maintain that RPM. Hence the reason over-speeding a prop can be a VERY bad thing for your engine. Variable pitch props only controlled prop pitch, not engine revvs, which made flying with this prop a lot like playing a three-handed piano. Adjusting pitch meant the engine speed would change, so you had to fiddle with the throttle and mixture to avoid over-revving it.
As for the under-bottom stall, it does happen. However it only happens when you crank in a lot of rudder at very low airspeed and rather high bank angles. Usually in AH the tendency is for the aircraft to stall on the left wing (right wing for the bass-ackwards engines). So you can dial in some rudder to increase turn speed without getting into a stall. However, I've never seen or had this happen to me and I do use a twisty stick. Then again, I don't like playing the low-speed stall-fight games some guys prefer. I've used some rudder to delay an oncoming stall in a turn more than once during practice. But I've never had an under-bottom stall occur. It might be a difference between AH modeling and the way a real aircraft handles. I'll check it in AH2 to see if this characteristic is present.
Striaga: The prop pitch in any aircraft is limited by a physical stop inside the prop dome. You can not get the prop angle below that stop, it's impossible without a feathering system. Also, when you increase airspeed with a low RPM setting, eventually you'll hit the point where the prop begins to drive the engine. When this happens you have a very finite amount of time to either firewall the prop lever or start dumping speed. 30 seconds was the limitation in most engines for this to happen, typically at 3,050 RPM and no higher. If you failed to take any action the crankshaft main bearing would melt, ruining the engine.
Now if you set 2,000 RPM with 48" MAN and proceeded to dive, the prop angle is set too high. As you pass a given airspeed, the engine/prop is no longer generating enough thrust to offset the increase in speed. So the prop starts turning faster (driving the engine with the prop shaft) while the governor tries reducing the prop angle. Once the adjustment plate inside the prop dome hits the fixed stop on the cam the prop becomes fixed-pitch. All WW2 era props except the Curtiss Electric had/have a mechanical stop. The governor can not adjust the prop angle any lower, and your engine speed starts climbing. This is why you saw the RPM gage climbing after setting 2k RPM and diving.
Try it in any constant-speed prop aircraft that can move faster than 200 knots. Pull the RPM back to 1,500 and dive the aircraft until you see the RPM climb. It can and will happen. Constant speed props have mechanical limits that most people never see simply because they aren't that dumb. No one wants to have their crank sieze up or plow a hole in the ground. Take the time and actually read that article I posted, along with several others Deak has done on props.
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Flakbait [Delta6]
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Originally posted by flakbait
If you have a direct pitch control, instead of an RPM control, then it's a variable pitch prop instead of a constant speed prop. I think the only AC we have that used this sort of system was the Bf-109. All the rest had a constant-speed.
la5Fn pilots had to vary pitch and throttle (and mixture) separately.
la7 introduced the constant speed prop and latterly linked mixture to throttle control.
I believe numerous early war ac had variable pitch props but not constant speed props.......... I always thought early spits and hurricanes were without it.
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Hi Tilt,
>If the pilot has separate pitch control (rather than pitch control from a governer driven by rpm setting) is it really a constant speed prop? isn't it really a variable pitch prop?
The name "pitch control" is an anachronism. In other places in the manual, it's called "airscrew lever".
From the same manual:
"Airscrew.- This is a Rotol variable-pitch type governed by a constant-speed unit. The pilot's control regulates the engine r.p.m. through the action of a governor unit which controls the airscrew pitch according to the power output and in relation to the airspeed."
Note that the propeller itself is considered "variable pitch", but the entire system is "constant speed".
Regards,
Henning (HoHun)
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So is AH and AHII modeled incorrectly, since you don't hear RPMs increasing when you are in a steep 400+ MPH dive? Like IL2 does.
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It does increase with speed.
HiTech
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I have not noticed the sound increase, I know you guys were still working on rpm and sound etc.
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I've always noticed it since a long time. It's not as dramatic as Il2's, might be the difference between a melted main crankshaft bearing and one that's not?
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No game, to the best of my knowledge, models engine wear and tear to that degree. The difference between AH and IL2 is mostly one of programming, as both model this phenomenon. Neither, however, model props driving engines to any accurate degree. Aside from an RPM increase, we don't see any damaging side effects. Which is probably a good thing, since many pilots here would prefer to worry about the enemy vs. how they're handling the engine.
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Flakbait [Delta6]
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Yeah, I could care less about the damage affect, although it would stop alot of people from running and force them to fight. That would be a good thing. :D
But I didn't notice the increase in RPMs in a fast dive till I started flying IL2. The next time I am in AHII I will pay better attention to it. It is really dramatic in IL2 and adds to the overall immersion factor. It reminded me of the films you see when a pilot noses over and dives in.
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Actually it wouldn't stop anyone from running. As long as the engine and prop are making enough power, the prop can't drive the engine. It takes quite a bit to get an aircraft to that point really. I haven't played Il-2 in a long time, but if they model an RPM increase just from diving then they got it wrong.
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Flakbait [Delta6]
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I haven't played Il-2 in a long time, but if they model an RPM increase just from diving then they got it wrong.
OK then what are we saying in this thread. It was stated once you dive to the point where you are up against the stops your prop basically becomes a fixed pitch prop and you would then see an increase in RPMs. Hitech mentioned this is what happens, so what do you mean in the above quote?
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Aw Geez..answer, please. I've read this far and it's like someone ripped the last page from a book or article.:(
edit: great thread, btw.:D
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Mars, I'm saying that it takes a lot to get to the point where you've got a problem with the prop driving the engine. At very low power and low revs, diving from a great height will get the prop driving the engine becaue the prop/engine combo is putting out squat for power. The high-speed airflow over the prop starts turning it faster than the engine is, and that's where things get nasty. If Il-2 is modeling it so when you dive from 350mph to 400mph at mil power, and you see an RPM increase, then they've got it all wrong. A dive like that even at cruise power settings won't cause the prop to drive the engine. The reason why is simple; the engine is still putting out enough power to prevent it. HTC has modeled it about right: diving with low power and low revs will, eventually, cause the prop to drive the engine. Key word here being eventually. It doesn't happen all the time, only under specific circumstances with certain power/RPM settings can you cause this to happen.
Here's two examples of how to drive the engine with the prop...
1) Take the Spit driver diving from 25k to avoid getting nailed by a P-47. By 400mph TAS he's cooking at full power with his nose 25º down. By 475mph he's reached a point where more than likely he can't chop power. If he does then his engine is not producing enough kick to drive the prop. So the airflow over the prop starts back-driving the engine along the extention shaft. You can see this in action in either AH or AH2 by taking a P-51D up to 25k and diving it to 500mph. Watch for an RPM increase past 3,000 and as soon as you see that, cut power. That is a situation where the airflow is moving air faster than the prop is, and as a result, the prop is driving the engine. Airspeed alone can cause the prop to drive the engine if the airspeed is high enough.
2) Use a last minute decent procedure by chopping power completely while in a steep dive towards the airfield at a medium altitude. Use cruise power (try 40" 2,300) in any aircraft at 15k and let it settle. Now cut power and dive the aircraft while watching for the RPM to climb above 2,300. Again, airspeed alone is moving the prop faster because the prop thrust is slower than your airspeed.
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Flakbait [Delta6]
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flakbait, someone who plays FB on a regular basis will have more accurate anecdotes, but I can tell you the first times I played I was often burning and braking Hurricane engines.
It started with strong dives where I must've forgot to use the right throttle and pitch procedures, the engine would quickly over rev.
Afterwards if it hadn't caught fire, the RPMs would overreact (don't remember by how much, i never bothered to look and just remember by ear, it was real spiky) to any throttle imputs, independent of plane speed and orientation.
The engine RPM had very elastic reactions.
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Gentalmen, your points are well taken and have some vilidty.
A fixed pitch prop is a solid piece of metal or wood set to for a climb, cruise or combo of both to get the performance you want.
RPM is what you read in the cockpit not manifold pressure this is the only gauge showing power.
When you enter a dive with a high RPM setting your prop will over speed past red line and severly damage your engine. Power reduction is required for desent or any nose low attitude to keep RPM below red line. In a climb you will never be able to over rev a fixed pitch prop. RPM will decrease with increase of angle of attack to the max power output from the engine.
Constant speed props is a variable pitch prop that you can vary prop pitch with the prop handle, full forward is high RPM low Blade pitch, move the handle back this changes the prop govener (either electric, oil pressure or what ever) to a desired higher pitch low RPM setting. Move the handel all the way back this will feather the prop on some airplanes . Some radial or inline engines have prop reverse, this is were the prop angel of attack goes to a neg angle or beta range.
Blade stops range from high RPM to feather, some have no blade stops at all (Prop reversing ) So airplanes have many different configurations of a constant speed system, and the prop blade angles vary dramaticly depending on how big the blade is.
When you take a fighter and dog fight with it your in a low airspeed range but never in the never exceed airspeed range of the airframe, unless your trying to beat the other guy to the deck. I have noticed in AH that you could be going about 150 then nose over to 300 and watch the prop rpm climb Im sorry this is not possible a constant speed prop system will prevent this from happening. I can see this if you got the airframe up to close to red line, when some props hit the blade stops yes RPM will increase but the angle of the prop blade at its stops, takes a while to spool up you will have probably rip your wings off about the same time you have over sped the eng who knows or reduce power and still watch your wings fall off. Excessive I mean excessive airspeed yes you can over speed. But in a wide envelope range normally, RPMs can be managed by setting the prop RPM. Some Airplanes can go to feather no over speed and this is not a normal practice.
But what im saying in AH when your dog fighting and you want to maintain a set RPM it wont do this, the prop rpm will rise or fall depending on nose attitude. Constant speed props were designed to maintain a set RPM or why have them?
Accelerated stalls are just as I decribe. No rudder at all.
Using aileron to counter torge it is still wrong Im sorry. If your were to use right aileron to counter a left torgue tendancey the left aileron would be deflected down increasing chord length
increasing angle of attack, there for increasing lift which increases drag slowing that wing up yawing the airplane in the same direction of the torge. Now you have to add rudder to counter this motion, and all you had to do in the begining is to add rudder in the first place to counter torgue, ailerons only bank an airplane then horizontal componant of lift turns the airplane. The right wing is also set at an higher angle of incidence then the left to counter torge (fix angle of attack of the wing mounted to the fuselage). The vertical stab is not centered to the airplane centerline either , the leading edge is moved to the left of center to counter torge along with rudder.
Aileron trim should is used for fuel weight inbalance meaning more fuel in the fight fuel tank then the left, or you dropped one bomb and still are carring one. Losing one engine on a multi you could use it to roll the dead engine into the good engine about 5 degrees this is counter drag not torgue. All the flying that I have done I have used airleron trim very little most of the time 99.9 percent its set to 0 and I dont use airleron to counter torge thats unheard of. In a real airplanes they fly so easy. In AH I have to laugh Im sorry that every time you have to trim the airlerons to make it fly straight wings lvl at different airspeeds because of torgue effect. I dont do that in a King Air 200 or B-767, MU-2, PC-12, Senaca, Piper Arrow or any other airplane get the point. Remember I teach student Pilots to FAA standards so they can get there certified pilots licences. Every two years I have to recertifie my CFI to keep current.
Also when you shoot the tail off an airplane the nose of the airplane will pitch down, not up. Because a resultant tail down force is produced by the horizontal stab to balanced airplane. The airplane first of all has a very heavy engine in front this makes for a nose down situation, second the center of pressure on the main wing moves aft at higher airspeeds this still makes a nose heavy situation you now need the horizontal stab to do its thing in the opposite direction to balance every thing out in flight, so when you shoot the tail off the nose pitches down not up. Just threw that in.
I would like to know if you guys have pilot licences? I not I would like to know were you get your aviation experinces from Im very interested.
I hold a Airline Pilot Certificate & Airplane Single & Multi Eng Land Rotor Craft Helicopter Instrument certified flight instructor rating, and also a Flight engineer Jet Rating. If you would like, I could send you copies of my certificates to showyou that im not blowing wind, send me your fax number.
Im presently with Hawaiian Airlines were I started as a flight engineer on the L-1011 then went to the first officer position, I then flew Md-83 for the inter-island side then went to the Boeing 717 after the company sold of the Md-83s. Another bid came out and start flying first officer for the DC-10 after those where retired and I now fly the Boeing 767-300 ER. Its great fun, till I reach 60.
Later see you on the Map
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Originally posted by Straiga
Also when you shoot the tail off an airplane the nose of the airplane will pitch down, not up. Because a resultant tail down force is produced by the horizontal stab to balanced airplane. The airplane first of all has a very heavy engine in front this makes for a nose down situation, second the center of pressure on the main wing moves aft at higher airspeeds this still makes a nose heavy situation you now need the horizontal stab to do its thing in the opposite direction to balance every thing out in flight, so when you shoot the tail off the nose pitches down not up. Just threw that in.
Hi Straiga,
I believe the behaviour of the aircraft in AcesHigh in that respect is correct. I think there may be some confusion in this discussion regarding the system of forces involved for the stability of an aircraft, particularly when you try to apply that to explain what happens when the tail has been shot away.
Allow me to explain what happens… Let's assume that you are flying along, minding your own business, in level flight at constant speed. Further assume that the forces on your aircraft are balanced. The prop’ thrust is balanced with drag, the lift with weight and so on. All the moments are balanced too, the pitching yawing and rolling moments are all in equilibrium. The nose down pitching moment caused by the weight and lift couple is balanced at the tail, and so on.
Now, since you raised the question about what direction the nose points when the tail goes away, let’s just think about those longitudinal pitching moments. Most folk, including you, think like this… During flight the weight and lift couple was trying to rotate the nose downwards, and the tail was preventing this from happening by providing a downward force. So, if we remove the tail, there will be nothing to prevent that rotation, and the nose will drop… Not so fast! That’s not what happens, you might not see this right away, so bear with me, I’m going to go slowly… But first, the flaw in that reasoning is that it overlooks the fact that the nose down pitching moment that existed during controlled flight, also goes away with the tail. You see, the tail wasn’t only responsible for the balancing moment, it was also indirectly responsible for the lift that produced the nose down pitching moment in the first place. Once the tail has gone, the forces normally associated with static/dynamic stability no longer apply… So what does happen?
Firstly, the wings are only producing lift when they are forced to do so by the control surfaces at the tail. Those surfaces (using a small force but long lever arm) rotate the wings against the airflow, forcing the wings to fly at an angle to the free air stream, thereby causing downwash, circulation, and thus lift. When the elevators go away with the tail, the lift goes away with it, and the wings weather vane, and no longer produce a nose down pitching moment. That all happens very quickly and only leaves an engine, with the wings and forward/mid fuselage acting as little more than dead weight that simply wants to fall downwards, with a propeller attached to it that is still producing thrust.
Now, all you really need to consider at this point is how a heavy lump of metal with a propeller attached to it would fall. I think most people can see intuitively, that the heavy lump would fall first, dragging the propeller behind it. An admittedly weak analogy would be the stable condition that arises with a man hanging beneath a parachute. The aircraft falls, dragging the prop behind it, and falls more slowly because the prop is producing thrust and slowing it down.
That's exactly what happens in AcesHigh... Kudos HT!
Hope that helps.
Badboy
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Hi Straiga,
>I have noticed in AH that you could be going about 150 then nose over to 300 and watch the prop rpm climb Im sorry this is not possible a constant speed prop system will prevent this from happening.
Funny the Spitfire manual should advise to reduce boost to 1/3 to avoid excessive rpm then. I guess they didn't know any better because they lacked the Piper Arrow flight experience.
Regards,
Henning (HoHun)
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Hey Badboy,
I see your point, BUT here we are flying fat dumb and happy and one of the LTARDS shoots your tail off, the center pressure on the main wing moves aft at high airspeed or moves forward in low speed high angle of attacks. Im talking cruise flight COP is aft we have a big engine on the nose and the tail goes away, at that instance with the center of pressure aft on the wing pitches nose down because you lost your balance from the tail plus with the big engine on the nose dose'nt help either. After this later I can see a wing pitch up and vaining. But not on the onset of losing the tail.
Hey Ho Hun,
If your implying that a piper arrow can go as fast as a spit II in a dive the arrow would probably win the race since it wouldnt have any wings anyway and prop over speed cituations would no longer be a factor!
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Hi Straiga,
>If your implying that a piper arrow can go as fast as a spit II in a dive the arrow would probably win the race since it wouldnt have any wings anyway and prop over speed cituations would no longer be a factor!
Well, actually it was a failed attempt at irony.
If a WW2 fighter manual says that you should pull back the throttle to 1/3 in a dive, it's obvious that propeller overspeed was a factor even though the aircraft was fitted with a constant speed governor.
I don't think that it's possible to invalidate the WW2 fighter manual based on Piper Arrow (or modern turboprop) experience.
Regards,
Henning (HoHun)
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It's realy simple if you understand stops on the prop. Infact had to have mine adjusted on my RV becase past 175 knots it started to change. I could no longer hold 2400 rpm it would start to creep up.
With the debate which way would an aircraft pitch when tail feathers are gone, the answere is they could pitch both ways. It just depends where the CG / CP releationship is prior to loosing the tail. And please don't sight that the CG is always head of the CP, because that is incorect. The CG must be head of the combined CP of the tail and wing only to create a stable aircraft.
Also if your going to debate torque, please be specific, because by strick definition roll is the only thing that counteracts engine torque. Other wise you probably refering to PFactor or slip stream effects.
As to which way a plane rolles when stalled in a turn, life is not so simple. It can go both wayes, because I can assue that I have done 4 g accelerated stalls in real dog fights and had the plane snap both ways, including in a p51. It realy depends on the specific air craft, and where the, ball is along with bank angle when max aoa is reached.
HiTech
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Originally posted by Straiga
I see your point, BUT here we are flying fat dumb and happy and one of the LTARDS shoots your tail off, the center pressure on the main wing moves aft at high airspeed or moves forward in low speed high angle of attacks. Im talking cruise flight COP is aft we have a big engine on the nose and the tail goes away, at that instance with the center of pressure aft on the wing pitches nose down because you lost your balance from the tail plus with the big engine on the nose dose'nt help either. After this later I can see a wing pitch up and vaining. But not on the onset of losing the tail.
The location of the COP doesn't matter once the tail is gone, because when the tail goes away, the lift on the wings goes away as well. Of course in reality it doesn't go away instantly, so at the moment the tail is lost, the nose down tendency does exist, as you point out, but the lift decays very rapidly, so it would only be momentary (and damped by the nose up moment from the vertical component of thrust at the prop') and insignificant compared to the more massive, long term and stable motion we see correctly depicted by the flight model in AcesHigh.
Leon "Badboy" Smith
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I disagree bad boy, The lift still is what will determine which way it will fall. The wing will generate lift unless it is at 1 specific AOA so if any pitching occours the wing is what will generate the stable fall condition. All that is changing is which end of a dart the feathers on. In the nose up case the fethers are on the front side of the plane. Nose down case fethers are on the back.
HiTech
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Torgue is a roll moment but to an aitplane its is countered by rudder not airleron.
Lets take a P-51, its a tail dragger the nose sits in a high angle of attack to the relative wind which is paralle to the runway, P-factor, prop slip stream and gyro pressesion is all present at the onset of power application.I
In AH on autotake off you see the airlerons move up and down at the intial onset of takeoff power, why are they moving I dont know and rudder doesnt move at all. 1. There is no airflow across the wing at zero airspeed to make airlerons effective. 2.Rudder is in the prop stream and is the major control device thats is controlling the airplane from a left turning motion at this time. 3.Elevator is also efective because of slip stream. Torgue is trying to roll the aircraft to the left along with P-Factor, prop slip stream and gyro-prossesion which moves to the right. Rudder is used to counter this moment airlerons are not effective still, not enough airspeed to counter anything. The left landing gear is now the pivet point and is bearring the brunt of the torgue. The plane is not going to roll over on the ground but will pull to the left because of drag and weight on the left main tire, it feals like the brake is applied. Power is applied smoothly if you run out of rudder and the planes still is pulling to the left get of the power there is nothing else thats going to stop you from going off the left side of the runway except this or cheating with brake on the right side.
Around 45 kts airlerons become effective it varys on different airplanes, but this still doesnt counter torgue you cant roll an airplane still on the runway rudder is still used . Once you get airbourne everbody thinks the airplane is going to roll opposite direction of the torgue this is not true. Rudder maintains direction controll fine and roll moment. Now suppose we use airleron in stead of rudder after takeoff here is whats happens you roll the airleron to the right to counter torgue, the left airleron moves down increases angle of attack, increases cord length, increases lift and increases drag. Which slows the left wing, the right wing speeds up due to decrease in lift and drag now the airplane yaws to the left in the direction of the torgue if more airlerons is used to counter this left turning moment this situation gets worse the same is true on the runway. If your trying to maintain a heading after takeoff this is not possible the airplane keeps pulling to the left if you were not use right rudder while the airleron is used you would be cross cordinated the ball would not be centered and you could not hold a heading but drift only to the left.
But in AH, airleron is only used with no rudder. Now if you took off with no autopilot all you need is rudder no need for airlerons. I dont understand by watching the airplane on takeoff in auto whats its trying to do. The airplane moves left and right on the runway with airlerons deflection , on full power application, as the wheels start turning there is no airspeed to make airlerons effective no airflow, but the plane moves left and right anyway because of this, and the rudder doesnt even move. UHH! Please explain. By using no autopilot on takeoff this is a more realistic takeoff using rudder only with no need for airlerons for roll moment.
Yes you get a roll moment from torgue but airplanes are designed with anti left turning moments. The right wing is mounted to fuselage at a higher angle of incidence then the left wing, the vertical stabilizer is mounted to the fuselage with more angle of attack to the left side of the airplane. the engine is mounted nose down and to the right from the center line of the airplane this is all to counter torgue, slip stream, P-factor.
If you were to lose airlerons in flight, say the cables broke or something your roll moment can be aquired by rudder. Rudder is also used to cordinate the airplane in a turn, when you roll into the turn, you use rudder into the same direction of the turn because in a turn the lower wing always speeds up pushing the nose in the opposite direction of the turn you use rudder to bring the nose back in the direction of the turn. Airlerons only gives you bank angle for a turn, horizontal componite of lift is what turns an airplane.
Crosswind takeoffs is were you use airleron for take off. You start with full airleron deflection into the wind as airspeed increase you minamise airleron as they get effective enough to kill the drift, use rudder to point the nose this is a forward slip take off. Once airbourne use rudder to hold heading and airleron is no longer required.
Rudder is used to stop the roll moment on takeoff not airleron.
Multi-engs have the same principle but a little differant in an engine out condition. I have a lot of high performance twin time (King Air 200 & 350) to name a few and my right foot gets a work out on takeoff.
Thanks talk at you later.
Hitech what kind of RV you have? I have help build and fly some friends with a RV - 6 and 8 funs toys.
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The ailarons move simply because they are trying to keep the plane level. Even if they have no efect the auto pilot will try keep the plane level. The gain on the autopilot is increased as you slow down, so when just starting the take off roll they are extreamly sensitive. Think what would happen to a real plane if you turned on a wing leveler autopilot at take off.
The rudder is what the auto pilot is useing to keep the plane going straight down the runway. It's not doing anything different than if you were not using auto pilot.
The left yawing tendency that you correct with rudder, is not caused by engine torque, but by the other forces you describe. Engine torque produces a roll.
Rudder alone will not produce much roll , the resone you get a roll when using rudder is do primarly to diheadral of the wing, When you induce a yaw with the rudder the forward wing recieves a greater AOA than the trailing wing. This is what produces most of the roll. The other componet , but this is the small effect is because the rudder is typicly position above the Roll cg axis. Hence inducing a roll torque. With straight wings almost no rolll can be observed, with planes with a lot of dihedral a full 360 barrel roll can be complete with rudder. Done this with a lot of RC planes.
you use rudder into the same direction of the turn because in a turn the lower wing always speeds up pushing the nose in the opposite direction of the turn you use rudder to bring the nose back in the direction of the turn.
Wouldn't that be the high wing speeds up?
There are other forces at work here also, the ball simply messures the side force on an airplane, when in a steady state turn there is a slip created from different directions on the air plane, i.e forward section and rear section recieving different directions of air flow, just to mention one. Centering the ball balances all these yaw forces along with the difference in drag of the wings.
As to how wings are attached, AH has those setups, in AHII one of the things we fined tuned was to be able to put more detail into wing washout, hence ruducing tip stalls, and a finer adjust ment on wing twist to counter torque.
My toy:
RV8 IO360 200hp with inverted oil system. Looks like it will be a great evening to do some more cuban 8 and slow roll practice.
HiTech
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The high sided wing will slow up due to the airleron, its moves down and increases the angle of attack and increases lift, there for increase drag which slows the wing down, the nose goes to the opposite side of the turn, there for you need rudder to be cordinated. The lower wing is just opposite.
Hey Hi tech the RV-8 is a great flying airplane. I have about 30 hrs in one. Good machine.
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Your desribing the rolling into a turn, once in a steady state turn the hi side / outside wing is travling further do to the fact it is on the outside of a circle. Hence it is travaling faster.
HiTech
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Yes I was talking about the intial turn once your in the turn and bank angle is established all the control surfaces are neutral and cordinated except for elevator which is continually maintaining altitude. Once your in the turn the horizontal componate of lift turns the airplane, elevator is used in the turn because of decreasing vertical componate of lift.
Torgue effect roll is managed by rudder, both in single engine and multi-engine opperations even multi-engine with single engine failure. Whether you have dyhedrial or not.
Rudder is very effective it sits in the prop slip stream. Mutli-engine airplanes have a very big vertical stablizer for single engine opperations.
I have an extensive library from basic flight training to advanced aerodynamics and there is nothing that I have ever read that airleron is used to counter torgue roll moment. If you have some information that says different send it to me.
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So why do they put the twist in the wings if not to counter engine torque?
Also in a turn the controls are rairly nuetrual.
HiTech
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so Hitech, just what exactly do we get for gifting you the $8,995 Garmin 430. And how about the $40 Scotch whiskey? :)
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Garmin: How about your choice from our list of planes to do next. And free arobatic RV8 rides for life when ever your in my area?
Scotch: Free office tour.
HiTech
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Originally posted by hitech
Garmin: How about your choice from our list of planes to do next.
This has me wondering what it would take just to see the list...
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Originally posted by hitech
Garmin: How about your choice from our list of planes to do next. And free arobatic RV8 rides for life when ever your in my area?
Scotch: Free office tour.
HiTech
Hmm, where is your area? I might move there! And, I warn you, I come from a long lived family. :) Btw, and pardon my ignorance,what is a RV8?
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Originally posted by Straiga
Yes I was talking about the intial turn once your in the turn and bank angle is established all the control surfaces are neutral and cordinated except for elevator which is continually maintaining altitude. Once your in the turn the horizontal componate of lift turns the airplane, elevator is used in the turn because of decreasing vertical componate of lift.
Straiga,
In the continous level turn the ailerons must be used to keep angle of bank constant. If the ailerons are in the neutral position and the elevator is used to keep altitude constant then the angle of the bank will reduce and the plane will come slowly out of the turn (assuming that the rudder is used just to keep "the ball in the middle"). Basicly during a continous banked turn the plane has a continous rolling moment.
gripen
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Hey Hitech, The King Air 200 I fly part time has two Garmen GNS 430s GPS slaved with an RS-232 to the autopilot and an Avidyne TAWS with terrain mapping feature. There good equipment just wish it had Vnav.
Gripen, Whats your CFI # or class certificate you hold. Im interested.
The DC-10 does great steep turns, roll it in to 45 degrees of bank, 4 1/2 degrees nose up and manage altitude with a little a back pressure. It holds bank angle quit well. You could also trim the back pressure and watch it turn all by itself, untill you roll it out yourself.
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Straiga,
I have no CFI certificate. I'm merely saying that a plane has a rolling moment during turn, that is a physical fact.
gripen
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Gripen,
Its true every airplane has a roll moment, but designers build stable and unstable airplanes in the roll moment due to the mission of the airplane. I teach student pilots and show them how a stable airplane can be stable in turn hands off. Go rent an airplane and try it. We can write back and forth about aero properties all we want but its hard to listen to a teacher, teaching you how to fly an airplane if he has never learned how to fly an airplane himself.
Its hard to teach stundents how to fly real airplanes who have never flown before. Not only do they have to know aerodynamics of an airplane but regs, airspace, navigation, weather and a hole list of things to pass a FAA check ride and oral exam.
I think computers pilots would be worse to teach. They already know everything and they wanna be a pilot, but the only way they will know how to fly is from the computer, which most airplane sims are about 60 percent accurate from the way an real airplane flys.
Its like the tiger tank in AH trying to fly with its tracks shot off shouldnt it be just a pet rock, or the way two airplanes run head on into each other both planes should be crippled right! wrong not in AH, now why is that. Its a computer game its crued simulation and is not real life but some people thinks its an accurate reflection.
The airlines uses sims to teach us procedures in case the real thing happens but these sims dont fly like the real thing, its a close simulation. All the switches and dials are real thats it. Also not every real airplane of the same make flys the same either.
Later
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Straiga,
Well, you don't have to teach me on this. Basicly all planes with neutral or positive lateral stability need a bit of ailerons (to the bank side) in the level turn. In the case of the laterally unstable plane aileron direction and amount varies depending on case.
gripen
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Originally posted by hitech
So why do they put the twist in the wings if not to counter engine torque?
I was thought that the wing twist was for giving the pilot some advance stall warning. The inner part of the wing would stall first, but since the wing is twisted the outer part (with the ailerons) still has normal airflow. Engine torque is countered by mounting the vertical stabiliser at an angle, usually set to cruising speed.
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Hi Straiga,
>I think computers pilots would be worse to teach. They already know everything and they wanna be a pilot, but the only way they will know how to fly is from the computer, which most airplane sims are about 60 percent accurate from the way an real airplane flys.
Gripen knows his stuff, and while he might be wrong, you should be able to point out exactly why. CFIing an internet discussion platform requires a rather different approach than CFIing in an aircraft.
And be prepared to be precise - inaccurate statements like those you made on constant speed propellers won't score you any credibility points with us wannabes.
Regards,
Henning (HoHun)
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lol HoHun :)
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Straiga: You are incorect about teaching computer pilots. Especialy those coming from somthing like AH. The instincts of how the plane reacts, especialy at departure time, are already all built in. They just need to be translated to a different enviorment.
And being one of those guys who first flew RC's and computers, then when on to flying the real stuff. I was cleared to solo at 3.5 hours.
When I started my areobatic training, instructor was amazed how easy it was for me to fly only looking out the side of the plane, this was simple for me, because ive spent lots of hours with that same sight picture in combat sims.
In general i've found that most pilots and CFI's have only a very limited understanding of the physics of flight. The only exceptions ive seen to this are when they have an engerining back ground, and study the physics of flight. Generaly they recite what they have been taught, and don't think about why it works that way, hence come to incorect conclusions.
GScholz: Your refering to washout. wingtwist is more or less incidence on left or right wing.
The rudder incidence is primarly for slipstream effects. Hence why I said early on in this disccusion, if your talking the general term "Torque" you can't have a physics discussion. You need to referer to which 1 of the 4 components your speeking of. And while rudder is used to correct the left turning tendency of a prop plane, that effect is not caused by engine torque, but by the 3 other effects.
HiTech
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Ok, I kind of knew it couldn't be that simple.
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What I have been saying all along is I find that AH and there aerodynamic modeling is close but when it comes to use of ailerons and aileron trim for torgue controll is totally inaccurate. You shouldnt have to trim aileron on an airplane trough all airspeed changes this is incorrect I dont do that in the real world, except for pitch trim, for every power change and pitch change you need trim change. I have flown alot of different airplanes in my 30 years of flying singles, multis, turbo props, jets, helicopters
We all know the left turning tendancies Torgue, Prop slip stream, P-Factor, Gyro-procession but there are others to force we have to tend to adverse yaw, preverse yaw, cross wind take off, asymmetrical power, and spin recovery. In addition to directional stability, the airplane must have adequate directional control to cordinate turns, balance power effects, create sideslip, balance unsymmetrical power, etc. The principal source of directional control is is the rudder and the rudder must be capable of producing sufficient yawing moment for the critical conditions of flight.
Gripen,
If you know airplanes, it would roll more into a turn than roll out of a turn by itself, its called over banking.
As you enter a turn and increase the angle of bank, you notice the tendancy of the airplane to continue rolling into a steeper bank, even though you neutralized the ailerons. This overbanking tendency is caused by additional lift on the outside, or raised wing. Since the outside wing is traveling faster than the inside wing, it produces more lift and the airplane tends to roll beyond the desired bank angle. To correct for overbanking for overbanking tendency, you can use small amount of opposite aileron, away from the turn , to maintain your desired bank angle.
GScholz,
You are correct about the vertical stab countering torgue. Wing twist is because of airleron deflection or excessive airspeed. This does nothing to counter togue. Some planes move the airlerons inboard to prevent twist. In excessive speed cituation the plane will roll opposite in the direction of the airleron deflection. The B-2 bomber uses wing twist and drag flap to stabilize about the yaw moment.
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To isolate torque from P-factor, slipstream, and gyroscopic effects, remove the prop from the plane and have the shaft terminate into a brake. Without the prop and therefore those other effects, you will see what direction the effect of torque has on a plane. Do you think a plane in that test configuration would try to yaw left or try to roll left? Or put another way, when you're driving screws with a drill, what does the drill do? Rotate or yaw?
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Originally posted by Pyro
To isolate torque from P-factor, slipstream, and gyroscopic effects, remove the prop from the plane and have the shaft terminate into a brake. Without the prop and therefore those other effects, you will see what direction the effect of torque has on a plane. Do you think a plane in that test configuration would try to yaw left or try to roll left? Or put another way, when you're driving screws with a drill, what does the drill do? Rotate or yaw?
Newton's third law of motion....
My regards,
Widewing
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Hitech,
I do have an engineering degree in aeronautics. I soloed in 3.5 hrs too in a airplane and also in a helicopter I recieved my RotorCraft rating at 40 hrs. I started flying when I was 14 I wasnt legal when I was soloed but when your dads own the airport with no feds around I didnt care. I had 376 hrs by the time I recieved my private pilot certificate this was because of my age, at the same time I took my Instrument and Commercial licences at 17. My CFI at 19 and ATP at 21.
You ask one time who my flight instructors where My first instructor was my dad a retired two star general USAF with 105 missions over north vietnam in the F-105D ThunderChief. Every aircraft he flew in the air force, he was an instructor in. He flew T-6, P-51,T-33, F-86, F-84, F-100, F-105, F-111 and F-16, my next flight instructor was mys dads partner in the airport he was a retired Col USAF he had 100 missions over vietnam he flew the F-4 Phantom II. I have also had about 20 different flight instructors between the military and civialian flying for different ratings and type training.
If you were wondering were the airport was it was KRKR Robert S. Kerr airport in Poteau OK about 30 miles south west of Ft.Smith Arkansas, we moved there from Las Vegas when my dad retired from Nellis.
I been flying for 30 yrs, I probabley have more logged instructor time then most pilots have total time. I have over 7,000 hrs rotor time alone 1/3 of that as an instructor. The only ratings I dont have is float plane, glider, tiltrotor, hot air baloon, but there next when I get time.
So I think I may know something about aerodynamics not just in theory but in practical military and commercial flying, but talking in general about a subject matter I shouldnt have done, I should be more on the point. My wife says I talk over peoples heads because Im so technical when I talk, so I try not to do that anymore.
I also fly RC helicopters and airplanes and computer sims PC and military and FAA approve class sims.
I cant think that you use ailerons to counter torgue in your RV-8 on takeoff or in any other flight manuever. I have RV-8 time too I just use rudder.
HoHun,
Sorry I didnt want to talk over you head.
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Ill tell ya what straiga how about you stop draging other things in to the basic question at hand, and try to describe how a rudder counteracts torque. Wrather than just continuing to state that it does. Because the more you say on the subject, things like
I cant think that you use ailerons to counter torgue in your RV-8 on takeoff or in any other flight manuever. I have RV-8 time too I just use rudder
makes me think you can't seperate the forces in your mind. Because you do NOT use rudder to counter engine torque. When the plane is on the ground the wheels do a fine and dandy job of opposing engine torque.
The yaw forces at take off are NOT produced by engine torque. Engine torque produces a roll , and what plane control is best for makeing a plane roll.
HiTech
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WhooHoo!
sign me up for the Free Office Tour!
I have $20.00 (although Canadian) burning a hole in me pocket!
As for the rest of the discussion, us real Peelots buzz around in Helicopters
RTR
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Straiga,
The speed difference between wingtips in the WWII fighters is not really a factor . As an example the Spitfire I (real plane in the real world test by RAE) could do continous 2,65g level turn (angle of bank 68deg) with 696ft turning radius. Due to angle of bank the speed difference between wing tips is very very small if compared to rolling moment due to turning. Basicly if we assume correct piloting technique ie the rudder is just used to keep "the ball in the middle", then "overbanking" (or what ever) can't happen in the laterally neutral or positively stable WWII fighter (that covers probably more than 90%of them) . In practice I have seen this phenomena (in sailplanes) only in very slow speed turns which are in yaw due to wrong piloting technique (too much rudder).
gripen
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Hi Straiga,
>Sorry I didnt want to talk over you head.
Don't worry, my head might be a bit low but I can still follow fine.
I'm sure this is not over your head, but you seem to have missed it anyhow: The Spitfire manual puts a limitation on the boost to be used for the constant speed propeller to function in the way you described, while you maintained a constant speed propeller would be able to regulate speed under all circumstances.
A bit more attention to detail, both with regard to technology and with regard to the posts you're referring to, and you will do great on this forum.
Regards,
Henning (HoHun)
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Because here seems to be a lot people with RC background then a good way to demonstrate engine tourque is to hover plane and make it to roll using tourque. During hovering the only way to counter tourque is ailerons.
gripen
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Sorry if this shows my ignorance........... but if torque forces are applied forward of the centre of lift/centre of gravity would this not produce some yaw?
Particularly if one of the wheels became the off centre axis around which the forces were balanced.
A force vector diagram would show this.
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HT, you're trying to explain something to the same guy who can't tell the difference between an EPR gage and a torque gage. Keep that in mind; we don't want you blowing a gasket from frustration. :D
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Flakbait [Delta6]
Delta Six's Flight School (http://www.wa-net.com/~delta6)
Put the P-61B in Aces High
(http://www.wa-net.com/~delta6/sig/stupid_ppl.gif)
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Pyro,
Go to this web sight and learn something about how the real airplanes fly. Watch this film on the characteristics of the P-51. This is an actual training film for the pilots.
This is part of the real P-51s pre-takeoff check list
< Elevator trim set to 2 degrees nose hvy
< Rudder Trim set to 7 degrees nose right
< Aileron trim set to 0 degrees
1. Listen to what the pilots say about the normal use of rudder on takeoff to counter torgue but nothing about airleron which the trim is set to 0.
2. Hitech listen to what the pilot says about prop over speed.
3. Not one time during this hole flight does he say anything about triming the airplane about the roll axis but only in a high speed dive this is because of the +1 degree on incidence on the right wing and trim he said is very little.
I have argued this point about torgue but nobody would believe me, I do know what Im talking about. I can give you technical discription of how torgue effects an airplane so you can understand it better.
After viewing this film can someone correct the aerodynamics modeling in AH 1
Heres the web sight http://www.zenoswarbirdvideos.com
And watch the Characteristics of the P-51
Later
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Gasket blowing time.
have argued this point about torgue but nobody would believe me, I do know what Im talking about. I can give you technical discription of how torgue effects an airplane so you can understand it better
Please enlighten us clueless dolts. We might even belive you if you make a valid argument.
HiTech
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Here we have a p-51 sitting on the runway with the engine running at idle power. Now advance power smoothly and evenly and we use directional control (rudder) to maintain center line.
Torgue ,p-factor, prop slip stream, and gyro procession are all the left turning translating tendencies on the ground. This is the definition from the book of advanced naval aerodynamics.
Torgue trys to roll the airplane on the ground in a tail dragger, but whats happens is that the left main landing gear is the pivot point for the roll moment or leverage. The left gear is compressed somewhat because of the roll force applied this depends on the amount of torgue present, this then translates into a left turning tendency because of the friction or drag from the left landing gear. If there was not enough rudder force to counter this left turn force the airplane will ground loop.
Hitech call those guys that gave a P-51 flight. I know they didnt let you takeoff or land due to insurance purposes and I know you dont have an LOA, but have one of those pilots discribe to you in detail a takeoff in the P-51 and show them this video and see how accurate it is. Ask them all the questions you want, ask them why they use rudder on takeoff and in the air to counter torgue, you dont have to listen to me. In fact im getting tired, I gave you prove of a training film that talks about using rudder for takeoff but I guess this goes against your religion sorry.
Let them fly AH 1 and let them tell you how incorrect, you use aileron trim. For some reason I dowt you will contact anybody, I would if I wanted to find the truth if someone was saying something else than what I beleived.
Torgue is a rolling moment in the air, on the ground it is a left turning moment. Both in the air and on the ground this force can be overcome by the use of rudder at graduall power changes. If rudder is at full deflection because of excessive torgue the plane will yaw and roll due to excessive sideslip. As pilots we fly the airplane we dont let the plane fly us so we manage the forces applied to the airplane.
Well got to go fly later
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Gripen,
How do the ailerons work when a plane is in a 0 airspeed hover when there is no airflow over the wing there worthless, it like a parked airplane move the ailerons they dont do anything, same as with rudder and elevator nothing, try rudder or elevator for some control they sit in the prop stream they have an airflow going over it. But if it exceeds rudder authority the plane will roll opposite torgue with no control authority. See you can start a roll with rudder. I used to fly RCs with no aileron just elevator and rudder with a little dyhedryl.
But this is not what were talking about, forward airflow acting on an airplane will be a yawing /rolling moment if rudder authority is exceeded due to excessive sideslip.
If you were to just use aileron to oppose excessive torgue with out rudder you would roll right aileron in and the left wing would create more lift and drag, then the right wing and the ball would be to the inside of the turn. If you did use rudder it would be right rudder to cordinate preventing sideslip. But were not using rudder at all at this time. So were not cordinated, if you were to use more aileron in this situation it would get worse in the sideslip.
The nose of the airplane at this time has been moving to the left with a left wing high slowing down because of lift and drag and the right wing speeding up because of less lift and less drag turning the nose of the airplane to the left in a yawing or left turning motion because of sideslip, and because of torgue moment in front of the CG and because of no directional control (Rudder).
Now if torgue exceeds the full aileron deflection or control authority you are already in a yawing motion, and also at a high bank angle at a given time, and airspeed is probably decaying, torgue is exceeding aileron control and it will start to roll the airplane opposite to the rotation of the prop. Now you have probably stalled one wing because of excessive sideslip. When this happens you will get into a rolling motion, and the plane would roll over on its back and get way out of control. Controlling the airplane at this time would be to stop developing torgue, (reduce power) so you can have aerodynamic authority again.
Pilots dont let there airplane get out of control like this, if they cant help it.
A pilot during a managable power increase or power decrease would just use rudder to cordinate the ball, and aileron would not have even be been needed.
Remember when you use aileron you have to use rudder in the same direction to be cordinated. This is directional control.
If there is a power change and rudder can cordinate the ball, you should not even feel a roll moment.
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Never mind, getting tired of the subject changing. Because in that whole disertation you have said.
1. Eng torque produces a roll moment.
2. Correcting with ailaron produces adverse yaw .
3. Advserse yaw is controled by rudder.
HiTech
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Im sorry Hitech, in the last string I was trying to talk gripen, to give him my view about what he was talking about.
People told me it would be a lost cause, I have talked to other pilots who fly for a living and do play AH which I have met them on a regular basis when I have flown in and seen them during work and we will sit at lunch or just hang out or something and talk about AH. Truthfully we laugh alot of the time about a lot of things that happen in AH. I have been told from these guys that they have been flying for years and that things will never change. I was told there making there money and what do they care. In there view. I try not to believe this. But we play, because of the friendship and to kill time when Im at work.
I have been sending all the E-mails to my dad to get his take on this and ask If he wanted to address this subject he said he was retired and didnt have time for games.
Im just trying to have a discussion about something and being open mined about this and see if there is something I can learn from it. By talking about it, it makes you think and you can learn from it. The last string was mostly taken out of the book. If Im wrong im wrong and I would stand up and say Im wrong, Id rather be open minded then close minded.
It would be better to demonstrate hands on and actually see the outcome, better then typing over the internet and trying to visualize what would happen or have some one else like a professional mustang pilot can explain it better.
Hey did you ever talk to someone about this? Something tells me you didnt.
Hey you know, you havent explained in your own words what you think what happens, may be I can learn something. Please tell me indetail. I have no Idea what you think, let me know were your coming from. Explain.
Why are you trying to be defensive or negative. I havent been, its feals like Im treading on your territory. You must be reading an inflection coming from my script. Thats far from it. Just trying to have a discussion. Sorry!
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Straiga,
The hovering capable RC-planes have large ailerons which start directly from the fuselage and the ailerons are usually wider near fuselage to have better controll using propeller slipstream. Basicly you are continoysly mixing together tourque effects and slipstream effects.
gripen
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Gripen, Not RC airplanes I fly. I have two yellow aircraft one F-16 and F-14 both with rossi .91s the f-14 having two, a byron P-51 and a scratch built spit 14 with a five bladed prop running a quadra 3.5 same as the p-51.
Torgue, P-Factor, prop-slipstream, gyro-precession are all left turning tendancies on the ground. Thats right out of the book for advanced aerodynamics for naval aviation. So you use rudder to counter left turning tendancies. Right!
Torgue in the air is a roll moment but the way a plane is designed to fly, it can be countered by rudder havent you ever rolled your RC with rudder only I have, so what makes you think rudder cant prevented torgue rolls? If you use aileron you still have to use rudder to cordinate the plane due to sideslip. Using aileron is a waisted flight controll against torgue, when all you need is rudder when torgue is applied. When an airplane is in striaght and level unexccelerated flight ailerons shoulnd be neutral. Rudder and elevator is a different story. Where do you set your aileron trim on your RCs?
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Straiga,
Well, none of the planes you mentioned is so called 3D capable (ie capable to maintain controll during hovering). As an example Shock Flyer (http://www.ansaproducts.co.uk/products.php?cat=12) is a good example of current 3D RC-plane generation.
The tourque caused by propeller mass and engine moving parts mass causes just rolling moment. The tourque caused by air particles hitting propeller blades causes just rolling moment (which depends on speed and angle of the propeller blade and the plane itself). After that slipstream might cause rolling and yawing moments due to assymmetrical shape of the plane or ground effect (or due to various other reasons; like thrust line and so on).
Seems that you can't see the difference between tourque and sliptream effects.
gripen
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Originally posted by hitech
...can go both wayes, because I can assue that I have done 4 g accelerated stalls in real dog fights and had the plane snap both ways, including in a p51...
when I grow up I wanna be Hitech :D. But with better typing skills :P
Straiga: I don't doubt you might have flown a lot of RC or real planes, and that you think you know a lot about aircraft...but,really, you should FORGET all you think you "know" because, to put it sharply, you're wrong in most of the topics you've raised here.
I would point out where are you wrong on most of them...but it seems it ain't neccesary...just clear your mind about everything you think you 'know' and read what hitech, Hohun and others have written in this thread. And then ask yourself if it makes sense or not...and if it does, then ask yourself if what YOU say makes sense or not.
It's quite a challenging exercise (I know, have had to go through that before and it's hard just to admit you 'may' not know as much as you think, not to talk about admitting that others have been right all the time), but in the end you'll get all your questions answered. And that is what matters.
BTW, accept this advice...don't try to teach Pyro or hitech about aircraft...and certainly don't tell them to read webpages about how do aircraft fly. Because bassically, I think they went past that stage some decades ago :D :D :D
P.D. Amazing thread, very informative. There should be a link in the main page with the best and most informative messages written in the forums about the mechanics of flying. Should help people a lot to better understand what's flying about.
and I'm serious, I think it's worth a thought :)
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I'd do some digging in each forum for a list like that if Skuzzy'd sticky it RRAM.
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Gripen,
The blade torgue is found to be proportional to a nodimensional torgue coefficient, the air density, the disk area, the square of the tip speed, and the blade radius. The torgue coefficient is dependent upon the average profile drag coefficient of the blades, the blades pitch angle, and the average lift coefficient of the blades. The torgue can be thought to result from components of profile and induced drag forces acting on the blades.
Slip stream is a by product of the average profile and induced drag of the blades, proportional to the blade area, blade radius, air density and the square of the tip speed. The resultent acceleration of the volume of air along the fuselage in a flow rotation at the vertical tail.
Of course I know the difference. You cant have one with out the other thats why they blend together. The one big disadvantage you have in not understanding the force acting on an airplane is not being able to be at the controls to see and feal the effects of the forces acting on the airframe and what controll actions needed for a given flight maneuver. Just reading and not applying what you learn about aerdynamics is a disadvantage.
Go rent a airplane get behind the controls and talk to a instructors about what you believe and see what they say. You dont have to believe me, but find out from another experienced sorce and see what they say.
I have been flying for 30 yrs now and I would not say something that I dont know about. Im not lying to you about this, this is what happens. Dont just read from a book go experience it your self. RCs dont count your not in the driver seat.
Dont get hook while your flying, its expensive for a pilots certificate.
Have a good flight!
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RRAM,
Its what is taught to stundents pilot obtaining a pilot certificate and what I had to discuss as parts of my check ride for becaming a newly FAA designator examiner and check pilot for the company I fly for, now I give the check rides for the company pilots to pass a 135, 121 and ATP check rides.
Tell us all of the extent of your flying experiences please, so we have a bases for your knowledge, and be more direct on the things that Im wrong on. So I can give you an appropriate responce.
Later!
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Originally posted by Straiga
RRAM,
Its what is taught to stundents pilot obtaining a pilot certificate and what I had to discuss as parts of my check ride for becaming a newly FAA designator examiner and check pilot for the company I fly for, now I give the check rides for the company pilots to pass a 135, 121 and ATP check rides.
Interesting. However it's also interesting that you can't explain correctly which forces are involved in a piston engined plane's takeoff, and how to counter them (at least, how and why to correctly counter them).
Tell us all of the extent of your flying experiences please, so we have a bases for your knowledge, and be more direct on the things that Im wrong on. So I can give you an appropriate responce.
Later!
Oh, my flight log doesn't go further than 5 or so hours, with 4 takeoffs and landings aboard an idiot-proof plane. And no, I ain't got a pilot licence. It isn't cheap (at least not where I live) and for now I can't pay for one. Each time I've flown I've done it with an instructor or pilot on my side, and as a personal favor...but I'm going to solve it after I get my studies completed and as soon as I can pay for the classes and licence.
However, I've spent thousands of hours reading about phisics (mostly because I studied Phisic science in the past), planes (mostly WWII-vintage), planes manuals, hundreds of web pages, and literally thousands of quite comprehensive threads on the internet about flying, why does a plane fly, how does a plane work, etc etc etc.
To know about a topic you don't necessarily need to be actively involved in the professional activity related to that topic. You just need to know. And admittedly, I know just a fraction of a fraction of a fraction of what someone as Hitech (someone with some hours of flight in P51s in his log, and aerial mock dogfights, something I guess you don't have) knows. But that's enough to know that what he has said in this thread is quite right. And enought to know that quite a lot of what you said isn't.
BTW, I can re-read the thread and find out each of your errors to make a list here, but I guess there isn't the need to do it. Others have already pointed out those errors...and they explained,too, WHY you were wrong. I can explain that myself but why to do if it's already done?. Even more because I have serious trouble explaining technical stuff in english because, as you might have noticed, my english, while good enough to read and understand almost 99% of what it comes in front of my eyes, is not good when it's time to write or speak, much less when it involves technical expressions I may have problems to translate from my native language.
So to lose time to do some copy&paste of what other, or others, have already told you won't solve a thing. As I said before, re-read the whole thread, read what others know, and have told you, while "forgetting" what you know...and then find out if it makes more sense that what you say.
It's as simple as that :)
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Straiga,
It does not matter what kind of experience you or me have with airplanes; we can't change laws of physics. The torque from the propeller does just rolling moment. It's a very common error to mix the yawing moments caused by slipstream and/or asymmetrical shape of the plane to the torque effects.
The Bf 109 is a good example how different forces affect in the take off. In the beginning of the take off it had a very strong tendency to turn right. This was caused by slipstream of the clock wise turning propeller (if viewed from the cockpit); slipstream causes more force to the left side of the fuselage forcing plane to turn right.
After speed had increased in the take off and tail was raised, it had a tendency to turn left. This was caused by tourque; more moment to the left wheel. Naturally at this moment the rudder could be used to keep direction.
Once the plane came airborne it had a strong tendency to drop left wing due to tourque, if it was pulled to the air at too slow speed even the full deflection of the ailerons (to the right) was not enough to prevent rolling motion to left..
gripen
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RRAM,
Unlike Hitech I do have an LOA in the P-51 thats means I have a license unlike hitech to fly solo in a P-51 and to carry one passanger. With over 500s logged time inthe mustang.
Im sure Hitech experience in a p-51 was taken off and landed by the pilot in the plane with him due to insurance restraints. If you comparing my flight experience to Hitechs, LOL, I stop logging flight time after about 14,000 hrs. I think I have over 23,000 hrs actually. I probably have more flight instruction time than Hitechs total flying time. As an ex-military and commercial airline pilot I think if after I log off I going to laugh my head off about this.
Oh and get about another couple thousands hours of reading and youll have about .1 percent of the total knowledge that I have forgotten, and 0 percent of actual experience. Good luck with the third grade. Get the point!
Hey Hohun,
I know you want get this right but If the prop slip stream hits the left side of the vertical stabilizer from the clock wise rotation of the prop, the nose will turn to the left needing right rudder to correct. Thats Physics.
And tourgue is spelled (torgue).
I usually get paid for this.
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Originally posted by Straiga
Get the point!
what I get is that you can't even describe in a correct way the forces involved in a piston engined plane's take off. Thus, I seriously doubt what you say you are.
in any case what I'm sure is that you're underrating what I may know. Heh, I'm not sure if you will get this example, but to know how to build houses you don't need to be an architect. To actually build a house you need to...but to know how to do it, not.
You just need to know how to do it. How to do it without being an architect?...well, you could very well understand how to do it by reading the reasons why houses are built the way they are, the phisics involved, the materials chosen and why, etc. A perfect way to reach that is to read books about the topic, and talking to architects and engineers, for instance.
In a similar way: to understand why a plane flies, and how it acts and reacts while it's flying you don't need to be a pilot, nor a mechanic, nor an engineer. You can understand almost everything of it by understanding the phisics involved (and I used to study just that at the university, you know. and BTW, I passed my 3rd grade a long way in the past. I'm currently studying my 2nd career), and reading about aeronautical engineering (which I have done extensively), or discussing matters with actual pilots and engineers (which I ALSO have done, also extensively).
and reading your "facts" posted in this thread, bassically I think you're not what you claim to be. And if you are (of course I may be completely wrong), then I won't want to fly in the back seat of your P51 when you are taking off ;).
in any case, everything I've read, everything I've talked about with professionals of flight, etc, tells me that the one who's giving the correct info in this thread is hitech, gripen, Hohun, or Pyro (his example of the driving screws as an analogy is quite good, BTW).
I just entered this thread simply to give you an advice, so you could open your ears to what others were telling you instead of sticking to your own point of view, not to discuss who has the most hours logged in a P51. Now do as you want to; I'm not giving valuable info to the main topic of this thread, so I'll leave you alone so you can go on pointing (I assume will be that way) wrong facts so hitech or others can correct them. Reading the thread, later, I may learn a bit more from those who I really believe that actually know what they are talking about :).
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Give me a fax number and I well fax you my certificates. As soon as I can copy my certificates I will fax them to you.
If hitech and pyro were to build a real airplane you can be the test pilot orval. But its your funeral.
See I told you that computer pilots make the worst airplane students, what they know you have to download, its the wrong info its like trash in and trash out, teach them the right information because the plane teaches the pilot the right way to fly not the written way. You need a 609 check ride dude.
Heres one that you cant figure out, if you take a DHC-6-300 Twin Otter and if you have an extream amount of ICE on the tail plain and stalled the tail plane, what should you do to recover from the stall.
1. Push forward on the controll yoke
2. Pull back on the control yoke
3. Use left rudder
4. Use left rudder and aileron
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Originally posted by Straiga
And tourgue is spelled (torgue).
I usually get paid for this.
what ?
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Straiga,
I quess you mean me instead Hohun?
In the case ofthe Bf 109 there is not much slipstream effect to the vertical tail due to asymmetrical shape of the tail.
And while english is not my native language, it's tourque not tourgue AFAIK.
gripen
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Originally posted by gripen
And while english is not my native language, it's tourque not tourgue AFAIK.
gripen
English is not my native language either, but i think the word you two are so desperately to spell right is "torque".
Gripen, the helical propwash and precession in takeoff of 109 (and most planes) work in the same direction, in this case left, see
http://www.jiop.fi/ksimuseo/faq_mtkierto.html#engl
http://www.djaerotech.com/dj_askjd/dj_questions/propeffects.html
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TimRas,
You can easily verify from the Kokko's report that when the Bf 109 was operated from the hard surface (as in the case of the winter time Malmi), there was no large yawing moments after tail was raised. (in the beginning, before tail was raised, there was a strong tendency to turn right as noted above). If the surface was soft then there was a tendency to turn left after tail was raised (as noted above) and this was caused by tourque (asymmetrical loading to wheels in the soft surface). The vertical tail of the Bf 109 had built in compensation for propeller slipstream effect.
gripen
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Originally posted by RRAM
P.D. Amazing thread, very informative. There should be a link in the main page with the best and most informative messages written in the forums about the mechanics of flying. Should help people a lot to better understand what's flying about.
and I'm serious, I think it's worth a thought :) [/B]
Ask and yee shall recieve! I should have most of the info contained in this thread along with a slew of other stuff posted on my site by Friday. An Engineering section is something I've always wanted to add, but with a lack of interest I didn't see much point in it. On a side note, I should also have a few more AC added to Ground School (like 6 or so). Keep an eyeball on the Help forum over the next few days, cause that's where I'll post a note when it's up.
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Flakbait [Delta6]
Delta Six's Flight School (http://www.wa-net.com/~delta6)
Put the P-61B in Aces High
(http://www.wa-net.com/~delta6/sig/geek.gif)
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Gripen,
When the plane, pitches forward and to lift the tail your bringing in gyroscopic precession at that point. A force applied in that direction meanning nose pitch down, the resultant force acks 90 degrees later which is to the left. Every prop plane I have flown, had the vertical stabilizer set to counter prop slip stream but this is more for cruise not as much on takeoff, right rudder is still used also.
Torgue is spelled torgue not tourgue.
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Torgue is spelled torgue not tourgue.
You need to invest in a dictionary.
The word is torque with q not a g.
Main Entry: torque
Function: transitive verb
Inflected Form(s): torqued; torqu·ing
: to impart torque to : cause to twist (as about an axis)
- torqu·er noun
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tonque broplem
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Straiga,
In the case of the Bf 109 most slipstream effects could be avoided by keeping tail down until the tail started to "bite". Note that when the tail was down, it had no or very little leverage (depending on surface) to move right in slipstream (to cause left side yawing moment) . Basicly TimRas's first links tells us what happened when tail was raised too early before tail started to counter yawing.
FAF test pilot Pekka Kokko made quite comprehensive tests on the Bf 109G-2 and found out that by using correct take off technique, yawing effects (caused by slipstream) were minimal when the throttle was advanced slowly in the beginning of the take off (to avoid right side yawing when the tail was down) and the tail was keeped down until tail started to work (to avoid left side yawing when the tail was up). In fact I'm quoting pretty much directly his text.
And you should read carefully TimRas another link because it explains to(u)rque ;) pretty well; moment to the other wheel in take off and also use of ailerons to counter torque in air. Kokko's report also tells us how the the Bf 109 dropped left wing (due to torque) if the plane was pulled to air at too slow speed.
gripen
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Originally posted by flakbait
Ask and yee shall recieve! I should have most of the info contained in this thread along with a slew of other stuff posted on my site by Friday. An Engineering section is something I've always wanted to add, but with a lack of interest I didn't see much point in it. On a side note, I should also have a few more AC added to Ground School (like 6 or so). Keep an eyeball on the Help forum over the next few days, cause that's where I'll post a note when it's up.
WTG, Flakbait :)
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I wondered a bit this torque/tourque spelling thing because I have seen both in the books. It appears that the brits spell tourque and the americans torque.
So not! (as legendary Matti Nykänen use to say)
gripen