Aces High Bulletin Board
General Forums => Wishlist => Topic started by: catdaddy on December 18, 2009, 09:49:38 AM
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ALL WW II acft had trim tabs, there was not one single WW II acft that was equipped with with an all flying tail (entire horizontal stabilizer moves to trim acft) and the ONLY fighter equipped with boosted controls (ailerons ONLY) was the P-38 J and subsequent lightnings. As the onset of the sonic shock wave becomes apparent the control forces increase enormously. Another WW II design limitation was the cable and pulley control system incorporated into all the WW II acft, there was not a mechanical advantage designed into any of the control systems that I have seen to date.
The point I'm trying to illustrate is this; Trim tabs could not conceivably overcome the several tons of force required to move a fabric covered control surface on ANY acft experiencing the effects of the sonic wave build up (compression) at high speed.
In some cases the aircraft the compression effects are more pronounced at lower speed due to the wing planform and/or the control surface area, a good example is the A6M series, lightly built, large ailerons, thicker planform. These features allowed zeros to perform very well at low to medium speeds 250 mph and lower, above 250 mph testing revealed the inability to roll to the right and a limited ability to roll left assisted only via engine torque (only at 1/2 throttle and above). Many zeros were shot down by taking advantage of this controls issue.
ME-109s compressed earlier than P-47's or P51's and U.S. pilots took advantage of that as well, TRIM did not affect the onset of compression nor did it add any amount of effective control input during the effects of compression. In nearly all cases the trim tabs were MANUALLY adjusted via trim wheels in the cockpit. MY wish....( insert drum roll here) ...is for the trim to be diminished at higher speed and eliminated during the effects of compression. keep it real
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ALL
Not a good start to a thread... :bolt:
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The 109 did not suffer from compression. Quite the opposite; it suffered from heavy controls. Many seem oblivious to the fact that compression and control stiffness are entirely different phenomena. The former is caused when there is not enough airflow over the control surfaces, i.e. horizontal stabilizer. The latter is caused by too much airflow over the control surfaces.
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The 109 did not suffer from compression. Quite the opposite; it suffered from heavy controls. Many seem oblivious to the fact that compression and control stiffness are entirely different phenomena. The former is caused when there is not enough airflow over the control surfaces, i.e. horizontal stabilizer. The latter is caused by too much airflow over the control surfaces.
You'd think they would have thought of powered steering.
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EDIT: Nevermind. I just don't care.
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Inconceivable as it may seem, pilots actually did use trim to counter compressibility.
If you want to criticize the flight model it's better to cite references so people don't think you just made stuff up.
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Inconceivable as it may seem, pilots actually did use trim to counter compressibility.
I doubt that, otherwise the P-38 series would not have had dive flaps introduced. I think you mean that trim could be used to counter control stiffness so that the aircraft would pitch up on its own.
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This time wikipedia is very helpful:
Compressibility is an important factor in aerodynamics. At low speeds, the compressibility of air is not significant in relation to aircraft design, but as the airflow nears and exceeds the speed of sound, a host of new aerodynamic effects become important in the design of aircraft. These effects, often several of them at a time, made it very difficult for World War II era aircraft to reach speeds much beyond 800 km/h (500 mph).
Some of the minor effects include changes to the airflow that lead to problems in control. For instance, the P-38 Lightning with its thick high-lift wing had a particular problem in high-speed dives that led to a nose-down condition. Pilots would enter dives, and then find that they could no longer control the plane, which continued to nose over until it crashed. Adding a "dive flap" beneath the wing altered the center of pressure distribution so that the wing would not lose its lift. This fixed the problem.[4]
A similar problem affected some models of the Supermarine Spitfire. At high speeds the ailerons could apply more torque than the Spitfire's thin wings could handle, and the entire wing would twist in the opposite direction. This meant that the plane would roll in the direction opposite to that which the pilot intended, and led to a number of accidents. Earlier models weren't fast enough for this to be a problem, and so it wasn't noticed until later model Spitfires like the Mk.IX started to appear. This was mitigated by adding considerable torsional rigidity to the wings, and was wholly cured when the Mk.XIV was introduced.
The Messerschmitt Bf 109 and Mitsubishi Zero had the exact opposite problem in which the controls became ineffective. At higher speeds the pilot simply couldn't move the controls because there was too much airflow over the control surfaces. The planes would become difficult to maneuver, and at high enough speeds aircraft without this problem could out-turn them.
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I doubt that, otherwise the P-38 series would not have had dive flaps introduced. I think you mean that trim could be used to counter control stiffness so that the aircraft would pitch up on its own.
Nonsense.
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ME-109s compressed earlier than P-47's or P51's and U.S. pilots took advantage of that as well, TRIM did not affect the onset of compression nor did it add any amount of effective control input during the effects of compression. In nearly all cases the trim tabs were MANUALLY adjusted via trim wheels in the cockpit. MY wish....( insert drum roll here) ...is for the trim to be diminished at higher speed and eliminated during the effects of compression. keep it real
Ummm... what makes you think this doesn't happen now? I remember a patch a couple of years ago that addressed this very issue. The 109 could squeak out of a compression dive by using trim - actually any aircraft could PRIOR to the patch. Now, trim barely moves the aircraft. Trust me, it was a lot more obvious than before - for me.
I do have a trick (I fly the Bf-109F4/G2 + Ki-84) - I trim all the way up and then engage combat trim. When I'm dog fighting and I need the extra pull - I disengage combat trim and it pulls my nose up that much harder. During compression however, I cannot trim out of a dive. Ever.
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Nonsense.
Is that all you got?
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EDIT: Nevermind. I just don't care.
:rofl
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The 109 did not suffer from compression. Quite the opposite; it suffered from heavy controls. Many seem oblivious to the fact that compression and control stiffness are entirely different phenomena. The former is caused when there is not enough airflow over the control surfaces, i.e. horizontal stabilizer. The latter is caused by too much airflow over the control surfaces.
Since you asked, this is also nonsense.
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You still haven't made a substantive point in favor of your opinion. All you're saying is "no."
Argument by appeal to no argument at all is way too popular at the AH forum.
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ALL WW II acft had trim tabs, there was not one single WW II acft that was equipped with with an all flying tail (entire horizontal stabilizer moves to trim acft)
The 109's whole stabilizer moved for trim. As did the 190's. Only a trivial amount of research would have been needed to discover this before posting.
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Actually the 109 had trim tabs on the horizontal stab that had to be adjusted on the ground. Can't remember exactly how the 190 trim worked.
Anyone know what the OP is going on about anyway? Trim settings work pretty well in the game.
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ALL WW II acft had trim tabs,
I think that many/most WWII aircraft had no inflight adjustable trim at all, though I may be mistaken.
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The point I'm trying to illustrate is this; Trim tabs could not conceivably overcome the several tons of force required to move a fabric covered control surface on ANY acft experiencing the effects of the sonic wave build up (compression) at high speed.
In some cases the aircraft the compression effects are more pronounced at lower speed due to the wing planform and/or the control surface area, a good example is the A6M series, lightly built, large ailerons, thicker planform. These features allowed zeros to perform very well at low to medium speeds 250 mph and lower, above 250 mph testing revealed the inability to roll to the right and a limited ability to roll left assisted only via engine torque (only at 1/2 throttle and above). Many zeros were shot down by taking advantage of this controls issue.
ME-109s compressed earlier than P-47's or P51's and U.S. pilots took advantage of that as well, TRIM did not affect the onset of compression nor did it add any amount of effective control input during the effects of compression. In nearly all cases the trim tabs were MANUALLY adjusted via trim wheels in the cockpit. MY wish....( insert drum roll here) ...is for the trim to be diminished at higher speed and eliminated during the effects of compression. keep it real
A) The 109 series did not suffer from compression, rather from control stiffness at high speeds. These are two different things.
B) 'Trimming' out of a dive was use by 109 pilots in real life. So if you'd like to 'keep it real'... ;)
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I think that many/most WWII aircraft had no inflight adjustable trim at all, though I may be mistaken.
Motherland...uhhhh...that's in direct contradiction to your statement about the 109 pilots trimming out of a dive...how could they do that if there was no "inflight adjustable trim"?
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A) The 109 series did not suffer from compression, rather from control stiffness at high speeds. These are two different things.
A lot of people seem to confuse control stiffness due to high speeds and compression/compressability. Most players in game experience control stiffness at high speeds rather compressability. Of course, obvious exceptions are planes like the P-38 and P-47 that did suffer from compressability in high speed dives depending at the start altitude of the dive.
ack-ack
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Actually the 109 had trim tabs on the horizontal stab that had to be adjusted on the ground. Can't remember exactly how the 190 trim worked.
Anyone know what the OP is going on about anyway? Trim settings work pretty well in the game.
The 109 had elevator and aileron trim controls in the cockpit, two wheels located to the left of the pilots seat. What it was lacking was rudder trim if I recall correctly.
In Alfred Price's book on the 190 he has the following to say on the 190 trim system.
A fighter pilot did not want to have to re-trim the aircraft each time he moved the throttle. The team were so successful in this that they found that movable trim tabs were unnecessary. Small fixed trimming tabs were fitted to the ailerons, the elevators, and the rudder. They were adjusted on the ground after the initial flight, to compensate for the wide tolerances that occur with a mass produced aircraft. The only system of trimming the aircraft in flight was in the elevator sense, and that was achieved using an all moving tailplane.
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Motherland...uhhhh...that's in direct contradiction to your statement about the 109 pilots trimming out of a dive...how could they do that if there was no "inflight adjustable trim"?
Even the majority of 109 models had only two axises (pitch/roll) that could be trimmed in flight. The rudder trim had to be adjusted on the ground (on versions that had it- this was not the majority).
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That is all moot. catdaddy's mistake is to interpret all control stiffness in AH as compression when in fact very little of it is compression and is instead control stiffness due to excessive airflow over the control surfaces.
Prominent examples in AH are the Bf109's or Ki-84's difficulty pulling out of a fast dive, the Spitfire's poor roll rate at high speeds and the A6M's poor roll rate and poor elevator response at high speed. None of those are compression effects.
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A lot of people seem to confuse control stiffness due to high speeds and compression/compressability. Most players in game experience control stiffness at high speeds rather compressability. Of course, obvious exceptions are planes like the P-38 and P-47 that did suffer from compressability in high speed dives depending at the start altitude of the dive.
ack-ack
Nonsense. ;)
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Nonsense. ;)
Is that all you got? ;)
ack-ack
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Actually the 109 had trim tabs on the horizontal stab that had to be adjusted on the ground. Can't remember exactly how the 190 trim worked.
Anyone know what the OP is going on about anyway? Trim settings work pretty well in the game.
Both aircraft changed the incidence of the horizontal stab for trim in the longitudinal axis. The OP apparently did not bother to find this out when he stated that "there was not one single WW II acft that was equipped with with an all flying tail (entire horizontal stabilizer moves to trim acft)"
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Also I thought the P38L was the first model to have boosted ailerons?
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Also I thought the P38L was the first model to have boosted ailerons?
I need to confirm, but I believe that the boosted ailerons and dive flaps first appeared on the P-38J-25-LO.
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I like trim...trim is good...not real bushy trim but then...trim is trim ya know? Fast action trim can be a lot of fun...but most of the time I like the slower casual trim use...I don't turn down the chance to get trim unless the rest of the frame looks like it belongs in a dog food bag...or if the trim itself looks like it's been chewed up by a dog. I like trim in all sizes too.
I like trim...
:D :bolt:
Hopefully skuzzy doesn't give me the old "see rule #" action...
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The AAF Manual 51-127-1 on the P-38, under the section titled Compressibility Recovery Procedure, states: "Use only a few degrees of elevator trim tab". This is also listed under Normal Dive Recovery as well as being part of the procedure for recovering from compressibility in a dive.
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The AAF Manual 51-127-1 on the P-38, under the section titled Compressibility Recovery Procedure, states: "Use only a few degrees of elevator trim tab". This is also listed under Normal Dive Recovery as well as being part of the procedure for recovering from compressibility in a dive.
That was only if they were on the onset of compressability. If a P-38 was in a full compressability state, using elevator trim to come out of it wouldn't work. Otherwise there would have been no need for the dive flaps that were introduced first in the P-38J-25-L0 and later L models.
ack-ack
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I need to confirm, but I believe that the boosted ailerons and dive flaps first appeared on the P-38J-25-LO.
I believe you are correct.
ack-ack
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See Rule #4
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See Rule #4
You seem to be pretty fascinated with consoles... you mention them in almost every post :)
I start to see some good PNG potential here ;)
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That was only if they were on the onset of compressability. If a P-38 was in a full compressability state, using elevator trim to come out of it wouldn't work. Otherwise there would have been no need for the dive flaps that were introduced first in the P-38J-25-L0 and later L models.
ack-ack
It was also when recovering. According to the manual the denser lower air would slow you down enough after cutting power that your controls would become effective again. I never said trim eliminated compressibility.
In any case the trim effectiveness is already reduced in AH at compressibility.
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I stand corrected, the 109's did trim through the horizontal stab, however after reading the flight test results it mentioned the actual performance of 109's at the various speeds. At 400 mph it takes FIVE (5) seconds to roll the acft to 45 degrees bank.
Ailerons
At low speeds the aileron control is very good, there being a definite resistance to stick movement, while response is brisk. As speed is increased, the ailerons become heavier, but response remains excellent. They are at their best between 150 mph and 200 mph, one pilot describing them as an 'ideal control' over this range. Above 200 mph they start becoming unpleasantly heavy, and between 300 mph and 400 mph are termed 'solid' by the test pilots. A pilot exerting all his strength cannot apply more than one-fifth aileron at 400 mph. Measurements of stick-top force when the pilot applied about one-fifth aileron in half a second and then held the ailerons steady, together with the corresponding time to 45 degrees bank, were made at various speeds. The results at 400 mph are given below:
Max sideways force a pilot can apply conveniently to the Bf.109 stick 40 lbs.
Corresponding stick displacement 1/5th.
Time to 45-degree bank 4 seconds.
Deduced balance factor Kb2 - 0.145
Several points of interest emerge from these tests:
a. Owing to the cramped Bf.109 cockpit, a pilot can only apply about 40 lb sideway force on the stick, as against 60 lb or more possible if he had more room.
b. The designer has also penalized himself by the unusually small stick-top travel of four inches, giving a poor mechanical advantage between pilot and aileron.
c. The time to 45-degree bank of four seconds at 400 mph, which is quite excessive for a fighter, classes the airplane immediately as very unmanoeuvrable in roll at high speeds.
Elevator
This is an exceptionally good control at low air speeds, being fairly heavy and not over-sensitive. Above 250 mph, however, it becomes too heavy, so that manoeuvrability is seriously restricted. When diving at 400 mph a pilot, pulling very hard, cannot put on enough 'g' to black himself out; stick force -'g' probably exceeds 20 lb/g in the dive.
Rudder
The rudder is light, but rather sluggish at low speeds. At 200 mph the sluggishness has disappeared. Between 200 mph and 300 mph the rudder is the lightest of the three controls for movement, but at 300 mph and above, absence of a rudder trimmer is severely felt, the force to prevent sideslip at 400 mph being excessive.
Harmony
The controls are well harmonised between 150 mph and 250 mph. At lower speeds harmony is spoiled by the sluggishness of the rudder. At higher speeds elevator and ailerons are so heavy that the worn 'harmony' is inappropriate.
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You seem.......bitter.
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and again I was wrong about the 190 (sigh) German technology it was even electric trim...just really slow.
The controls are highly effective at most speeds and forces are moderate giving good control feel. However, at speeds over 400 MPH indicated airspeed, the elevator tends to become quite heavy and noticeable buffeting and vibration of the airplane occurs.
F. Trim and Stability
Longitudinal trim of the airplane is accomplished by changing the incidence angle of the stabilizer rather than by trim tabs on the elevator. Ground adjustable tabs are only provided for rudder and aileron but are adequate since rudder and aileron trim changes for most flight conditions are very slight.
The elevator trim control is electrically operated and is controlled by a toggle switch. This control arrangement operates too slowly for maneuvers, requiring a rapid change in elevator trim.
Stability was satisfactory at this weight and C.G. location.
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It was also when recovering. According to the manual the denser lower air would slow you down enough after cutting power that your controls would become effective again. I never said trim eliminated compressibility.
In any case the trim effectiveness is already reduced in AH at compressibility.
Actually, the trim was spring loaded, so when the aircraft's mach speed became slower in the denser air, it would move the elevators to enable the aircraft to pull out. If one didn't do that and just pulled back on the stick, it could suddenly unlock with the lower mach speed, with the sudden up elevator causing other issues, like blackouts and broken planes.
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See Rule #4
The intent of the dive flaps in the P-38 were never meant to 'delay the onset of compressability', but rather to help the pilot pull out of a high speed dive in which they entered compressability. The dive flaps didn't increase the mach threshold to stave off compressability. The dive flaps didn't just work to a point, they worked very well and those P-38s outfitted with the dive flaps had no troubles following German planes as they tried to dive away. Tony LeVier (Lockheed test pilot) used to do demonstrations where he would dive a P-38L at high speeds and recover easily using the dive flaps. Also, a little known thing is that before the dive flaps, some P-38 pilots had no troubles following German planes as they tried to dive away. P-38 pilots like Mosier, Olds and Lowell used to use their rudders to help slow them down in high speed dives, but they were amongst the small number of very experienced P-38 pilots in the ETO.
ack-ack
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I stand corrected, the 109's did trim through the horizontal stab, however after reading the flight test results it mentioned the actual performance of 109's at the various speeds. At 400 mph it takes FIVE (5) seconds to roll the acft to 45 degrees bank.
Ailerons
At low speeds the aileron control is very good, there being a definite resistance to stick movement, while response is brisk. As speed is increased, the ailerons become heavier, but response remains excellent. They are at their best between 150 mph and 200 mph, one pilot describing them as an 'ideal control' over this range. Above 200 mph they start becoming unpleasantly heavy, and between 300 mph and 400 mph are termed 'solid' by the test pilots. A pilot exerting all his strength cannot apply more than one-fifth aileron at 400 mph. Measurements of stick-top force when the pilot applied about one-fifth aileron in half a second and then held the ailerons steady, together with the corresponding time to 45 degrees bank, were made at various speeds. The results at 400 mph are given below:
Max sideways force a pilot can apply conveniently to the Bf.109 stick 40 lbs.
Corresponding stick displacement 1/5th.
Time to 45-degree bank 4 seconds.
Deduced balance factor Kb2 - 0.145
Several points of interest emerge from these tests:
a. Owing to the cramped Bf.109 cockpit, a pilot can only apply about 40 lb sideway force on the stick, as against 60 lb or more possible if he had more room.
b. The designer has also penalized himself by the unusually small stick-top travel of four inches, giving a poor mechanical advantage between pilot and aileron.
c. The time to 45-degree bank of four seconds at 400 mph, which is quite excessive for a fighter, classes the airplane immediately as very unmanoeuvrable in roll at high speeds.
Elevator
This is an exceptionally good control at low air speeds, being fairly heavy and not over-sensitive. Above 250 mph, however, it becomes too heavy, so that manoeuvrability is seriously restricted. When diving at 400 mph a pilot, pulling very hard, cannot put on enough 'g' to black himself out; stick force -'g' probably exceeds 20 lb/g in the dive.
Rudder
The rudder is light, but rather sluggish at low speeds. At 200 mph the sluggishness has disappeared. Between 200 mph and 300 mph the rudder is the lightest of the three controls for movement, but at 300 mph and above, absence of a rudder trimmer is severely felt, the force to prevent sideslip at 400 mph being excessive.
Harmony
The controls are well harmonised between 150 mph and 250 mph. At lower speeds harmony is spoiled by the sluggishness of the rudder. At higher speeds elevator and ailerons are so heavy that the worn 'harmony' is inappropriate.
That report is about the Bf 109E model, which had (and has in game) much worse high speed maneuverability in general to its later counterparts, in roll rate in particular. Take the Emil up in game and try to roll it at 400mph. If you're feeling extra daredevilish, try to roll it against the engine torque.
Not only that but you misquoted the roll time even in the report, which was four seconds, not 'FIVE (5)' seconds.
I just took up the Bf 109E offline, climbed to about 7k so I could actually reach 400mph in a dive, leveled at 400mph and guess what... it took about 4 seconds to roll 45% right with full stick deflection.
and again I was wrong about the 190 (sigh) German technology it was even electric trim...just really slow.
Just tested this offline as well, it takes a little under 5 seconds to go from neutral to full up on the elevator trim.
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See Rule #4
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BNZ....dang....sir, you are the man..... :salute :airplane: