Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: Kaz on August 29, 2003, 02:03:45 PM
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I know that torque effects will be increasing in AH2 for those planes that experienced it with everything functioning properly.
Basically now in AH we can jam the throttle to full power and use a bit of rudder and maybe a little aileron to stay straight until takeoff.
But I remember reading somewhere that the P-51D on takeoff used 1/3 to 1/2 throttle. Anymore throttle and the torque would be too much to counteract.
I'm guessing that this applied to more planes and not just the Mustang.
So will this aspect of power/prop related torque be modelled in AH2 to be as close to the real thing as possible?
And if so then how much would this affect the amount of runway used for takeoff?
Just some questions from a not - in - the - know WW2 flight novice.
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Originally posted by Kaz
I know that torque effects will be increasing in AH2
How do you know this? Source?
(http://image1ex.villagephotos.com/extern/640697.jpg)
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Swoop,
Pyro said that (IIRC) the P factor was impacting too far out on the wings in the current model and would be fixed in the new model.
The end effect is that the apparent "torque" would be greater.
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Ah right. Cool.
Damn I wish we had all this in a FAQ somewhere so peeps like me didn't miss it. hint hint HT.
(http://image1ex.villagephotos.com/extern/640697.jpg)
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Originally posted by Swoop
Ah right. Cool.
Damn I wish we had all this in a FAQ somewhere so peeps like me didn't miss it. hint hint HT.
(http://image1ex.villagephotos.com/extern/640697.jpg)
*snort*
I don't advise holding your breath.
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I believe they fixed this torque issue with "auto take-off" :)
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I hope HTC doesn't overdue the torque model as so many wish.
Do not forget that these A/C had trim tabs that were very effective in dealing with takeoff torque.
Also many of the A/C that are currently modeled with combat trim in AH did not have the ability to use trim in flight IRL.
For instance the Me109 and FW190 had no cockpit adjustable elavator or rudder trim in the cockpit. This makes life very easy in AH but was not the case as this capabilty did not exist.
I beleive the La-7 had the same lack of trim wheels.
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Originally posted by Karnak
Pyro said that (IIRC) the P factor was impacting too far out on the wings in the current model and would be fixed in the new model.
I don't think Pyro said that. P-factor is called P-factor because it's an effect of the prop. Wings don't have anything to do with it.
What is going to be changed are the effects of prop wash on the wings (and probably other parts of the aircraft). Those contribute almost everything to the bad behaviour of the plane. P-factor doesn't, especially at slow speeds, e.g. at take off.
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I don't think Pyro said that. P-factor is called P-factor because it's an effect of the prop. Wings don't have anything to do with it.
that is correct. In MOST, airplanes there are 4 forces that cause an airplane to turn left. #1 Torque (motor) #2 P-Factor, 1 prop blade gets more bite out of the air than the other one (most noticable in a climb) #3 Gyroscopic Precession (reacts 90* ahead of where pressure is applied) #4 Spiraling slipstream (air from the prop striking the vertical stabilizer)
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The spitfire MKXIV was another fighter that used about half throttle on takeoff to lessen torque.
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I REALLY have trouble believing that any WWII planes didn't have elevator trim wheels or handles in the cockpit. But I haven't checked this myself. The aerodynamical forces change a lot from slowflight to full speed. The strain on the pilot flying a WWII bird without elevator trim would be pretty much intolerable and unnecessary.
Is it for real F4UDOA?
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I REALLY have trouble believing that any WWII planes didn't have elevator trim wheels or handles in the cockpit
The Polikarpov I-15 and I-16 havn't got no trim wheels.
Sailor
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Originally posted by F4UDOA
For instance the Me109 and FW190 had no cockpit adjustable elavator or rudder trim in the cockpit.B]
Both of these planes definately had an adjustable elevator trim.
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Originally posted by N8DOG
that is correct. In MOST, airplanes there are 4 forces that cause an airplane to turn left. #1 Torque (motor) #2 P-Factor, 1 prop blade gets more bite out of the air than the other one (most noticable in a climb) #3 Gyroscopic Precession (reacts 90* ahead of where pressure is applied) #4 Spiraling slipstream (air from the prop striking the vertical stabilizer)
At last someone who understands flight. ;)
Except, gyroscopic precession affects any plane without a nose wheel during takeoff. So, with most of the planes in AH it kicks in (or should kick in) just as the tail wheel comes up off the ground.
And, just as a side note. Anyone using ailerons to "steer" a plane without a nose wheel is looking for disaster. These planes should be "guided" with rudder and brakes only.
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I thought the Bf-109 had no rudder trim, requiring the pilot to keep his feet on the rudders applying some pressure at all times.
Bf-109s did have elevator trim. I read that pilots would trim their 109s to be nose light so that the planes were more responsive (less mushy) in combat. This required the pilot to keep his hands on the stick to fly level, but it was a choice.
MRPLUTO VMF-323 ~Death Rattlers~ MAG-33
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Except, gyroscopic precession affects any plane without a nose wheel during takeoff. So, with most of the planes in AH it kicks in (or should kick in) just as the tail wheel comes up off the ground.
Well....actually...it's a left turning tendency in a conventional gear (tail wheel) and a right turning tendency in a tricycle gear. In the trike it happens at rotation, but because it's "documented" in the AFH with the subnote of "on conventional gear" it's always lumped in with the other lefts.
If you fly some of the Euro/Russkie planes, then torque and P-factor will also be right turning tendencies as the prop rotates in the other direction. I can't recall exactly which ones have the opposite props at the moment, but just as an example, the difference between say an Extra-300 and the SU-29.
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I see one person here who has some background in aerodynamics. If ya'll notice on auto take off the ailerons are situated in the right turn position, why???? There is no crosswind on any of these airfields. Ailerons are only in effect when there is airflow. Just as in a stall ailerons are useless until airflow is re-established.
As far as P-Factor and other forces acting upon an aircraft during takeoff, the designers of these aircraft were aware of these forces and built slight airframe designs in order to counteract these forces during takeoff without most importantly taking away the performance during flight. Most fighters during this era used 50% power until airflow was established over the wings and then full power was applied SLOWLY!!!! I know I have taken several rides in a P-51 Mustang and LA-7, for I am a real world pilot and instructor.
Flight modeling is damn good in this game and I dont believe they should make it harder for gamers to takeoff. Not many people understand flight dynamics, resulting in making the game miserable for them if they cannot take off. This should be an option for experienced gamers making the aircraft have increased performance if you know what your doing and less performance for those who choose auto takeoff AGREE???
Just my opinion.
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Originally posted by recon1
As far as P-Factor and other forces acting upon an aircraft during takeoff, the designers of these aircraft were aware of these forces and built slight airframe designs in order to counteract these forces during takeoff
pfactor cannot be compensated. it is purely dynamic, the force acting only when the angular momentum, the attitude of the aircraft changes. No aerodynamic compensation behaves like that. The only way to compensate pfactor is by a mass rotating in the opposite direction of the prop.
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P-factor,Torque, and Spiraling Slipstream on most western WW2 Aircraft had left turning tendencies as the properllor rotated to the right. In modern tricycle light aircraft they have too left turning tendencies the difference is the severity in which they're manifested.
IMO in AH they seem too light, the 109 for example had very bad habits when being at slow speed if the throttle was pushed too quickly without having too much speed or while in take -off you could ground loop. The 190 too had a masty snap roll at lo airspeeds and high angle of attack,not just due to the wing loading.
Th 109 had aileron and elevator trim(which moved the whole horizontal stab) it didn't have rudder trim. The 190 did Have elevator trim in the least it was an electrically driven servo. As far as far as rudder and aileron trim I'm not certain it had these,but anyone much more knowledgeable in the 190's systems might correct me.
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I realize p factor is purely dynamic and it is true you would need something counteracting, which is the plane itself. Newton's 3rd Law For Every Action There is an Opposite and Equal Reaction. So the prop and torque is one action and the airframe is the opposite and equal reaction. What I meant by manufacturers building airfoils into the airframe can only take affect when airflow is introduced to these airfoils. Most of these aircraft where built for power and speed, hence the over sized propellers and engines. P-51 for example, inline 12 cylinders Allison engines took up the first 8 feet of the aircraft. Wish I had that engine in my car! LOL
Anyway thats just my opinion.
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My bad. was thinking precession and writing pfactor. precession can't be compensated.
now thinking about pfactor, it probably can't be compensated either for all flying states at least, but at initial takeoff roll it's zero anyway.
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Wmaker,
My bad, I meant aileron and rudder, not elavator.
Jodgi,
What they had is adjustable trim that had to be set by hand before flight. So once you were airborne that was it.
Seems strange considering how German machinery seems so well done but their trim system was stone age.
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What in AH limites the torque effect (yes, the real one, where the aircraft rolls to the opposite direction the prop speeds up to and blows the air in, not the yawing tendency) are two things:
The gradient of engine speeds is limited in AH. If you're at full RPM and idle, then push in full throttle, first the prop should spin up to full speed, then create thrust. In AH the speed increase is limited.
The gears are very though, but don't seem to be modeled indivdually. When realoading bombs on the hot pad, the aircraft sinks in a bit due to highter mass. I've never seen it sink in on one gear only, e.g. dropping the bomb on one wing not the other.
One wheel beeing pressed to the ground more than the other also creates some yawing, but with the tough gear I don't think this is modeled.
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This is why torque is modeled how it is currently in AH.
Originally posted by Pyro in another thread
One thing that I mentioned with regards to torque is that the propellor slipstream effects on the wings were being placed too far out thus creating an artificially large force moment. This effect counteracts torque to a degree, an overly large degree in AH until now. The propwash from a propellor comes off in a vortex that corkscrews back over the airplane. In a standard clockwise rotating engine, the vortex strikes the right wing with a downward component and the left wing with an upward component. This increases the effective aoa of the left wing and decreases the effective aoa of the right wing, hence more lift on the left wing and less on the right.
The slipstream continues to corkscrew back to the tailplane where it impacts the vertical stabilizer on the left side which pushes the tail to the right and the nose to the left. This is the main force causing the left yaw on your takeoff roll.
With regards to that, the main factor countering that in AH is the modeling of the tailwheel. All the planes have a steerable tailwheel and that is a change we are looking at as well.
ack-ack
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Originally posted by F4UDOA
Wmaker,
My bad, I meant aileron and rudder, not elavator.
Jodgi,
What they had is adjustable trim that had to be set by hand before flight. So once you were airborne that was it.
Seems strange considering how German machinery seems so well done but their trim system was stone age.
The Germans thought they were unnecessary, and they were. Both the 109 and the 190 had elevator trim. The trim tabs on the ailerons and rudder were set for cruising speed. I wouldn't call the German electric trim system "stone age", considering that the allies were using manual wheels. The 109 and 190 simply didn't need aileron and rudder trim, plenty of other German planes did, and were so equipped.
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Actually, the 109 could definately have used rudder trim.
I have read to many accounts of how tired the pilot's legs would get in a fight or at high speed in the 109.
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why do u think they made the p38s props spit opposite directions so it would eliminate the tourqe problem
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why do u think they made the p38s props spit opposite directions so it would eliminate the tourqe problem
That's to eliminate the "critical engine". What I haven't been able to figure out is why they spin outside instead of inside like every other non conventional twin I've seen.
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actuallly they spin outside cause it does eliminate engine tourqe cause i watched a show on the p38 and thats what they say it did
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Originally posted by jigsaw
That's to eliminate the "critical engine". What I haven't been able to figure out is why they spin outside instead of inside like every other non conventional twin I've seen.
The XP-38 and Model 322's (RAF version) had inward turning, counter-rotating propellers. The YP-38 and all subsequent Lightnings had outward turning, counter-rotating propellers which negated the torque when both engines were operating.
ack-ack
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Thanks Ack. Never knew they had any at all the turned inward.
You're both correct about the torque by the way. I'm just tossing out some additional info. Yeh I know I tend to ramble some times, but it keeps me in practice for teaching ground. ;)
General FYI stuff for critical engine (and torque :p)....
Book definition of critical engine: engine that will have the most adverse effect on the aircraft if it fails.
In a conventional twin (props both rotate to the right from the pilots view) the left engine is the critical engine because the thrust line is closer to the centerline of the aircraft. This means that the thrust line on the right engine has a longer arm to the centerline (almost a duh thing but that's how simple we're supposed to teach it). If an engine fails, the thrustline, p-factor, and torque on the remaining engine will create a rolling moment. Right engine having a longer arm, creates a larger rolling moment.
On small trainers like the seminole and duchess (180 hp whee) it's so slight and slow that you could go out for coffee, come back, and still recover. Plus they're counterrotating inward.
You step up to the high horsepower planes and if you don't catch and correct it immediately it's gonna roll you over rather nicely. If you were to lose the right engine, you'll still have all the nasty factors acting on the aircraft, but because the arm on the left engine is closer to centerline, the effect isn't "as" great. Although, I'd be willing to bet in 38 it would still roll you over rather nicely if you didn't catch it.
What I still miss on the 38 is that turning inward or outward would have the same effect on torque. But, outward makes the thrust arm to centerline longer on *both* sides. Just curious as to why they chose outward. Would be interesting to hear the aerodynamic reasoning they had during design. Best speculation (note the speculation) I've heard so far has to do with the way the spiraling slipstream hits the the twin vertical stabs.
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Maybe the prop wash cancels part of the wake turbulence?