Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: Enduro on September 20, 2005, 01:15:48 AM
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Okay, this post isn't meant as a whine at all.
We all know that the Hog's engine was a torque monster. But, I'm wondering if the torque in our Hog is just a bit overmodelled. I'm referring to the tendency of our Hog to loop after landing with an idle throttle.
Isn't the tendency just a bit much? Maybe not. Just askin'.
:)
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Helps if you "lock" the tail wheel by pulling half back on the stick. Tricky part is timing it right, too early and it try's to fly again.
To late and your already into the first swerve that leads to the ground loop.
And no, I don't think its overmodeled. :)
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The "swing" on landing and takeoff isn't caused by tourque actually. It's caused by the slipstream from the propeller hitting the vertical stab, this is why rudder helps to counter it. All planes have it, specially when taking off as you throttle up.
Tourque is a totally different thing, usually misstaken for the slipstream. Some planes wityh big engines (possibly the best known, Skyraider) could flip all over on iot's back if the throttle was moved up too fast. The tourque is countered by ailerons which is why you can only counter it with some airspeed. The tourque is also the reason your plane is rolling if you climb straight up and lose speed.
If anything, the tourque in the F4u is undermodelled IMO.
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I do this. Come in slow, 2 notches flap, and when yoyu touch..PUSH FORWARD on the stick keeping your tail OFF the ground. The brakes will slow you down as you do this. Just when you feel you cant keep it off its tail any longer, pull back hard on the stick, slamming the tail down. You will stop before any weird crap happens.
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The F4U is so much fun to take off and land.
Especially a carrier landing with 1 missing flap, and 1 destroyed gear.
;-)
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The trick to landing all airplanes is the C and V keys. Set them to be left and right brakes.
I haven't rolled a plane in a year and a half.
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Ah, Lady slipstream, eh? Well, remember that I'm talking about an aircraft with its throttle at full idle here. Is the slipstream effect so apparent in the Hog when it's very slow & dirty?
Another question, then...why is slipstream so apparent in AH2's Hog and barely noticeable in the other a/c, like the 109, P-51 and Jug (when slow with idle throttles)?
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Is it possible to key map the tailwheel lock?
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The slipstream is just as noticable in the other planes (they wanna run of the runway on takeoff). However, part of the F4u ground looping problem may be the large tail fin.
Uhm, trying to explain tourqe to explain how it doesn't make a plane "sway" when on the ground.
When the prop is rotating, say to the right, it needs to something to counter the right way rotation (otherwise the prop would roll off and roll away to the right). The plane is it's counterweight.
So if the prop spins to the right the plane wants to spin to the left, this is what caused some planes to roll over on their backs when the throttled was opened too fast.
The slipstream from the prop causes the "sway" because the slipstream hits the vertical stab and thus pushes the tail end of the plane in one direction (depending on which way the prop is turning).
The tourqe is what makes the plane "spin" or roll at low speeds (specially noticable at the top of a zoom).
Enduro, I don't know how much slipstream is generates when slow and throttle on idle, shouldn't be THAT much so can't really explain that but ground loops (plane sway too fast and make a 180 or degree turn) "should" not be caused by tourqe.
Ever seen a car nose up when accelerating? Can be seen at dragraces, this is the effect of tourqe.
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To reduce the slipstream effect, try to reduce also RPM to minimum. Optionally, you may also stop the engine a soon as you touch the ground.
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The ground loop isn't necessarily cause by engine torque or p-factor etc. Even low torque tail draggers have a ground loop tendancy. The distance between mains and the tail wheel may be the most important factor for stability.
The way I land Corsairs to to three point them, by holding them nose up low over the runway until i stall out. I tend to bounce down at 75 or so and can get it stopped quickly before any ground loop.
The other trick you can do is turn the engine off. (course that kind of refutes my earlier point)
--P.
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51 needs more torque.
IRL you hit that thing to 100% and you'd dig the prop if you didnt roll the plane over on its back first.
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Originally posted by Enduro
Ah, Lady slipstream, eh? Well, remember that I'm talking about an aircraft with its throttle at full idle here. Is the slipstream effect so apparent in the Hog when it's very slow & dirty?
Another question, then...why is slipstream so apparent in AH2's Hog and barely noticeable in the other a/c, like the 109, P-51 and Jug (when slow with idle throttles)?
And is it just me, or do others have to apply rudder with manual take off in planes that ought not have slipstream issues at all -- like the Me262 and the P-38L?
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Originally posted by Wilbus
The "swing" on landing and takeoff isn't caused by tourque actually. It's caused by the slipstream from the propeller hitting the vertical stab, this is why rudder helps to counter it. All planes have it, specially when taking off as you throttle up.
QUOTE]
If by "swing" you mean yaw then my impression is that torque does contribute. Engine rotation causes roll which increases downward pressure on undercarriage on one side relative to other, which in turn increases friction/resistance between axle/wheel & wheel/runway on that side hence tending to turn plane towards that side.
Gyroscopic effect of rotating mass (ie engine) moving forward also has an effect but don't ask me to explain this as it needs someone with a brain the size of a small planet.
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I'm pretty sure most people think the planes are modelled way more sophisticated in AH than they really are.
The swing on landing is simply a bug IMO. If I recall it correctly it can do it even with a blown out engine on landing.
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Whiskey, I love the soccer avatar! You make it yourself?
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go to http://www.Zenoswarbirdvideos.com and watch the F4U training video. alot of useful information that will help you understand the plane and how to handle some of the things it does.
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When I land a corsair I kick the rudder to the right (set it to neutral) doesn't swerve at all. Combat trim has it left to counteract the torque. J&L keys are rudder on keyboard or should be unless remapped.
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Originally posted by Simaril
Whiskey, I love the soccer avatar! You make it yourself?
Thanks, but I wish m8.
Check out spacespider.net.
:aok
Rugby's my game - I could never do that with a footy :D
Regards
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Whisky you may be right but I've never heard anything like that before.
MrRipley, doubt it is a bug. It's been around since th F4u was released more or less, think they would have spotted and fixed such a bug by now.
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The trick to landing all airplanes is the C and V keys. Set them to be left and right brakes.
Do I have to say it any more clearly?
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Originally posted by peregrin
The ground loop isn't necessarily cause by engine torque or p-factor etc. Even low torque tail draggers have a ground loop tendancy. The distance between mains and the tail wheel may be the most important factor for stability.
peregrin is the most correct here, although Wilbus is correct in pointing out that P-factor is the reason that the F4u always tends to start the ground loop to the right. The most significant factor is that the F4U has a very short moment (distance) between the front wheels and the tail wheel. All short fuselage tail dragging airplanes have the same problem, most notably is the Folker Dr.1 from WW1. Even the reproductions are very difficult to land even with differential braking.
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A friend of mine's father died just after the war when his Corsair ground-looped. He was an experienced pilot - but it was known to be dangerous.
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Well, since the revised FM of AH2 came along, the F4Us are far less prone to ground looping.
Nonetheless, I strongly suggest 3 pointing your landings and maintaining backpressure on the stick while braking. Do this and you'll never suffer another ground loop.
My regards,
Widewing
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Sorry to flog this one but it was niggling me & thought it might be of interest to us weekend physicists.
I dug out some old notes.
There are 4 forces tending to yaw a plane on t/o.
1. Reactive force. See my contribution above.
2. Slipstream effect. Beautifully described by Wilbus.
3. Gyroscopic precession. Spinning mass of propellor & engine makes them subject to this effect. If a force is applied to a spinning gyroscope, the gyroscope acts as if the force were applied at a point 90 deg to the direction of rotation. When nose goes down on take-off gyroscopic precession pushes nose to left. Those old enough to remember toy gyroscopes spinning on bits of string will know what I mean :)
4. P-factor (asymmetric blade effect). In a tail dragger the downward moving prop blade has a higher angle of attack & thus produces more thrust. When props rotating clockwise (as viewed from cockpit) this yaws plane to left.
Corsair scores badly on all these because
1. Big rotary engine (1 & 3)
2. Big diameter prop (2)
3. Tail dragger (4)
P38 suffers little from yaw on take off 'cos inline contra-rotating engines & horizontal AoA (tricycle u/c) on take-off.
Regards
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Very nice Whisky, more factors then I thought and I am a hobby pilot (then again I am a glider pilot so don't have to worry about those factors :D )
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Took me years(lol) took figure out the best way to plop down a hog..
Use the tail hook...:D
Seriously,map the left and right brakes in case after landing you get careless with your taxi to the rearm pad.
Come in full flaps,gear down and get thing as slow as you can(100mph or less) and do a 3 point landing...with the stik pulled all way back on landing to lock tail wheel.
:aok
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Rgr Sirlion same thing as I do. If it is done that way I get no sway. If I land some other and get sway I have left/right differential toe brakes on the pedals, they can help alot :D
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Great input, everyone. Thanks! :)
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I never do a 3 point landing in he F4U!!! always land on the main gear and let the tail settle,You should have no problems landing,.this was how pilots would have been taught during wwII.I stress do not attempt 3 point landing.it's possible but not the best way,and makes a ground loop more likely.;)
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The F4U behaves like any tailwheel airplane. You should not use brakes on landing. Wheel landings and 3 points are both fine. Simply use your rudder to align the longitudinal axis with the runway, and make SMALL adjustments.
The CG of all tailwheel airplanes is BEHIND the main gear. Therefore, if the tail starts to move left or right, it has a tendency to move MORE in the same direction ---> negative stability. That is why you can't allow much deviation in tail movement, using the rudder.
Just like in the real world, if the tail does start to "get away", you apply full power and do a go-around. That is the safest thing to do.
As the tail comes down after landing, GYROSCOPIC PRECESSION, (Not spiraling slipstream, torque, or P-factor) will cause the nose to gently yaw to the RIGHT. (During a wheel landing, not a 3-point). Add a small amount of left rudder as the tailwheel comes down. Add too much, you'll loop her, too little, you'll loop her. As tail comes down, stick to your belly and apply brakes.
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The training video for the F4U says to do 2 point landing and to keep the tail up as long as possible because at the 3 point angle there isnt enough clean air to allow the rudder operate effectively.
Since watching that video I dont have as many problems with ground looping when I do 2 point landings.
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The F4U behaves like any tailwheel airplane. You should not use brakes on landing. Wheel landings and 3 points are both fine. Simply use your rudder to align the longitudinal axis with the runway, and make SMALL adjustments.
If you have your Left and Right brakes bound to C and V, you can easily control any spin as it goes down the run way AND slow down the aircraft at the same time.