F4U?

[olds442]

I've always been told its an effect of torque at low speeds, but then again I could be wrong. 

i thought that to but the p47 has the same eng and so dose the f6f

[SIK1]

The prop on the F4U is huge 13'1" that's a lot of gyroscopic effect. The rudder is also very large so a small amount of rudder input can have dramatic results.
I agree that the hog does seem more inclined to ground looping than any other plane. I know I don't have near the problem in 109's that I do in F4U's with ground looping and I would think they (109's) would be just as prone if not more so than the F4U, because of the narrow track, light weight, and large amounts of torque.

[mtnman]

i know how to land it your not getting what im saying im just asking why dose this plane do it but other planes dont?

Based on your initial post, "how come" could be taken as either a question on physics or on technique.  Most of us chose to answer the technique aspect, because it's easy to solve.

I've always understood it to be caused by gyroscopic precession, enhanced by the high nose angle (and tail wheel design) of the F4U.  The short, castored, tail wheel, the need to keep the big prop up off the ground, and the differing thrust from the right-hand side of the propeller arc vs the left all work against you.

With an RC tail dragger, you can feel this effect if you lift the tail with your hand while the engine is running, even at idle.

P-factor, torque, slipstream, and the gyroscopic effect of the propeller are all trying the turn the plane to the left.  I actually think they're trying to cause a left spin at that low airspeed, but contact with the ground obviously prevents that.  I could be wrong.  The gyroscopic force could be applied in other directions though, depending on which direction the force was applied to the propeller disc.  If you push the stick forward, I think you'll yaw right, where pulling the stick back gives you a left yaw.

If you land at a "highish" speed in the F4U (100mph or so), the slipstream will allow you to maintain control with your rudder (even if you just let it sit there in the middle).  But, as you slow down, you lose rudder effectiveness, while at the same time not having enough control with the tail wheel to counter the turning force.

Even when the tail wheel is in contact with the ground, it doesn't resist this force in the F4U, because the tail wheel spins freely like the front wheel of a shopping cart.  If the plane wants to swing the tail to one side or the other, the tail wheel doesn't resist it like you might expect.  The F4U has a locking mechanism for the tail wheel though, that's activated by holding the stick back (up elevator) in game.  that will lock the wheel wherever it happens to be pointing at the time.  Lock it while your rotating to the left, and it'll be really hard to go straight, or to the right...

Holding the stick back at landing does two things.  Obviously, it locks the tail wheel.  Second, it helps "plant" the tail wheel firmly on the ground, so that as the rudder loses authority, the (locked) tail wheel takes over and the result is straight tracking down the runway.

I haven't looked at the other planes closely enough to tell you how they differ in this matter.  If the upward angle of the nose is reduced as compared to the F4U, the tendency would probably be less.  If the design or height of the tail wheel is different, that would matter too.  Smaller prop?  Different placement of the main gear?  They'd all factor in.

[W7LPNRICK]

I don't think it's the engine torque, prop size etc. Too many other AC have that issue & don't ground loop. I believe it's the gull wing placing the engine in a precarious position regarding fulcrum/pendulum/center of gravity vs wing angle on landing. Isn't the angle much steeper when the tail wheel begins to drop? causing the main wing to bite in a bit deeper increasing lift for a split second...making it float? If I lower the tail wheel slowly as the horizontal stab stalls, the "Floating Feeling" is not there. 

[nrshida]

Has the original Corsair training film been presented on the AH BBS? It mentions this effect.

[mtnman]

I don't think it's the engine torque, prop size etc. Too many other AC have that issue & don't ground loop. I believe it's the gull wing placing the engine in a precarious position regarding fulcrum/pendulum/center of gravity vs wing angle on landing. Isn't the angle much steeper when the tail wheel begins to drop? causing the main wing to bite in a bit deeper increasing lift for a split second...making it float? If I lower the tail wheel slowly as the horizontal stab stalls, the "Floating Feeling" is not there.  

If you're getting a "floating feeling", I'd argue that you're landing too fast, which makes the ground loop more likely.  If you land at a stall, there isn't enough lift being generated to give you the floating feeling.

Landing in 3-point configuration practically eliminates all of the ground looping tendencies, even without differential braking.  I just fixed my brakes, but I flew for about 6 months without any brakes at all.  I fly the F4U exclusively, and I don't ground loop.  Heck, sometimes my tail wheel is the first wheel on the ground!

The thing that makes the conventional-geared planes prone to ground looping is the gear being placed ahead of the CoG.  Difference in design is what makes one plane more likely to ground loop than another, even with the same engine.  The single engine propeller plane characteristics that make the plane want to turn are present in tricycle-geared planes too, but the gear configuration and it's relation to the CoG makes them far less prone to ground loop.

[W7LPNRICK]

In reality most flying instruction manuals teach not to land in a near stall, but to fly to the landing. Otherwise, you are completely at the mercy of a gust of wind (Non existent in AH), but I like thinking I'm trying to do it "Real".

[SectorNine50]

In reality most flying instruction manuals teach not to land in a near stall, but to fly to the landing. Otherwise, you are completely at the mercy of a gust of wind (Non existent in AH), but I like thinking I'm trying to do it "Real".

Actually, in a lot of GA aircraft, you should hear the stall horn right before touchdown.  However, stall horns tend to have a bit of lee-way to them.

Mooney's are a great example of this.

[mtnman]

In reality most flying instruction manuals teach not to land in a near stall, but to fly to the landing. Otherwise, you are completely at the mercy of a gust of wind (Non existent in AH), but I like thinking I'm trying to do it "Real".

You don't need to come in anywhere near a stall.  You just hold your flare an inch off the ground, so you stall as you touch.  You can make your approach as fast as you want.

Are most flying manuals written with tail-draggers or tricycle gear in mind?  Honest question, I have no idea...

[W7LPNRICK]

Don't know for sure. I remember specifically a P-38 flight Instruction Manual I saw on here where they told students to under no circumstances to float in to their landing, but to fly it in at 110...? They warned of dire consequences for attempting to float it in. 

[nrshida]

Swerving on landing is mentioned in the F4-U film I posted here:-

http://bbs.hitechcreations.com/smf/index.php/topic,305117.0.html

If you fast forward to 6:28 of part 2 (http://www.youtube.com/watch?v=n-PwTTQz6Zw), it mentions buffeting with the tail on the ground. Also that a three point landing is approximately the stalling angle of attack.

[Ruah]

I find that you want to avoid the 'bounce' in the f4f just like in th 190 - which also suffers from a roll over to the right if you bounce it on landing.  To overcome this, as mentioned, i bring the blan in a little fast, not use too much flap, touch th front two gears first and then either cut th engine and play with th brakkes, or power it down to idle and watch the ball.  The wost thing to do imo is to float above the field and 'drop' the plane down because that causes the bounce, the liftoff, and the stall-roll.  this is very similar to the 190s imo and is moe to do with the oversensitive landing gear (seems to have springs in it) then with the engine torque (which is the killer, but only because of th bounce).

[W7LPNRICK]

The second film specifically states not to pull back on the stick at landing speed as this will cause strong swerving, don't apply brakes until the rear wheel lands naturally.

[SIK1]

The second film specifically states not to pull back on the stick at landing speed as this will cause strong swerving, don't apply brakes until the rear wheel lands naturally.

Yeah,but in a real corsair you can lock the tailwheel with a lever.

[mtnman]

It's interesting that they warn against braking, too, until the tail is down.  This is the first time I've "officially" seen the "hold down elevator to keep the tail up" idea, although I use it for landing tail dragger RC planes if I don't land 3-point.

I land more like the field carrier landing shown.  Except I don't usually drop it in as hard.  My approach is in the 115-120mph range; I just hold my flare barely off the ground until I touch all three wheels down together.

They must assume a new pilot won't have the feeling for the stall down yet, stating that for your first landing you should keep the tail higher than normal?  By "high" they show "level"...  They also say you "can" set it down on two wheels, not that you "should".  It's almost like he's giving the pilot permission to do it that way.

"Buffeting"...  I wonder when the gyroscopic precession term (and others) was first used?  Maybe after this film was made?  I don't understand what he means by that.

I've been taught that "In an ideal situation the aircraft will stall just as the main wheels touch the runway."  In the F4U, as stated in the film, that would imply a 3-point landing.

The plane can be landed either way, obviously.  It's kind of nice actually, that the less-experienced guys have the same trouble landing it in the game that the inexperienced pilots had landing it in RL...