HELP! I recently had a catastrophic crash on my maiden flight of a Hanger 9 ARF: P-51 Blue Nose Mustang. On takeoff the plane rolled to the right I believe since the right landing gear was severely damaged. Also, the fuselage ame aprt in two pieces as teh nose hit the ground. I am assuming this was due to an uncompensated engine torque problem. I seem to remember a formula of 0 .1 ounces of counterbalance for every 0.1 cu. inch engine displacement. the engine is a TT F130, 4 stroke. That means I should add 1.3 ounces to the left wing? Any thoughts on this?

I've never added counterbalance to compensate for torque. I've only laterally balanced a couple of my planes....

I use the rudder on take off to compensate for torque. The P-51 was never known for superb ground handling

Torque and P effects will turn the nose to the left. That's why your model probably has some amount of right thrust built in.

It sounds a bit like you expect the plane to fly itself.

Rudder and to some extent, aileron input is needed to correct. Was this your first airplane?

In spite of it being one of the most beautiful planes ever made, the P-51 is one of the more difficult planes to fly and is not for the inexperienced.

Typically they roll off to the left and cart wheel if the power is applied too suddenly and the nose pulled up too soon.

Engine torque will roll the airframe to the left, this why we use a few derees right thrust to compensate. As for the wings, you want them to balance evenly over the centerline of the airframe.

Despite all this, none of it should have caused a crash by itself.

Maybe you were'nt ready to fly this plane.................

If it was at takeoff it was P factor not torque. No amount of counterbalance will work properly for P-Factor, this is counteraced with rudder.

err maybe you mean right rudder?

Denis

I corrected it before your post.

You need to use the rudder to fly it correctly and not horse it off the ground. Also, make sure that the plane is Ballanced laterally.

SpaceRockMan,


Torque is the wrong term and this was discussed before you got here.

The problem that caused your crash, is the same as what caused that deadly crash at Oshkosh, a couple of years ago.


It is not torque that causes a plane to veer off its course, during the take-off run; but the prop's spiral slipstream, hitting the fin and the rudder on one side...
Because of ground deflection, with the tail low, hugging the runway; the bottom of the slipstream hits the fin and the rudder from the right, requiring left-rudder to correct.

Once the plane gains some speed and the tail rises, it is the top of slipstream that hits the rudder and the fin; but now from the left! This requires a force reversal, because now right-rudder is required, to keep the plane tracking straight.

This confuses newbies, even to the brink of hurrying the take-off, ground-looping and crashing their model...Or their full-size plane.
I am sorry it had to happen to you.


Extending the take-off run a bit, to achieve greater speed, is the solution.


The P-factor is another issue... When a plane climbs out after take-off, it is at a rather low speed with the nose high.
As a result, the descending blades of the prop have a higher eventual angle of attack, than the prop's rising blades.

As a result the plane tends to veer to the left during climb-out, requiring right-rudder input from the pilot, to fly straight...

THANX everyone. Great advice. I guess I'll need a lot more experience before I get it right.

one last thing i would do, is make sure you have enough ground speed before you lift off... Ive seen some guys try and yank the planes the ground before they causing them to stall and sometimes crash...this usually happens on less forgiving scale type airframes

G'day You did not say whether this was your first plane or your 100th.

Trainers and models designed as "model aeroplanes" tend to fly them selves to a certain extent. Scale models usually don't and especially warbirds like the Mustang.

I have a number of scale and warbird type models and they are all far more like real planes to fly than trainers etc.

I killed a P-40 in a similar way to yours. I had been flying trainers and with them you could just add lots of power and the plane would take off by its self. The P-40 started to roll on low power and as I increased the power it was gaining speed when it hit a bump in our not so smooth field and jumped into the air. I then gave it lots of power (wrong) and it leapt into the air, stalled, dropped a wing and cartwheeled. End of story. It was trying to fly before it was actually flying.

I also have an Auster AOP-9 which has to be very carefully handled to get it into the air. It needs a long slow gradual acceleration and it then floats off but if you try to give it lots of power too soon, it just puts its nose up and stalls.

Sounds like you are learning what I have already learned by the bash and crash method. It works, but it is a bit expensive.

Dar,
I live close too Oshkosh, and was there that day. That Mustang crash was caused by two P-51's that were landing at two different speeds. The trailing mustang was a modified P-51 and it was landing much faster "still airborn" when it ran into the back of the leader which was allready on his mains.[X(]

Quote:

ORIGINAL: Iflyglow

Dar,

I live close too Oshkosh, and was there that day. That Mustang crash was caused by two P-51's that were landing at two different speeds. The trailing mustang was a modified P-51 and it was landing much faster, ''still airborne'' when it ran into the back of the leader which was already on his mains.[X(]

David,


The plane that crashed was a P-51C, I believe.

What its pilot tried to do was an 'aborted landing', once he had realized the demeanor he was in; which then resulted in a ground-loop to the right...
This would have also happened in any take-off attempt at too low a speed.

It was a very rare P51A with an Allison. The report was both thought they were the only P51 the tower was talking too. One guy did not know one was behind and one did not know one was below. Very sad all the way around.

Dar,
He never gave it power to go around "aborted landing", and just did not see him and flew into the back of the "D" Model Mustang that was allready on its mains. The second pilot (Precious Metal not to be confused with the Griffin powered Mustang D raceralso called recious metal) which is a moddified clipped wing A Model" did not try to go around at all. This does not really have anything to do with this modlers problem other than they are both P-51's. The full size Mustang was very low on the power setting, and was flairing for a landing at the time of the impact. His prop was in the fuse of the other faster than he knew what happened. It was very sad, and he should have known that his landing speed was higher than a Stock Wing configured "D Model Mustang".

http://www.youtube.com/watch?v=PLnKYJLzjjI

http://www.youtube.com/watch?v=8I0J3...eature=related

http://www.youtube.com/watch?v=KD0No...eature=related

http://www.youtube.com/watch?v=VJoBdwgq_DU

David,


I believe you know better than my guess, which model was involved in this...
It is the Allison 'A' and not the similar looking Merlin 'C'.

...But its pilot DID give it full power, just prior to it flipping over...
It could clearly be heard in the first clip, just before the engine was permanently silenced by the crash.


And my emphasis was on what was supposed to be 'torque'... Had it been torque, that plane would have flipped over to the left.

It flipped over to the right.

Thank you for the link to the videos, Iflyglow.

It seems to me that the right roll was produced by three simultaneous things:
1) Sudden power up (the last second increase in rpm can be seen in the video).
2) Quick full elevator up.
3) Right wing tip hooked under the tail of the other plane (view of which may have motivated the reaction of the pilot, who had blind frontal view). I can only imagine the confusion of the unfortunate pilot at that very moment. Left wing was free to lift, and it lifted hard as soon as its AOA was increased by elevator up.

Left roll was induced by 1, due to sudden engine torque.
Right yaw was produced by 1 and 2 combined, due to propeller being tilted backwards. This is called Gyroscopic Precession, and it can overpower the P-factor for big and heavy propellers.

http://www.faatest.com/books/FLT/Cha...opicAction.htm

The OP problem seems to be too much elevator too soon, combined with bad right landing gear, gyroscopic precession and a little of right rudder. The result was a right snap roll. Torque was helping him save the model.

Quote:

ORIGINAL: LNEWQBAN


It seems to me that the right roll was produced by three simultaneous things:
1) Sudden power up (the last second increase in rpm can be seen in the video).
2) Quick full elevator up.
3) Right wing tip hooked under the tail of the other plane (view of which may have motivated the reaction of the pilot).

Left roll was induced by 1, due to sudden engine torque.
Right yaw was produced by 1 and 2 combined, due to propeller being tilted backwards. This is called Gyroscopic Precession, and it can overpower the P-factor for big and heavy propellers.

Lnewqban,


The plane rolled to its RIGHT, prior to crashing... Torque; had it any effect, would cause the plane to roll to the left!

Please see photo of the plane [link=http://media.photobucket.com/image/allison%20mustang/bomarc_99/P-51%20SIG/1a35323u.jpg]here[/link] and below.

Torque has virtually no effect. Please re-read what I wrote in post #6.

Gyroscopic precession, due to the large, heavy propeller; would cause some yaw effect, upon application of the elevator and some pitching effect; upon application of the rudder.
But the effects would not cause the roll to the right, which was the ultimate cause of the crash...

There is nothing to support your third claim, although the prop hitting the other plane's left horizontal stabilizer and elevator, could have caused the nose of the doomed plane to rise...

I still do not totally agree on the sudden power up to go around, since he had allready hit the other guy with his prop which easily could have messed up the prop blades which would have given the sound of a power up. The crasgh was caused by collision with another plane and intanglement with the other plane. Its pretty clear that his left wing tip was caught under the other plane, and leveraged him to flip to the right.

Quote:

ORIGINAL: Iflyglow

...Its pretty clear that his left wing tip was caught under the other plane, and leveraged him to flip to the right.

Watching the clip again, it does seem to have happened (the rear plane's right wing snagging the front plane's tail), causing the front plane to pitch its nose down...

Dar,

Re-reading my and your posts, I cannot find anything wrong.

I can see sudden acceleration of the prop thru the stroboscopic image of the blades, which produced left torque (force only, since movement was blocked by the tail), and served the table for strong precession when the propeller disc was tilted back a split second later.

Right yaw happened, induced by lower speed of the tail of the forward plane, slowing the right wing of the aft plane, and helped by propeller precession.

Propeller hit, if any, was after the roll of the aft plane and nose down of forward plane had started.
A pure propeller hit would have caused exactly the opposite results, I believe.

I like to read your point of view, since I may see things that I don't observe by myself.

I don't know about trying to go around, but the aft pilot had a last second reaction.
At least, he input elevator up.
He reacted because he saw or heard something.

I believe that the crash would have had a different result if there wouldn't be been avoiding reaction.
Just think about it: aft plane would have never lift, it would have just pushed the forward plane, doing more damage to it.