What caused the crash ?
#1
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What caused the crash ?
Check this out guys.....
What's the cause ? IMO being tail heavy....
[youtube]http://www.youtube.com/watch?v=-inMx8qExhw&feature=related[/youtube]
What's the cause ? IMO being tail heavy....
[youtube]http://www.youtube.com/watch?v=-inMx8qExhw&feature=related[/youtube]
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RE: What caused the crash ?
What caused the crash? The fact that that airplane was never flying without ground effect.
That's nothing more complicated than a simple stall. It wasn't ready to fly, it got horsed off the ground, and the moment it lost ground effect it rolled over. Aileron to correct aggravated the stall, as it ALWAYS MUST, with the result being more up elevator (increasing the AoA even more) and the inevitable spin into the ground.
Nose down, more airspeed, that plane would have flown out just fine.
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RE: What caused the crash ?
Knowing how the old Texan really bites if you don't handle it right I gotta agree with gboulton.
Pilot error = stalled plane
Mike
Pilot error = stalled plane
Mike
ORIGINAL: gboulton
What caused the crash? The fact that that airplane was never flying without ground effect.
What caused the crash? The fact that that airplane was never flying without ground effect.
That's nothing more complicated than a simple stall. It wasn't ready to fly, it got horsed off the ground, and the moment it lost ground effect it rolled over. Aileron to correct aggravatedthe stall, as it ALWAYS MUST, with the result being more up elevator (increasing the AoA even more) and the inevitable spin into the ground.
Nose down, more airspeed, that plane would have flown out just fine.
#10
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RE: What caused the crash ?
ORIGINAL: Kostas1
IMO it had enough airspeed over the control surfaces.
IMO it had enough airspeed over the control surfaces.
1) At BEST, your frame of reference is GROUND speed
2) Ground speed judged from the worst possible angle (aircraft traveling away from your point of view)
3) Airspeed over control surfaces has only an anciallary association with whether an aircraft is stalled or not
I'd say we can safely disregard that opinion.
On the other hand, an aircraft that leaves ground at an airspeed below its stall speed in its current configuration, but above the speed needed to stay airborne in ground effect will exhibit certain characteristics that are independant of frame of reference, or point of view.
1) It will fly so long as it stays in ground effect, which occurs within approx. 1 wingspan AGL (Check)
2) It will roll violently to the left upon exiting ground effect. (Check)
3)Right Aileron input will aggravate the stall, since the left aileron will deflect downwards, INCREASING the AoA of the stalled wing, thus increasing the roll to the left. (Check)
4) On any properly balanced plane, the CG being relative to the now stalled wing, the nose will drop as the airflow demands a lower AoA (Check)
5) Again given that the CG is relative to a now stalled wing, elevator input will produce a violent reaction. (Check)
6) UP elevator will simply increase the AoA even more, making the stall unrecoverable at low altitude. (Check)
In short, in this situation, the airplane will attempt to roll left, and head for the ground. The immediate INSTINCTIVE reaction of every human pilot in the world will be to counter undesirable roll and pitch actions with opposite control inputs....right aileron and up elevator. Both will serve only to make a bad situation worse, and result in the airplane in the ground, nearly inverted, to the left of it initial flight path. (Check)
So let's see:
The airplane did EXACTLY the sorts of things an airplane would do if it took off too slowly.
The pilot did EXACTLY the sorts of things that human insitinct dictates he will likely do when faced with such a situation.
The airplane reacted to those inputs EXACTLY as it would if it were stalled.
Or, optionally, there was plenty of airspeed over the control surfaces because it looks like it based on the ground speed, and some other mysterious or unknown issue is to blame here.
*shrug*
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RE: What caused the crash ?
IMHO it could be his throw rates were too high, and he had no or hardly any Expo making his controls too sensitive. Also the tail could have been heavy. All things added up, it does make the aircraft fly that way.
It's too bad to see a nice plane like that crash.
I know what happened! A Jap Zero got him on take off!
Pete
It's too bad to see a nice plane like that crash.
I know what happened! A Jap Zero got him on take off!
Pete
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RE: What caused the crash ?
ORIGINAL: richardgerardi
I think that long metal thingy coming out of the radio is at fault. Haven't seen one them in a long time.
I think that long metal thingy coming out of the radio is at fault. Haven't seen one them in a long time.
Nothing wrong with his radio, I still fly 72 and refuse the new 2.4 and my planes don't fly like that.
Nice try!
Pete
#14
Thread Starter
RE: What caused the crash ?
ORIGINAL: Oberst
IMHO it could be his throw rates were too high, and he had no or hardly any Expo making his controls too sensitive. Also the tail could have been heavy. All things added up, it does make the aircraft fly that way.
It's too bad to see a nice plane like that crash.
I know what happened! A Jap Zero got him on take off!
Pete
IMHO it could be his throw rates were too high, and he had no or hardly any Expo making his controls too sensitive. Also the tail could have been heavy. All things added up, it does make the aircraft fly that way.
It's too bad to see a nice plane like that crash.
I know what happened! A Jap Zero got him on take off!
Pete
Pete i agree with you.
I think that x3 majour causes led to the crash.
Airspeed+being Tail Heavy+very Large throws+Big Inputs[X(]
#17
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RE: What caused the crash ?
I'm going to go with pilot error on this one. Whether it was when the plane was in the air or when the plane was built either way the pilot was at fault.
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RE: What caused the crash ?
Looking at the plane before take-off, the elevator appears to not be level with the stabilizer, looks like it has down incidence ? On take-off the up elevator lifted off the ground but when he neutralized the elevator on the transmitter, the elevator went to the "down" side would that account for the "dipping" of the airplane ?
Just my guess...........
I too had a Texan that did this same thing. Tried to take off with too little air speed.
Just my guess...........
I too had a Texan that did this same thing. Tried to take off with too little air speed.
#19
RE: What caused the crash ?
I didn't see any problem with the elevator position. Also, I'm thinking takeoff speed while perhaps border line should have been adequate as lift off was quite normal. Most often when plane speed is too low, problems initiate quicker than seen. Most often if seriously tail heavy, the plane will lurch into the air, and that didn't seem the case.
What I saw initiate the sequence of problems was the plane first yawed left. While that could have been (and probably was) the pilot simply getting off the rudder he'd been holding for the takeoff run, because the yaw is so noticeable, I'm going to go with the theory that for whatever reason there was too much left yaw and that combined with perhaps too much throw in the elevator or slight tail heavy condition or both.. the plane was snappy (obvious).
We'd need to know if the plane was built with the correct amount of right thrust. None could easily explain what happened. I'm currently building an AT-6 and a good friend who is a very good pilot was telling a story about how an AT-6 he maidened for a guy almost got the best of him on takeoff because it didn't have enough rudder throw as the plane requires a lot of rudder on takeoff and he'd nearly buzzed the flight line holding full right rudder.
What I saw initiate the sequence of problems was the plane first yawed left. While that could have been (and probably was) the pilot simply getting off the rudder he'd been holding for the takeoff run, because the yaw is so noticeable, I'm going to go with the theory that for whatever reason there was too much left yaw and that combined with perhaps too much throw in the elevator or slight tail heavy condition or both.. the plane was snappy (obvious).
We'd need to know if the plane was built with the correct amount of right thrust. None could easily explain what happened. I'm currently building an AT-6 and a good friend who is a very good pilot was telling a story about how an AT-6 he maidened for a guy almost got the best of him on takeoff because it didn't have enough rudder throw as the plane requires a lot of rudder on takeoff and he'd nearly buzzed the flight line holding full right rudder.
#22
RE: What caused the crash ?
As an experienced pilot you feel it in the air when something is wrong with a servo. It is not like this was the maidenflight or something.
There are a few images of the build here: [link=http://www.rcflyg.se/forum/showthread.php/13680-Bokis-teaser?s=84dafd4fcc8deabb0f689cbbeed415fe]Build [/link]
A flight well before the crash;
[youtube]http://www.youtube.com/watch?v=5awo2KQyCAQ[/youtube]
There are a few images of the build here: [link=http://www.rcflyg.se/forum/showthread.php/13680-Bokis-teaser?s=84dafd4fcc8deabb0f689cbbeed415fe]Build [/link]
A flight well before the crash;
[youtube]http://www.youtube.com/watch?v=5awo2KQyCAQ[/youtube]
#23
Thread Starter
RE: What caused the crash ?
The thing that i really cannot explain is this.
During the first moments of taking-off,
and while building speed on the ground,
on a tail-dragger you must add some Up-elevator in order your airplane not to nose-over.
I guess that the pilot does that on the video...BUT, as soon as the airframe is OFF the ground and he adds some elevator more,
the airframe starts to wobble all over the place......That's why i said IMHO it is tail-heavy (little or much) & extreme movements on the elevator servos.
During the first moments of taking-off,
and while building speed on the ground,
on a tail-dragger you must add some Up-elevator in order your airplane not to nose-over.
I guess that the pilot does that on the video...BUT, as soon as the airframe is OFF the ground and he adds some elevator more,
the airframe starts to wobble all over the place......That's why i said IMHO it is tail-heavy (little or much) & extreme movements on the elevator servos.
#24
RE: What caused the crash ?
The video that I posted is of the maiden flight, and yes it does go a little up and down right after take off. This is nothing strange though on a maiden flight and taking off from a rough field. The airfield is not at an RC club it is simply a grassy patch on his farm. On a rough grass field, an experienced flyer can pull up a little early and then stay low to build up speed. This is also done on full scale airplanes. Add to that a bit of nerves and no expo, and you have the result in the movie. There are several of us old-school people that do not like expo, to us the planes just feels a little bit too unresponsive and dead with expo and we have to rely on steady thumbs instead. In the crash movie the take off is intended to be similar but then goes wrong due to a faulty elevator servo, according to the pilot, I cannot see any reason to question that.
#25
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RE: What caused the crash ?
ORIGINAL: gboulton
What caused the crash? The fact that that airplane was never flying without ground effect.
What caused the crash? The fact that that airplane was never flying without ground effect.
That's nothing more complicated than a simple stall. It wasn't ready to fly, it got horsed off the ground, and the moment it lost ground effect it rolled over. Aileron to correct aggravated the stall, as it ALWAYS MUST, with the result being more up elevator (increasing the AoA even more) and the inevitable spin into the ground.
Nose down, more airspeed, that plane would have flown out just fine.
He had the ailerons reversed.....and way too much throw!!