Go Back  RCU Forums > RC Airplanes > Crash & Rebuild
Reload this Page >

What caused the crash ?

Notices
Crash & Rebuild Post your crash stories, pictures and if you want to document your rebuild you can do that here too!

What caused the crash ?

Old 04-19-2011, 08:05 AM
  #1  
Kostas1
Thread Starter
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default 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]
Old 04-19-2011, 08:43 AM
  #2  
RCBruski65
My Feedback: (44)
 
Join Date: Jul 2005
Location: Saginaw,MI
Posts: 252
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What caused the crash ?

When it lifts off it doesn't look too bad. When he lets go of the elevator the nose goes back down. Then when he pulls it's like it's way over controlled.
Old 04-19-2011, 08:54 AM
  #3  
Kostas1
Thread Starter
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default RE: What caused the crash ?

Maybe too much elevator throw ???
Old 04-19-2011, 09:17 AM
  #4  
vpresley
My Feedback: (162)
 
vpresley's Avatar
 
Join Date: Feb 2002
Location: Colorado Springs, CO
Posts: 739
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What caused the crash ?

Reversed aileron maybe. Trys to correct but it get worse?

Vince
Old 04-19-2011, 09:22 AM
  #5  
Kostas1
Thread Starter
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default RE: What caused the crash ?

hmmmmmm
Old 04-19-2011, 09:35 AM
  #6  
richardgerardi
 
Join Date: Feb 2008
Location: Little Egg Harbor, NJ
Posts: 343
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What caused the crash ?

I think that long metal thingy coming out of the radio is at fault. Haven't seen one them in a long time.
Old 04-19-2011, 09:48 AM
  #7  
gboulton
My Feedback: (15)
 
gboulton's Avatar
 
Join Date: May 2005
Location: La Vergne, TN
Posts: 3,743
Likes: 0
Received 0 Likes on 0 Posts
Default 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.
Old 04-19-2011, 09:51 AM
  #8  
Kostas1
Thread Starter
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default RE: What caused the crash ?

IMO it had enough airspeed over the control surfaces.
Old 04-19-2011, 11:56 AM
  #9  
mboland
 
mboland's Avatar
 
Join Date: Jul 2007
Location: BouldercombeQueensland, AUSTRALIA
Posts: 559
Likes: 0
Received 0 Likes on 0 Posts
Default 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

ORIGINAL: gboulton

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.
Old 04-19-2011, 02:55 PM
  #10  
gboulton
My Feedback: (15)
 
gboulton's Avatar
 
Join Date: May 2005
Location: La Vergne, TN
Posts: 3,743
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What caused the crash ?


ORIGINAL: Kostas1

IMO it had enough airspeed over the control surfaces.
Given that:

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*




Old 04-19-2011, 03:04 PM
  #11  
Oberst
Banned
 
Join Date: Jan 2010
Location: Lacona, NY
Posts: 1,840
Likes: 0
Received 0 Likes on 0 Posts
Default 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
Old 04-19-2011, 03:06 PM
  #12  
Oberst
Banned
 
Join Date: Jan 2010
Location: Lacona, NY
Posts: 1,840
Likes: 0
Received 0 Likes on 0 Posts
Default 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.


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
Old 04-19-2011, 03:46 PM
  #13  
1320Fastback
Senior Member
 
1320Fastback's Avatar
 
Join Date: May 2008
Location: Northern Occupied Mexico, CA
Posts: 998
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What caused the crash ?

As jerky as he is with the elevator its almost like he has it reversed or switched with the rudder? [X(][]
Old 04-19-2011, 11:29 PM
  #14  
Kostas1
Thread Starter
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default 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

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(]
Old 04-20-2011, 07:10 AM
  #15  
daveopam
My Feedback: (9)
 
daveopam's Avatar
 
Join Date: Oct 2002
Location: ELK CITY, OK
Posts: 7,810
Received 42 Likes on 37 Posts
Default RE: What caused the crash ?

I don't know about tail heavy, but every input of elev seamed to stall it. To me it's to much throw and trim way off on the elev.

david
Old 04-20-2011, 07:11 AM
  #16  
Kostas1
Thread Starter
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default RE: What caused the crash ?

yup[8D]
Old 04-20-2011, 07:41 AM
  #17  
bigpunisher365
Junior Member
 
Join Date: Jan 2011
Location: Oxford, AL
Posts: 3
Likes: 0
Received 0 Likes on 0 Posts
Default 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.

Old 04-20-2011, 07:46 AM
  #18  
mustangman177
 
Join Date: Aug 2002
Location: Cisne, IL
Posts: 747
Likes: 0
Received 0 Likes on 0 Posts
Default 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.
Old 04-20-2011, 09:05 AM
  #19  
AA5BY
 
Join Date: Sep 2006
Location: White Oak, TX
Posts: 2,398
Likes: 0
Received 2 Likes on 2 Posts
Default 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.
Old 04-20-2011, 11:11 AM
  #20  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default RE: What caused the crash ?

Well, I know the pilot is very experienced, so when he says there was a problem with the elevator servo I do trust him.


Old 04-20-2011, 12:52 PM
  #21  
Kostas1
Thread Starter
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default RE: What caused the crash ?

Well,

i'd like to know HOW he found that the elevator servo was faulty , AFTER the crash....
Old 04-20-2011, 08:50 PM
  #22  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default 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]
Old 04-20-2011, 09:45 PM
  #23  
Kostas1
Thread Starter
 
Kostas1's Avatar
 
Join Date: Dec 2005
Location: AthensAthens, GREECE
Posts: 3,566
Received 1 Like on 1 Post
Default 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.
Old 04-20-2011, 11:02 PM
  #24  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default 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.
Old 04-25-2011, 07:36 PM
  #25  
RC MANIAC119
Senior Member
My Feedback: (14)
 
Join Date: Nov 2003
Location: muskegon, MI
Posts: 941
Likes: 0
Received 1 Like on 1 Post
Default RE: What caused the crash ?


ORIGINAL: gboulton

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.
WRONG!!!!


He had the ailerons reversed.....and way too much throw!!

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.