Webinar: Flight with Broken Flight Controls

[djpacro]

Presenter: Gordon Penner, two time MCFI-A, FAA Gold Seal Instructor

 

How to handle jammed or broken flight controls and get safely to the ground.

 

Thursday 10th January 12:00 pm - 1:30 PM AEDT

 

Register free at https://www2.gotomeeting.com/register/980209042

 

 

[pudestcon]

This webinar is one I would like to participate in - timing is the problem.

 

Are these webinars recorded and able to be accessed at a later time?

 

Pud

 

 

[djpacro]

yes, see it afterwards at http://www.eaavideo.org/channel.aspx?ch=ch_webinars

 

 

[pudestcon]

Thanks DJP

 

Pud

 

 

[SteveJeff]

Watched the webinar. Quite interesting.

 

I found a flt control malfunctions is pretty manageable assuming the control doesn't jam to an extreme. What I wonder if when something breaks, wouldn't it slam the surface to an unfavorable position i.e. towards an extreme, let's say more than a half deflection, and jam there where you don't have enought authority to stop it with the remaining controls? Or due to flapping/fluttering wouldn't it jam to an extreme?

 

Of course not talking about the case when the pilot got a large deflection and the jam occured at that moment jamming the stick in that current position.

 

What do you think?

 

 

[djpacro]

Need to consider failure modes of the specific configuration to assess what the control surface may do. e.g. discuss the Pitts elevator lost due to structural failure of control stick at the base (this happened to a local airplane some years ago, also to a Fuji control column years earlier). Of course aileron is lost as well.

 

Weight of the control system is equivalent to somewhere around a 5 kg forward force on the stick. In straight and level trimmed flight - elevator is trimmed so if that's when the stick breaks then nothing happens, the elevator is trimmed. More likely to fail when the pilot pulls back hard on the stick, say to enter a loop. Elevator will return to the trimmed position ......

 

 

[facthunter]

DJP unless the trim is a spring.

 

Emphasis should be made as to the inability of anyone to fly a plane without a dual capability on the elevators. Ie a backup system. A controllable trim tab could be considered a separate pitch control The gazelle for instance has only a spring. Jabiru also If the elevator control rod detached, trim does nothing, stick does nothing. Whether the plane would pitch up or down would depend on other factors like fore and aft balance, which few pilots can do much about if flight. I consider the lack of pitch control backup as a serious design flaw . Nev

 

 

[djpacro]

Ok, change my example to a Husky which has springs as the elevator trim system - same situation as my Pitts example. If the failure was at the rear bellcrank then indeed the trim system has been lost as well.

 

The good news with spring trim systems is that it eliminates tab flutter following failure of the tab drive as a consideration.

 

 

[facthunter]

That it does, but a blunt trailing edge would prevent that would it not?. I tend to think the best is an adjustable horizontal stab by a screw jack. Again it has to be done right or you have something else to go wrong. Nev

 

 

[SteveJeff]

I thought about a conventional control system, elevator with trim tab with its separate control, not spring or jackscrew.

 

I practiced a lot of trim + power landings in a Cessna, I would say it's pretty manageable, at least to get you safely on ground, if not even the airplane intact. You have chances to brake the nosewheel, propeller, but at least you won't be fatal injured, I think in such a rare and critical situation, yours and passengers safety is the first thing despite the airplane might be demolished.

 

If hinges are not broken, the only two possibilities I imagine, not sure if likely to happen, just thinking about them, are either the surface vibrates, oscillates (maybe from stop to stop) and eventually, finally jams in an unfair position to recover with the remaining controls or when one componnent from the flight control systems broke, e.g. pulley, pushrod, the break reaction effect might slam the surface in an extreme position, however, don't have enough knowledge about how flt control system componnents are rigged if it would be possible to slam so when it breaks. What do you think?

 

 

[djpacro]

One real life example at http://www.usnationalaerobatics.org/IACSafetyForum/default.aspx?g=posts&t=234

 

Notes of others at the same website.

 

 

[SteveJeff]

Flutter at high speed below VNE.

 

During a descent for an airshow at 240 mph..

 

240 mph for that airplane seems to be above Vne. I'm sorry, but I would say more pilot fault than airplane fault. Even if it was a modified version, I guess 240 mph would be pretty close to VNE. It is not the first time when at speeds close to VNE happened something to broke.

 

Anyway, I think pilots should be more reluctant to take flight at such speeds especially if there is no possibility to bail out quickly. Just my 2 cent opinion...

 

 

[djpacro]

The lesson there is to be wary of Experimental aeroplanes. Designers of the 52TW variant reduced the diameter of the tab actuating rod to a small fraction of that on the standard 52. A low time machine operated always well within g limits and below Vne etc suffered fatigue failure as a result of poor design.

 

 

[SteveJeff]

Was it an experimental model modified by the owner? As far as I know, 52TW, they are factory-built in Romania at Aerostar, a local reputable company in aircraft design/maintenance.

 

 

[djpacro]

As built by the factory - the TW variant is quite a bit different from the robust standard model 52.