Skymaster down!

[Ernie Martin]

I couldn't agree more with both of you, but Roger asked a question and I gave the best answer I had. I think some of us would still like to know: if it happens, is the information I have valid? Essentially: a) does the flap with the broken cable snap to neutral and b) will moving the flap lever to zero return the other flap to neutral and therefore remove the unbalnced forces causing the roll?

Ernie

[tropical]

Originally Posted by Ernie Martin

I couldn't agree more with both of you, but Roger asked a question and I gave the best answer I had. I think some of us would still like to know: if it happens, is the information I have valid? Essentially: a) does the flap with the broken cable snap to neutral and b) will moving the flap lever to zero return the other flap to neutral and therefore remove the unbalnced forces causing the roll?

Ernie

At 1000 feet and you are quick, you may make it. At 50 feet and 80kts on short final, I doubt it.

You're only other option is to fly with the flaps left at zero.

[edasmus]

Ernie,

I think your procedure to recover from an asymmetric flap configuration sounds logical. The only other thing I could mention would be an aggressive application of maximum power and a lowering of the nose to increase airspeed rapidly. With the sudden retraction of flaps on one side, the possibility of that wing being at or near stall would be likely which would increase the roll rate in that direction. Any increase in airspeed would at least slow the roll in the direction of the failed side assuming the yoke was turned fully in the opposite direction.

You may recall the famous crash of American 191 in 1979 with the erie photo in the Chicago Tribune just before the DC10 impacted the ground with the aircraft in excess of a 90 degree bank after an engine departed a wing on take off. It is my understanding that when the engine departed the wing it took hydraulic lines with it causing the leading edge flaps (slats) to retract obviously causing an aerodynamic imbalance. The initial rolling motion that followed was corrected by the flight crew as the airspeed was approximately 20 knots past V2. If my memory serves, the crew recognizing they had an "engine failure" followed procedure and allowed the aircraft to slow slightly to V2 which was the speed they were to fly in the event of loss of power on an engine. This slowing caused the one wing to stall and the unrecoverable roll followed. When the NTSB put flight crews in the simulator replicating the event, they were instructed to maintain the V2 plus 20 airspeed and every crew flew away to a successful outcome.

[Ernie Martin]

Good input. Another reason, if there is plenty of runway length, to be higher and faster than minimums on final. Altitude and speed are your friends in the flap scenario. But as Jim Stack and "Tropical" suggest, the better choice is to make sure your flap cables are inspected regularly so you never face this emergency.

Ernie

[Roger]

Thanks for the response that the flap would reset to "0" if the cable breaks. As for the pithy comments about maintentance, and it never happening if, blah.. blah... blah... You have got to be kidding me?

I guess based on the assurance that good maintentace is all I have to concern myself with, I will add a little useful load by throwing my Emergency POH overboard.

tks/Roger

[tropical]

Originally Posted by Roger

Thanks for the response that the flap would reset to "0" if the cable breaks. As for the pithy comments about maintentance, and it never happening if, blah.. blah... blah... You have got to be kidding me?

I guess based on the assurance that good maintentace is all I have to concern myself with, I will add a little useful load by throwing my Emergency POH overboard.

tks/Roger

No, I'm not kidding anyone. You can invent emergency procedures for everything.

Typically flaps aren't used at altitude but close to the ground. If your flaps go asymmetric at 50 feet on landing I doubt seriously anyone will have quick enough reactions to overcome the control forces.

Part of safe and proficient flying is having everything in order, both the pilot and the airplane. If the flaps are suspect have a mechanic go through the system and do a very thorough inspection. Unfortunately in general aviation most owners wait for something to break before considering fixing it because they feel preventative maintenance is too costly. If you observe operators that fly airplanes commercially and do all the maintenance their failure rates are alot less because they find the problems before they become an in flight emergency, not always but a much better record.

[Paul462]

If memory serves, there was quite a comprehensive broken flap cable thread on this message board 6 or 7 years ago after the Australian failure. I believe that one occured on short final, a few hundred feet up, and the pilot reported he applied full power and retracted the asymetrically extended flap. It goes without saying he was probably applying full ailerons and coordinated rudder against the roll... :-)

Unfortunately, it is not possible to visually or "rag" inspect the flap cables in place, or even removed from the aircraft, because the heart strand or an internal strand may be failing, and that would not be visible externally, even with the cable removed. Also, the most common failure point is flush against a quadrant pulley, not easily inspectable.

There are FBOs who are willing to take your money for a "visual" inspection - Turbo Air in Boise Idaho did from me back in 2003 when I bought my first 1968 T337C, as part of a $7,000 annual! They called it a "visual" and "rag" inspection - you drag a rag along the cable and see if it snags anywhere, and "visually" inspect where you can't reach with the rag. This inspection was at least partly ineffectual, because it only inspected external strands, not (possibly) failing internal strands nor the heart strand.

I took a different approach with my second T337C, acquired 2 years ago with just under 3,000 hrs. TTAF: we removed the 4 flap cables which hold down the flaps and replaced them. It wasn't that awful bad a job (10 - 12 hours?), and the IA made up new cables on the spot with new terminals and cable, using a huge swedger he dragged over. I understand there's an operation in New Zealand which does same every 500-1,000 hours or so, as preventive maintenance.

[edasmus]

Thanks for this info Paul! Much appreciated!

Ed

[birddog]

Does anyone know the history on when the factory went to stainless steel cables and have any of the accidents involved stainless steel cables? I understand later production aircraft were all manufactured using the stainless steal. I have heard one report that none of the flap failures involved the stainless steal equiped aircraft. This is a significant observation if true. The source did not give permission to use his name but it's a very reliable source in the 336/337 aircraft operations. OK I like cooberation. I think thats the right word.
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Weed vaporizer