Skymaster down!

[hharney]

Has anyone else seen this news? I just had a google alert that sent this link. The writer of the article is pretty green about flying and aircraft.


http://www.stillwater-newspress.com/...086184217.html

[hharney]

http://www.wausaudailyherald.com/art...304080071/1981

[Ernie Martin]

This series of 2 Skymasters down within days should be of grave concern. In both instances the pilots were highly experienced (one flew for Northwest Airlines and had 30,000 hours, and the other had been a commercial pilot and flight instructor) and in one case the aircraft was state-owned and flying for a state agency (which suggests a more rigorous environment of maintenance and pre-flight checkout). And people, these were lightly loaded twin-engine Skymasters. I can see an overloaded Skymaster losing an engine at takeoff crashing, but these aircraft had a single passenger. And in the case of the state airplane witnesses saw the plane circling the fire area and then “it went straight down”.

Fuel exhaustion might explain one but not the one that "went straight down". We need to stay on top of these to find out what happened. I'm hoping a snapped flap cable (the subject of another message this morning) didn't play a part, since the aircraft that "went straight down" was not landing.

Ernie

[Frank Benvin]

In the second crash the plane was circling the fire and came straight down. Might have stalled it in a turn?? Whatching the fire and not paying attention to airspeed. I lost my best friend in a Yak 52 He was and instuctor and his passenger was a ex mig 29 pilot They stalled at 1200 ft in a turn and didn't have enough atlitude to recover

[Skymaster337B]

Stalls at low altitude are the most common cause of VFR accidents. However, flying around a fire may cause a different problem. The density alitude over a fire is insanely high...because of the temperatures. This might have agrivated a non stall condition into a stalled condition. Either way, flying around a fire isn't the smartest thing to do with an airplane.

[Roger]

As long as the Flap Cable question has come up, as related to these potential accidents, I would like to ask the following question to those pilots/mechanics who are familiar with the whole flap system in the 337, as follows: If a flap cable breaks, is the "other flap" usable? I.e can it be set to correspond to the "broken cable position" of the jammed flap? Granted you wouldn't have a lot of time, but if we knew the answer, we could perhaps develop a "rule of thumb" protocol.

I seem to recall on my Navajo, that if one side went, you were essentially screwed. Is this the same on our Skytrucks?

[Ernie Martin]

OK, here goes my understanding of the issue and how to recover. A caveat: I could be wrong and I hope others jump in here and set me straight.

When a flap cable breaks, the flap on that side snaps instantly to neutral (zero degrees). The other side remains where you set it, and the imbalance causes the aircraft to roll aggressively, especially at full flaps. The solution: with the left hand instantly apply opposite aileron (to arrest the roll) and with the right hand flip the flap handle back to zero (so the non-broken flap goes to neutral like the broken one). Bringing the flaps to neutral is critical, because for some flap settings (certainly above 2/3 and perhaps even at 1/3) there isn't sufficient aileron authority to overcome an unbalanced flap condition.

At least one pilot, on short final and with flaps deployed, was able to recover from this failure, in what was decribed as a masterful job of piloting.

On approach, part of my checklist is a reminder of what to do if a flap breaks and after setting flaps I try to keep my right hand close to the flap handle.

Ernie

[tropical]

Aircraft accidents aren't caused by one problem. There are a chain of events that lead up to the accident. Each link in the chain can be small, almost unnoticeable. If you can break one link in the chain good chances are you can avoid the accident.

High time and lots of experience mean nothing if the very basics are ignored or forgotten. "What? Me?, Ha, that can't happen! I'm highly experienced!"

Lots of those guys in graveyards.

[Ernie Martin]

I was hoping to get a response to my cause/recovery above, in part because I'd like to know for sure. Anyone who knows, one way or the other, please comment.

Ernie

[tropical]

Originally Posted by Ernie Martin

I was hoping to get a response to my cause/recovery above, in part because I'd like to know for sure. Anyone who knows, one way or the other, please comment.

Ernie

The best response is have the maintenance done correctly and it doesn't become an issue ( I assume we're still talking flap cables).

[stackj]

Ernie,

The Coast Guard (and it's Auxiliary) uses a model called Swiss Cheese to say the same thing. The example uses slices of cheese to represent occurances during a flight. If the holes in the successive slices line up, there is a corridor to an accident or incident. Any one slice being repositioned can block the corridor thereby preventing the accident.

The key is to recognize a building situation and take action to prevent it's progress.

[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