Dead Foot, Dead Engine? ...maybe
- Thread starter Captain
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Except that would be incorrect in this instance as well as the failed engine was producing excess thrust.
Captain
Final Approach
Did you read my OP? The nose moved left and I lost the right engine. Sorta the point.
Cpt_Kirk
En-Route
Right. I understand that and as Henning said earlier, your situation was atypical.
My post was not directed towards your specific situation.
Ted
The pilot formerly known as Twin Engine Ted
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iFlyNothing
I learned the same thing when I started flying the Commander 690 - possibility exists for a runaway engine somehow. Really the only time when you worry about needing an immediate/instant response to an engine failure is right after takeoff. Once you have a bit of altitude (and especially at FL270) no reason to be in a hurry.
Nicely done, Captain. Thanks for sharing the story and the failure mode. Illustrates that you can have an engine that's just fine, but other items can still make your day bad. The benefit of two...
Nicely done, Captain. Thanks for sharing the story and the failure mode. Illustrates that you can have an engine that's just fine, but other items can still make your day bad. The benefit of two...
That was his point, you always should stop a moment and assess the situation before acting. Unless you are low and on takeoff, you really are under no great press of time to get an engine caged, take the few seconds to look things over and assess them for information before you act because things may not be what they appear.
If he would have acted on the nose swing, he would have one engine shutting down about the same time the other twisted off the wing.
PaulS
Touchdown! Greaser!
I doubt it would have twisted off the wing, not from over torque anyway, ( would think the gear box would fail first) catastrophic failure may have caused some issues which probably would have happened sooner than later. I'm more disturbed from the damage that was caused by the engine feathering, seems like that should never happen and maybe some design changes are in order by P and W..
Glad you are ok cap...
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Gucci Pilot
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Pretty standard for most planes equipped with yaw dampers to have them disengaged during single engine ops.
RotorAndWing
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Nothing I've ever flown requires the yaw dampers to be turned off in single engine or engine out ops.
It already broke the engine mounts.
PaulS
Touchdown! Greaser!
I thought captain had said it was from the engine feathering but it was another poster. I guess we don't know, but feathering seems like a more likely scenario to me, a sudden deceleration from an over torque condition. I would think that the mounts have a large safety factor built in as they could experience forces well beyond 100 % torque in normal use by dynamic forces from external influences.
The mounts were already breaking away from the feather, so obviously the level of over engineering is not as significant as you may believe. Weight is the key factor in all these designs. When part of an engineered structural assembly like this turns loose, typically the component failures cascade.
Ted
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Engine mounts are tough, but you are correct that there is a weight factor. The mounts are required to withstand certain loads and testing. No more is needed for cert.
Gucci Pilot
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Nothing I've ever flown requires the yaw dampers to be turned off in single engine or engine out ops.
Beechjet I flew had to have it off for a single engine landing. The rudder boost(pretty much the same system but technically not connected) would take over in an engine failure. Pretty sure the C-21/Lear 35 has to as well.
Or on the DC10, if your center engine fails you have no dead foot.
Does a failed #2 on a DC10 cause a pitch change?
#2 failure is the easiest one of them all
Not really much of a pitch change. Nothing you would really notice in the heat of the moment. Only had it happen in the sim and didn't notice it. #2 inadvertent thrust reverser deploying is a different story.
I had mentioned that it would be most difficult to over torque at that altitude if the prop was spinning at anything resembling a cruise RPM. Most PT6's are temped well before that altitude is reached. It would have taken some kind of a feathering event to cause that.
Being totally unfamiliar with how the linkage differs on the P180 compared to more traditional set ups I hope Captain at one point will share how "they" think it happened. He did mention that the linkage in question somehow was related to the beta rod. Let us know what you fine out Capt.
PaulS
Touchdown! Greaser!
I didn't say it was overengineered, I said I would think something else would fail before the mounts were damaged by the engine developing too much power. You have to remember that this is a dynamic environment. The AC is in motion through what could be very turbulent air, and turbulance could happen at takeoff or initial climb when maximum power is made subjecting the mounts to much greater forces than the engine could develop alone, even in an over powered situation. My theory ( as first mentioned by Ron) is maybe the props went from developing too much power to the feather condition too quickly causing much greater than normal or anticipated forces on the engine, damaging the mounts. Generally, I am guessing that props that get feathered are not producing power before they are feathered. It sounds to me like the prop went from producing too much power to no power quickly and that could be what caused the damage.
I'd be curious as to what Captain thinks as far how much power the engine was producing. Could it have been more than takeoff power???
kgruber
Final Approach
If it were flat rated, yes. But probably not at FL270
It was still producing power in feathered position thus the over torque. When Capt said over torque I assume he means too much torque for that altitude. I do not know how Capt runs his engines. One popular way is to once temped out just keep the hottest engine 50 deg below redline and match torque. If one engine started producing more torque the temperature rise would be immediate. Again, assuming with the linkage set up on the P180 and the relationship between the beta rod and the failed linkage it would appear going into or towards feather is what run the torque to or above redline. This would have minimal effect on PT blade temperature since the compressor section would still be hauling a$$. I still do not think the engine will get anywhere near max allowable torque at that altitude with out a prop feather incident. JMO.
Anxious to hear the outcome, including damage.
Anxious to hear the outcome, including damage.
PaulS
Touchdown! Greaser!
So pulling the condition lever back the detent is probably what caused the damage....... I think you are correct. The engine was producing too much power for the conditions, and was still producing power until the lever hit the detent which cut off fuel flow. At that point the prop feathered, effectively slamming on the brakes for the 500 or so pounds of mass spinning at very fast speeds overloading the mounts. Makes sense to me, it will be interesting to see what the experts say.
It seems more like the part let go which is what allowed it to go to feather while still making power.
kgruber
Final Approach
Probably the firewall shutoff valve would have been a better option.
Is engine "runaway" overtorquing on the emergency checklist?
Is engine "runaway" overtorquing on the emergency checklist?
Captain
Final Approach
I would go with this.
When the linkage let loose the torque went up. At first I assumed it was the FCU delivering too much power causing the over torque. Now that I've seen where it broke and how the failed part is directly connected to the beta rod my theory is the failure caused the blades to partially feather while the engine was still powered causing the over torque and my yaw to the left.
If they had fully feathered there wouldn't have been yaw. The moment the mount was broke will never be known...when the linkage broke or when I pulled the condition levers back. Don't know and I suppose it doesn't really matter. I'd guess it was when the linkage broke though.
You know, the engine mount breaking is potentially the causal factor in breaking the linkage if it put it in a bind. I'd have to see the mount breaks to tell.
Did you look at the broken mount? Did all the breaks show torsional damage?
Captain
Final Approach
I don't know. It looked like a black rubber block with cracks in it. Beyond my pay grade and experience to diagnose.
No, I agree with Captain and is what I said originally. The prop was going into at least a partial feather which spiked the torque and did the damage. Once the fuel was shut off it was all over. Once fuel is removed you can go into feather as fast as you want. An auto feather system will be at full feather in a couple of seconds from loss of power. Captain's fast reaction may have saved the PT blades in that eventually it would have heated up due to the stopping the PT blade section with the gear box.
About the only way to over torque at that kind of altitude (without a tremendous peak in turbine temp) is to some how stop the propeller from turning (or slow it way down).
Hoping the gear box is OK, Captain.
No, I agree with Captain and is what I said originally. The prop was going into at least a partial feather which spiked the torque and did the damage. Once the fuel was shut off it was all over. Once fuel is removed you can go into feather as fast as you want. An auto feather system will be at full feather in a couple of seconds from loss of power. Captain's fast reaction may have saved the PT blades in that eventually it would have heated up due to the stopping the PT blade section with the gear box.
About the only way to over torque at that kind of altitude (without a tremendous peak in turbine temp) is to some how stop the propeller from turning (or slow it way down).
Hoping the gear box is OK, Captain.
I would hope the engine is declared a total and gets replaced.
Not likely IMO. I think the gear box may be toast. Capt said temp did not go up. Power section may be fine. If that engine was considered totaled, well let's just say it will be tough. We had two -61's overhauled. They were running perfect. $775,000. That was after a week of intense negotiation. Let's hope it is just a gear box and three new mounts.
kgruber
Final Approach
I'd suspect firewall damage.
From what Captain described, it sounds like The Lord Mounts took the damage, as they should.
Just remember guys....
This is a pusher airplane, not a tractor. So the mount is actually in compression, not tension....
All kind of strange things can happen, but my guess is gyroscopic forces from the prop did more damage then the thrust factor did... IMHO...
I would LOVE to see pics of the damaged mount...
..
PS...
GREAT job captain.....
This is a pusher airplane, not a tractor. So the mount is actually in compression, not tension....
All kind of strange things can happen, but my guess is gyroscopic forces from the prop did more damage then the thrust factor did... IMHO...
I would LOVE to see pics of the damaged mount...
..PS...
GREAT job captain.....