IFSD at takeoff (turbo-prop)

[1jz]

If a turbo-prop airplane's engine stalls at takeoff n to recover the Power Lever has to be reduced to FI n hence that increases the drag then, is engine shutdown advisable to reduce drag.

Any documents / references / crash reports. Will appreciate.

[Dash8driver1312]

You mean engine surge. Turbojets (fans/props/shafts) don't stall.

First, fly the aircraft. Then, what are the indications? High torque and low rpm? High rpm and low torque? Low torque and low rpm? Best refer to your training anyway...

[1jz]

Thanks. But, unfortunately world isn't perfect they do surge n if turboprop surges then one has to retard the Power lever, if done at take off (if) to save the engine, then blade angle of the prop goes into a fine pitch angle causing alot of drag. Still waiting for more inputs.

[lomapaseo]

Don't do anything that impacts controllability at low speed. Take your time sorting out the engine. Work the drag issue first.

Of course I never seem to understand the question on the first go so a few more descriptions might help.

most of the problems I'm familiar with involved the PF not recognizing or taking action to mitigate the drag.

I'm sure they covered this in training :confused:

[Intruder]

I'm sure the exact procedures also depend on the airplane and engine type...

[dixi188]

Most Turbo-Prop aircraft have an Auto Feather system that will feather the prop if torque falls below a certain figure with the power lever at Take-Off position. No need for pilot action, the prop will be feathered and engine will be shut down.

At least that's how I remember it for RR Dart, Allison 501 and Garrett 331.
PT6 might be a bit different as the prop is driven by a free turbine so the gas generator would still run.

[JammedStab]

I have flown PT-6 aircraft with and without autofeather installations. I have
also flown Allison 501 engines without autofeather. So in this case, you are on your own with no feathering help.

Perhaps it is PIC decision but at such a critical moment if you have low speed and high drag(you stated stalls in the first post), I would suggest that feathering immediately is the best option unless you can be sure that your performance is so good(very light weight and low density altitude) that you can climb reasonably well with all the extra drag.

[1jz]

JammedStab .... That's what I was talking about, I m well versed with the type of airplane I m flying, atr. N also the auto-feathering system won't feather the engine for surges etc. If u have any documents supporting pilot actions to feather the engine then do share. Thanks alot

[MarkJJ]

There are normally systems working to prevent this on most turbo props, bleed air is taken away to ensure smooth airflow through the various stages of compression. Auto feather or auto coarse is with reduced torque as stated.

There is a system called a compressor bleed value on the PT 6-67s, it takes away excess compressed air at low N1 and reduces the back pressure on the axial stages thus reducing the likely hood of a compressor stall.

In the event of a compressor stall on turbo props, I've not heard of any, though I believe the remedy is the same as with a fan. Reduce power to idle and then reapply.

Yes you will increase drag for a time, and there will need to be a quick trade off in terms of what your are doing with your energy at that point. But the smooth airflow should return fairly smartly, hopefully with no damage to your motors.

Really to shut down the engine would not be 1st course of action, especially just after V1 unless there is a fire or the compressor stall has caused bits to start flying out of the engine. Indications of a compress stall in the cockpit will be a reduced N1 and rise in ITT which is not a cause for a shut down immediately I'd say. Perhaps later on, but try the remedy first, why not read what your PFM or AFM states.

[GearDownThreeGreen]

I know of at least one incident with a CT-7 where the engine completely surged on departure, the ITT rose to well above 1200°C, and was left unattended for quite some time.
I believe most of the central engine components were a write off after the incident. So the phenomena can definitely occur on TP engines as well.

[A Squared]

I don't know how the ATR powerplant works, but on the turboprop engine I'm most familiar with, if you have a loss of engine power, pulling the throttle back to flight idle will have no effect on prop pitch, and thus no effect on drag.

If you've lost engine torque, and the prop hasn't been feathered by an auto-feather system, in most cases the prop will *already* have been driven to the low pitch stops by the governor in an effort to maintain prop RPM. At that point pulling the throttle lever back won't change the prop setting.

Does the ATR powerplant do something substantially different than this?

[GearDownThreeGreen]

Can't say anything for the ATR, however, most engines are still producing some power in these cases, so reducing the PL will most likely give you finer pitch, but still positive thrust.

If the engine has failed without autofeather, then it will normally stay at pretty much the current pitch balanced by PCU oil pressure and flyweights. In the latter case PL position is irrelevant.

I would deselect autofeather if selected, reduce the power, and then carefully reapply it to see if the situation has been corrected. If not, then shutdown.

[A Squared]

Can't say anything for the ATR, however, most engines are still producing some power in these cases, so reducing the PL will most likely give you finer pitch, but still positive thrust.

OK, I'm not really clear on what sort of event the OP is referring to, but if the engine is still producing some power, then I suppose at some point reducing the power lever will create some drag.

It you're right at takeoff and the engine is producing some power we train to not take action until established in a climb. Of course we have he luxury of a flight engineer who can tell us whether the engine is making useful power while we're busy flying the airplane.

[Intruder]

If the QRH/FCOM allow it, and setting the power to near 0 torque (no thrust, but no drag) makes the surges go away, I'd likely keep it there while still at low altitude. Worry about feathering and shutting down after you have some altitude.

[Mach E Avelli]

Depending on the engine, but those that I am familiar with all inhibit the autofeather circuit to both engines if either power lever is reduced below a certain setting. In the case of surging or compressor stall, in the absence of any other immediate memory drill, I would only reduce power on the affected engine to somewhere below the autofeather inhibit, but not so far as to allow the prop to windmill. This means at least some useful torque is available, but the engine has been offloaded somewhat. With less fuel going in, less chance of damage. The airflow is not something you can do anything to improve on take-off anyway. A windmilling prop at low speed is a far more dangerous beast than a rough running engine!
If the engine did subsequently fail, the two ways to deal with it could be to either simply advance the power lever above the inhibit setting and let the autofeather do its job, or call for a manual feather. Obviously, the latter being the preferred option if the engine is overtemping.

[1jz]

Thanks guys for such useful inputs.. Actually what I meant was, if engine surges / stalls with a lot of over-temp n bangs ( which are a possibility in ATR engines -pw127e, besides even having HANDLING BLEED VALVE -to cater for extra air for surging ). N the power lever setting at which things go normal is at flight idle setting-that increases drag. So just after take-off is it advisable to feather the engine to avoid drag n sort out the issue at higher altitude?

[Australopithecus]

What negative torque protection does that powerplant have? Surely retarding the power lever to flight idle will not cause the prop blade angle to reduce to the beta range?

If an engine will only run at idle there isn't much point in keeping it running except perhaps for electrical and hydraulic power.

Single engine flight is simple and well trained, whereas one-and-a-fraction engined flight can get complex.

[Intruder]

Actually what I meant was, if engine surges / stalls with a lot of over-temp n bangs ( which are a possibility in ATR engines -pw127e, besides even having HANDLING BLEED VALVE -to cater for extra air for surging ). N the power lever setting at which things go normal is at flight idle setting-that increases drag. So just after take-off is it advisable to feather the engine to avoid drag n sort out the issue at higher altitude?
Your QRH or FCOM certainly has procedures for that dramatic an event. What does it say?!?

[Mach E Avelli]

Negative torque protection is usually only provided if the pilot does not retard the power lever. If the power lever is retarded to flight idle, most props will go to a high drag state - not beta or reverse, but still enough to cause control problems at low speed. At a critical time immediately after V1, if the engine bangs, surges, farts or explodes into a thousand pieces, locking out the autofeather by closing the power lever all the way to flight idle at low altitude is a bad idea.
The entire takeoff performance is predicated on the autofeather taking care of any failure at or soon after V1.
Autofeather systems are extremely reliable, so much so that some operators no longer require pilots to conduct manual feather drills immediately after takeoff.

The history books are littered with accidents caused by pilots losing control due to windmilling props.

Unless your Company specifically preaches another doctrine or the FCOM clearly states something to the contrary, for engine malfunctions after take-off, I would not be retarding to flight idle below 400 feet or below V2 plus 10 knots.

[Dufo]

We had a nasty compressor stall after hitting a flock on birds just after liftoff. CT7. It popped and banged but didn't flame out or feather, so after required actions we tried to increase power but couldn't get above 40% trq, above that it would start to surge. We left it running until landing as no other abnormalities were observed.

[A Squared]

Negative torque protection is usually only provided if the pilot does not retard the power lever. If the power lever is retarded to flight idle, most props will go to a high drag state - not beta or reverse, but still enough to cause control problems at low speed.

I have no idea how the ATR powerplant handles this, but this is not true for the Allison 501 installation in the L382. Negative torque protection is a mechanical system which is active through the entire flight range of throttle position. You have to move the throttles over the gate into the Beta range before the linkage in the NTS system is cammed out. If you pull the throttles all the way back to flight idle, (like when you're a little high on descent and trying to make a crossing restriction ... or so I've heard ;) ) you will definately get NTS-ing, and should in a prperly rigged powerplant. In fact this is one of the things which is checked on a functional check flight.

My understanding is that the Metro powerplants are the same way, that you'll get NTS-ing if you pull the throttles back to Flight Idle. I would take that as an indication that some (but not necessarily all ) Garrett installations are similar.

[Mach E Avelli]

The Convair 580 also runs an Allison. Because the aircraft is not supported by a proper simulator, we only got to pretend we were asymmetric in the real aircraft and at low training weights. We never got to explore the NTS range - in fact we never got below 400 hp because apparently there was a risk of the drive decoupling if the prop got into a range where it was 'driving' the engine.
During the flare, if the power was pulled off too quickly it sure felt like a lot of prop drag was affecting things. The aeroplane would fall to earth like a ton of bricks,as I found to my great embarrassment one day when I had a Boeing flashback and pulled it to flight idle at about 30 feet. Quite the worst landing I have ever done in a transport aeroplane!
Some Garrett aircraft appear to behave the same way. I vaguely recall that a Metro crashed on final approach somewhere in Australia due to either the NTS not working or somehow being over ridden. More recently we lost a Brasilia during a training exercise where it appears that the windmilling prop contributed to a loss of control on takeoff.

All the RR Dart setups will go to the flight fine pitch stops at low power lever angles and they also have a minimum torque limitation in flight to protect the reduction gears .

So, I dunno, but I think most prop installations end up producing drag with power lever(s) deliberately set to flight idle, otherwise how do we get the aircraft to achieve its advertised landing performance?. Obviously from the post above, there are some aircraft where that is not the case. Maybe the aerodynamic experts can wade in with a more erudite explanation.

[A Squared]

I guess I should clarify that I didn't mean to say that it doesn't produce drag at flight idle. It does, but the NTS is operating in that range.

[bucks_raj]

The ATR would possibly do nothing.

The ATPCS (Automatic Takeoff Power Configuration System) Is active Untill

TQ (approx) 48%+
Power Leaver Angl (approx) 48* +
values aprox but very close.

ATPCS recognizes an Engine failure by Monitoring TQ less than 18% (For any damn reason )
It will give full power on the other engine and feather the failed engine.

In the case of Surge at Tk Off Loss of power would be evident , whether the ATPCS works or not Aviate Aviate Aviate.

Compensate loss of power Ramp the live engine, follow the E Out profile