IFSD at takeoff (turbo-prop)

[A Squared]

Originally Posted by 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.

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