Turboprop control

[brettt777]

At work (International Jets, KGAD) we are getting a couple of Shorts 312 Tucanos sent to us for repair and then I will install a complete glass avionics package. The planes have the Garrett TPE331 turboprop in them. I am wondering about these engines. How do turboprop controls differ from recip controls? A recip has three controls, how many does a turboprop have and how are the used? When flying, do you keep the torque at one setting and then adjust your power with the prop pitch or is it the other way around? What about when you taxi?

[C]

The Garrett engined Tucanos (Shorts built) have a single throttle lever to control the engine in flight. The fuel and the prop sort themselves out according to the engine mode, the pilot just has to decide whether to go faster or slower! The engine governs itself automatically, although there is a switch for a manual mode for emergency use.

In an emergency, there is a separate lever somewhere down by the left buttock of the pilot (both cockpits), which is the emergency shut down lever (fuel cut off and prop feather).

On the ground, there is a switch which selects a ground mode of, IIRC, 70% engine RPM (in flight mode the engine runs at 100% RPM continuously and power is controlled by aforementioned fuel/prop pitch combo).

Hope this helps.

If you're unfortunate to fly an anciently controlled PT6 engined aeroplanes, such as the King Air, you get 3 levers for each engine to clutter the cockpit.

[Brian Z]

I just recently read a forum thread elsewhere talking about this, someone chimed in with a LOT of technical talk, especially about the PT6 engine specifically.  In a reciprocating engine, the throttle controls fuel flow. For a turboprop, the power lever (he was emphatic that it's NOT a throttle!) makes a lot of things happen in the background so that higher power lever setting equals more thrust, but it's a lot more complicated than just more fuel going into the engine.

[C]

For a turboprop, the power lever (he was emphatic that it's NOT a throttle!) makes a lot of things happen in the background so that higher power lever setting equals more thrust, but it's a lot more complicated than just more fuel going into the engine.

I all rather depends which engine it is and who's designed the aeroplane.

For the Shorts Tucano, it certainly is the case. Earlier/legacy designs, such as the King Air followed the adage that if it's got props, you have to have 3 levers for each engine. Flying the Tucano, with its single throttle/power lever, I was bewildered how backward it was flying the B200 with throttle/power levers controlling torque, prop levers for rpm, and then even though there were only 3 (IIRC) setting on them, full size "mixture" levers controlling fuel/cut off.

It was like being back in 1944.

[expat]

For a turboprop, the power lever (he was emphatic that it's NOT a throttle!) makes a lot of things happen in the background so that higher power lever setting equals more thrust, but it's a lot more complicated than just more fuel going into the engine.

I all rather depends which engine it is and who's designed the aeroplane.

For the Shorts Tucano, it certainly is the case. Earlier/legacy designs, such as the King Air followed the adage that if it's got props, you have to have 3 levers for each engine.

Legacy still hangs about. For example the ATR XX-500 series still has condition levers, however they have no function other than to make the pilot feel at home so there is no cross aircraft confusion when flying a no -500 series (I think they are now onto 600 now too) The crew still manipulate them, but they have no input. The Dash 8 Q400 is the same, but is somewhere between the two. It is quite a time since the last time I did a run up on the Q, so I would have to do a bit of reading before I do it again.....

Matt

[Ivan]

If you want to see how a single-lever turboprop works, download the latest An-24 package

Basically you have just two controls: a pitch limiter and 'throttle'
You start in ground pitch, if you deactivate the limiter the pitch will go to flight mode, and the plante starts to move.
In flight you fly by a parameter called TLAI (Thrust lever angle indicator), which is displayed in percentages.

Depending on the engine type there is a non-indicated range where you aren't accelerating anymore (usually around 40% and lower), but you have NO reverse (that is done by the pitch limiter)

All the real adjustments in pitch and throttle are done in the engine by hydraulics