Airline Pilot Central Forums - CTOT and Autocoarsen

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Quote:

Originally Posted by The Juice (Post 431298)

If the CTOT is set to 90% and the PL are pushed to 92% when you activate CTOT it will not lower to 90% so how can you get an increase in torque when you dial down the CTOT?

If done correctly, you cannot.

Here is what sometimes happens:

Say you are going to set 92% on the CTOT control panel. The PF advances the power levers to say 85% instead of somewhere in the 77-82%. The CTOT switch is moved to APR and you see 92% on the guages. Perfect, well, about 100 knots or so or even during acceleration after climb, the torque has actually bloomed to 95% (based on where the power levers are set). Some pilots do not notice this during the takeoff roll or initial climb so when they do dial down the CTOT, they are left with the 95%.

Ideally, and you will get there with practice, when you dial down the CTOT after takeoff, you will not have to move the power levers and the Torque will remain constant.

I was always under the impression that the autocoarsen system was in place for operators of the Dowty-Rotol propellers and that those aircraft with Hamilton-Standard props (AE's birds, I was told) actually went to complete feather. I only flew the Dowtys. Any Ham-Standard operators care to clarify?

It has been a looong time since I was in the Saab. But if you forgot to turn off the CTOT and pulled the PL back to start down, didn't the power really drop off once out of CTOT range? Or am I mixing up another airplane?
IM

Quote:

Originally Posted by Invisible Man (Post 431436)

Yes -- the power has to be dialed down prior to switching CTOT off to avoid the danger of a compresser stall. I actually had a First Officer one time not switch the CTOT completely off, he just turned off the APR, so there was no indication in the cockpit (the status lights only come on in APR mode) the CTOT was still engaged, it made for an interesting approach, the torque would jump from 40% to 60% every time I hit the 64 degree switch until I figured out what happened.

Quote:

Originally Posted by RJ85FO (Post 431413)

Ok, I misunderstood your original post. I though you meant the Torque would baloon up when dialing down the CTOT. Kind of like how the power drops like a rock when someone pulls back the PL's without dialing down the CTOT first and you get that huge dropoff when they see what they have been doing.

What you speak of I see all the time. CTOT set to 90%, PL advanced and APR/CTOT set. On climbout you look down and Torgue is at 98%.