CTOT and Autocoarsen
07-23-2008 | 06:03 AM
#11
Gets Weekends Off
Joined: Sep 2005
Posts: 586
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From: Lots and Lots of Days Off
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.
07-23-2008 | 06:24 AM
#12
Line Holder
Joined: Sep 2007
Posts: 67
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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?
07-23-2008 | 06:42 AM
#13
Line Holder
Joined: Sep 2007
Posts: 75
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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
IM
07-23-2008 | 07:27 AM
#14
Line Holder
Joined: Jan 2008
Posts: 39
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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.
07-23-2008 | 10:16 AM
#15
ULTP-Ultra Low Tier Pilot
Joined: Dec 2007
Posts: 3,228
Likes: 0
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.
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.
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%.
