Reduced power takeoffs in an ATR?

[Brasilia Pup]

I thought the ATR was already at Reduced Torque. It sure flew slowly enough to feel like that. Kinda like the Brasilia was fuel critical the moment you pushed out of the gate.

 

[unwashed]

I did assumed temp TO with a Dash 8 100/200/400 all the time. I do them all the time now in a Jet. Not a big deal. Are they safe, hell yea they are. It saves the engines for when you might need them most, on a real emergence, not just taking off day to day.

 

[dwcaviator]

Assumed temperature is exactly what I was getting at. Interesting that the min flex was 80%. The performance tables I'm looking at would make as low as 75% possible, but I like that margin. Any current ATR operators out there do it?

 

[unwashed]

25% reduction is the maximum allowable under the FAA.

 

[BobbyBiplane]

The issue with ATRs at lower than 80% is that at certain atmospheric condiitions it is possible to have the assumed temp minimum power point at a PL angle where the ATPCS does not arm invaledating the entire process.

Bob

 

[dwcaviator]

Good info on the ATPCS arming. Unwashed, I'm not familiar with the Dash 8's takeoff procedures. Does the good engine automatically uptrim in the event of an engine failure on takeoff? Also, are you able to tell me which company did the procedure with the Dash? Finally, can anybody name an ATR operator that does/did assumed higher temperature takeoffs?

 

[BobbyBiplane]

Good info on the ATPCS arming. Unwashed, I'm not familiar with the Dash 8's takeoff procedures. Does the good engine automatically uptrim in the event of an engine failure on takeoff? Also, are you able to tell me which company did the procedure with the Dash? Finally, can anybody name an ATR operator that does/did assumed higher temperature takeoffs?

PM me sometime. I will link you up with the guy from Pan Am. I know of no one in the US currently using this procedure.

Bob

 

[unwashed]

Good info on the ATPCS arming. Unwashed, I'm not familiar with the Dash 8's takeoff procedures. Does the good engine automatically uptrim (yes it will uptrim 10% on the operating engine, ie if you derate from 100% to 90% the uptrim value will be 99%.) in the event of an engine failure on takeoff? Also, are you able to tell me which company did the procedure with the Dash? (QX) Finally, can anybody name an ATR operator that does/did assumed higher temperature takeoffs?

I don't know anything about the ATR, but they do operate PW's so I assume it is possible to derate like the Dash.

 

[Headfake14]

I know ASA did NOT do anything like that. We/They...I'm no longer there...had 12 ATR-72-212s and 7...ah sh!t, can't remember the "dash" for the other model...it was a predecessor to the -500 with the auto condition lever notch design.

Anyway, both models had the notch for the PLs. We NEVER took off without a PL out of the notch...except of course for a busted EEC.

I can't imagine wanting to reduce further anyway...they thing was a pig unless you were empty and it was winter. I still miss it.

 

[CutEmUp]

PDT does reduced power takeoffs in the Dash8-100 (not the 300). And the power does uptrim 10% with an engine failure.

Normal take off power is 90% with a normal ITT of 785. When temperatures get above ~30C (depending on press alt.) the normal torque for takeoff is decreased to keep the normal ITT from exceeding 785 (not to be confusing, but this is not the "reduced power" part) This torque is published in the performance data on the release and is not contingent on anything but OAT and pressure alt.

Now for the reduced power part. An assumed temperature (higher than ambient) can be used to reduce the power further (no lower than 80%). Say the OAT is 25C, the Assumed temperature may be 42C which will give a reduced power setting of ~80%. Depending on runway length, or climb requirements there may be a limit to how much you can reduce the torque based on takeoff weight. Again, this is all published on the performance numbers in the release.

I always thought that reduced power was used to keep ITTs lower to save on engine wear. Instead of 785C on takeoff you would see maybe 725. When it gets cold out, PDT can do a reduced power takeoff almost everytime. The ITT (when cold) may go from 685 normal down to 650 reduced. Which doesn't seem to save anything since on climbout the power is pushed back up to 90% until 730 ITT can be maintained in the climb.