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Well-known member
Mar 27, 2002

I'm a CSA/ramp agent for Chicago Express and a student pilot. We fly SAAB 340B aircraft, and often they are dispatched with DETRO on the release. Can someone try to explain what this is? I asked a Captain today and he said it's a limitation that doesn't allow the engines to produce full power. He mentioned temperature has some effect and how maintenance take an engine off DETRO when it goes through maintenance. I'd like some more detail or places to start looking. I already tried searching the forums.


Are you talking about engines that are on a derivative power program?
The engines are certified to produce their maximum available shaft horse power at sea level up to 35 degrees C without exceding the maximum takeoff inter-turbine temperatures. When the engines can no longer produce that power without over temping they go on derated (detro) power.

for example: you could still do a full power takeoff if you were at sea level and the ambient temp was 28 degrees, however, if the temp increased to 32 degrees you may not be able to do that full power takeoff without overtemping the engines.

There are some procedures that go along with detro power aswell. All takeoffs must be with bleeds (ECS) closed, the CTOT (constant torque on takeoff) system must be operative, anti-skid system must be operative, and the autocoarsen system must be operative.

The intent of letting engines go derated is to extract the maximum useage out of the engine and to allow scheduling of maintenance events. The most common fix to the problem is replacement of the "hot" section of the engine (includes the combustor and the gas generator turbine).

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