PPRuNe Forums - View Single Post - Inertial Particle Separator & TO Distance
Old 13th Aug 2015, 13:44
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FGD135
 
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Yes, itt, fuel flow and tq increases.
GTang,
If this is what you see when doing a static engine run, then it can only be an instrumentation fault. It is physically impossible to get a further rise in those parameters without the Ng also further increasing (in the case of a static engine run). You may be seeing the indicated Ng cease rising, but the actual Ng must still be rising.

On a takeoff roll however, it is perfectly normal to get a rise in those parameters whilst Ng stays constant - this is the ram effect.

Please explain the location of the NG gov.
It may not be called that, but I am referring to the mechanism with the speeder spring and flyweights that signals the FCU to increase/decrease fuel flow.

The 3% loss is what I first said. It's the loss of ram air affect.
No. I think you will find that the performance tables for this aircraft make the assumption that rated torque is achieved by the engine for every takeoff, including those with the separator open (this can be confirmed by a 750 pilot - he just needs to confirm that the AFM gives one torque value for all takeoffs).

In practice, this is achieved, for a separator-open takeoff, by just slightly increasing the Ng (thus compensating for the reduced air flow). The pilot does what he always does for takeoff - advances the power lever in order to set the target torque.

With the separator open, of course, he may notice a slightly higher ITT. If he is really sharp-eyed, he may notice the Ng is also slightly higher.

That 3% factor on the TO distance, queried by FoolCorsePich, can only be due to the aerodynamic drag of the open separator.
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