Apologies for any errors, but this may help for 412:
Done below limits (at 55% Eng Tq) and then checked against graph. Although, I think its acceptable to pull to limit (N1/ITT) and record everything else. May become a problem if you are at busy area, and climbing rapidly
Power Trend Checks, Topping Checks, Power Availability Checks?
The RFM for the 412 has a procedure for doing Power Assurance Checks...the maintenance manual has the procedure for the topping checks...there are several field expedient checks for determining power actually available for pinnacle landings, etc.....which one you looking for?
Aser.....mighty nice Co-Pilot you had with you at Heli-Tech...way too nice for you!
I mean Power Assurance Checks. I've seen pilots doing it just getting the heli light on the skis then write everything , but another said he prefer to do it by pulling just NEAR the limits , but not reaching it. I just wanted to hear more comments.
How often is a topping check done?
Sasless: I know the RFM but what do you mean with "field expedient checks" Thanks for the comments on the co-pilot , I will post some pics on the huey thread.
The Power Assurance Check is used to track the trend of an engine over time and requires you to apply power until the target Q, based on the current temp and PA, is achieved (OEI) . Usually you will be light on the skids because the target Q is in the region of 40-50% but you can also do this in flight (I don't recommend it though). The AFM describes the procedure clearly and also says that you should do a PAC daily. We do them every 25 hours.
The engine topping check requires you to fly OEI and pull power until a limit is reached (Q, N1, or ITT, whichever comes first). Should be done when an engine or engine component has been changed (governor, etc...). I always do them on contract when I take over a machine to ensure that, when I need it, full OEI power will be available.
412 PAC - best done at 55% Tq - puts the ITT into the expanded scale (>700deg) and is therefore more accurate. We no longer top out the engines (as was done on the 212) but insert a part-power stop. If, with that fitted, the N1 reads 92 - 92.8 when the Nr droops, the engine power is as it should be (Bell says).
Aser, little bit rusty on 212/412 AFCUs now, but as I recall, the topping adjustment is accomplished by moving a cam on the AFCU assembly, which then determines how far a mechanical arm attached to the throttle can move. To carry out topping checks without the need to get airborne, and to conserve engine life, it is possible to insert a bush of sorts (the part power stop) to this cam assembly, that limits the movement of the arm even further. The theory is that if you can achieve 92-92.8% g with this 'obstruction' in place, with it removed you should be able to achieve the normal topping figures (102.4 etc depending on the engine series).
In effect, this achieves much the same result as the means by which OEI training is carried out; a throttle is backed off to reduce the topping value and then frictioned tightly to prevent inadvertent movement while the other throttle is then used for simulating failures.