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ROTAX 912 - REVOLUTIONS


johnm
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I am not well versed at mechanics but i see a wealth of experience out there so here goes ......

 

the 912 i have up front - tecnam bravo - has now been adjusted to idle at about 2000 rpm - on the ground - departure is not a problem - arrival takes a bit more thought. before adjustment (i'd be guessing if i said old idle was about 1400 rpm) arrival was only a matter of closing the throttle and with use of flap - down she'd come - i'd have to admit there were some interesting noises from up front at 1400 rpm (reduction gear ?)

 

lets not degenerate this conversation into lift and drag - i'm interested in engine life

 

the theory behind 2000 rpm idle is no more interesting noises up front - which i think's good

 

so the question is - if you have a 912 with reduction gear (i guess they all do ?) what does it idle at and what about interesting noises up front ?

 

 

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Hi John,

 

I was reading in a Rotax Service Instruction the other day, that the 912 should be revved between 2500-2750rpm for warm up & warm down, whenever not actually being used for climb or cruise power. It's also supposed to stop shock cooling of the engine during descent.

 

Rgds,

 

Glen

 

 

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Guest pelorus32

One of the pre-takeoff checks on the P92 that I fly is: Idle - 1900RPM

 

If it idles too fast you can't get down and you can't land. If it idles too slow it stops.

 

The ugly noises up front in my experience are not derived from idle speed but aggressive use of the throttle from idle.

 

M

 

 

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Backlash

 

The reason for setting the high idle on the 912 series is to stop the backlash which occurs at revs below about 1600 rpm and can damage your gearbox if you continually allow it to happen.

 

My idle is set to 1400 rpm but I hardly ever use it except when I have to restrict my approach speed. I try not to idle below 1800 and use 2000 just after start, then 2500 to warm-up.

 

 

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