rotax engine

[michelda]

Hi guys
I'm not a test pilot, but only an instructor.
In fto where I fly there is p2006 that we used for MEP rating.
The rotax engines have a limitation of 5800 rpm for 5 min maximum and 5500 RPM continuously.
In the cockpit I have only Map gouge and propeller rpm gouge.
How can know if I' m using the engine at or above 5500 RPM?

thanks for any answer
Michelda

[Firewalled]

One way is to find out the gearbox ratio in the manual and divide it by 5500. Does the POH not have prop RPM numbers?

[michelda]

I have prop RPM....
Red line at 2400 rpm and yellow band from 2400 to 2250 rpm.
As you know with about 17/19 of map and full forward RPM lever, I have 2400 rpm but I don't think that the engine is turning at 5800 rpm.

thanks for your answer
michelda

[FlyingForFun]

From this website:

Integrated reduction gearbox, ratio of 2.43:1

This would mean that 5800rpm at the engine equates to 2387rpm at the prop (which, when rounded, is your redline of 2400), and 5500rpm at the engine equates to 2263rpm at the prop (once again, this matches your yellow arc when it's rounded).

So it seems the markings on your rpm guage are correct for the engine limits.

This is with no first-hand knowledge (I operated a Rotax 914 for a while, but never a 912, and I never really thought about the gearbox ratio that much!) - it's just based on what I've found with some help from Google.

FFF
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[michelda]

Thanks for your replay,
We fly a lot single engine operation and I think it is important to understand if with less than maximum map and propeller control full forward, I' m flying at or above 5500 engine rpm.

Michelda