ok, basic question..
my Os55ax is installed in GP extra 300 sp

If I go nose up, throttled back.. then open up the throttle to get some "hang time" (I´m not able to hover yet).. some times the engine will start to "wind down", (slow) rather than speed up.... if I throttle back quickly I can save it from a deadstick..

Could this be a badly set high needle? or is it a normal part of having an un-pumped fuel supply?

Probably the idle is too lean

Hi!
Or high speed needle...

ahhh confused now!!!!

Sound like a too lean setting to me.
I you can save it by throttling down, then the low end should be rich enough but the high end is too lean.

CeecRB1,


An engine that is to be adjusted for 3D flight, should be set to make it ultimately reliable; while doing 3D.

The setting of the low-speed needle differs somewhat, from that used in a normal sport plane...


This is more true with the low-nitro fuel that you would typically use in Spain.


The situation you must adjust to, is with the model in hovering attitude.
This may require that someone help you to hold the plane, while you do the adjusting and the throttling.

If you had adjusted the engine in level flight attitude; perfecting the transition from idle; the setting you have come to would be too lean, once the model is hovering nose-up at part-throttle.

It must be set to run well nose-up, at typical the 35-50% throttle required to maintain a stable hover (find that throttle setting).
But that's not where it ends... Upward acceleration during 'launch' from a hover, will cause the engine to become leaner as it accelerates.
It must be adjusted for a clean transition, from hovering to full, while accelerating

So it needs to be set a bit richer than the setting that would give 'perfect' nose-up transition, from the hover throttle setting (same as for 'normal planes' in level attitude).
It will be necessary for you to adjust as you go.

The setting of the high-speed needle is virtually the same as for sport models (peak minus 100-150 RPM, with the nose straight-up), but that adjustment will have little effect on your current difficulty (unless it is set so lean, that it affects the low-speed needle's range...).

tried this morning.. yeah it was too lean..
now i can concentrate on trying to learn to hover!

That depends upon the location of your fuel tank. Is it right behind the firewall? Or is it back at the CG?

A Perry VP-20 oscillating fuel pump would help you out in either case.


Ed Cregger