After my prang which I believe was due to overboost from wastegate sticking, I
have been at a loss to understand Rotax thinking. The turbo charger wastegate
default position is closed - ie turbo operating fully unless otherwise
commanded by the electronic control system. If any part of that system fails,
there is risk of overboost, and major engine damage.They advocate warning
lights to show turbo surge, and if overboost is likely, simply recommend
"reduce power to acceptable limits, limit operations (land), and fix the
cause"
My question is why not have some more positive option for the pilot in this
situation than simply warning light(s).
Has anyone considered having a manual over-ride to open the wastegate when
the warning lights indicate overboost is likely? I would have had plenty of
power to fly clear of trouble on 80 hp. and avoided the severe damage to the
aircraft and myself,if I could have simply disabled the turbo, and used the
normally aspirated function of the engine.
It should not be too difficult a task to devise a cable attached to the
servomotor cable outer, so that the wastegate can be forced open if
necessary. I do not know what forces would be required, but it would need to
be greater than the servo motor to be of any benefit.
Has anyone else had similar thoughts, or done any research, or know the force
generated by the servo motor on the wastegate arm??
I would like to have more options to do something about it when overboost is
threatening.
Graham Higgins in Oz.
914, Mono, Airmaster, 98 hrs to prang, rebuilding, but wanting something
better before I fly again.
> Subject: Re: Europa-List: 914 Waste Gate Sticking
>
>
> > Upon departure, at about 1800' agl, the waste gate stuck
>
> > closed, the engine over boosted and snapped the crank.
>
> > John Lawton
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