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Re: Speeding up the Rotax 914 Vacuum Pump PTO

Subject: Re: Speeding up the Rotax 914 Vacuum Pump PTO
From: EuropaChris@netscape.net
Date: Fri, 27 Apr 2001 08:25:34

"Steve Hagar" <hagargs@earthlink.net> wrote:

 My concern is the greater suseptibility of a prop 
> strike with the larger diameter disk. I am anticipating a ride on the 
> "wild side" while getting used to the monowheel landing configuration >  
> during
initial flights.
> 
Good point, Steve.  I think that is very valid, as the monowheel needs all the
clearance it can get.  We were actually thinking of going with a simple wood 
fixed
pitch to start out and get the feel of the plane, and then install a variable,
having made all the prior installation of the controls for the variable.


> At Sun and Fun I saw the Airmaster prop and was fairly impressed. Another 
> Europa owner swears by it. Being electrically activated you are not constantly

> running a pump. They are supposed to offer a fully feathering model shortly so

> you can feather it with a totally dead engine. Handily increasing engine 
> out glide (theoretically).

The Airmaster is on our short list.  There are several good props available it
seems, all a little different.  Again, with the electric prop, one may need more
alternator capacity.

 One concern I have with the geared Rotax engine 
> is being able to air start a dead engine with a bad starter. Being able to 
> dither the pitch may be of some use in an emergency to get the prop turning in

> the air. The warp drive prop blades are also pretty easy to come by when 
> dings occur.  

I think if you can fully feather a prop, even with the geared engine, as you 
bring
it back into running range, the prop will develop significant torque to get
the engine spinning.  I'd feel better with a feathering prop, that's for sure,
as with a standard prop, even in the coarse setting, the prop blades are pretty
well stalled if the prop isn't rotating, and won't give you much rotational
energy.

Regarding the starter, I wonder if that's much of an issue?  Reason why I say so
is these small permanent magnet units tend to be really reliable.  I'm on the
original unit on my Saturn SL with 138,000 miles on it.  I figure it's got at
least seven or eight thousand starts on it.  That's a lot of short flights 
before
you get to a 1500 hour TBO.

Chris 


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