Rob, 9312 fpm is 105.8 mph or 91.8 kts - still pretty fast, but allowing for
fact that you grasp blade perhaps 6 or 10 ins from tip, this would reduce
required handspeed by somewhere between 17 and 28% to between 76 and 88
mph. This is within the range that cricket balls are delivered. ( What's
cricket??!!) So with a 30 yd run up and a bit of practise, or with a degree
of desperation, maybe it is not quite so improbable. Cheers, David Joyce
----- Original Message -----
From: Rob Housman <RobH@hyperion-ef.com>
Subject: Europa-List: RE: Hand prop a Rotax?
>
> Something is suspicious here.
>
> According to Rotax the engine must be up to 1200 RPM in order to start, so
> let's do some math. 1200 RPM divided by 2.43 (the gearbox ratio) is 494
RPM
> at the prop. If we assume a 72 inch diameter prop, then the tip speed is
> 494 rev/min times 3.1416 times 72 in/rev divided by 12 in/ft equals 9312
> ft/minute or 155 ft/sec. Hmmm, that's about 120 knots, and I don't think
> any human can move a hand that fast let alone actually turn a prop against
> the engine's compression.
>
> So.... either Rotax is wrong or...well, draw your own conclusion.
>
>
> Best regards,
>
> Rob Housman
> Europa XS Tri-Gear A070
> Airframe complete
> Irvine, CA
>
> -----Original Message-----
> From: owner-europa-list-server@matronics.com
> [mailto:owner-europa-list-server@matronics.com]
> Subject:
>
>
> From: "Houlihan,Tim" <tim.houlihan@oce.co.uk>
> To: "'europa-list@matronics.com'" <europa-list@matronics.com>
> Subject: RE: Europa-List: Battery position
> Date: Fri, 27 Aug 2004 17:40:35 +0100
>
>
> ">Is an external power source point worth having?<
>
> If you don't an engine start with a flat aircraft battery will not be
> possible as you cannot hand crank a Rotax."
>
>
> Over the past three months I have spoken to two pilots who have hand
started
> their 912 equipped aircraft.
> I truly believe both of them.
>
> One of them found that the rising tide was a great incentive !!
>
> He landed on a beach to assist another microlight. When he came to restart
> the engine the battery was flat and the waves were only a few metres away.
> So he hand started it and saved the day !
>
> He tells me he had done this previously and was surprised when I told it
> could not be done !!!
>
> Tim Houlihan
>
>
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