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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-1335265@logan.com>
Subject: Re: [FlyRotary Alternator failure quits engine
Date: Thu, 3 Aug 2006 11:48:49 -0400
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> Ed Anderson wrote:
>
>> Here is a story failure mode of an alternative engine on another list 
>> that I found interesting.  I rather doubt that stuck belts would cause a 
>> rotary to stop - although if at idle rpm, it just might.  I recall one of 
>> rotary flyer who had a bolt jam the water pump pulley, but this caused 
>> both belts to jump off the water pump pulley.  No coolant circulating, 
>> but pilot made it back to the airfield, had to make a go-a-round due to 
>> conflicting traffic, but landed safely.  Engine was toast but still 
>> running when he shut it down.
>>
>> Ed
>>
>>>
>>> The cause and subsequent sequence of events has now been established.
>>>
>>> Alternator bearing seizure initiated dual rubber v-belt slip at the
>>> crankshaft
>>> pulley.
>>> In 2-3 seconds 50 cruise hp turned both rubber belts into smoke and
>>> vulcanised
>>> them instead of driving the now freewheeling prop (no flywheel effect to
>>> snap
>>> belts).
>>>
>>> The alternator was switched off immediately but to no benefit since its
>>> load was
>>> not the issue.
>>>
>>> So instead of the crankshaft pulley driving the alternator, the 
>>> alternator
>>> now
>>> seized was now driving the engine to a stop! A relatively minor 
>>> accessory
>>> failure
>>> had initiated a cascade of events equivalent or even worse than a major
>>> engine
>>> failure.
>>
>
> This sounds strange, Ed.  A couple of slipping belts stopped the engine? 
> Is that possible?
>

Ernest, I would not have thought so myself.  I would assume the belt would 
jump the cleave or break.  But perhaps with a lower HP/Torque engine or 
especially at low engine rpm - two stopped belts might be sufficient 
additional load to cause the engine to die. But, it sounded like the engine 
kept turning (at least for a while) as it caused the heat and smoke cited. 
Perhaps that was sufficient to cause the pilot to shut down the engine 
himself.  Giving the smoke, vibration, etc,. not an unreasonable action. 
But, apparently, the pilot  did not.  The load appeared to cause the engine 
to die.  But, did he throttle back when the crap hit the fan - I'll bet he 
did, perhaps reducing the power from the 50 HP he cited to something 
considerably lower.

 It sounds like part of the reason this turned out worst, is the Sprague 
clutch referred to permitted the prop to windmill (spin freely) which 
considerably changed the drag and descent path.  Inoperative trim and the 
fact that apparently lowering the gear also extended the flaps (not 
necessarily what you want when trying to clear a hedgerow {:>)).

Luckily no one was injured.

Ed