vjaqua wrote:

Another reminder of the fact that it is very simple to design a neat looking
controllable prop on a CAD program, do an extensive stress calculation,
do a beautiful job of building it, even test it on one installation, and still
provide an almost instant disaster. The Pulsar Super 100 prototype
made Sat 11:00PM news on channel 7, when it fortunately safely landed
in one of LA's concrete rivers near El Monte. An elecrtric controllable prop
which purportedly had been extensively tested on a Lancair, shed it's
blades converting the plane into instant glider shortly after take off.
Fortunately it apparently shed them both almost simultaneously, leaving
the rest of the plane intact, such that the skillful pilot was able to keep
himself and the plane undamaged.
Vance

Ken Powell wrote:

Just for the new guys - remember to use a safety cable between the engine and the firewall.  This will keep you from losing the engine if you lose a prop blade; my understanding is that the vibration will usually tear an engine off the firewall before you can get it shut down.  I am trying to listen when Bill Freeman and the other experienced guys give me a hint here and there.  Thanks for this one Bill.
Ken Powell
kenpowell@aristotle.net

ddunbar wrote:

Are we suggesting that this controllable pitch propeller was badly designed or is there a human failure here.

 This incident (since no one was injured,
and no property damage it is an incident, and
not an accident) happened Saturday afternoon
and Solly called me Sat evening to tell me,
since I had previously cautioned him about the
use of of new design controllible props in
general. To back up a bit- one of the items from
the Sun N Fun flight was that the original fixed 
pitch prop was oversize, limiting engine power.

The reworked prop was late in arrival, and this
prop that Solly had been negotiating with was 
brought by the designer from New Zealand.And 
so it was installed. Static runs indicated the
expected benifits of full power being available
at static conditions. Previous prototypes of
this prop had been satisfactorily operated o
a variety of engines and airplanes, so a flight
test was scheduled. On takeoff, at about 500 ft
a short period of vibration was almost insantly
followed by a thump, as both blades departed
(fortunately simultaneously). Instant glider.

The pilot (not Solly) executed a beautiful save,
landing in a nearby concrete "wash" (an LA type
river), with absolutely no damage to pilot nor
plane, and the plane was tranported back to the 
airport without damage. Apparantly this propeller
had an "improvement" that unfortunately had
weakened, and added stress concentration to 
the carbon blade hub.

The plane has been inspected for any structural
damage, particularly in the engine mount area
and the remanufactured - down sized Prince prop
has arrived, and
has been mounted. Flight tests will be done
at a more remote location, and departure for
Oshkosh is still scheduled for this weekend.
Vance


 
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