John Slade wrote:

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.

The cable might be a good idea. However, I only know of one lost prop blade
incident. Dave Dormier's heat muff went through the prop and took out a
blade on his Cozy IV. He said the canard was vibrating so fast he couldn't
see it, but there were no reported engine mount problems. He dead stick
landed safely at a nearby field.

A lot depends on the motor mount and how it is fastened to the fuselage.
>From what I have seen of Burt's EZ motor mount designs I would not
count on the wimpy aluminum angle bonded into the fuselage
stringers to withstand the extreme loads. I can't say about the Velocity or
the Cozy. Use a cable to be safe.

Paul Lamar

Paul, I know it's not obvious, but the alum angles are not just bonded
to the the fuelage longerons in the Long EZ.  They are bolted (four 1/4"
bolts EACH alum angle fitting) to the main spar AND the fuselage
longerons. The spar and longerons are joined by a 3/16" thick angle ply
layup which is clamped between the angle and the spar and longerons.
The bottom alum angle is bolted to a 1/4" thick fiberglass pad pver a lot
of woodcore and foam core, and also to which the main gear attach fittings
(1/4" alum angle)  are attached, and thru a wood compression
core adjacent to the bottom spar cap.  Not as weak as it might seem
on a quick inspection.

I think I first saw a cable on Harold Neumann's Monocoupe that he used to
do skywriting and aerobatic competition.  He used an Aeromatic prop
which has metal hub fittings and a phenolic blade. Cables are used by air
racers, since they fool around with very thin prop tips and very high
rpms which can get you a lost prop tip and some serious imbalance.
Dick Rutan was/is a big fan of the cable, and it kept the front engine
on the Voyager when it pitched a prop blade from their electrically
controllable prop.   In defense of the prop maker, the Rutans had
extensively modified the blades and may have caused the problem.
Three of four mount tubes were seperated in the Voyager incident, IIRC

When the Lancair threw a prop blade at Reno a couple of years ago,
the vibrations separated the case halves about 1/2 or more at the
parting line and broke most of the motor mount tubes in the second or
two, before Morss could get it shut down.

Anyone using a prop that is not a certified prop on the intended engine or
a simple solid wood prop is at a substantially higher risk of losing a tip or a
whole blade and the cable is an extra layer to help you avoid a glider with
a CG 24" too far aft to fly.  Prop vibrations are complex and can be a
very serious problem, a 1/2 lb steel cable might be the only thing that
lets you make a normal dead stick landing after a prop failure.  At least
one aircraft that I know of has made a safe landing after losing the entire
engine, but I wouldn't recommend it.

Bill Freeman

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