McCauley Pucker Factor

In article

,
Orval Fairbairn wrote:

This past Monday, a couple of my friends took off in a Bonanza with a
3-blade McCauley prop installed. At about 1000 feet, on power
reduction, one of the blades came unhooked from its pitch change
mechanism and went into "free pitch" mode.

It apparently made a lot of racket and bad vibrations right away; they
were able to make a 180 and land downwind safely. They even had a hard
time taxiing, but all are safe.

Both McCauley and the FAA are really interested in this one -- to make
sure that proper overhaul procedures were followed and to ascertain
whether or not bogus parts were used.

The insurance company is paying for the engine teardown/rebuild, as
there is a possibility that the front bearing was damaged, due to
asymmetric thrust.

The fortunate thing is that it happened at 1000 feet, after takeoff from
a 4800 ft runway, lightly loaded.

Watch this space for possible AD and other stuff hitting the fan.


Followup:

I talked to the owner of the plane today -- he was present when they
opened up the prop hub.

The pin at the base of the blade had sheared off. This is about 1/2"
diameter and keeps the blade synchronized with the other blades. The pin
went off for metallurgical analysis -- it was either too brittle or had
improper heat treatment done, so there may be no joy in Mudville after
this one is done.

I wonder how many accidents have happened where the pin had broken and
was dismissed as accident damage, rather than accident cause.

Why do I smell an expensive AD coming?

--
Bob (Chief Pilot, White Knuckle Airways)

I don't have to like Bush and Cheney (Or Kerry, for that matter) to love
America

"Orval Fairbairn" wrote in message
news ...
In article

,
Orval Fairbairn wrote:

This past Monday, a couple of my friends took off in a Bonanza with a
3-blade McCauley prop installed. At about 1000 feet, on power
reduction, one of the blades came unhooked from its pitch change
mechanism and went into "free pitch" mode.

It apparently made a lot of racket and bad vibrations right away; they
were able to make a 180 and land downwind safely. They even had a hard
time taxiing, but all are safe.

Both McCauley and the FAA are really interested in this one -- to make
sure that proper overhaul procedures were followed and to ascertain
whether or not bogus parts were used.

The insurance company is paying for the engine teardown/rebuild, as
there is a possibility that the front bearing was damaged, due to
asymmetric thrust.

The fortunate thing is that it happened at 1000 feet, after takeoff from
a 4800 ft runway, lightly loaded.

Watch this space for possible AD and other stuff hitting the fan.


Followup:

I talked to the owner of the plane today -- he was present when they
opened up the prop hub.

The pin at the base of the blade had sheared off. This is about 1/2"
diameter and keeps the blade synchronized with the other blades. The pin
went off for metallurgical analysis -- it was either too brittle or had
improper heat treatment done, so there may be no joy in Mudville after
this one is done.

I wonder how many accidents have happened where the pin had broken and
was dismissed as accident damage, rather than accident cause.

Orval Fairbairn wrote in message .. .
This past Monday, a couple of my friends took off in a Bonanza with a
3-blade McCauley prop installed. At about 1000 feet, on power
reduction, one of the blades came unhooked from its pitch change
mechanism and went into "free pitch" mode.

There is a composite material link between the pitch change mechanism
and the blade acutator pin, which is on the circumference of the blade
shank. It's about 2" long.

This is a reason that McCauley specifically warns against pulling the
airplane with the prop while on the ground. If you pull on the back
edge of the blade, you can put enough torque on it to threaten the links.

Ond does wonder how they were cared for because this is a very rare
failure.

It would be like a terrible mistrack on a helicopter rotor.

Bill Hale BPPP Instructor