Wooden prop placement when parked.

[Tom Downey]

Tom, those lovely photos look like a Sigma-Tek metal-hub vacuum pump which uses non-canted vanes and is bidirectional. Most pumps (Airborne, Rapco, Tempest) use a graphite hub with canted vanes and are designed to turn in only one direction (e.g., 211CCW or 212CW). I've actually never seen a Sigma-Tek pump disassembled before, that metal hub and big ball bearing are impressive. No wonder they cost more. --Mike

No Mike, it's a regular old Pesco wet pump. you can buy them off E-bay for 40 bucks they are used on a lot of old aircraft. Any dry pump that uses the vane style pump uses centrifugal forces to hold the vanes to the pump walls, that force is not present while rotating by hand. Any pump that uses a canted vane when rotated in reverse, actually will push the vanes away from the walls as it is turned. They will only pump in one direction that is why the model says CCW or CW.

I've never had a sigma-tek pump apart either. I've only dealt with 1, it was on warrantee so I could not play with it.

[Bill Berson]

My aircraft is parked outside. The wood prop has a light breathable cover when at the airport.
In the winter, I remove the prop and now the prop is in my unheated garage with humidity 80-90%.

I wonder if the prop should be stored in the warm house with drier air for the winter, or should it stay in the higher outside humidity all year?

[Tom Downey]

My aircraft is parked outside. The wood prop has a light breathable cover when at the airport.
In the winter, I remove the prop and now the prop is in my unheated garage with humidity 80-90%.

I wonder if the prop should be stored in the warm house with drier air for the winter, or should it stay in the higher outside humidity all year?

The water content of wood isn' t the real issue as to much of an unbalanced the blades are. I normally store a wooden prop on a shelf with the prop lying flat.

In either case simply run the prop at a low RPM the excess water will leave, it really isn't that big of a deal.

[IDAH]

There is one exception to the horizontal rule, and that is with a De havilland Gypsy Major engine (and may be other Gypsy series) and that is because with the prop horizontal oil ways are in such a position in the engine that the oil will drain from the crankshaft leaving the journals dry for re start. Of course that would matter only if left for long periods, or the prop could be put on in a different position, except that you could not prop it easily to start it.

[Richard Warner]

I might also add, Mike, check to see if the mag switch actually cuts off the mags at every shutdown if you normally stop your engine with a mixture control. Might just save your life.

[George Clymer]

Since most of the maintenance prop and vacuum pump points thusfar have been debated and/or amount to chickenshit, permit me the following REASON to turn ALL non-hangered two blade props horizontal whren parked: collisions. Anyone busy in the biz a coupla decades knows about and may even have seen or heard the impact of wingtip againt vertical prop blade. Oh sure... they were SUPPOSED to stay on the centerline but if it is their (and now your) unlucky day and they didn't, leaving the prop horizontal will be the difference between a ten grand (or more if spar bent) repair for them and a new prop for you vs having a wingtip harmlessly (or with only a paint scrape) breeze over the top of a cowling as the pilot stabs rudder. This could even be true for low wing in some combinations but certainly can avoid high wing/prop impact. And if someone is too stupid or careless to stay out of the prop arc when turning it horizontal, I say let Darwin do his important evolutionary work unimpeded.

[Frank Giger]

Thanks, all!

Fortunately the Champ's engine is shut off by using the mag switch, so it's a positive check that the mags aren't doing what they're not supposed to do when the switch is off! I always do a double check before moving the prop and treat it as if it is live.

On propping backwards, a caution on some Rotax engines - the manual says not to do that; don't know why for sure, but I heard it has something to do with the oil pump.

Never thought about the aircraft being struck on the ramp by another plane! That would be really nasty if the prop gets whacked, as one then has to treat it like any other prop strike and have the crankshaft looked at - or at least I would. But I'm kind of a chicken when it comes to the Big Fan and the things that make it go 'round and 'round.

[Bill Berson]

With my G109, I normally shut down my engine in flight at about 3000 feet AGL.
Then I get the prop positioned horizontally with a few blips on the starter switch. The reason I want the prop horizontal is because a horizontal prop is much less likely to be damaged in the case of a tip-up on the nose from heavy braking or an unintentional groundloop or excursion into the soft grass.

Experienced airplane pilots can do this as well, in the case of a stuck retractable landing gear (stuck in the up position), it saves the prop and engine if stopped horizontally.

p.s. the G109 is a motorglider (engine off landings are preferred)

[Eric Brown]

It has been said; if you don't position a wood prop horizontally, all of the pitch will run out of it.

[FlyingRon]

No matter how many times I've checked things, I always move that prop as if it will fire when I do so.
You can turn it backwards but if it kicks forward on the compression it still could fire the mag.

I'm amazed how long my plane will run after starting it with the mixture pulled out.