Prop position

In rec.aviation.owning nrp wrote:
: Your prop just might be indexed correctly but differently than the ones
: I'm recalling. That seems to be a snake oil thing with different
: aircraft.

There was a thread on this awhile back. I'd concluded that at least on the PA28
like mine, the discrepancy is in the service manual itself. It calls for 10-2 IIRC, but
doesn't say if it's as viewed from the front or the rear. So, 50% of them out there are on
one way, and the others are 60 degrees off. I *still* don't know which is right.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

"Doug" wrote in message
oups.com...

The only other answer is some airplane elf came and reindexed your prop
in the middle of the night :-)


May not be as strange as it sounds.

Maybe someone needed a prop. They stole one, put it on your plane and stole
yours. That way the one reported as stolen is on your plane, which you may
never find out about. Mr prop theif winds up with yours, which never gets
reported.

I'm pretty sure where the prop stops doesn't measure anything.
How do you know it stopped in the same place "horizontally"
each time? There are at least two possibilities.

Why would the prop stop in a preferential position anyway?
Seems like it would be on any one of the 4 compression strokes.

I'm also convinced that even the differential compression
check doesn't show what you really want to know.
The rings are AC coupled, tho less so in the Lycomings.

So I'd guess one would need something worse to worry
about. Maybe price of gas or user fees!

Bill Hale

wrote:
I'm pretty sure where the prop stops doesn't measure anything.
How do you know it stopped in the same place "horizontally"
each time? There are at least two possibilities.

Right, unless you can somehow distinguish the two blades.


Why would the prop stop in a preferential position anyway?
Seems like it would be on any one of the 4 compression strokes.

There are 4 cylinders, and each one has a compression stroke every 2 revolutions
of the crankshaft. That makes 2 compression strokes per revolution. The prop
stops in one of two places, which are indistinguishable unless you can somehow
distinguish the two blades.


I'm also convinced that even the differential compression
check doesn't show what you really want to know.
The rings are AC coupled, tho less so in the Lycomings.

What does this mean: "The rings are AC coupled"?


So I'd guess one would need something worse to worry
about. Maybe price of gas or user fees!

Agreed. It's fun to think about, though, and if there's a sudden change in
behavior, I'd want to know what changed.

On Mon, 20 Mar 2006 19:57:03 +0000 (UTC),
wrote:

In rec.aviation.owning nrp wrote:
: Your prop just might be indexed correctly but differently than the ones
: I'm recalling. That seems to be a snake oil thing with different
: aircraft.

There was a thread on this awhile back. I'd concluded that at least on the PA28
like mine, the discrepancy is in the service manual itself. It calls for 10-2 IIRC, but
doesn't say if it's as viewed from the front or the rear. So, 50% of them out there are on
one way, and the others are 60 degrees off. I *still* don't know which is right.

Mine stops with the prop @ 2 O'Clock as viewed from within the cabin.

Did your propposition involve 10 o'clock and 4 o'clock?

.... or was it something about being horizontal?

Did your propposition involve 10 o'clock and 4 o'clock?

.... or was it something about being horizontal?

LOL. The usual "approach" has something to do with picking her up at 10
and dropping her off at 4 G

wrote)
... or was it something about being horizontal?

LOL. The usual "approach" has something to do with picking her up at 10
and dropping her off at 4 G


"I'm not that kind of girl - SLAP!"

"Contact."


Montblack :-)

"Steve Foley" wrote in message
news:BSDTf.6447$092.3203@trndny04...
"Doug" wrote in message
oups.com...

The only other answer is some airplane elf came and reindexed your prop
in the middle of the night :-)


May not be as strange as it sounds.

Maybe someone needed a prop. They stole one, put it on your plane and
stole
yours. That way the one reported as stolen is on your plane, which you may
never find out about. Mr prop theif winds up with yours, which never gets
reported.

Nope; nice try, though. I'd already made 3 stops that day in which
everything appeared normal.

wrote:

I'm pretty sure where the prop stops doesn't measure anything.
How do you know it stopped in the same place "horizontally"
each time?

Because I've been watching it carefully for 3 years.

A prop that stops in an unusual position can indicate a cylinder with poor
compression, as I discovered when I had cylinder trouble 3 years ago.

There are at least two possibilities.

Why would the prop stop in a preferential position anyway?
Seems like it would be on any one of the 4 compression strokes.

Becaues of the crankshaft geometry of the horizonally-opposed Lyc. O-360,
the prop will stop in the same compass position every time as it bounces
back from the last TDC.

I'm also convinced that even the differential compression
check doesn't show what you really want to know.
The rings are AC coupled, tho less so in the Lycomings.

?

So I'd guess one would need something worse to worry
about. Maybe price of gas or user fees!

No. Something has changed, and that's something to worry about.

--
Dan
C172RG at BFM