Turning the Prop Over as Part of Preflight?

BTW - Was that you I saw on "Frontline" last week?


Yes, it was.

O. Sami Saydjari wrote:

BTW - Was that you I saw on "Frontline" last week?


Yes, it was.


This cries out for further explanation! Which Frontline episode? What was the
context?

Dave
Remove SHIRT to reply directly.

"O. Sami Saydjari" wrote:

I am quite surprised that this is the first I have heard such advice.

How old is this book? (I'm guessing that it dates from the 30s or 40s).

What do folks on this newsgroup think of that advice?

Sounds like he's talking about radial engines. Radials indeed tend to collect oil in
the lower two or three cylinders. Most radial owners pull the prop through a few
times to check for hydraulic lock. The old "inverted" engines like the Ranger series
sometimes presented similar problems. This is not a problem with the horizontally
opposed engines behind which most of us fly.

Does anyone out there do this routinely?

I frequently pull the prop through four times to check compression. This also makes
it slightly easier to start in Winter by breaking the gummy oil bond that tends to
form between the rings and cylinder walls.

If so, what is the proper procedure? Do you just turn the prop slowly
in the direction the prop normally turns?

Make sure the mags are off and mixture at lean cutoff. Pull the prop in the direction
it normally turns. Stay out of the plane of the prop. My prop is indexed to stop
straight up and down. When I pull the prop through, I pull the lower blade up.

Could fuel actually collect in the cylinders as suggested?

Not in most light planes. The carb is usually behind or under the engine. Even if gas
did flow through the carb (and there are several valves that usually prevent this),
the fuel would just fall out the throat of the carb.

Why would the fuel not just evaporate?

If raw gas pooled in the cylinders or induction system, the saturation point of the
air in there would be reached rather quickly.

George Patterson
I childproofed my house, but they *still* get in.

G.R. Patterson III wrote:
: I frequently pull the prop through four times to check compression. This also makes
: it slightly easier to start in Winter by breaking the gummy oil bond that tends to
: form between the rings and cylinder walls.
: Make sure the mags are off and mixture at lean cutoff. Pull the prop in the direction
: it normally turns. Stay out of the plane of the prop. My prop is indexed to stop
: straight up and down. When I pull the prop through, I pull the lower blade up.
:

I generally pull my Lycoming O-360 through at least 4 blades (all compression
strokes) to verify that I've got the adequate and roughly equal on all strokes. I got
in the habit of doing this after a recent top overhaul, to check on the status of the
break-in.

In addition to the mags being switched off, mixture leaned, and never primed,
I *always* pull it through as if I were hand-propping it (expecting it to fire off).
If you ever once pull it through without that thought, you're looking to have a new
nickname.

That said, it probably doesn't do much for the engine, good or bad. In cold
weather, just nudging the prop would do the same "loosening" as pulling it through a
few blades. If your oil truly is that gummy, though, better rethink your oil-changing
invervals...

FWIW,
-Cory

--
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* The prime directive of Linux: *
* - learn what you don't know, *
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I do it when it's 5 C outside or below, just to help the battery and starter
a bit.
________________
G. Paleologopoulos


"O. Sami Saydjari" wrote in message
...
In reading a booked called "Design for Safety", by David Thurston, he
advises owners to "turn the propeller over by hand three or four times
during preflight if the airplane has been standing for half a day or
longer." [p169]

His rationale is as follows. "When an engine has been standing for
awhile and has not been pulled through by hand prior to starting, an
accident could result if fuel or oil has collected in the cylinders.
When the engine fires, trapped fluids can cause bent piston rods,
cracked cylinders, or a damaged crankshaft. Althouogh such accidents
might not cause bodily injury, they surely can harm one's budget and can
beavoided by proper preflight procedures. It is also possible for
damage of this type to remain hidden until something fails in flight"
[pp 147-148].

I am quite surprised that this is the first I have heard such advice.

What do folks on this newsgroup think of that advice?

Does anyone out there do this routinely?

If so, what is the proper procedure? Do you just turn the prop slowly
in the direction the prop normally turns?

Could fuel actually collect in the cylinders as suggested? Why would
the fuel not just evaporate?

-Sami
M2057M, Piper Turbo Arrow III

If you even remotely suspected fuel then hand propping seems to
be to be an invitation to the new name of Stumpy. Why take a
chance on a cylinder firing and removing an appendage??


"O. Sami Saydjari" wrote in message
...
In reading a booked called "Design for Safety", by David
Thurston, he
advises owners to "turn the propeller over by hand three or
four times
during preflight if the airplane has been standing for half a
day or
longer." [p169]

His rationale is as follows. "When an engine has been standing
for
awhile and has not been pulled through by hand prior to
starting, an
accident could result if fuel or oil has collected in the
cylinders.
When the engine fires, trapped fluids can cause bent piston
rods,
cracked cylinders, or a damaged crankshaft. Althouogh such
accidents
might not cause bodily injury, they surely can harm one's
budget and can
beavoided by proper preflight procedures. It is also possible
for
damage of this type to remain hidden until something fails in
flight"
[pp 147-148].

I am quite surprised that this is the first I have heard such
advice.

What do folks on this newsgroup think of that advice?

Does anyone out there do this routinely?

If so, what is the proper procedure? Do you just turn the prop
slowly
in the direction the prop normally turns?

Could fuel actually collect in the cylinders as suggested? Why
would
the fuel not just evaporate?

-Sami
M2057M, Piper Turbo Arrow III

I've been reading the POH for an older Piper Apache 150 lately and it
suggests pulling the prop through several times in cold weather. (I'm just
assuming to circulate some oil through the engine and prop hub, but then
again just how much would actually circulate when it's cold??) Although the
Apache has Lycoming engines, I too wonder if this is a carry through from
the radial days.
Jim Burns

"O. Sami Saydjari" wrote in message
...
In reading a booked called "Design for Safety", by David Thurston, he
advises owners to "turn the propeller over by hand three or four times
during preflight if the airplane has been standing for half a day or
longer." [p169]

His rationale is as follows. "When an engine has been standing for
awhile and has not been pulled through by hand prior to starting, an
accident could result if fuel or oil has collected in the cylinders.
When the engine fires, trapped fluids can cause bent piston rods,
cracked cylinders, or a damaged crankshaft. Althouogh such accidents
might not cause bodily injury, they surely can harm one's budget and can
beavoided by proper preflight procedures. It is also possible for
damage of this type to remain hidden until something fails in flight"
[pp 147-148].

I am quite surprised that this is the first I have heard such advice.

What do folks on this newsgroup think of that advice?

Does anyone out there do this routinely?

If so, what is the proper procedure? Do you just turn the prop slowly
in the direction the prop normally turns?

Could fuel actually collect in the cylinders as suggested? Why would
the fuel not just evaporate?

-Sami
M2057M, Piper Turbo Arrow III

Jim Burns wrote:

(I'm just
assuming to circulate some oil through the engine and prop hub, but then
again just how much would actually circulate when it's cold??)

Pulling the prop through will do absolutely nothing to circulate oil. It usually
takes several seconds for the oil pressure gauge to come off the peg after engine
start, and that's at about 1,000 rpm.

George Patterson
I childproofed my house, but they *still* get in.

Jim Burns wrote:

I've been reading the POH for an older Piper Apache 150 lately and it
suggests pulling the prop through several times in cold weather. (I'm just
assuming to circulate some oil through the engine and prop hub, but then
again just how much would actually circulate when it's cold??) Although the
Apache has Lycoming engines, I too wonder if this is a carry through from
the radial days.

But the point should be, we need to try to elevate ourselves from the
50-year-old advice in those old references, and try to do what makes
sense today, with the advances in lubricating oils which were not
available when those old instructions were written.