Turning the Prop Over as Part of Preflight?

[O. Sami Saydjari]

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

[Dave Butler]

O. Sami Saydjari wrote:
> 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].

Sounds like the author has been flying with radial engines.

>
> I am quite surprised that this is the first I have heard such advice.
>
> What do folks on this newsgroup think of that advice?

Not necessary if you're flying behind a flat engine. Someone else will have to
speak for radials.

>
> 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?

Remove SHIRT to reply directly
Dave

[Peter R.]

O. Sami Saydjari ) wrote:

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

Wouldn't killing the engine by pulling the mixture lever out remove all
fuel in the cylinders?

--
Peter

[Roy Smith]

In article >,
"O. Sami Saydjari" > wrote:

> 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]

How old is the book? This sounds like something that would be advised
for radial engines, where such issues (called hydraulic lock) were
indeed a problem.

Unless your aircraft manual specifically advises you to do this, I
wouldn't.

[G.R. Patterson III]

"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.

[O. Sami Saydjari]

The book appears to have been published in 1995. He does not seem to
say anywhere that the advice is unique to radials.

-Sami

Roy Smith wrote:

> In article >,
> "O. Sami Saydjari" > wrote:
>
>
>>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]
>
>
> How old is the book? This sounds like something that would be advised
> for radial engines, where such issues (called hydraulic lock) were
> indeed a problem.
>
> Unless your aircraft manual specifically advises you to do this, I
> wouldn't.

[Chris Kennedy]

O. Sami Saydjari wrote:

> The book appears to have been published in 1995. He does not seem to
> say anywhere that the advice is unique to radials.

Hydraulic lock on radials without clean kits is well understood, but for
wet sump boxer engines like we generally fly behind the advice not only
makes no sense, it's contrary to Lycoming's current recommendations.
With the oil sump under beneath the engine there's simply no mechanism
for lock to occur, unless you tend to park your aircraft inverted.

About the only mechanism I can imagine for causing something like this
would be on some injected engines, where hitting the boost pump and
ramming the mixture full forward while the engine is stopped will dump
gobs of fuel into the intake runners. While much of it will eventually
come pouring out the air cleaner it's not hard to imagine getting
unlucky and having one cylinder with an intake valve open. Hardly seems
the basis for turning the engine over by hand as a standard procedure.

[G.R. Patterson III]

Chris Kennedy wrote:
>
> While much of it will eventually
> come pouring out the air cleaner it's not hard to imagine getting
> unlucky and having one cylinder with an intake valve open.

In any engine that has valves and at least four cylinders, at least one of the intake
valves will be open when the engine is not running. In a four-banger, there will be
one piston on the power stroke and another on the compression stroke, and these two
pistons will stop about halfway down the bore (where the compression in each is about
equal). One of the other pistons will be halfway down the intake stroke.

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

[g n p]

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
>

[Brendan Grace]

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
>

[Jim Burns]

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
>

[[email protected]]

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

--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

[G.R. Patterson 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.

[Roger Halstead]

On Mon, 17 May 2004 16:20:27 GMT, Chris Kennedy >
wrote:

>O. Sami Saydjari wrote:
>
>> The book appears to have been published in 1995. He does not seem to
>> say anywhere that the advice is unique to radials.
>
>Hydraulic lock on radials without clean kits is well understood, but for
>wet sump boxer engines like we generally fly behind the advice not only
>makes no sense, it's contrary to Lycoming's current recommendations.
>With the oil sump under beneath the engine there's simply no mechanism
>for lock to occur, unless you tend to park your aircraft inverted.
>
>About the only mechanism I can imagine for causing something like this
>would be on some injected engines, where hitting the boost pump and
>ramming the mixture full forward while the engine is stopped will dump
>gobs of fuel into the intake runners. While much of it will eventually

That's the way I start mine.

>come pouring out the air cleaner it's not hard to imagine getting

None of it comes out the air cleaner, but it sure do run out the
exhaust stacks. OTOH, Boost pump on for a count of three (or even
10)hardly qualifies for enough to block a cylinder. Course the count
of ten might start a fire. <:-))

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

>unlucky and having one cylinder with an intake valve open. Hardly seems
>the basis for turning the engine over by hand as a standard procedure.

[John Galban]

"O. Sami Saydjari" > wrote in message >...
> The book appears to have been published in 1995. He does not seem to
> say anywhere that the advice is unique to radials.
>
> -Sami

It certainly sounds like the old radial hydro-lock check. Since the
oil sump and fuel system of your average horizontally opposed engine
are lower than the cylinders, I can't see where this procedure would
be applicable. For radials, on the other hand, it's a very common
procedure.

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

John Galban=====>N4BQ (PA28-180)

[David Johnson]

I always pull the prop through at least two revolutions - just to make
sure there is compression on all six cylinders.

As for there being no need to do so with opposed engines, I vividly recall
a pilot telling the story about what happened to him. It seems he had just
bought a new (to him) airplane, and was trying it out. It was an early
model Cessna 210, with fuel injection. He decided to find out how fast it
was, and laid out a course between two points along the Southern California
coastline. Then he flew the course with the throttle and prop firewalled.
To cancel the efect of wind, he planned to fly it in both directions. The
outbound pass went well, but on the way back there was suddenly a loud bang,
and the view out the windshield went black (covered with oil). Down he went,
sighting out the side windows as best he could. He ditched it in the ocean,
and managed to get out before it sank.

It gets worse. As there were no boats within sight, he swam to the beach.
There was no one there either. Then a boat came along, so he swam out to
it. About that time, some rescuers showed up on the beach, so he swam
back again. Later, the plane was recovered. They found that a cylinder
had blown off the engine, right through the cowling. The analysis was
hydraulic lock, caused by a leaky injector. The theory was that the
cylinder had filled with gasoline, and was overstressed when the engine
was started. It could have happened long before the final flight.

Worst of all, he had neglected to obtain insurance for his new toy. The
only good news in this event is that he walked (or rather swam) away
with only a minor injury.


David Johnson

[CriticalMass]

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.

[O. Sami Saydjari]

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

Yes, it was.

[Dave Butler]

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]

The program is called "Cyberwar" and can be viewed at
http://www.pbs.org/wgbh/pages/frontline/shows/cyberwar/

You can see a more extended interview under the "interviews" link.

-Sami

Dave Butler wrote:
> 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.
>