Radial Engine

[Slick Goodlin]

Isn’t backwards movement the worst thing you can do?

Some say it’s bad for vacuum pumps, others say it can damage generator brushes. I figure both of those are easier to replace than con rods.

[Chuck Ellsworth]

Some say it’s bad for vacuum pumps, others say it can damage generator brushes. I figure both of those are easier to replace than con rods.

The reason you pull it through by hand is if you have hydraulic lock you stop pulling and remove the spark plug and drain the oil out of that cylinder.

[JW Scud]

Isn’t backwards movement the worst thing you can do?

Some say it’s bad for vacuum pumps, others say it can damage generator brushes. I figure both of those are easier to replace than con rods.

I mean for increasing the likelihood of actual engine damage.

[Chuck Ellsworth]

I mean for increasing the likelihood of actual engine damage.

When pulling an engine through by hand if you a cylinder has hydraulic lock it will be quite evident by the fact that it suddenly has become difficult to pull that cylinder through......so you just quit pulling and drain that cylinder.

[JW Scud]

I mean for increasing the likelihood of actual engine damage.

When pulling an engine through by hand if you a cylinder has hydraulic lock it will be quite evident by the fact that it suddenly has become difficult to pull that cylinder through......so you just quit pulling and drain that cylinder.

Correct. Pulling the prop backward can move oil to the intake area instead of removing it. The oil can subsequently go back into the cylinder and damage the engine.

[Chuck Ellsworth]

Also getting back to the picture L.C. posted the sun was quite bright as demonstrated by the shadows under those two machines.

[Colonel]

I've never encountered an engine in 50 years which would be damaged by rotating backwards.

I'm not saying there isn't one out there, but the odds of it being a problem for you seems pretty slim.

Meta-observation: people spend a lot of time worrying about stuff (0.001%) they don't have to, and they don't spend a lot of time worrying about stuff (99.999%) that they have to.

Why is that? This is an honest question.

[JW Scud]

I've never encountered an engine in 50 years which would be damaged by rotating backwards.

I'm not saying there isn't one out there, but the odds of it being a problem for you seems pretty slim.

Meta-observation: people spend a lot of time worrying about stuff (0.001%) they don't have to, and they don't spend a lot of time worrying about stuff (99.999%) that they have to.

Why is that? This is an honest question.

This is why(because it is a legitimate worry),

"The US Air Force Powerplant Maintenance Manual (AFM 52-12, May 1953), in a section on hydraulic lock involving radial engines, states:
‘Never attempt to clear the hydraulic lock by pulling the propeller through in the direction opposite to normal rotation, since this tends to inject the liquid from the cylinder into the intake pipe with the possibility of a complete or partial lock occurring on the subsequent start.’"

"The pilots of G-AWVF had not been employing the engine manufacturer’s recommended practice of removing the spark plugs to clear a suspected hydraulic lock and their practice of turning the propeller back to clear the lock could have caused oil to be re-introduced into the cylinder during start, and cause hydraulic lock damage."

"Conclusions
The accident was caused by an in-flight engine fire that probably rendered the pilot unconscious. The fire was caused by a catastrophic mechanical engine failure which was initiated by a fatigue crack of the No 6 piston gudgeon pin. The exact cause of the fatigue crack initiation could not be determined but it is likely that a high-load event, such as a partial or full hydraulic lock, initiated the crack in the pin. The presence of corrosion pits on the inner surface of the pin, which would act as stress raisers, was probably a contributory factor, and the aircraft’s low utilisation rate during the previous 45 years probably contributed to the formation of corrosion."

"Safety Recommendation 2010-030
It is recommended that the Civil Aviation Authority notify operators of piston radial engines of the correct technique for clearing a hydraulic lock"

https://assets.publishing.service.gov.u ... _10-10.pdf

Never move the prop backwards in an attempt to clear a hydraulic lock. Chuck's procedure was right.

[Colonel]

gudgeon pin

I don't know why, but I love that term. Probably because it was in a Bartholomew Bandy book,
when he landed on that road and dicked the General's wife.

Other people, growing up, their heroes were Al Gore, or Greta Thunderberg. Mine was Bandy.



Taught me two valuable life lessons:

1) women can't resist a guy that flies a biplane.

2) if you have to jump out of an airplane to test a badly designed parachute, land on a General's cock.

[Chuck Ellsworth]

And I though I was sick.