Pulling/Pushing Props

I have seen a rope and sock method used to start an Auster 5 due to the compression. Sometimes the prop would flick back and has been known to catch the person’s wrist and arm,hence the use of.

I read an article a couple of years ago that put the whole Hydraulic lock thing in perspective. A guy in the states owned an An-2 and had just had a new engine fitted which IIRC had only flown about 5 or 6 hours since installatation. Anyway he was going to fly it one day and pulled the prop through as normal then decided to go have a coffee, came back out 30 minutes later and fired her up – wrecking his nice new engine. Just shows how quick it can happen. The guy reckoned that he’d learned his lesson. He also reckoned that there was so much radium (or whatever they use to make paint luminous) in the markings on the instruments that you could go night flying and get a suntan:D

Manual Starter

When I was serving at RAAF Darwin back in the early 1960s, I was puzzled to see RAF crews pulling a prop on a ‘Pig’ (Valletta) with a rope.

When I asked them why they were doing this, the engineer said the starter motor was US and, if I had ever had the job of replacing a starter motor on one of these *********g things, I would be pulling the prop too!Bri 🙂

Over fifty years ago when a school boy my brother would bring me copies of ‘The RAF Flying Review’ when he came home on leave from the RAF.
In one issue there was an article about a Vickers Varsity having a starter problem when on an Indonesian island. The crew obtained a length of rope which was wound around the propellor enough times to start the engine when pulled by a load of locals, this was shown in photos. The engine was started successfully!
Ray

More from Mr Curry’s article

As you can see you are correct.

The action of pulling-through identifies the problem rather than fixing it per se.

Moggy

Thanks Moggie 🙂

In the book ‘Aircraft Engine Maintenance’ by Daniel J Brimm and H Edward Boggess (pitman 1942) on page 135 there are details how to start a engine with a shock cord with leather boot on the end. Place the leather boot over the end of the prop, use 15 to 25ft of shock cord attached to a truck. Drive away from the airplane. When the cord is two to three times its normal lenght. The mechanic who holds the leather boot on the tip signals contact to the pilot and moves the prop in the direction of rotation. The boot flies of and the engine turns over!

😮

Think, I prefer this method!

Taking the topic just slightly off-course, I’ve heard that some Russian radials have some design feature that prevents hydraulic lock, and/or clears the oil from the cylinders without removing the plugs. Is this true, and if so how is it done??

Yep, I’ve seen some sort of device on a Ruskie radial. There’s a socking big tap on the inlet manifold. Excess oil collects in it when you pull the engine through, then you open the tap and make a mess all over the tarmac!

In the book ‘Aircraft Engine Maintenance’ by Daniel J Brimm and H Edward Boggess (pitman 1942) on page 135 there are details how to start a engine with a shock cord with leather boot on the end. Place the leather boot over the end of the prop, use 15 to 25ft of shock cord attached to a truck. Drive away from the airplane. When the cord is two to three times its normal lenght. The mechanic who holds the leather boot on the tip signals contact to the pilot and moves the prop in the direction of rotation. The boot flies of and the engine turns over!

I think there is a mod available on the Yak 52 Vedeneyev, but it certainly didn’t come as standard on ours.

Moggy

Taking the topic just slightly off-course, I’ve heard that some Russian radials have some design feature that prevents hydraulic lock, and/or clears the oil from the cylinders without removing the plugs. Is this true, and if so how is it done??

Mr. Curry’s explanation, above, is absolutely spot on.

It doesn’t just apply to radials. “Upside down” engines such as Gipsy Majors, Walter Mikrons and Cirrus’ssssss can also hydraulic, particularly if they’ve been standing a while.

That’s why you’ll see Chipmunk and Tiger Moth owners “pulling through” engines beofr ethe first start of a day.

I’ve had it happen to me with a Gipsy Major and it was amazing how much oil blurted out when we cleared it!

More from Mr Curry’s article

Avoiding liquid lock, as you can see, is critical to safe engine operation. The first line of defense in preventing this problem is to always pull the propeller through prior to starting the engine. Even if the engine has not run for only 30 minutes, pulling the engine through is good insurance against liquid lock.

Two complete revolutions of the crankshaft will take each cylinder through all of its cycles and insure that the cylinders are clear of excess oil. If, as the engine is pulled through, hard resistance is felt, STOP. Remove the #4 and #5 front spark plugs and drain whatever oil has accumulated in these cylinders.

NEVER pull the engine backwards (opposite to the direction of normal rotation) to clear a liquid lock. Though this procedure will often clear the oil from the combustion chamber, it merely moves the oil to the intake pipe where it is much more difficult to get rid of. The oil will sit in the intake pipe until it is drawn back into the combustion chamber by the vacuum created when the engine starts. Then you not only have a liquid lock, but also the inertia of the spinning propeller which will pull the engine through the lock and bend or break the link rod.

As you can see you are correct.

The action of pulling-through identifies the problem rather than fixing it per se.

Moggy

I think possibly they were pulling your leg

Starting a Bristol Hercules radial by handswinging is a definite non-starter 😀

However turning the engine over by hand before starting is normal procedure on big radials to avoid damage from hydraulic lock.

Courtesy Steve Curry – Radial Engines Ltd

Moggy

I always find this standard partial explanation trotted out a bit lacking in detail WRT to ‘avoiding a hydraulic lock’:

If a sufficient quantity of oil had pooled in a lower cylinder, enough to in fact cause a hydraulic lock, wouldn’t the act of pulling through TDC with the signifcantly superior mechanical advantage of a long blade (lever) through a reduction gearbox, than the starter, almost guarantee a bent rod?

Perhaps the act of pulling a blade through, identifies if a lock is occuring thus allowing the option to pull the plugs and drain before actually pulling through TDC, rather than risk using the starter to take a run at it without checking first?

Does the act of pulling through a few blades as well as identifying if a lock is going to occur, disperse excess oil that might not be sufficent to cause a lock, but perhaps make the starting a little difficult?

How easy is it to detect the load via the end of a blade where there is a hydraulic lock about to occur as opposed to just a normal pull through?

Further answers for more clarity please radial engine operators 😀

When I asked them why they were doing this, the engineer said the starter motor was US

I think possibly they were pulling your leg

Starting a Bristol Hercules radial by handswinging is a definite non-starter 😀

However turning the engine over by hand before starting is normal procedure on big radials to avoid damage from hydraulic lock.

By the very nature of its design the radial engine finds itself prone to the dreaded hydraulic or liquid lock. By gravity oil is drawn into the lower two cylinders #5 & #6 on a nine cylinder engine) where it pools in the
combustion chamber awaiting the next start up.

If the quantity of oil is small it will not affect the start up and will either be burned in the start up (blue smoke) or be expelled as oil droplets (wet start). If, however, there is sufficient oil in the cylinder to contact the piston as it reaches top centre, a liquid lock will occur. The piston will attempt to compress the oil which cannot be compressed, and one of several engine parts will fail. Most common is the bent link rod, but piston pins can bend and cylinder heads have been known to crack or even separate completely from
the barrel

Courtesy Steve Curry – Radial Engines Ltd

Moggy