F3F cartridge starter

[Joe Broady]

About 11 minutes into the video on this Grumman F3F page, the host (a retired Harrier pilot) explains the cartridge starter. He opens the breech in the left wheel well to show where the cartridge is inserted. Then he explains the gas when the cartridge fires goes into the intake manifold, enters any cylinder with an open intake valve, and rotates the engine. That was a surprise to me. I always had the idea the gas was directed into an accessory which turned the engine, much like an electric starter. But if it's routed into the intake manifold, there must be a check valve to prevent blowing back through the carburetor. Or maybe the throttle can shut off totally for the start? Puzzling!

The 1940 (?) movie Flight Command shows F3Fs doing cartridge starts. There's a little pop, not like the loud bang of the Coffman starter in the 1960s Flight of the Phoenix. Can't remember the engine start in the remake. Of course in a Hollywood production you don't know if that's the actual sound or they just dubbed in something.

I think it was Corky Meyer who wrote that a Hellcat pilot was considered a dud if he needed more than one cartridge.

Grumman F3F

 

[MiTasol]

If the discharge entered the intake manifold it would take the route of least resistance and all come out through the carb intake.

This is the Coffman setup on the Spitfire and attached is a US TM on the Breeze cartridge starters fitted to tanks. The aircraft versions were almost identical.

 

[GrauGeist]

Then he explains the gas when the cartridge fires goes into the intake manifold, enters any cylinder with an open intake valve, and rotates the engine.

He has two different Coffman starters mixed up.

The Coffman starter for aircraft used the expanding gas from the discharge to turn a worm-gear, which turned the engine's flywheel.

The direct to cylinder Coffman starter was used on ground vehicles and tanks, where the expanding gas from the discharge was piped directly into a single cylinder of the engine.

Coffman also introduced a device that atomized fuel into the intake that assisted ignition during the starting process.

 

[MiTasol]

I did not realise that Coffman produced a system similar to the pneumatic starters that the British used on a lot of engines and the Russians still use.

Obviously, like the Brit and Russian systems, there must be a distributor valve that directs the airflow to which ever cylinder has just passed top dead centre. I would presume that it also, like those systems, distributes the air to more than one cylinder in sequence until the pressure dissipates.

 

[Engineman]

The F3F vid is somewhat basic.
The Cartridge starters on some piston engines usually use the high pressure combustion gasses from the cartridge to move a starter unit piston that turns the engine by a spiral groove drive and a starter claw coupling. The normal engine systems such as magneto's and pumps function just as normal and suitable priming is done before actuating the starter.
Compressed gas/air starters for piston engines can have a distributor that directs the pressurised gas into cylinders via pipes and one-way valves, into the cylinders on the firing stroke. These were common on some Russian engines.
Later gas-turbine cartridge starters used a small reaction turbine that was driven by the gasses to spin the engine spool via gearing. These starters needed much more gas to operate and the cartridges were often upto about 3in dia and 6in long approx.
Overall, there are many different types of engine starters!

Eng

 

[Maxrobot1]

Coffman Starter on the 1936 F2F at the 58 second mark.

View: https://www.youtube.com/watch?v=Os19XiWGDjs

 

[cvairwerks]

Starting an FM-2 with a Coffman.

View: https://www.youtube.com/watch?v=65qrzgbTTcQ