How Do I Start Thee? Let Me Count ONE way

Factual Questions
1

I recently saw a video of a restored WWII B-24 Liberator aircraft starting up. I’ve also been brainwashed by a 40 year old viewing of the original (James Stewart) Flight of the Phoenix.

In the movie the cobbled-up plane used some firing cartridges to start the engine. How did a real B-24, B-17, etc. start their engines? With the airplane equivalent of an electrical starter motor? Or something more akin to successive firing cartridges? Or…?

2

Modern 1940s aircraft used starter motors. Generally the pros need to be pulled through a few rotations to distribute the engine oil, but the actual starting was accomplished by a push of a button.

3

The firing cartridges were called a Coffman starter.

Some British Spitfires used Coffman starters.

In a similar idea, some engines used compressed air for starting, typically supplied by an external air compressor instead of a single-use cartridge.

How to start a B-17 (looks like it’s from an original pilot training film from back in the day)


For the B-17, an electric starter motor spun a flywheel, and once the flywheel was up to speed, that was used to start the engine. Flywheel starters like this, called Inertia Starters, were common. On some planes the flywheel was hand-cranked by the ground crew.

The B-24 also used an electric starter, which you can hear cranking in this video:

Some B-24s had a “putt-putt” generator (APU) installed in the front of the plane. This generator could provide enough electrical power to start the engines. On-board batteries or an external battery cart could also be used.

The B-29 had a putt-putt generator in the back of the plane. The B-29 could also be started from an external battery cart.

4

Thanks for the scoop. – ASG

5

Cartridge starters (basically a bigass blank shotgun shell pushing a piston that turned the main shaft via rack and pinion) were a thing on late piston and early jet engines for emergency scrambles (Soviet missiles in the air, etc.) but mainly early radials had a flywheel you’d spin up with a hand crank and then engage a clutch to connect it to the engine crankshaft, sometimes with an electric motor instead of a hand crank, hence the stereotypical sound effect. Later radials used electric starters just like cars – so you could boop the button to crank them over with the spark off to pump out the oil pooled in the bottom cylinder heads (Count four blades, then flip the magnetos to “on”) to prevent blowing the heads off due to hydrolock.

Most modern jets have an air turbine (powered by a ground cart blower) or electric starter motor on one engine, and then use bleed air from that one to spin up the others via geared turbines, a few military jets have cartridge start on all the engines so they can go on short notice.

6

I remember driving a tractor back in the 60s with a cartridge start. You stuck a fuse in a hole at the front, a blank 12 bore in the side, and whacked it with a hammer. Single cylinder two stroke - started first time even on a frosty morning.