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The Coffman engine starter (also known as a "shotgun starter") was a starting system used on many piston engines in aircraft and armored vehicles of the 1930s and 1940s. The Coffman system was one of the most common brands; another was the Breeze cartridge system, which was produced under Coffman patents. Most American military aircraft and tanks which used radial engines were equipped with this system. Similarly, the British Supermarine Spitfire used the Coffman system to start its Rolls-Royce Merlin engine^[1]. The Hawker Typhoon also used the Coffman system to start its Napier Sabre engine.

A derivation of the Coffman starter was used on a number of jet engines, including such engines as the Rolls-Royce Avon, which were used in the English Electric Canberra and Hawker Hunter.

Contents 1 Design 2 Notable use 3 References 3.1 Notes 3.2 Bibliography 4 External links

[edit] Design

The Coffman device used a large blank cartridge containing Cordite which, when fired pushed a piston forward. A screw thread driven by the piston engages with the engine turning it over. ^[2]. This was in contrast with other type of cartidge starter which acted directly to drive the engine piston down and so turn the rest of the engine over (eg such as those used on the Field Marshall agricultural diesel engines)

The other systems used during the period were electric motors (such as those used in automobiles today) inertia starters (cranked either by hand or an electric motor) and compressed-air starters, which operated much like Coffman starters but were powered by pressurized air tanks.

Shotgun starters are composed of a breech (into which the cartridge is inserted) which is connected to the motor by a short steel pipe, which acts like a gun barrel. The blank cartridge fits into the breech, and is triggered either electrically or mechanically. When the aircraft's ignition is turned on and the cartridge is fired, high-velocity, high-pressure gas (~1000 psi at ~600 ft/s) shoots down the pipe, forcing the motor to spin and engage the starter ring on the engine, which is attached to the crankshaft.

The advantage of the cartridge system over electric starters is that the batteries of the time were weak and trouble-prone. Aircraft with electric motors often required the use of a battery cart and jumper cables, or large, heavy batteries carried in the plane. Inertia starters use a heavy wheel, usually made of brass, which is spun by a hand crank or electric motor, causing the spinning wheel to engage the starter ring. The Coffman system weighs less.

The primary disadvantages of the shotgun starter are the need to keep a stock of cartridges, one of which is used for each attempt to start, and the short time that the motor is spun by each cartridge. Compressed-air starters, which use the same type of motor, are usually recharged by an engine-driven compressor, negating the need to carry cartridges, but adding requirements for the compressor and air tank. Hybrid systems can be made simply by adding a cartridge breech or an air tank to an existing system.

The Coffman starter was the most common brand of cartridge starters during the mid-1930s, and the name was used as a generic description. Some modern military diesel engines still use this device, but advances in battery technology have made shotgun starters obsolete for most uses.^{[citation needed]}

[edit] Notable use

The starter became famous as a plot device in the movie The Flight of the Phoenix, in which pilot Frank Towns (James Stewart) has a limited number of cartridges with which to start the makeshift aircraft's engine. (This was also featured in the 2004 remake of the film.)

[edit] References

[edit] Notes

[edit] Bibliography

[edit] External links

• [1]

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