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With today’s convenient push-button starters, it is easy to forget that this facility was BRIEFING FILE AEROPLANE JULY 2019 hard-won — previously, many more challenging methods were used to get engines running Under the skin of aviation technology and tactics Starting with a bang The units in more detail Cylinder Barrel assembly Barrels Starter unit Indexing pins Return spring Operating Cam Engine Main spindle spindle gear link Piston Operating 5 Firing 8 Starting dog lever 4 mechanism Combustion Firing pin chamber 1 Helically splined Exhaust shaft 7 3 Cartridge valve Helically splined 9 The Hawker Typhoon’s cartridge sleeve starter is located at the top and Push rod Ensures rear of its Napier Sabre engine FDUWULGJHZRQōWƓUHXQOHVV 2 sealing piston is positioned It consists of two main Linking gear components to crankshaft How it works 11 10 connected by a 1. Pilot pulls a toggle, turning operating spindle 7. Charge pressure pushes the piston… combustion tube: 2. A cam on the spindle pulls sealing piston away from 8. …engaging starter dog with engine gear Five-cartridge barrel breech barrel via levers and… 9. As piston moves, helical splines on shaft and sleeve slide assembly Operated Push pawl 6 3. …the drag pawl rotates the barrel assembly over each other, turning starting dog and engine gear mechanically and Combustion tube Drag pawl electrically by the pilot 4. Pilot releases toggle, lever returns and push pawl 10. At stroke’s end, piston pushes on exhaust valve bolt, completes barrel rotation, aligning fresh cartridge opening the valve Combustion Starter unit Sealing piston levers and repositioning sealing piston 11. Pressure releases, piston is returned by spring tube 12 Connected, when 56WDUWHUSUHVVHGE\SLORWƓULQJFDUWULGJHHOHFWULFDOO\ operating, via gears to Combustion tube Sealing piston 12. Gases exit combution chamber. If engine does not the engine’s upper 6. Charge passes to the starter unit start, process is repeated Exhaust tube crankshaft CARTRIDGE STARTERS WORDS: JAMES KIGHTLY ARTWORK: IAN BOTT he critical elements for six shells ready to be used. Early something entirely consumable in on the Beaver. One Chipmunk being the rule because of the Bizarrely, one standard size of aircraft engine starting English Electric Canberras, for the discharge such as cardboard. user in the UK remembers that 2/6d cost per cartridge. Today, Coffman cartridges was four- were that the total instance, had the single-cartridge As is well known from the Coffman cartridges were only most piston-engine types have gauge, equivalent to that of the weight of the starter kit arrangement, which could result dramatic engine start sequence in issued for ‘away’ landings, hand- been reconfi gured with other 19th century hunter’s black Tcarried in the aircraft had to be in a 10-minute delay while the the fi lm The Flight of the Phoenix, swinging propellers otherwise starting systems. powder elephant gun. A similar minimal, yet still able to start groundcrew had to wait for the involving Jimmy Stewart’s cartridge system was used in high-performance, and therefore area to cool enough to fi t a new character Frank Towns, the starter Marshall tractors, and in armoured demanding, aero engines. One one. Subsequent Canberras had a could become ineffective due to a One benefi t was that each cartridge military vehicles. Today some lightweight starter was the three-cartridge unit. One benefi t build-up of carbon in the starting cartridge engine starters are still Coffman cartridge, often known was that each cartridge was small, tube. In the original novel, by was small and simple to use, advantageous used in extreme low-temperature colloquially as a ‘shotgun starter’. easily stored and simple to use, Elleston Trevor, Towns’ thoughts in comparison to unreliable batteries or environments, where electric Patented by an American, advantageous in comparison to illustrate the idea of using a systems are unable to Roscoe A. Coffman, in 1935, unreliable batteries or bulky and cartridge just to clear the carbon: equipment like the Hucks starter perform properly. it was a means of converting a awkward equipment such as the “Risk the next cartridge on stable, compact burst of energy Hucks starter, and easier and safer clearing the pots — she was too in order to turn an engine over than the later isopropyl nitrate rich, stank of the stuff. Mixture effectively enough for it to pick up A mass cartridge start by Fleet Air Arm Hawker Sea Hawks aboard (avpin) liquid monofuel that was weak, switches off, throttle wide and start running on its own. In HMS Eagle during Exercise ‘Sea Enterprise’ in 1955. KEY COLLECTION used in some jet engine starting open and risk it.” FURIOUS BANGS AND EXTRA FLAMES simple terms, a gun-like bulletless mechanisms. The Coffman system was Coffman starts could be tricky, as recalled by a little more than usual. The second problem: cartridge was inserted into the adopted in the late 1930s, notably Royal Australian Navy Hawker Sea Fury pilot instead of turning the engine, the Coffman breech of a fi ring chamber, which required, the pilot would trigger catch and run the process was with the Grumman Wildcat’s Fred Lane: “If the cylinder priming time guess or ÃÌ>ÀÌiÀ} ÌÕÃ̼wââ½vÀÎäÃiV`ÃÀÃ>` was connected, via a metal tube, the cartridge’s primer, igniting the repeated, but this was the fi rst The cartridge itself looked Pratt & Whitney Twin Wasp, and throttle position was not just right, the impetus exude a cloud of noxious-smelling smoke.” to a device to turn the engine — cordite charge. The resulting gas of the system’s shortcomings to like an artillery shell, but there by 1940 on the Spitfi re II’s Rolls- from a single Coffman starter cartridge might On jets, a giant plume of black smoke was either a starter motor, as shown, explosion would be forced through be fi xed. If the breech had one were differences. The base plate Royce Merlin XII. Later wartime ÌLiÃÕvwViÌÌii«Ì ii}iÌÕÀ}} normal, while on the Gloster Javelin an or an element of the engine itself, the tube (at approximately chamber, the shell had to be was usually over-size to hold it use was with the Napier Sabre, enough. Firing the second or more cartridges ÕÃÕVViÃÃvÕÃÌ>ÀÌV>ÕÃi`i}i¼y`}½ such as on later jets. With the 1,000psi at 600ft per second) to physically extracted and a new one correctly in the chamber, while as illustrated, while post-war from the six-cartridge breech might or might not whereupon the subsequent start resulted in cartridge fi red by the pilot after cause the engine to turn. inserted. Later versions adopted a the front had a lip rolled in employment came with the DHC work. Sometimes it was best to wait 10 minutes > Õ}iiÝ >ÕÃÌy>ipëiVÌ>VÕ>À]LÕÌ the engine had been set with the As noted in the accompanying revolver-style multi-shell breech from the sides to hold the disc- Chipmunk’s Gipsy Major and the or so, then try again with the throttle advanced entirely harmless. ignition on and the fuel mixture as illustration, if the engine did not set-up, with between two and shaped cover, usually made from Pratt & Whitney Wasp Junior .

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