Hello! Maybe some of you are able to identify following object: Its a large blank Cartridge made of Brass with some Text engraved on the Bottom: CART. ELEC. ENG. START No. 10 MK3 K. 71,2 The Dimensions are Diameter at Base with Rim: 8,2 cm Diameter 7,2 cm and a total length of 18,3 cm... In my opinion it might be a Coffman Start Cartridge for quite a big Engine! I would appreciate if this item will be identified to an engine type or even an Aircraft. Pictures are also available on demand!
many thanks for your quick response! I never thought that this gas turbines were able to be fired up with a cartridge, even that large... Does anybody know the principle? I worked with hydraulik start systems for Pratt&Whitney engines only in the late 70´s.
The object of the cartridge start was to allow the aircraft to be totally independant of ground services (electrics, air or hydraulics)
The cartridge case was filled with a slow burning charge of cordite - not the fast-burn charge of a projectile.
When ignited, the high pressure of the burn was directed to a turbine (about six inches in diameter) which wizzed round at about 50,000 rpm. This was connected to the engine compressor via a reduction gear and gearbox and retractable coupling (not unlike a car "bendix" drive)
Since the burn lasted about 5 seconds, it spun the engine up to a reasonable rpm and as long as fuel was delivered to the combustion chambers and the high-energy igniters worked OK, the engine started.
The early starters only had a single cartridge but later ones had three, so three attempts could be made to start without a re-load being necessary.
On later marks of Hunters the "cartridge" was replaced by a combustion chamber in which IPN (Iso-Propyl-Nitrate (liquid rocket fuel) was burnt.
Both - in my experience - were effective and reliable systems, although when the IPN one went wrong, it usually did so quite dramatically !
Interestingly, does the CAA allow these start systems on civil registered aircraft ? (I believe they ban Coffman starters on Chipmunks ?)
Way back in 1973 I was a civilian Flying Instructor at the Hawker Siddeley Flying Club based at Hawarden near Chester and the three Club DHC1 Chipmunks were fitted with Coffman starters which I understand was quite unusual,however these aircraft were orignally built there and the factory no doubt had a good working arrangement with the local CAA Office. All starts were therefore spectacular by civilian standards and whenever we appeared in public endeavoured to produce a synchronised start ,per the Reds of that era, but Sods law usually applied resulting in a misfire thus spoiling the effect. On one occasion I taxied backin with the Tiger Moth and witnessed a fellow Instructor standing beside the raised starboard engine cowling of a Chipmunk ,he was resplendant in a Daz white shirt and endeavouring to clear a Coffman malfunction at which point the malfunctioning cartridge actually fired and he took on the slightly startled resemblance of a chimney sweep and furthermore ever so slightly deaf as a result !! I understand that the three DHC1 Chipmunks were modified to electric starters when they were sold on, resulting in dimished Daz sales no doubt.
Last edited by midnight retired; 4th Jul 2009 at 23:50.
Today whilst visiting the Fenland and West Norfolk Aviation Museum with my 'personal guide' Richard Mason, a very nice and knowledgeable person, we came across this Coffman Starter exhibit, having read this thread and not knowing what they look like, I snapped a photo, Richard then showed me a second unit fitted to a recovered engine, which I 'think' was a merlin ???? I am sure you kind people will recognise the engine from what little is on view in my photo ????