Dear all,
Rather than my own amateur theorising I thought I should ask some people who will know…
I’ve been researching the history of a particular Halifax III, namely HX356 of 158 Squadron. At the time of its loss, in a training accident in November 1944, the port inner was a replacement (469757 serial number as compared to 31xxxx & 38xxxx for the others) I am just trying to establish when this is most likely to have happened. For example, on the aircraft’s third mission it returned early with port-inner engine problems which are not elaborated upon in the squadron documents, this is one candidate.
Later, on 11th September while en route for Le Havre the port-inner suffered a broken throttle lay-shaft. My question is what would the manifestation of this have been? I’m certainly no expert on engines, would this have resulted in a misfire/idling to one or more cylinders resulting in the shutdown of the engine and prop-feathering? Or would it have been more catastrophic, involving an oil leakage etc? Is it possible to even speculate? The aircraft returned early to its home base having jettisoned bombs in the North Sea, so clearly there was no major emergency. It took part in operations the day later. I understand that if required an overnight engine replacement would have been difficult but possible and of course this was a time when maximum serviceability was been called for more than ever. Could a broken lay-shaft even approach the need for an engine change?
Of course it could have failed on a training flight which is now undocumented.
Then of course there is the question of 158 Squadron’s differing types of tail markings…
By: Zidante - 5th February 2013 at 21:04
Many thanks for the responses everyone, much appreciated!
By: MerlinPete - 5th February 2013 at 12:36
The control lay shaft is usually the cross shaft fitted to the firewall, so the above comments about lack of control would apply, but it wouldn’t require an engine change, as it is part of the airframe.
However, what the person who wrote that report actually meant could be something different, as is often the case.
Pete
By: sycamore - 5th February 2013 at 12:18
The layshaft is the rod/lever linkage on the engine connecting the throttle cables/rods to open/close the carb.butterflies/chokes.Depending where it broke the engine may maintain it`s power,or run back to idle ,or if it broke between chokes then one may have some power,but usually misfiring etc.Best to just feather it as less drag,than windmilling.
By: Bombgone - 5th February 2013 at 11:02
Recovered a Herc Carb from a clay dig site years ago. Remarkable condition, cleaned it up, still full of fuel. Made it as a display item. Very impressive bit of kit. 4 choke, the butterfly or throttle valves were huge. it had automatic altitude mixture control, using bellows.
I understand this was designed by a woman.
By: Zidante - 5th February 2013 at 09:26
Many thanks for the swift and thorough response Creaking Door, I suspect that it will have been a much earlier incident then.
By: Creaking Door - 5th February 2013 at 09:22
Cannot see a carburettor ‘lay shaft’ problem requiring an engine change myself; unless the fuel mixture is badly wrong it is actually quite difficult to physically damage an engine with a carburettor problem. More likely (for me anyway) the ‘lay shaft’ problem prevented the pilot from controlling the power produced by the engine so it was shut-down and the aircraft aborted the operation.
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February 5, 2013 at 8:34 am