An aircraft might fail if run too long at 12lb/3000rpm, but then again it might not, and failure is not an automatic consequence, and in fact unless the engine has suffered battle damage it probably won't fail if run until fuel exhaustion, but of course running out of fuel is likely to ruin your day, in any event.
Regarding the Spit Vc test:
Quote:
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.A.A.878 is fitted with a temperate type cooling system. The engine oil inlet and coolant outlet temperatures were measured on two climbs to 24,000 ft. This takes considerably longer than the 3 minutes for which the combat power may be used, a concession for test purposes. The observed temperatures are therefore likely to be higher than would normally be obtained in a 3 minute period at the same outside temperature. Even so, the oil inlet temperature is within requirements (100 deg C) for temperate summer conditions and does not exceed the emergency maximum temperature of 105 deg.C when corrected to tropical summer conditions.
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Quote:
The observed oil inlet temperature has been corrected to temperate summer and tropical summer conditions of A.D.M.491 by adding 70% of the difference between the appropriate standard and the observed air temperature.
.......Under tropical summer conditions, the oil inlet temperature exceeded the maximum permissible (100 oC) above 15,000 ft. and rose to 105 oC at 22,000 ft., and remained at this figure to 24,000 ft. with no tendency for the temperature to fall. The temperature exceeded 100oC for about 4 minutes.
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You will note that the test made allowances for increased temps during English and Tropical (IE Egypt) summers.
Dowding did take his pilots to task for probably abusing the use of 12lb boost:
http://www.spitfireperformance.com/dowding.pdf
but this was only one facet of abuse that could lead to engine failure, as Dowding's memo points out, but RAFFC had lots of spare aircraft and engines, and I doubt that pilots felt that they were using 12lb boost unnecessarily.
06-06-2011, 10:17 AM
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