An earlier question concerning lower high altitude cruising fuel efficiency of the B-29 bombers with 4 x Wright R-3350 air-cooled radial Cyclone engines made me wonder about the Lancaster bomber, which was powered by 4 x Rolls-Royce Merlin liquid cooled in-line engines.

The R3350 needed to enrich its fuel mixture and open its draggy engine cowlings to avoid overheating its engines, negating the benefits of higher TAS with greater altitude.

Was the Lancaster able to avoid these issues with liquid cooling and gain fuel efficiency at higher altitudes, or would the extra demands of turbo and or supercharging limit these gains as well?

What was the Lancaster's best cruising altitude?


1 Answer 1


The Lancasters regularly cruised above 20,000 ft, near their service ceiling of 21,400 ft at 63,000 lbs. Nine model B.III's were converted to B.VI's by installing two-stage superchargers. This increased their service ceiling to 28,500 ft., but the engines were notoriously prone to failure for various reasons, including RPM "hunting" which would make it difficult to synchronize them. These aircraft were pulled from service in 1944.

  • $\begingroup$ This doesn't answer "What was the Lancaster's best cruising altitude?" as far as I can see. $\endgroup$
    – Zeiss Ikon
    Commented Jun 9, 2021 at 23:57
  • 1
    $\begingroup$ It does. I think everyone who is a pilot knows there is no "best cruising altitude" because it's always a judgement called based on many factors such as load, weather, etc. The fact that they "regularly cruised above 20,000 ft" tells you the answer as it relates to operational activities. Different models could also cruise at higher altitudes, as I explained in my answer. $\endgroup$ Commented Jun 10, 2021 at 0:52

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