The Rolls Royce Peregrine Mk1 Engine

Over the years there has been a lot of discussion regarding the pros and cons of the Peregrine, Dave Gibbings and Matt Bearman have been good enough to put together their thoughts on the engine for us and to try and dispel some of the myths surrounding it.

Matt Starts

The altitudes at which dogfights happened is an interesting one. I am currently looking into the reality of this. There was something of a height obsession prevalent at the time, leading to the development of the Welkin to counter a high-altitude threat that never really materialised.
It would appear that most actual dogfighting in 1940 (as opposed to bomber intercepts) took place at altitudes well below 15,000 feet. The logical propensity to turn height into speed meant that most fights assumed a downwards trajectory once contact was made. The job, should the WW have been used as an interceptor (‘bomber destroyer’) in 1940, would be to ‘get in quickly, punch hard, get out’ to quote ‘Sailor’ Malan.. and this would have been quite within the aircraft’s capabilities, even if getting out involved diving for a height it could match any 109 at.
So, without development of the supercharger the WW would never make a great escort fighter for allied high-altitude heavy bomber streams – but this is about as far from its intended role as is possible to get.
I don’t think that Peter Twiss was uncomplimentary about the Whirlwind? The one he famously flew cross-country in the US had a dodgy compass. He acknowledged that the airframe was very tired by then, and seemed to think it did pretty well, considering.
The key thing for me is the ‘unreliable engines’ nonsense. Rolls Royce deserve this even less than Westland!

Dave Gibbins Continues

I offer a flight test engineers perspective

Although it was developed from the Merlin/Kestrel range of engines, the Peregrine was to all intents and purposes an undeveloped engine.  This meant that all the first units had comparatively short declared Engine life with a number of restrictions on usage such as:

A limitation on the power Temperatures and engine RPM allowable.

All this Slows down development, and puts up the cost. Any flight test engineer will tell you to avoid testing a new aircraft and a new engine simultaneously. 


 In 1940 we were very limited for resources. As regards replacing Peregrine with Merlin This too would be difficult, Early Merlins Weighed 1400 pounds/ Peregrines 1100 pounds, 600 pounds difference plus the extra power, would require stronger heavier installation, a stronger undercarriage a revised stress measurement program, reassessment of performance and a multitude of areas would require retest.  This does not come to nothing and could have added 50 to 100 hours flying, A great deal of analysis time all tying up resources We did not have.

In 1940 above all we needed interceptors, not escort fighters, and one aircraft per engine is a better deal than one aircraft per two engines. No matter what the fire power or small performance advantage.


All this doesn’t make the WW a bad aircraft, it is just force majeure. The shortcomings of Hurricanes and Spitfire were well understood, and the poor kids who flew them, could be trained to avoid them, it was going to take time for the same proven data to become available for the WW, and believe it or not a twin engine fighter vs a single is a debatable subject.

Given the time and resources we did not have, I am sure the WW would have delivered, but I do believe the right decisions were made under the dire circumstances of the times.

I really think it time we eased off debating the decision to cut back on WW, and celebrate its engineering and its potential, for the great aircraft it was.

Dave G

CAD by Rene Peters