Merlin engine limits & failure behaviour

[Viper2000]

How impressively, deeply, illogical.

I never would have guessed. Thanks for the references.

However, this does raise some interesting questions about the lean cruise case, because obviously the interference between mixture and throttle control will limit the options.

I can see this making sense for infinitely variable mixture and fixed pitch prop (since you want a richer mixture at a lower rpm), but it raises interesting questions about the sanity of Camm et al in case of a 2 position auto mixture, not least because you could just use a toggle switch to set mixture if you wanted to take that path. Since Camm was a very clever man, I think that we need to dig deeper here.

Originally Posted by Viper2000

How impressively, deeply, illogical.

..that's British engineering for ya matey

[klem]

Does any of this explain why I get the following results when I push/pull the Boost Cut-out in the Spits and Hurris? (NB I have to jiggle the throttle or hit the WEP key to make it actually go into higher boost)

Hurricane DH 5-20 (AKY) @ ~8,000 feet in level flight
Full Throttle boost: 6.25lbs
Pull Boost Cut-out: 6.25lbs

Hurricane Rotol (FTN) @ ~8,000 feet in level flight
Full Throttle boost: 5.2lbs
Pull Boost Cut-out: 5.5lbs

Spitfire I (ZPE) @ ~8,000 feet in level flight
Full Throttle boost: 6.2lbs
Push Boost Cut-out: 6.2lbs

Spitfire Ia (YTR) @ ~8,000 feet in level flight
Full Throttle boost: 6lbs
Push Boost Cut-out: 6lbs

Spitfire IIa (OVC) @ ~8,000 feet in level flight
Full Throttle boost: 5.5lbs
Push Boost Cut-out: 8lbs

In the Hurricane DH 5-20 and the MkI/Ia Spitfires I don't see an increase in boost and the Hurricane wit the Rotol prop only gives an extra 0.3lbs.

Is that correct?