Spitfire & Hurricane flight model & engine performance thread. (1.09 patch)

[Osprey]

What klem is referring to is what I mean JtD. IIRC the Merlin XII did not require field modification, this was already done at the factory, and the throttle was different and designed with a dog leg 'gate' in order to move from max 9lbs to emergency 12lbs. It's a slightly different system to the Spitfire I. I have "Merlin In Perspective" - it's Robo's copy and I'm getting through it slowly!

[bongodriver]

Originally Posted by klem

There appears to have been two methods of bypassing the boost control.

The throttle had a gate, at which the normal max 9lbs boost was produced. At the gate you could shift the throttle to the left then forward to achieve +12.25lbs for takeoff.

Emergency combat boost of +12lbs was also available with the throttle at the normal max position (+9lbs) by pushing forward the red tab we are familiar with froim the Spitfire MkIa/100 octane.

Why there should have been two methods I don't know. I have the attached on my hard drive for the Spitfire MkII, I'll try to find out more if we have a copy of an original Manual at the museum.

the 2 methods make some sense taking into account JTD's mention of the automatic cutting out of 12lbs take off boost above 1000', the use of the famous red lever should give the emergency 12lbs instead of an instant engine death boost and is available for use when above 1000', it simply stands to logic that the fabled combat boost was 12lbs, as 9lbs was achieved by default at full throttle and we know the engine could handle 12lbs for at least 3 minutes.....more than enough time for a 'tight spot' in combat.

I always thought the instant engine death boost levels were only achieved when people went and started putting matchsticks in holes they shouldn't have.

[MadTommy]

As interesting as this might be for some of you, this thread was meant to be for posting observations about the performance of the Spit & Hurri as it is in game, not another discussion about historic records relating to flight models.

But hell at least people aren't slagging each other off.

[5./JG27.Farber]

Originally Posted by MadTommy

As interesting as this might be for some of you, this thread was meant to be for posting observations about the performance of the Spit & Hurri as it is in game, not another discussion about historic records relating to flight models.

But hell at least people aren't slagging each other off.

Originally Posted by luthier

Our goal has always been that the actual aircraft flight manuals should be used with Cliffs of Dover. If that’s not the case, the only people that know the guts well enough to write a flight manual are our aircraft programmers – and in that very case their efforts are better spent bringing the performance in line with the actual flight manuals.
In other words, there’s never a situation where writing a flight manual for Cliffs of Dover is a good idea.

...and your first post starts with an out of game document...

[JtD]

Attached a description of the automatic boost control unit as in the Merlin II. You can see how the cut out would work. You can see that it would give full boost, only depending on throttle setting, when the cut off was engaged.

Guess this has been posted before, but so what.

[JtD]

On the Merlin 20 series, the maximum boost available in case of the cut off engaged was regulated through bleed holes of a particular size - which at least required different cut out valves. This way the cut off no longer disabled the abc completely, it just reset it to a higher boost level.

The take off setting did not use the mechanism of the cut out valve, but went a different way, the particulars of which I don't remember right now. It essentially is a fixed throttle setting around the abc as opposed to an abc controlled boost, managed through varying throttle settings depending on a pressure balance. The boost limit with engaged abc cut off and the boost limit with the take off setting are not related.

The necessary modification for the Merlin XII when using all out level with 12lb boost would be a modification of the cut out valve.