Bug 174 on 12lbs boost. Review please.

[Kurfürst]

Emergency / Combat boost was +9 on the Spitfire during the BoB, not +12.

[NZtyphoon]

Originally Posted by Kurfürst

Emergency / Combat boost was +9 on the Spitfire during the BoB, not +12.

Utter nonsense, of course

http://www.spitfireperformance.com/ap1590b.jpg

http://www.spitfireperformance.com/dowding.pdf

http://www.spitfireperformance.com/lane-26-5-40.jpg

http://www.spitfireperformance.com/webster-28-7-40.jpg

http://www.spitfireperformance.com/gribble-12lbs.jpg

http://www.spitfireperformance.com/elliott-9-9-40.jpg

http://www.spitfireperformance.com/McMullen-15oct40.jpg

[Kurfürst]

Correction: Spitfire II limitations for BoB were +9, not +12.

See:

[Robo.]

Originally Posted by Kurfürst

Correction: Spitfire II limitations for BoB were +9, not +12.

I am sorry but you're wrong. +12 was used in Spitfires Mk.II during BoB.

[Kurfürst]

Originally Posted by Robo.

I am sorry but you're wrong. +12 was used in Spitfires Mk.II during BoB.

And the source for that..?

[41Sqn_Banks]

The use is reported on:
- 21 August 1940 http://forum.1cpublishing.eu/showpos...postcount=1441
- 2 and 30 November 1940 http://forum.1cpublishing.eu/showpos...8&postcount=55

The page from the Pilot's Notes is from June 1940. Spitfire II entered service on 13 August 1940.

[Kurfürst]

Originally Posted by 41Sqn_Banks

The use is reported on:
- 21 August 1940 http://forum.1cpublishing.eu/showpos...postcount=1441

Only mentions "emergency boost", at 4000 feet, does not specify boost used/obtainable.

- 2 and 30 November 1940 http://forum.1cpublishing.eu/showpos...8&postcount=55

Only mentions "boost cut-out", at 4500 feet, does not specify boost used/obtainable.

The page from the Pilot's Notes is from June 1940. Spitfire II entered service on 13 August 1940.

And the point is?

+12 lbs boost was only usable for take off and at low altitudes, and it fell of rapidly, in contrast to Spitfire I pilot notes which notes its effective up to rated altitude. There was no 'two different' sytems on the Spitfire II during BoB.

See:

[41Sqn_Banks]

Originally Posted by Kurfürst

There was no 'two different' sytems on the Spitfire II during BoB.

AP 1565B, Vol I, Section 8 was issued in August 1940 and mentions the "two different" systems. "6. The quadrant plate has a ... gate for the throttle lever in the take-off position". And in paragraph 7 mentions that the "red-painted thumb lever can be pushed forward in emergency".

[JtD]

+12 lbs boost was only usable for take off and at low altitudes, and it fell of rapidly, in contrast to Spitfire I pilot notes which notes its effective up to rated altitude.

Now how would they technically do that, make the boost of 12" drop off quickly instead of having it follow the outside pressure? What did the automatic boost control cut out do on the Spitfire II if not disable automatic boost control?

To my understanding (please correct me) of the pilot's notes page posted:

During take-off EITHER 3000 rpm OR 12 lbs boost + 2270 rpm up to 1000ft alt or for 3 mins ?????? (which indicates that 12 lbs boost could be used beyond 1000ft but only for 3 mins, but at lower rpm???)

30 min climb: max boost 9 lbs + 2850 rpm

cruising 7 lbs + 2650 rpm normal mixture
cruising 3 3/4 lbs +2650 weak mixture (fuel saving)

all out : 9lbs + 3000 rpm for 5 min

max dive for 20 sec: 9 lbs + 3600 rpm (cooking your engine quickly I imagine)