SpitfireV speed at +12lbs.

[VooDoo]

In the pilot manuals of SpitV and SpitII this power setting described as "take-off", but SpitfireI pilots in BoB used it as combat. May be somebody have any info about max speed/climb figures on this power setting SpitfireV or SpitfireII ?

[Delirium]

::elbows Slack::    


  just kidding, but seriously, he can tell you whatever you want to know.

[VooDoo]

Didnt get it. My question is too complicated ? The answer is too secret ? Everebody know that SpitV has xxx mph at +12lbs ? Nobody understand that Im talking about ?

[Angus]

There were no Spit V's in the BoB. Spit II's,however.
I should have these figures somewhere,- will look them up for you.

[VooDoo]

"but SpitfireI pilots in BoB used it as combat" - clear ?

will look them up for you
Thank you .

[mw]

Your information about the Spit II is incorrect.  See
this page from the Spit II Pilot's Notes.  +12 was a 5 minute combat rating.  Spit V's were only limited to +12 takeoff for a short time, and were eventually cleared for +18 combat.  Top speeds/climb varies among the data sets and is  dependant primarily on aircraft configuration and fit and finish.

[VooDoo]

Originally posted by mw
Your information about the Spit II is incorrect.  See
this page from the Spit II Pilot's Notes.  +12 was a 5 minute combat rating.  Spit V's were only limited to +12 takeoff for a short time, and were eventually cleared for +18 combat.  Top speeds/climb varies among the data sets and is  dependant primarily on aircraft configuration and fit and finish.

No, my information IS correct. Its just not the only information exist .



The main question is about speed and climb of SpitV and SpitII at +12 boost. Not how this boost was named . But any info about clearing of a SpitV for using boost higher than +12 are always appreciated. If you know exact date - share it . Im interested mainly in 1941 produced and used aircrafts (SpitV) and mid-late 1940 (SpitII).

Conditions of the tested aircrafts are third question. Im interested in standart production aircrafts (VB and VC) with standart engines (Merlin 45) and standart armament (2x20+4x7).

[VooDoo]

As for Spitfire Performance Testing site - Ive digged it through already .

[Guppy35]

August 1942 Air Tactics department Air Ministry issued a document for Spitfire pilots regarding survivability with the 190s around

Part of it mentions:

"Spitfires are now modified to give +16 emergency boost.  It must be impressed upon pilots that this gives a great increase in speed under 21,500 feet and 18,250 feet for Merlin 46 and 45 respectively, and if used for combat only, there is no risk of engine failure"

another quote from it, "You can fly +16 boost and 3000 RPM without any danger of the engine blowing up, BUT, your consumption will be 150 gallons an hour."

Spit V Manual I have says +9 boost and 2850 RPM gave the maximum rate of climb.  Nothing about +12 boost though.

No specific speeds that I can find though, So I don't think this really answers your question

Dan/Slack

[HoHun]

Hi Voodoo,

>But any info about clearing of a SpitV for using boost higher than +12 are always appreciated.

That first step was an increase to +16 lbs/sqin that came along with the introduction of the Fw 190A.

According to Alfred Price' "A Spitfire - The Complete Fighting History", the Air Ministry issued a memorandum in August 1942 stating "Spitfires are now being modified to give +16 emergency boost." I'd say that dates it pretty well.

With regard to the Spitfire speed at +12 lbs/sq in, the easiest way to get an answer is to estimate it graphically.

Plot N.3171 speed from

http://www.fourthfightergroup.com/eagles/spit1.html

on graph paper. Then have a look at the full curve above full throttle height (18900 ft) and draw an extension in a smooth shape to 10900 ft.

+6.25 lbs/sqin has a full throttle height of 18900 ft, and +12 lbs/sqin is 8000 ft below that according to the Merlin III power chart here:

http://www.fourthfightergroup.com/eagles/merlin3curve.jpg

Note that absolute heights differ due to the ram effect changing the pressure.

Next, draw a line parallel to the straight line denoting +6.25 lbs/sqin low altitude speed from the freshly extended +12 lbs/10900 ft line down to sea level.

That's a quick, simple and reasonably accurate method of estimating a speed change resulting from a boost pressure change :-)

From just staring at the numbers, I'd say this will give you something like 362 mph @ 10900 ft and 311 mph @ sea level.

Regards,

Henning (HoHun)

[lasersailor184]

Not to sound too newbish, but what kind of acceleration difference are we talking at 12 - 16 lb's?

[hawker238]

Not to sound too newbish, but what the hell is everyone arguing about?

[VooDoo]

Hello HoHun !



It looks pretty similar to that you are talking about. Does it means that SpitV speed will be just 10 mph faster than SpitII ? 321 mph at sea level at +12 boost ?

[VooDoo]

Originally posted by Guppy35
Spit V Manual I have says +9 boost and 2850 RPM gave the maximum rate of climb.  Nothing about +12 boost though.

Dan/Slack

Yes it says . But Im pretty sure that climb at +16 boost will be a way faster than at +9 and 2850 RPM. So as at +12. The only problem - it will not work for an hour . +12 lbs and 3000 RPM is a MAX TAKE-OFF as said in PM.

[Angus]

Recommended to the max of 5 or 10 minutes, overboosting never the less was sometimes done for much longer, sometimes 30 minutes without ruining the engine. In such cases the engines were usually overhauled.