I Want my 4.09 Spit FM's back.........

[Fenrir]

Originally Posted by EJGr.Ost_Caspar

It seems as you are guessing. Manual clearly sais 170mph lightweight, up to 200mph loaden. Spitfire is a warplane, I don't think, manual were written for flying on sundays-tours.

If you find valuable references for your estimations, also for Mk.VIII/IX etc., then we would be happy to make it that way.

With all due respect caspar, and I respect you TD guys enormously, I get the feeling you're being facetious, when all I'm trying to do is help you guys get the Spits as accurate as possible.

The fact is that 170mph at 1800rpm is MAXIMUM ECONOMY CRUISE: used for extracting every last mile from the petrol tank at the expense of speed and being able to to accelerate quickly. You would fly at these settings for long range ferry flights, or on the initial part of a long range combat mission in areas where enemy air interception is negligible. You couldn't cruise in a combat area in that state:

To quote Tom Neil in 'Spitfire: From The Cockpit' ISBN 0-7110-1918-5, p 40:

"...It was a very odd chap indeed who chose to roam about over enemy territory with his engine operating at it's most economical setting! Except on navigation or reinforcement flights, it invariably became necessary to use the engine at wide throttle openings..."


From Spitfire In Action, ISBN 1-85648-015- 1, Dr Alfred Price p.192 Chapter 26 Correct Engine handling - Key to Survival

"In August 1942: the Air Tactics department at the Air Ministry issued the document which follows, as a guide to Spitfire pilots on the optimum engine settings to use when flying over enemy territory. Long range sorties had to be planned to meet the diverging requirements of fuel economy, and the need to maintain the highest possible cruising speed in areas where formations were liable to to encounter enemy fighters. If the Spitfires were 'bounced' while flying at low speed it could take up to two minutes for them to accelerate to maximum speed during which time they were extremely vulnerable. To reduce the risks while over enemy territory formation leaders were advised to cruise at speeds considerably higher than those for optimum fuel consumption.... at 10000ft.... maximum continuous cruising speed 331 (True) [thats 295 IAS - Fenrir] with +6lb boost and 2650rpm, consumption was 70gal/hr.

Memorandum:

HOW TO MAKE FULL USE OF THE PERFORMANCE OF THE SPITFIRE V, VI AND IX <-[HEY! Will you look at that! Fenrir]

1. This memorandum is intended to bring to the notice of all concerned the necessity of making full use of the power available in our Spitfire aircraft. It applies equally, in principle, to all our fighter aircraft operating against an enemy whose performance is equal or superior to our own.

2. At the present stage of the war the enemy in France is equipped with the FW 190, a fighter with an excellent rate of climb and good acceleration. To defeat this aircraft and to avoid casualties on our side, our aircraft must fly as fast as possible whenever they are in the combat zone.

3. In the past pilots have been told to fly at low rpm and high boost to economise in petrol. All pilots must know the correct rpm and boost at which to fly to obtain the longest duration of flight or range; a Table at appendix 'A' gives the various durations at different adjustments of rpm and throttle for the Spitfire VB & VC (Merlin 45 and 46).

4. Wings must still fly at the most economical rpm when they are flying under the enmy RDF [radar] screens but it is essential, as soon as they are liable to be detected, that they open up to maximum power for formation flying.

5. The acceleration of the Spitfire is relatively poor. It is therefore dangerous to cruise at say +2 boost and 1900rpm when the Hun is about because the time taken in accelerating to maximum speed will allow him quickly into firing range.

6. 7. & 8. - [tho of passing interest are somewhat superfluous for our argument - Fenrir]"

You noticed the figures I posted for the Mk V? These are the recommended settings from this document

Now extrapolate the fact that the Mk IX was a Mk V airframe with the Merlin 60 series engine.

Why would you give an airframe a more powerful engine, with it's accompanying effect on cruising speeds and hamstring it by giving it a nominal cruising speed of 170mph, when all operations before that point, prove that combat cruise is only safe around or above 230?

Caspar, we are both interpreting data, neither of us has a definitive statement which will read "The aileron neutral trim speed of a Mk (x) Spitfire is xxxxx" - and more's the pity.

Your marker is the max economical cruise speed.

I'm a fighter pilot at heart which means when I fly 400+ mph fighter plane, designed to fight other enemy aircraft I personally would want it aileron neutral trimmed within the speed range of which I am fighting so that gunnery, and flight characteristics are least affected. You said it best:

Spitfire is a warplane, I don't think, manual were written for flying on sundays-tours.

I couldn't give two hoots if f I've got to fly one wing low when ambling about on a long range navigational ex, or ferry flight, cos it's not an area of the flight envelope I'll spend much time in. Does no-one else feel the same?

BTW: Spitfires didn't have fixed trim tabs as such. I got told, that they used textile patches on the ailerons, but I've seen no proove for it yet.

See my earlier post on how Spitfire ailerons were trimmed on the ground.

Maybe we should also include the issue with the bending wingtips due too high aileron input and thus leading to reverse roll action? Now that would be fun!

I have no source for this, first I've heard. What's your evidence?

Between one guy who has the nothing but the fidelity of this simulation in mind to another, will you please consider my argument and in the meantime I'll see what I can do regarding some extra research? I'll see if I can contact the BBMF for clarification on aileron neutral rpm/speed settings.

Regards, Caspar, and thanks for your continuing work on the Il-2 series.