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PostPosted: Sat Mar 26, 2011 6:38 am 
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Airman First Class

Joined: Sat Feb 19, 2005 8:25 am
Posts: 75
HI!

I downloaded and checked your Spitfire Manual. It is great thing. Very detailed info like from RL manual.

Beeing little in topic i have some notices about your Spitfire MK1 performance data.


Firstly your maximum speeds at WEP ( +12 lbs boost preassure) are totaly wrong. Your speeds are way too fast.

Here you have RL data for Spitfire MK1 Merlin III ( both at +6lbs and +12 lbs emergency power):

Image


Here is good site about Spitfire performacne:

http://www.spitfireperformance.com/spit1vrs109e.html


Also i think that Spitfire MK1 with MErlin III using 100 octan fuel had different power settings - the same like Spitfire MK II with Merlin XII engine :
+ 9 lbs - nomial power ( climb )
+12 lbs - emergency ( take off) power .

+6 1/2 lbs was used as nominal power only with 87 fuel octan settings with MErlin III.


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PostPosted: Sat Mar 26, 2011 8:57 am 
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Joined: Mon Oct 25, 2010 3:28 pm
Posts: 166
Launch the Darryl
:lol:






.

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PostPosted: Sat Mar 26, 2011 12:50 pm 
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A2A Spitfire Crew Chief
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Location: The South West of the large island off the north coast of Tasmania
G'day

EDIT..are you talking about just the manual, or the performance....I do see a spot in the manual which lists 410mph...THAT is a typo, the model definitely will NOT perform to that.....?

Firstly, the speeds vary GREATLY depending on equipment, airscrew, weights and individual aircraft. If you must quote figures, make sure you quote all of the many different figures obtained in Mk I tests, and sources which were used in making this model, not one particular test set.

You will notice that your report is dated 25/8/1941 .... 15 months AFTER the modelling of the A2A Spitfire Mk I, have you taken THAT into account?.

Also, is your statement based on indicated, true, or calibrated airspeed?

Which are the basis for the figures in the table ?

What AUW was used, what airscrew? A simple polish of an aircraft could add up to 5mph. All of these things were considered.

What drag coefficient have you used in interpreting the graph you present?

Was the test aircraft armed and loaded to combat weight? Which was yours?

What were your compression ratios during your tests, what were your average temperatures? What was the condition of the engine when you finished your tests?

Are you aware that "all out level" and Combat Concession are not the same thing? (WEP is a completely anachronistic term, by the way and was used in the manual, as was "propellor, purely for "comfort" of modern readers.)

You may wish to reconsider using phrases such as "totally wrong" on the basis of one test graph. I would say that anyone would be very lucky to be able to state DEFINITE speeds and say that the model is totally wrong. After thirty years of research the best I can do is to make approximations on individual aircraft serials. [EDIT...as above, there is a SINGLE speed in the manual which is a typo]



Secondly, the normal operating boost maximum of the Merlin III was NOT increased to 9lbs at any stage pre or during battle of Britain.

Which page of the Merlin III manual are you referencing for your suggestion that it was 9lbs. per sq. in.?

Or which version of the Mk I Pilot's Notes ammended to which date, lists +9 as the maximum permissible boost for normal operations?

I have not found anything to suggest it was increased to 9lbs after that date but it is irrelevant in any case as the Mk I is modelled at or around March-May 1940. In fact the combat concession to +12 was, in the opinion of Dowding, widely misused and overused. It drastically reduced engine life and was cause for concern. The Merlin XII was specifically strengthened to allow 9lbs NORMAL operating maximum. Placards from wrecks dug dating from BoB and earlier clearly show these limitations.

Spitfire Performance was widely used in making the model, as were M&S, Dr Price, Wotjek (none of whom require any introduction) Spitfire performance and a score of others.

I am interested to see what detailed figures you achieved with the model, as i can not make it perform in any maner which significantly departs from that which would be expected given all the test data and all the published figures.


regards


Darryl

("launch"?? Now THAT is harsh :lol: :lol: )



EDIT..this post has been edited where noted...for some reason the "edit" tag does not show up....strange...

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PostPosted: Sun Mar 27, 2011 5:25 am 
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Airman First Class

Joined: Sat Feb 19, 2005 8:25 am
Posts: 75
HI!

I want to say that you make good work with Spitfire MK1 for FSX - very deatailed etc. But when i checked your manual i just notice wrong data for maximum speeds. Spitfire MK1 never was such fast.

In manual you claimed ( page 26):

Sea level speed ( Emergency Power) - 340 mph TAS ( 547 km/h)

Top speed ( Emergency Power) at 20 000 ft - 410 mph TAS ( 660 km/h).


Such speeds are rather for Spitfire Mark IX with Merlin 66 engine not for SPitfire Mk1 Merlin III +12 lbs. It is huge error.


The Royal Aircraft Establishment (RAE) obtained 314 mph (TAS) at sea level and 359 mph (TAS) at a full throttle height of 11,500 feet using +12 lbs/sq.in. boost.


I dont know how it is in game - how maximum speeds reach your Spitfire but clearly in your manual it is wrong.

These speed chart which i posted is for Spitfire MK1 Merlin III with Constant Speed Propeller Unit at + 6 1/2 boost and also emergency +12 lbs.

Surly Spitfire MK1 with different equipment like 2 stage prop pitch , 2 blade prop and with 87 octan fuel will have different performance.

Here you have very good data for different SPitfires MK1 types:

http://www.spitfireperformance.com/spitfire-I.html

http://www.spitfireperformance.com/spit1vrs109e.html

It is very good site for performacne of these plane with RL data.


About Merlin III engine and new power settings look here for these document:

Image

As you see with 100 Octan fuel Merlin III had similar power settings to Merlin XII engine.


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PostPosted: Sun Mar 27, 2011 8:04 am 
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A2A Spitfire Crew Chief
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Joined: Tue Jul 29, 2008 11:41 pm
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Location: The South West of the large island off the north coast of Tasmania
G'day, and thanks.

Agreed, the 410 figure (actually should be 408 for a Mk IX) is a typo, as stated.

The Spitfire Performance site was extensively consulted, as I have also said...so pointing us towards it as "very good data" is a bit redundant!

The majority of Spitfire I testing at RAE etc was done pre 12 lb boost.You need to be very careful when analysing tests to match conditions to dates. Most tests done early were only at 6 1/4 and LOW weights, making those aircraft (March 1940) much faster. There was a steady drop off in speed as the marque progressed and the Mk II was slower again. What changed (and what was MUCH more important) was the climb rate.

2 pitch airscrews gave faster speeds than ROTOL (much lighter) but the climb was inferior. Given that climb to altitude was the main problem, the heavier props won out even though they delivered lower speeds.

The last page is interesting. What date is that from? Feb 1940? If that document refers to experimental data for the early conversions to Merlin XII, that may explain it. That is in fact around when the XII was being developed and the higher horsepower was being dragged out of what BECAME the XII. Later Merlin III engines were strengthened and modified effectively turning them into Merlin XII standard. I suspect THAT is the activity from which your page comes. But certainly the performance in the field at the time the Mk I is modelled is set out clearly and consistently in the pilot's notes. The Mk I is 6 1/4 used as a basis and in fact was still used up to 19 March 1940.

As stated, the Spit MK I is modelled as at March - May 1940...NOT some later date and certainly BOTH copies of the Mk I pilot's Notes which I have (and which DO date from that time) list 6 1/4 only. As does the maintenance manual for the Merlin II and III for the early war period.

Out of interest, tests of airscrews in November 1939 delivered 296mph at sea level and 304 at 2000ft with the DeH 20 PCP. The extra 30-40 mph given by 12 lb then gives the 340mph as it is correctly stated in the manual. As said, the ONLY figure which is wrong IS the 410mph. That is a typo and the MODEL does NOT do that. On a good day the model delivers around 320 to 340 "calibrated" as a sea level combat boosted top speed...exactly as it should.

Early tests showed significantly higher speeds at low level and when an extra 30 - 40 MPH is added to those tests for +12 at lower weights etc, the model performs pretty much spot on.

regards


Darryl

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PostPosted: Sun Mar 27, 2011 11:18 am 
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Airman First Class

Joined: Sat Feb 19, 2005 8:25 am
Posts: 75
Sry but a cant agree that any Spitfire MK1 ( with or without aditional armour, with DH or Rotol ) could reach 340 mph TAS at sea level. Such speed was even not possible to achive by Spitfire Mark IX Merlin 66 in 1943 year which had much more horsepower (1700 HP) and more efficent prop. Spitfire Mark IX Merlin 66 reached 335 mph (540 km/h) at sea level.

Sea level speeds for Spifrire MK1 at 12 lbs was never better then 500- 505 km/h ( 310-314 mph).

It is true that 2 pitch or DH prop could be little faster then Rotol Spitfires at higher alts but difference was only a few mph never such hugh.

http://www.spitfireperformance.com/n3171.html


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PostPosted: Sun Mar 27, 2011 11:57 am 
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Senior Airman

Joined: Mon Oct 25, 2010 3:28 pm
Posts: 166
out of curiosity I took my MkI for a spin after setting the weather to 15 deg C. and no wind.
I got a true airspeed of around 300 at sea level and 350 at 20,000 feet.
I took off with around half fuel, with ammo and the DH prop.

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PostPosted: Sun Mar 27, 2011 2:21 pm 
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Aviation Writer and Pilot

Joined: Tue Feb 22, 2005 1:29 pm
Posts: 357
I agree with you.

In recent tests which I flew, on a standard day, 200’ASL, with no wind, the Spit Ia, at 5,338 lbs., DH two-position propeller, flat canopy, radiator shutter on red diamond, 87 octane petrol, boost +12, 2,900 r.p.m., did approximately 310 m.p.h.; and the Spit IIa on the same day, at 3,489 lbs., Rotol constant-speed propeller, blown canopy, radiator shutter on red diamond, 100 octane petrol, boost +12, r.p.m., 2,900 r.p.m., did approximately 315 m.p.h. Both aeroplanes’ engines heated up very quickly during the speed runs and had to be very tenderly flown back to base to prevent overheating before shutdown.

In both aeroplanes prior to the tests the engines were in excellent condition, less than 10 hours, with cylinder compression readings all above 80 lbs. Afterwards, they were similarly excellent with slightly lower compression readings.

“Optimistic” performance reports in official documents were not uncommon then, nor are they now. When there is an active and aggressive adversary to impress and hopefully cow a bit, the degree of official “optimism” is likely to grow. The contents of our documents reflect what the official word was in and around June 1940. No doubt the R.A.F. pilots of that time found the same practical discrepancies with them as have you and I.

Just another example of how A2A brings to you accurate and authentic simulation of real-world experiences.

Mitchell


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PostPosted: Sun Mar 27, 2011 8:23 pm 
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A2A Spitfire Crew Chief
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Joined: Tue Jul 29, 2008 11:41 pm
Posts: 5281
Location: The South West of the large island off the north coast of Tasmania
Mitchell wrote:
, 87 octane petrol, boost +12, 2,900 r.p.m.,


Oh dear!!!


:D :wink:


Darryl

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PostPosted: Mon Mar 28, 2011 1:41 am 
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Aviation Writer and Pilot

Joined: Tue Feb 22, 2005 1:29 pm
Posts: 357
Darryl,

Yes my friend, I know that I was pushing the old girl a bit, maybe more than a bit; however I was trying to replicate a balls-out combat situation where a pilot might be either desperately chasing or desperately running from a determined adversary at sea level. Such things, I understand, occurred from time to time.

In that kind of situation, I am sure that pilot’s manual conventions and niceties, as well as thoughts about engine preservation went bloody well by the boards. Of course, neither I, nor any sane modern pilot would ever do this in a real, vintage, preserved Spit today, nor would such be necessary; but our herein simulator environment permits such blasphemous indiscretions if only for the purpose of our further illumination and enlightenment.

Your “Oh dear!!!” is, however, well-taken; and I agree with you and do not recommend that our girl be ordinarily abused in such fashion.

As our esteemed Spitfire Crew Chief, your concern is eminently appropriate; and, as a mere Chief Pilot, I bow to your just chastisement.

My bad.

Mitchell


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PostPosted: Mon Mar 28, 2011 2:55 am 
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A2A Spitfire Crew Chief
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Joined: Tue Jul 29, 2008 11:41 pm
Posts: 5281
Location: The South West of the large island off the north coast of Tasmania
Well, I suppose as long as the kiddies are in bed by the time you do it, it is OK :lol:

The rather firm letter from Dowding to the Groups and Sector Stations re "overboost" does indeed show that "preservation" was better than cure, at least as far as pilots were concerned. One needs only to read some period Combat Reports to see that the niceties of engine life were very much not in the thoughts of pilots during combat. The "slightest excuse" being seen to justify "pulling the tit".

I have never been able to ascertain exactly what the procedure was for the throttle quadrant when 100 Octane was able to be used but 87 was in fact put in the tank. I suspect that the ABCO-O was wired semi-permenantly to "OFF" rather than the more usually sheer wire. I have seen several modern birds where this is the case.

I have also seen "100 Octane Only" placarded. The modifications to the III to allow the use of 100 were not great and were largely concerned with physically allowing higher boost rather than too much strengthening of the engine. A different Cylinder Top Joint was however used.

The whole issue of timing of introduction, consistency of supply and issue to Squadrons is a little vexxed in any case.

...and you know we Crew Chiefs, we own the aircraft but are quite amenable to loaning it to a pilot once in a while...to Chief Pilots even more so..... :D

Darryl

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PostPosted: Mon Mar 28, 2011 3:14 am 
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Aviation Writer and Pilot

Joined: Tue Feb 22, 2005 1:29 pm
Posts: 357
Thanks Chief.

Mitchell


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PostPosted: Sat Jun 18, 2011 2:12 pm 
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Technical Sergeant

Joined: Wed Feb 20, 2008 8:19 pm
Posts: 531
Location: Chester, NY. USA
I learned so much that my attention span ran out, nice verks


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PostPosted: Sun Jun 19, 2011 1:10 am 
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Aviation Writer and Pilot

Joined: Tue Feb 22, 2005 1:29 pm
Posts: 357
Toonsis,

Thanks.

You've got to get larger attention span tanks.

Mitchell


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PostPosted: Sun Jun 19, 2011 8:30 am 
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Posts: 531
Location: Chester, NY. USA
Its just one step at a time and practice practice practice. I take a few written notes right away on what I did right and what I still need to work on. I call it my debrief


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