AH Spitfire Mk V vs AH 190 A5 Tests

[Nashwan]

Wilbus, you might be interested in  this post on Butch2k's board:

http://pub131.ezboard.com/fallboutwarfarefrm31.showMessage?topicID=779.topic

Apologies if it's stuff you've already got.

[Wilbus]

Exelent Nash! Thanks!

Also note that the 190 Outaccelerates both the Spit 9 and P38 F in dives without trouble.

[MANDOBLE]

Originally posted by Nashwan
http://pub131.ezboard.com/fallboutwarfarefrm31.showMessage?topicID=779.topic

Is that link Scifi? Or is AH Scifi?

[Neil Stirling]

I found this today.

[Wilbus]

1,35 ata = 4,5 lbs/sq.inch???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????

[Nashwan]

The British way of measuring boost pressure was to give the figure above sea level air pressure.

So to convert ata to lbs boost, subtract 1 from the ata, then multiply.

The 18lbs boost talked of in Spits was actually almost 33 lbs in absolute pressure, 18lbs above sea level atmospheric pressure.

18lbs in British terminology = 33 lbs in absolute pressure = 66 in hg = 2.22 ata (all approx)


Mandoble, what do you mean?

[Nashwan]

Good info Neil. Wasn't the Spit V rated at at least 12lbs by the time of this test? Are the Spit figures simply old A&AEE figures, rather than a new test alongside the 190?

[Wilbus]

Nashwan, the Spit 5 had 12 lbs with WEP. The Speed tests were made with WEP and the climb tests were made with military, 9 lbs for the spit they had at the time.

Nash, check the chart, it says the 190 A3 was tested at 1.35 ata. It also says that "Note: 1,35 ata = 4,5 lb./sq.in. Boost"

If this is correct, and as they write nothing else about it. It means the 190 was infact used at 4,5 lb/sq.in and the Spit at 9 lb/sq.in.

WHat have I missunderstood here?

[Urchin]

On the bottom chart in the link, there is a column with the weights of the various models.  

Next to 190A-5, the weight is listed as 9,480 pounds.

Next to the 190A-3 (the one tested in the test Wilbuz is quoting), the weight is listed as 8,377.  

What would cause the difference in weight of 1,100 pounds?  That could very well be why our 190A-5 doesn't accelerate as well as that 190A-3 did in the test.

Of course, in the AH help file it gives the 190A-5's weight as 8,583... now I'm rather confused.

[Naudet]

Urchin that 9xxx lbs for the A5 is fully loaded weight, including external ordance.

from my sources the weight differences between A3 and A5 are "nonexistant", to my own surprise i also found some data giving the A5 a lower "empty weight" than the A3.

[Nashwan]

Nash, check the chart, it says the 190 A3 was tested at 1.35 ata. It also says that "Note: 1,35 ata = 4,5 lb./sq.in. Boost"

If this is correct, and as they write nothing else about it. It means the 190 was infact used at 4,5 lb/sq.in and the Spit at 9 lb/sq.in.

WHat have I missunderstood here?

As I understand it, the 190 A3 was designed to run at 1.42 ata max. In service, it caused trouble, and they were restricted to 1.35 ata max (possibly 1.3 ata, I am not 100% sure)

All the other ratings were lowered as well (eg, max continuous from 1.35 to 1.28 or 1.3, again I am not 100% sure)

So, when the RAE tested the captured 190 at 1.42 ata it caused engine trouble. At the time, the RAE knew the plane had been derated, but ran it at the higher rating anyway. I remember seeing an old story, where it was claimed the 190s had been derated because their margin of superiority over the Spit V was so great, they could be run at lower settings to preserve engine life, and still not be under threat. Perhaps that was the thinking at the time, and so they ran the 190 at 1.42 ata, thinking derating would be reversed when the Spit IX came along.

Anyway, back to the point.

The RAF ran the 190 at 1.42 ata. According to this report, they also tested it at the derated figures, 1.35 ata max, 1.28 climbing power.

However, they have compared it to a Spit V at 9lbs boost, which is climbing power, but not WEP. I just wondered why.

[Wilbus]

CC but the chart says that 1,35 ata = 4,5 lbs boost which means that the climb test against spit 5 was done with the 190 flying with HALF the boost of the Spit.

[Nashwan]

Different planes, different boost.

The 109 used anywhere up to 1.8 ata with 97 octane fuel, with MW 50 as well it could go up to 1.98 ata.

The Spitfire used up to 2.25 ata on 100 octane fuel, with 100/150, which was comparable to 97 octane + MW50, the Spit could go up to 2.7 ata.

The Tempest could go to 1.76 ata on 100 octane, 1.9 on 150 octane.

Why such differences I don't know. I don't know much about engines.

I'd like an explanation on why such huge diffferences in manifold pressure. Why would a Sabre suffer detonation above 11lbs boost, whilst a Merlin or Griffon could run 18lbs boost without detonation?

BTW, 4.5 lbs boost is half the boost increase of 9lbs boost, but not half the actual manifold pressure.

4.5lbs + standard sea level air pressure is about 19lbs manifold pressure. 9lbs + sea level pressure is about 23.5lbs manifold pressure, which no longer looks such a huge difference.

The 190 A3 could run a maximum of 4.5lbs boost pressure safely, and that's what this doc from Neil shows. The Spitfire V could run 12lbs safely, possibly as much as 16lbs, so it's strange that the Spit was tested at less than max boost, with the 190 at max boost.

[Wilbus]

The Spit 5 had WEP at 12 boost. It was tested at 12 boost during speed runs only, speed runs for 190 was tested at 1,42 ata.

However, this 19lbs vs 23,5 lbs throws new light over this. All spit people seem to think the Spit was run at much less boost then the 190 which in that case is very wrong.

[Neil Stirling]

Nash, the Spit V was able to use +12lbs boost from the date of its entry into service, this was intially used for take off. Boost was increased to +16lbs in mid 1942.
Neil.