Spitfire 14 is porked

[Wilbus]

None the less, sitting on the runway to 20K it is still almost a minute too slow

Please Angus, from where do you get your numbers? A source please, as it is now the only "porked" thing about it is the climb rate, this could very likely be because of the lack of a fuel tank but it does not (atleast not from the numbers I and others have posted) climb too slow. It actually climbs 500ft/min too fast at the deck.

Source?

[Nashwan]

Given that most of the report is calculations based on some flight tests with pre-determined numbers for "satisfactory results",

The "pre determined numbers" are the permitted coolant temperatures."Satisfactory results" are temperatures lower than the permitted coolant temperatures.

Yep, it`s about 200 fpm worser than the Mk. IX, which cuts in very nicely with the decrease in climb rate with clipped models, suffering from the same wingload increase.

If you clip the wings of the Spit IX, you may get a wingloading increase to the same as a Spit VIII (I haven't checked), but of course you still have a higher power to weight ratio, which has far more effect on climb rate than wingloading, so you would still outclimb the Spit VIII.

Uhm, if a "normal" Spit could do ~4500 fpm, and increasing the boost would raise that by about 950 fpm (4500+950= 5450 fpm), than how could RR`s Spit be "underperforming at 5740 fpm?

Because the 4500+ figure is with rad flaps open. RRs test of JL165 was with rad flaps shut.

At Rollce-Royce`s test the "same underperforming Spit IX" was very close to it`s official specs at 399 mph max speed.

It was 397 mph, and that is lower than similar Spits. MA548, with an SU fuel pump instead of carb, did 411 mph. (The SU pump increased the speed of the Spit V by 5 mph). BS543 did 407mph, BS310 did 404mph.

With the same plane A&AEE mesured 389 mph as max speed, so clearly, for some reason, in the RR tests the plane was perfectly representative of an avarage spitfire.

Apart from being 5 - 10 mph slower than any other Spit IX, and having a climb rate 200 - 300 ft/min worse. (In the RR tests. By the time A&AEE tested it, it was 15 - 20 mph slower than other Spit IXs, and had a climb rate 500 ft/min worse.)

but as we know, late 109s had double the WEP time than Spits.

Do you have a cooling report on the 109? Because WEP time has no bearing on engine overheating. The Spit cooling report shows that after 5 mins at 25 lbs boost in level flight, the coolant was still way below permitted temperatures, even with the rad flaps shut. Got the figures for the 109? How long it could run at 1.98 ata with rad flaps shut, half open, etc?

German tests at rechlin
109G1 no WEP, full load,no gonds, with takeoff roll. 20K 5 : 14

No takeoff roll. The Rechlin figures for the G1 show 47 seconds to 1000m, 1 min 35 secs to 2000m. That works out at an average of 21 m/s for both the 0-1 km stretch, and the 1 - 2km stretch.

Also, the G1 reached 6000m in 5:14, 20,000ft would be 5:20.

These figures were done at 30-min rating at 1.3ata, the maximum WEP would be 1.42ata for about 10% more power at all altitudes,

1.42 ata was forbidden on the DB605 from June 1942 until June 1943, by which time production of the 109G2 had stopped.

vs. your 6 : 34 min.

I get 4:55 vs the actual 5:20.

[Nashwan]

However I believe it could cruise faster without the engine overheating. I can't find the engine settings for cruise.
Maybe Nashwan or Karnak know it?

I don't know. The manual lists maximum continuous as 2400 rpm, 7lbs boost. It also lists a max 1 hr climbing limit of 2600 rpm, 9lbs boost.

Cruising implies a continuous rating to me, but wether it's the same as the max continuous figure above, I have no idea.

[GScholz]

Nashwan, I believe the coolant did not overheat when running on WEP (Spit and 109), but the piston heads and/or valves overheated. They would not be cooled at all except for the oil and excess fuel usage. The piston heads were designed to operate at high temps, but on WEP they would eventually overheat and could seize up the engine. The increase in coolant temp would be minimal, in fact what I have read is that the MW-50 and C3 injection used by the Germans actually reduced heat build-up since they had a heat dissipating/vaporizing effect. The 5 and 10 minute operational limit on the Spit and 109 is not dependent on coolant temp, but on the additional heat and stress on certain components of the engine.

EDIT: In AH this is simplified for all AC. All AC can run at MIL setting and max revs without running hot or damaging the engine, but in RL this was not so and different engines had different operational limits. AH does not model this AFAIK.

[Angus]

Hey Wilbus
My mistake. The test clock was apparently started after takeoff, as soon as the plane entered climbing speed. So, out Spit XIV is actually spot on with the plane registered at the fourthfightergroup website. If it is too fast climbing in some zones up to 20K, it must thereby also be too slow in others.
However, performance above 20K seems to fall short, but I will have to look at it better.
Hey Isengrim: where do you find that data? I sorely need more tables of all 109 variants, (also the 190 actually), so if you have a nice thread, please post.
oh, - " but as we know, late 109s had double the WEP time than Spits."
What WEP time did Spits have? I know of Spits being run on "panic boost" for up to 30 minutes without engine damage.
Well, wish we had a better engine modelling in AH anyway

[AmRaaM]

i own a spit14, and fly it regular. Best plane my money can buy.























mines slightly modified, has 26" wings.

[Angus]

Got any pics of that?
Must be kinda small though