Spitfire Mk.XIV vs P-51D Mustang

[wh1skea]

I say slap a RR Griffon in the Mustang, then see how the two compare.

[Soren]

That's a serious weight increase.

[delcyros]

Pretty good points drgondog. Thanks for sharing them!

[kool kitty89]

Anyway, the V-1650-9 with water injection had power output similar to the Griffon.

[Kurfürst]

Originally Posted by drgondog

So to your points - the 51 cruises at about 235 -250 for best specific fuel consumption at 45 gph and ~ 46" Hg at 2500.. if unmolested, the P-51 "full wing tanks" of 184 gallons is LESS than 1/2 fuel for take off condition - so do the math? The 51 could drop tanks, engage for 10-15 minutes at 240gph over Berlin and still have enough to fly 600 miles back to England

The Luftwaffe interceptors were probably at 2/3 fuel remaining and only had about 40minutes high speed cruise plus 10 minutes of combat left by the time their day started with a fight... and lucky to stay in the air another 100 miles.

Re: LW interceptors, its quite unlikely. Their droptanks replenished the main tank, so when they dropped them, they were on full internal (and did not have to bother with switching between tanks as a bonus). Frankly its quite unlikely. And the main tank, either full or at 2/3s would be enough for a lot more than just 100 miles as I reckon.

I comparison from a British report:

[kool kitty89]

40 min at high speed cruise should give ~200 mi.

[Hop]

Note the different speeds used for the different aircraft in the table Kurfurst posted. The 109s are at significantly lower speeds than the others:

109G - 615 miles in 3.1 hours - 198 mph
LF IX - 420 miles in 1.6 hours - 263 mph
XIV - 500 miles in 1.8 hours - 278 mph
Temp - 760 miles in 3 hours - 253 mph
Must - 890 miles in 3.6 hours - 247 mph

[claidemore]

Originally Posted by Hop

Note the different speeds used for the different aircraft in the table Kurfurst posted. The 109s are at significantly lower speeds than the others:

109G - 615 miles in 3.1 hours - 198 mph
LF IX - 420 miles in 1.6 hours - 263 mph
XIV - 500 miles in 1.8 hours - 278 mph
Temp - 760 miles in 3 hours - 253 mph
Must - 890 miles in 3.6 hours - 247 mph

Also note the difference for fast cruising:

109G - 450 miles in 1.4 hours =321 mph
Spit IX -365 miles in 1.1 hours =331 mph
Spit XIV-375 miles in 1.0 hours =375 mph
Tempest-535 miles in 1.4 hours =382 mph
Must III - 690 miles in 1.8 hours=383 mph

[KrazyKraut]

They just reflect the 109 G(-6?)'s generally slower pace compared to these relatively newer fighters (sans MkIX). Being a British report they may possibly stem from the captured G-2. Considering the argument was about who could stay how long in the fight in a escort vs interceptor scenario, the difference in fast cruise speed is irrelevant. The 109s just had to intercept the bombers afterall, if they reach them, the escort didn't have to be "caught".

[claidemore]

Originally Posted by KrazyKraut

They just reflect the 109 G(-6?)'s generally slower pace compared to these relatively newer fighters (sans MkIX). Being a British report they may possibly stem from the captured G-2. Considering the argument was about who could stay how long in the fight in a escort vs interceptor scenario, the difference in fast cruise speed is irrelevant. The 109s just had to intercept the bombers afterall, if they reach them, the escort didn't have to be "caught".

But... the escorts could 'catch' the interceptors!

Also, since the 109 shown in that chart had drop tanks, it's more likely the G6 than G2 afaik Black 6 was not fitted with drop tanks during trials. The Mustang III as well as the Spit IX would be contemporary with the 109G6 as far as production and combat use.

[davparlr]

After quite a bit of research and pondering I think I have determined reasonable weight and performance for the P-51B post installation of the 85 gallon fuselage (extended range) tank.

First, let me define the fighter weight of the P-51 (both B and D). P-51B fighter weight is the aircraft fully loaded with ammo, pilot, liquids (not fuel), etc., plus fuel for full wing tanks, about 180 gallons, roughly 1100 lbs. This is equivalent to a fully fueled P-51A or P-51B pre-fuselage tank. It is also equivalent to the tested values of the Fw aircraft (previous discussions indicated Ta-152H tested fighter weight included one half fuel weight or about 148 gallons). I am not sure of the fuel quantity of the tested Fw-190D-9, but I believe its internal fuel capacity is 169 gallons. So, for comparison purposes, fighter weight is an equivalent weight.

The initial fighter weight that I arrived at, 9077 lbs, I believe was the Manufacturing data for the P-51B without the center fuselage tank installed, pre-P-51B-7 ((I think). Army testing of the P-51B, with fuselage tank installed, defined the fighter weight as 9205 lbs

According to wwiiaircraftperformance, two test references show,

“….at a take-off weight of 9205 lbs. This loading corresponds to the average P-51B combat weight with full oil, 180 gallons of fuel and specified armament and ammunition.”

“All test were flown… 9335 lbs… The weight flown was 125 lbs. heavier than combat weight…”

Adding to the confusion, there were two test reports on wwiiaircraftperformance of climb for the P-51B using 75” boost, one at a test weight of 9680 lbs, and one at 9335 lb. I could not find any differences between the data on the two charts. After reading the reports, I believe that the test reflecting 9335 lbs is the correct chart, and the conservative one. Using this chart, and others, and correcting for combat weight (approximately 100 ft/min), I have generated the following performance data for the P-51B using 100/150 (44-1) fuel, at combat weight. A more accurate comparison with the Fw-190D-9 follows.

It must be noted here that this data, like all data obtained through analysis and/or test (or thumb rule), has a certain error that always distorts any comparison. This error is unknown and has many variables. For example, to assume that an aircraft that a 100 ft/min tested/analyzed can actually out climb the other aircraft is risky at best but it does give a neighborhood of performance.

SL
P-51B
A/S 386 mph
Climb 4430 ft/min

Fw-190D
A/S 385 mph
Climb 4429 ft/min

5k
P-51B
A/S 410 mph
Climb 4420 ft/min

Fw-190D
A/S 405
Climb 4134 ft/min

10k
P-51B
A/S 420 mph
Climb 3900 ft/min

Fw-190D
A/S 413 mph
Climb 4134 ft/min

15k
P-51B
A/S 428 mph
Climb 3820 ft/min

Fw-190D
A/S 432 mph
Climb 3740 ft/min

20k
P-51B
A/S 440 mph
Climb 3200 ft/min

Fw-190D
A/S 426 mph
Climb 2992 ft/min

25k
P-51B
A/S 440 mph
Climb 2400 ft/min

Fw-190D
A/S 417 mph
Climb 2158 ft/min

30k
P-51B
A/S 429 mph
Climb rate 1700 ft/min

Fw-190D
A/S 406 mph
Climb 1476 ft/min

If you throw in the general statements that the Fw-190D could out-turn the P-51B, and the P-51B could out dive the Fw-190D, I think you can see that the performance of the two are, for all intents and purposes, equal up to 15k ft. Here, the ability of the pilot would be the determining factor.

Nearing 20k ft., the P-51B was gaining a significant amount of airspeed advantage and slight climb advantage, and, above that, this advantage increased. In this envelope, the P-51B pilot had more tools to work with.

General notes: Firepower of the Fw-190D-9 was much more substantial than the P-51B, along with better power loading (acceleration) at lower to medium altitudes. P-51B had lower wing loading (82% of the Fw-190D-9).

Notes on the P-51D with 75” boost. With a fighter weight about 400 lbs heavier than the P-51B, climb will be impacted about 250 ft/min more (roughly). Airspeed would be slightly less than the P-51B, mainly due to a slight increase in drag from the bubble canopy.

[drgondog]

[quote=Kurfürst;405129]Re: LW interceptors, its quite unlikely. Their droptanks replenished the main tank, so when they dropped them, they were on full internal (and did not have to bother with switching between tanks as a bonus). Frankly its quite unlikely. And the main tank, either full or at 2/3s would be enough for a lot more than just 100 miles as I reckon.

/QUOTE]

Kurfurst - I agree your points on the ranges for G's with tanks. Based on what I have seen of the late 1944 period much fewer missions were flown with external tanks so the scramble assembly and max climb to 30,000+ feet then high speed cruise to the directed intercept point would be accomplished on internal fuel.

My 'estimate' above was based on taking off, internal fuel, climb to altitude - fast cruise for 30-60 minutes - 15 minutes of emergency power - and speculate on what is left to go home with 20-30 minutes of reserve for landing - more if bad weather.

What are your thoughts based on the mission narratives and doctrine that you have observed?

[ponsford]

Originally Posted by davparlr

SL - Fw-190D -A/S 386 mph

That’s a bit generous davparlr for standard production aircraft in a condition approved and configured for operations

[davparlr]

Originally Posted by ponsford

That’s a bit generous davparlr for standard production aircraft in a condition approved and configured for operations

Data is off of Focke Wulf chart and I have no reason to doubt them. A/C probably was cleaned up somewhat, like most A/C in test.

[kool kitty89]

On the cruise speed, it's a bit relative. Both the Spit variants and the 109 should get maximum range when cruising at ~180-200 mph. (of course, altitude would affect the speeds as well)

So, technically the Spitfires in that chart are not demonstrating their maximum range. (even the P-51 could go a bit farther when at minimum cruising around 200 mph ~400 hp, though the difference was much less dramatic due to the low drag airframe)

Somthing to note is that at long range cruise in clean configuration at 10,000 ft, the P-38J was only going at ~175 mph. (which dropped to ~150-160 mph with tanks, at escort altitude it should be more around 190-200 mph though)