Escort Fighter Performance Comparison

[Geoffrey Sinclair]

Andrew Arthy posted the following charts from Luftwaffe Quartermaster reports at some stage, perhaps on this forum?

So the 600 Bf 109's lost are to all causes on operations, 502 to enemy action and 98 without enemy action. Bergström's total losses to enemy action is actually higher for the 109's, by 32 aircraft.

Luftwaffe Quartermaster
663 Bf109 and 252 Bf110 total all cause losses
600 Bf109 and 235 Bf110 lost on operations
502 Bf109 and 224 Bf110 lost to enemy action
Bergstrom 534 Bf109 and 196 Bf110 lost.

Battle of Britain Then and Now
586 Hurricanes and 364 Spitfires lost to all causes on both operations and non operations.
500 Hurricanes and 300 Spitfires in round terms, destroyed by enemy action on operations (including losses to Luftwaffe bomber fire) plus another 18 Spitfires and Hurricanes lost on the ground "enemy action" and 28 to unknown causes on operations.
Bergstrom 603 Hurricanes and 394 Spitfires lost.

What definition is Bergstrom using and should be used? I chose to compare his total to "total all causes losses on operations" as that was the closest match for the aircraft under discussion, the Bf110. Also Bergstrom's 1,300 confirmed Hurricane+Spitfire kills can be compared to the total of 1,000 Luftwaffe aircraft lost to enemy aircraft in the Battle of Britain Then and Now list.

 

[Milosh]

Luftwaffe Quarterly reports, German Order of Battle - Statistics as of Quarter Years, 1938-45

What is interesting is very few of the units were at Est. Strength in June and none in Sept.

 

[Zipper730]

The transcription for the Spitfire IX (cut away fuselage as modified in the U.K.), second and third lines should read 96+62?

Yeah, I just entered it haphazardly, but I reposted it correctly.

The next page in Air 19/286 is interesting, it dates the document to 7 September 1944 and states,

"3. The following progamme has been arranged:-
(i) Spitfire IX (now in production). 800 sets of tanks have been ordered for retrospective fitting and production of these tanks should commence in about 3 months' time. The modification will comprise replacing the existing 85 gallon main fuselage tank by a 96 gallon tank and fitting a 72 gallon self sealed tank in the fuselage behind the pilot.

(ii) Spitfire IX (cut away fuselage). This aircraft comes into production in about 4 months' time and it is hoped to embody the 96 gallon main tank and a 62 gallon rear fuselage tank in the production line from the outset. The cut away fuselage, which gives a considerably improved rear view, prevents the fitting of a 72 gallon tank."

According to that timetable, the 72-gallon aft-tank would have been put into operational service in early December, 1944, and the 62-gallon tank for the cut-away fuselage would be around early January, 1945.

The range figures in Air 19/286 are similar to the proposals from the first half of 1944 reported in AVIA 20/2030 and AIR 20/3312, see messages 228 and 229 in the Spitfire Combat Radius (range) evolution, limitations? topic

Do you have access to these historical documents? They sound like they'd be very interesting to read. I actually did transcribe much of what you wrote since it's nice to have the data handy (I am curious why some of the figures, such as the Spitfire Mk.VIII/Mk.21 had two ranges listed, since the fuel load was identical).

Was there any proposal to fit the Mustang with a 98 imperial gallon tank? That's the only way I get 346 gallons, unless they meant 246?

Also in AIR 19/286 the Spitfire LF.IXE with Merlin 66, maximum weak mixture cruise speed was 328 mph at 20,000 feet

I'm surprised the altitude figures were so low. I'm not an expert on the merlin 60 series, but we had versions that we had (V-1650-3/-7) had critical altitudes that were typically around 19000' (V-1650-7) to 24000' (V-1650-3) without ram, and with ram, you'd see around 24000' (V-1650-7), and 29400-29800' (V-1650-3) with ram compression. The Spitfire climbed faster than the P-51's did, so I'd figure they'd have had better AMPG up high.

 

[Stig1207]

Luftwaffe Quartermaster
663 Bf109 and 252 Bf110 total all cause losses
600 Bf109 and 235 Bf110 lost on operations
502 Bf109 and 224 Bf110 lost to enemy action
Bergstrom 534 Bf109 and 196 Bf110 lost.

Battle of Britain Then and Now
586 Hurricanes and 364 Spitfires lost to all causes on both operations and non operations.
500 Hurricanes and 300 Spitfires in round terms, destroyed by enemy action on operations (including losses to Luftwaffe bomber fire) plus another 18 Spitfires and Hurricanes lost on the ground "enemy action" and 28 to unknown causes on operations.
Bergstrom 603 Hurricanes and 394 Spitfires lost.

What definition is Bergstrom using and should be used? I chose to compare his total to "total all causes losses on operations" as that was the closest match for the aircraft under discussion, the Bf110. Also Bergstrom's 1,300 confirmed Hurricane+Spitfire kills can be compared to the total of 1,000 Luftwaffe aircraft lost to enemy aircraft in the Battle of Britain Then and Now list.

Looks to me that Bergstrôm is definitely using destroyed by enemy action for the Luftwaffe, while Fighter Command losses are losses to all causes, but I don't know where he gets his figures from. Odd that he has more 109's lost but less 110's by a similar number , +32 109's; -28 110's.
Otoh, his 1300 confirmed Hurricane + Spitfire kills compares well with the 1385 total Luftwaffe losses to enemy action from the Lw Quartermaster.

 

[drgondog]

Was there any proposal to fit the Mustang with a 98 imperial gallon tank? That's the only way I get 346 gallons, unless they meant 246?

No.

I'm surprised the altitude figures were so low. I'm not an expert on the merlin 60 series, but we had versions that we had (V-1650-3/-7) had critical altitudes that were typically around 19000' (V-1650-7) to 24000' (V-1650-3) without ram, and with ram, you'd see around 24000' (V-1650-7), and 29400-29800' (V-1650-3) with ram compression. The Spitfire climbed faster than the P-51's did, so I'd figure they'd have had better AMPG up high.

Climb is related to Excess Power and Wing Loading. Range is more dependent on specific fuel consumption per hour and combination of parasite and induced drag and wing loading. The Mustang and Spitfire, with same engine and boost and RPM and altitude, will always find the Mustang with more 'air miles per gallon' per relative Gross weight load out %.

 

[Geoffrey Sinclair]

Do you have access to these historical documents? They sound like they'd be very interesting to read. I actually did transcribe much of what you wrote since it's nice to have the data handy (I am curious why some of the figures, such as the Spitfire Mk.VIII/Mk.21 had two ranges listed, since the fuel load was identical).

Was there any proposal to fit the Mustang with a 98 imperial gallon tank? That's the only way I get 346 gallons, unless they meant 246?

I'm surprised the altitude figures were so low. I'm not an expert on the merlin 60 series, but we had versions that we had (V-1650-3/-7) had critical altitudes that were typically around 19000' (V-1650-7) to 24000' (V-1650-3) without ram, and with ram, you'd see around 24000' (V-1650-7), and 29400-29800' (V-1650-3) with ram compression. The Spitfire climbed faster than the P-51's did, so I'd figure they'd have had better AMPG up high.

I only have 25 pages from AVIA 20/3030 and 6 from Air 20/3312 as at the time I was only after what happened, not what might happen or proposed plans which make up the bulk of those files. Early in the war the RAF standard characteristics cruise height was 15,000 feet, that was changed to 20,000, the performance figures are meant to be standards for basic planning purposes, adjusted according to the mission. The idea Spitfires were retrofitted with the larger tanks helps explain the uncertainties about what capacity individual aircraft had. The two ranges listed are economic versus maximum weak mixture cruise.

Mustang 221 gallons internal 2x62.5 gallon external = 346 gallons

 

[EwenS]

I'm surprised the altitude figures were so low. I'm not an expert on the merlin 60 series, but we had versions that we had (V-1650-3/-7) had critical altitudes that were typically around 19000' (V-1650-7) to 24000' (V-1650-3) without ram, and with ram, you'd see around 24000' (V-1650-7), and 29400-29800' (V-1650-3) with ram compression. The Spitfire climbed faster than the P-51's did, so I'd figure they'd have had better AMPG up high.

The figures being quoted were for a Sptfire LF.IX with a Merlin 66.

The Merlin 66 was considered a"low altitude" engine. The F.IX got the Merlin 63 which had a higher altitude rating. The difference seems to lie in the superchargers with different rotor sizes and gearing ratios.

Merlin 63 11.5/10.1 rotor dia; 6.39/8.03 gear ratios. combat power low gear @ altitude 1,710 @ 8,500ft; combat power high gear 1,510 @ 21,000ft
Merlin 66 12.0/10.1 rotor dia; 5.79/7.06 gear ratios. combat power low gear @ altitude 1,705 @ 5,750ft; combat power high gear 1,580 @ 16,000ft

V-1650-3 12.0/10.1 rotor dia; 6.39/8.095 gear ratios. combat power low gear @ altitude 1,530 @ 15,750ft; combat power high gear 1,300 @ 26,500ft
V-1650-7 12.0/10.1 rotor dia; 5.80/7.34 gear ratios. combat power low gear @ altitude 1,705 @ 5,100ft; combat power high gear 1,300 @ 26,500ft

The V-1650-7 is often described as nearly the equivalent of the Merlin 66

 

[Zipper730]

I only have 25 pages from AVIA 20/3030 and 6 from Air 20/3312 as at the time I was only after what happened, not what might happen or proposed plans which make up the bulk of those files.

If I may ask, can you put them up here? Is there any issues regarding copyright?

Early in the war the RAF standard characteristics cruise height was 15,000 feet, that was changed to 20,000, the performance figures are meant to be standards for basic planning purposes, adjusted according to the mission.

What would be the optimum cruise altitude for the Spitfire Mk.VII/VIII and Mk.IX with the Merlin 63.

The idea Spitfires were retrofitted with the larger tanks helps explain the uncertainties about what capacity individual aircraft had.

Yeah, I figured they had the tanks available earlier.

Mustang 221 gallons internal 2x62.5 gallon external = 346 gallons

Okay, that makes sense. It's weird how the conversions that they're using for American aircraft don't perfectly translate across (221 imperial gallons computes out to 265.4099 US gallons and the P-51B/C's had a capacity of 269 gallons).

The figures being quoted were for a Sptfire LF.IX with a Merlin 66.

The Merlin 66 was considered a"low altitude" engine. The F.IX got the Merlin 63 which had a higher altitude rating. The difference seems to lie in the superchargers with different rotor sizes and gearing ratios.

No, the Spitfire cited by Geoffrey Sinclair was the Spitfire F. Mk.IX, and the engine cited was specifically the Merlin 63. The problem was that the RAF seemed to calculate 20000' as a default altitude for basic performance calculations. The calculations are just not accurate unless the plane cruises at 20000'.

Merlin 63 11.5/10.1 rotor dia; 6.39/8.03 gear ratios. combat power low gear @ altitude 1,710 @ 8,500ft; combat power high gear 1,510 @ 21,000ft
Merlin 66 12.0/10.1 rotor dia; 5.79/7.06 gear ratios. combat power low gear @ altitude 1,705 @ 5,750ft; combat power high gear 1,580 @ 16,000ft

V-1650-3 12.0/10.1 rotor dia; 6.39/8.095 gear ratios. combat power low gear @ altitude 1,530 @ 15,750ft; combat power high gear 1,300 @ 26,500ft
V-1650-7 12.0/10.1 rotor dia; 5.80/7.34 gear ratios. combat power low gear @ altitude 1,705 @ 5,100ft; combat power high gear 1,300 @ 26,500ft

The V-1650-3/-7 figures don't look right (I don't know enough about the Merlin 63 & 66 to even guess).

 

[Milosh]

221 imperial gallons computes out to 265.4099 US gallons

257.1661 gal
1 gal is equal to 1.1636 gal

 

[ThomasP]

I am pretty sure 1 Impgal = 1.2 USgal

 

[wuzak]

The figures being quoted were for a Sptfire LF.IX with a Merlin 66.

The Merlin 66 was considered a"low altitude" engine. The F.IX got the Merlin 63 which had a higher altitude rating. The difference seems to lie in the superchargers with different rotor sizes and gearing ratios.

Merlin 63 11.5/10.1 rotor dia; 6.39/8.03 gear ratios. combat power low gear @ altitude 1,710 @ 8,500ft; combat power high gear 1,510 @ 21,000ft
Merlin 66 12.0/10.1 rotor dia; 5.79/7.06 gear ratios. combat power low gear @ altitude 1,705 @ 5,750ft; combat power high gear 1,580 @ 16,000ft

V-1650-3 12.0/10.1 rotor dia; 6.39/8.095 gear ratios. combat power low gear @ altitude 1,530 @ 15,750ft; combat power high gear 1,300 @ 26,500ft
V-1650-7 12.0/10.1 rotor dia; 5.80/7.34 gear ratios. combat power low gear @ altitude 1,705 @ 5,100ft; combat power high gear 1,300 @ 26,500ft

The V-1650-7 is often described as nearly the equivalent of the Merlin 66

The V-1650-7 was equivalent to the Merlin 65/66. The gear ratios were slightly different because of the different drive systems (UK built Merlins had Farman type drive, Paclard 2 stage Merlins had Wright epicyclic system).

The Merlin 63 was a strengthened version of the Merlin 61, and retained the 11.5"/10.1" superchargers. Later production 2-stage Merlins had the 12"/10.1" supercharger.

When the Spitfire LF.IX was being built so too was the Spitfire HF.IX, which used the Merlin 70. The Merlin 70 had the same ratios as the 63, but had the 12"/10.1" supercharger.

 

[wuzak]

The Germans had a terrible time using twin-engined, two-seater fighters as daylight bomber escorts. Would the British have failed as badly had they sent the Mosquito fighter variant as a daylight bomber escort?

Daylight long range day fighter Mosquitoes would have performed poorly as escorts. Basically the could not compete with single engine interceptors.

The Mosquito was not designed for the traditional fighter role. It did well at night against other night fighters, and it could have some success against s/e fighters when the circumstances were right.

 

[wuzak]

While it has some of the following disadvantages

1. Critical altitude is lower than the P-51B, topping out at around 19000 feet. While the aircraft seems to retain a good degree of speed all the way up to around 25000', it's climb-rate dips more than speed with altitude. Somewhere between 10000-20000', the P-51B starts to generate a climb-rate that exceeds the Tempest Mk.II, and, by 30000', it has over twice the climb-rate.
2. Compared to the Tempest Mk.II, however: It (provided I did my conversions right) does appear to be superior to the Fw 190A across significant portions of the envelope in terms of rate of climb. With the Fw 190D, there appears to be an advantage from 0' to around 195000' with the Fw-190D doing around 40 fpm better around 30000'.

The Tempest II (Centaurus) only started in service in early 1945.

 

[EwenS]

The Tempest II (Centaurus) only started in service in early 1945.

The first production Tempest II, MW735 from the Bristol Aeroplane Co production line, first flew on 4 Oct 1944.

183 squadron was the first to receive them in Aug 1945 at Chilbolton. It was renumbered 54 squadron on 15 Nov 1945. The next unit was 247 squadron, again at Chilbolton, beginning late in Aug. The next units to get them were in India in 1946.

 

[Zipper730]

E EwenS

I didn't know they weren't online until the last few weeks of WWII...

 

[GregP]

I am pretty sure 1 Impgal = 1.2 USgal

Technically, 1 Imp Gal = 1.20095 US Gal.

 

[Zipper730]

On Imperial to US Gallons,

M Milosh , no it's not. For most purposes you'd just multiply by 1.2 for simplicity purposes, but if I recall it's technically 1.2009499204287 (I've typed that in so many times on excel due to the faulty arrangement of the sheet that it might very well have embedded itself into my memory ), though I think GregP's figure of 1.20095 is probably good enough for most purposes.

In either way the number doesn't come out to 269 US gallons, which was the correct fuel load the plane could carry (the left & right wings both carry 92 gallons apiece for 184 and the center tank carries 85 gallons).

On Merlin variants,

1. What's a Farman-type gear-train like? I know what an epicyclic system sort of looks like...
2. The V-1650-7/Merlin 65/66 hit ACA at 19000' correct?
3. What was the Merlin-63's ACA (I think the V-1650-1 was 24000').

 

[pbehn]

On Imperial to US Gallons,

M Milosh , no it's not. For most purposes you'd just multiply by 1.2 for simplicity purposes, but if I recall it's technically 1.2009499204287 (I've typed that in so many times on excel due to the faulty arrangement of the sheet that it might very well have embedded itself into my memory ), though I think GregP's figure of 1.20095 is probably good enough for most purposes.

In either way the number doesn't come out to 269 US gallons, which was the correct fuel load the plane could carry (the left & right wings both carry 92 gallons apiece for 184 and the center tank carries 85 gallons).

On Merlin variants,

1. What's a Farman-type gear-train like? I know what an epicyclic system sort of looks like...
2. The V-1650-7/Merlin 65/66 hit ACA at 19000' correct?
3. What was the Merlin-63's ACA (I think the V-1650-1 was 24000').

Do you realise what you are discussing taking a gallon down to 13 decimal places? Are you discussing the weight of fuel or the volume?

 

[Thumpalumpacus]

Do you realise what you are discussing taking a gallon down to 13 decimal places? Are you discussing the weight of fuel or the volume?

The weight (more correctly, mass) doesn't change, but the volume can and does. Anyone who's heard the whoosh of pressurized air escaping your car's fuel-cap when you go to refill can get that. Temperature changes can and do cause fuel to expand or contract. See: https://www.consumerwatchdog.org/resources/DPReportHotFuelUSAJune07.pdf

Is a gallon a measure of volume or mass? I seem to remember it being a measure of volume, but I could being suffering CRS.

Nothing to detract from your point about 13 decimal places being rather silly.

 

[pbehn]

The weight (more correctly, mass) doesn't change, but the volume can and does. Anyone who's heard the whoosh of pressurized air escaping your car's fuel-cap when you go to refill can get that. Temperature changes can and do cause fuel to expand or contract. See: https://www.consumerwatchdog.org/resources/DPReportHotFuelUSAJune07.pdf

Is a gallon a measure of volume or mass? I seem to remember it being a measure of volume, but I could being suffering CRS.

Nothing to detract from your point about 13 decimal places being rather silly.

Down to 13 decimal places you are getting into the realm of moles and groups of molecules and certainly into the realm of standard temperature and pressure Boyles law etc. As per your post, if you take the filler cap off on a hot day your tank of fuel is changing all the time the cap is off, measured to 13 decimal places, and same if you take off in a plane, that is before any discussion of what happens in the carburettor. The problem with the gallon was it came before these issues, there are liquid and dry gallons in the US system. Gallon - Wikipedia

BTW the weight is correct in the discussion, the mass will not change but the weight, to 13 decimal places may do, gravity is taken as a constant, but in the limit, it isnt.