P-51B Mustang: North American’s Bastard Stepchild that Saved the Eighth Air Force

[Bruno Anthony]

That said, he did contribute to bringing Energy Manueverability into the conversation.

Absolutely and his work with GD on the F-16.

Once we get into the Cult of Boyd, I tend to check out.

 

[HoHun]

Hi Bill,

For Penetration and Withdrawal, the climb was normally 28-30000 feet to have altitude advantage over any encountered LW fighters attacking the bombers.

I've had a look at Freeman's "The Mighty Eight - War Manual", and he details a typical mission profile as follows:

• Engine Start
• Taxying and Marshalling - 8 min
• Take-off whole group - 12 to 15 min
• Forming up - Single orbit of the base (P-38 and P-47 switch to drop tanks now, P-51 only after bringing down fuselage tank to 30 gallons)
• Climb out on course to rendezvous point - for P-51: 700 fpm @ 240 to 270 mph IAS
• Escorting bombers
  • 2 groups at bomber altitude, 1 group 4000 ft above
  • orbiting/weaving as necessary (throttling back was possible when no enemy aircraft were in the vicinity)
  • Typical escort distance - 150 to 200 miles from rendezvous to turning back
• Flight back - at high altitude until let-down over the channel

By assigning a power setting to each phase of the flight, one would have the basis for a quantified comparison of escort ranges in the European Theatre. The altitude for the cruise to the rendezvous point is missing, but I suppose we could use 18000 ft.

For the maximum return distance, I'd use the following estimation method:

• Internal fuel minus
  • For Starting, warm-up, take-off and forming up:
    • 15 min at maximum continuous (in the case of the P-51, internal fuel is reduced to a constant 30 gallons instead)
  • For escorting the bombers:
    • Fuel for 40 min maximum continuous.
    • Fuel for 15 min military power
    • Fuel for 5 min war emergency power
  • Reserve:
    • Fuel for 15 min maximum continuous

The values are a bit arbitrary, but Freeman states that bomber air speeds were 130 to 150 mph IAS while carrying bombs, and 160 to 180 mph IAS without bombs. So 60 min for 200 miles is more or less in the middle of the ballpark. The reserve and take-off allowance are loosely based on examples from the F-51H Standard Aircraft Characteristics Sheets.

Unfortunately, I don't seem to have a complete manual for the P-38 which includes the Flight Operation Instruction Chart (which show range depending on fuel reserve), so I can't include the type in the comparison, and it's a bit hairy to find and select perfectly comparable numbers for the P-47 and P-51, but using the P-51D Pilot Training Manual and the "Pilot Flight Operation Instructions for Army Models P-47D-25, -26, -27, -28, -30, and -35 Aiplanes und British Model Thunderbolt" with the 305 gallon tank size of the earlier Thunderbolts, I get the following return distances (at Maximum Air Range settings):

The fuel available (excluding reserve) for escorting and return:

• P-51D (184 gal internal): 184 gallons <- Stand-in for P-51B/C without fuselage tank
• P-51D (269 gal internal): 214 gallons
• P-47D (305 gal internal): 260 gallons
• P-47D (370 gal internal): 315 gallons

The fuel available for return (excluding reserve):

• P-51D (184 gal internal): 70 gallons @ 5.5 mpg
• P-51D (269 gal internal): 100 gallons @ 5.5 mpg
• P-47D (305 gal internal): 36 gallons @ 2.5 mpg (P-47D manual) or @ 4 mpg (P-47B/C/D/G manual)
• P-47D (370 gal internal): 101 gallons @ 2.5 mpg (P-47D manual) or @ 4 mpg (P-47B/C/D/G manual)

Well, the USAAF threw a spanner in the works there by providing two vastly different miles-per-gallons values for the P-47 in two different manuals! Glad I noticed that just before posting ... I can't resolve this right now, but of course it results even more uncertainty in return ranges than we'd have anyway:

• P-51D (184 gal internal): 385 statue miles
• P-51D (269 gal internal): 550 statue miles
• P-47D (305 gal internal): 90 statue miles OR 144 statue miles
• P-47D (370 gal internal): 253 statue miles OR 405 statue miles

These values sort of represent the maximum combat radius for the desired mission profile in a fairly realistic, apples-to-apples comparison for the European Theatre.

I have simply assumed that the range on the specified amount of internal fuel that's consumed prior to switching to drop tanks, plus the fuel that's consumed from the drop tanks, are enough to get the fighters to the rendezvous points. As long as that's given, and as long as we specify that the drop tank is not to be carried while escorting the bombers, the size of the drop tanks doesn't actually play a role for the combat radius.

(Not to say the aircraft can't range farther and return safely if they don't encounter enemy resistance that is hard enough to require them to use the power setting outlined above, or if they are allowed to start the return flight before the hour is up - for example, because they are relieved earlier, which could be a planned aspect of a particular mission. Accordingly, you could change the mission profile to increase the combat radius, but that would obviously reduce the mission effectiveness.)

Since I'm talking about actual mileages, for once I'd like to point out that your mileage migth vary ;-)

Hi Henning - good observations. I will never be talked into using iPhone again as the meeting tool as I had zero access to my laptop folders.

You might not have noticed it as you were losing connection occasionally, but the moderator did a fairly good job of showing your material while you were reconnecting. It might have been a bit out of sequence, but it probably wasn't as bad as it must have looked to you.

Regards,

Henning (HoHun)

 

[drgondog]

Hi Bill,



I've had a look at Freeman's "The Mighty Eight - War Manual", and he details a typical mission profile as follows:

• Engine Start
• Taxying and Marshalling - 8 min
• Take-off whole group - 12 to 15 min
• Forming up - Single orbit of the base (P-38 and P-47 switch to drop tanks now, P-51 only after bringing down fuselage tank to 30 gallons)

SOP forLR escort was to burn to 65gal. AAF recommendation was to burn to 45-50gal

• Climb out on course to rendezvous point - for P-51: 700 fpm @ 240 to 270 mph IAS
• Escorting bombers
  • 2 groups at bomber altitude, 1 group 4000 ft above
  • orbiting/weaving as necessary (throttling back was possible when no enemy aircraft were in the vicinity)
  • Typical escort distance - 150 to 200 miles from rendezvous to turning back
• Flight back - at high altitude until let-down over the channel

By assigning a power setting to each phase of the flight, one would have the basis for a quantified comparison of escort ranges in the European Theatre. The altitude for the cruise to the rendezvous point is missing, but I suppose we could use 18000 ft.

Based on NA 8449 P-51D Performance Report, climb to altitude was made at 160-180mph (SL through 12K- low blower), 180-210 plus at Max Continuous power (12K through 20K -high blower). Time to 25K =20min. Distance covered 66mi. Cruise at 60% power ~ 322mph. Cruise at 2200RPM/32"MP and 2x75gal tanks ~ 285mph.

The straight line calcs for Combat Radius, 415gal (incl 30min reserve) was 802mi w/15min MilPwr/5min WEP. Also stipulated dropping 75gal tanks 625mi out. Sourcs Fig 4., page 7.

That said, in no universe was that CR actually attained with 20min combat and 30min reserve.

For the maximum return distance, I'd use the following estimation method:

• Internal fuel minus
  • For Starting, warm-up, take-off and forming up:
    • 15 min at maximum continuous (in the case of the P-51, internal fuel is reduced to a constant 30 gallons instead)
  • For escorting the bombers:
    • Fuel for 40 min maximum continuous.
    • Fuel for 15 min military power
    • Fuel for 5 min war emergency power
  • Reserve:
    • Fuel for 15 min maximum continuous

The values are a bit arbitrary, but Freeman states that bomber air speeds were 130 to 150 mph IAS while carrying bombs, and 160 to 180 mph IAS without bombs. So 60 min for 200 miles is more or less in the middle of the ballpark. The reserve and take-off allowance are loosely based on examples from the F-51H Standard Aircraft Characteristics Sheets.

Unfortunately, I don't seem to have a complete manual for the P-38 which includes the Flight Operation Instruction Chart (which show range depending on fuel reserve), so I can't include the type in the comparison, and it's a bit hairy to find and select perfectly comparable numbers for the P-47 and P-51, but using the P-51D Pilot Training Manual and the "Pilot Flight Operation Instructions for Army Models P-47D-25, -26, -27, -28, -30, and -35 Aiplanes und British Model Thunderbolt" with the 305 gallon tank size of the earlier Thunderbolts, I get the following return distances (at Maximum Air Range settings):

The fuel available (excluding reserve) for escorting and return:

• P-51D (184 gal internal): 184 gallons <- Stand-in for P-51B/C without fuselage tank
• P-51D (269 gal internal): 214 gallons
• P-47D (305 gal internal): 260 gallons
• P-47D (370 gal internal): 315 gallons

The fuel available for return (excluding reserve):

• P-51D (184 gal internal): 70 gallons @ 5.5 mpg
• P-51D (269 gal internal): 100 gallons @ 5.5 mpg
• P-47D (305 gal internal): 36 gallons @ 2.5 mpg (P-47D manual) or @ 4 mpg (P-47B/C/D/G manual)
• P-47D (370 gal internal): 101 gallons @ 2.5 mpg (P-47D manual) or @ 4 mpg (P-47B/C/D/G manual)

Well, the USAAF threw a spanner in the works there by providing two vastly different miles-per-gallons values for the P-47 in two different manuals! Glad I noticed that just before posting ... I can't resolve this right now, but of course it results even more uncertainty in return ranges than we'd have anyway:

• P-51D (184 gal internal): 385 statue miles
• P-51D (269 gal internal): 550 statue miles
• P-47D (305 gal internal): 90 statue miles OR 144 statue miles
• P-47D (370 gal internal): 253 statue miles OR 405 statue miles

These values sort of represent the maximum combat radius for the desired mission profile in a fairly realistic, apples-to-apples comparison for the European Theatre.

I have simply assumed that the range on the specified amount of internal fuel that's consumed prior to switching to drop tanks, plus the fuel that's consumed from the drop tanks, are enough to get the fighters to the rendezvous points. As long as that's given, and as long as we specify that the drop tank is not to be carried while escorting the bombers, the size of the drop tanks doesn't actually play a role for the combat radius.

The drop tanks were retained until engaged - and the drag of the pylons are considerable. The P-51B and P-38J and P-47D pylon drag was of order of 10mph at max power.The P-51D pylon ~ 6mph. Less for cruise speed but still more than 'true clean' as most often cited in flight testing.

That said, I know that when carrying steel tanks, the pilots were encouraged to keep them if not engaged. Conversely the Bowater-lloyd composite tanks were always dropped when empty.

Also, the 85gal tank was rarely drained below 50gal on a long range escort. Anecdotally my father's 355th loaded 85gal and only burned some after arriving at R/V south of Stettin for FRANTIC VII. His logbook had 7hr 50min for that leg. SOP for 355th was to load 65gal on most missions, but switch to wing tanks first after take off and forming up to begin climb.

(Not to say the aircraft can't range farther and return safely if they don't encounter enemy resistance that is hard enough to require them to use the power setting outlined above, or if they are allowed to start the return flight before the hour is up - for example, because they are relieved earlier, which could be a planned aspect of a particular mission. Accordingly, you could change the mission profile to increase the combat radius, but that would obviously reduce the mission effectiveness.)

In complete agreement. The Fighter Mission (Sweep) range was considerably farther then escort range.

Since I'm talking about actual mileages, for once I'd like to point out that your mileage migth vary ;-)

As usual your calcs are sound, but the base assumptions on actual cruise settings and escort durations seem at variance with SOP, at least based on actual recollections of many that I grew up around. More common cruise power for P-51B/D was in range of 32-36"MP (lead vs wing) for 220+IAS at 25K - which ties nicely to the below test reports.

200mi for one hour of escort seems fine based on a typical historical target escort durations for a P-51 or P-47 in Ess/Racetrack pattern. The diffeences were largely the R/V and Break Escort locations on the continent.

That said, I applied Brequet equation methodolgy in which diminishing gross weight and decreasing angle of attack (and decreasing induced drag) and constantly reducing power required for constant altitude and airspeed - resulted in about 5% more range than NAA calcs.

You might not have noticed it as you were losing connection occasionally, but the moderator did a fairly good job of showing your material while you were reconnecting. It might have been a bit out of sequence, but it probably wasn't as bad as it must have looked to you.

Regards,

Henning (HoHun)

Thank you for that.
Roger Freeman published generally excellent data and information. What Freeman did not focus on was the effect of external tanks and racks on drag - which affected cruise speed at economical settings.

The drag of twin 75gal tanks and pylons on P-51B was considerably less than P-47D with 108 or 150gal tanks and pylons.

Anecdotally, the B-17 inbound cruise speed was 150mph IAS at 25K due to lower performance of some aircraft/engines at cruise settings - outbound 180IAS.

For close escort, more typically the high squadron was 'essing' 3-5000 feet higher, while the other squadrons were more closely at bomber altitudes in a 'racetrack pattern.

Eglin and Wright Field did quite a bit of range testing but I have yet to find flight testing of P-47D. That said, I am quite sure that 4mpg for dirty drop tank config was impossible - closer to 2.5mpg.

Attached is one set of P-51D tables at different altitudes and configurations. The drag of the 75gal tank was about the same as a 500# bomb for reference on fuel consumption.

P 51D Performance Test

and drag curves

http://www.wwiiaircraftperformance.org/mustang/P-51D_15342_Drag_Curves.jpg

and fuel consumption

http://www.wwiiaircraftperformance.org/mustang/P-51D_15342_AppendixB.pdf

 

[bercr]

Just correcting a misprint: Breguet equation (with a g, not Brequet)

 

[HoHun]

Hi Bill,

Thanks a lot for the detailed answer!

As usual your calcs are sound, but the base assumptions on actual cruise settings and escort durations seem at variance with SOP, at least based on actual recollections of many that I grew up around. More common cruise power for P-51B/D was in range of 32-36"MP (lead vs wing) for 220+IAS at 25K - which ties nicely to the below test reports.

Admittedly, Freeman provided some useful starting points, but he didn't give the full mission details, so I had to make some assumptions.

My question would be, which power settings were used on the escort leg as long as no Luftwaffe fighters were sighted? The same 32 to 36" Hg?

The range table from Mike's site for the 25000 ft, 2250 rpm data point aligns nicely with the corresponding Flight Operation Instruction Chart:

Also, the 85gal tank was rarely drained below 50gal on a long range escort. Anecdotally my father's 355th loaded 85gal and only burned some after arriving at R/V south of Stettin for FRANTIC VII. His logbook had 7hr 50min for that leg. SOP for 355th was to load 65gal on most missions, but switch to wing tanks first after take off and forming up to begin climb.

If I schedule 15 min at maximum continuous for start/take-off/form-up, that uses up 24.3 gallons, leaving us with 60.7 gallons in the fuselage tank if it was used first. As that seems both realistic and eliminate a P-51 specific assumption, I'll go with that for now.

For "escort cruise" power (as I'll call it for ease of reference), I'm going to use 25000 ft, 2250 rpm @ 73 gph for 370 mph for the P-51D, and 25000 ft, 2290 rpm @ 146 gph for 324 mph for the P-47D.

Using the same 15 min at maximum continuous for start/take-off/form-up assumption for both aircraft, the reduced "escort cruise" consumption results in return distances:

P-51D (184 gal internal): 350 miles @ 5.625 mpg
P-51D (269 gal internal): 825 miles @ 5.625 mpg
P-47D-25* (305 gal internal): 255 miles @ 3.0 mpg
P-47D-25 (370 gal internal): 455 miles @ 3.0 mpg

(I stayed with the P-47D-25 for now since the Flight Operation Instruction Chart for the P-47B/C/D/G has the 5 mpg cruise data that needs further investigations. Of course, that's not a 1943 type, but I'm trying to reduce complexity right now.)

So that means that a P-47D-25 due to its larger fuel tank could have flown this particular mission profile and returned from Schweinfurt (which is about 425 statue miles from Wattisham, which unlike the wartime fields in the same area can be found on skyvector.com), but the same aircraft with the 305 gallon tank of the earlier versions couldn't have.

Ironically, the P-51D with the fuselage tank would have easily been able fly this mission profile and return from Schweinfurt easily, but without its fuselage tank, it couldn't have done so either.

Again, I've ignored the question of whether the aircraft could have gotten there on drop tanks only, and I've stayed with the assumption that the drop tanks were dropped at the beginning of the actual escort part of the mission. I'll leave that for later posts

Now we can turn this around and see what kind of mission the P-47D-25 with only 305 gallons internal could have flown to Schweinfurt, by reducing the "escort cruise" time: 5 min WEP, 10 min MIL, 17.2 min "escort cruise".

Accordingly, the bombers wouldn't have been escorted by fighters for 60 min, as desired by the mission profile and possible with the mid-to-late-1944 variants of both fighters, but only for 32 min. With regard to mission planning, that would mean that you'd have to schedule twice the number of fighters for the same escort coverage - which perhaps shows in a slightly different way why more range made a better escort fighter.

That said, I applied Brequet equation methodolgy in which diminishing gross weight and decreasing angle of attack (and decreasing induced drag) and constantly reducing power required for constant altitude and airspeed - resulted in about 5% more range than NAA calcs.

Makes perfect sense, but weren't the fighter pilots trained to fly matching power settings? Of course, the Flight Operation Instruction Chart does not show the effect from a speed increase due to the weight reduction either. Sort of odd, since the format of the table would allow to take Breguet into account.

Regards,

Henning (HoHun)

 

[HoHun]

Hi again,

Again, I've ignored the question of whether the aircraft could have gotten there on drop tanks only, and I've stayed with the assumption that the drop tanks were dropped at the beginning of the actual escort part of the mission. I'll leave that for later posts

To follow up on this, I added calculations for the cruise out on drop tanks as well as for the escort part and the return flight.

Since the manuals don't give all of the figures required (such as distance covered in climb), and not all versions of the manuals have all of the data (such as the 200 gallon drop tank data only being provided by an older version of the P-47 manual), it's not really rock solid, but I suppose it's not too far off. I wouldn't rule out an occasional mistake on my part when transferring parameters from the manuals into my spreadsheet, but I don't think I would have been dramatically off without noticing.

Anyway, here are the results:

<Edit: Since I made a mistake by subtracting the allowance for engine start, warm-up, take-off, form-up *twice*, and didn't notice that the USAAF hid even more fuel for warm-up and take-off in the climb data , I've edited the results somewhat so future readers don't get unecessarily confused by this error.>

[*]P-47D (370 gallon internal, 200 gallon drop tank):

• Engine start, warm-up, take-off, form-up: 55 gallons (internal) @ 220 GPH
• Climb to 25000 ft: 118 gallons (external), covering ca. 50 miles
• Cruise on drop tanks until empty: 148.8 miles @ 1.81 MPG
• Cruise to rendezvous (408.6 miles out): 92.8 gallons (internal) @ 2.27 MPG
• Escort flight for 6.5 min.(5 min MIL, 1.5 min escort cruise @ 143 GPH)
  • The bombers are assumed to cover the 16.4 miles remaining to the target while thus escorted.
• Return flight: 425 miles @ 3.03 MPG
• Reserves due to HoHun's accounting errors: 85 gallons = 257 miles
  

[*]P-51D without fuselage tank (184 gallon internal, 2 * 75 gallon drop tank):

• Engine start, warm-up, take-off, form-up: 24.3 gallons (internal) @ 97 GPH
• Climb to 25000 ft: 44 gallons (external), covering ca. 61.1 miles
• Cruise on drop tanks to rendezvous (321.3 miles out): 260.2 miles @ 3.92 MPG
  • Tanks are assumed to be dropped at rendezvous, still containing 53.1 gallons total.
• Escort flight for 41.5 min.(5 min MIL, 36.5 min escort cruise @ 73 GPH)
  • The bombers are assumed to cover the 103.7 miles remaining to the target while thus escorted.
• Return flight: 425 miles @ 5.63 MPG
• Reserves due to HoHun's accounting errors: 39.3 gallons = 221 miles

[/LIST]

I'm not sure if that proves anything, but at the very least, it illustrates why long range makes an escort fighter more effective.

Regards,

Henning (HoHun)

 

[drgondog]

Hi Henning - I won't nit pick your calcs, all very good and match your assumptions.

Anecdotally the mission profile would only include METO for a short time and depending on the mission would not even climb at Max Continous. From Steeple Morden, the longer distance from coast compared to Halesworth granted more leeway to climb to altitude over N.Sea.

Anecdotally again from all my sources growing up, a long range mission with R/V near target (such as Munich with R/V s. Augsberg) the cruise with 75gal tanks would have been in 32-36"MP and 2200-2400 RPM from crossing coastline all the way at 25K_ with the top cover assignment climbing to 3-5K above assigned box altitude for escort position at ~220IAS. Cruise w/75gal tank was in range of 295mh TAS and ~260TAS w/108gal tanks at 25K

I believe that all operating manual data were delivered via contractor, tested by AAF and then the FAREP charts were published , accompanied by 'average' start up, taxi, take off and climb fuel consumption.

I published the tables fr P-38, P-47 and P-51 on pg 318 of Bastard Stepchild. Dean's America's One Hundred Thousand publiched the bar chart and I converted the table/bar chart data to map of ETO centered n Duxford (pg 317)

FWIIW the data for a.) SE through take off and climb (no account for formation assembly), b.) Reserve 30min, and c.) combat were:
Clean
P-38J 300int 86 50 111
P-38J 410int 98 50 111
P-47C/D 305int 101 40 89
P-51B 180int 46 26 58
P-51B 265int 51 26 58

As a practical yardstick I dove into 8th AF VCB June 1945 to extract a month by month longest recorded combat encounter for which a victory was claimed.

Showing that calc versus reality were often at odds

The January 11 MOH mission by 354FG P-51B wo 85 gal was Halberstadt, about 406mi from Boxted. The first time the 56thFG fought there was May 1944 w/2x150gal ext, 305int

Jan 11 saw the 354FG provided target escort at Bodeaux - 496mi from Boxted. 180gal int plus 2x75gal drop tanks.

The attached spreadsheet compares actual distances from Halesworth and Boxted for longest 56FG victory credits to the 8th AF Tactical Development map on pg97. It is 'optimistic' compared to the later FAREP charts and ranges.

 

[HoHun]

Hi again,

Hi Henning - I won't nit pick your calcs, all very good and match your assumptions.

Very embarrassing to admit it , but I just noticed that there must be a mistake in the calculations as the parts don't sum up to the correct total.

Stay tuned while I hunt for bugs in my spreadsheet!

Regards,

Henning (HoHun)

 

[drgondog]

Hi again,



Very embarrassing to admit it , but I just noticed that there must be a mistake in the calculations as the parts don't sum up to the correct total.

Stay tuned while I hunt for bugs in my spreadsheet!

Regards,

Henning (HoHun)

I hate to fess up, but I think I may have made an error or tw on spreadsheets...

 

[HoHun]

Hi again,

Stay tuned while I hunt for bugs in my spreadsheet!

After tidying everything up a bit, it turns out I had subtracted the allowance for engine start, warm-up, take-off and form-up *twice*, which did of course affect combat persistence negatively! :-D

After correcting this mistake, even the early P-47D could have made an escort mission to Schweinfurt ... here's the comparison:

- P-47D (early, 305 gal internal + 200 gal drop tank): 5 min MIL, 10.8 min "escort cruise"
- P-47D-25 (370 gal internal + 200 gal drop tank): 5 min MIL, 44.5 min "escort cruise"
- P-51D (184 gal internal + 2 * 75 gal drop tank): 5 min MIL, 56.5 min "escort cruise" <- stand-in for P-51B/C without fuselage tank
- P-51D (269 gal internal + 2 * 75 gal drop tank): 5 min MIL, 126.3 min "escort cruise"

(The "no fuselage tank" P-51D drops 63.2 gal unused fuel at the rendezvous, the standard P-51D drops 98.7 gal. The difference is due to the version with the larger internal fuel volume being able to escort the bombers for longer, thus having the rendezvous earlier in the mission.)

I did not allow for any reserve in the mission profile other than the additional range gained from throttling back during the let-down on the way home.

So, while the early P-47D with a 200 gal drop tank could give bombers roughly a quarter of an hour of escort time over Schweinfurt, that's probably close to the best-case scenario for this configuration, and so I'm not sure the USAAF planners would really have scheduled that kind of mission profile.

I haven't yet checked Bill's latest post for useful information I could use to make my mission profile more realistic since I was distracted by that bug in my calculations ... maybe that will cast yet a different light on the comparison!

Regards,

Henning (HoHun)

 

[HoHun]

Hi Bill,

Anecdotally the mission profile would only include METO for a short time and depending on the mission would not even climb at Max Continous. From Steeple Morden, the longer distance from coast compared to Halesworth granted more leeway to climb to altitude over N.Sea.

Sounds like good practice to stretch the range. The manual only provides limited climb data ... climb speed reducing from 175 mph IAS at sea level to 145 mph IAS at 25000 ft, and climb rate from 1450 fpm to 1100 rpm (at 11000 lbs weight).

Oops, the values contain another 15 gallon warm-up and take-off allowance! That had escaped me ... and it's 30 gallons allowance for the P-47D. Well, I'll just consider my previous calculations to have a 15 to 20 min reserve - I think I saw in the combat radius calculations for the post-war Standard Aircraft Characteristics that a bit more would be more realistic, but it's a step in the right direction.

Anecdotally again from all my sources growing up, a long range mission with R/V near target (such as Munich with R/V s. Augsberg) the cruise with 75gal tanks would have been in 32-36"MP and 2200-2400 RPM from crossing coastline all the way at 25K_ with the top cover assignment climbing to 3-5K above assigned box altitude for escort position at ~220IAS. Cruise w/75gal tank was in range of 295mh TAS and ~260TAS w/108gal tanks at 25K

I'm using the 25000 ft value from the manual, which gives 2100 rpm @ full throttle for 60 GPH at 295 mph TAS, which is a bit slower with less spower. The next column in the table is a bit on the faster side ... probably when flying in formations, they used the faster column but had the leader throttle back just slightly so the wingmen had a bit of throttle to play with?

FWIIW the data for a.) SE through take off and climb (no account for formation assembly), b.) Reserve 30min, and c.) combat were:
Clean
P-38J 300int 86 50 111
P-38J 410int 98 50 111
P-47C/D 305int 101 40 89
P-51B 180int 46 26 58
P-51B 265int 51 26 58

Thanks, that's a useful data set for cross-checking! Looks like a decent fit, considering that the climb altitude is not given and it's not clear to me whether the climb was with drop tanks.

The use of a 30 min reserve confirms my impression that my accidental 15 - 20 min reserve would not have been enough for the USAAF!

The attached spreadsheet compares actual distances from Halesworth and Boxted for longest 56FG victory credits to the 8th AF Tactical Development map on pg97. It is 'optimistic' compared to the later FAREP charts and ranges.

Hehe, that's really good use of data! I've graphed the information, which nicely highlights the systematic bias towards consistently shorter ranges, despite a few kills "outside" the range limits:



Regards,

Henning (HoHun)

 

[HoHun]

Hi again,

After correcting this mistake, even the early P-47D could have made an escort mission to Schweinfurt ... here's the comparison:

Eliminating the redundant allowance "hidden" in the manuals' climb figures and inserting the reserve fuel allocations provided by the USAAF range data quoted by "P-51B Mustang: North American’s Bastard Stepchild", the comparison now looks as follows - for the Schweinfurt escort mission, escorting the bombers to the target at 425 miles out from the fighter airfield:

Type	Internal Fuel [US Gal]	Drop Tank [US Gal]	WEP [min]	MIL [min]	Escort Cruise [min]
P-47D (early)	305	200	0	1	6.4
P-47D-25	370	200	5	5	19.7
P-51D	184	2 * 75	5	5	20.3
P-51D	269	2 * 75	5	15	64.5

(As before, the "no fuselage tank" P-51D drops 63.2 gal unused fuel at the rendezvous, the standard P-51D drops 98.7 gal. The P-47D has to drop the fuel tanks before the rendezvous and use some internal fuel to get there.)

As a useful benchmark, the USAAF according to the table from Bill's book calculated a combat radius of 275 miles for the P-47C/D-15, which according to my calculations would be good for the following mission profile:

Type	Internal Fuel [US Gal]	Drop Tank [US Gal]	WEP [min]	MIL [min]	Escort Cruise [min]
P-47D (early)	305	108	5	5	29.4

That's based on the climb time for the 200 US gallon tank, and being about 600 pounds light might save a couple of gallons and thus give a little more escort time than I account for, but it illustrates nicely what the USAAF at the time considered the requirement for an effective escort mission.

Based on that, one could conclude that the P-47D (early) with a 200 gallon drop tank would not have been effective over Schweinfurt, the P-47D-25 with the same tank as well as the P-51 with no fuselage tank and two 75 gallon drop tanks would have been borderline effective, and the P-51 with fuselage tank would have been very effective.

Regarding the P-47D-25 and the P-51 without fuselage tank, the latter could have become a markdely more effective if it were allowed to carry the drop tanks into the escort part of the mission, as was done historically, so the apparent equivalence is a bit of an artifact of using a standardized mission profile.

Regards,

Henning (HoHun)