Fighter Escorts of B-29's over Japan & Pacific

[Dash119]

First, GrauGeist I'm not sure that higher altitudes result in greater fuel efficiency and engine load demand for pistons engines as it does with turbojets and turbofans. Higher altitudes require more boost and there is a cost for that. Additionally, although the air is cooler it is less dense meaning cooling is less efficient. Hence the numbers for the B-36 above.

Second, BiffF15 your descriptions of the divert process on the OV-10 & RC-26 don't really answer the question of fuel efficiency and engine load at altitude. To this layman they just seem to indicate that the fuel efficiency in climb is lousy compared to the fuel efficiency in cruise and descent.

I'm thinking the efficiencies have nothing to do with the propellors, but rather the piston versus the turbine.

 

[GrauGeist]

Keep in mind I am not stating "max" altitude, but "higher" altitudes.

The B-29's "sweet spot" was roughly 15,000 ASL with a full load of fuel and medium to heavy bombload (not max/overload).

Piston powered aircraft will not be as efficient as jet powered aircraft at any altitude because of drag penalties imposed by the engines's frontal area, especially with a radial - but the fact remains that the denser atmosphere at sea level creates more resistance than it does at 20,000 feet.

 

[Shortround6]

Piston engines have problems with cooling at the higher altitudes if pushed.

While the air is cooler/colder it is less dense. the air at 20,000ft is 53% as dense (lb/cu ft) as the air at sea level.
The colder temperature helps but does not make up for the lower mass flow through the cooling system,

Now throw in that that the mixture temperature is higher. The heat added to the mixture temperature?intake charge goes up with the increased compression needed at the higher altitudes. A Merlin XX raised the temperature of the intake charge 148 degrees C at 9lbs boost for example. Granted the temperature rise would be less at lower boost.
Yes the B-29s used intercoolers but the GE turbos were never known for being among the highest efficiency compressors.
High intake charge temperature follows right through the engine, higher cylinder temperatures and higher exhaust temperatures.

Modern fan jets are bit different, they generally have a surplus of air flowing thought the engine/nacelle compared to the amount of fuel burned.

 

[Joe Broady]

Piston engines have problems with cooling at the higher altitudes if pushed.

While the air is cooler/colder it is less dense. the air at 20,000ft is 53% as dense (lb/cu ft) as the air at sea level.
The colder temperature helps but does not make up for the lower mass flow through the cooling system

That's consistent with the B-29 training manual: "Maximum range, like maximum endurance, is obtained at low altitude. However, if you operate at powers of 2200 rpm and 35" in AUTO LEAN (or less) in the desired speed band, there is no gain in range by flying at a lower altitude. The range loss at high altitudes is caused almost entirely by the rich mixtures required at high powers and the larger cowl flap openings needed to cool the engines at high altitudes."

I found two editions of this manual at archive.org. There's an interesting difference in the recommended transition from climb to cruise. In February 1945 you are instructed in no uncertain terms to "get on the step": overshoot cruise altitude by 500 - 1500 feet, maintain level flight and climb power, accelerate to 210 mph. Then set cruise power, maintain 210 mph in a shallow dive, level off at cruise altitude. "A speed of 210 mph will put the airplane on the step... The B-29 does not reach its maximum airspeed for a given power setting unless you fly it on the step." (Boldface in original.)

But the December edition omits any reference to "the step". You simply level off at cruise altitude and reduce power when the B-29 reaches the desired speed. An overshoot and dive to cruise altitude is performed only if cylinder head temperatures are excessive.

In the B-36 the preferred procedure (with permission from ATC) was to overshoot by 500 feet, set cruise power, and allow the plane to slowly descend to cruise altitude. But this had nothing to do with "getting on the step". The 500 feet gave a cushion of extra energy so you would not accidentally get too slow during the complex transition of 10 engines from climb power to the cruise configuration.

B-29 training manual Feb 45
B-29 training manual Dec 45

 

[LarryJ]

I find it interesting this thread evolved from B-29 fighter escorts to fuel economy.

I wasn't aware that fighters escorted the bombers until I read some items in a different thread from the fighter perspective. I knew of single B-29s being the enroute navigation services for fighters, mama bird and chicks, to Japan and back.

 

[Zipper730]

From the limited information I have, it seems the first operations listed here were out of the Marianas: Payloads and fuel reserves are averaged out

Mission 1
Date: 1944/10/27 - 10/28
Codename: Truk
Target: Dublon Island: Submarine Pens
Participating Unit: 73rd BW
A/C Launched: 18
Altitude: 25900-27450'
Time on Target: 08:55-09:00
Payload: 6000 lb.
Fuel Reserve: 1812 gal.

Mission 2
Date: 1944/10/30
Codename: Truk
Target: Dublon Island: Submarine Pens
Participating Unit: 73rd BW
A/C Launched: 18
Altitude: 25500-27450'
Time on Target: 11:00-11:03
Payload: 6000 lb.
Fuel Reserve: 2011 gal.

Mission 3
Date: 1944/11/2
Codename: Truk
Target: Dublon Island: Submarine Pens
Participating Unit: 73rd BW
A/C Launched: 20
Altitude: 25900-27300'
Time on Target: 10:34-11:35
Payload: 5000 lb.
Fuel Reserve: 2053 gal.

Mission 4
Date: 1944/11/5
Codename: Iwo Jima
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 73rd BW
A/C Launched: 36
Altitude: 26750-27500'
Time on Target: 16:23-16:39
Payload: 10000 lb.
Fuel Reserve: 1409 gal.

Mission 5
Date: 1944/11/8
Codename: Iwo Jima
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 73rd BW
A/C Launched: 17
Altitude: 27650-29000'
Time on Target: 12:32-12:34
Payload: 10000 lb.
Fuel Reserve: 1167 gal.
Losses: 1
Notes: If I read this right, the enemy dropped phosphorous bombs on B-29 formations. I only know of one or two other cases where bombers got bombed while in the air, one of which was the Scweinfurt Raids.

Mission 6
Date: 1944/11/11
Codename: Truk
Targets

Primary: Dublon Island: Submarine Base​

Secondary: Dublon Island: Shipping​

Participating Unit: 73rd BW
A/C Launched: 9
Altitude: 25000'
Time on Target: 13:55-13:57
Payload: 10000 lb.
Fuel Reserve: 2212 gal.

Mission 7
Date: 1944/11/24
Codename: San Antonio #1
Targets

Primary: Tokyo: Nakajima A/C Factory, Musashino​

Secondary: Tokyo Urban / Dock Area​

Participating Unit: 73rd BW
A/C Launched: 111
Altitude: 27000-32000'
Time on Target: 13:12-15:32 (Primary)
Payload: 10000 lb.
Fuel Reserve: 1048 gal.
Losses: 2
Notes: Groundspeed managed to reach 445 mph over target-area. Given the Norden bombsight's limit is around 450 mph, this would (among other things) explain problems with bombing accuracy.

Mission 8
Date: 1944/11/27
Codename: San Antonio #2
Targets

Primary: Tokyo: Nakajima A/C Factory, Musashino​

Secondary: Tokyo Urban / Dock Area​

Participating Unit: 73rd BW
A/C Launched: 81
Altitude

Primary: N/A​

Secondary: 27700-34000'​

Opportunity: 32500'​

Time on Target

Secondary: 13:47-15:25​

Opportunity: 14:20-14:23​

Payload: 10000 lb.
Fuel Reserve: 1093 gal.
Losses: 1
Notes: Japanese forces attacked Isley Field at Saipan during the course of this mission.

Mission 9
Date: 1944/11/29 - 11/30
Codename: Brooklyn #1
Targets

Primary: Tokyo Industrial Area​

Last Resort: Any Industrial City​

Participating Unit: 73rd BW
A/C Launched: 29
Altitude

Primary: 25000-33000'​

Last Resort: 21000-33200'​

Time on Target

Primary: 00:50-05:27​

Last Resort: 01:06-01:57​

Payload: 7000 lb.
Fuel Reserve: 1238 gal.
Losses: 1
Notes: Strange that the first to missions to Tokyo had an average of 10000 lb. of ordinance, and it was now reduced to 7000 lb.

Mission 10
Date: 1944/12/3
Codename: San Antonio #3
Targets

Primary: Tokyo: Nakajima A/C Factory, Musashino​

Secondary: Tokyo: Docks & Urban Area​

Participating Unit: 73rd BW
A/C Airborne: 86
Altitude: 16000-33100'
Time on Target: 05:03-06:30 (Primary)
Payload: 5000 lb.
Fuel Reserve: 815 gal.
Losses: 5
Notes: This seems to be the first mission where the altitude was below 20000'. The large spread in altitudes appears to be aimed at splitting the air-defenses up.

Mission 11
Date: 1944/12/8
Codename: Sledgehammer #1
Targets

Primary: Iwo Jima: Airfields​

Secondary: Pagan Island​

Participating Unit: 73rd BW
A/C Launched: 79
Altitude: 19670-23400'
Time on Target: 10:20-11:50 (Primary)
Payload: 20000 lb.
Fuel Reserve: 1454 gal.
Notes: 3 x B-29's listed in the total provided navigation for 28 x P-38's.

Mission 12
Date: 1944/12/13
Codename: Memphis #1
Targets

Primary: Nagoya: Mitsubishi A/C Engine Plant​

Secondary: Nagoya Urban Area​

Last Resort: Any Industrial City​

Participating Unit: 73rd BW
A/C Launched: 90
Altitude: 26450-32300'
Time on Target: 14:57-16:38 (Primary)
Payload: 5000 lb.
Fuel Reserve: 783 gal.
Losses: 4

Mission 13
Date: 1944/12/18
Codename: Hesitation #1
Target: Nagoya: Mitsubishi A/C Plant
Participating Unit: 73rd BW
A/C Launched: 89
Altitude: 28000-32000'
Time on Target: 14:00-15:43
Payload: 5000 lb.
Fuel Reserve: 705 gal.
Losses: 4

Mission 14
Date: 1944/12/22
Codename: Eradicate #2
Target: Nagoya: Mitsubishi A/C Engine Factory
Participating Unit: 73rd BW
A/C Launched: 78
Altitude: 28800-32600'
Time on Target: 14:04-15:58
Payload: 5500 lb.
Fuel Reserve: 1045 gal.
Losses: 3

Mission 15
Date: 1944/12/24
Codename: Rockcrusher #1
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 73rd BW
A/C Launched: 29
Fighter Sweep: Unspecified
Altitude: 19500-21800'
Time on Target: 14:24-15:35
Payload: 10000 lb.
Fuel Reserve: 1832 gal.
Notes: 3 x B-29's not included provided navigation for a fighter-sweep. The lower altitudes on this mission and Mission #11 might be more for the benefit of the fighter-sweep than the bomber.

Mission 16
Date: 1944/12/27
Codename: Enkindle #1
Target: Tokyo: Nakajima A/C Plant, Musashino
Participating Unit: 73rd BW
A/C Launched: 72
Altitude: 28200-33800'
Time on Target: 13:42-15:03
Payload: 5500 lb.
Fuel Reserve: 1200 gal.
Losses: 3

Mission 17
Date: 1945/1/3
Codename: Microscope #1
Target: Nagoya: Docks & Urban Area
Participating Unit: 73rd BW
A/C Launched: 97
Altitude: 28200-31500'
Time on Target: 15:45-16:33
Payload: 5300 lb.
Fuel Reserve: 761 gal.
Losses: 5

Mission 18
Date: 1945/1/9
Codename: Enkindle #2
Target: Tokyo: Nakajima A/C Plant, Musashino
Participating Unit: 73rd BW
A/C Launched: 72
Altitude: 29500-34400'
Time on Target: 15:13-15:35
Payload: 5000 lb.
Fuel Reserve: 1174 gal.
Losses: 6

Mission 19
Date: 1945/1/14
Codename: Hesitation #2
Target: Nagoya: Mitsubishi A/C Plant
Participating Unit: 73rd BW
A/C Launched: 73
Altitude: 29080-32000'
Time on Target: 15:40-16:28
Payload: 5000 lb.
Fuel Reserve: 909 gal.
Losses: 5

Mission - None Assigned
Date: 1945/1/16
Codename: Fagan Island
Target: Fagan Island: Airstrip
Participating Unit: 313th BW
A/C Launched: 44
Altitude: 28300-28400'
Time on Target: 11:33-17:54
Payload: 12000 lb.
Fuel Reserve: 1854 gal.
Notes: Shakedown mission.

Mission 20
Date: 1945/1/19
Codename: Fruitcake #1
Target: Osaka: Kawasaki A/C Plant, Akashi
Participating Unit: 73rd BW
A/C Launched: 80
Altitude: 25100-27400'
Time on Target: 14:50-15:24
Payload: 5000 lb.
Fuel Reserve: 1057 gal.

Mission 21
Date: 1945/1/21
Codename: Panhandle #1
Target: Moen Island: Airfield
Participating Unit: 313th BW
A/C Launched: 33
Altitude: 25500-26000'
Time on Target: 10:34-11:08
Payload: 11000 lb.
Fuel Reserve: 1817 gal

Mission 22
Date: 1945/1/23
Codename: Eradicate #3
Target: Nagoya: Mitsubishi A/C Engine Plant
Participating Unit: 73rd BW
A/C Launched: 73
Altitude: 25300-27200'
Time on Target: 05:35-05:47
Payload: 6000 lb.
Fuel Reserve: 1053 gal.
Losses: 2

Mission 23
Date: 1945/1/24
Codename: Starlit #1
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 313th BW
A/C Launched: 28
Altitude: 26000-28000'
Time on Target: 12:28-13:30
Payload: 12000 lb.
Fuel Reserve: 1622 gal.

Mission 24
Date: 1945/1/27
Codename: Enkindle #3
Targets

Primary: Tokyo: Nakajima A/C Plant, Musashino​

Secondary: Tokyo Urban Area​

Participating Unit: 73rd BW
A/C Launched: 74
Altitude: 24500-29600'
Time on Target: 15:04-15:58
Payload: 6000 lb.
Fuel Reserve: 1059 gal.
Losses: 9

Mission 25
Date: 1945/1/29
Codename: Starlit #2
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 313th BW
A/C Launched: 33
Altitude: 23000-25200'
Time on Target: 14:28-14:47
Payload: 12000 lb.
Fuel Reserve: 1386 gal.

Mission 26
Date: 1945/2/4
Codename: Middleman #1
Target: Kobe Urban Area
Participating Units: 73rd & 313th BW
A/C Launched: 110
Altitude: 24500-27000
Time on Target: 15:57-16:56
Payload

73rd BW: 6830 lb.​

313th BW: 4880 lb.​

Fuel Reserve: 695 gal.
Losses: 2

Mission 27
Date: 1945/2/8
Codename: Panhandle #2
Target: Moen Island: Truk Airfield 1
Participating Unit: 313th BW
A/C Launched: 31
Altitude: 29500-30700'
Time on target: 10:57-11:33
Payload: 10000 lb.
Fuel Reserve: 1000 gal.

Mission 28
Date: 1945/2/9
Codename: Panhandle #3
Target: Moen Island: Truk Airfield 2
Participating Unit: 313th BW
A/C Launched: 30
Altitude: 24000-26000'
Time on Target: 11:19-11:21
Payload: 10000 lb.
Fuel Reserve: 1620 gal.

Mission 29
Date: 1945/2/10
Codename: Fraction #1
Target: Tokyo: Nakajima A/C Plant, Ota
Participating Units: 73rd & 313th BW
A/C Launched: 120
Altitude: 26000-29400'
Time on Target: 16:05-16:41
Payload

73rd BW: 6522 lb.​

313th BW: 5317 lb.​

Fuel Reserve: 576 gal.
Losses: 12

Mission 30
Date: 1945/2/11
Codename: Sea Search #1
Target: Enemy Picket Boats
Participating Unit: 313th BW
A/C Launched: 9
Search Area: 135°E - 148°E, 30°N & 60 miles to either side
Altitude: 3000'
ETA over Search Area: 15:18
Payload: 0 lb.
Fuel Reserve: Unspecified

Mission 31
Date: 1945/2/12
Codename: Starlit #3
Target: Iwo Jima: Heavy AA
Participating Unit: 313th BW
A/C Launched: 21
Altitude: 24000-24500'
Time on Target: 12:11-12:50
Payload: 8000 lb.
Fuel Reserve: 1015 gal.

Mission 32
Date: 1945/2/12
Codename: Sea Search #2
Target: Enemy Picket Boats
Participating Unit: 313th BW
A/C Launched: 10
Search Area: 135°E - 148°E, 30°N & 60 miles to either side
Altitude: 2000'
ETA over Search Area: 16:43-20:30
Payload: 0 lb.
Fuel Reserve: Unspecified
Losses: 1
Notes: Repeat of Mission #30

Mission 33
Date: 1945/2/14
Codename: Sea Search #3
Target: Enemy Picket Boats
Participating Unit: 313th BW
A/C Launched: 6
Search Area: 145°55'E - 148°E, 28°44'N
Altitude: 3000'
ETA over Search Area: 14:15-17:25
Payload: 0 lb.
Fuel Reserve: Unspecified

Mission 34
Date: 1945/2/15
Codename: Eradicate #4
Targets

Primary: Nagoya: Mitsubishi A/C Engine Plant​

Alternate: Hamamatsu Urban Area​

Participating Units: 73rd & 313th BW
A/C Launched: 117
Altitude: 25300-34000'
Time on Target: 15:02-15:55 (Primary)
Payload

73rd BW: 6000 lb.​

313th BW: 5000 lb.​

Fuel Reserve: 1191 gal.
Losses: 1

Mission 35
Date: 1945/2/17
Codename: Panhandle #4
Target: Dublon Island: Submarine Pens
Participating Unit: 73rd BW
A/C Launched: 9
Altitude: 26300-26900'
Time on Target: 16:46-16:47
Payload: 2500 lb.
Fuel Reserve: 1335 gal.
Notes: Odd to see such a low payload. All the other raids to Dublon Island saw loads around 10000 lb.

Mission 36
Date: 1945/2/18
Codename: Panhandle #5
Target: Dublon Island: Airfields 1 & 2
Participating Unit: 313th BW
A/C Launched: 36
Altitude: 24000-25900'
Time on Target: 12:27-13:40
Payload: 9492 lb.
Fuel Reserve: 1335 gal.

Mission 37
Date: 1945/2/19
Codename: Enkindle #4
Targets

Primary: Tokyo: Nakajima A/C Plant, Musashino​

Secondary: Tokyo Urban Area​

Participating Units: 73rd & 313th BW
A/C Launched: 150
Altitude: 24500-30000'
Time on Target: 15:49-16:47 (Secondary)
Payload

73rd BW: 6860 lb.​

313th BW: 5439 lb.​

Fuel Reserve: 955 gal.
Losses: 6

Mission 38
Date: 1945/2/25
Codename: Meetinghouse #1
Target: Tokyo Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 229
Altitude: 23500-31000'
Time on Target: 14:58-16:52
Payload

73rd BW: 7085 lb.​

313th BW: 5147 lb.​

314th BW: 3944 lb.​

Fuel Reserve: 883 gal.
Losses: 3
Notes: First raid to destroy over a square mile (28,000,000 square feet).

Mission 39
Date: 1945/3/4 - 3/5
Codename: Enkindle #5
Target: Tokyo: Nakajima A/C Plant, Musashino
Participating Units: 73rd & 313th BW
A/C Launched: 192
Altitude: 25100-28900'
Time on Target: 09:40-10:51 (Secondary)
Payload

73rd BW: 6833 lb.​

313th BW: 5646 lb.​

Fuel Reserve: 947 gal.
Losses: 1

Mission 40
Date: 1945/3/9 - 3/10
Codename: Meetinghouse #2
Target: Tokyo Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 325
Altitude: 4900-9100'
Time on Target: 01:07-04:00
Payload

73rd BW: 13880 lb.​

313th BW: 12857 lb.​

314th BW: 9673 lb.​

Fuel Reserve: 1044 gal.
Losses: 14
Notes: Employed a switch from high to moderate altitudes to low altitudes to increase bombing accuracy and reduce effects to fused artillery. Aircraft were had all guns but the tail-gun removed and the associated gun computer equipment, some armor was removed, and a slight fuel reduction was actually implemented. Since the aircraft weren't going to climb as high, it wasn't needed, and the payloads were increased. It was the most destructive raid carried out against Japan to that date in terms of surface area destroyed (469,146,000 square feet, or 16.8 square miles), possibly ever.

Mission 41
Date: 1945/3/11 - 3/12
Codename: Microscope #2
Target: Nagoya Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 310
Altitude: 5100-8500'
Time on Target: 01:19-04:17
Payload

73rd: 13880 lb.​

313th: 13695 lb.​

314th: 9827 lb.​

Fuel Reserve: 920 gal.
Losses: 1
Notes: A continuation of low-altitude night-bombing. Approximately 56,982,000 square feet (2.04 square miles) of urban area destroyed, either including, or in addition to, 394,660 square feet of the Aichi A/C plant at Eitoku, potentially adding up to 57,286,660 square feet (2.05 square miles) destroyed.

Mission 42
Date: 1945/3/13 - 3/14
Codename: Peachblow #1
Target: Osaka Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 298
Altitude: 5000-9400'
Time on Target: 00:57-04:25
Payload: 13739 lb.
Fuel Reserve: 1049 gal.
Losses: 2
Notes: 226,010,000 square feet (8.1 square miles) destroyed.

Mission 43
Date: 1945/3/16 - 3/17
Codename: Middleman #2
Target: Kobe Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 330
Altitude: 4600-9000'
Time on Target: 03:38-05:46
Payload: 14931 lb.
Fuel Reserve: 889 gal.
Losses: 3
Notes: 85,458,000 square feet (3.065 square miles) destroyed

Mission 44
Date: 1945/3/18 - 3/19
Codename: Microscope #3
Target: Nagoya Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 310
Altitude: 4500-9000'
Time on Target: 03:04-05:48
Payload: 13144 lb.
Fuel Reserve: 1085 gal.
Losses: 1
Notes: 82,000,000 square feet (2.94 square miles) destroyed, total damage to Nagoya from mission #41 is 139,800,000 square feet (5.01 square miles)

Mission 45
Date: 1945/3/24 - 3/25
Codename: Eradicate #5
Target: Nagoya: Mitsubishi A/C Engine Plant
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 248
Altitude: 5650-9800'
Time on Target: 01:00-02:17
Payload

73rd BW: 16957 lb.​

313th BW: 15330 lb.​

314th BW: 8784 lb.​

Fuel Reserve: 1021 gal.
Losses: 5

Mission 46
Date: 1945/3/27
Codename: Fearless #1
Targets

Kyushu Island: Tachiari & Oita Airfields​

Omura: A/C Factory​

Participating Units: 73rd & 314th BW
A/C Launched: 161
Altitude

Tachiari: 14500-18000'​

Oita: 15300-18300'​

Omura: 15000-16000'​

Time over Target

Tachiari: 11:40-12:05​

Oita: 11:44-12:59​

Omura: 12:06-12:20​

Payload: 6907 lb.
Fuel Reserve: 788 gal.

Mission 47
Date: 1945/3/27 - 3/28
Codename: Starvation #1
Target: Shimonoseki Straits
Participating Unit: 313th BW
A/C Launched: 102
Altitude

Love: 6000-8000'​

Mike: 4900-5400'​

Time over Target

Love: 00:10-01:42​

Mike: 23:37-01:06​

Payload: 12157 lb.
Fuel Reserve: 976 gal.
Losses: 3

Mission 48
Date: 1945/3/30 - 3/31
Codename: Eradicate #6
Target: Nagoya: Mitsubishi A/C Engine Plant
Participating Unit: 314th BW
A/C Launched: 14
Altitude: 6800-7910'
Time over Target: 00:46 - 01:50
Payload: 8682 lb.
Fuel Reserve: 852 gal.

Mission 49
Date: 1945/3/30 - 3/31
Codename: Starvation #2
Target: Shimonoseki Straits
Participating Unit: 313th BW
A/C Launched: 94
Altitude

Item: 4700-6000'​

Jig: 7800-8200'​

Love: 4850-5150'​

Roger: 6900-7450'​

Time on Target

Item: 01:24-03:48​

Jig: 00:53-01:41​

Love: 01:34-02:45​

Roger: 02:03-03:02​

Payload: 12094 lb.
Fuel Reserve: 879 gal.
Losses: 1

Mission 50
Date: 1945/3/31
Codename: Fearless #2
Targets: Kyushu Island: Tachiari Machine Works & Omura Airfield Installations
Participating Units: 73rd & 314th BW
A/C Launched: 149
Altitude

Tachiari: 14500-17050'​

Omura: 16000-18100'​

Time on Target

Tachiari: 11:40-12:19​

Omura: 11:51-12:42​

Payload: 7867 lb.
Fuel Reserve: 677 gal.
Losses: 1

Some patterns I've noticed

1. Missions to Truk were around 5000-6000 pounds (Mission 3: 5000#; Mission 1 & 2: 6000#), then increased to around 9000-11000 pounds (Mission 36: 9492#; Missions 6 & 27: 10000#; Mission 21: 11000#) with an unexpected drop to 2500 during one mission (mission 35): I'm not sure if the reason for the payload difference was due to availability of ordinance (i.e. they didn't get enough bombs to the airbases yet) or weather conditions?
2. Early missions to Tokyo had 10000 lb. of ordinance (Mission 7 & 8). Later that would go down to around 5000-7000 lb. Was this due to availability of ordinance or weather conditions? All the missions seemed to be from 23500'-34400' so the altitude seemed to have little bearing.

E emu27 , GrauGeist , S Shortround6

 

[GrauGeist]

Weather conditions could play a large part - note in the one bombing mission where the ground speed was noted to be over 450mph, this was due to the Jet Stream.

In the one mission where there was a light payload (#35?) - those may have been mines.

 

[Zipper730]

Weather conditions could play a large part - note in the one bombing mission where the ground speed was noted to be over 450mph, this was due to the Jet Stream.

Yeah, that's the most logical conclusion -- the B-29 couldn't fly that fast otherwise unless (maybe) it was in a dive.

In the one mission where there was a light payload (#35?) - those may have been mines.

It doesn't seem to be, as it was an attack on submarine pens. Submarine pens generally are struck with bombs (I'd assume armor piercing ones), right?

 

[GrauGeist]

It doesn't seem to be, as it was an attack on submarine pens. Submarine pens generally are struck with bombs (I'd assume armor piercing ones), right?

Mining the bay where the subs come and go either traps the subs in the pens or keeps them out - much easier than trying to bomb the pens themselves. The USAAF did use the B-29 to deploy a considerable amount of mines.
As far as bomb types used to penetrate the pens themselves, woukd be dictated by the construction of the pens. The Germans were masters of building bomb-proof pens, but I am not sure of the Japanese construction method.

 

[Reluctant Poster]

From the limited information I have, it seems the first operations listed here were out of the Marianas: Payloads and fuel reserves are averaged out

Mission 1
Date: 1944/10/27 - 10/28
Codename: Truk
Target: Dublon Island: Submarine Pens
Participating Unit: 73rd BW
A/C Launched: 18
Altitude: 25900-27450'
Time on Target: 08:55-09:00
Payload: 6000 lb.
Fuel Reserve: 1812 gal.

Mission 2
Date: 1944/10/30
Codename: Truk
Target: Dublon Island: Submarine Pens
Participating Unit: 73rd BW
A/C Launched: 18
Altitude: 25500-27450'
Time on Target: 11:00-11:03
Payload: 6000 lb.
Fuel Reserve: 2011 gal.

Mission 3
Date: 1944/11/2
Codename: Truk
Target: Dublon Island: Submarine Pens
Participating Unit: 73rd BW
A/C Launched: 20
Altitude: 25900-27300'
Time on Target: 10:34-11:35
Payload: 5000 lb.
Fuel Reserve: 2053 gal.

Mission 4
Date: 1944/11/5
Codename: Iwo Jima
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 73rd BW
A/C Launched: 36
Altitude: 26750-27500'
Time on Target: 16:23-16:39
Payload: 10000 lb.
Fuel Reserve: 1409 gal.

Mission 5
Date: 1944/11/8
Codename: Iwo Jima
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 73rd BW
A/C Launched: 17
Altitude: 27650-29000'
Time on Target: 12:32-12:34
Payload: 10000 lb.
Fuel Reserve: 1167 gal.
Losses: 1
Notes: If I read this right, the enemy dropped phosphorous bombs on B-29 formations. I only know of one or two other cases where bombers got bombed while in the air, one of which was the Scweinfurt Raids.

Mission 6
Date: 1944/11/11
Codename: Truk
Targets

Primary: Dublon Island: Submarine Base​

Secondary: Dublon Island: Shipping​

Participating Unit: 73rd BW
A/C Launched: 9
Altitude: 25000'
Time on Target: 13:55-13:57
Payload: 10000 lb.
Fuel Reserve: 2212 gal.

Mission 7
Date: 1944/11/24
Codename: San Antonio #1
Targets

Primary: Tokyo: Nakajima A/C Factory, Musashino​

Secondary: Tokyo Urban / Dock Area​

Participating Unit: 73rd BW
A/C Launched: 111
Altitude: 27000-32000'
Time on Target: 13:12-15:32 (Primary)
Payload: 10000 lb.
Fuel Reserve: 1048 gal.
Losses: 2
Notes: Groundspeed managed to reach 445 mph over target-area. Given the Norden bombsight's limit is around 450 mph, this would (among other things) explain problems with bombing accuracy.

Mission 8
Date: 1944/11/27
Codename: San Antonio #2
Targets

Primary: Tokyo: Nakajima A/C Factory, Musashino​

Secondary: Tokyo Urban / Dock Area​

Participating Unit: 73rd BW
A/C Launched: 81
Altitude

Primary: N/A​

Secondary: 27700-34000'​

Opportunity: 32500'​

Time on Target

Secondary: 13:47-15:25​

Opportunity: 14:20-14:23​

Payload: 10000 lb.
Fuel Reserve: 1093 gal.
Losses: 1
Notes: Japanese forces attacked Isley Field at Saipan during the course of this mission.

Mission 9
Date: 1944/11/29 - 11/30
Codename: Brooklyn #1
Targets

Primary: Tokyo Industrial Area​

Last Resort: Any Industrial City​

Participating Unit: 73rd BW
A/C Launched: 29
Altitude

Primary: 25000-33000'​

Last Resort: 21000-33200'​

Time on Target

Primary: 00:50-05:27​

Last Resort: 01:06-01:57​

Payload: 7000 lb.
Fuel Reserve: 1238 gal.
Losses: 1
Notes: Strange that the first to missions to Tokyo had an average of 10000 lb. of ordinance, and it was now reduced to 7000 lb.

Mission 10
Date: 1944/12/3
Codename: San Antonio #3
Targets

Primary: Tokyo: Nakajima A/C Factory, Musashino​

Secondary: Tokyo: Docks & Urban Area​

Participating Unit: 73rd BW
A/C Airborne: 86
Altitude: 16000-33100'
Time on Target: 05:03-06:30 (Primary)
Payload: 5000 lb.
Fuel Reserve: 815 gal.
Losses: 5
Notes: This seems to be the first mission where the altitude was below 20000'. The large spread in altitudes appears to be aimed at splitting the air-defenses up.

Mission 11
Date: 1944/12/8
Codename: Sledgehammer #1
Targets

Primary: Iwo Jima: Airfields​

Secondary: Pagan Island​

Participating Unit: 73rd BW
A/C Launched: 79
Altitude: 19670-23400'
Time on Target: 10:20-11:50 (Primary)
Payload: 20000 lb.
Fuel Reserve: 1454 gal.
Notes: 3 x B-29's listed in the total provided navigation for 28 x P-38's.

Mission 12
Date: 1944/12/13
Codename: Memphis #1
Targets

Primary: Nagoya: Mitsubishi A/C Engine Plant​

Secondary: Nagoya Urban Area​

Last Resort: Any Industrial City​

Participating Unit: 73rd BW
A/C Launched: 90
Altitude: 26450-32300'
Time on Target: 14:57-16:38 (Primary)
Payload: 5000 lb.
Fuel Reserve: 783 gal.
Losses: 4

Mission 13
Date: 1944/12/18
Codename: Hesitation #1
Target: Nagoya: Mitsubishi A/C Plant
Participating Unit: 73rd BW
A/C Launched: 89
Altitude: 28000-32000'
Time on Target: 14:00-15:43
Payload: 5000 lb.
Fuel Reserve: 705 gal.
Losses: 4

Mission 14
Date: 1944/12/22
Codename: Eradicate #2
Target: Nagoya: Mitsubishi A/C Engine Factory
Participating Unit: 73rd BW
A/C Launched: 78
Altitude: 28800-32600'
Time on Target: 14:04-15:58
Payload: 5500 lb.
Fuel Reserve: 1045 gal.
Losses: 3

Mission 15
Date: 1944/12/24
Codename: Rockcrusher #1
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 73rd BW
A/C Launched: 29
Fighter Sweep: Unspecified
Altitude: 19500-21800'
Time on Target: 14:24-15:35
Payload: 10000 lb.
Fuel Reserve: 1832 gal.
Notes: 3 x B-29's not included provided navigation for a fighter-sweep. The lower altitudes on this mission and Mission #11 might be more for the benefit of the fighter-sweep than the bomber.

Mission 16
Date: 1944/12/27
Codename: Enkindle #1
Target: Tokyo: Nakajima A/C Plant, Musashino
Participating Unit: 73rd BW
A/C Launched: 72
Altitude: 28200-33800'
Time on Target: 13:42-15:03
Payload: 5500 lb.
Fuel Reserve: 1200 gal.
Losses: 3

Mission 17
Date: 1945/1/3
Codename: Microscope #1
Target: Nagoya: Docks & Urban Area
Participating Unit: 73rd BW
A/C Launched: 97
Altitude: 28200-31500'
Time on Target: 15:45-16:33
Payload: 5300 lb.
Fuel Reserve: 761 gal.
Losses: 5

Mission 18
Date: 1945/1/9
Codename: Enkindle #2
Target: Tokyo: Nakajima A/C Plant, Musashino
Participating Unit: 73rd BW
A/C Launched: 72
Altitude: 29500-34400'
Time on Target: 15:13-15:35
Payload: 5000 lb.
Fuel Reserve: 1174 gal.
Losses: 6

Mission 19
Date: 1945/1/14
Codename: Hesitation #2
Target: Nagoya: Mitsubishi A/C Plant
Participating Unit: 73rd BW
A/C Launched: 73
Altitude: 29080-32000'
Time on Target: 15:40-16:28
Payload: 5000 lb.
Fuel Reserve: 909 gal.
Losses: 5

Mission - None Assigned
Date: 1945/1/16
Codename: Fagan Island
Target: Fagan Island: Airstrip
Participating Unit: 313th BW
A/C Launched: 44
Altitude: 28300-28400'
Time on Target: 11:33-17:54
Payload: 12000 lb.
Fuel Reserve: 1854 gal.
Notes: Shakedown mission.

Mission 20
Date: 1945/1/19
Codename: Fruitcake #1
Target: Osaka: Kawasaki A/C Plant, Akashi
Participating Unit: 73rd BW
A/C Launched: 80
Altitude: 25100-27400'
Time on Target: 14:50-15:24
Payload: 5000 lb.
Fuel Reserve: 1057 gal.

Mission 21
Date: 1945/1/21
Codename: Panhandle #1
Target: Moen Island: Airfield
Participating Unit: 313th BW
A/C Launched: 33
Altitude: 25500-26000'
Time on Target: 10:34-11:08
Payload: 11000 lb.
Fuel Reserve: 1817 gal

Mission 22
Date: 1945/1/23
Codename: Eradicate #3
Target: Nagoya: Mitsubishi A/C Engine Plant
Participating Unit: 73rd BW
A/C Launched: 73
Altitude: 25300-27200'
Time on Target: 05:35-05:47
Payload: 6000 lb.
Fuel Reserve: 1053 gal.
Losses: 2

Mission 23
Date: 1945/1/24
Codename: Starlit #1
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 313th BW
A/C Launched: 28
Altitude: 26000-28000'
Time on Target: 12:28-13:30
Payload: 12000 lb.
Fuel Reserve: 1622 gal.

Mission 24
Date: 1945/1/27
Codename: Enkindle #3
Targets

Primary: Tokyo: Nakajima A/C Plant, Musashino​

Secondary: Tokyo Urban Area​

Participating Unit: 73rd BW
A/C Launched: 74
Altitude: 24500-29600'
Time on Target: 15:04-15:58
Payload: 6000 lb.
Fuel Reserve: 1059 gal.
Losses: 9

Mission 25
Date: 1945/1/29
Codename: Starlit #2
Target: Iwo Jima: Airfields 1 & 2
Participating Unit: 313th BW
A/C Launched: 33
Altitude: 23000-25200'
Time on Target: 14:28-14:47
Payload: 12000 lb.
Fuel Reserve: 1386 gal.

Mission 26
Date: 1945/2/4
Codename: Middleman #1
Target: Kobe Urban Area
Participating Units: 73rd & 313th BW
A/C Launched: 110
Altitude: 24500-27000
Time on Target: 15:57-16:56
Payload

73rd BW: 6830 lb.​

313th BW: 4880 lb.​

Fuel Reserve: 695 gal.
Losses: 2

Mission 27
Date: 1945/2/8
Codename: Panhandle #2
Target: Moen Island: Truk Airfield 1
Participating Unit: 313th BW
A/C Launched: 31
Altitude: 29500-30700'
Time on target: 10:57-11:33
Payload: 10000 lb.
Fuel Reserve: 1000 gal.

Mission 28
Date: 1945/2/9
Codename: Panhandle #3
Target: Moen Island: Truk Airfield 2
Participating Unit: 313th BW
A/C Launched: 30
Altitude: 24000-26000'
Time on Target: 11:19-11:21
Payload: 10000 lb.
Fuel Reserve: 1620 gal.

Mission 29
Date: 1945/2/10
Codename: Fraction #1
Target: Tokyo: Nakajima A/C Plant, Ota
Participating Units: 73rd & 313th BW
A/C Launched: 120
Altitude: 26000-29400'
Time on Target: 16:05-16:41
Payload

73rd BW: 6522 lb.​

313th BW: 5317 lb.​

Fuel Reserve: 576 gal.
Losses: 12

Mission 30
Date: 1945/2/11
Codename: Sea Search #1
Target: Enemy Picket Boats
Participating Unit: 313th BW
A/C Launched: 9
Search Area: 135°E - 148°E, 30°N & 60 miles to either side
Altitude: 3000'
ETA over Search Area: 15:18
Payload: 0 lb.
Fuel Reserve: Unspecified

Mission 31
Date: 1945/2/12
Codename: Starlit #3
Target: Iwo Jima: Heavy AA
Participating Unit: 313th BW
A/C Launched: 21
Altitude: 24000-24500'
Time on Target: 12:11-12:50
Payload: 8000 lb.
Fuel Reserve: 1015 gal.

Mission 32
Date: 1945/2/12
Codename: Sea Search #2
Target: Enemy Picket Boats
Participating Unit: 313th BW
A/C Launched: 10
Search Area: 135°E - 148°E, 30°N & 60 miles to either side
Altitude: 2000'
ETA over Search Area: 16:43-20:30
Payload: 0 lb.
Fuel Reserve: Unspecified
Losses: 1
Notes: Repeat of Mission #30

Mission 33
Date: 1945/2/14
Codename: Sea Search #3
Target: Enemy Picket Boats
Participating Unit: 313th BW
A/C Launched: 6
Search Area: 145°55'E - 148°E, 28°44'N
Altitude: 3000'
ETA over Search Area: 14:15-17:25
Payload: 0 lb.
Fuel Reserve: Unspecified

Mission 34
Date: 1945/2/15
Codename: Eradicate #4
Targets

Primary: Nagoya: Mitsubishi A/C Engine Plant​

Alternate: Hamamatsu Urban Area​

Participating Units: 73rd & 313th BW
A/C Launched: 117
Altitude: 25300-34000'
Time on Target: 15:02-15:55 (Primary)
Payload

73rd BW: 6000 lb.​

313th BW: 5000 lb.​

Fuel Reserve: 1191 gal.
Losses: 1

Mission 35
Date: 1945/2/17
Codename: Panhandle #4
Target: Dublon Island: Submarine Pens
Participating Unit: 73rd BW
A/C Launched: 9
Altitude: 26300-26900'
Time on Target: 16:46-16:47
Payload: 2500 lb.
Fuel Reserve: 1335 gal.
Notes: Odd to see such a low payload. All the other raids to Dublon Island saw loads around 10000 lb.

Mission 36
Date: 1945/2/18
Codename: Panhandle #5
Target: Dublon Island: Airfields 1 & 2
Participating Unit: 313th BW
A/C Launched: 36
Altitude: 24000-25900'
Time on Target: 12:27-13:40
Payload: 9492 lb.
Fuel Reserve: 1335 gal.

Mission 37
Date: 1945/2/19
Codename: Enkindle #4
Targets

Primary: Tokyo: Nakajima A/C Plant, Musashino​

Secondary: Tokyo Urban Area​

Participating Units: 73rd & 313th BW
A/C Launched: 150
Altitude: 24500-30000'
Time on Target: 15:49-16:47 (Secondary)
Payload

73rd BW: 6860 lb.​

313th BW: 5439 lb.​

Fuel Reserve: 955 gal.
Losses: 6

Mission 38
Date: 1945/2/25
Codename: Meetinghouse #1
Target: Tokyo Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 229
Altitude: 23500-31000'
Time on Target: 14:58-16:52
Payload

73rd BW: 7085 lb.​

313th BW: 5147 lb.​

314th BW: 3944 lb.​

Fuel Reserve: 883 gal.
Losses: 3
Notes: First raid to destroy over a square mile (28,000,000 square feet).

Mission 39
Date: 1945/3/4 - 3/5
Codename: Enkindle #5
Target: Tokyo: Nakajima A/C Plant, Musashino
Participating Units: 73rd & 313th BW
A/C Launched: 192
Altitude: 25100-28900'
Time on Target: 09:40-10:51 (Secondary)
Payload

73rd BW: 6833 lb.​

313th BW: 5646 lb.​

Fuel Reserve: 947 gal.
Losses: 1

Mission 40
Date: 1945/3/9 - 3/10
Codename: Meetinghouse #2
Target: Tokyo Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 325
Altitude: 4900-9100'
Time on Target: 01:07-04:00
Payload

73rd BW: 13880 lb.​

313th BW: 12857 lb.​

314th BW: 9673 lb.​

Fuel Reserve: 1044 gal.
Losses: 14
Notes: Employed a switch from high to moderate altitudes to low altitudes to increase bombing accuracy and reduce effects to fused artillery. Aircraft were had all guns but the tail-gun removed and the associated gun computer equipment, some armor was removed, and a slight fuel reduction was actually implemented. Since the aircraft weren't going to climb as high, it wasn't needed, and the payloads were increased. It was the most destructive raid carried out against Japan to that date in terms of surface area destroyed (469,146,000 square feet, or 16.8 square miles), possibly ever.

Mission 41
Date: 1945/3/11 - 3/12
Codename: Microscope #2
Target: Nagoya Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 310
Altitude: 5100-8500'
Time on Target: 01:19-04:17
Payload

73rd: 13880 lb.​

313th: 13695 lb.​

314th: 9827 lb.​

Fuel Reserve: 920 gal.
Losses: 1
Notes: A continuation of low-altitude night-bombing. Approximately 56,982,000 square feet (2.04 square miles) of urban area destroyed, either including, or in addition to, 394,660 square feet of the Aichi A/C plant at Eitoku, potentially adding up to 57,286,660 square feet (2.05 square miles) destroyed.

Mission 42
Date: 1945/3/13 - 3/14
Codename: Peachblow #1
Target: Osaka Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 298
Altitude: 5000-9400'
Time on Target: 00:57-04:25
Payload: 13739 lb.
Fuel Reserve: 1049 gal.
Losses: 2
Notes: 226,010,000 square feet (8.1 square miles) destroyed.

Mission 43
Date: 1945/3/16 - 3/17
Codename: Middleman #2
Target: Kobe Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 330
Altitude: 4600-9000'
Time on Target: 03:38-05:46
Payload: 14931 lb.
Fuel Reserve: 889 gal.
Losses: 3
Notes: 85,458,000 square feet (3.065 square miles) destroyed

Mission 44
Date: 1945/3/18 - 3/19
Codename: Microscope #3
Target: Nagoya Urban Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 310
Altitude: 4500-9000'
Time on Target: 03:04-05:48
Payload: 13144 lb.
Fuel Reserve: 1085 gal.
Losses: 1
Notes: 82,000,000 square feet (2.94 square miles) destroyed, total damage to Nagoya from mission #41 is 139,800,000 square feet (5.01 square miles)

Mission 45
Date: 1945/3/24 - 3/25
Codename: Eradicate #5
Target: Nagoya: Mitsubishi A/C Engine Plant
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 248
Altitude: 5650-9800'
Time on Target: 01:00-02:17
Payload

73rd BW: 16957 lb.​

313th BW: 15330 lb.​

314th BW: 8784 lb.​

Fuel Reserve: 1021 gal.
Losses: 5

Mission 46
Date: 1945/3/27
Codename: Fearless #1
Targets

Kyushu Island: Tachiari & Oita Airfields​

Omura: A/C Factory​

Participating Units: 73rd & 314th BW
A/C Launched: 161
Altitude

Tachiari: 14500-18000'​

Oita: 15300-18300'​

Omura: 15000-16000'​

Time over Target

Tachiari: 11:40-12:05​

Oita: 11:44-12:59​

Omura: 12:06-12:20​

Payload: 6907 lb.
Fuel Reserve: 788 gal.

Mission 47
Date: 1945/3/27 - 3/28
Codename: Starvation #1
Target: Shimonoseki Straits
Participating Unit: 313th BW
A/C Launched: 102
Altitude

Love: 6000-8000'​

Mike: 4900-5400'​

Time over Target

Love: 00:10-01:42​

Mike: 23:37-01:06​

Payload: 12157 lb.
Fuel Reserve: 976 gal.
Losses: 3

Mission 48
Date: 1945/3/30 - 3/31
Codename: Eradicate #6
Target: Nagoya: Mitsubishi A/C Engine Plant
Participating Unit: 314th BW
A/C Launched: 14
Altitude: 6800-7910'
Time over Target: 00:46 - 01:50
Payload: 8682 lb.
Fuel Reserve: 852 gal.

Mission 49
Date: 1945/3/30 - 3/31
Codename: Starvation #2
Target: Shimonoseki Straits
Participating Unit: 313th BW
A/C Launched: 94
Altitude

Item: 4700-6000'​

Jig: 7800-8200'​

Love: 4850-5150'​

Roger: 6900-7450'​

Time on Target

Item: 01:24-03:48​

Jig: 00:53-01:41​

Love: 01:34-02:45​

Roger: 02:03-03:02​

Payload: 12094 lb.
Fuel Reserve: 879 gal.
Losses: 1

Mission 50
Date: 1945/3/31
Codename: Fearless #2
Targets: Kyushu Island: Tachiari Machine Works & Omura Airfield Installations
Participating Units: 73rd & 314th BW
A/C Launched: 149
Altitude

Tachiari: 14500-17050'​

Omura: 16000-18100'​

Time on Target

Tachiari: 11:40-12:19​

Omura: 11:51-12:42​

Payload: 7867 lb.
Fuel Reserve: 677 gal.
Losses: 1

Some patterns I've noticed

1. Missions to Truk were around 5000-6000 pounds (Mission 3: 5000#; Mission 1 & 2: 6000#), then increased to around 9000-11000 pounds (Mission 36: 9492#; Missions 6 & 27: 10000#; Mission 21: 11000#) with an unexpected drop to 2500 during one mission (mission 35): I'm not sure if the reason for the payload difference was due to availability of ordinance (i.e. they didn't get enough bombs to the airbases yet) or weather conditions?
2. Early missions to Tokyo had 10000 lb. of ordinance (Mission 7 & 8). Later that would go down to around 5000-7000 lb. Was this due to availability of ordinance or weather conditions? All the missions seemed to be from 23500'-34400' so the altitude seemed to have little bearing.

E emu27 , GrauGeist , S Shortround6

For mission 40 all guns but tail guns removed. Did the tail guns still include the 20 mm?

 

[Zipper730]

R Reluctant Poster : Good question, I honestly don't know

 

[Zipper730]

Continuing from previous listing

Mission 51
Date: 1945/4/1 - 4/2
Codename: Enkindle #6
Target: Tokyo: Nakajima A/C Factory, Musashino
Participating Unit: 73rd BW
A/C Launched: 121
Altitude: 5830' - 7960'
Time on Target: 03:01-04:43
Payload: 19428 lb.
Losses: 6
Fuel Reserve: 737 gal.
Notes: Increase in payload seems to certainly indicate the merits of the lower altitude attack profile, though I'm not certain the altitude that was flown on the way in and out (just over the target).

Mission 52
Date: 1945/4/1
Codename: Starvation #3
Target: Kure Harbor: Minefield How
Participating Unit: 313th BW
A/C Launched: 6
Altitude: 25700' - 26460'
Time on Target: 23:02-23:33
Payload: 8000 lb.
Fuel Reserve: Unspecified

Mission 53
Date: 1945/4/2 - 4/3
Codename: Starvation #4
Target: Hiroshima Area: Minefield Item
Participating Unit: 313th BW
A/C Launched: 10
Altitude: 6000' - 6100'
Time on Target: 01:16-01:36
Payload: 12354 lb.
Fuel Reserve: Unspecified

Mission 54
Date: 1945/4/3 - 4/4
Codename: Starvation #5
Target: Hiroshima Area: Minefield Item
Participating Unit: 313th BW
A/C Launched: 9
Altitude: 6000' - 6150'
Time on Target: 00:10-00:45
Payload: 12000 lb.
Fuel Reserve: Unspecified

Mission 55
Date: 1945/4/3 - 4/4
Codename: Upcast #1
Target: Shizuoka: A/C Plant
Participating Unit: 314th BW
A/C Launched: 49
Altitude: 7000' - 8875'
Time on Target: 02:30-04:35
Payload: 9300 lb.
Fuel Reserve: 1126 gal.

Mission 56
Date: 1945/4/3 - 4/4
Codename: Furious #1
Targets

Primary: Koizumi: Nakajima A/C Factory​

Secondary: Tokyo Urban Area​

Participating Unit: 313th BW
A/C Launched: 68
Altitude: 7200' - 7950'
Time on Target: 02:14-03:41 (Primary)
Payload: 14829 lb.
Fuel Reserve: 947 gal.

Mission 57
Date: 1945/4/3 - 4/4
Codename: Modeller #1
Targets

Primary: Tachigawa: Tachigawa A/C Company​

Secondary: Kawasaki Urban Area​

Participating Unit: 73rd BW
A/C Launched: 113
Altitude: 5700' - 7200'
Time on Target: 03:30-05:34 (Primary)
Payload: 17959 lb.
Fuel Reserve: 796 gal.
Losses: 1
Notes: Some kind of ball of fire was seen following the aircraft: "Foo Fightas!"

Mission 58
Date: 1945/4/7
Codename: Enkindle #7
Target: Tokyo: Nakajima A/C Plant, Musashino
Participating Unit: 73rd BW
A/C Launched: 107
Escort: 97 P-51's
Altitude: 11500' - 15650'
Time on Target: 11:00-11:06
Payload: 10275 lb.
Fuel Reserve: 547 gal.
Losses

B-29: 3​

P-51: 2​

Mission 59
Date: 1945/4/7
Codename: Eradicate #7
Target: Nagoya: Mitsubishi A/C Engine Plant
Participating Units: 313th & 314th BW
A/C Launched: 194
Altitude: 16000' - 25000'
Time on Target: 12:00 - 13:54
Payload

313th BW: 8776 lb.​

314th BW: 8993 lb.​

Fuel Reserve

313th BW: 975 gal.​

314th BW: 754 gal.​

Losses: 2

Mission 60
Date: 1945/4/8
Codename: Checkbook #1
Targets

Primary Visual: Kyushu Island: Kanoya Airfield​

Primary Radar: Kagoshima: Urban Area​

Secondary: Kyushu Island: Izumi Airfield​

Participating Unit: 73rd BW
A/C Launched: 32
Altitude: 17400' - 19300'
Time on Target: 11:29-11:53 (Primary Radar)
Payload: 8560 lb.
Fuel Reserve: 639 gal.

Mission 61
Date: 1945/4/8
Codename: Famish #1
Targets

Primary Visual: Kyushu Island: Kanoya East Airfield​

Primary Radar: Kagoshima Urban Area​

Secondary: Kyushu Island: Kokubu Airfield​

Participating Unit: 313th BW
A/C Launched: 21
Altitude

Primary Visual: 17010' - 17800'​

Primary Radar: 17000' - 18800'​

Time on Target

Primary Visual: 11:32​

Primary Radar: 11:32-11:53​

Payload: 9095 lb.
Fuel Reserve: 1076 gal.
Losses: 1

Mission 62
Date: 1945/4/9 - 4/10
Codename: Starvation #6
Target: Shimonoseki Straits
Participating Unit: 313th BW
A/C Launched: 20
Altitude: 5000' - 6300'
Time over Target: 01:40-02:16
Payload: 12000 lb.
Fuel Reserve: Unspecified

Mission 63
Date: 1945/4/12
Codename: Enkindle #8
Target: Tokyo: Nakajima A/C Factory, Musashino
Participating Unit: 73rd BW
A/C Launched: 114
Altitude: 12000' - 17500'
Time over Target: 12:08-12:21
Payload: 10762 lb.
Fuel Reserve: 532 gal.

Mission 64
Date: 1945/4/12
Codename: Butterball #1
Target: Koriyama: Hodagaya Chemical Company
Participating Unit: 313th BW
A/C Launched: 82
Altitude: 7000' - 15000'
Time over Target: 12:20-13:30
Payload: 8939 lb.
Fuel Reserve: 948 gal.

Mission 65
Date: 1945/4/12
Codename: Lunchroom #1
Target: Koriyama: Chemical Plant
Participating Unit: 314th BW
A/C Launched: 85
Altitude: 7000' - 9000'
Time over Target: 12:33-13:28
Payload: 5342 lb.
Fuel Reserve: 927 gal.
Losses: 2

Mission 66
Date: 1945/4/12 - 4/13
Codename: Starvation #7
Target: Shimonoseki Straits: Minefield Love
Participating Unit: 313th BW
A/C Launched: 5
Altitude: 6850' - 7110'
Time on Target: 01:46-02:16
Payload: 8000 lb.
Fuel Reserve: Unspecified

Mission 67
Date: 1945/4/13 - 4/14
Codename: Perdition #1
Target: Tokyo: Arsenal Area
Participating Units: 73rd, 313th & 314th BW
A/C Launched: 348
Altitude: 6750' - 11000'
Time on Target: 23:57 - 03:36
Payload

73rd BW: 16887 lb.​

313th BW: 15125 lb.​

314th BW: 9409 lb.​

Fuel Reserve: 1158 gal.
Losses: 7
Notes: 296,000,000 square feet (10.6 square miles) of destroyed

Mission 68
Date: 1945/4/15 - 4/16
Codename: Brisket #1
Target: Kawasaki Urban Area
Participating Units: 313th & 314th BW
A/C Launched: 219
Altitude: 6420' - 10020'
Time on Target: 23:43-01:56
Payload

313th BW: 14985 lb.​

314th BW: 9659 lb.​

Fuel Reserve

313th BW: 1065 gal.​

314th BW: 1060 gal.​

Losses: 12
Notes: 80,920,000 square feet (2.9 square miles) destroyed

Mission 69
Date: 1945/4/15 - 4/16
Codename: Arrange #1
Target: Tokyo Urban Area
Participating Unit: 73rd BW
A/C Launched: 118
Altitude: 8000' - 10110'
Time on Target: 23:25-00:55
Payload: 14784 lb.
Fuel Reserve: 893 gal.
Losses: 1
Notes: Total damage to Tokyo to this date is 909,826,000 (32.64 square miles).

Mission 70
Date: 1945/4/17
Codename: Bullish #1
Target: Kyushu Island: Izumi Airfield
Participating Unit: 73rd BW
A/C Launched: 22
Altitude: 15000' - 16100'
Time on Target: 15:28-15:29
Payload: 8480 lb.
Fuel Reserve: 714 gal.

Mission 71
Date: 1945/4/17
Codename: Aghast #1
Target: Kyushu Island: Tachiari Airfield
Participating Unit: 73rd BW
A/C Launched: 21
Altitude: 15000' - 16000'
Time on Target: 15:51 - 16:00
Payload: 8544 lb.
Fuel Reserve: 706 gal.

Mission 72
Date: 1945/4/17
Codename: Barranca #1
Target: Kyushu Island: Kokubu Airfield
Participating Unit: 313th BW
A/C Launched: 24
Altitude: 17300'
Time on Target: 15:30-15:38
Payload: 13780 lb.
Fuel Reserve: 878 gal.

Mission 73
Date: 1945/4/17
Codename: Famish #2
Target: Kyushu Island: Kanoya East Airfield
Participating Unit: 73rd BW
A/C Airborne: 22
Altitude: 16000' - 17300'
Time on Target: 15:47-15:50
Payload: 11780 lb.
Fuel Reserve: 949 gal.

Mission 74
Date: 1945/4/17
Codename: Bushing #1
Target: Kyushu Island: Nittagahara Airfield
Participating Unit: 314th BW
A/C Launched: 10
Altitude: 18000' - 18500'
Time on Target: 16:10 (Primary)
Payload: 5950 lb.
Fuel Reserve: 1516 gal.

Mission 75
Date: 1945/4/17
Codename: Checkbook #2
Target: Kyushu Island: Kanoya Airfield
Participating Unit: 314th BW
A/C Launched: 34
Altitude: 17800' - 19400'
Time on Target: 15:38-15:44
Payload: 4888 lb.
Fuel Reserve: 1436 gal.

Mission 76
Date: 1945/4/18
Codename: Aghast #2
Targets

Visual: Kyushu Island: Tachiari Arfield​

Radar: Kyushu Island: Omura Airfield​

Participating Unit: 73rd BW
A/C Launched: 21
Altitude: 15000' - 15400'
Time on Target: 08:41 - 08:54 (Primary)
Payload: 8472 lb.
Fuel Reserve: 557 gal.
Losses: 2

Mission 77
Date: 1945/4/18
Codename: Famish #3
Targets

Visual: Kyushu Island: Kanoya East Airfield​

Radar: Kyushu Island: Kokubu Airfield​

Participating Unit: 313th BW
A/C Launched: 20
Altitude: 16000' - 16800'
Time on Target: 08:50-09:17 (Primary)
Payload: 12000 lb.
Fuel Reserve: 780 gal.

Mission 78
Date: 1945/4/18
Codename: Checkbook #3
Targets

Visual: Kyushu Island: Kanoya Airfield​

Radar: Kyushu Island: Kanoya East Airfield​

Participating Unit: 314th BW
A/C Launched: 33
Altitude: 18000' - 19140'
Time on Target: 08:50-08:58 (Primary)
Payload: 5718 lb.
Fuel Reserve: 1299 gal.

Mission 79
Date: 1945/4/18
Codename: Bullish #2
Targets

Visual: Kyushu Island: Izumi Airfield​

Radar: Kyushu Island: Kokubu Airfield​

Participating Unit: 73rd BW
A/C Launched: 23
Altitude: 15390' - 16300'
Time on Target: 08:29 - 08:58 (Primary)
Payload: 8449 lb.
Fuel Reserve: 943 gal.

Mission 80
Date: 1945/4/18
Codename: Barranca #2
Targets

Primary: Kyushu Island: Kokubu Airfield​

Secondary: Kyushu Island: Izumi Airfield​

Participating Unit: 313th BW
A/C Launched: 22
Altitude: 15600' - 17000'
Time on Target: 08:45-09:01 (Primary)
Payload: 14390 lb.
Fuel Reserve: 933 gal.

Mission 81
Date: 1945/4/18
Codename: Bushing #2
Targets

Visual: Kyushu Island: Nittagahara Airfield​

Radar: Kyushu Island: Miyazaki Airfield​

Participating Unit: 313th BW
A/C Launched: 11
Altitude: 18000' - 18200'
Time on Target: 10:03-10:23 (Primary)
Payload: 5950 lb.
Fuel Reserve: 1047 gal.

Mission 82
Date: 1945/4/21
Codename: Camlet #1
Target: Kyushu Island: Oita Airfield
Participating Units: 73rd BW
A/C Launched: 30
Altitude: 14300' - 15300'
Time on Target: 07:55-07:56
Payload: 10165 lb.
Fuel Reserve: 801 gal.

Mission 83
Date: 1945/4/21
Codename: Famish #4
Target: Kyushu Island: Kanoya East Airfield
Participating Unit: 313th BW
A/C Launched: 33
Altitude: 16200' - 17350'
Time on Target: 08:09-09:01
Payload: 13245 lb.
Fuel Reserve: 704 gal.

Mission 84
Date: 1945/4/21
Codename: Checkbook #4
Target: Kyushu Island: Kanoya Airfield
Participating Unit: 313th BW
A/C Launched: 33
Altitude: 16000' - 17800'
Time on Target: 08:04-08:35
Payload: 9080 lb.
Fuel Reserve: 1107 gal.

Mission 85
Date: 1945/4/21
Codename: Blowzy #1
Target: Kyushu Island: Usa Airfield
Participating Units: 73rd BW
A/C Launched: 30
Altitude: 14500' - 15800'
Time on Target: 09:11-09:22
Payload: 10165 lb.
Fuel Reserve: 716 gal.

Mission 86
Date: 1945/4/21
Codename: Barranca #3
Target: Kyushu Island: Kokubu Airfield
Participating Unit: 313th BW
A/C Launched: 35
Target: Kyushu Island: Kokubu Airfield
Altitude: 12000' - 14000'
Time on Target: 09:20-09:53
Payload: 12885 lb.
Fuel Reserve: 835 gal.

Mission 87
Date: 1945/4/21
Codename: Aeroscope #1
Target: Kyushu Island: Kushira Airfield
Participating Unit: 314th BW
A/C Launched: 31
Altitude: 17400' - 17675'
Time on Target: 09:59-10:07
Payload: 9492 lb.
Fuel Reserve: 1120 gal.

Mission 88
Date: 1945/4/21
Codename: Aghast #3
Target: Kyushu Island: Tachiari Airfield
Participating Unit: 73rd BW
A/C Launched: 21
Altitude: 18500' - 19200'
Time on Target: 10:03-10:04
Payload: 10165 lb.
Fuel Reserve: 555 gal.

Mission 89
Date: 1945/4/21
Codename: Bullish #3
Target: Kyushu Island: Izumi Airfield
Participating Unit: 313th BW
A/C Launched: 16
Altitude: 14100' - 14500'
Time on Target: 08:14-09:49
Payload: 13643 lb.
Fuel Reserve: 744 gal.

Mission 90
Date: 1945/4/21
Codename: Bushing #3
Target: Kyushu Island: Nittagahara Airfield
Participating Unit: 313th BW
A/C Launched: 23
Altitude: 15000' - 16500'
Time on Target: 09:25-09:34
Payload: 8845 lb.
Fuel Reserve: 949 gal.

Mission 91
Date: 1945/4/22
Codename: Bullish #4
Target: Kyushu Island: Izumi Airfield
Participating Units: 73rd BW
A/C Launched: 21
Altitude: 16000' - 18000'
Time on Target: 08:52-09:05
Payload: 9095 lb.
Fuel Reserve: 958 gal.

Mission 92
Date: 1945/4/22
Codename: Aeroscope #2
Target: Kyushu Island: Kushira Airfield
Participating Unit: 313th BW
A/C Launched: 18
Altitude: 16000' - 16600'
Time on Target: 08:58-09:45
Payload: 9363 lb.
Fuel Reserve: 1083 gal.

Mission 93
Date: 1945/4/22
Codename: Neckcloth #1
Target: Kyushu Island: Miyazaki Airfield
Participating Unit: 314th BW
A/C Launched: 22
Altitude: 14000' - 17500'
Time on Target: 08:34-10:10
Payload: 9217 lb.
Fuel Reserve: 1095 gal.

Mission 94
Date: 1945/4/22
Codename: Skewer #1
Target: Kyushu Island: Tomitaka Airfield
Participating Unit: 73rd BW
A/C Launched: 18
Altitude: 16450' - 17500'
Time on Target: 09:36
Payload: 9095 lb.
Fuel Reserve: 1194 gal.

Mission 95
Date: 1945/4/22
Codename: Checkbook #5
Target: Kyushu Island: Kanoya Airfield
Participating Unit: 313th BW
A/C Launched: 25
Altitude: 15350' - 15950'
Time on Target: 08:34-09:36
Payload: 9091 lb.
Fuel Reserve: 1079 gal.
Losses: 1
Notes: Over the course of 5 days, 474 sorties were launched against 10 airfields on Kyushu Island with 4 losses.

Mission 96
Date: 1945/4/24
Codename: Catcall #1
Targets

Primary: Higashiyamato: Hitachi A/C Factory​

Secondary: Shizuoka: Tachigawa A/C Factory​

Participating Units: 73rd, 313th & 314th BW
A/C Launched: 131
Altitude: 10000' - 14500'
Time on Target: 09:52-10:06 (Primary)
Payload

73rd BW: 9898 lb.​

313th BW: 10058 lb.​

314th BW: 10063 lb.​

Fuel Reserve

73rd BW: 855 gal.​

313th BW: 1077 gal.​

314th BW: 1070 gal.​

Losses: 5

Mission 97
Date: 1945/4/26
Codename: Blowzy #2
Target: Kyushu Island: Usa Airfield
Participating Unit: 73rd BW
A/C Launched: 21
Altitude: 15500' - 26500'
Time on Target: 08:16-08:44
Payload: 9095 lb.
Fuel Reserve: 1023 gal.

Mission 98
Date: 1945/4/26
Codename: Camlet #2
Target: Kyushu Island: Oita Airfield
Participating Unit: 73rd BW
A/C Launched: 22
Altitude: 13500' - 24000'
Time on Target: 07:13-08:07
Payload: 9095 lb.
Fuel Reserve: 1152 gal.

Mission 99
Date: 1945/4/26
Codename: Cockorow #1
Target: Kyushu Island: Saeki Airfield
Participating Unit: 73rd BW
A/C Launched: 23
Altitude: 20800' - 25390'
Time on Target: 07:53-08:18
Payload: 9095 lb.
Fuel Reserve: 1175 gal.

Mission 100
Date: 1945/4/26
Codename: Skewer #2
Target: Kyushu Island: Tomitaka Airfield
Participating Unit: 73rd BW
A/C Launched: 22
Altitude: 13000 - 24500'
Time on Target: 07:07-08:45
Payload: 9095 lb.

 

[Zipper730]

Have you got B-29 performance numbers to demonstrate the mileage vs altitude relationship? Unfortunately I have no data, at least for the B-29. But let's look at cruise performance of another turbocharged heavy bomber designed for sustained high altitude flight: the B-36. I chose a weight of 320,000 lb (about 80% of max useful load) as a representative outbound cruise condition. Power settings and speeds are selected for optimum fuel mileage at each altitude. The jet pods are not used.

0 ft, 190 mph EAS, 190 mph TAS, 35.0 nm/klb, 1800 hp
5000 ft, 186 mph EAS, 200 mph TAS, 35.5 nm/klb, 1870 hp
10000 ft, 185 mph EAS, 215 mph TAS, 36.0 nm/klb, 1980 hp
15000 ft, 178 mph EAS, 224 mph TAS, 35.5 nm/klb, 2050 hp
20000 ft, 175 mph EAS, 240 mph TAS, 31 nm/klb, 2200 hp
25000 ft, 175 mph EAS, 261 mph TAS, 26 nm/klb, 2400 hp

Best mileage ("nm/klb" = nautical miles per thousand pounds of fuel) is at 10,000 feet, though there's little difference from sea level to 15,000. But cruise at 20,000 and above causes a serious drop in fuel economy, though the power per engine is still acceptable for continuous operation. As you climb from sea level to 25,000 the best mileage airspeed does yield a steady increase in true airspeed, but the engines must be pushed harder too. Cruise at 30,000 with no jets is possible but not recommended since the best mileage speed is uncomfortably slow. It also requires 2500 hp/engine.

I'm confused about something here regarding air-miles per pound or air-miles per gallon.

These stats come from a thread about the most overrated aircraft of WWII and includes figures for the P-51D-5, P-38L, and the P-47D-25 at different altitudes and weights

P-51D-5, 9,600 to 8,000 lbs, wing bomb racks only, maximum range cruise condition​

At 15000 feet: 260 TAS, 44 GPH = 5.91 air miles per gallon​

At 20,000 feet: 280 TAS, 48 GPH = 5.83 air miles per gallon​

At 25,000 feet: 305 TAS, 52 GPH = 5.87 air miles per gallon​

​

P-38L, 17,400 to 13,500 lbs, tank supports only, maximum range cruise condition​

At 15000 feet: 229 TAS, 61 GPH = 3.75 air miles per gallon​

At 20,000 feet: 248 TAS, 66 GPH = 3.76 air miles per gallon​

At 25,000 feet: 267 TAS, 71 GPH = 3.76 air miles per gallon​

​

P-47D-25, 14,200 to 12,000 lbs, no external load, maximum range cruise condition (preliminary data)​

At 15000 feet: 266 TAS, 88 GPH = 3.02 air miles per gallon​

At 20,000 feet: 288 TAS, 95 GPH = 3.03 air miles per gallon​

At 25,000 feet: — no figures given —​

Why do the fighters show a performance benefit at high altitudes? Fuel burn is higher, but they also fly faster at higher altitudes and, on the fighters it evens out. It doesn't seem to be related to superchargers or turbocharges as the first only has a supercharger, and the latter two have turbochargers. My guess is it's got something to do with acceleration and time to climb.

 

[Shortround6]

. It doesn't seem to be related to superchargers or turbocharges as the first only has a supercharger, and the latter two have turbochargers.

First has a two stage mechanical supercharger and the other two have two stage superchargers, just that the first stage is powered by an exhaust turbine and not geared off the crankshaft.

Air is a lot thinner at higher altitudes so their is less drag. That is why modern jets cruise at high altitude and even why there are/were 4/6 seat private planes with turbos and pressurization. Increased range/cruise speed was thought to be worth the extra cost and maintenance.

 

[Zipper730]

Air is a lot thinner at higher altitudes so their is less drag. That is why modern jets cruise at high altitude and even why there are/were 4/6 seat private planes with turbos and pressurization. Increased range/cruise speed was thought to be worth the extra cost and maintenance.

What I was trying to get at was the B-29's sweet spot was fairly low whereas the P-47 & P-51 were high up.

The P-47 & B-29 used a mechanical supercharger & turbocharger; the P-51 used a twin-stage supercharger. Both the P-47 & P-51 showed improved miles per gallon when up at altitude whereas the B-29's sweet-spot was lower on down. I figured the reason had to do with the climb-rate.

 

[Shortround6]

. Both the P-47 & P-51 showed improved miles per gallon when up at altitude whereas the B-29's sweet-spot was lower on down. I figured the reason had to do with the climb-rate.

B-29 may have a sweet spot high up (mid 20,000ft range)
however that is different than max range/endurance. The much heavier B-29 could burn enormous amounts of fuel climbing to the high cruise altitude. Which the lower fuel consumption at the higher altitude did not make up for. The extra fuel was deducted from the bomb load. B-29s operated at some widely varying weights.
I believe the manual is available on this site.

 

[MIflyer]

Of possible interest:

B-29 Combat Crew Manual : Maj Gen Curtis E Le May : Free Download, Borrow, and Streaming : Internet Archive

Pilots' And Flight Engineers' Training Manual For The Superfortress B-29 : United States. Army Air Forces. Office of Flying Safety : Free Download, Borrow, and Streaming : Internet Archive

 

[Zipper730]

The much heavier B-29 could burn enormous amounts of fuel climbing to the high cruise altitude.

It would seem that they would climb to lower altitude, then climb up in steps.

 

[Joe Broady]

I'm confused about something here regarding air-miles per pound or air-miles per gallon.

P-38L, 17,400 to 13,500 lbs, tank supports only, maximum range cruise condition

At 15000 feet: 229 TAS, 61 GPH = 3.75 air miles per gallon​

At 20,000 feet: 248 TAS, 66 GPH = 3.76 air miles per gallon​

At 25,000 feet: 267 TAS, 71 GPH = 3.76 air miles per gallon​

​

Why do the fighters show a performance benefit at high altitudes? Fuel burn is higher, but they also fly faster at higher altitudes and, on the fighters it evens out. It doesn't seem to be related to superchargers or turbocharges as the first only has a supercharger, and the latter two have turbochargers. My guess is it's got something to do with acceleration and time to climb.​

​

(I omitted the P-47 and P-51 because I don't have detailed data at hand.)

No, the climb is not relevant because the figures are for the cruise condition, i.e., after the stated altitude has been attained. The B-36 figures for best range speed at various altitudes, which I posted earlier, show a similar effect of increased true airspeed with no range penalty as altitude increases — up to a point.

My theory is that the "point" occurs when the bomber must begin taking extra steps to keep its engines cool. The fighter doesn't reach that point because it doesn't have to push its engines so hard due to its more favorable power to weight ratio. My copy of the P-38 manual agrees with the values above, and also shows auto lean as the cruise mixture setting at all altitudes.

Compare that to the B-29 long range summary curve. Take a weight near the middle, say 110,000 lb. Find that weight on the bottom line and go straight up to the top set of curves. These give mileage (nm/gallon) at various altitudes. The solid lines are the auto rich mixture setting, the dotted lines are auto lean. At 110,000 lb there's a break in the 20,000 foot line, so you could use either mixture. But a descent to 15,000 greatly improves mileage, and 10,000 yields a further improvement.

The reason is evident in the next lower set of curves, which give estimated cowl flap settings. These show that best range speed at 110,000 lb and 20,000 ft requires 12 degrees open with auto lean, and 4 degrees with auto rich. The book says ("effect of cooling flaps") that a 6 degree opening reduces speed 10 mph. Clearly a 12 degree opening is unacceptable, so at 20,000 you're forced to cruise in auto rich. By descending to 15,000 you can use auto lean and 3 degrees of cowl flap. Go down further to 10,000 and the cowl flaps can be shut completely.

As altitude increases, so does the difficulty of cooling the engine. As the B-36 manual says, "The decreasing temperature is favorable as it widens the temperature difference of the heat exchange. Unfortunately the decreasing air density, which is unfavorable, reduces the weight of cooling air flow at a rate that overcomes the beneficial temperature factor. If constant power is maintained at high altitude, the cylinder cooling problem becomes increasingly difficult."

It's even worse because the higher you fly, the more horsepower is needed to obtain the airspeed for best range. That's clear in the B-29 miles per gallon curve. Thus, an increase in cruise altitude squeezes the flight engineer from two directions. Cooling is less effective and the demand for power is greater. With its great power a fighter is easy on its engine in cruise (P-38L: 1750 rpm and 27" Hg at 25,000) so these factors don't emerge.

 

[Zipper730]

This is pretty interesting as it shows the ingress altitudes (a lot lower than I would have thought) for the aircraft as well as the altitude over the target.

http://468thbombgroup.org/LinkClick.aspx?fileticket=zZmjz+XkwIc=&tabid=103&mid=548