Fighter Range-importance, philosophy, "records"?

[IdahoRenegade]

I'm curious about the range of various countries fighters during the war, both what they achieved, what the design philosophy was and what the longest range fighter missions were. Our (US) fighters (to the best of my knowledge) did not consider exceptionally long range as a design criteria pre-war. The "bomber mafia" insisted that heavy bombers could succeed without fighter escort and actually "banned" fighter designs from incorporating drop tanks. Yet our fighters ended up being among the longest range ones of the war (to the best of my knowledge).

Early in the war, from what I understand, the Zero probably had the longest range of any fighter. Which seems odd, given that due to it's limited power every effort was made to keep the plane very light. That seems to fly in the face of stuffing a lot of gas on board.

The '38 was designed as a fairly short range fighter (the term "interceptor" coined by Kelsey to get around "establishment" AAC limitations), but Kelsey started work with Johnson early on to equip it with plumbing and hardpoints for drop tanks and to design tanks for it. The 150-165 gallon tanks worked well and were ready by early-mid 42 on F4 (recon) variants, and were crucial for operation Bolero on all fighters. Later versions were fitted with twin 300-310 gallon tanks, as well as an additional 110 gallons in wing leading edge tanks (replacing the original intercoolers).

The '47 was not originally designed as a long range fighter, and had considerable growing pains, but finally in late versions ended up with exceptional range. Range extension was very much an afterthought, not a feature of the original design. IIRC they ended up using Lockheed tanks after several Republic attempts to develop their own.

The '51s range was always quite good, and excellent once fitted with the additional fuselage tank. Again though, the '51 was originally designed as a "super P-40" when contracted by the Brits, AFAIK range was not emphasized.

My understanding is that the Spit, BF-109 and FW-190 were all short-medium range fighters and never really did extend it to the extent that US ones did. Is that correct, and if so, why?

Also, what were the longest fighter missions of the war? I'm aware of the Borneo oil field missions that were somewhere around a 1200 mile radius (flown by '38s, and I've seen 1100-1300 mile radius claimed). Was this the longest fighter mission of the war? Anyone have any links to details on those missions (I've searched and found little).

Thanks all-love the forum and learning so much.

 

[tomo pauk]

Zero's long range was a result of decent fuel tankage feeding the engine of modest power, hence of modest consumption. Modest engine power has it's shortcomings, especially looking with 'Western' eyes, where people wanted, all it the same time, much more speed, protection, firepower, ammo count.
The Japanese have had a fighter with even longer range, speed, some protection - Ki-61.

The P-38 was not designed as a short range fighter - 400 gals were to feed two 1150 HP engines, or about twice the fuel per engine as carried by Hurricane, Spitfire or Bf 109; granted, it was designed as an interceptor.
Once the self sealing tanks were incorporated, the remedy for the fuel capacity now lost was installation of drop tanks. Granted, big 'fuel fraction' on the US fighters was a function of geography, rather than of non-existing doctrine of fighters escorting bombers; the XP-39 (another interceptor) was with 200 gals, the P-39C was with 170 gals, similar was the P-36 and early P-40. Here also the drop tank was a mean to restore fuel capacity once the self sealing tanks reduced internal fuel tankage.

Too bad the people at Republic were trying to reinvent the wheel, instead of going on with pylons from P-38 that were far less a bulky/draggy item.

 

[Shortround6]

The P-38 was a "long range" fighter from it's early conception. It is just that the definition "long range" varied with time and the power of the available engines. The P-38 was designed to a specification that called for the same speed and climb and same armament as the initial specification for the P-39 except twice the endurance. The Allison was only offering about 1000hp when the initial design work for the P-39 and P-38 was going on.
US fighters were designed ( and ALL US wartime fighters were in design stage well before Pearl Harbor) for much greater range than European fighters simply because of the size of the United States. Modern Germany is about 85% of the size of California for example. The US needed to be able to transfer fighters quickly from east to west or north to south and nominal ranges of 600-800 miles make that a lot easier than ranges of 350-450 miles like most European fighters of the mid/late 30s.
US fighters were designed to hold a lot more fuel than European fighters (160-200 US gallons for single engine fighters before the P-47) but self sealing fuel tanks cut into the fuel capacity to a greater or lesser extent depending on the shape/layout of the tanks which necessitated the initial round of "drop" tanks to restore range/endurance. Once the tanks were in the supply chain it was a matter of expanding the supply and fitting the aircraft with fittings for the planes that didn't have them initially and adding additional tank stations to the planes that started with one station (belly tank). Larger tanks were designed and put into production.
Please note that many US planes (like European aircraft) had major increases in power from prototypes/ early models to later ones allowing a much greater fuel load to be carried (take-off). While more powerful engines require more fuel it is only while using the extra power, in long range cruise the engine only needs to make enough more power to handle the extra weight/drag of the external tanks.

P-47 had twice the "nominal" range of either a Spitfire or Bf 109, none of them using external tanks. Nominal range being figured at around 200mph cruise, low altitude and allowing for take-off. Trouble is you can't fly at 200mph at low altitude (5,000ft) over enemy territory so the P-47 didn't have the range to perform the mission/s required when it did show up in combat, about 2 1/2 years after design work started.

For long range work drop tanks don't provide the entire answer. They are great for getting a plane to the target. Not so good for getting the plane home. Strapping 300 gallons to the outside of a 100 gallon (inside) fighter may give you almost 4 times the "nominal range" but if you have to drop all the external fuel and run the engine at combat/full power for 15-20 minutes after dropping the tanks you only have whatever fuel is left in the internal tank/s to get home and that is waaaay less than 100 gallons.
Planes have to be designed from the start to hold large amounts of internal fuel (or it helps a great deal). The P-36 was designed to have an over 50 gal tank behind the pilot for ferry purposes. Combat was to done on the tanks in the wing center section. When modified into the P-40 the behind the seat tank became a normal tank and one of the wing tanks became the overload tank (weights/balance and center of gravity). Sticking a 55 gallon drum (or equivalent--- 10-11 jerry cans?) into an existing fighter is not going to be easy in all cases.

 

[pbehn]

I dont know that the 109 was designed as an interceptor, I thought it was designed as a fighter to protect and screen bombers and dive bombers who in turn were supporting the army. The Spitfire and Hurricane were definitely interceptor fighters, the additional range that the P51 had with its bigger internal tanks may have been useful in some situations but being scrambled to an incoming raid in the BoB it would be dead weight to carry up to altitude, making height fast was frequently the most important part of the planes performance.

One thing to note is how national attitudes affect what is perceived as "good range". France is only 21 miles from England. In England it is impossible to be more than 72 miles from the sea. London is about 70 miles from Dover and about 320 from Scotland. Compare to distances to fly around the USA and Canada and the distances ships are apart from each other and a port when at sea.

 

[tomo pauk]

The Bf 109 was not conceived to provide escort for 'level bombers', those being majority in Luftwaffe. He 111 and Do 17 were to 'always get through' in very much the same fasion that was the thing in RAF or USAAC. Even the Bf 110 was not 'just' the escort fighter, it's roles being also to contest enemy fighters over thier bases, and to intercept & destroy enemy bombers.
The early effort to have 2 cannons on the Bf 109 (even with Jumo 210 on board) and 110 tend to show what was intended target for those two.

Radar-assisted air defence quickly rendered both unescorted bombers and slowish hevy fighters obsolete.

 

[stona]

The Bf 109 was based on the RLM's 'Tactical Requirements for Fighter Aircraft (Land)' of 1933 which called for 1 1/2 hours full throttle flight at 6,000m. Make of that what you will.

France might be only 21 miles from Britain, but that would not have concerned the British in the 20th Century. The 250-300 miles from East Anglia to the Ruhr valley, or Germany's western airfields to London were more relevant, but not to fighter design.

Cheers

Steve

 

[Shortround6]

pbehn males some good points. Lets also remember that the 109 was designed around a 600-700hp engine which rather limits the size/weight of the fighter while still keeping good performance. The 109 was designed to the short range specification, the 110 covering the long range specification. Please note that 1-2 years could pass between issue of a specification (requirement/invitation to tender, etc)
and first flight of a prototype let alone introduction into service so doctrine/tactics/actual requirements could change.
The 109 was designed as a replacement for the Heinkel He 51 and Arado Ar 64 biplanes.
And this was the standard Luftwaffe bomber of the Mid 30s.

Most other countries not having anything much better in any numbers in the mid 30s.

Not a lot of need for long range fighters when the bombers weren't very long range. Combat experience in Spain with the early He 111 and Do 17s suggested (wrongly) that escort fighters weren't needed. Japan's combat experience over China suggested otherwise but most western nations weren't given the results of Japanese experience or ignored it.

 

[pbehn]

The Bf 109 was based on the RLM's 'Tactical Requirements for Fighter Aircraft (Land)' of 1933 which called for 1 1/2 hours full throttle flight at 6,000m. Make of that what you will.

France might be only 21 miles from Britain, but that would not have concerned the British in the 20th Century. The 250-300 miles from East Anglia to the Ruhr valley, or Germany's western airfields to London were more relevant, but not to fighter design.

I agree steve
I was thinking more of a comparison to the USA Japan and Germany with their potential adversaries, in the Pas de Calais the LW took off and formed up in sight of British Radar, it changes the mind set of what is "good range" imagine trying to protect the USA eastern seaboard and northern lines of approach with planes of a Spitfires range.

 

[IdahoRenegade]

The P-38 was a "long range" fighter from it's early conception. It is just that the definition "long range" varied with time and the power of the available engines. The P-38 was designed to a specification that called for the same speed and climb and same armament as the initial specification for the P-39 except twice the endurance. The Allison was only offering about 1000hp when the initial design work for the P-39 and P-38 was going on.
US fighters were designed ( and ALL US wartime fighters were in design stage well before Pearl Harbor) for much greater range than European fighters simply because of the size of the United States. Modern Germany is about 85% of the size of California for example. The US needed to be able to transfer fighters quickly from east to west or north to south and nominal ranges of 600-800 miles make that a lot easier than ranges of 350-450 miles like most European fighters of the mid/late 30s.
US fighters were designed to hold a lot more fuel than European fighters (160-200 US gallons for single engine fighters before the P-47) but self sealing fuel tanks cut into the fuel capacity to a greater or lesser extent depending on the shape/layout of the tanks which necessitated the initial round of "drop" tanks to restore range/endurance. Once the tanks were in the supply chain it was a matter of expanding the supply and fitting the aircraft with fittings for the planes that didn't have them initially and adding additional tank stations to the planes that started with one station (belly tank). Larger tanks were designed and put into production.
Please note that many US planes (like European aircraft) had major increases in power from prototypes/ early models to later ones allowing a much greater fuel load to be carried (take-off). While more powerful engines require more fuel it is only while using the extra power, in long range cruise the engine only needs to make enough more power to handle the extra weight/drag of the external tanks.

P-47 had twice the "nominal" range of either a Spitfire or Bf 109, none of them using external tanks. Nominal range being figured at around 200mph cruise, low altitude and allowing for take-off. Trouble is you can't fly at 200mph at low altitude (5,000ft) over enemy territory so the P-47 didn't have the range to perform the mission/s required when it did show up in combat, about 2 1/2 years after design work started.

For long range work drop tanks don't provide the entire answer. They are great for getting a plane to the target. Not so good for getting the plane home. Strapping 300 gallons to the outside of a 100 gallon (inside) fighter may give you almost 4 times the "nominal range" but if you have to drop all the external fuel and run the engine at combat/full power for 15-20 minutes after dropping the tanks you only have whatever fuel is left in the internal tank/s to get home and that is waaaay less than 100 gallons.
Planes have to be designed from the start to hold large amounts of internal fuel (or it helps a great deal). The P-36 was designed to have an over 50 gal tank behind the pilot for ferry purposes. Combat was to done on the tanks in the wing center section. When modified into the P-40 the behind the seat tank became a normal tank and one of the wing tanks became the overload tank (weights/balance and center of gravity). Sticking a 55 gallon drum (or equivalent--- 10-11 jerry cans?) into an existing fighter is not going to be easy in all cases.

You took the time to word that much better than I did. Ben Kelsey's 1937 request for proposal specified "fuel for 1 hour at rated power" I believe, or ~400 miles of range. Certainly good for that timeframe but far from what was achieved just a few short years later. What I guess impresses me is how quickly they extended the range dramatically. '38s were flying with large drop tanks by early '42 and were used to fly to Britain from the US on Operation Bolero, with several long range legs. The rapid deployment from Britain to North Africa in late '42 was about 1500 miles unrefueled-I don't think any other fighter (possibly excepting the Zero) was capable of that, at that time. In late '42 a P-38F, in the hands of a test pilot, flew 2900+ miles. Remember that versions at that time (an F IIRC) did not have wing leading edge fuel tanks.

 

[Shortround6]

It is no great trick to extend range to long distances IF you allow the planes to fly in overloaded condition, restrict maneuvers until fuel is burned off, and have very, very long runways to take-off from.

Lockheed had done studies (and converted planes) in the mid/late 30s on the Lockheed Electra 10 airliner. In airline use and carrying 8-10 passengers this plane (twin 450-550hp engines) had a range of 600-800 miles on 150-200 gallons of gas. For flying the Atlantic (or for use by Amelia Earhart) they ripped out the seats and stuffed large fuel tanks in the cabin. This allowed for flights as long as 4000 miles at optimum altitudes and speeds.
The last is important as one of the range charts in this study shows the optimum cruise altitude for the first 1000 miles to be 1000ft or under (yes one thousand) until fuel is burned off. At a "normal" gross weight of 10,000-10,500lbs the Electra had a single engine ceiling of 4000-6000ft depending on engines fitted. Take off for record setting flights was allowed at over 14,000lbs. engine failure in the first few hundred miles at that high weight would mean the plane could not maintain height on the remaining engine.

Some of these fighter long range flights were done under similar conditions/circumstances. They were done/allowed despite the risk for certain military reasons. Operation Bolero was done, in part, for rapid deployment (although the ground personnel traveled by ship) and to save on shipping space. Most P-38s used in Europe, North Africa and Italy were sent over as deck cargo after the first few hundred planes. This despite Bolero having a loss rate about 1/2 that first anticipated.

 

[drgondog]

Remember two things about the P-38/range discussion. First, you can shut down an engine and feather it so that you can run at lowest fuel consumption rate. Second, the P-38 was much like the F4U and F6F in that at most economic cruise setting it cruised at a pretty low speed in comparison with a P-51/P-47.

Despite the very long potential range, the actual combat radius (defined by take off, climb, cruise, combat, cruise home and have 20 minutes reserve of fuel) was less than the P-51B/D. The other issue for the P-38 in the ETO is that its best cruise speed was about 40-50mph TAS slower than the P-51 at 25,000 feet - with a double hazard. If attacked it took longer to react at combat speed, and second - the pilot had to be very careful raising RPM and boost with the turbosupercharger and intercooler (Pre-J) configuration.

 

[pbehn]

Great posts SR and Drgodog, I guess what you are saying is "its complicated".

 

[eagledad]

Gentlemen

I was surprised to see that the P-51 and P-47 cruised 40 /50 mph faster than the P-38 so I dug up some data. This data is taken from Tactical Planning; Report No TSEAL-6-AI dated September 1945:

Data is for 25,000 feet







Max Cruise Power





Max Continuous Power


Weight

Fuel

Range

Time

Speed



Range

Time

Speed


Pounds

Gallons

Miles

Hours

Calculated

Miles

Hours

Calculated

P-51D11600​

489

2100

6.1

344.2623​

1950

5.4

361.1111​

P-47D

16700

670

960

3.4

282.3529​

820

2.4

341.6667​

P-38J

20200

740

1460

4.9

297.9592​

900

2.8

321.4286​

Clean Aircraft at max Continuous power (25,000 feet)

P-51D 406
P-47D 372
P-38J 374


Note, as Drgondog stated, the P-51D is 40 to 50 mph faster at these settings. Depending on conditions, the P-47D is either faster or slower.

The P-51D figures include 2-110 gallon drop tanks, The P-47 includes 2-150 gallon drop tanks and the P-38J includes 2-165 gallon drop tanks.

I thought I might add more data to the discussion.

Eagledad

 

[eagledad]

Please delete previous post
Eagledad

 

[eagledad]

Gentlemen

I was surprised to see that the P-51 and P-47 cruised 40 /50 mph faster than the P-38 so I dug up some data. This data is taken from Tactical Planning; Report No TSEAL-6-AI dated September 1945:

Data is for 25,000 feet
Max Cruise Power Max Continious Power
Name Weight Fuel Range Time Speed Range Time Speed
Pounds Gallon Miles Hour Mph Miles Hour Mph
P-51D 11,600 489 2,100 6.1 344.2 1,950 5.4 361.1
P-47D 16,700 670 960 3.4 282.4 820 2.4 341.7
P-38J 20,200 740 1,460 4.9 298.0 900 2.8 321.4


Clean Aircraft at max Continuous power (25,000 feet)

P-51D 406
P-47D 372
P-38J 374


Note, as Drgndog stated, the P-51D is 40 to 50 mph faster at these settings. Depending on conditions, the P-47D is either faster or slower.

The P-51D figures include 2 110 gallon drop tanks, The P-47 includes 2 150 gallon drop tanks and the P-38J includes 2 165 gallon drop tanks.

I thought I might add more data to the discussion.

Eagledad

 

[GregP]

While technically correct, and while you COULD cruise that fast (TAS) for a purely fighter mission, you couldn't for an escort mission, which was far and away the most common mission for a the P-51. And the P-47s almost NEVER cruised that fast with bombs ... maybe on the way home when they were clean. The P-38s usually had drop tanks on and typically cruised into a combat area at 290 - 330 mph. Again, that is according to former pilots. If they didn't have to stay with slow bombers, they were free to go faster and no doubt did, particularly as the war wound down (late 44 onward) and the mission distances got shorter.

The bombers were cruising at 185 - 200 mph or so IAS (call it CAS), so they were making a TAS of about 278 - 300 mph. No escorts would run around at max continuous power 100 mph or so faster than the planes they were escorting. According to the many pilots giving talks at the Planes of Fame, they typically cruised about 30 - 40 mph faster than their bombers and weaved around above or below them, and cleaned the plugs at higher power settings for 10 minutes or so every hour.

I have little doubt that there were some fast P-51s flitting about on fighter sweeps, but not many when there were 700 P-51s escorting 1,000 bombers.

In the past, we had some heated debates about this and there is no point repeating them here. Suffice to say the "fast" numbers are all TAS, not IAS, and were mostly confined to non-escort types of action. An escorting P-51 could easily get to well over 400 mph if he followed a Bf 109 / Fw 190 down through a formation, but if he did, we was essentially abandoning his mission, even if just for a short while. And while he was gone, the bombers were open to more successful attacks. I don't claim it didn't happen, but most of the fighters stayed around the bombers for the duration of their escort mission. They were free to indulge themselves on the way home if they were cleared home at some point by the mission planning.

NOT escorting, I bet many transited combat areas rather fast, probably up at max continuous power, right where you are talking above. Things are always easier if you aren't confined to a particular set of actions.

 

[tomo pauk]

The max speed of B-17G was ~320 mph, it cruised at ~200 mph, all values are TAS - true air speed. Please see here.
The escorts were indeed required to cruise at 210 mph indicated at 25000 ft, gives a bit more than 300 mph true. The difference in speeds meant that close escorts were ess-ing, in order not to get too far away from bombers.

 

[pbehn]

The max speed of B-17G was ~320 mph, it cruised at ~200 mph, all values are TAS - true air speed. Please see here.
The escorts were indeed required to cruise at 210 mph indicated at 25000 ft, gives a bit more than 300 mph true. The difference in speeds meant that close escorts were ess-ing, in order not to get too far away from bombers.

Surely that is impossible to say apart from in a test, cruising speed depends on head winds, bomb load and the speed of the slowest.

 

[eagledad]

Gentlemen


No argument with what you both say.

From same source

B-17G max cruise power with 4000lbs of bombs, 25,000 feet: 1,850 miles, 8.7 hours, ave speed 212.6
max continuous same load and altitude as above 1,450 miles, 6.2 hours, ave speed 233.9
B-24H max cruise power with 5000lbs of bombs, 25,000 feet 1,700 miles 7.3 hours, ave speed 232.9
max continuous same load and altitude as above 950 miles 3.5 hours ave speed 271.4

As stated no allowance made for head or tail winds. Also note fort he B-17 to obtain the ranges given, the first 4 hours are spent at 20000 feet for max cruise and 3 hours for max continuous ranges.

Eagledad

 

[GregP]

Hi Tomo,

I was trying to not start the same old debate all over again and was mostly making the point that the speed of a fighter at any particular time in a mission was pretty dependent on the mission. Escort had a different requirement than a fighter sweep. I figured someone would come in and clear it up. I get the feeling that as the war wound down, there were more fighters on missions that were not escort, and they were free to use their own speeds and tactics. That being the case, they probably DID go considerably faster that when on escort duty.

Cruising into the war zone: