Did the RAF have designs for a long range escort fighter?

[stona]

Neither the P-47 nor P-51 had enough range to accompany USAAF bombers all the way to their targets. An unbelievably complicated relay system was used. It got a bit simpler after they were belatedly fitted with drop tanks.
You could argue that the US didn't really produce a long ranged single seat fighter in time for the initial stages of the daylight bombing campaign.

As you say the USAAF too thought that the bomber would always get through when it became involved,even in the face of the evidence from the British and Germans who had already been at it for several years.

Naval aircraft are something entirely different. The US has and had important strategic objectives in the Pacific and that's an awfully big bit of water.

Cheers

Steve

 

[Shortround6]

I already spoke of the Tempest adequated range. Was it unsuitable to high altitude combat?

It is three things. One was that the high altitude performance was a bit lacking.
The second is that Drop tanks can get you into trouble. Combat radius is distance you can make it back from AFTER you drop the tanks, engage in a high speed fight for 15-20 minutes (5 minutes at WEP or Combat rating and the rest at Military power), while allowing for reserves in case of bad weather/head winds to find the home Field. Take-off and initial climb out was done on internal tanks in-case of a problem with the drop tanks so internal tanks werenever 100% full when the external tanks were dropped. If the Drop tanks are too big (ferry tanks) you can get in further than you can get out.
Third is that MAX range with tanks was almost always for some altitude and speed that was useless for escorting bombers.
Like this :

http://www.wwiiaircraftperformance.org/typhoon/typhoon-ads.jpg

254mph at 15,000ft is useless for escorting bombers, you need to be at 22,000-30,000ft and moving faster in order to be able to respond. Escort fighters flew a weaving pattern so their forward speed over ground some what matched the bombers but that added to actual miles flown and shortened the operational radius.

 

[Shortround6]

As a slightly different question, how come the Americans produced long range fighters?

We've established that the belief existed among all the nations, including the Americans, that the bomber will always get through so why did they see the need for these longer ranged fighters? Or was it just pure chance that they were adaptable to taking more fuel?

For one thing the US is big

P-36 and early P-40s carried 25-40% more fuel than the Spitfire, Hurricane, 109. They needed just to deploy around the US.
The P-38 was supposed to be a long range (or high endurance?) interceptor. Again, given the size of the United States the need to have fighter fields a few hundred miles apart for thousands of miles of coast line was seen as cost prohibitive. Better to have somewhat fewer fields (and fighters) that could cover a wider area.

And part of it was chance.

The fact that the two stage Merlin in the P-51B-D was several hundred pounds heavier and needed a heavier propeller than the plane was originally designed for may have made the installation and flight with the rear fuselage tank a lot easier than it would have been if the Allison had stayed.

 

[tomo pauk]

The 2 stage R-2800 had 1800hp at 15,500ft but that is in low gear, in high gear it had 1650 at 22,500ft. While the dry weight of the engines was about the same the R-2800 doesn't have around 600+ pounds of radiators/coolant. Of course it is fatter with more frontal area/drag.

The 'engine accesories' (auxiliary supercharger and intercoolers?) weight 300+ lbs in F6F, that item was missing from the single stage Vulture. The weight of cooling system depends much of the execution, the 350 lbs cooling system of the P-36 was able to cool the engine developing 90% of Vulture's power.

Once Merlin XX series engines are allowed over 9lb boost it doesn't look so good for the Vulture. Granted it was several years after the Vulture's Heyday but 1480hp at 12,500 for 1000lbs lessof dry engine weight + much smaller radiators and propeller doesn't make the Vulture look good.

At 15000 ft that would be 1300 HP for the Merlin XX? If Vulture's power does not look good, how good is Sabre then?

We are talking in the context of an escort fighter which means while the plane doesn't HAVE to be as good as the short range defender it should be close. 10% worse in both speed and climb won't cut it.

What planes are in the comparison?

While altitudes did not go up as expected after the BoB the escort fighters do need to keep the defenders from getting positions 3-8,000ft above the bomber formations and diving down through them. The escort fighters WILL have to fight, at least somewhat at 25,000-30,000ft.

Service ceiling for Typhoon was 33-34000 ft, for Tempest V (the one with same engine, Sabre IIA) was 35-36000 ft, depending on load. The wing area of Tempest was some 10% greater than Typhoon's.

added: the Vulture we're discussing should be Vulture II, capable for 1710 HP at 15000 ft. That would be unrestricted variant, used at Avro Machester, at least according to the ADS Neil Stirling kindly posted. Date of ADS being 14 Aug 1941. The 'fighter' variant was the Vulture V (better performance at altitude? wuzak, help with these Vultures!)

 

[buffnut453]

As a slightly different question, how come the Americans produced long range fighters?

We've established that the belief existed among all the nations, including the Americans, that the bomber will always get through so why did they see the need for these longer ranged fighters? Or was it just pure chance that they were adaptable to taking more fuel?

'Cos Americans want their aeroplanes to be like their cars (and their women?)...bigger than everyone else's. I think it's a compensation thing.

Seriously, though...another poster hit the nail on the head - the US is a big place and to enable air mobility, you have to build aircraft that can fly a long way. The happy coincidence is that, by late-1941, engine technology was providing the kind of performance, both in terms of outright thrust potential and fuel efficiency, to give these larger airframes unprecedented combat performance at long range.

I think a similar happy coincidence, and for exactly the same reasons, revolves around the increasing use of fighters in the ground attack role from 1942 onwards - we see fewer and fewer dedicated light-bomber aircraft and more fighters being used for mud-moving.

 

[Shortround6]

The 'engine accesories' (auxiliary supercharger and intercoolers?) weight 300+ lbs in F6F, that item was missing from the single stage Vulture. The weight of cooling system depends much of the execution, the 350 lbs cooling system of the P-36 was able to cool the engine developing 90% of Vulture's power.

The weight of the auxiliary supercharger is included in the 2480lbs of the R-2800 two stage, the Single stage weighed 2360lb but you are right about the inter-coolers. What cooling system in a P-36?
If you meant P-63 then you have to include the water injection system (50lbs) plus the weight of the fluid (186lbs for 25 gallons).

At 15000 ft that would be 1300 HP for the Merlin XX? If Vulture's power does not look good, how good is Sabre then?

Not good for an escort fighter. And depends on the Sabre, IIA were running at 3700rpm and 9lbs boost while IIBs were running 3850rpm and 11lb boost. IIA was 1830 at 11,500ft while the IIB was 2050 at 13,750 but the II B was a little late in the game.
What would a production Sabre have been good for in 1942/43 as an escort fighter and a critical altitude of under 12,000ft doesn't look good.

What planes are in the comparison?

What ones do you want? It was a hypothetical. If the 109 can do 400mph trying to use an escort fighter than can only do 360-370 isn't going to be real successful, especially if the 109 can out climb it. The escort fighter HAS to be able to equal the defender at something ( or come within a couple of percent, 10% is way to much) even if not so good at something else.

Service ceiling for Typhoon was 33-34000 ft, for Tempest V (the one with same engine, Sabre IIA) was 35-36000 ft, depending on load. The wing area of Tempest was some 10% greater than Typhoon's.

The service ceilings are too low. Nobody is fighting at 34-36,000 but those are the altitudes the plane can fly pretty much straight and level and if really lucky, with one other airplane.

In a book from the R-R Heritage trust there is a chart for the 109E, Hurricane I, Hurricane II and Spitfire I. with a few performance figures at high altitudes. It is this kind of thinking that shaped western combat.


AIrcraft...............service ceiling............oper.ceiling........time to op ceiling......rate of climb/30,000ft.......time to 30,0000ft...........rate of climb 25,000ft.............time to 25,000ft

Bf109E...................35,200ft.....................31,900ft............20min, 23sec..............740fpm........................17min, 12 sec.................1340fpm.............................11min, 39sec
Hurricane I..............35,000ft.....................31,400ft............21min, 15 sec.............660fpm........................17min, 30 sec.................1260fpm.............................13min, 12sec
Hurricane II.............37,600ft.....................34,900ft............19min, 57sec.............1160fpm........................13min, 20sec..................1840fpm............................. 9min, 48 sec
Spitfire I.................37,400ft.....................34,000ft............21min, 33sec.............1020fpm........................15min, 42sec..................1660fpm.............................11min, 33 sec.

Operational ceiling is where they can climb at 500fpm. (and is about what a good 40hp piper cub can do at sea level) and is what is need for a margin of power to maintain small formations. Please note that while the Hurricane I and II are only about 2600ft apart in 'service ceiling' the actual capabilities of the two planes are much further apart. At 25,000ft the MK II is climbing about 3 ft for every 2ft the MK I does. and at 30,000ft it can climb 75% faster.

Test conditions are not really given but I hope this brings out the point about "service ceilings" It is a nice comparison but in actual fact the planes were fighting 3-6,000ft below their service ceilings in order to be effective. It may also bring home why the P-40 with a service ceiling of 29,000ft or so was judged to be pretty much out of the running for the European theater.

 

[Shortround6]

I think a similar happy coincidence, and for exactly the same reasons, revolves around the increasing use of fighters in the ground attack role from 1942 onwards - we see fewer and fewer dedicated light-bomber aircraft and more fighters being used for mud-moving.

Kind of, In the 1930s with 600-900hp engines if you wanted to lift 1000lb of bombs and fly past the next county (not country) you were going to need a big wing to get off the ground. With 1200-1500hp engines the small wing fighters could do the job (and constant speed props) and with 2000hp engines the fighters could carry 1000lb of bombs a fair distance or more bombs a short distance. Longer runway helped too.

 

[tomo pauk]

The weight of the auxiliary supercharger is included in the 2480lbs of the R-2800 two stage, the Single stage weighed 2360lb but you are right about the inter-coolers.

Okay.

What cooling system in a P-36?
If you meant P-63 then you have to include the water injection system (50lbs) plus the weight of the fluid (186lbs for 25 gallons).

P-36?? P-63, indeed.
Why should we include the ADI system into cooling system, pound-per-pound?

Not good for an escort fighter. And depends on the Sabre, IIA were running at 3700rpm and 9lbs boost while IIBs were running 3850rpm and 11lb boost. IIA was 1830 at 11,500ft while the IIB was 2050 at 13,750 but the II B was a little late in the game.
What would a production Sabre have been good for in 1942/43 as an escort fighter and a critical altitude of under 12,000ft doesn't look good.

If one saddles the Sabre with thick wing, that has also the wing area just a tad greater than Spitfire, sure enough the performance will suffer, especially the performance at altitude. Back to the other 24 cyl, the Vulture II, bomber engine, was providing some 10% more HP above 15000 ft.

What ones do you want? It was a hypothetical. If the 109 can do 400mph trying to use an escort fighter than can only do 360-370 isn't going to be real successful, especially if the 109 can out climb it. The escort fighter HAS to be able to equal the defender at something ( or come within a couple of percent, 10% is way to much) even if not so good at something else.

109 was able to outclimb the P-47 and P-51, not that it gave it much edge in fight over Germany. The escorts were already at altitude, they did not needed the climb rate as badly as defenders.
The 360-370 mph is value for Typhoon at 26000 ft, the airplane twice cursed by wing choice. The Sabre-engined fighter with thinner wing (say, 15% instead of 19%) and tad a greater area (300 sq ft vs. 275) should offer 400 mph at 27000 ft. The Tempest's superb wing was enabling 405-425 mph, at Sabre IIA power (9 lbs, 3700 rpm), at 28000 ft.

The service ceilings are too low. Nobody is fighting at 34-36,000 but those are the altitudes the plane can fly pretty much straight and level and if really lucky, with one other airplane.

Agreed. They should be flying between 25-30000 ft.

In a book from the R-R Heritage trust there is a chart for the 109E, Hurricane I, Hurricane II and Spitfire I. with a few performance figures at high altitudes. It is this kind of thinking that shaped western combat.


AIrcraft...............service ceiling............oper.ceiling........time to op ceiling......rate of climb/30,000ft.......time to 30,0000ft...........rate of climb 25,000ft.............time to 25,000ft

Bf109E...................35,200ft.....................31,900ft............20min, 23sec..............740fpm........................17min, 12 sec.................1340fpm.............................11min, 39sec
Hurricane I..............35,000ft.....................31,400ft............21min, 15 sec.............660fpm........................17min, 30 sec.................1260fpm.............................13min, 12sec
Hurricane II.............37,600ft.....................34,900ft............19min, 57sec.............1160fpm........................13min, 20sec..................1840fpm............................. 9min, 48 sec
Spitfire I.................37,400ft.....................34,000ft............21min, 33sec.............1020fpm........................15min, 42sec..................1660fpm.............................11min, 33 sec.

Operational ceiling is where they can climb at 500fpm. (and is about what a good 40hp piper cub can do at sea level) and is what is need for a margin of power to maintain small formations. Please note that while the Hurricane I and II are only about 2600ft apart in 'service ceiling' the actual capabilities of the two planes are much further apart. At 25,000ft the MK II is climbing about 3 ft for every 2ft the MK I does. and at 30,000ft it can climb 75% faster.

Test conditions are not really given but I hope this brings out the point about "service ceilings" It is a nice comparison but in actual fact the planes were fighting 3-6,000ft below their service ceilings in order to be effective.

Thanks for the effort to type out the data

It may also bring home why the P-40 with a service ceiling of 29,000ft or so was judged to be pretty much out of the running for the European theater.

It was also darn slow, compared with contemporary Spit, 109 and 190.

 

[Balljoint]

Hi Balljoint.



I don't doubt AAF requirements were taken into consideration in designing the Mustang; it was, after all an American design by an American team. It's only natural that NA would want the USAAF to operate the type. As for a Mustang (P-51 was a USAAF designation and not officially used by the British) model built to RAF standards, which model Mustang was that?

Later Mustangs were certainly modified for RAF requirements, such as radio fit and in later Mustang IIIs (equivalent to the P-51C) a 'bubble' hood instead of the earlier bird cage one, but I don't recall a specific late model Mustang built especially for the RAF. The Mustang was actually designed for service with the RAF to begin with, as the RAF was its first customer. Experimental Mustangs were modified by Rolls Royce as test beds for the Merlin, but they were research aircraft only and were not meant for service use. Packard did the design work on the nose to take the Merlin installation.

I had to think on this a bit. The P-51-H (almost saw combat) was a redesign by NA to RAF stress specs but for the AAF. Timmy had posted on this in another thread.

 

[Shortround6]

Why should we include the ADI system into cooling system, pound-per-pound?

Maybe because if you DON'T use the ADI system you DON'T get 90% of the power of the Vulture? You get 1500hp or under. Put it were you want, it has to go into the power plant weight somewhere.

109 was able to outclimb the P-47 and P-51, not that it gave it much edge in fight over Germany. The escorts were already at altitude, they did not needed the climb rate as badly as defenders.
The 360-370 mph is value for Typhoon at 26000 ft, the airplane twice cursed by wing choice. The Sabre-engined fighter with thinner wing (say, 15% instead of 19%) and tad a greater area (300 sq ft vs. 275) should offer 400 mph at 27000 ft. The Tempest's superb wing was enabling 405-425 mph, at Sabre IIA power (9 lbs, 3700 rpm), at 28000 ft.

The Climb rate has to do with the ability to perform sustained speed turn. It is not one for one but in general the plane with the better climb rate has more surplus energy and can use it for climb or to counter act drag in a turn. A poor climbing plane has little extra power and has a choice of doing wide turns and maintaining altitude or doing a tight turn and trading altitude for speed. Go to the the two Hurricanes in the example. If both are at a high altitude (over 25,000ft) and turning at speed XXX ( Hurricane I is pulling just enough G that it is at full throttle but is neither gaining or loosing speed or gaining or loosing altitude) the Hurricane II has several choices, it can turn at the same speed/radius (G Load) and gain altitude( to be traded later?) or it can pull a tighter radius at the same speed without loosing altitude or it can turn at the same radius but at a higher speed than the MK I without loosing altitude. If the two planes were fighting each other you can see the advantages the better climbing plane has in addition to regaining altitude after a firing pass. Granted both can pull really tight turns and trade several thousands of feet of altitude for a tight turning radius.
Given a decent radar system the Germans shouldn't have needed fast climbing aircraft to get into firing position. For fighters based in Germany they should have over an hours warning that a raid is coming, granted they don't know WHERE but??? knocking 2-3 minutes of the time to 30,000ft doesn't do much for the intercept. Having a fast climbing fighter may help to evade escort fighters or in the absence of fighters help the interceptors to do multiple firing passes.

It was also darn slow, compared with contemporary Spit, 109 and 190.

Not in 1940, the first Tomahawk reached England in Sept of 1940. It was certainly faster than a Hurricane, even a MK II.

 

[buffnut453]

Kind of, In the 1930s with 600-900hp engines if you wanted to lift 1000lb of bombs and fly past the next county (not country) you were going to need a big wing to get off the ground. With 1200-1500hp engines the small wing fighters could do the job (and constant speed props) and with 2000hp engines the fighters could carry 1000lb of bombs a fair distance or more bombs a short distance. Longer runway helped too.

Agreed, kindda. You have to have a structure strong enough to carry the external stores. The Spit, Me109 and P-36/P-40 never really were strong enough, hence they mostly carried bombs on the centreline and hence couldn't really match the weapon load of a light bomber. Larger, stronger airframes, like the P-47, P-51, Tempest, Sea Fury etc could carry heavier external ordnance loads that were comparable to a light bomber (eg the latter 2 could each carry 2000lb in bombs operationally).

 

[Shortround6]

I don't know how many they broke doing this but;

 

[buffnut453]

Looks like it's had a few too many - distinct list to port...or is that me?

 

[tomo pauk]

Maybe because if you DON'T use the ADI system you DON'T get 90% of the power of the Vulture? You get 1500hp or under. Put it were you want, it has to go into the power plant weight somewhere.

I was talking about the systems that R-2800 had, and the Vulture had not, and vice versa. The P-63 served as an example that a 350 lb cooling system was able to cool the engine developing 1800 HP, so the Vulture's cooling system does need to go to 600+ lbs for 2000 HP.

The Climb rate has to do with the ability to perform sustained speed turn. It is not one for one but in general the plane with the better climb rate has more surplus energy and can use it for climb or to counter act drag in a turn. A poor climbing plane has little extra power and has a choice of doing wide turns and maintaining altitude or doing a tight turn and trading altitude for speed. Go to the the two Hurricanes in the example. If both are at a high altitude (over 25,000ft) and turning at speed XXX ( Hurricane I is pulling just enough G that it is at full throttle but is neither gaining or loosing speed or gaining or loosing altitude) the Hurricane II has several choices, it can turn at the same speed/radius (G Load) and gain altitude( to be traded later?) or it can pull a tighter radius at the same speed without loosing altitude or it can turn at the same radius but at a higher speed than the MK I without loosing altitude. If the two planes were fighting each other you can see the advantages the better climbing plane has in addition to regaining altitude after a firing pass. Granted both can pull really tight turns and trade several thousands of feet of altitude for a tight turning radius.

Agreed on all accounts.
The high wing loading (in Typhoon's example) is also detrimental factor there, too. The Vulture II can provide a tad more power at altitude, Vulture V providing again more. The Tornado was reaching max speed at 23,300 ft with Vulture V (FTH at 19000 ft?, no ram).

Given a decent radar system the Germans shouldn't have needed fast climbing aircraft to get into firing position. For fighters based in Germany they should have over an hours warning that a raid is coming, granted they don't know WHERE but??? knocking 2-3 minutes of the time to 30,000ft doesn't do much for the intercept. Having a fast climbing fighter may help to evade escort fighters or in the absence of fighters help the interceptors to do multiple firing passes.

I was under impression that great RoC was crucial thing for interceptor

Not in 1940, the first Tomahawk reached England in Sept of 1940. It was certainly faster than a Hurricane, even a MK II.

Indeed. By Sept 1940, the major offensive for that year was vanning. Both British and Germans have already in pipeline newer better performing planes for 1941, while the Curtiss cannot offer anything like that.

added: a member is quoting the person named Rod Banks, that Sabre, per HP delivered, cost 5 times more than Merlin. The long range fighter with 2 Merlins should cost about same as Typhoon/Tempest?

here

 

[Shortround6]

I was talking about the systems that R-2800 had, and the Vulture had not, and vice versa. The P-63 served as an example that a 350 lb cooling system was able to cool the engine developing 1800 HP, so the Vulture's cooling system does need to go to 600+ lbs for 2000 HP.

Two things, ADI acts as an internal coolant in addition to the anti-detonation and charge cooling. And the 1800 hp rating of the P-63 was of limited duration. Try sticking a pair of those engines on a medium bomber and climbing a 35,000-40,000lb plane to 25,000ft with a 300lb radiator systems.

It's NORMAL rating was 1000hp. Max continuous. The Vulture was "supposed" to cruise at 1475-1485hp. That is thing with these "sprint" rated engines, they expected the liquid cooling system to "absorb" the extra heat for a few minutes before the engine cooked. It doesn't mean you can operate 1800hp Allisons, 1800-2000hp DB605s or Merlins using 15+ pounds of boost like you would a real 1700-2000hp engine. Think of them like drag or hill climb engines vs enduro engines

I was under impression that great RoC was crucial thing for interceptor

It was when they were depending on a phone call from a spotting station a few miles from the airfield

15 minute warning vs 60 minute warning? This may have helped Mosquitoes. 8th Air Force bomber groups lumbered across Europe at 180 miles an hour. Granted they dog legged and flew evasive routes but the Germans certainly knew they were going somewhere well before they crossed the German border. Quite a change from 1939/40 when French/British bombers could be based only a few dozen miles from the German Border.

 

[tomo pauk]

Agreed that ADI will act as a coolant, we will need to look at other planes' cooling systems, weight per power. Eg. P-40: 290-300 lbs, up to 1580 HP. P-39: 320-330 lbs, same HP.
I agree that Vulture was supposed to cruise at bigger power, using either 1480 or 1290 HP, 1st or 2nd gear. With a compact cooling system, like P-40, Tornado or Manchester had, that would be some 450 lbs for cooling system?

Quite a change from 1939/40 when French/British bombers could be based only a few dozen miles from the German Border.

Hmm, idea for the new thread - Feasibility of CBO starting at April's fools day, 1940?

 

[tomo pauk]

....
What ones do you want? It was a hypothetical. If the 109 can do 400mph trying to use an escort fighter than can only do 360-370 isn't going to be real successful, especially if the 109 can out climb it. The escort fighter HAS to be able to equal the defender at something ( or come within a couple of percent, 10% is way to much) even if not so good at something else.
....

If I may return on the 360-370 mph speed value.
There is plenty of F4U-1 tests, both for WER-capable and non-WER capable machines, where the F4U does some 370-380 mph at 27-28000 ft. That would run to the contrary with people saying the F4U-1 was the ideal, yet missed opportunity for the bomber escort in ETO? The service ceiling is listed at 34-35000 ft, ie. somewhere between Typhoon and Tempest.
http://www.wwiiaircraftperformance.org/f4u/corsair-II-III-ads-b.jpg

 

[tomo pauk]

The Hawker Tornado was some 10 in longer than Typhoon, the engine protruding more in the front. That would leave more space for fuel tank? The "Centaurus Tornado" giving even more?

 

[Aozora]

The Hawker Tornado was some 10 in longer than Typhoon, the engine protruding more in the front. That would leave more space for fuel tank? The "Centaurus Tornado" giving even more?

View attachment 230165

The reason for the Tornado's greater length was that the R-R Vulture, which was taller than the Sabre, could not be fitted over the main spar, thus it had to be mounted further forward, in addition to which the wings were mounted 3 in lower on the fuselage cf the Typhoon. Even with the extra room the Vulture and its accessories section was longer than the Sabre and the amount of extra fuel that could have been squeezed in would have been too small to justify the weight and balance issues that would have developed. As it was the Tornado did have better longitudinal stability than the Typhoon.

 

[tomo pauk]

Thanks for the insight, Aozora.
Do we know length of the Vulture and war-time Sabres (all with accessories)? The Tornado having no 'weight stability issues'?

added: Sabre II V were 82.2in long, according to the pdf available at WIlliams' site.
added 2: image (here) shows Vulture installation in Tornado. Good call, Aozora, the auxiliary systems seem to take much more space than those of Sabre.
added 3: wuzak's info, from another forum:

I received a reply from the RRHT about the Vulture. The main question about was the overall dimensions of the Vulture, which are:

Length overall - 87.625in/2226mm.
Width overall - 35.8in/909mm.
Height overall - 42.175in/1071mm.
Weight - 2450lb/1111kg