Why did the RAF put so many resources into the Hurricane?

[Shortround6]

What did the Spitfire pick up in speed with the clipped wings? 3-5mph?

It usually isn't worth it for speed alone. The Spitfires wings were a bit weird. You could could cut 4 feet from the pointy ends and not lose too much wing area, planes with blunter wing tips might see an increase in stall speed/landing speed that matched the increase in top speed.

 

[michael rauls]

Agree with the above, with some caveats.

I think the Soviets still had use for the later model P-39s to the end of the war.
In addition to their effective use as fighters in the CBI by the Americans and Pacific by the Australians, the RAF was still using P-40s as fighter bombers in Italy to he end of the war.
They were still FM-2 or some version of the Martlet in the Royal Navy too I think. From the wiki:

"The last air-raid of the war in Europe was carried out by Fleet Air Arm aircraft in Operation Judgement, Kilbotn on May 5, 1945. Twenty eight Wildcat VI aircraft from Naval Air Squadrons 846, 853 and 882, flying from escort carriers, took part in an attack on a U-boat depot near Harstad, Norway. Two ships and a U-boat were sunk with the loss of one Wildcat and one Avenger torpedo-bomber. "

In a nutshell there were different types of Theaters, i.e. the Russian Front was much more focused on Low Altitude combat and had little requirement for long range, compared to NW Europe, and there were secondary (ala Italy) and Tertiary (CBI) Theaters where the 1941 and 1942 vintage aircraft still worked.

Not certain about the Hurricane in the CBI though I'd like to see some Operational history data for that.

Wow, the last air raid of the war in Europe was carried out by Wildcats and Avengers.
Not exactly what I would have expected to hear.
There sure was a lot of stuff going on in the war that somehow didn't seem to make it onto the consciousness of most of the history book writers.

 

[Kevin J]

Think about this mod for the Hurricane. The original design has STOL, 40 feet wings, eight guns and a 1000 hp engine. Why not clip the wings, replace the 303's with 50's, and put in a Merlin 60 series engine with individual exhaust ejectors. Suddenly, the Hurricane is no longer 10% slower than a Spitfire but maybe just 5%, and the dive speed has increased to 460 mph. Better still, use a Mustang style radiator and its 5% faster than a Spitfire. Then you think, hey wait a minute, the Boss might cancel my Typhoon and Tempest projects, this might not be a good idea.

 

[buffnut453]

The 50cal was never a primary weapon for the RAF so changing to that weapon for the Hurricane is introducing a host of logistical and maintenance challenges that will have a significant diluting effect on operational effectiveness. In addition, the use of 50cals in wing installations was problematic thru to the latter half of 1942 in a range of aircraft. I think the use of 50cals is a non-starter (IMHO).

Overall, this concept puts a lot of effort into a design that was fundamentally obsolescent by the autumn of 1940. There isn't another fighter among the major powers that still has main components covered in doped fabric. The reason is that doped fabric over a frame isn't as strong as monocoque construction. With shorter wings and a structure that's weaker than monocoque, you may hurt manoeuvrability, which was one of the Hurricane's key strengths. I'm not sure the juice is worth the squeeze.

Don't get me wrong. I love the Hurricane. Always have, always will. It was the right aircraft in the right place at the right time in the spring/summer of 1940 but after that it falls back quickly relative to its competitors. The only way to substantially improve things is an entirely new design.

 

[Kevin J]

The 50cal was never a primary weapon for the RAF so changing to that weapon for the Hurricane is introducing a host of logistical and maintenance challenges that will have a significant diluting effect on operational effectiveness. In addition, the use of 50cals in wing installations was problematic thru to the latter half of 1942 in a range of aircraft. Overall, I think the use of 50cals is a non-starter (IMHO).

Overall, this concept puts a lot of effort into a design that was fundamentally obsolescent by the autumn of 1940. There isn't another fighter among the major powers that still has main components covered in doped fabric. The reason is that doped fabric over a frame isn't as strong as monocoque construction. With shorter wings and a structure that's weaker than monocoque, you may hurt manoeuvrability, which was one of the Hurricane's key strengths. I'm not sure the juice is worth the squeeze.

Don't get me wrong. I love the Hurricane. Always have, always will. It was the right aircraft in the right place at the right time in the spring/summer of 1940 but after that it falls back quickly relative to its competitors. The only way to substantially improve things is an entirely new design.

I think you'll find that the only fabric bits left on the Hurricane by 1940 was the tail section, wasn't that the same as the Corsair? As for the 50's, well maybe instead a couple of 20 mm cannon and four 303's. Certainly later Fulmars and some Canadian built Hurricanes got 50's so its not beyond the realms of possibility. Talking about a clipped wing Hurricane immediately turns my mind to the M.B. 3 & 5 prototypes. The Hurricane could have been improved but it would have lost Hawker its Typhoon and Tempest business.

 

[buffnut453]

It wasn't just the "tail section" that was fabric covered. It was the entire fuselage aft of the cockpit. That's a substantial piece of the structure. The Corsair was entirely monocoque.

Comparing the Fulmar to the Hurricane in terms of logistical impact isn't really relevant. Only about 600 Fulmars were built compared to over 14,000 Hurris.

 

[Elmas]

"Beauty is but skin deep…" and one has to see what there is under that skin.

Most of the cost of an airplane to be produced in large series is represented by tooling and jigs, so one of the strong points of Hurricane, the ease of construction due to well tested building methods, but obsolete by late '30-early '40s, was also one of his weaknesses. A complete retooling for an airplane who had, from the start, some aerodynamic limitations, was a nonsense well understood by MAP.

 

[wuzak]

What did the Spitfire pick up in speed with the clipped wings? 3-5mph?

It usually isn't worth it for speed alone. The Spitfires wings were a bit weird. You could could cut 4 feet from the pointy ends and not lose too much wing area, planes with blunter wing tips might see an increase in stall speed/landing speed that matched the increase in top speed.

I believe the Spitfire lost speed with clipped wings - but maybe only at higher altitudes.

The big gain was roll rate, of course, but the biggest loss was climb rate.

The other thing about clipping Spitfire wings was that the wing tips were bolt on pieces, so they could be removed and squared off short span tips installed, or long span pointy wing tips for high altitude versions. No structural modifications were necessary.

In the Hurricane's case the wing itself would have to be modified. Which may take a lot of work and delay production.

 

[wuzak]

The problems with the Typhoon, just like the Americans problems with the P-46, P-60 et al meant the Hurricane was still needed at least through 1943.

The Typhoon clearly didn't have as many problems as the P-46, P-60, etc, because

1. it went into volume production
2. it went into service with the RAF

 

[Kevin J]

Continuing on with my Hurricane suggestion. I have no doubt that 50's would not have been available for any Merlin 60 powered Hurricane. My suggestions aimed to make you think, as Hitler once said "my generals don't understand the economic aspects of war". If Hawkers were to propose a clipped wing Hurricane with a Mustang style radiator and individual exhausts for the Merlin then maybe the Air Ministry would question why they needed the Typhoon or Tempest. I still think they would have done, but would Hawkers want to take the risk? You would get improved roll rate and a higher dive speed in a more rugged fighter than the Spitfire, maybe one better suited to the Asia-Pacific theatre where boom and zoom was the tactic. As for everything aft of the cockpit being fabric, well the increased weight of the Merlin 60 series engine would require more weight aft, so replace that fabric with stressed skin.

Its like Auschwitz, if you wanted to kill people, it certainly wasn't the most efficient production line method, but then if you're a businessman would you really design a system that would get you hung after the war. No you'd design and quote a system that hopefully was rejected.

The LF Spitfire gained about 5 mph below 20 thou feet and lost it above that IIRC.

 

[pbehn]

Think about this mod for the Hurricane. The original design has STOL, 40 feet wings, eight guns and a 1000 hp engine. Why not clip the wings, replace the 303's with 50's, and put in a Merlin 60 series engine with individual exhaust ejectors. Suddenly, the Hurricane is no longer 10% slower than a Spitfire but maybe just 5%, and the dive speed has increased to 460 mph. Better still, use a Mustang style radiator and its 5% faster than a Spitfire. Then you think, hey wait a minute, the Boss might cancel my Typhoon and Tempest projects, this might not be a good idea.

That sounds remarkably like a P-51 which the British ordered in 1940 off the drawing board and was in service in 1942, fitted with a Merlin engine in 1943.

 

[Shortround6]

Think about this mod for the Hurricane. The original design has STOL, 40 feet wings, eight guns and a 1000 hp engine. Why not clip the wings, replace the 303's with 50's, and put in a Merlin 60 series engine with individual exhaust ejectors. Suddenly, the Hurricane is no longer 10% slower than a Spitfire but maybe just 5%, and the dive speed has increased to 460 mph. Better still, use a Mustang style radiator and its 5% faster than a Spitfire. Then you think, hey wait a minute, the Boss might cancel my Typhoon and Tempest projects, this might not be a good idea.

A fair amount of the Hurricanes STOL performance (and this is only in comparison to later aircraft, contemporary aircraft weren't that different) was the airfoil used.

Chopping 1 1/2 to 2 feet off each wingtip does nothing to change the lift/drag of the rest of wing.

replacing the wing tips outboard of the end of ailerons just isn't going to get you much in the way of reducing drag. Reducing the size of the ailerons sure isn't going to do much for the roll rate.
The Hurricane II had the Merlin XX engine almost two years before the two stage Merlin shows up in quantity. It had several hundred more horsepower than the Merlin III engine in the Hurricane I. By the time the Merlin 60 shows up they had been fitting Hurricanes with 20mm cannon for well over 6 months.
Hurricanes may not have had individual exhausts but they were using ejector exhaust systems.

by Robert Phelan
RR did some rather extensive tests on ejector exhausts, including running an engine in a test house with nozzles of different sizes going into a baffle box of a type developed by the Steam Nozzle Research Committee.
Yes a Merlin 60 does put out more exhaust than a Merlin XX but not much more (especially at similar boost pressures.)

The Mustang radiator was NOT an add on accessory below the fuselage, no matter how big the scoop appears. a lot of the radiator and duct was up inside the fuselage.

Which on a Hurricane means cutting away a lot of the stringers/frames in the bottom of the fuselage.

Perhaps it could be done, but it is hardly a wam-bam, thank you mam proposition. Start extensive modifications to the fuselage structure right behind the wing (and on the Hurricane the radiator was under the pilot, not behind him) and you have to redo all the stress calculations for the rear of the fuselage.
and........................

area behind pilot was full of radio gear. The 'tube" just visible in the right hand side of the opening was the landing flare tube (one of two) used for dropping parachute flares to illuminate a landing area at night that didn't have runway lights. These may have been deleted in later aircraft.

The boss might say " why are you still flogging this dead horse? why aren't you working on the Tempest project?"

 

[Kevin J]

A fair amount of the Hurricanes STOL performance (and this is only in comparison to later aircraft, contemporary aircraft weren't that different) was the airfoil used.
View attachment 526127
Chopping 1 1/2 to 2 feet off each wingtip does nothing to change the lift/drag of the rest of wing.
View attachment 526128
replacing the wing tips outboard of the end of ailerons just isn't going to get you much in the way of reducing drag. Reducing the size of the ailerons sure isn't going to do much for the roll rate.
The Hurricane II had the Merlin XX engine almost two years before the two stage Merlin shows up in quantity. It had several hundred more horsepower than the Merlin III engine in the Hurricane I. By the time the Merlin 60 shows up they had been fitting Hurricanes with 20mm cannon for well over 6 months.
Hurricanes may not have had individual exhausts but they were using ejector exhaust systems.
View attachment 526129 by Robert Phelan
RR did some rather extensive tests on ejector exhausts, including running an engine in a test house with nozzles of different sizes going into a baffle box of a type developed by the Steam Nozzle Research Committee.
Yes a Merlin 60 does put out more exhaust than a Merlin XX but not much more (especially at similar boost pressures.)

The Mustang radiator was NOT an add on accessory below the fuselage, no matter how big the scoop appears. a lot of the radiator and duct was up inside the fuselage.
View attachment 526130
Which on a Hurricane means cutting away a lot of the stringers/frames in the bottom of the fuselage.
View attachment 526131
Perhaps it could be done, but it is hardly a wam-bam, thank you mam proposition. Start extensive modifications to the fuselage structure right behind the wing (and on the Hurricane the radiator was under the pilot, not behind him) and you have to redo all the stress calculations for the rear of the fuselage.
and........................
View attachment 526132
area behind pilot was full of radio gear. The 'tube" just visible in the right hand side of the opening was the landing flare tube (one of two) used for dropping parachute flares to illuminate a landing area at night that didn't have runway lights. These may have been deleted in later aircraft.

The boss might say " why are you still flogging this dead horse? why aren't you working on the Tempest project?"

Okay, so we need the radiator under the engine and a laminar flow wingplus the individual ejector exhausts. It did wonders for the hook only Sea Hurricane IIc as it did the same speed as the Hurricane IIa.

 

[Shortround6]

Okay, so we need the radiator under the engine and a laminar flow wingplus the individual ejector exhausts. It did wonders for the hook only Sea Hurricane IIc as it did the same speed as the Hurricane IIa.

you are really expecting miracles from the individual exhaust stacks.
In some of the RR tests they figured they were getting 86.5hp from the exhaust at 15,000 from the Merlin XX. This is with an intake pressure of 48.24in and a charge weight(weight of fuel and air) of 140.5lbs per minute and an ejector jet velocity of 1395fps.(aircraft speed 325mph)
At 20,000ft they got 113. hp at the same manifold pressure and a charge weight of 144lbs, ejector jet velocity 1695fps. (aircraft speed 335mph)
At 25,000ft they got 107.2 hp at 42.12 manifold pressure and a charge weight of 129.1lbs, ejector jet velocity 1840fps. (aircraft speed 330mph)
At 30,000ft they were back to 89hp at the 34.30 manifold pressure and a charge weight of 107.2lbs, ejector jet velocity 1901fps. (aircraft speed 317mph).

Granted there are trade offs between flame damping and peak exhaust thrust but then the exhaust nozzles can only be optimized for one speed at one altitude at one charge flow.
Any other conditions are a compromise. Since at any altitude much above 15,000 ft the exhaust thrust was already exceeding 10% of the brake horsepower I don't see where a change to single stacks was going to really make much more power.
I would note that a text book of the time says that while one cylinder per stack is optimum, three cylinders can use one stack/pipe and still show a useful gain. This assumes of course that the the cylinders fire an equal time apart. The Hurricane's use of two cylinders per stack/nozzle might not be optimum but it was hardly crippling (and most Spitfires of 1940-42 used the same two cylinders into one nozzle design)

 

[nuuumannn]

The Typhoon clearly didn't have as many problems as the P-46, P-60, etc,

Don't get me wrong here wuzak, but this does need to be put into perspective a little. Neither of the US types suffered massive structural failure with their tails falling off either. As much as the Typhoon entered RAF service, it was not in the role it was designed for and not to denigrate the aircraft, it had a habit of doing that itself, its performance was not up to scratch for the interceptor role, as fast as it was, then there was the difficulties of the Sabre engine itself, which all led to discussions about a possible withdrawal from service. It was actually grounded at one point owing to a failure of a seal, which led to carbon monoxide entering the cockpit.

Perhaps not the best example for comparison, although you are right about it entering service and production, and actions speak louder than words and as an attack aircraft it excelled and gave exceptional service.

 

[nuuumannn]

Continuing on with my Hurricane suggestion.

The boss might say "why are you still flogging this dead horse? why aren't you working on the Tempest project?"

Sums it up nicely.

 

[Kevin J]

Sums it up nicely.

There was a little bit more mileage that could have been got out of the Hurricane II even in 1942, namely individual exhaust stubs and armament reduced to 6 303's with the missing gun in either wing being used as an attachment point for a drop tank. My estimate on top speed 355 mph. Okay for the Far East.

 

[michael rauls]

Certainly the Hurricane could have been updated or evolved into a more modern fighter. A redesigned wing. A more powerful engine. I imagine however that at some point it becomes cheaper and more practical to start over and design a new aircraft from scratch.
Did the Hurricane have more practical evolution left in it than was tapped?
An interesting question and one for those with more knowledge about aircraft design than myself.

 

[Shortround6]

There was a little bit more mileage that could have been got out of the Hurricane II even in 1942, namely individual exhaust stubs and armament reduced to 6 303's with the missing gun in either wing being used as an attachment point for a drop tank. My estimate on top speed 355 mph. Okay for the Far East.

Have you actually looked at the development of the Hurricane? Or the weights?

Yanking one .303 gun and 334 rounds of ammo from each wing saves a trivial amount of weight. Like about 100lbs total. Changing weights (guns) does very little for speed as the change in drag for guns that do not protrude from the wings is confined to the increase in incidence of wing to create the extra lift and the slot for the fired cases to fall through. The "factory" figures for the difference between a IIa (eight guns) and a IIb (twelve guns) was 2 mph. going from right guns to six is going to get you ?????? 1mph??? if you are lucky.
The change in climb is a bit different, the extra four guns cost 0.3 minutes (18 seconds) to 20,000ft. A lot of Hurricanes failed to meet these 'factory' figures on test. A "tropical" IIB lost another 16mph of speed and took 2.7 minutes longer to get to 20,000ft. it also lost about 30 miles of range on internal fuel and 60 miles range when carrying drop tanks.
Hurricane IIs were carrying drop tanks in 1941, there is no need to take out a gun in order fit a drop tank.
44 imp gallons of fuel weighs about 316lbs, add the weight of the tank and the mount for a 28lb machine gun is not going to be anywhere near strong enough to hold it.

I have yet to see anything that would suggest the change from paired exhaust stacks to individual exhaust stubs would add anywhere near the power required to get a Hurricane anywhere near 355mph.

The Cube rule says that if a Hurricane needed 1253 HP (1126hp to the prop and 127 hp exhaust thrust) to go 340mph it is going to need 1423hp to go 355mph.
Granted crankshaft power to the prop is not thrust and the 127 hp exhaust HP is after the thrust is converted to HP at the speed the aircraft is moving, so I may (am ) mixing things up a bit. However you still need another 180hp or something near it and changing from paired stacks to individual stacks is not going to double the exhaust HP or change the the power developed in the cylinders by any great amount.
I would note that Hawker Typhoons and Tempests used paired exhaust stacks, two cylinders sharing one outlet.

Late model Spitfires did use individual stacks, but they used several different kinds and at least one of them looks a bit dubious for getting a whole lot for high speed flight.

Stacks that do not turn the exhaust flow to line up with the direction of flight introduce a vector problem to figuring out how much power is contributing to making the plane go forward and how much is trying to make the plane go sideways (counter acted by stacks on the other side).

I don't know but am making a wild guess that perhaps the round, more open exhaust was used on low altitude planes.

©Nigel Key

The exhaust velocity being much higher in the thinner high altitude air and generating more power for the same charge weight.
At low altitude the exhaust power could be much lower?

 

[Kevin J]

Have you actually looked at the development of the Hurricane? Or the weights?

Yanking one .303 gun and 334 rounds of ammo from each wing saves a trivial amount of weight. Like about 100lbs total. Changing weights (guns) does very little for speed as the change in drag for guns that do not protrude from the wings is confined to the increase in incidence of wing to create the extra lift and the slot for the fired cases to fall through. The "factory" figures for the difference between a IIa (eight guns) and a IIb (twelve guns) was 2 mph. going from right guns to six is going to get you ?????? 1mph??? if you are lucky.
The change in climb is a bit different, the extra four guns cost 0.3 minutes (18 seconds) to 20,000ft. A lot of Hurricanes failed to meet these 'factory' figures on test. A "tropical" IIB lost another 16mph of speed and took 2.7 minutes longer to get to 20,000ft. it also lost about 30 miles of range on internal fuel and 60 miles range when carrying drop tanks.
Hurricane IIs were carrying drop tanks in 1941, there is no need to take out a gun in order fit a drop tank.
44 imp gallons of fuel weighs about 316lbs, add the weight of the tank and the mount for a 28lb machine gun is not going to be anywhere near strong enough to hold it.

I have yet to see anything that would suggest the change from paired exhaust stacks to individual exhaust stubs would add anywhere near the power required to get a Hurricane anywhere near 355mph.

The Cube rule says that if a Hurricane needed 1253 HP (1126hp to the prop and 127 hp exhaust thrust) to go 340mph it is going to need 1423hp to go 355mph.
Granted crankshaft power to the prop is not thrust and the 127 hp exhaust HP is after the thrust is converted to HP at the speed the aircraft is moving, so I may (am ) mixing things up a bit. However you still need another 180hp or something near it and changing from paired stacks to individual stacks is not going to double the exhaust HP or change the the power developed in the cylinders by any great amount.
I would note that Hawker Typhoons and Tempests used paired exhaust stacks, two cylinders sharing one outlet.

Late model Spitfires did use individual stacks, but they used several different kinds and at least one of them looks a bit dubious for getting a whole lot for high speed flight.
View attachment 526202
Stacks that do not turn the exhaust flow to line up with the direction of flight introduce a vector problem to figuring out how much power is contributing to making the plane go forward and how much is trying to make the plane go sideways (counter acted by stacks on the other side).

I don't know but am making a wild guess that perhaps the round, more open exhaust was used on low altitude planes.
View attachment 526203 ©Nigel Key

The exhaust velocity being much higher in the thinner high altitude air and generating more power for the same charge weight.
At low altitude the exhaust power could be much lower?

The Sea Hurricane IIc did the same 342 mph at 22000 feet that a Hurricane IIa did at the same height. It had the added burden of an arrestor hook that cost 6/7 mph depending on altitude. The standard IIc did 336 mph., 6 mph less than the IIa. Add 7, 6 and 342 and you get 355 mph for the Hurricane IIa with individual exhausts.