More fuel in Hurricane?

[hobbes154]

Based on discussions like this, just wondering if there is any practical way to fit more than 97 imperial gallons of fuel in the Hurricane while remaining a useful fighter? Just on gross size - bigger and thicker wings than Mustang (224 imperial gallons or about 150 without rear tank?) - seems like it should be possible, particularly once you get stressed-skin wings?

Particularly wondering if the radiator was moved/deleted (Hercules!) could a tank be fitted under the pilot, or does the steel tube construction take up too much space? The wheels get in the way too. https://ww2aircraft.net/forum/attachments/1730592675350-png.804041/

Or is there a reason not to have a bigger tank in front of the pilot? Spitfire seemed to fit a lot more in there.

Cutaways:
Hawker-Hurricane-cutaway | HistoryNet
https://conceptbunny.com/wp-content/uploads/2019/04/hawker-hurricane.gif

 

[Shortround6]

The Hurricane was either a little nose heavy or tail light, your choice,
It did not like weights much under the cockpit or behind the the cockpit.
Somebody can correct me but the CG was just under 30% of cord. Any weights added to the rear affected handling.
Before you say that plane X did it, consider that for instance, the Mustang was about 1000 heavier without fuel than a Hurricane weighed with full internal fuel. 300lbs 50 in behind the CG on Mustang is bad but not as bad as 300lbs 50in behind the CG on the Hurricane (the 300lbs is a smaller percentage of total weight.)
Some wings/airfoils tolerated CG changes better than others. Some planes tolerated changes in CG better than others due to the horizontal stabilizer and trim.

The P-36/ P-40 is a classic case of weight and trim. You could fly a P-36/Hawk 75 with the tank behind the pilot full for ferry flights. It was dangerous to try to do combat maneuvers with the tank full or part full. French lost more than one Hawk 75 that way. P-40s with the longer/heavier V-12 in the nose were fine flying with the tank near full, no restrictions in the manual.
P-40Fs and Ls with the even heavier Merlins wanted the pilots to keep 25 gallons in the rear tank at all times and only the 25 gallons for reserve and landing. In the Allison P-40s they wanted the rear tank drained after take-off and the forward tank was the reserve fuel supply.

Hercules in a Hurricane was a disaster waiting to happen in 1940-41.

 

[Airframes]

Is there much point in extra fuel, in the originally intended role of the Hurricane ?
As a UK airspace defence interceptor, the Hurricane would have run out of ammunition before running out of fuel.
Of course, if used in the "old fashioned" standing patrol, flying back and forth waiting for the enemy, extra fuel may be a benefit, but then, under the "Dowding system", standing patrols were more or less abandoned.

 

[tomo pauk]

Based on discussions like this, just wondering if there is any practical way to fit more than 97 imperial gallons of fuel in the Hurricane while remaining a useful fighter? Just on gross size - bigger and thicker wings than Mustang (224 imperial gallons or about 150 without rear tank?) - seems like it should be possible, particularly once you get stressed-skin wings?

Hurricane, along with the next-gen piston-engined fighters from the Hawker stable, was with the stowed landing gear volume between the spars. That way, a good deal of the very suitable CoG-neutral volume was dedicated for a non-consumable thing, meaning that fuel tanks will be scattered all around the aircraft, much reducing the useful volume for the fuel. If the landing gear can be retracted outward (requiring the re-hash of the weapon layout), that leaves a lot of volume for the fuel tanks between the U/C hinge points. Not inconceivable - Re.2005 received that way of retracting. And probably far easier to make than it was using the Hurricane as a parts donor to arrive at the Hotspur, for example (Hurricanes wing + new fuselage).
Another thing to attempt is to shift the cockpit a feet or two backwards, so a bigger CoG-neutral fuel tabnk can be installed between the pilot and the engine. Again, not unheard of, we know that Yak-9 gotten that type of remake in order that a 37mm cannon can fit, or the additional fuel tank as in the -9DD version.
Redesigning of the wing leading edge might've been easiest to pull among the CoG-neutral surgeries, and historically it was done with Tempest, that 1st gotten extra fuel tankage in one leading edge, and then in another. Also a part of the process that saw the P-47N getting more fuel.
Have the fuel tanks span as much as possible from fuselage to the 1st blast tubes.

Trying to fit a perhaps the 29 gal tank as it was done on some Spitfires would've been the easiest job as far as modifications are debated. For the pilot-friendly usage, have that tank to feed directly in one of the wing tanks, or at the bottom of the fuselage tank, and to be receiving the cooled exhaust gasses in order to have the lower susceptibility of fire when empty.

Is there much point in extra fuel, in the originally intended role of the Hurricane ?
As a UK airspace defence interceptor, the Hurricane would have run out of ammunition before running out of fuel.
Of course, if used in the "old fashioned" standing patrol, flying back and forth waiting for the enemy, extra fuel may be a benefit, but then, under the "Dowding system", standing patrols were more or less abandoned.

There is a lot of world-spanning British Empire beyond UK that might use a long-range fighter

 

[Elan Vital]

Another thing to attempt is to shift the cockpit a feet or two backwards, so a bigger CoG-neutral fuel tabnk can be installed between the pilot and the engine. Again, not unheard of, we know that Yak-9 gotten that type of remake in order that a 37mm cannon can fit, or the additional fuel tank as in the -9DD version.

AFAIK this is also what Bloch 155 did compared to its predecessor.

 

[Shortround6]

More fuel in Hurricane?

What are you willing to give up to get it?
Climb?
Take-off performance?
Ceiling?
Armament?

Every plane is bunch of trade offs.
I will also note that many of the P-40 performance specifications were done with with 120 US gallons of fuel (100 imperial) and not the 148-157 US gal (123-131 G Imp) that the internal tanks would hold.

 

[tomo pauk]

More fuel in Hurricane?

What are you willing to give up to get it?
Climb?
Take-off performance?
Ceiling?
Armament?

Every plane is bunch of trade offs.
I will also note that many of the P-40 performance specifications were done with with 120 US gallons of fuel (100 imperial) and not the 148-157 US gal (123-131 G Imp) that the internal tanks would hold.

I'm not sure what is the fuss. Everyone tried to add more fuel to their aircraft, be it via increase of internal fuel tankage or via installation of the drop tanks, or both. The only problem was that the epiphany of greater_range = better_fighter happened later for some people.

The high rates of climb, like during the defense of the one's own territory, require not filling up the tanks to 100%. No Nobel price required there.

 

[Shortround6]

I'm not sure what is the fuss. Everyone tried to add more fuel to their aircraft, be it via increase of internal fuel tankage or via installation of the drop tanks, or both. The only problem was that the epiphany of greater_range = better_fighter happened later for some people.

The high rates of climb, like during the defense of the one's own territory, require not filling up the tanks to 100%. No Nobel price required there.

This is all true but it does overlook the fact than many/most planes that got increased internal fuel also got higher powered engines and many times better runways (longer) to operate from.
Hurricanes got a pair of 44imp gal drop tanks for combat and larger for Ferry. Need for increased internal fuel was not as pressing. 436 liters of external fuel compared to the 109s 300 liters?
Hurricane was also rather on draggy side, it was going to burn a lot of fuel trying to fly very far at anything approaching a fast cruise.

For some ballpark numbers look at the numbers from a P-40F which used the engine as a Hurricane II but was around 30mph faster (depends on source and armament in the Hurricane).
A P-40F will "cruise" at 327mph at 20,000ft but it is burning about 84imp gal an hour. Slower is going to save fuel but Hurricane is never going to be a long range escort (unless for Blenheims).

you can fly Hurricanes from one air field to another over decent distances, what is a lot harder is getting into enemy air space and getting back out

And again the Hurricane didn't get the two pitch prop for the over a year of it's service life. The two pitch helped getting of the field, it didn't do squat for climb. The constant speed prop helped with that but that didn't show up until the summer of 1940. Once the new prop took 1 1/2 to 2 minutes off the time to 20,000ft perhaps they could think about putting more weight (fuel) in the plane.
The Hurricane IIA with just eight guns knocked another 1.2 minutes off the climb to 20,000ft so perhaps there was an opportunity to trade fuel for the four extra guns on the IIB that added 0.3 minutes to 20,000ft?
The IIA was 3.1 minutes faster than the MK I with the Watts 2 blade, it was also over 500lbs heavier empty due the engine, prop and protection/electronics.

So when do you start putting in more fuel and what sacrifices do you make when?

Japanese Ki-43 didn't get the under wing drop tanks until it got a new wing, an engine with a 2 speed supercharger and about 15% more power for take-off and 3 bladed prop instead of two blade.

 

[tomo pauk]

This is all true but it does overlook the fact than many/most planes that got increased internal fuel also got higher powered engines and many times better runways (longer) to operate from.
Hurricanes got a pair of 44imp gal drop tanks for combat and larger for Ferry. Need for increased internal fuel was not as pressing. 436 liters of external fuel compared to the 109s 300 liters?
Hurricane was also rather on draggy side, it was going to burn a lot of fuel trying to fly very far at anything approaching a fast cruise.

This is where the increased internal fuel tankage is great - it does not add up the drag more than it is a rounding error.

For some ballpark numbers look at the numbers from a P-40F which used the engine as a Hurricane II but was around 30mph faster (depends on source and armament in the Hurricane).
A P-40F will "cruise" at 327mph at 20,000ft but it is burning about 84imp gal an hour. Slower is going to save fuel but Hurricane is never going to be a long range escort (unless for Blenheims).

Picking up the worst case scenario here: demanding that P-40F cruise faster than P-47 or P-51B/D? C'mon.

you can fly Hurricanes from one air field to another over decent distances, what is a lot harder is getting into enemy air space and getting back out

Again advantage of the increased internal fuel: return_to_base fuel is considerably greater.

So when do you start putting in more fuel and what sacrifices do you make when?

Preferably, by the time Mk.1 is in production.
There is enough of dead wood to trim in the British A/C procurement between 1935 and 1941, more than enough to double the production of Hurricanes in the era.

 

[Shortround6]

Picking up the worst case scenario here: demanding that P-40F cruise faster than P-47 or P-51B/D? C'mon.

Pointing out that the P-40F can fly at max continuous (2650rpm and 39in) at just under the speed that a Hurricane II needs 3000rpm and 44in to fly.
Hurricane is going to use more fuel at any speed than a P-40F.

Again advantage of the increased internal fuel: return_to_base fuel is considerably greater.

Only if you can return to base without getting shot down. Flying 15-20mph slower than P-40F is going to make a Hurricane II an easier target. A Hurricane I is even slower but then the enemy aircraft aren't as fast so maybe it evens out.

Preferably, by the time Mk.1 is in production.
There is enough of dead wood to trim in the British A/C procurement between 1935 and 1941, more than enough to double the production of Hurricanes in the era.

We have been over this a number of times. Cutting out the 'dead wood' pretty much means the Battle. Defiant wasn't in production in numbers until 1940 and the only other plane using the Merlin III engine in numbers higher than single digits was the Henley.
Put your 29 gallon tank into a Spitfire, at least you have chance. A Hurricane I is not a penetrating aircraft. It is about 30mph slower than a Spitfire I with the same engine as we know.
There may have been reasons why the British did most of the experiments with extra fuel on the Spitfires.

 

[hobbes154]

The Hurricane was either a little nose heavy or tail light, your choice,
It did not like weights much under the cockpit or behind the the cockpit.

I might be a dumbass here but isn't this contradictory? If it's nose heavy/tail light shouldn't weight behind the cockpit help? (And if it's nose light/tail heavy isn't there room for a bigger front tank? Or if it's well balanced as is there's room for both?)

Hercules in a Hurricane was a disaster waiting to happen in 1940-41.

For the usual production/reliability issues or because you think it would not mate well with the Hurricane specifically (as below, I am not claiming it would help performance as a pure interceptor)?

Is there much point in extra fuel, in the originally intended role of the Hurricane ?

No, I'm thinking more of carrier fighter (as in original link) or fighter-bomber.

What are you willing to give up to get it?

I guess I'm thinking of keeping it useful for longer in the above roles and just not losing range as it gets more powerful engines.

 

[Engineman]

In modern vintage operation, the Hawker Hurricane is known for being very sensitive to C of G and weight distribution. Of course, all aircraft have or had laid down limitations, but the Hurricane is known to be particularly sensitive to handling in pitch.

Eng

 

[yulzari]

I have no idea of what else was moved around but I do note that a few Soviet Hurricanes were converted to two seaters with a gunner/observer at the back for artillery spotting.That has to about 120kg extra behind the normal CofG.

 

[Geoffrey Sinclair]

RAF figures,
Hurricane production began in December 1937, Merlin III fitted in production from April 1939, two pitch propeller from June 1939, constant speed propellers from end February 1940, the mark II was to have been the Spitfire change over to constant speed propellers.

Hurricane I, 97 gallons of 87 octane fuel, 77.6 gallons available for cruise at 15,000 feet, range De Havilland propeller 455 miles at 275mph, Rotol propeller 445 miles at 272 mph, economic cruise both propellers 600 miles at 180 mph (De Havilland) and 170-180 mph (Rotol).

Hurricane IIA, 97 gallons of 100 octane fuel, 68 gallons available for cruise at 15,000 feet, range 524 miles at 168 to 176 mph, 7.7 ampg.
Hurricane IIC, 97 gallons of 100 octane fuel, 68 gallons available for cruise at 15,000 feet, range 500 miles at 165 to 170 mph, 7.35 ampg.

Francis Mason figures,
Hurricane I, datum point 21.2 inches below thrust line and 28 inches forward of the wing leading edge extended to the centre line. CoG at normal weight 57.3 inches aft of datum point, GoG limits 54.9 to 58.7 inches aft of datum point.

Hurricane II, datum point 21.6 inches below thrust line and 30 inches forward of the wing leading edge extended to the centre line. CoG at normal weight 9.45 inches above and 59.5 inches aft of datum point, GoG limits 57 to 60 inches aft of datum point.

Range miles, Merlin II used the wooden propeller

Model	Speed	97 gallons	97 + 2x44	97 + 2x90	97 gallons
Model	mph	97 gallons	gallon external	gallon external	less 20 min res.
I (Merlin II)	190​	525​	n/a	n/a	440​
I Rotol Prop.	190​	505​	n/a	n/a	425​
I (Trop) Rotol	190​	460​	935​	n/a	380​
IIA	177​	468​	946​	1,090​
IIA (Trop)	185​	440​	900​	1,015​
IIB	177​	465​	935​	1,080​
IIB (Trop)	185​	436​	880​	1,010​
IIC	178​	460​	920​	1,086​
IIC (Trop)	188​	426​	908​	1,022​
IID	186​	420​	895​	1,020​
IID (Trop)	192​	404​	870​	995​
Sea IIC	180​	452​	908​	1,062​
Sea IIC (Trop)	190​	415​	895​	998​

either the 90 gallon tanks had a huge amount of drag or something is wrong or not accounted for (oil capacity?)

 

[Shortround6]

A big thank you for all of those numbers in on place.

Something does seem to be off with the 90 gallon numbers as you noted.
plane....................44 gallon tanks.......................90 gallon tanks
IIA.........................946.........................................................1090
IIB.........................935.........................................................1080
IIC.........................920........................................................1086(?)
IID........................895.........................................................1020

Maybe the IIC should have been 1068?
You may be right about the oil. Spitfires with long range tanks got larger oil tanks.
Maybe they did put larger oil tanks in the Hurricanes but they don't show up externally and it is not mentioned in in most (any?) accounts.
The existing oil tank formed part of the leading edge of the port wing.

Maybe there was a way to add another tank?

I do have to ask if the ranges at " 68 gallons available for cruise at 15,000 feet, range 524 miles at 168 to 176 mph, 7.7 ampg." is just cruising and the 68 gallons was what was left after after warm up, take-off and climb to 15,000ft with a margin/reserve for landing?
Fuel burn in combat could be around 1 3/4-2 gal per minute depending on boost used (9lbs-12lbs)?

 

[tomo pauk]

Only if you can return to base without getting shot down. Flying 15-20mph slower than P-40F is going to make a Hurricane II an easier target. A Hurricane I is even slower but then the enemy aircraft aren't as fast so maybe it evens out.

Hopefully, people in the charge will be having these Hurricanes escorting something, not just idly sending them with no purpose. Leaving to the Axis commanders with a decision to make: should we attack the bombers, or the escorting Hurricanes?
Not every Axis fighter was a Bf 109F or a MC.202.

We have been over this a number of times. Cutting out the 'dead wood' pretty much means the Battle. Defiant wasn't in production in numbers until 1940 and the only other plane using the Merlin III engine in numbers higher than single digits was the Henley.

Before 1940, dead wood wrt. the useless development were Hotspur, plus the two Gloster fighters (keeping the things in family for the moment). The development resources and time can be spent in making the Hurricane better, including extending the range.
Then we indeed have the Henley to be cancelled both because of the time and development it sucked up, as well as due to the usage of Merlin engines and excellent propellers.
Defiant also need to meet the swift end, and have BP make something useful. In the spirit of this thread, they can star making Hurricanes before ww2 starts.

 

[Shortround6]

Defiant also need to meet the swift end, and have BP make something useful. In the spirit of this thread, they can star making Hurricanes before ww2 starts.

Wait!!! That means BP won't be able to build Roc's under subcontract! Without Roc's the Empire is facing imminent doom
Maybe Blackburn and or BP could have tried making a folding wing Hurricane?

Then we indeed have the Henley to be cancelled both because of the time and development it sucked up, as well as due to the usage of Merlin engines and excellent propellers

I am not sure about the propeller, source vary but some say two pitch. This may have been part of the problem as a dive bomber.

Before 1940, dead wood wrt. the useless development were Hotspur, plus the two Gloster fighters (keeping the things in family for the moment). The development resources and time can be spent in making the Hurricane better, including extending the range.

Basically the problem with a long range Hurricane is that the thing is flying barn door. It's huge wing offered the ability to lift a large load out of a small runway (once they got CS props) but it's large size and thickness was always going to be high drag (unless you are talking about changing the wing) and the Spitfire is always going to offer more miles per gallon of fuel which means a lighter fuel load and/or higher speed on the way back.
Again things change. A IIA can climb to 20,000ft about 1.2 minutes faster than a MK I with a Rotal prop. It also has ceiling about 2,000ft higher and about 16-18mph faster, which means that it will be able to fight in the above 20,000ft area a lot better, it will also be able to fight at the lower altitudes a bit better in low gear of the supercharger.

Hopefully, people in the charge will be having these Hurricanes escorting something, not just idly sending them with no purpose. Leaving to the Axis commanders with a decision to make: should we attack the bombers, or the escorting Hurricanes?
Not every Axis fighter was a Bf 109F or a MC.202.

True but some people seem to forget about the MC. 200 and the G. 50
The Italians were not depending only on CR 32s and CR 42s.
The MC 200 as almost as as fast as non Trop Hurricane I and could certainly out climb it, at least until the altitude got on the high teens or low 20s.
The MK I Trop was just about the same speed (adjust for height) and couldn't climb for crap.
On the other hand the MC 200 had crap for range
The G.50 was slightly slower but it was still a dangerous opponent for a Hurricane I Trop.

But NA was different than the BoB. In the BoB both sides were fighting for altitude in most engagements. In NA any bombers (ground attack aircraft) had to fly low in order to spot the targets as there were only a few cities and one railroad and very little paved road to act as markers.
Engagements tended to be much lower than typical BoB engagements although there were exceptions in both theaters

The problem with long campaigns is you don't have to shoot the enemy coming in, that is sort of bonus. If you can shoot down enough of them when they are on the way out they start running out of planes to send on later missions. In NA there were no factories that could affect supply later, there were only existing forces on the ground (and air) and supply dumps. This hurt to loose but it was more replaceable than loosing a factory in the home country.

 

[Engineman]

I have no idea of what else was moved around but I do note that a few Soviet Hurricanes were converted to two seaters with a gunner/observer at the back for artillery spotting.That has to about 120kg extra behind the normal CofG.

It is likely that considerable modification of weight distribution would be required to maintain the C of G. The two seat Spitfire has the front cockpit moved forward, and balance weights are common to fix unsatisfactory weight distribution in aircraft.
I didn't say the Hurricane has handling quirks for nothing, here are some comments by the late Trevor Roche about the Shuttleworth Sea Hurricane:

"So we are safely airborne, but what is she like to fly up and away? Well, classic aircraft that she is, I find that the handling is dominated by the pitch instability to a detrimental effect. Let me explain. All aircraft have varying degrees of pitch stability. If an aircraft is trimmed for a particular speed, and then accelerates, the pilot (if he does not retrim) will have to apply forward pressure to the control column to maintain a level flight path as speed increases. This means that he can feel what the aircraft is doing, and if the nose should drop in flight, the resulting speed increase will then work through the natural stability of the aircraft to bring the pitch attitude back to where it was. Of course, a fighter aircraft should not have too much stability, as control forces become excessive during manoeuvres that produce large speed changes and the pilot must trim rapidly during accelerations to keep such forces manageable. However, an aircraft that is slightly longitudinally unstable, although clearly flyable, requires constant attention from the pilot to keep it pointing where he wants it to go. This is most apparent in the Hurricane during a display when a tight turn is flown and the pilot finds the aircraft tightening into the turn. Here, since the turn is flown at constant power (to conserve engine life), the increased drag causes the speed to drop. Normally, the pilot would expect to have to pull back more on the stick in this case to maintain the turn and to recover from the turn by relaxing the back pressure. However, the Hurricane tightens up and requires a push force to relax the turn."

"So how can I summarise the Sea Hurricane, and in particular her much discussed (amongst collection pilots) handling characteristics? For an airshow pilot flying the aircraft occasionally, the poor longitudinal stability demands a cautious approach when manoeuvring hard close to the ground. However, I would imagine that a fully current Hurricane pilot with a few recent hours on type would soon have been able to turn such characteristics to his advantage in the aggressive combat encounters of the Battle of Britain. As for myself, I can only consider myself fortunate enough to learn this at first hand.

Trevor Roche
May 2003"


Eng

 

[Geoffrey Sinclair]

RAF Figures,
The ranges of fighters are shown as ranges at maximum economic cruising power on the fuel available, after deducting fuel used in 15 minutes at maximum power at sea level. This allowance is for warming up and climbing to operational height.

Under this definition the ranges are climb to operational height over the airfield, then cruise until you run out of fuel.

Mason figures,
The table does say 1,086 miles for the IIc.
Merlin XX fuel consumption
weak mixture, gallons per hour, MS Gear 8 to 20,000 feet, S gear 14 to 30,000 feet, Boost in pounds per square inch.

Gear	MS	MS	MS	S	S	S
RPM	2,650​	2,300​	2,000​	2,650​	2,300​	2,000​
Boost
4​	56​	50​	46​	57​	51​	47​
2​	52​	46​	42​	53​	47​	43​
0​	47​	42​	38​	48​	43​	39​
-2​	42​	37​	34​	43​	39​	35​
-4​	37​	33​	30​	38​	34​	33​

Rich mixture consumption
7 lb/sq in boost, 2,650 rpm, 80 gallons per hour
9 lb/sq in boost, 2,850 rpm, 95 gallons per hour
9 lb/sq in boost, 3,000 rpm, 100 gallons per hour
12 lb/sq in boost, 3,000 rpm, 115 gallons per hour

 

[Engineman]

Notwithstanding the gph consumption figures in post #19 above, it should be appreciated that the best range performance, or air nautical miles per gallon (anmpg), for the Merlin engine was generally achieved by flying with low revs, throttle wide open and relatively high boost. Engine handling wise this was roughly achieved by reducing the revs by the constant speed propeller control, opening the throttle wide and being high enough that the achieved boost was just at the weak mixture limit. This procedure increased range due to the engine operating with minimum throttling and reducing internal losses whilst still having high overall compression. With high altitude, low temperature and TAS/IAS ratio's helped.
Individual aircraft types would have further airframe drag effects and operating weights would limit the altitude, according to the task.
Alec Harvey-Bailey in his great book "The Merlin in Perspective" (RRHT), lists the later bomber ops into Germany flying 1800rpm/7lb boost cruise for best range. The Mosquito had to hold higher rpm to avoid propeller vibration effects and had a good cruise performance carrying a 4000lb cookie to Berlin, cruising at 30,000 feet, full throttle, 2300 rpm, giving 4 lb boost and close to 360mph TAS.

Eng