Spitfire Combat Radius (range) evolution, limitations?

[Jabberwocky]

There wasn't a need for the 20G tank because the MkV had a 29G and the MkIX a 33G behind the seat.

I think the 29 Imperial gallon tank was only fitted to Mk Vs that were flown on ferry flights to Malta. I believe that the local fitters then removed them from the aircraft.

The rear fuselage tank(s) on the Mk IX and Mk XVI were not fitted until very late in the war - from memory the first aircraft with them started to come off production lines in the final quarter of 1944. I believe there was both a 42 Imperial gallon and a 33 Imperial gallon tank for the modified aircraft. Mk XVIs with the cut down rear fuselage had two reart tanks of 33 Imperial gallons each.

 

[ThomasP]

The 29 Impgal rear fuselage ferry tank was tried in one of the Mk I or Mk V PR variants, but one of the pilots commented that it was "almost unflyable" until the tank was empty, and only 2 airframes were so modified.

 

[PAT303]

The 29 Impgal rear fuselage ferry tank was tried in one of the Mk I or Mk V PR variants, but one of the pilots commented that it was "almost unflyable" until the tank was empty, and only 2 airframes were so modified.

Almost unflyable or he couldn't fly it?. Spitfires carried 75g in the rear fuselage with the same restrictions as other aircraft so loaded, they also carried 250/500 and 1000 pound bombs and towed gliders, every report I've read stated the handling was back to normal with 33g in the rear tank.

 

[Shortround6]

We keep forgetting that the MK Vs and earlier used different engines and propellers than the later aircraft, MK VIIs and later used the two stage Merlins (or Griffons) and 4 or 5 bladed propellers.
Center of gravity is going to be different. How much seems to be an unanswered question.
Sticking 210-300lbs of fuel (plus tanks) in the rear fuselage of the planes using lighter engines and propellers might not have worked well.

 

[PAT303]

And these are very good points, there was a lot of changes between the MkII's and MkV's especially in regards to handling but remember the rear tank is burnt off first and mostly gone once at altitude.

 

[Shortround6]

And these are very good points, there was a lot of changes between the MkII's and MkV's especially in regards to handling but remember the rear tank is burnt off first and mostly gone once at altitude.

Then just strap a 30 or 45 gal drop tank under the fuselage and have done with it.
Burn off the fuel in climb and extend the range that way but it doesn't give the range for the desired mission/s.
You need fuel inside the plane to extend the range any significant amount.
How far would 25-30 gallons get a Spitfire V at high-speed cruise burning 36-46gal per hour?
Using 2400rpm and 3 3/4lbs boost needed 50 gal an hour?
2650rpm and 6lbs of boost needed 65-70 gph depending on altitude?

 

[PAT303]

Then just strap a 30 or 45 gal drop tank under the fuselage and have done with it.
Burn off the fuel in climb and extend the range that way but it doesn't give the range for the desired mission/s.
You need fuel inside the plane to extend the range any significant amount.
How far would 25-30 gallons get a Spitfire V at high-speed cruise burning 36-46gal per hour?
Using 2400rpm and 3 3/4lbs boost needed 50 gal an hour?
2650rpm and 6lbs of boost needed 65-70 gph depending on altitude?

In 1941-42 the MkV needed all the help it could get, the rear 29G gives the benefit of a higher cruising speed in airspace protected by 190A's or longer range or loiter time without the drag of the slipper, the slipper was also a reverse aero foil in shape, it was a lash up at best.

 

[Shortround6]

Spend a little time figuring out how to drop the 'slipper' without damaging the aircraft. If you are using the extra fuel for climb and forming up and crossing the channel then dropping it you have nearly full internal when the engagement starts and with the slipper discarded you have no additional drag.

 

[PAT303]

Spend a little time figuring out how to drop the 'slipper' without damaging the aircraft. If you are using the extra fuel for climb and forming up and crossing the channel then dropping it you have nearly full internal when the engagement starts and with the slipper discarded you have no additional drag.

Sounds like a lot of wasted tanks to me, fit the rear tank once and be done with it, they could be clever and make it follow the profile of the back rest of the seat, that way the COG is moved forward plus once empty the tank itself provides additional spaced armor for rounds ranging foward through the rear fuselage.

 

[EwenS]

Spend a little time figuring out how to drop the 'slipper' without damaging the aircraft. If you are using the extra fuel for climb and forming up and crossing the channel then dropping it you have nearly full internal when the engagement starts and with the slipper discarded you have no additional drag.

They did.

Lt Cdr Crosley's description of the setup on the Spitfire V. He was flying Sea Hurricanes from Eagle in 1942 when she was ferrying Spitfires to Malta.

"Amongst the piles of ammunition, wireless sets, pilot's seats, propeller spinners, tail steering arms, wing mats, sweating bodies and noise, we could see several huge slipper-shaped petrol tanks. Some of these were being offered up to the underside of the Spitfire's fuselage — where a bomb might ordinarily be — and the fuel lines were being connected by an invisible, sliding fit. There was only a half-inch gap between the underside of the fuselage and the top surface of the tank, which was all of six feet long by two feet wide. We found that it could hold 90 gallons of 100 octane fuel. This was more than the Spitfire carried in its internal tanks. A closer study of the jettison arrangements showed that a Bowden cable release in the cockpit let go the lifting ring — stressed to three tons breaking strain — in the top surface of the tank. The tank then slid backwards onto two lugs sticking out two inches from the fuselage underside. The nose of the tank then dropped and the airflow forced it downwards and clear of the fuselage underside. The slightest skid, we thought, and the whole thing would come clear of the two lugs, slide back and hit the tail. However , the Spits would now have a range of 400 miles and would allow a fly-off to Malta well before we got to 'bomb alley'."

IIRC "Spitfire the History" has a photo of a test drop of the big 170 gal ferry tank detaching from the aircraft and being flipped down by those hooks.

And someone's model of the setup from elsewhere on this site.

Edit:- diagram of the fittings now found.

 

[ThomasP]

re

Almost unflyable or he couldn't fly it?. Spitfires carried 75g in the rear fuselage with the same restrictions as other aircraft so loaded, they also carried 250/500 and 1000 pound bombs and towed gliders, every report I've read stated the handling was back to normal with 33g in the rear tank.

Shortround6 beat me to it, but to reiterate, the fitting of rear fuselage fuel tanks was made possible by the CG changes allowed by the heavier Merlin 2-stage engines and their associated propellers and structure changes. The 28 Impgal ferry tank in the rear of the V was not intended to be used without the 170 Impgal belly tank which balanced out the change in CG.

Fitting the 29 Impgal ferry tank - by itself - moved the CG past the rearmost limit, and made the aircraft very difficult to control (if it had not been wartime they would not have allowed it) and even in war-time it was not considered worth the problems - to the point that only 2 were ever modified that way. And these were experienced pilots commenting on the handling.

Also, it should be noted that the 29 Impgal ferry tank, as fitted to the Spit Mk V and to the PR variant I mentioned above, was not self-sealing, and could only be accessed and fueled by removing the internal decking and armoured headrest from the rear of the cockpit.

There was a good reason the 29 Impgal ferry tank was not fitted as a general Mod in the Spit Mk V.

 

[PAT303]

re


Shortround6 beat me to it, but to reiterate, the fitting of rear fuselage fuel tanks was made possible by the CG changes allowed by the heavier Merlin 2-stage engines and their associated propellers and structure changes. The 28 Impgal ferry tank in the rear of the V was not intended to be used without the 170 Impgal belly tank which balanced out the change in CG.

Fitting the 29 Impgal ferry tank - by itself - moved the CG past the rearmost limit, and made the aircraft very difficult to control (if it had not been wartime they would not have allowed it) and even in war-time it was not considered worth the problems - to the point that only 2 were ever modified that way. And these were experienced pilots commenting on the handling.

Also, it should be noted that the 29 Impgal ferry tank, as fitted to the Spit Mk V and to the PR variant I mentioned above, was not self-sealing, and could only be accessed and fueled by removing the internal decking and armoured headrest from the rear of the cockpit.

There was a good reason the 29 Impgal ferry tank was not fitted as a general Mod in the Spit Mk V.

Both the Spitfire and Mustang had limitations put on them with rear tanks fitted and like I said change the shape of the tank to move the COG forward, cruising at higher speeds was one of the ways MkV pilots had to combat the FW190, I bet the pilots would happily exchange poor handling for the first 30 minutes if it gave them more speed when needed.

 

[PAT303]

Also, it should be noted that the 29 Impgal ferry tank, as fitted to the Spit Mk V and to the PR variant I mentioned above, was not self-sealing, and could only be accessed and fueled by removing the internal decking and armoured headrest from the rear of the cockpit.

It's seems to be a common thing in these discussions that if something is done, like fitting the 29g tank for Malta that that;s all it can be, there's no reason why the consept can't be continuelly developed. MkIX and MkXVI's had the same rear fusalarge and were fitted with 33+ 33 or 33+42g tanks so I can't see any issue fitting the 29g tank, like I said think outside the square and look at the tank as a positive instead of negative, if didn't have self sealing for Malta because it didn't need it, doesn't mean it can't be fitted, as far as I'm aware the slippers were self sealed either.

 

[Jabberwocky]

Almost unflyable or he couldn't fly it?. Spitfires carried 75g in the rear fuselage with the same restrictions as other aircraft so loaded, they also carried 250/500 and 1000 pound bombs and towed gliders, every report I've read stated the handling was back to normal with 33g in the rear tank.

The Malta tanks were mounted high up in the fuselage, behind the pilot's head. And they were flown in combination with either 170 or 90 gallon slipper tanks. Even with the slipper tanks, the rear tank messed with aircraft's balance and made it unstable.



The A&AEE tested a later (and heavier) Merlin 66 powered Mk IX over Jan/Feb-1945.

There finding was that with the full 75 gallons in the rear tanks the aircraft was "dangerously unsuitable for combat flying" and would also be "dangerous for instrument or formation flying" but not dangerous "for an experienced Spitfire pilot in conditions of good visibility".

There was "markedly longitudinally unstable, stick free, under all conditions of level flight and it was impossible to fly "hands off" for even short periods at normal cruising speeds". If the stick was let go, the aircraft would immediately depart from level flight, and in bumpy air it was considered "most tiring to fly".

In turns, it "tightened up very markedly" and required a "heavy push force" to prevent G's building up to "excessive values".

Dives were neutral, but there was a "definite tendency to diverge in bumps, which had to be constantly checked" and there was a tendency for the nose to rise when speed was reduced.

When fuel burned down to 30 gallons in the rear tanks there was "a noticeable improvement in the
longitudinal behaviour of the aircraft". The aircraft "could be flown level with a reasonable degree of comfort although it was still unstable in phugoid motion and was very "touchy" longitudinally, making trimming difficult".

In turns the aircraft still tightened up, but the effect was "less pronounced" and occurred above 2G at 20,000 ft. It was considered that "if due care were exercised, satisfactory combat manoeuvres could be carried out at this loading without unduly heavy stick forces being involved in checking the build up of normal acceleration".

In dives a "very light push force" as needed to hold the aircraft in a dive.

Overall, even with 30 gallons in the rear tank the aircraft could carry out full combat manoeuvres "without difficulty" but its handling characteristics were "unsatisfactory" and it could "not be considered satisfactory as a fighter by present day standards". Even the 30 gal rear tank loading was "recommended only as an operational necessity".



Overall, not exactly a ringing endorsement of the rear fuselage tanks.

 

[PAT303]

The Malta tanks were mounted high up in the fuselage, behind the pilot's head. And they were flown in combination with either 170 or 90 gallon slipper tanks. Even with the slipper tanks, the rear tank messed with aircraft's balance and made it unstable.



The A&AEE tested a later (and heavier) Merlin 66 powered Mk IX over Jan/Feb-1945.

There finding was that with the full 75 gallons in the rear tanks the aircraft was "dangerously unsuitable for combat flying" and would also be "dangerous for instrument or formation flying" but not dangerous "for an experienced Spitfire pilot in conditions of good visibility".

There was "markedly longitudinally unstable, stick free, under all conditions of level flight and it was impossible to fly "hands off" for even short periods at normal cruising speeds". If the stick was let go, the aircraft would immediately depart from level flight, and in bumpy air it was considered "most tiring to fly".

In turns, it "tightened up very markedly" and required a "heavy push force" to prevent G's building up to "excessive values".

Dives were neutral, but there was a "definite tendency to diverge in bumps, which had to be constantly checked" and there was a tendency for the nose to rise when speed was reduced.

When fuel burned down to 30 gallons in the rear tanks there was "a noticeable improvement in the
longitudinal behaviour of the aircraft". The aircraft "could be flown level with a reasonable degree of comfort although it was still unstable in phugoid motion and was very "touchy" longitudinally, making trimming difficult".

In turns the aircraft still tightened up, but the effect was "less pronounced" and occurred above 2G at 20,000 ft. It was considered that "if due care were exercised, satisfactory combat manoeuvres could be carried out at this loading without unduly heavy stick forces being involved in checking the build up of normal acceleration".

In dives a "very light push force" as needed to hold the aircraft in a dive.

Overall, even with 30 gallons in the rear tank the aircraft could carry out full combat manoeuvres "without difficulty" but its handling characteristics were "unsatisfactory" and it could "not be considered satisfactory as a fighter by present day standards". Even the 30 gal rear tank loading was "recommended only as an operational necessity".



Overall, not exactly a ringing endorsement of the rear fuselage tanks.

Read the A&AEE report on the Mustang, they pretty much reached the same conclusion word for word yet P51's flew millions of miles escorting bombers in the second half of the war.
Quote:
The Aircraft & Armament Experimental Establishment (A&AEE) reported that a full 85-gallon rear fuselage tank on the P-51 Mustang shifted the center of gravity aft, creating severe longitudinal instability and reducing stick force per G. Operational procedures mandated that this tank be emptied before combat to avoid dangerous handling characteristics

 

[drgondog]

Read the A&AEE report on the Mustang, they pretty much reached the same conclusion word for word yet P51's flew millions of miles escorting bombers in the second half of the war.
Quote:
The Aircraft & Armament Experimental Establishment (A&AEE) reported that a full 85-gallon rear fuselage tank on the P-51 Mustang shifted the center of gravity aft, creating severe longitudinal instability and reducing stick force per G. Operational procedures mandated that this tank be emptied before combat to avoid dangerous handling characteristics

Later in the original AAF October-November 1943 flight test report the specific recommendation was to reduce the fuselage tank to 45gal to restore full safe maneuver envelope. SOP post WWII was to fill only to 65-gallons.

 

[Juha3]

The Malta tanks were mounted high up in the fuselage, behind the pilot's head. And they were flown in combination with either 170 or 90 gallon slipper tanks. Even with the slipper tanks, the rear tank messed with aircraft's balance and made it unstable.



The A&AEE tested a later (and heavier) Merlin 66 powered Mk IX over Jan/Feb-1945.

There finding was that with the full 75 gallons in the rear tanks the aircraft was "dangerously unsuitable for combat flying" and would also be "dangerous for instrument or formation flying" but not dangerous "for an experienced Spitfire pilot in conditions of good visibility".

There was "markedly longitudinally unstable, stick free, under all conditions of level flight and it was impossible to fly "hands off" for even short periods at normal cruising speeds". If the stick was let go, the aircraft would immediately depart from level flight, and in bumpy air it was considered "most tiring to fly".

In turns, it "tightened up very markedly" and required a "heavy push force" to prevent G's building up to "excessive values".

Dives were neutral, but there was a "definite tendency to diverge in bumps, which had to be constantly checked" and there was a tendency for the nose to rise when speed was reduced.

When fuel burned down to 30 gallons in the rear tanks there was "a noticeable improvement in the
longitudinal behaviour of the aircraft". The aircraft "could be flown level with a reasonable degree of comfort although it was still unstable in phugoid motion and was very "touchy" longitudinally, making trimming difficult".

In turns the aircraft still tightened up, but the effect was "less pronounced" and occurred above 2G at 20,000 ft. It was considered that "if due care were exercised, satisfactory combat manoeuvres could be carried out at this loading without unduly heavy stick forces being involved in checking the build up of normal acceleration".

In dives a "very light push force" as needed to hold the aircraft in a dive.

Overall, even with 30 gallons in the rear tank the aircraft could carry out full combat manoeuvres "without difficulty" but its handling characteristics were "unsatisfactory" and it could "not be considered satisfactory as a fighter by present day standards". Even the 30 gal rear tank loading was "recommended only as an operational necessity".



Overall, not exactly a ringing endorsement of the rear fuselage tanks.

Hello Jabberwocky, in fact the report (A.&.A.E.E. ref: 5717,a/84/JF) says that the Loading B, i.e. when "if due care were exercised, satisfactory combat manoeuvres could be carried out at this loading without unduly heavy stick forces being involved in checking the build up of normal acceleration", is with 40 ImpGal in the rear tank (74 ImpGal-34 ImpGal used).

 

[MIflyer]

This is from a book by Dr. Alfred Price, "The Spitfire Into Combat" and I recommend it although I think a more accurate title would be something like "Neat Info About the Spitfire That You Probably Have Not Heard About."

This is the second worst example of screwing up a beautiful airplane, the first extra fuel added to the Spitfire. This resulted in a small production run so Spitfires could be made available for longer range missions across the Channel

First a 30 gal non-jettisonable tank was added.

Then a 40 Gal tank was added for the definitive production version.

 

[MIflyer]

Monogram's vintage 1/48 Spitfire IX features a belly mounted drop tank. When I read WingCo J E Johnson's book, "Wing Leader" he mentioned the "Slipper tanks" and I assumed it to be the ones Monogram depicted. In reality the Slipper tanks looked rather like slippers. The Monogram kit was depicting the 90 gallon cylindrical tank that did not appear until 1944.

 

[PAT303]

This is from a book by Dr. Alfred Price, "The Spitfire Into Combat" and I recommend it although I think a more accurate title would be something like "Neat Info About the Spitfire That You Probably Have Not Heard About."

This is the second worst example of screwing up a beautiful airplane, the first extra fuel added to the Spitfire. This resulted in a small production run so Spitfires could be made available for longer range missions across the Channel

First a 30 gal non-jettisonable tank was added.
View attachment 891709
Then a 40 Gal tank was added for the definitive production version.

View attachment 891708

Is this the first worst example?.