Edgar Brooks
Senior Airman
Finger trouble; hit 3 instead of 2, sorry.
Long range, high speed Spitfire fighter: the best approach?
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Referring back to the pros and cons of the "elliptical" wing, Shenstone wrote that one of the biggest advantages of the shape was unforeseen.
"…the real advantage of the elliptical wing turned out to be its low induced drag at very high altitudes, such altitudes not having been considered during the design, but realised during the war, helping to keep Spitfire in the front line during rapid development under Joe Smith. The point here is that at great altitudes where the air is thin, the angle of incidence must be increased, resulting in more induced drag. The elliptical wing then becomes important - assuming subsonic flight."
Cheers
Steve
"…the real advantage of the elliptical wing turned out to be its low induced drag at very high altitudes, such altitudes not having been considered during the design, but realised during the war, helping to keep Spitfire in the front line during rapid development under Joe Smith. The point here is that at great altitudes where the air is thin, the angle of incidence must be increased, resulting in more induced drag. The elliptical wing then becomes important - assuming subsonic flight."
Cheers
Steve
You'd need to ask someone like Beverley Shenstone MASC, FRAES, FAIAA, FCASI.
Shenstone started his career at Toronto University where he became the first graduate to be made a Master of Applied Science in Aeronautical Engineering. He worked briefly at the Air Ministry's research laboratory in London before moving to Germany, working with Lippisch (with whom he remained firm friends for the rest of his life). He worked for Junkers in the 1920s. He returned to Britain in 1931 joining Vickers Supermarine throughout the war. He became BEA's chief engineer from 1948 before becoming BOAC's technical director in 1964. He was president of the Royal Aeronautical Society in 1962/3. He remained one of the world's leading aerodynamicists.
If he wrote it I believe it to be so
I have to take his word for I because I am not qualified to debate it.
Cheers
Steve
Shenstone started his career at Toronto University where he became the first graduate to be made a Master of Applied Science in Aeronautical Engineering. He worked briefly at the Air Ministry's research laboratory in London before moving to Germany, working with Lippisch (with whom he remained firm friends for the rest of his life). He worked for Junkers in the 1920s. He returned to Britain in 1931 joining Vickers Supermarine throughout the war. He became BEA's chief engineer from 1948 before becoming BOAC's technical director in 1964. He was president of the Royal Aeronautical Society in 1962/3. He remained one of the world's leading aerodynamicists.
If he wrote it I believe it to be so
I have to take his word for I because I am not qualified to debate it.
Cheers
Steve
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Balljoint
Senior Airman
Just a guess, but generally speaking, it does have reduced frontal area relative to total wing area. Still guessing, at altitude the frontal area may be more important than form drag with the larger total area relative to frontal area also generating more lift per unit frontal area, i.e. a relatively lesser AoA.
OldSkeptic
Senior Airman
- 509
- May 17, 2010
Most German production was for the eastern campaign
Still more than enough, 75 squadrons in all, 50 of them Spitfires.
About a month's production basically.
The idea is that this brings them up, you can't leave planes on the ground.
Park did it to the Germans very successfully later, attacking from Malta.
Hung bombs off Spits, if they stayed on the ground they lost their planes, if they came up they got shot down.
True about dates, a true LR Spit (later) would be invaluable supporting the US bombing campaign and lets BC bomb at day. But a MR Spit Mk V is also invaluable in the late 41/42 period.
They were there, the RAF threw away over 1,000 fighters in the 41/42 'leaning towards the enemy' campaign by Leigh Mallory. They obviously thought they had enough fighters to use them up like that.
But because they didn't have the range to press the Luftwaffe right to their airfields they achieved basically nothing, with a loss rate somewhere in the 4:1 range.
The JG2, 26, etc simply pulled their bases back and only fought when it suited them.
The issue is not whether or not FC should do it, because they actually tried very hard.
The issue is fight more effectively to inflict a proper war of attrition on the Luftwaffe and that, in this case, was simply a question of range.
In other words, what they tried to do was bound to fail unless they increased the range of the Spit.
Now using my fuel model and changing it to the Spit V, instead of the Spit VIII, I get a 300 mile combat range with a 30 gal rear tank and a 45 gal drop tank (you have the option of a 90 gal drop tank too which allows more loiter time in the target area).
More then enough to push the Luftwaffe fighters away (ie if they move their bases further away then they will be out of range of the coast and effectively
useless). If you fit the VIII leading edge tanks to the V, then 400 miles is fine too.
Note that the USAAF fitted 36 gals into the leading edges in their prototype, as opposed to the 26 gals in VIIIs and used a smaller rear tank with 2x62.5 gal drop tanks (same as the Mustang). Apparently it handled quite well.
Note these are conservative figures with takeoff and a climb to 20,000ft and 15 mins combat time (at max power). I also assume that you use all the rear tank straight away, though, at least in MK VIIIs and MK IXs, handling returned to normal at about 20 gal left. Say 10 gals in a Mk V?
If you factor that in and don't run down the rear tank fully, saving the remainder for the return, you can get a bit more (or use it as a reserve of course).
Naturally if you change the mission profile you can get a bit different nums, either a bit better or a bit worse (though to get worse you have to be fairly pessimistic with your assumptions, but certain missions types might do that, eg running at max cruise speed at low altitude all the time). As always, good pre-planning and coordination would be essential.
Note that a fair few MK Vs were fitted with 29 gal rear tanks and used for ferrying them to NA and Malta and so on (along with a 170 gal slipper tank).
All gals are UK ones.
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Glider
Captain
They obviously vary but the Discus Gliders had a wing reducing in three stages resulting in a near elliptical wing to reduce costs. They are excellent gliders with a very good performance with near viceless handling, making it an ideal 'first' high performance glider.
I can confirm that they are a lot of fun to fly and despite being eclipsed in competitions can give a good account of themselves given a bt of luck re conditions.
One problem which would have needed to be sorted on the Mk V with a 30 gal rear tank was stability; Supermarine adopted counter-weights ("bob weights") in the elevator circuit to help solve some problems encountered in 1942 when several Spitfires broke up in flight due to longitudinal instability: as it turned out the problem was caused by bad loading at a squadron level, moving the cg back too far. I would assume that to achieve adequate stability with a 30 gal rear fuselage tank and drop tank not only would it have been wise to introduce the bob weights but also the increased elevator balance area of most Mk IXs and some late Mk VCs. The PR Spitfies could get away with using rear fuselage tanks without too many mods because they were expected to fly straight and level most of the time and only use drastic manœuvres when evading attack.
One effective way to counter Spitfires with fuselage tanks would have been to intercept as far forward as possible, forcing the Spitfire pilots to try manœuvring with the fuselage tanks (say) 2/3rds full. Presumably leading edge tanks could be fitted Mk VII VIIIs because of the extra length and weight of the Merlin 60/70 series which helped counter-balance the extra fuel just ahead of the cg. Leading edge tanks on the Mk Vs, as well as rear fuselage tanks would entail modifications to the Spitfire's rear end. Possibly the larger pointed rudder would have helped?
The Spitfire IX/XVI PNs advise the pilot to take off using the main tanks, then switch to the fuselage tank at 2,000 ft and drain it before switching back to the main tanks. When fitted with the drop tank the policy was to take off on main, switch to fuselage, drain to 30 gal then switch to the drop tank, drain the drop tank, then switch back to rear fuselage, drain it, then back to main tanks. Of curse the pilot had to be careful not to get vapour locks by allowing the tanks to drain completely before switching over. All to keep the cg within limits.
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Do you have a source for that? Murray says German fighter losses on the eastern front were about 120 a month May - September 1942.
They were "coming up". Up to 4,000 sorties a month, depending on RAF activity. That's a similar sortie rate to Luftflotte Reich in the first quarter of 1944, but with a much smaller force. So the problem most definitely wasn't the Luftwaffe staying on the ground.
This is where I can't understand the logic. The RAF lost 1,000 fighters and you want to put more fuel in them and fly further in to enemy territory. That's just going to increase losses further.
They had ample range to reach the German fighter bases in France. Here are JG 26 airfields as of June 1942, with their distance from the British coast:
St. Omer-Wizernes 48 miles
St. Omer-Arques 50 miles
Abbeville-Drucat 65 miles
Wevelgem - 80 miles
All of these were in easy range of FC.
Range is useful if you can't get to the fight. It's useful if you want to bomb targets that are otherwise out of range. Neither applied to the RAF in 1942. They didn't have the numbers to escort deep penetration raids in to Germany, they found all the combat they could possibly want over France.
Firstly, any modifications will of course reduce the numbers of Spitfires available, so the numbers problem gets even worse for the RAF.
Secondly, adding a 30 gallon read tank to the Spitfire V probably wouldn't help much.
The Spitfire IX was just about stable enough with 30 gallons left behind the pilot. But that had a heavier, longer Merlin engine in the front to counteract the extra weight in the back.
If the RAF couldn't force the Luftwaffe away from St Omer, what good would more range do?
That requires structural modifications that would disrupt production. There were large numbers of modifications that could be added to the Spitfire to improve it, but the problem was for most of the war the Spitfire was the only allied fighter that could take on the German fighters on equal terms.
According to Supermarine the US wing leading edge tanks compromised structural strength to an unacceptable degree.
The Spitfire certainly could have its range increased, the various modifications in 1943 and 1944 proved that. But I don't think those modifications are practical in 1942, both for technical reasons and because the RAF were still desperate for more Spitfires (indeed even the USAAF and VVS wanted them as well)
I don't think the modification for a rear tank is worth it for an extra 10 gallons. A better solution would be fit the enlarged forward tank (total 95 gallons) and hang a 90 gallon drop tank underneath.
But that doesn't really solve many problems in 1942. The Luftwaffe in France is still a force capable of flying more than 4,000 sorties a month in defence (about the same as Luftflotte Reich in 1944). It's beyond the capabilies of the RAF to defeat it in 1942.
Edgar Brooks
Senior Airman
Thankfully, the government didn't feel that they should leave these shores undefended, after all dead civilians can't produce, and repair aircraft.
In 10 years 22,00 Spitfires and Seafires were produced, at an average of 42 per week.
The Germans were only interested in Germany; occupied countries could be destroyed as far as they were concerned.
2 x 250lbs, which meant nothing except the odd pinprick
It would appear that you don't listen to what you're told:- the Mk.V HAD to use the 90-gal ferry tank with a tank behind the pilot. The 45-gal was NOT AN OPTION, and, if the under-belly tank was dropped, there was no way to get the fuel out of the fuselage tank, which would make the aircraft increasingly unstable.
Can't be done, since the leading edge "D" boxes, on the V, contained the pipes used for heating the outboard pairs of .303" Brownings.
And when it arrived back here, Farnborough condemned it, since the leading edges had been weakened, so much, to get the tanks in, the airframe was deemed unfit for combat purposes.
I repeat; if the drop tank has gone, the rear tank becomes a waste of space, and aerodynamic liability.
The VIII IX never had fuselage tanks fitted behind the pilot. The Air Ministry wanted them in every Spitfire, but were persuaded against it, so only the XVI had them, and then not until 1945.
Not while Malta was under siege, they didn't; all Spitfires were flown off carriers, with only a 45-gallon tank, and nothing behind the pilot. Any more and they'd never have got off the carrier decks.
swampyankee
Chief Master Sergeant
- 3,979
- Jun 25, 2013
For the laminar flow airfoils available during the WW2-era, normal practice was to assume that the "drag bucket" did not exist, as the required surface finish could not be maintained in service. Even without this, the NACA 6 series airfoils, like the 65A215, have many positive properties. Incidentally, if you want to maintain laminar flow wings in service, completely give up the idea of wing-mounted guns.
Long-range Spitfire:
1) Root plugs, to increase span. Use the added wing volume for fuel tankage.
2) Extend the fuselage about 24 inches for the same reason. Probably the best way to do this would be to add some frames near the c/g.
3) Engine cooling system drag is a major concern on all aircraft. The Mustang probably had the best cooling system design of any aircraft, but the same effect can be achieved with other configurations, that is the belly duct and radiator is not the only solution.
4) All aircraft, especially combat aircraft, have lots of less-than-optimal bits of ducting, venting, doors, seals, etc. These could be cleaned up, but doing so may make servicing more difficult
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Really, when looking the diagrams in Spitfire The History p. 149, it seems odd that with the droptank fuelcock shut and the rear tank fuelcock open there was a need to the droptank being in place. And even more difficult to understand why it had to be 90gal DT, what is wrong with 45gal? And Spit Vs with 29gal rear tank and with 170gal DT flew directly from Gibraltal to Malta in late 42, see for ex Price's The Spitfire Story or Shores' et al Malta: The Spitfire Year.
Juha
As Quill explained carefully in his book the bob-weights were an emergency measure introduced to counter Spitfire Vs breaking up in flight in alarming numbers in 1942, due to poor loading at a unit level. Like most such emergency measures they were a compromise which at least helped curtail a far bigger problem at the expense of some changes in how the elevator felt to the pilot. Once the elevators were redesigned with larger balances the bob-weights could be dropped.
As for the claims about the weights killing more pilots than were saved, does Mike Crosley have any evidence, such as solid figures, to back up his claims?
One big problem with fitting Spitfire Vs with rear fuselage tanks and operating them over Europe: the Fw 190. How could Spitfire Vs with full or half full tanks cope with being attacked by 190s, or even 109F-4s, when the standard variants were so badly outclassed? Doesn't bear thinking about really...
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Edgar Brooks
Senior Airman
I'm afraid that you'd need to address that question to those who wrote the manuals during the war, since they don't go into that sort of detail; going by the drawings, I'd guess (and can only guess) that, in the 90-gal tank, there was enough fuel forward of the CoG to counterbalance the fuel in the rear tank, but not in the 45-gal. Losing the droptank, and having fuel sloshing about behind the pilot, would, in my view, make control extremely difficult, if not impossible. How often did P-51 pilots use, and drop, their extra tanks, before emptying the fuselage tank?
But did any of them use the 29-gal tank with a 45-gal droptank? Somehow I doubt that you'll find any examples, and don't forget that the siege was over, so likelihood of attack, from the African coast was gone.
The only airframe(s) to have the tank were the XVI and (possibly) the F.R.XIV; post-war, pilots were banned from using the rear tank, in fact, there was a ruling that the filler cap should be wired shut.
Today's Tornado's fin is a fuel tank; the fuel, in it, has to be used first, and, if it refuses to feed, pilots have to abort their mission, immediately.
Only his work, as a test pilot, with Boscombe Down, post-war; dead pilots don't return, to give reports, and, as he is now also deceased, it's not possible to ask him anything.
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OldSkeptic
Senior Airman
- 509
- May 17, 2010
Spit IX and IVI (they were identical planes except for the engine) long range fuel system:
Seems smple to me, turn on/off drop tank fuel, turn on/off rear tank fuel.
And here is the conclusions of testing a LF MK IX with a 75 gal rear tanks. Conclusions was that it was cleared for combat with 41 gals left....
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OldSkeptic
Senior Airman
- 509
- May 17, 2010
Even if this true (and I can't find any reference it and it doesn't make intuitive sense since, from a simple safety point of view you would want to be able to isolate different tanks), somehow I don't thing it was beyond British engineering to ...change the fuel switches so you can go from one tank to the other.....
PR versions, based on the k I and Mk V had all sorts of (and combinations of) fuel tanks, anything from 20-30 gals under the pilot's seat, 20-30 gals behind the pilot, plus a whole range of drop tanks depending on the mission requirements.
Somehow they managed to plumb it up so that tanks could be switched....... amazing eh?
The MK V was the most sensitive of all of the Spits to CoG issues ... until they put the bob weight (more accurately, an inertial balance) on and later the revised elevator.
Note bob weights were retained on the pressurised Spits (VII etc), because the friction of the seals on the control lines caused elevator instability.
That is a possibility. But as in P-51, after t/o first use the fuel in the rear tank until it was enough emptied for safe manoeuvring then switch to the DT(s). In early PR Spits with the rear tank, the idea was to use first the fuel from the 29gal rear tank, then to switch to the main tanks.
45gal or 90gal DT were too small for a flight from Gibraltar, so 170gal was the only option. And the siege wasn't over, in fact the danger from LW fighters was highest at that time, Germans had moved to Tunisia with force in early Nov 42 and there was much trafic between Sicily and Tunisia incl. fighters, moving to Tunisia and escorting shipping and transport planes. The Axis didn't surrender until early May 43.
Juha
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OldSkeptic
Senior Airman
- 509
- May 17, 2010
The accident investigation people of the day concluded that the loss of Spits due to wings coming off dropped away after the bob weights (etc) were introduced.
As for the 190, it depend on the time we are talking about.
In mid 41 onwards, when FC first started its 'leaning towards the enemy' approach (and Portal with in incessant opposition to long range fighter became CAS) there were no 190s in any significant numbers (plus they were very buggy at that time). The issue to deal with them was good tactics (naturally once numbers came up they needed the MK IX).
The tactical problem they faced, having very limited range (and no will to change that), was bringing the Luftwaffe to combat in favourable terms. That they couldn't do.
They never attacked the Germans radar (until just before D-Day in fact and that was only thanks to RV Jones*), therefore they could not achieve tactical surprise, they wouldn't or couldn't attack anything the Germans cared about. If they did fighter sweeps the Germans ignored them (as Park did to them in the BoB). If they sent bombers in they could only go to very close targets.
In fact JG2 26 simply could have done nothing at all if they wanted. But fighter pilots being fighter pilots they did engage .. but only where and when they could get their top pilots lots of gongs for easy kills.
The 190s were a shock, even though they were altitude limited, but because, to bring them up, they sent in escorted bombers they were at relatively low altitudes where the 190 shone.
Their own escort tactics were poor, placing, initially undue numbers of plane in close support. Took far too long to work out the correct pattern of close (but not too close) high along with a forward sweep.
It was if everything they had seen done wrong by the Luftwaffe in the BoB they were determined to copy, with similar results.
Park showed the way when he went on the offensive from Malta into Sicily (etc). Increased range with drop tanks, mixed pure fighters with Spits carrying bombs (and they dropped the racks with the bombs, thus turning them back into pure fighters again, the racks could cost anything up top 20mph in speed).
Then he used the Spits as very successful dive bombers, which though they only had a small bomb load (2x250lb)) they were (with training) very accurate.
So if the Luftwaffe stayed on the ground they would lose planes, therefore their fighters would have to come up and at a tactical disadvantage.
The proof is in the pudding, so to speak, the Luftwaffe basically abandoned Sicily before the landings.
Note that the Spit made a very good dive bomber capable of high angle, high G attacks. Its low wing loading, high G rating plus that good elevator authority at speed and light weight meant that it could attacks at very steep angles and still pull out. Other heavier fighter bombers (eg the Typhoon and P-47) had to attack at shallower angles and pull out earlier because they 'mushed' so much.
A small bomb aimed accurately is far more effective than a larger one that is inaccurate.
Now to do a successful campaign in 41 and 42 there were only 2 targets that were guaranteed to get the Luftwaffe fighters up, whatever their tactical position:
(1) Sending in bombers to attack the U-Boat pens being built in the Bay of Biscay coast.
(2) Attacking their airfields. Note that could have been (say) some of their bomber airfields.
Both cases depended on:
(1) Taking out their radar sites.
(2) Longer ranged Spits.
Target (1) was completely ignored (despite RN and Coastal Command pleadings) by Portal and dependency (2) was completely ignored (more accurately fought against for years, Oct 43 and still fighting against it) by Portal.
And since he was the boss, well that's why we got that whole sorry fiasco in 41 and 42.
And lots of JG2 26 boys got lots of gongs for shooting down strategically and tactically disadvantaged FC pilots (plus a fair few BC ones too).
That old saying "Lions led by donkeys' comes to mind....
* I lobe this story, Jones had been building up maps of every German radar station throughout Europe. BC was not interested in the least, in a famous comment, after Jones had laid out to Harris the complete German radar defence network he commented "well that shows we're hurting them", as Jones commented his thoughts were "more likely that will hurt you".
Anyway he had been tracking and documenting and arranging all sorts of things (resistance spying, photo recon, signals,et al) to build a compete map of the German coastal radar network.
In March 44 he went to Tedder (since no one had contacted him about it and there were precisely zero anti-radar plans by the allies) about it through unofficial channels and finally someone from SHAFE turned up. The rest as they say was history.
Glider
Captain
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