1000-1200 HP: long range fighter vs. interceptor?

Shortround6 said:

How the plane was supposed to pick up over 40mph by deleting the turret has never been really explained.

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Sholto-Douglas was told by someone (during efforts to remove Dowding) that removing a Blenheim's mid upper turret would increase its speed by a more modest 15 mph, though there is no clear evidence for this. This, Douglas suggested, in combination with 100 octane fuel, for which its engines were not modified and which was anyway reserved for Spitfire and Hurricane aircraft at this time, would enable it as a night fighter.

Douglas, like armchair Air Marshalls today, glossed over the details of the conversion, its effect on the aircraft's CoG etc, all points raised by Dowding in his reply.

This is why places like Boscombe Down exist!

Cheers

Steve

There is a problem about max speed achieved by Defiant II. The 315 mph was achieved at 16500 ft, a figure that might correspond with Merlin III full throttle heigh (plus a little ram), but not with Merlin XX, that have had 2nd gear FTH at 18500 ft on +9 lbs boost. The maximum speed would be at altitude higher than that, due to ram, as attested by Hurricane II and P-40F. They were fastest at 20-22000 ft.
Of course, a speed graph for the Daffy II would be good to have.
At +12 lbs boost, the Defiant I was capable for 310 mph at 10000 ft.

Well, there could be discrepancies due to the airborne radar antenna and perhaps the the flatblack finish. But nobody is claiming 330-340mph speeds for a Defiant II and the idea that a Defiant II (single seater) would be 20mph or more faster than than a Hurricane II with the same engine takes a lot of faith.

stona said:

Sholto-Douglas was told by someone (during efforts to remove Dowding) that removing a Blenheim's mid upper turret would increase its speed by a more modest 15 mph, though there is no clear evidence for this. This, Douglas suggested, in combination with 100 octane fuel, for which its engines were not modified and which was anyway reserved for Spitfire and Hurricane aircraft at this time, would enable it as a night fighter.

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Evidence was probably from A&AEE tests of Blenheim L1348 where they tested just that modification (among other things).

As far as I can tell, the Blenheim I's Mercury VIIIs required modification to allow the jump from +5 to +9 boost, but the Blenheim IV's Mercury XVs were good to go from the start. I have no hard data but reading correspondence and publications from the time, it seems to me that the Blenheim was using 100 octane fuel before any other plane in British service.

Thanks Tomo, for posting those. Very nice.

The main trouble I have with single seat Defiant's is that the 360mph speed was an estimate, that doesn't seem to have anything to back it up. The original Defiant was flown as single seater, with the turret position faired over but not out.

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It was; the prototype was never altered in any way except to fair over the turret. The only way the Defiant could have been able to reach such speeds is if the internal structure is lightened since the bulk of the turret is not required. This doesn't mean it would not have had a creditable performance if such alterations were made. With such measures it would have been able to match at least the Hurricane, if not better the Spit. It is worth remembering that in the mid 1930s, a service fighter that could reach, let alone better 300 mph was considered fast.

The Defiant was quite advanced structurally for a mid 1930s design, yes it had a thick wing, but BP undertook measures to reduce skin friction as much as possible. The innovations carried out on it might not be so new to us today, but at the time were very advanced and in some cases had not been done in the British industry before. Its entire exterior cladding was fastened with countersunk rivets and each panel was carefully trimmed to produce as clean a fit as possible. Its undercarriage was completely enclosed, with fairings fitted to the gear doors to cover gaps and produce a clean fit. On production aircraft the small 'D' shaped door that enclosed the wheel was removed, presumably to save weight. Early on, Defiants, just like Spitfires, were also polished to keep their exterior clean (this is not a new idea), although photos of war weary aircraft show a decidedly rough finish.

Construction wise the Defiant was very strong and toughly built and was designed for ease of construction and maintenance in mind; it was simpler to build than other British fighters and was designed as modular sub assembles that would be built then mated together. The wing centre section contained the radiator/oil cooler assy and u/carriage, to which would be fitted the outer wings, which contained fuel tanks. The centre fuse was from the firewall to aft of the turret, with the rear fusel bolting on to that, to which was fitted the empennage, tailwheel and radio equipment. Its wing comprised a two spar arrangement; its main spar was comprised two 'T' sectioned spar caps with corrugated webs between. The rear spar was the same, but with 'L' section spar caps.

Defiants were also modified for the carriage of external tanks, although these were Mk.IIs; the Daffy was also considered for the Army Co-op role and were fitted with pylons for the carriage of external stores. Hard points were built into its wings.

There's no reason that a modified Daffy single-seater couldn't be a good long range escort. The airframe is big enough and it doesn't encroach on existing production plans.

Whatever long range fighter is hypothetically developed it won't be from one of the interceptor fighters developed by the British in the 1930s.

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Of course, you are absolutely right, Steve. Why would the RAF interrupt its existing plans and requirements for something it did not perceive it needed? Despite Supermarine carrying out modifications to the Spitfire by fitting external tanks, no official requirement was issued for such a modification, nor was a long range Spitfire even set in concrete as a need for the RAF. These were experiments carried out by Supermarine at the behest of senior staff who had discussed the idea, but no official statement was issued for production of such a thing.

Oh yes they were. Those photos I posed showed that 602 squadron was picked to trail them and 30 aircraft were suppose dot be fitted, in June 1940. Then the BoB happened and obviously it was shelved.
Then Dowding was given the boot and the whole idea collapsed ... basically forever.

stona said:

A

Sholto Douglas nicely summed up the British defensive mind set and definition of air superiority in 1938.

"Our objective is not to prevent enemy bombers reaching their objectives, though it would be nice if we could, but to cause a high casualty rate among enemy bombers, with the result that the attack will dwindle rapidly to bearable proportions."

No mention of fighters, and in December 1940, after the BoB he reiterated this position.

"The best, if only way of achieving air superiority is to shoot down a large proportion of enemy bombers every time they come over.........I would rather shoot down fifty of the enemy bombers after they had reached their objective than shoot down only ten before they do so."

The Royal Navy lowered the bar. They were content to break up enemy formations thus preventing accurate bombing of their ships. This the FAA did rather well prior to the arrival of the better equipped and better trained Luftwaffe in the Mediterranean.

Cheers
Steve

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Which Park totally disagreed with in the BoB or later. His idea was to stop the bombers dropping AND shoot them down.
When he took charge in Malta he did it by separate squadrons, one for the escorts, one straight at (head on attack) at the bombers and the other (if available) to sweep up the remaining, now split up and retreating, bombers.
The bombing on Malta ended real fast... The he went on the attack and was the first to put bombs on Spits (I always until recently thought North Africa did the first bomb carrying Spits but I was wrong) including dropping the racks which meant performance was the same.
He did that to get the Luftwaffe up, if they didn't come up the Spits bombed their airfields. Mixed groups of bomb carrying and non carrying ones of course.

The Malta defence was hampered by that idea, plus they used 'big wings' (later on when they had enough Spits), which as usual took too long to form up and were vulnerable to fighter attacks.

Park's idea was strategically, tactically and psychologically sound.
On the attack, even if you are taking heavy losses, if you believe you are making an impact then you will carry on.
If the bombers dropped their bombs (roughly) on target, even though they took bad losses, then they will probably continue on, at least for good while.

Human psychology being what it is, the most optimistic interpretation tends to hold for a long time (look at Bomber Command and the USAAF).
"Yes we are taking bad losses, but we are bombing the heck out of them, so lets continue, they will fold before we do" ... and that sort of thing (cognitive dissonance is the syndrome and no military organisation wants to think that all those lives expended and resources used are all for nothing).

But if they are not even doing that, they will give up far faster, since they are taking losses for zero achievement (unless they counted killing lots of fish as an achievement).

Greyman said:

Evidence was probably from A&AEE tests of Blenheim L1348 where they tested just that modification (among other things).

As far as I can tell, the Blenheim I's Mercury VIIIs required modification to allow the jump from +5 to +9 boost, but the Blenheim IV's Mercury XVs were good to go from the start. I have no hard data but reading correspondence and publications from the time, it seems to me that the Blenheim was using 100 octane fuel before any other plane in British service.

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Roy Feddan (chief design engineer for Bristol engines) and F.R Banks were agitating for 100 Octane fuel to be adopted throughout the RAF as early as 1937 fuel consumption | compression ratio | fuel | 1937 | 0077 | Flight Archive , and Feddan designed the Mercury XV, and all later Bristol engines to use 100 Octane from the outset. Rolls-Royce displayed Merlins using 100 Octane fuel at the 1938 Paris Salon:

Paris Salon 1938 | 3453 | Flight Archive :



View attachment Flight_March28_1940_Fighter_Station.pdf

Re stopping the bombers before they dropped their bombs the RAF went to considerable effort to making this happen. The pre war spec for a four cannon armed fighter had this task in mind.

Glider said:

Re stopping the bombers before they dropped their bombs the RAF went to considerable effort to making this happen. The pre war spec for a four cannon armed fighter had this task in mind.

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Exactly. That was the Dowding 'idea' and the Park tactics. Hence the 'eight gun fighter'. the performance, the C&C system and all the rest..

A question: anybody knows how much fuel the Martin-Baker MB-2 fighter was carrying?

OldSkeptic said:

Oh yes they were. Those photos I posed showed that 602 squadron was picked to trail them and 30 aircraft were suppose dot be fitted, in June 1940. Then the BoB happened and obviously it was shelved.
Then Dowding was given the boot and the whole idea collapsed ... basically forever.

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You have posted images from "Spitfire the History" so you obviously have a copy.
Fighter Command received this from the Air Ministry.

"As a result of investigations by the Air Ministry, it has been decided to manufacture 100 wing tanks of 29 gallon capacity. This will provide just over 200 miles additional range at most economical cruising speed. The tanks will be self sealing and Supermarine estimate that the tank should not result in a loss of more than 3 miles per hour at maximum speed. The first tank will be available by about the middle of June and you will decide which squadrons will be fitted with the tank."

Dowding replied on 17th June.

"Arrangements are being made to fit 602 Squadron with the long range tank in the first instance. The installation, however, cannot be fitted in conjunction with the Hispano cannon Spitfire, and owing to the extensive nature of the modification it is necessary to confine the fitting of Hispano guns to new production aircraft and the present intention is to produce 30 of this aircraft type. The tank can be fitted to standard Spitfires retrospectively."

There are problems apart from the incompatibility with cannon armament. The reduction in speed was not 3 mph but 20+mph, Supermarine was quite wrong. The tank installation added 440 lbs to the all up weight of the aeroplane with all the penalties that incurred. The aircraft was difficult to fly at high speed with the tank fitted and it's handling characteristics were described, by Boscombe Down as "poor". It required almost constant aileron input, tightened in turn to port and if the control column was pulled back the port wing dropped throwing the aircraft into a spiral dive. I've already mentioned the heavy ailerons and need for "considerable force" to hold up the port wing at speed. Of course you could always fly around slowly (like your tired old puffers) but that rather negates the advantages the Spitfire had. What is the point of getting to a fight if in doing so you have thrown away some of your advantages in that fight?
An aeroplane that the test pilots of Boscombe Down struggled with was not suitable for squadron service.
This why the system was shelved.

Metal ailerons were first tested in November 1940. In September 1941 an under wing tank was tested on a Spitfire IIA and the handling was now found to be acceptable. The degradation in performance compared with a standard Spitfire IIA (already slower than the lightly equipped early Mk Is due to the extra weight of the Merlin XX, IFF set, armour and the drag of the IFF antennae) I have already demonstrated from the Boscombe Down reports on P7280 and P8036.
The Spitfire IIs performance was reduced by the fitting of the wing tank to something barely better than a Merlin XX powered Hurricane II.
This is why the system only saw limited service with a few squadrons.

It doesn't matter what Park thought was the best method of dealing with bombers. His bosses at the Air Ministry shared Douglas' view both prior to and after the BoB. Park was an Air Vice Marshall commanding one Group of Fighter Command. He did not make nor implement British air defence policy. He had some latitude of action in a tactical sense. He carried out his orders to the best of his ability which, luckily for all of us, was considerable.

Cheers

Steve

Hello, Steve,

The degradation in performance compared with a standard Spitfire IIA (already slower than the lightly equipped early Mk Is due to the extra weight of the Merlin XX, IFF set, armour and the drag of the IFF antennae) I

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Merlin XII was aboard, not the XX. Unfortunately, if I may add.

tomo pauk said:

Hello, Steve,
Merlin XII was aboard, not the XX. Unfortunately, if I may add.

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Correct. I misread or mistyped. The rest still stands though.
Thanks
Steve

Indeed, as does wast majority of what you post here.

Greyman said:

Evidence was probably from A&AEE tests of Blenheim L1348 where they tested just that modification (among other things).

As far as I can tell, the Blenheim I's Mercury VIIIs required modification to allow the jump from +5 to +9 boost, but the Blenheim IV's Mercury XVs were good to go from the start. I have no hard data but reading correspondence and publications from the time, it seems to me that the Blenheim was using 100 octane fuel before any other plane in British service.

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Dowding asked, specifically, on 7th September.

"How long would it take to remove a Blemheim turret and install a blister?"

"What effect would this have on its [Benheim] centre of gravity?"

"How much time would it take to modify the Blenheim's Mercury engines to take the improved fuel?"

The version of Blemheim and engines are not specified. If the tests had been carried out at this time Dowding was clearly not aware of them.

The Blenheim, or some of them, may have been able to use 100 octane fuel but they weren't at this time as it was reserved for Spitfires and Hurricanes

It is also relevant that earlier, on 28th August, Dowding had written that he considered the Beaufighter to be Britain's only realistic hope of an effective night fighter. All this was going on at the height of the day battle.

Cheers

Steve

Glider said:

Re stopping the bombers before they dropped their bombs the RAF went to considerable effort to making this happen. The pre war spec for a four cannon armed fighter had this task in mind.

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The pre-war specification for an 8 gun fighter was designed to shoot down bombers. When exactly this would happen has nothing to do with the specification.

We owe the eight gun fighter to Squadron Leader Ralph Sorley of the DTD who worked out the need for this weight of fire in 1933/4. He passed over the cannon armament as he considered it "super sensitive" to rigidity of mounting and difficult to mount in wings.

In April 1935 the AM Specification called for "as many guns as possible" which was a bit vague, despite a suggestion of eight. The .303 Browning was the machine gun now envisaged.

F7./35 did require a fighter armed with four 20mm cannon. This resulted in the twin engine "Whirlwind". The AM didn't think it was feasible in a single engine type and Hawker's formal submission of a cannon armed Hurricane in 1936, which would have somewhat pedestrian performance, both confirmed this and sowed the seeds for something better.
It wasn't until 3rd March 1938 that Hawker received a contract for four prototypes, built to Specification F.18/37, which eventually led to the "Typhoon" and then "Tempest".

It would always be ideal to intercept bombers before they bombed, as Douglas conceded, but this was not practically possible. Official figures are hard to find, but reference to memoirs and individual pilot's log books would indicate that roughly 6 out of 10 sector controlled interceptions were successful.
All Douglas wanted to do was shoot down as many bombers as possible, whenever that was possible, which seems eminently sensible to me.

Park's sensible plan to engage primarily bombers and not tangle with escorts (with either Spitfires or Hurricanes) was of course at the mercy of German tactics. One of the inadvertent effects of the Luftwaffe's change in tactics around 24th August was that it became virtually impossible to avoid the escort fighters, even though they were now flying in a less advantageous state.

The MB.2 had a fuel capacity of 83 gallons stored in two fuselage tanks.

Cheers

Steve

Air Publication 1530B - September 1939 (Revised October 1939)
Pilot's Notes
The Blenheim IV Aeroplane
Two Mercury XV Engines



Dowding had a lot on his plate, and I'm sure he wasn't aware of every single wheeling and dealing in the RAF/RAE/A&AEE/etc.

stona said:

The Blenheim, or some of them, may have been able to use 100 octane fuel but they weren't at this time as it was reserved for Spitfires and Hurricanes.

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Do you have evidence for this?

Some great documents from wwiiaircraftperformance.org
http://www.wwiiaircraftperformance.org/hurricane/AASF-Fuel.pdf
http://www.wwiiaircraftperformance.org/hurricane/RAF-Component-15may40.pdf

"Merlin XII was aboard, not the XX. Unfortunately, if I may add."

I think you just answered your own question.

If the Merlin XII isn't good enough at 1175hp for take-off and 1140hp at 14,750ft (at 9lbs boost) in the low drag (for the time) Spitfire carrying 440lbs(200kf) of guns and ammo, then what kind of engine or airplane do you need?

Having a plane that is fast isn't the answer. It has to be able to fight even if not tight dog fight in the traditional sense. The Bf 110 was faster than the Hurricane I and that didn't work out so well.

The MB.2 is a dead end. The Defiant is a dead end. ANY existing fighter with under 1200hp is a dead end. And a new design has to give up what? protection? Armament?

For an escort fighter the British needed plane that could fight the 109 on near equal terms and do it about 300 miles from it's bases just to hit the Ruhr. Depending on route home (Essen to Burge=165miles, Cologne to Dunkirk is 200miles) a considerable period of time/distance is spent in enemy controlled air-space which means cruise speed must be kept high.

For the Germans it is 114 miles from London to Derby (add to radius) and 178 miles from London to Liverpool, forget Northern Ireland. 258 miles from Arras to Derby. SO the Germans have the same problem. The need to be able to beat the Hurricane and come close to the Spitfire but do it at a radius 100-175 miles further than they were doing it. It is 67 miles from London to Dover.

These distances just get you out of AA range, pursuing fighters are another matter.