Fulmar in 1941/42/43: feasible and/or plausible upgrades?

As I said earlier, the only really feasible solution would be the removal of the "junk in the trunk," AKA remove all the stuff you can (including the extra crew member) from the rear position. It might not gain you much, but other than this option and MAYBE higher grade fuel than what was used (if possible), I don't see the Fleet Air Arm sanctioning new production of an older aircraft. Then again, the Fulmar is mean like the P-40 to plug a hole until better things come along.

And the better thing (the Firefly)* was delayed while the Griffon was pushed aside to concentrate on the the Merlin, Production, upgrading and new versions.



* that was the intention, if the Firefly was really what was needed is another question.

Shortround6 said:

And the better thing (the Firefly)* was delayed while the Griffon was pushed aside to concentrate on the the Merlin, Production, upgrading and new versions.



* that was the intention, if the Firefly was really what was needed is another question.

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I believe the Firefly was Fairey's response to teh request to build Seafires....

Perhaps, but the Air Ministry bought it (the proposal?) and issued a specification for it in the summer of 1940. They had the final choice, not Fairey.

if the Firefly was really what was needed is another question.

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The Firefly was built to N.5/40, which was a reconfiguration of N.8/39 and N.9/39, which were derived from earlier specs for a two-seat fighter and a turret fighter for the FAA. The idea was for a spotter reconnaissance fighter - again, too many requirements compromising a primary role. This was largely the doing of the Air Ministry in 1940, who concluded that the RAF's fighters had differing requirements to the FAA's, so single-seat fighters were a given and that performance differences between a single and two-seat fighter was negligible, therefore a long range recon element was necessary because of the nature of the attacking aircraft being slower bombers at long range attacking the fleet. In reality however, the Firefly gave excellent service as an attack aircraft; even with that big 36.7 litre 1,720 hp Griffon IIB up front, the maximum speed of the Firefly F.I was 316 mph at 14,000 ft - by mid 1943 was far too sluggish for a fighter.

The 'Sea Spitfire' was proposed by the Admiralty as an interim between the Fulmar and N.5/40 (Firefly) because their Lordships wanted a high performance fighter in service as quickly as possible. the idea was put forward on 29 February 1940, but the Air Ministry decided that diverting Spitfire airframes from RAF production was not acceptable, so by end of March 1940, the idea was dropped.

and this must give a substantially higher performance.

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It most certainly does not. Compare with figures for the Firefly - although the Firefly is a heavier machine than the Fulmar, any increase in speed would have been negligible and not enough to match increasing performance in enemy fighters and bombers. Interceptors need to be quick to get to altitude, neither the Firefly nor the Fulmar had very good rates of climb and Ju 88s frequently showed Fulmars attempting to intercept them a clean pair of heels because they were too slow to get up there. Adding a few mph isn't going to change that by much.

Aviation history is littered with designs that on paper had promising performance, but in reality once translated into hardware did not live up to expectations. Again, I turn to the Defiant for an example; when BP offered the Mk.II, its expectations for the aircraft with the Merlin XX fitted were a top speed of 345 mph at 21,000 ft, but found in trials that it could only manage 313 mph at 19,000 ft. The Fulmar would be the same, being bigger and heavier than the Defiant (yes, I know I keep going on about the Daffy, but it does make an interesting comparison with the Fulmar). A more powerful engine in the Fulmar would not offer anywhere near the leap in performance that either Tomo or RCAFson are expecting.

Thank you.

nuuumannn said:

In reality however, the Firefly gave excellent service as an attack aircraft; even with that big 36.7 litre 1,720 hp Griffon IIB up front, the maximum speed of the Firefly F.I was 316 mph at 14,000 ft - by mid 1943 was far too sluggish for a fighter.

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In 1939/40 They were expecting the Griffon to give closer to 2000hp and to ready in 1942. The Fall of France, the summer battles and the BoB meant that Griffon development was stopped for while short term needs were dealt with. quite a few months of development were lost. Perhaps some aircraft programs were resumed without much review as to changed requirements?

Out of curiosity - how fast was the Defiant I at 19000 ft?

tomo pauk said:

Out of curiosity - how fast was the Defiant I at 19000 ft?

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About 297.5 mph (A&AEE).

Speaking of A&AEE tests, the one that is being quoted a lot, I believe, might not be the best representative of the Defiant II's performance.

Indeed the actual test of Defiant II N1551 reports a top speed of 313 mph at 19,400 feet (9 boost). However, looking at the graphs it is apparent that something is wrong. The speed curve in 'M ratio' is fine, showing the same type of gain over a Merlin III as seen in the Spitfire and Hurricane. But the speed curve for 'S ratio' is very anemic. The performance test indicates they had trouble with the engine in M ratio, perhaps a typo? Also the A&AEE had to give the aircraft back to Boulton Paul earlier than they'd have liked.

Now, plotting basic curves from speed points given by the Defiant II 'data sheet' (325 mph at 22,000 feet) - makes the curves fit much more closely with the type of gains we see in the Hurricane and Spitfire when moving from Merlin III to Merlin XX.

In my heart I believe the data sheet to be a better representation of what the Defiant II was capable of.

Was there a speed loss when fitted with the radar aerials?

The 313 mph is quite commonly quoted ( doesn't mean it is right) but perhaps the nightfighter versions were fighting the drag of the black finish and aerials which dropped the speed back to near the day fighter MK I level?

tomo pauk said:

Out of curiosity - how fast was the Defiant I at 19000 ft?

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Hi Tomo, see Defiant K-8620 Level Speeds and R.P.M. at Heights

Shortround6 said:

Was there a speed loss when fitted with the radar aerials?

The 313 mph is quite commonly quoted ( doesn't mean it is right) but perhaps the nightfighter versions were fighting the drag of the black finish and aerials which dropped the speed back to near the day fighter MK I level?

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It appears the speed tests were done on a Defiant II in normal condition.

What to say - many thanks Mike, maybe it's time to give space at your site for the Defiants, Fulmars and Fireflies

Greyman, it goes without saying that I look forward to see any posts containing original documents (in their 'electronic shape', of course), re. ww2 flying hardware, any time you can spare. Thanks for the feedback.

Until someone doesn't post something more professional, here is the graph comparing Merlin 45 (blue line, +16 boost, 1515 HP at 11000 ft max) and Merlin 30 (red line, +12 boost, 1360 HP at 6000 ft max). Not too shabby, 30% more power above 10000 ft:

tomo pauk said:

What to say - many thanks Mike, maybe it's time to give space at your site for the Defiants, Fulmars and Fireflies

Greyman, it goes without saying that I look forward to see any posts containing original documents (in their 'electronic shape', of course), re. ww2 flying hardware, any time you can spare. Thanks for the feedback.

Until someone doesn't post something more professional, here is the graph comparing Merlin 45 (blue line, +16 boost, 1515 HP at 11000 ft max) and Merlin 30 (red line, +12 boost, 1360 HP at 6000 ft max). Not too shabby, 30% more power above 10000 ft:

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Hi, you've made a mistake on the Merlin 45 output curve, as you are using the 12lb boost figure for SL output. With 16lb boost it should look something like this:


and it provides more power than the Merlin 30 at all altitudes.

RCAFson said:

Hi, you've made a mistake on the Merlin 45 output curve, as you are using the 12lb boost figure for SL output. ...

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+12 psi was the SL output, when/where engine is not supplied with any worthwhile ram; the moving airplane/engine should indeed be able to use +16 psi up until 13000 ft (ram present from SL up to the FTH for +16 psi). Here.
The problem with +16psi boost is that it was authorized some time in late 1942? When was the +12 boost authorized?

tomo pauk said:

+12 psi was the SL output, when/where engine is not supplied with any worthwhile ram; the moving airplane/engine should indeed be able to use +16 psi up until 13000 ft (ram present from SL up to the FTH for +16 psi). Here.
The problem with +16psi boost is that it was authorized some time in late 1942? When was the +12 boost authorized?

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The ability of the Merlin 45 to generate 16lb of boost was always possible, even at SL under static conditions, and this could be maintained to the static FTH for that boost level. Ram air permitted 16lb boost to be maintained to a higher altitude than the static rating of the engine, which on the Spitfire V was 13000ft, but on the slower Fulmar it would be about 12000 ft.

16lb boost was authorized in Dec 1941, according to Lovesey.

Based upon our discussions here's my take on a Fulmar III versus the Fulmar II, Martlet IV and Firefly I:



I came up with this performace based upon extending the Fulmar II 12lb curve to 12000ft which gives about 285 mph at ~1400hp and I added another ~12 mph for a Merlin 45 @ 1515hp. IMHO, this would have provided a very useful increase in perfomance.

IMHO, this would have provided a very useful increase in perfomance.

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Compared to what? As a fighter in 1941 - 1943? That still less than 300 mph! Your charts are very pretty, but I don't think you are seeing the big picture.

The chart seems a little bit off. IF I am using the cube law correctly the FUlmar "III" should be good for 291mph at 12,000ft using your assumptions. Since people seem to want to turn the the Fulmar into a higher altitude fighter let's also look at 20,000ft.
Just about all official charts show the speed at altitude falling off in a curve, not a straight line. And even if the Fulmar did to 240mph at 20,000ft ( which rather shows how hopeless things were to begin with as on test a Gladiator did 239.5mph at 20,000ft) the difference in power between the the Merlin 30 and the 45 gets narrower with altitude. The 45 has a good margin but the difference in speed will not be simply moving the Fulmar II line over to correspond to the peak power point a 12,000ft.
Going by the TOmo's chart and having 6000 meters equal 20,000ft. it appears that the Merlin 30 was good for 850hp (give or take) and the Merlin 45 was good for 1100 hp (give or take). The Merlin 45 had 37.7% (?) more power at 12,000ft but at 20,000ft it has 29.4% (?) more power. Ussing the cube law and the 240mph speed at 20,000 ft we wind up with a speed of 261mph at 20,000ft not 273-5mph.

Perhaps minor quibbles but then the Martlet chart is for the Martlet IV which was the worst performing Martlet/Wildcat built (used the same engine as most American Brewster Buffaloes). Granted the UK got about 220 of them but at anywhere above 13,000ft it is going to be about 10-15mph faster than a Fulmar "III".

And that is part of the big picture, Any other Martlet/Wildcat is going to be 20-40mph faster than the Fulmar "III" above the Merlin 45's 16lb boost critical altitude.

Now what is the performance of a Sea Hurricane?

nuuumannn said:

Compared to what? As a fighter in 1941 - 1943? That still less than 300 mph! Your charts are very pretty, but I don't think you are seeing the big picture.

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The Allies had two carrier rated folding wing fighters (with variants) from 1940 to mid 1943, namely the Fulmar and the F4F/Martlet. I have provided the performance of the F4F-4B in the previous chart. A USN comparison of the F4F-4 with the F4F-4B had this to say:

"The F4F-4 was compared to the F4F-4B...the difference in performance was very small, the F4F-4B being slightly superior in speed and climb at low altitudes and the F4F-4 slightly superior at 15000ft and above..."
http://www.wwiiaircraftperformance.org/f4f/f4f-4-02135.pdf

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So "looking at the big picture" I think that it's pretty fair to say that an improved Fulmar would have been very worthwhile as would a variant with the Merlin XX.

Looking at the Firefly performance, we can see that it would have been a pretty hot ship if ready for service in late 41/early 42 as planned, rather than late 1943.

Shortround6 said:

Now what is the performance of a Sea Hurricane?

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Data sheet says:
308 mph at 18,000 feet (+ 6.25 boost)
315 mph at 7,500 feet (+ 16 boost)

Merlin III/eight-Browning version (only Sea Hurricane sheet available).