Why the heck did they design it that way?

[michael rauls]

Seems like I hit a nerve here. That was not my intent.
To address your points though: The Mustang Mk.I actually should have been faster at low altitude but just could not break the 400 MPH mark at any altitude. The Mk.II P-51A could. I believe most of the very low production numbers served in CBI but I didn't realise we were restricting discussions to Europe.
Never said the Allison Mustang or Mustang in general was better than everything else.
The main point I was trying to make was that although the Spitfire was certainly a great fighter, it was relatively slow for the amount of engine power installed and the only other common aircraft with similar model engines was the P-51B/D. If you think about it, the Merlin Mustang had about the same speed advantage over the Spitfire Mk.IX as the Allison Mustang had over the P-40....

As I see it, in general, everyone has some kind of unusual feature in their fighter design: The Mid-Engine in P-39, Thin Elliptical Wings in Spitfire, Landing Gear attached to the Fuselage for Me 109. Sometimes the trade off worked and some times it did not.

Just to throw another Aeroplane into the pot: What do you all think of the relatively small wings on the Focke-Wulf 190 series?

- Ivan.

I've wondered if the small wings on the FW190 were an intentional( an apparently successful) attempt to create a higher roll rate.

 

[Ivan1GFP]

Yes thats one of the things that has always been kinda frustrating for me to read that for many types just as improvements in hp came along so would a wheelbarrow full of new required wieght
keeping them mired in never ending mediocre performance mud so to speak. Most of these things like self sealing fuel tanks certainly warranted the soaking up of new hp. However, although I can't remember any particular examples right now I reamember thinking of a couple weight additions" did they really need that extra 300 lbs for that". That might also be an interesting discussion i.e. modifications done to aircraft negatively affecting performance that ended up giving little if any benefit but i guess that would be another topic for another thread................Hmmmmm

Hello Michael Rauls,
A really great example of this kind of degeneration would be the P-39 Airacobra.
As designed, and up to the P-39C, it carried 170 Gallons of fuel which isn't bad for an interceptor.
Armament, armour, and other military equipment would add about 1000 pounds to the design weight.
Add in some self sealing fuel bags and fuel load is down to 120 Gallons in the same space.
Weight escalations elsewhere (I believe mostly in the Engine and Supercharger) and an apparent wish to keep the aircraft weight low would reduce the fuel load to only 87 Gallons by the time the P-39N came along. That is barely half of what it started with....

Perhaps the small wings on the FW 190 helped the roll rate and perhaps they did not. Even with the longer wings of he Ta 152 series, the roll rate was still quite good.

- Ivan.

 

[michael rauls]

Hello Michael Rauls,
A really great example of this kind of degeneration would be the P-39 Airacobra.
As designed, and up to the P-39C, it carried 170 Gallons of fuel which isn't bad for an interceptor.
Armament, armour, and other military equipment would add about 1000 pounds to the design weight.
Add in some self sealing fuel bags and fuel load is down to 120 Gallons in the same space.
Weight escalations elsewhere (I believe mostly in the Engine and Supercharger) and an apparent wish to keep the aircraft weight low would reduce the fuel load to only 87 Gallons by the time the P-39N came along. That is barely half of what it started with....

Perhaps the small wings on the FW 190 helped the roll rate and perhaps they did not. Even with the longer wings of he Ta 152 series, the roll rate was still quite good.

- Ivan.

Yes good example. I would think the f4f/fm2 would be another prime example of this. My thinking about the small wings on the Fw190/ roll rate, with my limited understanding of aerodynamics, was that all other things being equal less wing area would create less resistance and therefore a quicker roll rate. At least to start. I could be wrong( often am) but didn't aircraft with a higher wing loading for about the same size aircraft generally have better roll rates?

 

[michael rauls]

Didn't the D have long wings but thin so still a fairly small area?

 

[Shortround6]

No, it was willingly sacrificed in the workings of the Operational Requirements Committee.
Everything about designing a fighter is a compromise, and in the quest for speed and firepower it was endurance that was one of the the first to be compromised.
Cheers
Steve
Edit: Wasn't fuel capacity/endurance further reduced when Supermarine agreed to fit eight guns? (I can't remember). The requirement to lift a bomb definitely went, in lieue of more guns.

You may have actual documents/letters/memos, etc. I certainly do not.
I am just pointing out that the Hurricane and Spitfire, with internal fuel, were going to have roughly the same endurance (not necessarily range) as the biplanes they were replacing as their bigger engine would use more fuel per hour. They may have bit more range as their cruising speed would be higher than the biplanes cruising speed so distance covered per hour would be different but not be enough to call for or allow a difference in tactics or differences in patrol/intercept areas or distances.

the "standard" bomb load of most British fighters of the 20s and early 30s seems to have been four 20lb bombs? Essentially unchanged since the S.E.5 if not before. Since the monoplanes with fixed pitch props were cutting it a bit close in take-off and landing distances without hanging little bombs under them it seems sensible to delete them.

 

[michael rauls]

By thin i meant fron to back.

 

[stona]

The Spitfire was originally supposed to lift a 250 lb bomb.
Obviously later Marks could, and some, but the capability was deleted from the Mk I.
Cheers
Steve

 

[Shortround6]

Thank you, I had not seen that before.

 

[pbehn]

Seems like I hit a nerve here. That was not my intent.
To address your points though: The Mustang Mk.I actually should have been faster at low altitude but just could not break the 400 MPH mark at any altitude. The Mk.II P-51A could. I believe most of the very low production numbers served in CBI but I didn't realise we were restricting discussions to Europe.
Never said the Allison Mustang or Mustang in general was better than everything else.
The main point I was trying to make was that although the Spitfire was certainly a great fighter, it was relatively slow for the amount of engine power installed and the only other common aircraft with similar model engines was the P-51B/D. If you think about it, the Merlin Mustang had about the same speed advantage over the Spitfire Mk.IX as the Allison Mustang had over the P-40....

As I see it, in general, everyone has some kind of unusual feature in their fighter design: The Mid-Engine in P-39, Thin Elliptical Wings in Spitfire, Landing Gear attached to the Fuselage for Me 109. Sometimes the trade off worked and some times it did not.

Just to throw another Aeroplane into the pot: What do you all think of the relatively small wings on the Focke-Wulf 190 series?

- Ivan.

You seem to miss my point, the P-51 and Spitfire were both British aircraft until the US military took an interest, even then they were both allied aircraft. It makes no sense to make the Spitfire compete in range when you actually have the Mustang and also the Typhoon then Tempest. The Spitfire Mk XIV first started in service in Oct 1943.

 

[michael rauls]

You seem to miss my point, the P-51 and Spitfire were both British aircraft until the US military took an interest, even then they were both allied aircraft. It makes no sense to make the Spitfire compete in range when you actually have the Mustang and also the Typhoon then Tempest. The Spitfire Mk XIV first started in service in Oct 1943.

Verry good point that made me realize I all to often view aircraft, especially allied aircraft, in terms of their individual atributes and or shortcomings in certain areas and not how they fit into the larger scheme of things.

 

[pbehn]

Verry good point that made me realize I all to often view aircraft, especially allied aircraft, in terms of their individual atributes and or shortcomings in certain areas and not how they fit into the larger scheme of things.

US pilots were flying Spitfires in UK until replaced by more suitable US aircraft, the RAF operated P-51B/C and D sometimes assisting on bomber escort, US P-51s also escorted Mosquitos on some bombing missions. It was an allied effort, particularly in photo recon, it made no sense to be anything else.

 

[buffnut453]

US pilots were flying Spitfires in UK until replaced by more suitable US aircraft, the RAF operated P-51B/C and D sometimes assisting on bomber escort, US P-51s also escorted Mosquitos on some bombing missions. It was an allied effort, particularly in photo recon, it made no sense to be anything else.

You raise a good point. Equally, AFAIK, the USAAF wasn't providing fighter defences for the UK mainland which, again, demonstrates that this was an integrated Allied effort.

 

[Shortround6]

We have a lot of things going on in this discussion.

The Mustang I may never have been designed/intended as a long range airplane in the way we think now.

It was also four years newer (at least) than either the Spitfire or the P-40 in knowledge.
The first production P-40 (no letter) flew only 1 month before the British OK'ed the preliminary drawings for the Mustang I. NAA was pitching a better P-40, not a better Spitfire. A P-40 (no letter) without self sealing tanks held 180 gallons of fuel. This went down to 160 gallons on the first rudimentary self sealing tanks and down even further later. And please note that the performance figures for the early P-40 was based on 120 gallons US of fuel (99 Imp gal)
http://www.wwiiaircraftperformance.org/P-40/P-40_Official_Summary_of_Characteristics.pdf

Not with the rear tank full.

The initial Mustang I design may have been done accordingly. Performance estimates done on something less than full tank/s. with the full tanks being available for deploying or transfers? spring of 1940 is before drop tanks were common in either the US or UK. Things change fast in wartime and by the time they were delivered and issued they may have decided to take the hit to speed/climb and fill the tanks.

As far as the Typhoon goes, I am not at all sure that it was designed as a "long range" fighter. Design work starting in 1937/38 and 154imp gallons (in what became self sealing tanks) really doesn't provide a lot of range/endurance for a 2000hp engine in a fighter the size of the Typhoon. Pilot's manual calls for about 4.5 miles to gallon at 230mph IAS at 15,000ft when clean. Going to 280mph IAS at 15,000ft clean drops the mileage to about 3.5 miles per gallon.

It may very well have gone further than a Spitfire but it was hardly going to be a an escort fighter for bombers attacking Germany from the UK in 1940-41(planning and initial development).

 

[pbehn]

Another point to consider in design is home territory, in England it is impossible to be further than 72 miles from the sea, I believe it is slightly more in the USA. Even in peace time how many times would a Spitfire have to refuel flying coast to coast? In UK if high enough you can frequently see both coasts.

 

[Ivan1GFP]

You seem to miss my point, the P-51 and Spitfire were both British aircraft until the US military took an interest, even then they were both allied aircraft. It makes no sense to make the Spitfire compete in range when you actually have the Mustang and also the Typhoon then Tempest. The Spitfire Mk XIV first started in service in Oct 1943.

Hello Pbehn,
This was not intended as a Spitfire versus Mustang discussion or even a comparison of the two aircraft other than for the simple characteristic of speed.
If you look at the original post I was replying to, you will note that it was a discussion of the characteristics of the Spitfire.
Why the heck did they design it that way?

While I agreed with most of what was stated, two of the characteristics did not seem correct to me.
I chose to address the "at least competitive speed" comment which I believe was not correct.
Is there another aircraft with a comparable engine that can be compared to the Spitfire?
I suppose one could consider how much faster an early Spitfire is to a Hurricane, but that is a waste of time.
The Merlin Mustang makes a pretty good comparison though because both were equipped with the same engine at about the same time.

The other factor I was intending to comment about was the roll rate. The Spitfires with metal ailerons especially those with clipped wings had a VERY fast roll rate. (About 150 degrees per second at 200 MPH IAS) They were not quite as fast as the FW 190, but were better than nearly anything else flying. In fact, up to a bit past 200 MPH, they actually rolled faster in a steady state than the FW 190. The non clipped wing versions were not that bad either. (About 105 degrees per second at 200 MPH IAS) This beats the vast majority of fighters of the time.

- Ivan.

 

[Shortround6]

Just saw these great pictures
by Terry in the "Flying Legends 2018" thead.

Please note the angle of the flaps.
They are doing just about nothing for lift and are acting as air brakes (drag producers and/or lift spoilers).
This was rather common for flaps designed in the mid 30s. You still needed a big wing for take-off but the flaps kept you from floating down the runway for a long distance on landing and steepened the glide angle/approach angle.

 

[pbehn]

Hello Pbehn,
This was not intended as a Spitfire versus Mustang discussion or even a comparison of the two aircraft other than for the simple characteristic of speed.
If you look at the original post I was replying to, you will note that it was a discussion of the characteristics of the Spitfire.
Why the heck did they design it that way?

While I agreed with most of what was stated, two of the characteristics did not seem correct to me.
I chose to address the "at least competitive speed" comment which I believe was not correct.
Is there another aircraft with a comparable engine that can be compared to the Spitfire?
I suppose one could consider how much faster an early Spitfire is to a Hurricane, but that is a waste of time.
The Merlin Mustang makes a pretty good comparison though because both were equipped with the same engine at about the same time.

The other factor I was intending to comment about was the roll rate. The Spitfires with metal ailerons especially those with clipped wings had a VERY fast roll rate. (About 150 degrees per second at 200 MPH IAS) They were not quite as fast as the FW 190, but were better than nearly anything else flying. In fact, up to a bit past 200 MPH, they actually rolled faster in a steady state than the FW 190. The non clipped wing versions were not that bad either. (About 105 degrees per second at 200 MPH IAS) This beats the vast majority of fighters of the time.

- Ivan.

But time is everything. The twin stage supercharger merlin engined Spitfire was in service with the RAF before the Allison engined Mustang. By the time the Merlin engined P-51 appeared in service in UK the front line Spitfire had a two stage Griffon. Prior to the P-51D going into service the RAF had the Tempest and Meteor in service. As S/R has said there is no doubt that the P-51 had superior aerodynamics, not just the laminar flow wings but also the cooling set up made better use of the Meredith effect and had lower drag anyway, plus the all around fit of joints. My point was about what was contemporary with what. I said the Spitfire with clipped wings had a good rate of roll compared to most, this would have been of little comfort to its pilots who were actually facing the Fw 190.

 

[Ivan1GFP]

But time is everything. The twin stage supercharger merlin engined Spitfire was in service with the RAF before the Allison engined Mustang. By the time the Merlin engined P-51 appeared in service in UK the front line Spitfire had a two stage Griffon. Prior to the P-51D going into service the RAF had the Tempest and Meteor in service. As S/R has said there is no doubt that the P-51 had superior aerodynamics, not just the laminar flow wings but also the cooling set up made better use of the Meredith effect and had lower drag anyway, plus the all around fit of joints. My point was about what was contemporary with what. I said the Spitfire with clipped wings had a good rate of roll compared to most, this would have been of little comfort to its pilots who were actually facing the Fw 190.

Hello Pbehn,
WHY are you trying to make this into a Spitfire versus Mustang argument?
All I will state for the record is that the two aircraft are quite different in many characteristics.
I actually agree with the details of your posts but the point is that we are NOT discussing the same thing.
My point was that the Spitfire was relatively slow for the amount of installed engine power. Do you disagree with that?

- Ivan.

 

[pbehn]

Hello Pbehn,
WHY are you trying to make this into a Spitfire versus Mustang argument?
All I will state for the record is that the two aircraft are quite different in many characteristics.
I actually agree with the details of your posts but the point is that we are NOT discussing the same thing.
My point was that the Spitfire was relatively slow for the amount of installed engine power. Do you disagree with that?

- Ivan.

Yes. for the reasons I have set out at length. Speed was only ever one criteria of the Spitfire, it was an interceptor, rate of climb was another, as was firepower and time of front line service. Start at September 1939 and detail when it was second best and to what.

 

[MiTasol]

Re post #68 (quoting is not working today)

Yes they could have added a ten gallon tank behind the pilot but then you add extra weight (wich degrades performance), a lot of extra plumbing (fuel and vent), an additional fuel selector position (which affects spares interchangeability), increase the possibility of the engine going quiet during some stage of operation due to fuel starvation, increased chance of leakage due to damage, etc.

Worse still, if this tank very small tank is used for start and taxi there is the possibility during a scramble that the pilot will fail to change tanks at the end of the runway resulting in the engine going quiet about the time the aircraft leaves the ground giving the pilot little or no chance of survival.

The other option of drop (slipper) tanks was used on the Spitfire but the design of those was far from perfect because they were an airfoil pointing down meaning they cancelled a portion of the aircraft's lift at a time when increased lift was required to compensate for the increased weight.