Why airplanes were designed the way they were.

[Shortround6]

Thanks to the information provided by MikeMeech in Hard runways in WWII

It appears that in/by 1938 the RAF was specifying new fighter airfields with 800yd runways. Distance to 50ft not given and by 1939 they wanted 1000yd runways. They were also specifying at least two pitch props on fighters and heading for constant speed props which helped take-off and climb out. But they were stuck with the Hurricane and Spitfire which had been designed for the old airfields.
Also helps explain the Hawker Typhoon only needing a wing 7% larger than the Hurricane. You can blast the plane off the runway using the power of the Sabre engine but you still have to land the beast. Even with fat tires

 

[Holtzauge]

And here we get to the heart of the matter.
Hawker and Supermarine both failed to meet the specification. Hawker by a little and Supermarine by a lot. There is also a difference between prototypes and service models.

Hurricane prototype at 5672lbs needed 265 yd take off run and 430 yds to clear the 50ft barrier. corrected for zero wind. Not bad but the problem was landing. It needed 475 yds from 50ft. with brakes and with a 5mph wind. Everybody who thinks they should have cut 30-60 sq feet of wing area please raise your hands
Problem really hits home when the weight for a service Hurricane I with wooden two blade prop hit 6040lbs and the take off run went to 370yds and distance to 50 ft went to 580yds.
Now lets add another 50 gallons of fuel had see how much runway we need
Things got better with the 2 pitch propeller but that was around 3 years after the Hurricane prototype flew.

Take-off figures for the Spitfire prototype are not listed on WWII Aircraft Performance but Aug through Dec 1938 K.9787 gave the following results.
K.9787 was almost 500lbs heavier than the prototype.

420yd take off run with 720 yds to 50 ft. and landing run was 380 yds with brakes. This was corrected to no wind and standard atmosphere. With an 8mph head wind and at 20 degrees F (?) the take off run was 367yds and it took until 640yds to clear the 50ft distance. Landing ground run was 315yds.

So which brave (but suicidal) pilots want to strap a 50-60 gal tank to the plane and take off from a standard RAF fighter field on a hot summer zero wind day so they can escort any sort of bomber across the channel? Things got better with two pitch prop with the take-off run shortened to 320yds and distance to 50 ft down to 490yds.

109 with Jumo engine was designed to carry two machine guns and only 270 (?) liters of fuel and had better flaps (not saying much), You can use a much smaller wing when the plane only weighs around 4400lbs.

As I recall it, there was also an "alightening speed" requirement of 60 mph not to be exceeded which the Spitfire did not live up to. And as far as I know there were voices raised in the British procurement organization that it and the Westland entry should both be struck off the list for failing this requirement, which as I understand it was put there because it was not felt that higher speeds were consistent with safe night operations at the time. However, when the Spitfire's superb speed performance (compared to the other entries) became apparent, it was allowed to stay in the competition. Then about the Bf 109: As I recall it the Germans instead had a wing loading requirement which Willy Messerschmitt choose to ignore because he knew that high wing loading is the easiest and safest path to high speed performance. It is said that Milch (who did not like Messerschmitt), still allowed the Bf 109 to compete with the others like Heinkel, not as a serious contender, but more as a "pike in the carp pool" to make the (in Milch's view) more serious contenders walk the extra mile. However, as we all know, this plan backfired on Milch and the rest is history.......

 

[Geoffrey Sinclair]

As of June 1934 the Hurricane prototype normal loaded weight was expected to be 4,600 pounds, by December 4,800 pounds, as of August 1935 5,200 pounds, as weighed in October 5,416 pounds with Watts two-bladed, fixed pitch (wood) airscrew fitted. As of March 1938 first production Hurricane L1547 Normal Loaded Weight was 6,017 pounds.

Gauntlet F7/30 at best (no prototype as such, K4081 FF Dec-34), Gladiator F7/30 & F14/35 (FF Sep-34), Hurricane F5/34 & F10/35 (FF Nov-35), Spitfire F10/35 (FF Mar-36), Defiant F9/35 (Aug-37), Whirlwind F37/35 (Oct-38) Blenheim night fighter decided on in mid 1938, first examples around in December.

From 1935 on the expected size of a fighter airfield was rapidly changing, at least some would need to be light bomber size. Even a 2 man crew single engine fighter was going to need more room than a single seater.

First Hurricane column DH, second column Rotol propeller and yes the report actually says adding weight to the Whirlwind reduces take off run.

Aircraft

Defiant I

Beaufighter I

Blenheim IVF

Tomahawk

Havoc I

Havoc II

Gauntlet

Gladiator

Hurricane I

Hurricane I

Spitfire I

Whirlwind

Wing Sq ft

250​

503​

469​

236​

465​

465​

315​

323​

258​

258​

242​

250​

Tare (pounds)

5938​

13,918​

9,236​

5,615​

11,800​

13,073​

2,933​

3,695​

5,210​

5,085​

4,795​

8,040​

Weight (pounds)

7710​

19,816​

12,660​

7,224​

15,400​

16,700​

4,028​

4,757​

6,629​

6,532​

6,255​

9,980​

Take Off (Over 50 ft) (Yards)

500​

790​

550​

570​

600​

420​

320​

370​

520​

430​

400​

630​

Landing (Over 50 ft) (Yards)

770​

940​

730​

630​

560​

551​

n/a

475​

610​

600​

590​

750​

-

-

-

-

-

-

-

-

-

-

-

-

-

Weight (pounds)

n/a

21,120​

14,100​

7,602​

n/a

n/a

n/a

4,912​

6,758​

6,661​

n/a

10,115​

Take Off (Over 50 ft) (Yards)

n/a

940​

720​

620​

n/a

n/a

n/a

420​

540​

445​

n/a

580​

The RAF 15 minute allowance for the Spitfire I used 19.5 gallons, leaving 64.5 gallons available for cruise at 15,000 feet. At 304 mph that gave a range of 415 miles, at 180-190 mph 575 miles, simply adding the extra 12 gallons of forward fuselage fuel the mark VII and VIII carried extends those ranges to 490 and 680 miles, give the mark I the full 124 mark VII and VIII internal fuel capacity and the ranges are 670 and 930 miles. Quite adequate if based in France (though Nancy to Berlin is about 415 miles versus 580 from London) but the RAF at best was doing the occasional light/medium bomber escort training, the heavies, like Wellingtons, were on their own.

Agreed a neutral Holland/Belgium/Denmark makes air attacks to/from Britain/Germany long range affairs, going over the North Sea runs into two RAF declared impossibilities, long range fighter and single seat fighter pilot having long range navigation skills. Belgium in the war as per WWI largely removes the range problem, more so as the RAF over rated the importance of the Ruhr.

I thought the multi thousand RAF heavy bomber ideas were post June 1940, not pre war.

 

[Shortround6]

Then about the Bf 109: As I recall it the Germans instead had a wing loading requirement which Willy Messerschmitt choose to ignore because he knew that high wing loading is the easiest and safest path to high speed performance. It is said that Milch (who did not like Messerschmitt), still allowed the Bf 109 to compete with the others like Heinkel, not as a serious contender, but more as a "pike in the carp pool" to make the (in Milch's view) more serious contenders walk the extra mile. However, as we all know, this plan backfired on Milch and the rest is history.......

Well, there was quite a bit of evolution with the 109.
Willy and the boys did use a smaller wing but compared to the British fighters the 109V1 with the Kestrel engine and no guns was about 1800kg. A service 109B was about 2000kg and a 109E about 2600kg depending on guns. 109E empty weight was just over the loaded weight of the 109V1. The extra power of the DB601 certainly helped the speed and climb. Increasing the wing loading by almost 30% didn't help either maneuver or landing qualities. Adding another 20% to go from the 109E to the 109G-6 (57% more than the 109B) certainly didn't help. But that is as evolved vs as designed. The 109 was not designed to fight/fly/land at a wing loading in the high 30lb/sq/ft range.
Other planes were and they had different landing gear (and longer runways) and different flaps, etc to try to deal with it.

 

[Shortround6]

I thought the multi thousand RAF heavy bomber ideas were post June 1940, not pre war.

I am reading few books that are rather critical of the RAF in the late 30s and early 40s and there may be some bias going in the books. There may a difference in the ideas/plans/dreams of some RAF officers and what was ordered and when. Telling the treasury/parliament you want 2000lb heavy bombers in 1936/37 may get you early retirement as you are obviously barking mad
Easing them into it by ordering lots of smaller bombers (Blenheim's and larger) and creating the squadrons and then reequipping the squadrons with newer/larger aircraft may have been a long term plan. The RAF was to win the future war by itself, no need for the army or even the navy.
Some of these bomber officers may have even begrudged getting Hurricanes and Spitfires as that cut into bomber production and only bombers could win wars, fighters could not.
Over looked was that fighters might keep you from loosing the war in meantime.

Author may have his own agenda but the infighting at the Air ministry/war department may have come close to rivaling the Japanese army and Navy.

 

[Holtzauge]

Well, there was quite a bit of evolution with the 109.
Willy and the boys did use a smaller wing but compared to the British fighters the 109V1 with the Kestrel engine and no guns was about 1800kg. A service 109B was about 2000kg and a 109E about 2600kg depending on guns. 109E empty weight was just over the loaded weight of the 109V1. The extra power of the DB601 certainly helped the speed and climb. Increasing the wing loading by almost 30% didn't help either maneuver or landing qualities. Adding another 20% to go from the 109E to the 109G-6 (57% more than the 109B) certainly didn't help. But that is as evolved vs as designed. The 109 was not designed to fight/fly/land at a wing loading in the high 30lb/sq/ft range.
Other planes were and they had different landing gear (and longer runways) and different flaps, etc to try to deal with it.

"The 109 was not designed to fight/fly/land at a wing loading in the high 30lb/sq/ft range." Well neither was the Spitfire: There was not only an evolution in terms of wing loading for the Bf 109: This was also the case for the Spitfire which actually ended up with a higher wing loading in the Spitfire Mk 14 than the Bf 109E4 had in 1939. The weight creep lead to both designs having wing loadings at the end of the war that would have seemed outlandish in the late 1930's. My point was that Messerschmitt in the initial design work was allowed to go to a 25% higher wing loading (125 kg/sqrm) than the other competing German designs from Heinkel and Arado which at a time were limited to 100 kg/sqrm (or 20.5 lb/sqft). In addition, all things are relative and "Adding another 20% to go from the 109E to the 109G-6 (57% more than the 109B) certainly didn't help." and "Increasing the wing loading by almost 30% didn't help either maneuver or landing qualities." Well, both the P-47C and P-51D had higher wing loadings that the Bf 109G6, so I would not be too worried about the Bf 109 G6 having a particularly high wing loading.

 

[Art Medcalf]

Most aircraft are designed for a purpose or multiple purposes. The designer has a pantry of ingredients to mix in order to come up with a recipe that works for the intended purpose. In the rapidly changing first half of the 20th century, the availability of materials, engines, engineering knowledge (ie., structural and aerodynamic design techniques), and infrastructure (airfields, fuels, manufacturing capabilities). to name a few. Availability of money and manpower are always considerations. We have now reached a plateau where a transport aircraft today may not look dramatically different from one designed 50 years ago. Try saying that in 1950! However, technology is a many splintered thing and the devil is often in the details. Thus an aircraft that does not appear much different from another may, based upon the parameters each is judged by (first cost, operating cost, payload, infrastructure requirements (for example, runway length), be much better or worse. The operative words for any designer are tradeoffs and iteration.

W.A.Medcalf PEME (aviation nut 1937 to 2024)

 

[Holtzauge]

Most aircraft are designed for a purpose or multiple purposes. The designer has a pantry of ingredients to mix in order to come up with a recipe that works for the intended purpose. In the rapidly changing first half of the 20th century, the availability of materials, engines, engineering knowledge (ie., structural and aerodynamic design techniques), and infrastructure (airfields, fuels, manufacturing capabilities). to name a few. Availability of money and manpower are always considerations. We have now reached a plateau where a transport aircraft today may not look dramatically different from one designed 50 years ago. Try saying that in 1950! However, technology is a many splintered thing and the devil is often in the details. Thus an aircraft that does not appear much different from another may, based upon the parameters each is judged by (first cost, operating cost, payload, infrastructure requirements (for example, runway length), be much better or worse. The operative words for any designer are tradeoffs and iteration.

W.A.Medcalf PEME (aviation nut 1937 to 2024)

Absolutely: I believe the phenomena is called the technology S-curve. And commercial aviation is now on the upper, mature part of the S-curve asymptotically approaching the optimal. As a boy, I flew in the brand new Boeing 747 "Jumbojet" from London to Johannesburg in 1970 IIRC, but AFAIK the 747 was retired just a few years ago. Granted, the engines on the late versions were quite different and more fuel efficient than back then but the airframe? Basically the same. Just like sharks really: not much to improve on!