Airspeed Napier Sabre fighters - June 1940

[Schneiderman]

The Napier Sabre ran on the bench for the first time in January 1938 and was soon delivering in excess of 2000hp. The Air Ministry had already issued fighter specifications for aircraft to be powered by a high-powered engine, such as the Sabre, and a contract was awarded to Hawker for the Typhoon.
Development of the Sabre was slow, however, and while the problems were being addressed Napier decided to use one engine for an attempt at the World airspeed record and asked Arthur Hagg to design a racer specifically for this engine. Hagg had had a long and successful career with de Havilland where he had designed the Moth family, the DH88 Comet racer and the DH91 Albatross airliner before falling out with management and resigning in 1937. The racer was built by the Heston Aircraft Company as the Napier-Heston Racer in 1940. This was a highly promising design but its potential is regrettably unknown as it was wrecked on its first flight after the cooling system was damaged on take-off. Hagg continued to work with Napier advising them on engine installation issues. In 1942 he joined Airspeed (1934) Ltd as chief designer.
Airspeed had worked hard to obtain orders for advanced aircraft; bombers, fighters and airliners, but had failed to achieve success and seemed stuck building Oxfords and other relatively undemanding aircraft. With the arrival of the Sabre they embarked on another attempt, as described below.

Airspeed Aircraft since 1931, H.A.Taylor, Putnam 1970
Other Sabre-engined fighter projects were also worked upon by the Airspeed team, including one with a well-faired fixed undercarriage and cranked wing. Both this and a retractable-undercarriage version had their radiators aft of the cockpit with cooling air ram-fed into an underside scoop and venting through slots in the tail. A verbal order was given officially at one stage to Airspeed for a day fighter which formed the basis for these undesignated projects, using wooden construction as a means of conserving strategic materials. The order was later revoked under pressure, it is believed, from another sector of the aircraft industry.

This work took place in mid-1940, a turbulent time for Airspeed as de Havilland had become the majority shareholder and had placed their own men on the board, which must surely have distracted Hessell Tiltman, part-owner, director and chief designer, from detailed design work. The design of the above two aircraft is likely the work of one of his subordinates, but judging from the obvious similarity to the Napier-Heston Racer, a secret aircraft that had not yet flown, could it be that Hagg had offered advice?
So……..

 

[Schneiderman]

Two designs from June 1940 powered by a Napier Sabre and housing 12 machine guns. There are a number of differences between the two, other than the fixed undercarriage. The cockpit has been shifted, the inverted gull-wing is modified and it is slightly shorter.

 

[lark]

Great !

Thanks.

 

[hesham]

Amazing find Schneiderman;

and there experience led to develop Napier Tailless Fighter as I think;

http://www.secretprojects.co.uk/forum/index.php/topic,3461.msg27590.html#msg27590

 

[blackkite]

Super!! Thanks for sharing.

 

[Schneiderman]

Amazing find Schneiderman;
and there experience led to develop Napier Tailless Fighter as I think;
http://www.secretprojects.co.uk/forum/index.php/topic,3461.msg27590.html#msg27590

I would doubt it, they are very different concepts. Airspeed were looking at ways to produce a quick, cheap fighter using non-strategic material, as Martin Baker and Miles had suggested before, while Napier were simply investigating radical concepts as part of a research programme. Rolls-Royce carried out similar investigations
http://www.secretprojects.co.uk/forum/index.php/topic,3441.msg27421.html#msg27421

 

[Hood]

An excellent find.
Do you know what Specification these were designed for or based on? Or where they purely private-venture ideas they were trying to sell to the Air Ministry?

 

[Schneiderman]

I suspect that it was a private venture although the fixed undercarriage, wooden construction and twelve guns is very much like that of the Merlin-powered Miles M20, which had specification F.19/40 written around it. If the comments in the Putnam about Airspeed receiving a verbal order for the aircraft are correct then I guess that would have been to F.19/40 too, the timing would be right. Selecting the Napier Sabre was probably a mistake.

 

[cluttonfred]

Wonderful finds, thanks for sharing Schneiderman. I was also going to bring up the Miles M.20 for comparison and I agree that the Miles choice of a standardized RR Merlin "power egg" made a lot more sense than the Sabre. Do I understand correctly that the radiator cooling air would have exited the airframe on either side of the rudder? Ingenious, but it seems to me that the radiator would have Ben very vulnerable in the aft fuselage.

 

[Schneiderman]

Yes, the radiator duct system looks remarkably like that on the Napier-Heston Racer, minus the special Gallay radiator. I guess a rear positioned radiator would be slightly more vulnerable in a conventional rear attack than one shielded by the wing or engine.

 

[blackkite]

Ummm.......What is the merit of this radiator position compared with Mustang radiator arrangement?
http://www.secretprojects.co.uk/forum/index.php?action=dlattach;topic=27685.0;attach=561245;image
"their radiators aft of the cockpit with cooling air ram-fed into an underside scoop and venting through slots in the tail."

Engine ram air intake is located wing root leading edge.
Armament is very powerful.

Attached drawing shows Napier-Heston Racer and Mustang radiator arrangement.

 

[Schneiderman]

The artwork in this Napier advertisement from late 1941 looks suspiciously like Airspeed's project.

 

[alertken]

#1 The order was later revoked under pressure, it is believed, from another sector of the aircraft industry.

Delete it is believed.

Lord William Weir had managed Air's shadow production schemes, 1917-18, and was Advisor to Lord Swinton, Air Minister inending to do the same in 1935.
In WW1 Ministers had little difficulty imposing the scheme on a new industry used to dribble production orders and to Govt paying, so owning, 100% of R&D.

In Peace Govt. invented the Ring of firms that, alone, would be invited to bid for new design work: it was a way of running down surplus Munitions capacity.

In 1935 the Stock Exchange's then-equivalent of dot-com was Rearmament, vast profits foreseen. New investors clambered in, some buying into Ring firms, others happily funding new kids on the block, like Airspeed. Swinton and Weir sat with the Ring and committed to continue to invite new design solely from them; in turn they would collaborate to provide drawings and help to shadow new entrants, to be brought in for the duration and not to be subsidised as future competitors. So, until DH, a Ring firm, took some equity in Airspeed, no (tasty) new design could be awarded to them. So they won a simple adaptation as Oxford of a privately-funded comms. type (Envoy), and they could have assault gliders, because they were not aircraft-as-we-know it.

Ministers later stretched their adherence to Swinton's commitment, to greatest benefit of EE/Preston. But that was why Martin Baker got nowhere, nor Nuffield or Fairey with engines.

 

[Schneiderman]

I rarely, very rarely, find myself disagreeing with alertken but in this case his comments are not entirely correct.
One notable aspect of the investment boom of the mid-1930s was the move by the shipbuilding industry to move in to grab a share of the aviation business. For Airspeed, always struggling for funds, this involved Swan Hunter buying a controlling interest; the original company went into voluntary liquidation and then relaunched as a public company, Airspeed (1934) Ltd. Wishing to avoid perceived profiteering from military contracts, which had resulted in the imposition of punitive excess profit taxes on some companies after WW1, the government pushed through a cost+ system with the SBAC for the rapidly growing number of new contracts. On top of this there was an industry wide severe shortage of qualified and experienced design staff. To formerly non-aviation and somewhat risk-averse management this all made subcontract work and simple follow-on projects such as the Airspeed Oxford appear much more attractive than new design work.
Airspeed took four years to crawl back into profit and by 1938 Shute Norway, one of the founders, had quit in frustration. The factory was now fully occupied building Oxfords. In mid 1940, just as these new fighter designs were being firmed up, Swan Hunter sold their interest in the company to de Havilland, triggering a big change in directors and disruption at the top of the company. DH showed no special interest in Airspeed designs and set about an immediate move of the design staff to Hatfield. Hessel Tiltman, chief designer and the other co-founder of Airspeed, found himself effectively side-lined, and although he did not quit until 1942 his influence was much reduced.
In the circumstances it would have been inappropriate for MAP to proceed with formal approval for the fighter project and Taylor's comment that " A verbal order was given officially at one stage to Airspeed for a day fighter which formed the basis for these undesignated projects, using wooden construction as a means of conserving strategic materials. The order was later revoked under pressure, it is believed, from another sector of the aircraft industry." appears quite sound, "another sector" quite conceivably being DH themselves.

 

[alertken]

We not at odds: entirely poss. that DH was the "other sector". When they bought into Airspeed, 27/5/40, DH had an order (1/3/40) for (only) 50 Mosquitos, Freeman's Folly, and was phasing down Hatfield Tiger Moths as Morris Aero/Cowley ramped up, not, per Putnam, to introduce cascades of Mossies, but of...Airspeed Oxfords, first Hatfield batch ordered 9/38. To kill off an A/S combat scheme, by reminding Air Minister Sinclair (and/or 14/5/40 Min. of A/c Prodn. Beaver) of Swinton's commitment to the 1920 Ring, would be a logical ploy to aid (=reduce) price settlement with Swan Hunter. Geoffrey DH wanted both the capacity of A/S Portsmouth+their upcoming MAP-funded plant at Christchurch, and their Design Authority status on Oxford, so he could take on more of them - why are Boulton&Paul/Norwich, Elliotts of Newbury, Parnall/Yate, Percival, Standard involved?

Beaver, to maximise output of NOW! types, would suffocate much, 25/5/40, deleting fantasy "Ideal" Heavies, 6/40. A/S-Napier had no chance in all this.

 

[Schneiderman]

Yes, on the same page.
I often feel that The Ring was used as a convenient excuse by some post war, along with sniping at bureaucrats, boffins and military bigwigs. Easier to pass the buck for perceived lost opportunities onto others. MAP did a pretty good job, all things considered, and given the war priorities not all companies were best employed building new stuff, even if that were feasible.

 

[Hood]

I think it was probably a pre-war grievance too, for example Percival Willoughby seems to have run a long campaign throughout the 1930s bemoaning the lack of official funding for his Delta F prototype and pointing out the unfairness of the Air Ministry not supporting smaller firms, especially in the field of civil aviation.
I think in this case it was more of a case of tunnel vision, the Ministries could never support every one-man band with a bright idea.

Not everyone could build new stuff and as with any market, people tend to trust (rightly or wrongly) those who have been around the longest and had a track record. Nobody was going to easily knock Messers DH, HP, Avro and Blackburn off their perches (and Mr Fairey though he wasn't a pioneer aviator)- they had been pioneers, they became the industry and built it around them. A track record during the Great War probably helped given the institutional 'muscle memory' the civil servants possessed.

As for shipbuilding investment, their own market had taken a terrible beating and the industry was in a very bad state during the mid-30s. Along comes aviation which looks like its in boom time, then the government starts enlisting the motor industry in the Shadow Factory scheme so firms like Swan Hunter and John Brown want a slice of that action. These investments probably came just before the larger Royal Navy rearmament contracts, it was a shrewd move but of course they could only invest in companies seeking funding (thus already struggling) and there was the downside.

What amazes me is how English Electric pulled it off in 1944-46 and actually built up one of the most successful post-war aviation companies. Had you told any members of 'The Ring' in 1939 that in 21 years time a Northern producer of locomotives and electrical equipment would form one half of the British Aircraft Corporation - one of only two big combines left in the industry, I don't think they would have believed you.

 

[Schneiderman]

The pioneer names certainly carried a lot of weight but they were mostly backed by extremely astute business partners who helped steer them through the austerity years of the 20s - Holt Thomas, Siddeley, Lord and similar. Once the mega-mergers kicked off around 1927, and then in 1934, they were increasingly difficult to compete against. They had the staff, research/dev facilities and production capacity that the others largely lacked. Not to mention contacts in high places and room on the board for useful ex-military and government types.

 

[newsdeskdan]

What amazes me is how English Electric pulled it off in 1944-46 and actually built up one of the most successful post-war aviation companies. Had you told any members of 'The Ring' in 1939 that in 21 years time a Northern producer of locomotives and electrical equipment would form one half of the British Aircraft Corporation - one of only two big combines left in the industry, I don't think they would have believed you.

EECo wasn't entirely without form in aviation, having built aircraft and dealt with the Air Ministry from 1921-1926. It was such a vast industrial concern by 1939, when it re-entered the field of aviation, that I doubt any members of 'The Ring' were surprised. And of course English Electric then purchased Napier & Son in 1942 - bringing fighter development directly into the company boardroom.

 

[Hood]

EECo wasn't entirely without form in aviation, having built aircraft and dealt with the Air Ministry from 1921-1926. It was such a vast industrial concern by 1939, when it re-entered the field of aviation, that I doubt any members of 'The Ring' were surprised. And of course English Electric then purchased Napier & Son in 1942 - bringing fighter development directly into the company boardroom.

That is very true, though it must be admitted that their early efforts at their own designs during the early 1920s were largely a failure, EECo was lucky they had so many other diverse interests, such failures would have killed a small independent firm.
In hiring Petter they got a temperamental genius and struck it lucky. Had Petter taken up a job offer elsewhere with his briefcase of the early proto-Canberra tactical jet bomber designs in tow, things would have been very different for another company.

 

[Wurst]

Hello everyone, are there any drawings of the Napier-Heston Racer? 3 side views would be great.
I would like to build it in a scale of 1:72. I already have the decals for this one and no money for expensive resin kits.

 

[Apophenia]

Hello everyone, are there any drawings of the Napier-Heston Racer? 3 side views would be great.
I would like to build it in a scale of 1:72. I already have the decals for this one and no money for expensive resin kits.

Depends upon what degree of detail you are looking for. Here's a couple of lo-rez versions ...

The Aeroplane drawing came from The Napier-Heston Racer by Bill Gunston, June 1976. I don't know the origin other drawing.

 

[sienar]

 

[Wurst]

Thank you ! I didn't expect so much information at all. Then I can start building the beauty.

 

[iverson]

Here a few more drawings.

 

[Nicknick]

Ummm.......What is the merit of this radiator position compared with Mustang radiator arrangement?

http://www.secretprojects.co.uk/forum/index.php?action=dlattach;topic=27685.0;attach=561245;image

"their radiators aft of the cockpit with cooling air ram-fed into an underside scoop and venting through slots in the tail."

Engine ram air intake is located wing root leading edge.
Armament is very powerful.

Attached drawing shows Napier-Heston Racer and Mustang radiator arrangement.

Actually, the air wasn’t slowed down to increase the heat transfer rate, but to reduce the pressure loss over the radiator. So smaller the pressure loss over the radiator, so more pressure will be in front of the flap and hence thrust.

The boundary layer channel solution like in the Heston racer was later used in some versions of the BF109.

 

[Calum Douglas]

 

[Dagger]

Actually, the air wasn’t slowed down to increase the heat transfer rate, but to reduce the pressure loss over the radiator. .................................

Indeed.

Just for info: slowing down the air decreases the heat transfer rate in W/m2 of BTU/hr.sqft.

The lower the fluid velocity over a heat exchange surface the lower the heat transfer coefficient, so more exchange area is required. That applies to all types of heat exchangers.
This is always a dilemma when designing a heat exchanger with low pressure drop.
In turbulent flow, if velocity is decreased by a factor 2, the pressure drop will decrease by a factor 4, while the overall heat transfer coefficient (U-value) decreases by only a factor 1.5 to 2.
Increasing the heat exchange area by a factor 1.5 to 2 to compensate for the decreased U-value still results in a heat exchanger with a pressure drop that is a factor 2 to 2.5 lower due to lowering the fluid velocity by a factor 2. The weight and cost of the exchanger will however increase due to increase of its exchange area.

 

[Nicknick]

The cross section of the cooler should be as large as possible whiche the entrence in the diffusor should be as small as possible, just keeping the air flow high enough. Therefor the heat exchanger was mooved to the rear of the fuselage because it was the only area in a fighter plane which is usually quite empty and offers enough space.

The one thing which I find quite intresting is, how important is the outlet position of a cooler? Will an outlet at the front produce significant more drag? Warm air has a higher viscosity and the relative air speed will be higher than that of the surrounding air, as well as turbolenz. The Heston racer might cooling outlet might have been more effective than that of the Mustang.

 

[robunos]

Therefor the heat exchanger was mooved to the rear of the fuselage

No. The radiator was placed in mid-duct. See the drawings in Post #25 for it's position.

cheers,
Robin.

 

[Nicknick]

I might have used a vague expression, I mean everything behind the cockpit is reawards, because in a classic fighter configuration it is mostly empty.

 

[Wurst]

What an impressive piece of aviation history! The fighter derived from this (at this time) would have represented a leap in performance.
So that I can recreate it technically correctly:
Does anyone have any idea how the rear shock absorber works? This is not clearly visible in the pictures (hidden in the grass) and drawings. In order to be able to spring, it would have to be extended, similar to the Me 209 V-1...

Here you can barely see the shock absorber on the Me 209 V-1:

Source: http://www.primeportal.net/hangar/francesco_pomi/me_209_v1/








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