Monday, 30 July 2012

Kinkead's Crash in the Supermarine S.5

N221, Kinkead's Supermarine S.5 (painting by author)

The death of Flt. Lieut. Samuel Kinkead,  whilst making a speed record attempt in a S.5 is the first fatality in a Supermarine crash which might be attributed to mechanical failure and so, if for no other reason, it is worthy of special consideration. Previously, Biard had survived the demise of the S.4 and both incidents reflect the increasing performance demands of the Schneider Trophy. Indeed, Mitchell, in a speech at a Rotary meeting in Southampton had given a glimpse of the feelings that he felt in connection with this sort of design work:
The designing of such a machine involved considerable anxiety because everything had been sacrificed to speed. The floats were only just large enough to support the machine, and the wings had been cut down to a size considered just sufficient to ensure a safe landing. The engine had only five hours’ duration; after that time it had to be removed and changed. In fact everything had been so cut down it was dangerous to fly. Racing machines of this sort are not safe to fly, and many times I have been thankful that it was only a single seater. The machine itself has been a source of anxiety to me right from the start, and I am pleased to know that at this moment it is safely shut up in a box.
Six weeks after the 1927 Schneider Trophy competition in Venice, a new world speed record was achieved at 297.8mph in a Macchi M.52, and so, the following March, the Air Ministry had the reserve S.5, N.221, which was not used in Venice, “taken out of its box” and prepared for an attempt to recapture the World Absolute Air Speed record.
The attempt was to be flown by Flt Lt Kinkead, who had had to retire from the previous Schneider Trophy competition in the Gloster machine. Unfortunately, the attempt was to end in tragedy – as reported in Flight on March 15, three days after the crash:
The machine, for reasons yet unexplained, suddenly dived into the Solent from an altitude of about 100 ft. while Flight-Lieut. Kinkead was flying over the measured course, and immediately sank without leaving a trace of man or machine, other than just  a few small pieces of wreckage.
Flight-Lieut. Kinkead had been waiting at Calshot some ten days for an opportunity to beat the 297 m.p.h. set up last November by the Italian pilot, Maj. De Bernardi. Weather conditions, however, were by no means favourable most of the time, and only once did he get a chance to make a trial flight, which was entirely successful.
On the morning of March 12 conditions seemed favourable for a flight, but an oil leak developed, and by the time this was set aright, the weather had broken up. All through the afternoon a snowstorm rendered a start hopeless. Then, shortly after 4 p.m., conditions changed entirely, and it was calm and sunny. Lieut. Kinkead therefore decided to make an attempt and the S.5 was brought out once more. After a preliminary run of the 875 h.p. Napier “Lion” engine, the pilot packed himself away in the tiny cockpit and the seaplane was launched into the water.
Besides the official timekeepers, a number of spectators were present to witness the attempt. Amongst these were several foreign Air Attachés, Capt. H. C. Biard, Mr. R. J. Mitchell, designer of the machine, and many other prominent figures in aeronautics. With little if any wind to help him, Flight-Lieut. Kinkead experienced some difficulty in getting the S.5 off the water, but once in the air the machine flew well at terrific speed. After a short circle round, Flight-Lieut. Kinkead brought the machine down and made an absolutely perfect landing, thus complying with the regulations which demand that the machine attempting the record must make two alightings to prove its seaworthiness – the first landing was made the previous day.
Although, by this time, a mist was forming over the water, Lieut. Kinkead immediately took off – again with some difficulty – once more, this time obviously with the intention of making the attempt on the record. The S.5 soon disappeared from view in the direction of the Isle of Wight, and then after a short interval was observed as a tiny speck rapidly approaching Calshot, the scream of its engine getting louder and louder.
When about two miles from the station, near Calshot Lightship [the start of the 3 km record course], all who were intently watching were horrified to see the machine plunge suddenly, nose first into the sea. A huge column of water rose into the air as the machine struck, and when this subsided, not a trace of the S.5 was visible. To add to the terrible effect of this disaster, the scream of the engine came across the water for what appeared to be an appreciable time after the machine disappeared from view.

Precisely what happened is unlikely ever be fully established as the S.5 was imperfectly visible to the witnesses on the land. As we shall see later, it was asserted that Kinkead had decided to abandon the attempt because of decreasing visibility and had stalled on the landing approach; the Flight correspondent advanced another possible cause:
There is no reason to believe that anything did go wrong with either machine or engine: Kinkead was, according to accounts, flying at a height of something like 100 ft. when the accident happened. Allowing for a very short time in which the machine changed its horizontal course into one sloping downward, it might well strike the water within a period of considerably less than one second from the time it commenced to depart from a horizontal flight path. Thus even a very momentary disturbance of any sort might well have caused the disaster. It has been suggested, quite seriously, that if the pilot were to sneeze, this might in itself cause him to depress the elevator sufficiently to make the machine swoop down into the sea.

Equally, sun glare, coupled with an obscured horizon and a waveless sea, would have given precious little information to confirm altitude or flying attitude, so others maintained that, with the poor visibility, he misjudged his height and flew straight into the sea whilst still intent on the speed record.
   However, a recently published book, Racing Ace: the Fights and Flights of ‘Kink’ Kinkead by Julian Lewis has brought to light certain eye-witness accounts which could lead to the conclusion that the cause of the accident might very well have been structural failure – contrary the findings of the internal RAF Court of Inquiry and the Southampton Coroner’s Inquest, both of which gave the cause of death as 'stalling'. 

(i) The possibility of a high speed stall caused by violent manoeuvres  can  surely be ruled as he would be doing nothing more than making minor corrections to his altitude or direction on the fatal approach run; and the possibility of a stall whilst having to make a landing approach because the visibility had deteriorated must take into account the Times’ description of his skillful landing of the S.5 on the day before the record attempt: ‘he chose an angle of glide which almost imperceptibly brought the floats nearer and nearer the water until the monoplane was just skimming the surface – a grey insect over a grey sea.'
(ii) Even if Kinkead had made a rare landing misjudgement, there seems to have been no mention of a gradual decrease in engine sound before his crash – on the contrary, spectators were impressed by the sound of an approaching high-revving engine which suddenly ceased and two commentators even described his impact with the water like that of a shell.
(iii) Also contrary to the landing scenario, the coroner at the inquest is reported as ‘trying to find out if there is a possible explanation of the sudden dive of the seaplane’  This  is echoed in the Morning Post headline, ‘Vertical Nose-dive from 100 feet’ or The Times report that Kinkead ‘dived straight into the Solent from a height of between 100 feet and 50 feet’.
(iv) Thus mechanical failure rather than pilot error must thus be given particular attention. Lewis cites newspaper reports from observers of ‘abnormal movement of the tail unit and fin’ (The Times) and of the aircraft ‘going at a very good speed’ when its tail developed ‘a pronounced flutter’ (the Daily Express). Supermarine test pilot Biard, who was standing next to Mitchell at the time of the accident, is also quoted as being quite certain that the crash was a result of structural failure and his likely reaction at the time might have contributed to Mitchell’s distress for some time afterwards.
It should be acknowledged that the other two similar S.5 machines had successfully completed the Venice Schneider Trophy course, which involved the taking of two extremely sharp corners on each of the required seven laps whilst returning an average course speed of about 88% of the top speed available to them. Kinkead's S.5 had not been extensively tested, or flown in the Schneider Contest a few months earlier, but the preliminary flight on the Sunday before the fatal crash and the second mandatory flight, flown on the day of the accident, went off without any problem; however, its specially tuned engine and light fuel load might have allowed Kinkead to reach a new top speed that brought with it unexpected structural problems.
(v) But most problematic, in view of the various considerations above, are the findings of the RAF Court of Inquiry that the accident was ‘due to stalling of the machine’ and the verdict of the Southampton Coroner’s inquest that Kinkead’s fatal injuries were caused by diving into the sea ‘owing to lack of speed while attempting to alight’. In the latter case, it was also maintained that no evidence had been found in the wreckage to point to any physical causes for the accident although how this could be upheld in view of the extensive damage caused by impact and by the subsequent salvaging operation might perhaps only be explained by a wish to draw a discreet veil over the whole matter. [One reads in Lewis that a file concerning the private RAF Court of Inquiry, referred to in Kinkead’s Service Record, has not survived and Hugh Trenchard, Chief of the Air Staff, had been a reluctant participant in the recent Schneider Trophy preparations as he was still very protective of his new Air Force. From another perspective, certain senior Air Ministry officials were unlikely to be happy with findings of mechanical failure as, in their case, they were in favour of continuing RAF involvement in the Schneider contests for the sake of research and development and of the prestige accruing to the British aviation industry via this blue riband event.]
It is thus interesting that, at the inquest, the Inspector of Accidents, whilst agreeing that ‘the rudder or tail of the machine was seen to be fluttering’, said that it was ‘probably the reflection of the sunlight from the rudder that gave the impression’ when the machine turned.  Had a turn been necessary, it would surely have been made well before the crash site, in order to maximise the entry speed into the actual speed course, and one would in any case expect only slight movements of the rudder at the speed that Kinkead was going – producing equally slight, progressive, changes of colour tone to the rudder (but not with reference to the tail as a whole – as reported above by witnesses). And one wonders how bright was the sunlight if Kinkead had actually been attempting to land because of the worsening visibility.

* * * * *

Whilst a stall due to ‘pilot error’ remains a possible reason for the death of Kinkead, there is, to say the least, no overwhelmingly supporting evidence and, indeed, there was an article in the Times, two days after the accident:
Kinkead had preserved complete reticence as to the exact speed at which he travelled in his trial flight on Sunday morning, and no-one had realised that he had reached, on his air speed indicator, a rate of no less than 330 miles per hour. . . Kinkead was so enthusiastic after his trial flight that he said he believed he could attain probably 350 miles an hour. It should be realised that this type of monoplane had never before been flown, probably, at more than 300 miles an hour, and . . . no-one could be certain that stresses, which were within the capability of aircraft engine and propeller at 300 miles an hour, might not rise to an unexpected magnitude when the speed was increased to 350 miles an hour. . .
As it stands, the findings of the inquest can be seen as the least worst outcome for all parties except the pilot. This is an especial pity as little mention is made of the Schneider Trophy pilots when credits are given for winning the Battle of Britain and all that followed. If these pilots had not successfully flown their, frankly, dangerous aircraft, the Spitfire might not have been ready in time for the outbreak of World War Two – one notes at least D’Arcy Greig’s dedication in My Golden Flying Years ‘to all those involved with the Schneider Trophy races that helped so much in the development of the Spitfire in later years’.

It is well recognised that Mitchell’s Spitfire and its Rolls-Royce Merlin engine were ultimately a by-product of the Schneider Trophy competitions, where manufacturers were free of inhibiting Air Ministry requirements, but not enough has been said in this context about the skills of the High Speed Flight pilots who took part in this early test flying. Of these, Kinkead’s 1927 group can be seen as the one which took the primary and most dramatic leap into the unknown.
   It is hoped, therefore, that Kinkead will not be remembered as a pilot who was said to have died because of an error of judgement but as one willing to take the risks involved of the dangerously low speed run for the sake of national prestige and whose previous decorations were duly recorded by Flight:
      For his war services he received the following decorations:- D.S.O., for attacking and dispersing a Cavalry Division in South Russia. D.S.C. for conspicuous gallantry and skill in face of enemy aerial combats. Bar to D.S.C., for attacking and bringing down an Albatross machine. Bar to D.F.C. for engaging and dispersing a large party of enemy troops in a wood.
     The King has sent the following message to Sir Samuel Hoare, the Air Minister:-
     “I am grieved to learn of the loss sustained by the Royal Air Force in the tragic death of Flight-Lieut. Kinkead, who had such a distinguished career in the Service. Please convey to the relatives of the gallant airman an expression of my sincere sympathy. – GEORGE. R.I.” 



I am indebted to Racing Ace: the Fights and Flights of ‘Kink’ Kinkead by Julian Lewis for much of the above information; for other reference sources, see my Blogpost: “Source Material and References" – an extended bibliography is included in my R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire (details below) which also provides material for wider reading, grouped according to specific areas of interest. 

More information, photographs and a three-view drawing of the S.5, as well as a full account of all Mitchell's completed designs and of the man behind them, will be available in a few weeks' time:
Advance Notice – 
R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire.
This is a much expanded, completely up-to-date, second edition of my earlier work with 50% more photos, and 25% more text – 380 pp. instead of 250. There are general arrangement drawings of Mitchell’s 21 main aircraft types which flew, as well as 40 other drawings. There are 24 photographs, featuring or including Mitchell, as befits the first fully detailed and, I hope,  definitive account of the man and his work at Supermarine.
To obtain a copy at pre-publication prices, please enquire via the contact form in the sidebar.

Friday, 13 July 2012

R. J. Mitchell’s Bomber and his death.


My painting above is based upon
 Supermarine Drawing 31600 Sheet 2  and Supermarine works models.
 
    In the last full year of Mitchell's life, and even when he was putting the finishing touches to his Spitfire design, another innovative project for a bomber had been occupying his mind. This was in response to Air Ministry specification B.12/36 which called for a high-speed, four-engined, long-range bomber with a range of 3,000 miles, capable of carrying up to a 14,000 lb bomb load or 24 soldiers. It also had to be able to be broken down into component parts for transport by the existing railway system and to lift off from a 500 ft runway, clearing a height of 50 ft at the end; for this last purpose there was added a requirement to provide a catapult take-off capability (because of the small airfields currently in use and, particularly, in order to extend the bomber's potential range and load capacity). At the same time, the wingspan was to be limited to no more than 100 ft (to discourage over-large projects which would take too much precious time and materials to produce rather than because of the size of existing hangars, as is often claimed). It also had to have a retractable ventral turret as well as nose and tail guns and had to be capable of staying afloat for several hours in the event of being forced down in the North Sea or Channel.
   In the same month that the very positive Martlesham Heath report on the Spitfire prototype was received, Mitchell's tender for the bomber had been sent to the Air Ministry and must have confirmed the officials' regard for Mitchell's importance to the aviation industry: despite having a proposed wingspan of 97 feet, it nevertheless was to make use of a single spar wing supported by torsion-resistant leading edge boxes on a similar principle to that developed for the Spitfire; and, unusually for its time, fuel was to be carried in these leading edges, thereby saving weight, and with the tanks adding to the rigidity of the wing. Behind this spar component, the structure allowed sufficient room for the main stowage of bombs, thus avoiding the need for conventional tiered bomb stowage which would have substantially increased the fuselage cross-section and its drag component. Prior to this design, the  Polish PZL  P.37 medium bomber had made extensive use of bomb bays in the wing between the engines and the fuselage, as did an Armstrong Whitworth A.W. 42 proposal but Mitchell’s bomb stowage arrangements in the wings was more extensive and not adopted in any of the other front-line bombers of World War II.

From Drawing 31600 Sheets 5/6 showing leading edge tanks and stowage of 27x500 lb/29x250 lb bombs
 A further refinement was the proposal to place the required guns well below the eye-line, not only giving the gunners an improved view but also enabling a reduction in the cross- section of the turret and a more rapid traverse of the guns.
Three versions of the Bomber were proposed: 
Type 316 with Bristol Hercules engines, deltoid shaped wing (see  drawing above) and single fin:


Type 318 with Rolls-Royce Merlin engines but otherwise similar to 316; 
and Type 317 with Bristol Hercules engines, twin fins, and wing leading and trailing edges tapering almost equally (see painting above).

      By November, 1938, Mitchell’s team was able to submit a set of estimated performance figures which make an intriguing comparison with published figures for the earliest Marks of the most well-known British four-engined bombers of comparable size:

Aircraft
Power Rating
Range
Bomb Load
Max. Speed
Supermarine (estimate)
1330 hp
3,680 miles
8,000 lb.
330 mph
Stirling I
1590 hp
1,930 miles
5,000 lb.
260 mph
Halifax BI
1145 hp
1,985 miles
5,800 lb.
265 mph
Lancaster I
1390 hp
2,530 miles
7,000 lb.
287 mph






 
More often than not, Supermarine estimates were actually achieved when their designs flew but it will always be a matter of conjecture as to whether these figures for Supermarine’s proposed bomber would have been attained  – after all, it was conceived at the same time as the Stirling and Halifax but with an estimated speed close to that of the new fighters; and its projected range and bomb load were also impressive. It might, however, be maintained that, with the need for volume production – using standard gun turrets and probably being forced to add a dorsal one too – the Supermarine performance figures might have turned out to be much closer to those of the production bombers quoted above.
    Unfortunately the project only reaching the stage of two prototype fuselages when they were destroyed by enemy bombing and Mitchell never lived to learn of the fate of his last main project, just as he never actually saw his Spitfire go into squadron service before World War II started.

Towards the end of February, 1937, Mitchell went into a London hospital. The prognosis was not good and a stay at the Cancer Clinic in Vienna was arranged in the April. Letters testify to his dismay at not being able to continue his input into the design of the bomber but it became clear that this was not possible. Mitchell returned to Southampton on the 25 May, 1937, and died on 11 June, aged 42.
   As he invariably gave full credit to his design staff in his speeches, it was fitting that he requested they be given first place at his funeral and it is perhaps significant that Harry Griffiths’ recollection of Mitchell’s death prompts a memory of his relationship with this team:
On the day he died Arthur [Black, chief metallurgist] and I were standing at the bench discussing a problem when Vera Cross, R J’s faithful secretary over many years, came in and just said, ‘It’s all over.’ Arthur looked at me and shook his head then he turned away and was silent for a long time.
At the annual dinner that year we stood in silence in his memory and then drank a toast: ‘To a very gallant gentleman.’
The Christmas before his untimely death he arrived late for the annual design staff dinner, and in spite of a place having been kept for him at the head of the table he insisted on sitting at the other end with us lads and sharing a joke and some wine.





I am indebted to John Dell (Dinger's Aviation Pages) for some of the information above. For other reference sources, see my Blogpost: “Source Material and References" – an extended bibliography is included in my R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire (details below) which also provides material for wider reading, grouped according to specific areas of interest.

More information on the bomber, the bombing of Supermarine and photographs, as well as a full account of all Mitchell's completed designs and of the man behind them, will be available in a few weeks' time:
Advance Notice – 
R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire.
This is a much expanded, completely up-to-date, second edition of my earlier work with 50% more photos, and 25% more text – 380 pp. instead of 250. There are general arrangement drawings of Mitchell’s 21 main aircraft types which flew, as well as 40 other drawings. There are 24 photographs, featuring or including Mitchell, as befits the first fully detailed and, I hope,  definitive account of the man and his work at Supermarine.
To obtain a copy at pre-publication prices, please enquire via the contact form in the sidebar.