de Havilland 100: Making of the Moth

First flown five years into the life of Geoffrey de Havilland’s eponymous company, the DH60 Moth showed the potential for a practical light aeroplane, and set its manufacturer down a very successful road. However, much had been learned from a rather less user-friendly machine, conceived with the overly restrictive rules of the Lympne light aeroplane trials in mind: the DH53. To open our de Havilland centenary special, we examine the Humming Bird’s place in history 

If you’re not quite sure what you’re looking for, you can be forgiven for setting off with the wrong foot, making mistakes and establishing a scenario that future generations might look back on and smirk over. A clear-cut example of this sort of behaviour is today remembered as the Lympne trials of the 1920s.

The purpose of those distant events was a quest that ultimately was intended to result in the ideal light aircraft. On reviewing the evidence in the way of the aeroplanes put forward as contestants, you could be excused for thinking otherwise.

There were four events in this corner of Kent, each quite different from the other. The first was the British Gliding Competitions, staged in the hills around Itford in 1922. This was followed by the Motor-Glider Competitions, held at Lympne in 1923. The same venue was the setting for the Two-Seater Competitions of 1924 and, finally, the Light Aeroplane Competitions of 1926.

In those days, our daily newspapers were of a different calibre than perhaps they are now. The main ones were headed up by notable, usually titled, families who were invariably royalists and keen on promoting the greatness of Great Britain. Publishing was also something of a gentleman’s contest where the winner was the newspaper with the highest circulation. And circulation was achieved by getting people to read the most interesting stories in your paper.

It was with circulation foremost in mind that our two biggest popular broadsheet nationals of the time — the Daily Mail and the Daily Express — regularly took to sponsoring things associated with the comparatively new and exciting world of aviation. One way in which this was done was with competitions and prize money.

This format was not altogether a British idea. The French press had been doing exactly the same thing for some while. After it became known that Louis Blériot was in the eye of a top Parisian paper, our Daily Mail promptly announced a £1,000 prize for the first Englishman to repeat his performance.

The Itford gliding competitions attracted prize money from the Mail when it learned that the Germans excelled in this sport. Gallantly the purse was open to all comers, Germans included. The success of this event inspired that curiously named 1923 event, the Motor-Glider Competition. Gradually we were moving towards a goal of some sort, but nobody quite knew what sort of outcome was likely.

The competition itself proved to be a rather ad hoc affair. Looking back, it seems a combination of bad weather and a number of designs from what we now call time-wasters contrived to make for a somewhat amateurish occasion.

It was into this mêlée that a youthful Geoffrey de Havilland entered the field of ultralight aircraft with his DH53 Humming Bird, built for the newspaper-sponsored trials at Lympne in October 1923. It was wholly a private venture. Nobody specified or sponsored it other than de Havilland himself.

A prize of £500 was offered to encourage the building of an economical light aircraft which would be suitable for club and private flying. The type was to be a single-seater, powered by an engine not exceeding 750cc. The main object of the competition was to achieve the greatest distance on 1.2 gallons (4.5 litres) of petrol. de Havilland was, of course, no newcomer to the world of aircraft design. He had a clear understanding of his brief and the Humming Bird proved a well-thought-out concept. For example, the rudder was of a larger area than might be needed, but with the overly long fuselage this provided an adequate lever arm designed to suit a slow-speed aircraft with minimal propeller slipstream. The fuselage was a basic box structure covered with 1mm-thick plywood and the aircraft was equipped with a  conventional,  simple, through-axle  undercarriage. Together these  features saved weight and, furthermore, ensured a degree of durability.

In those days, aerofoil choice was limited to the results of work conducted at Farnborough by the Royal Aircraft Factory. The more advanced work on wing sections was yet to be completed. America’s influential National Advisory Committee for Aeronautics (NACA) had been founded on 3 March 1915, but its first papers on airfoil — or aerofoil — design were not to be widely available until the mid-1920s. For this reason, Geoffrey de Havilland had a limited choice of established wing sections from which to choose. The one he favoured at the time, and had used on most of his designs, was the old RAF 15 which, in modified form, had been in use since the war. Significantly, in later years it was still this and its later sister section, RAF 45 (modified), which DH preferred.

The DH53 had conventional two-spar wings with the advantage of differential ailerons made to de Havilland’s own patented design. This mechanism would be used most successfully on the later Moth designs including the DH60 and DH82A Tiger Moth. Its principal benefit was the diminution of adverse yaw on entering a turn, and it achieved this by ensuring the ‘high’ aileron dipped only to initiate the bank, not to maintain it.

Two prototypes were built, G-EBHX subsequently being retained by the firm and G-EBHY going on to be privately owned. The machines were initially powered by 750cc Douglas motorcycle engines. In spite of considerable problems with this powerplant, both aircraft did well. Maj Harold Hemming flew Humming Bird number 12, G-EBHZ, while Hubert Broad piloted number 8, G-EBHX.

The main object of the competition was as pointless as it was simple. It was to find out who could cover the greatest distance on 1.2 gallons (4.5 litres) of petrol. In the event, the DH53 covered 59.3 miles (95.5km) on that amount of fuel. Others, though, did slightly better as smaller engines made for better distances. And frail airframes were usually lighter.

Unreliable engines were the bane of most contestants, the DH53 being no exception. Such were the contest rules and the limited thinking of the time (engine servicing and repairs were not allowed during the competition) that the Humming Bird’s participation in the contests was rewarded with neither prizes nor awards of any kind. This fact alone spoke volumes for the thought processes behind the event.

At the end of the competition, Broad thought he would attempt to set some sort of altitude record in number 8. His engine, however, thought otherwise, and having stopped on the climb what happened next made people stand up and gasp in amazement. Broad demonstrated the control and manoeuvrability of his mount when, on gliding down for a ‘deadstick’ landing, at 400ft he began a series of Immelmann turns — a form of stall turn, or roll-off-the-top, named after the German fighter ace Max Immelmann — and finished it off with two loops, landing safely off the last.

And so the 1923 contest came and went. It had attracted 29 entries, of which 28 were accepted and a number didn’t show for one reason or another. These were all extremely lightweight single-seaters, powered mainly by improbably small motorcycle engines. As aircraft they were grossly underpowered and the airframes were made in the lightest possible manner. Structural failure was ever just around the corner as design safety factors were second-placed to save pounds in weight.

Two weeks after the Lympne event, there was a race meeting for light aircraft staged at Hendon. In the interval between the two, de Havilland took the opportunity to exchange the Douglas of Hubert Broad’s DH53 number 8 for a Blackburne Tomtit inverted-V two-cylinder engine, an inverted version of the Blackburne unit. This motor had proved the most successful engine at Lympne both as regards performance and reliability. Broad was so confident in the strength of the Humming Bird with its new powerplant that he opened the meeting with a display of aerobatics.

In fact, the Tomtit engine and its larger sister, the Thrush, enjoyed a long-forgotten connection with Geoffrey de Havilland. Before he turned to the newly evolving aircraft business, he had worked briefly for Willans & Robinson of Rugby, a company which was a renowned maker of steam engines. It was there in 1903 that he met two young apprentices, the brothers Cecil Stanley and Edward Alexander Burney.

The young de Havilland had designed and built his own motorcycle which attracted the Burneys’ attention because it had, for its time, a first-rate performance. When they found the future aviation figurehead had no interest in its production, they were overjoyed; the more so when de Havilland offered to sell them the rights to his design, together with the casting patterns for the engine, for the princely sum of £5.

The Burney brothers, together with pioneer aviator Harold Blackburn, were able to start producing their de Havilland-designed ‘thugging-iron’ together with its de Havilland-designed engine. Ready for the road at the beginning of 1904 — the first year of vehicle registration — it carried the licence plate FF41. Trading as Burney & Blackburne (spelled with a terminal letter ‘e’), they operated from a factory at Northchurch near Berkhamsted in Hertfordshire. From there they built motorcycles based on de Havilland’s design and developed engines until the outbreak of World War One, when they moved to Tongham near Farnham in Surrey.

Meanwhile, in 1910 Geoffrey de Havilland had joined HM Balloon Factory at Farnborough, which became the Royal Aircraft Factory. There he sealed his future in aviation with George Holt Thomas and the Airco business. War service saw him promoted to the rank of captain and promoted to serve as Airco’s chief designer. After the war ended, the depressed years up to 1920 saw de Havilland launch out on his own as the de Havilland Aircraft Company. He designed and built a pair of gliders for the 1922 Itford meeting, but these were unsuccessful: one broke up spectacularly in the air, without badly injuring its pilot.

In the interim, Burney & Blackburne had shifted motorbike and engine production from Tongham to the Atlas Works at Bookham, Surrey. It seems de Havilland must have kept a fatherly eye on the business, because when it came to the 1923 Motor-Glider Competitions he thought back to his motorcycling days and his engine.

While the organisers of the 1923 contest didn’t think much of the DH53’s performance, and the prize donors — which, beside the Daily Mail, included the Royal Aero Club and the upmarket Abdulla tobacco company — saw nothing in its performance worth awarding a prize for, the Humming Bird attracted attention in higher places. That December, two things happened which endorsed the little Humming Bird’s reputation. First was an unexpected order from the RAF. The second was an adventurous trip to attend the Brussels Aero Show.

With an eye to its economic performance, the Air Ministry issued an order for eight aircraft for communications and flying practice. These were to be powered by the 28hp Tomtit, an engine that had demonstrated an advantage over the Douglas during the contest.

We may wonder today what on earth attracted the ministry to consider a single-seat, low-powered flying machine with so relatively marginal a performance. It must have had a good reason at the time, especially since the permitted military load was just 7lb, or 3.17kg, or pretty much the weight of the contents of a schoolboy’s pockets! Admittedly it was a period of stringent economy.

If the truth were known, looking back on it now, we can see that the Humming Bird had overall one of the best performance envelopes of all the participants in that 1923 contest. Besides this order for eight machines, in the fullness of time five others would be ordered for private customers, three going to Australia, one to Czechoslovakia and one to Russia.

The batch for the Air Ministry would be supplied under two contracts, the first for six machines and the second for two aircraft. These would be allocated serial numbers J7268-J7273, J7325 and J7326. A novel experiment concerned the last two, which were employed in trials that involved the aerial launching and recovery of an aircraft with an airship. These took place with the R33, G-FAAG. Both examples were fitted with a pylon and pick-up gear for attachment to a trapeze lowered from the airship.

Experiments were undertaken with the airship piloted by Flt Lt Irwin which left its mast at Pulham, Norfolk, on 15 October 1925, carrying J7325. On top of the fuselage was erected an inverted trapeze-like tubular steel structure, At an altitude of 3,800ft, Sqn Ldr Rollo Amyat de Haga Haig climbed into the DH53’s cockpit via a ladder from the airship. The aircraft with its trapeze framework was lowered clear of the gasbag and then released.

It was reported that the DH53 dived until the engine started, executed two loops and then returned to the underside of the airship, which was travelling at its full speed of 62mph. While this maiden launch was a success, a second attempt with the same aircraft on 28 October was not.

Turbulence close to the dirigible caused the DH53’s airscrew to foul a supporting bracing wire, resulting in such severe oscillation that the pilot was compelled to make a forced landing at Starston close to Harleston in Norfolk.

The whole process was a potentially hazardous exercise, there being a real risk of accidentally ripping the belly out of the airship with the rotating propeller. This was hopefully guarded against by the shape of the hook-up frame. On 4 December, the attempt was repeated, this time using J7326. This time all went well. The pilot returned safely to R33 and was able to rejoin the airship’s crew.

Unfortunately, it was not recorded exactly what the purpose of these undertakings was, let alone how the DH53/airship combine was supposed to be used in a defensive or observation role. While flying your own attack/defence aircraft to a target by airship might have seemed a good idea on paper, in reality the practicalities of it were rather suspect.

The main batch of six DH53s for the RAF made their public debut when they took off together at the start of a race between the Air Ministry Directorates at the Hendon Pageant on 27 June 1925. The noise of half a dozen Tomtits can only be imagined today.

Following the disposal of all eight aircraft by the RAF in 1927, all were civil-registered and went on to fly for some years. The first batch were allocated G-EBRW, G-EBRJ, G-EBRA, G-EBXN, G-EBIT and G-EBRK, and the final two aircraft G-EBXM and G-EBQP.

The other event of that December back in 1923 came about as the outcome of a remark made by de Havilland’s colleague, Francis St Barbe. He thought it might be worth exhibiting the little Humming Bird at the Brussels Aero Show. Furthermore, it was felt a good idea if Alan Cobham, then flying for DH, went along with it as a sort of salesman.

Author C. Martin Sharp recounts in his book D.H. that when he was approached about this, Cobham asked “What’s its range?” “Don’t worry”, responded St Barbe. “You can read all about that in the train”. “Why the train? Won’t it fly?”… “Do you mean you’d fly it there?” questioned an incredulous St Barbe.

In the end, Cobham did fly the machine all the way from Stag Lane to Croydon and thence via Lympne to Brussels. The difficulty was that the DH53 really didn’t have anything like the necessary range, so an additional two-gallon capacity fuel tank had to be made and fitted. Chief draughtsman Arthur Ernest Hagg installed a small extra tank in the only available position — to double as a headrest behind the pilot’s head. This, however, posed a fresh problem. It was not high enough to allow gravity feed to the engine’s carburettor. There being no commercially available fuel pump small enough for the job, a simple and lightweight solution was arranged. A rubber tube was installed into which Cobham could blow so as to give pressure feed to the tank.

As it turned out, the fun was not yet over. When Cobham got to Lympne to refuel for his epic crossing of the English Channel, the 100-gallon fuel bowser drew up and asked how much fuel he wanted. The two-gallon fill-up came to 7/6d — about 38p in today’s money.

The 150-mile non-stop flight to Brussels was completed at an average cruising speed of about 40mph and mostly through fog. It was thus something of an achievement in itself despite all-too frequent periods of rough running from the engine as the pilot’s breath-induced condensation and air bubbles mixed with the fuel supply. After the 10-day exhibition, a dramatic weather change brought snow and strong winds, perhaps fortuitously in the circumstances, so the return trip had to be by train and boat. The DH53, however, had proved itself once more.

Once the dust had settled from these events, it was clear that the quest for the ideal light aircraft was still far from over. Both Cobham and de Havilland agreed that the Humming Bird, while probably one of the best aircraft at the trials, was simply too small and underpowered to make a suitable machine for flying training. The Lympne proponents, in the form of the Royal Aero Club and the prize-giving Daily Mail, were somewhat far from reality in their ‘ideal specification’ of lightness and low power.

Nevertheless, both of the two DH aircraft that had made it to the skies at Lympne would continue to amaze crowds for a long while to come. They later took part in several air races, while the prototype was sold to a group of RAF officers who re-engined it with a 30hp ABC Scorpion, which proved anything but reliable. Number 8, G-EBHX, which had also been Cobham’s mount to Brussels, would remain flying into the 21st century as a key attraction at the Shuttleworth Collection.

It was for this event that Robert Blackburn designed his Bluebird, powered by a three-cylinder Blackburne Thrush. So troublesome was this engine that in the event it was a non-starter. Only when re-engined later with a 60hp Genet I radial did it perform well. Blackburn and de Havilland were obviously singing from the same hymn-sheet.

The generous Daily Mail had put up prize money of £5,000. The way the rules were drawn up, however, still missed the point. Whereas the ultimate goal was to end up with the ‘ideal’ two-seat training aircraft, the judging committee was still influenced not by common sense but by those false Gods of fuel economy and distance flown.

Meanwhile, de Havilland had produced the four-seat DH50 and the better-known three-seat DH51. Both these large biplanes demonstrated the characteristics Geoffrey de Havilland had considered to be vital for the ideal training two-seater: sufficient power reserve, adequate control and docile flight characteristics. 

de Havilland now had all the pieces of the jigsaw in his lap. From this melange of ideas came forth an aircraft design so perfect in its execution that it became a cornerstone of flying, both in a training role and in the club and private-owner sphere. It was called the DH60. Prototype G-EBKT first flew in February 1925, too large, heavy and powerful for the ‘Lympne Lords’. A tandem two-seater biplane, it was initially powered by one of Maj Frank Halford’s stunning new four-cylinder upright ADC Cirrus engines, but in order to get the weight down to the maximum specified by the 1926 competition rules, de Havilland installed an Armstrong Siddeley Genet I five-cylinder radial in G-EBOU, which flew as such in September 1926.

Unfortunately, the weight was still outside the specifications of the contest so the DH60 could not take part. Nevertheless, the aircraft proved to be a revelation. It also sealed de Havilland’s contention that no practical light aeroplane should have a cruising speed of less than 80mph and carry enough petrol for three hours’ flying.

Winners at Lympne that year were the low-powered and rather flimsy Hawker Cygnets. G-EBMB won the first prize while another example, G-EBJH, took second. de Havilland’s eminently practical Genet Moth was not even a contender.

The quest for the practical lightplane was now over. But what of the competition winners? Well, they went down in history for their achievements, but they would also be remembered as failing to live up to expectations. Time would prove whether those rules were on the right track, or whether the young man at Stag Lane knew better.

Looking back almost a century later, did the Lympne trials teach us anything, or were they just a waste of time, effort and money? They taught designers to evolve components and complete airframes that combined strength with lightness of weight. If anything, they taught us to hone our skills to the limit. But they were well and truly off-course in trying to give us a robust and adequately powered training aircraft.