Dinger's Aviation Pages
The misconceptions of the British 1912 "ban" on monoplanes.

Many books and articles, written from the mid 1940s into the 1990s, imply that the British Air Ministry effectively banned the use of monoplanes from before the start of WW1 through until the mid-1930s. That was certainly not the case. This article aims to shed light on the true story.



The Blackburn Type D monoplane of 1912. The oldest British aircraft still flying; it is part of the Shuttleworth Collection.

Britain got off to a slow start in heavier-than-air flight, the USA and France being the foremost pioneers in the field. In the USA, the biplane designs of the Wright brothers and Glen Curtiss predominated; while in France, the biplane designs of Gabriel and Charles Voisin shared the skies with the monoplane designs of Léon Levavasseur and Louis Blériot. The early British aviation pioneers found inspiration from both sides of the Atlantic and both biplane and monoplane designs enjoyed equal popularity in the UK.

Modern preconceptions make most people think of monoplanes as being more "modern" and streamlined than biplanes. However, with the technologies and materials available in the early years of the twentieth century, it was impossible to build a true cantilever monoplane. The early monoplanes had to have their wings supported by cables attached to the fuselage.

A simple analogy of the difference between a biplane and the early monoplanes is to consider the biplane as a girder bridge and the monoplane as a suspension bridge...


A biplane can be considered to be like a girder bridge. If built with sufficient strength it can withstand both the downward force of gravity (or multiples of that if high "g" forces are encountered). Crucially, it can also withstand an upward force (remembering that in flight it is the wings that support the fuselage) and multiples of that if "negative-g" forces are encountered.



The early monoplanes can be compared to suspension bridges. With the materials and technologies available it was necessary to support them with wires or struts from either the top of the fuselage or a pylon on top of the fuselage. This provided the strength to withstand downward forces. However, in this analogy, there is nothing to provide support against upward forces. On an aircraft in flight, there are upward forces generated by the lift on the wings and in "negative-g" manoeuvres this is increased.




So, our analogy of a suspension bridge to a monoplane is not completely correct. We have to add another set of wires or struts underneath the wing.





Another view of the Blackburn Type D monoplane, shows the many bracing wires required to keep the wing in place (although some of the wires are associated with the wing warping system the aircraft used in lieu of ailerons). The Blackburn Type D first flew at the end of 1912, some five or six months after the trials to select the best type of aircraft to equip the new Royal Flying Corp. Its predecessor, the two-seat Type E "military" monoplane had been intended to take part in the trials but its steel framework had proved too heavy for the power of its engine.

In August 1912, a competition was held by the British War office to determine the best type of aircraft to be employed by the British Army. 19 monoplanes and 13 biplanes were entered into the competition (not all actually competed.) The winner of the "British built" category was the Cody V biplane, which was purchased by the war office and a second example was ordered. Another of the competing biplanes, the Bristol GE2, was also purchased after the competition. Of the competing monoplanes, no less than five were purchased by the War Office, two Bristol Coanda monoplanes, two Deperdussin monoplanes (one built in France, the other in Britain) and a Bleriot XI-1 monoplane.


A Deperdussin monoplane.

It should be noted that the fledgling Royal Flying Corp (RFC) had been founded in April 1912, only 6 months before the competition; it had absorbed the Air Battalion of the Royal Engineers and initially was also responsible for air operations for the Royal Navy (this was separated off to form the Royal Naval Air Service in July 1914). It already operated a miscellany of types and it was the crash of one of these, a Nieuport monoplane on the 5th of July 1912, that caused the death of the first casualties of the RFC, Captain Eustace B Loraine and Staff-Sergeant Richard HV Wilson. The aircraft was executing a sharp turn when it crashed and it is presumed it stalled. This was a month before the competition to select new aircraft for the RFC.

Earlier, in February 1912, a series of crashes of monoplanes in France prompted the French Government to suspend all flying by monoplanes. The famous French aviation pioneer and manufacturer of monoplanes, Louis Bleriot, looked into the crashes and in March he sent a report to the French government warning of a design flaw in his own earlier designs of monoplanes and those of other companies. In the increasing tempo of aviation, pilots were doing tighter turns and starting to attempt aerobatics. This would involve increasing "g" forces on the wings, something that the design of the very early monoplanes did not take into account. Bleriot advised that the wire bracing of monoplanes be strengthened to take account of these forces. In the case of his own designs, this involved making the supporting cabane pylon on top of the fuselage higher to better handle the loads involved. The French Government acted on Bleriot's advice and quickly had all monoplanes in French service modified and put back into service. Although the issue was reported in the fledgling British aeronautical press, no action was taken to rectify this defect in monoplanes in British service.


Louis Bleriot; in 1909 he became the first man to fly the English Channel. His company manufactured a series of monoplane designs.

Only a few weeks after the completion of the competition to select aircraft for the RFC, the fatal crashes of two of the monoplanes selected by the trials forced the British Army to suspend the flying of all its monoplanes and order its pilots not to fly any civilian monoplanes. The first crash, on 6th September 1912, was of a Deperdussin monoplane; the pilot, Captain Patrick Hamilton and his observer, Lt Atholl Wyness-Stuart were both killed. The aircraft was seen to break up in the air. The second crash, on 10th September, was of a Bristol Coanda monoplane; The pilot, Lt Edward Hotchkiss and observer, Lt Claude Bettington were both killed. Their aircraft was seen to go into a steep dive and the fabric tore of one wing before the aircraft plummeted to the ground. It was the fact that both aircraft were seen to come apart in the air, with no possibility of pilot error or outside forces involved, that had forced the authorities to act. ¹



A Bristol Coanda monoplane. The designer, Henri Coandă, gave his name to "the Coandă effect".

A committee was quickly set up to look into the accidents. It produced a report that what given to the government on the 3rd of December 1912 and made public the following February. It concluded that none of the accidents could be blamed on the aircraft being monoplanes. It did note that the very nature of biplane design "admits of ample strength" but it concluded that there was no reason why monoplanes should not be as safe as biplanes if properly designed. The committee listed a series of recommendations to apply to any future purchases of aircraft by the Army (clearly influenced by Bleriots report to the French government) and advised that flying of monoplanes should recommence, providing that all existing monoplanes were inspected and found to either meet the recommendations or be modified to do so.

Thus the "ban" on monoplanes lasted only some five months and the RFC continued to operate monoplanes after the ban was lifted. In 1913, eight new Borel hydro-monoplanes were purchased for use by the Naval Wing of the RFC (The Royal Naval Air Service was separated off the following year). When war was declared in 1914 the RFC had a number of Bleriot monoplanes in service and some of these were despatched to France,
comprising two of the three Flights of No 3 Squadron. One took part in the first British reconnaissance flight of the war. Because of a shortage of British aircraft manufacturing capacity, the RFC scrambled to acquire more Bleriot and Morane monoplanes from French sources early in the war, with some production of Morane-Saulnier Type "H" shoulder-wing monoplane aircraft taking place under contract in Britain (although these were then mostly only used as trainers).


Eight French Borel monoplane floatplanes (they were called "hydro-monoplanes") were ordered for use by the Naval Wing of the Royal Flying Corp in 1913, the year after the "ban" was lifted. They were passed on to the Royal Naval Air Service (RNAS) when it was formed in July 1914.

Two monoplane types that saw service with the British in the first part of the war were the French REP Type "L" and the Morane-Saulnier Type "L". Both were of the parasol-wing layout. The REP L was used exclusively by the RNAS while the Morane-Saulnier L was used by both the RFC and RNAS. It was a Morane-Saulnier L of the RNAS that accounted for the first Zeppelin (the
LZ 37) destroyed in the air.


Two parasol monoplanes operated by the British in the early war years the Robert Esnault-Pelterie (REP) type "L" and the Morane-Saulnier Type "L". Note that both needed pylons to provide an anchor for the wires supporting the wings. Both were notoriously difficult to control and only the best pilots got the most out of them.



The Morane-Saulnier type "H" shoulder-wing monoplane was produced in the UK by the Grahame-White company of Hendon (the current site of the RAF Museum). The Royal Flying Corp used it as a training machine (although a single British example did serve in France). The Germans had more belligerent uses for the design, producing it as Pfalz E.1 to E.VI fighters and forming the basis for the famous Fokker Eindecker series of fighters.

The British Army was used to obtaining its weapons from government-run ordnance factories. So it had been a natural step to set up the
"Royal Aircraft Factory" to design and build aircraft to specifications laid down by the forces, to be used by the fledgling RFC (the designs would be contracted-out to commercial firms to build in quantity in wartime). The result was the super-stable and safe-to-fly BE2 biplane, which conformed to exactly what had been asked for. When the RNAS broke away in 1914, it adopted a different approach to procurement, taking on a range of aircraft from different commercial companies and then ordering further examples and developments of those designs that did best, "survival of the fittest" if you like. The Navy's approach did lead to tremendous wastage of resources, money, and sometimes lives in the first year of the war but it did bring to the fore successful designs from Shorts, Fairey, and Sopwith. Meanwhile, the Army's BE2 was found to be too ponderous to cope with the introduction of dedicated German fighter aircraft and the Royal Aircraft Factory was forced to close by a campaign run by Noel Pemberton Billing and CG Grey. This was a pity since the Factory had just produced the outstanding SE5 fighter and had some promising designs for both aircraft and engines in development. So there were two quite distinct organisations selecting aircraft for British use during World War One, the Army and the Navy, they both increasingly chose to use biplanes rather than monoplanes (although the RFC persevered with the French parasol Morane-Saulnier designs in the front-line until 1917).

Progressive developments of the French Morane-Saulnier saw service with the RFC during World War One, first the type "I" then the "V", both of which proved unpopular, followed by the two-seat MS24 type "P" (seen above) designed specifically for the RFC which was a much better aircraft, seeing service until 1917. The improved view of the ground for reconnaissance and scouting was an obvious advantage for parasol monoplane designs.

The inherent strength of the biplane layout, coupled with the inbuilt redundancy in structure enabled a biplane to survive damage much better than a monoplane. The increased wing area of a biplane enabled lower landing speeds and increased rate of climb to clear obstacles, making operation from the small landing fields in France much safer. The advantage of drag reduction offered by a monoplane was negligible at the speeds attained in WW1 and engine power was the most significant factor in speed performance. Thus the only real advantage of a monoplane built with the technology available during most of WW1 was better visibility of the ground for parasol types and better visibility in the upper hemisphere for low and mid-wing designs. Thus the biplane came to predominate during WW1, not only with the British Army and Navy but also with the Germans, French, Americans, Italians, Austrians and Russians. There is, of course, one major exception to this, the "Fokker Scourge" of 1915 caused by the introduction of the Fokker Eindecker monoplane. However, the Eindecker's success was not due to its monoplane layout (it was a development from the French Morane-Saulnier H shoulder-wing monoplane) but the combination of its then-unique synchronised machine gun (allowing it to fire through the propeller arc) and the fitting of increasingly powerful engines. The Fokker was countered by biplane designs from both the French and British. Manoeuvrability became greatly prized during the dogfights that predominated during the war, and the increased wing area of biplanes enabled tighter turning circles. Triplanes had a brief period of success, first the British Sopwith Triplane, then the Fokker Dr1, again stressing the importance of manoeuvrability.

Later in the war, monoplane designs did appear once more. The British Army introduced the
Bristol M.1C but considered its landing speed too high for operations from small airfields in France, so instead 32 of the production run of 125 (along with all three M.1Bs) were used in the Middle East and the Balkans for the last 18 months of the war. The remaining 93 M.1Cs being used for training pilots in the UK. The Germans introduced the parasol monoplane Fokker D.VIII but its introduction into service was marred by failures caused by poor workmanship in construction. A few metal Junkers CL1 ground-attack monoplanes were in service at the war's end as well as some Hansa-Brandenburg W-29 monoplane floatplanes. The Junkers D1 metal monoplane was on the verge of entering service, although in its initial form it was not as fast as the latest contemporary allied biplane fighters and was certainly not as manoeuvrable; although later projected developments (including two-seaters) may have been truly formidable.


Bristol M.1C monoplane; this example still flies at the Shuttleworth Collection. The fact that the British put the Bristol M.1C into production shows there was no bar to using monoplanes if their performance was a match for or better than their biplane contemporaries. Although it had a high top speed for the power of its engine, it was less manouverable than a Sopwith Camel and slower than an SE5a fighter. It only had one machine gun, whereas twin guns became the standard later in the war. It had poor downward visiblity, aleviated by having "window" sections cut out of the wing roots.

The formation of the Royal Air Force and the establishment of the
Air Ministry meant there was now a single organisation to oversee British military aircraft procurement. When the war was over there was a period of retrenchment in defence spending. However, a surprising number of new aircraft were ordered by the Air Ministry in the 1920s. The Ministry was not averse to considering monoplane designs, on the contrary, it financed the building of such experimental monoplanes as the Handley Page HP20, de Havilland DH29 and Beardmore Inflexible, and paid for numerous monoplanes from British companies for its official specifications. However, there were three overriding reasons why biplanes still predominated. Firstly, the lower landing speed of biplanes led to fewer fatal accidents. Secondly, the small size of the RAF's legacy airfields also militated against the longer take-off and landing runs of monoplanes. With hindsight, we can see that airfields were bound to get bigger, but that was not a given in the 1920s and early 1930s. The pace of aviation advance just from 1903 made many assume that further advances were bound to find solutions to the safety and airfield issues. The Air Ministry did not want to commit to an expensive programme to extend the size of its airfields if some new technical advance provided a solution. Indeed, the adoption of flaps and Handley Page slats seemed to hold out the promise of just such an advance.


The Handley Page HP20 experimental monoplane of 1921. Essentially a wartime DH9A bomber fitted with a thick monoplane wing, it featured leading-edge slats to bring down the landing speed. Its development was paid for by the Air Ministry.


The de Havilland DH29 "Doncaster" of 1921 lays claim to be the first British-designed, cantilever-winged (without bracing wires or struts) monoplane. The Air Ministry paid for its development. What looks like a "pylon" on top of the fuselage is a small header gravity feed tank for the fuel supply. The monoplane wings were made of wood with a fabric covering.


A rear view of a Doncaster, this was before the fitting of the gravity feed-tank.The projection you can se above the fuselage is a "stack" to carry the engine exhaust clear of the pilot. Two Doncasters were built and one was purchased outright by the Air Ministry and fitted out as a bomber with a dorsal gun position. The other DH 29 was intended for commercial use but it ended up with the Air Ministry as well. There were control issues with the design and de Havilland found it easier to develop a biplane version, the DH34, which proved a commercial success.



In 1921 the Air Ministry issued specification 2/21 to finance a novel idea from the Bristol Aircraft Company. Their modular "Bullfinch" aircraft could be put together in two ways: as a single-seat parasol monoplane fighter (pictured above) or as a two-seat biplane bomber, with the second, purely cantilever wing mounted under the rear fuselage. Three prototypes were built, two in single-seat fighter configuration and one as a two-seat biplane. Testing showed the single-seat monoplane version had an "adequate" performance but despite having a more powerful engine it was slower than the RAF's current biplane fighter the Gloster Grebe. The two-seat version was disappointing, not being able to carry the required weight of equipment and bombs.



The Air Ministry paid for the construction of two prototype Blackburn R.2 Airedale parasol monoplanes for specification 37/22 for a three-seat carrier reconnaissance aircraft. First flying in 1925, the Airedale showed no advantage over the types already in service.



In 1923 the Air Ministry contracted the English Electric company to build a lightweight monoplane single-seat trainer designed by William Oke Manning. Specification 4/23 was written around the design, which first flew in April 1923 and was called the
"Wren". The Air Ministry paid for the full development of the aircraft and purchased the prototype which went through extensive tests at Martlesham Heath. English Electric went on to build another two examples of the Wren, one of which is still in existence in the Shuttleworth Collection and still regularly flies.



It is often forgotten that the Air Ministry sponsored and paid for the Supermarine and Short monoplane contenders for the 1925 and 1927
Schneider Trophy races. Above is the Supermarine S4, built to an Air Ministry specification issued in 1923, it was entered in the 1925 race. It was a true cantilever design, having no bracing wires or struts to the wing. Unfortunately, it crashed during a test run. The subsequent Supermarine S5 and S6 designs reverted to having bracing wires.



Another monoplane Schneider Trophy design sponsored and paid for by the Air Ministry, the
Short Crusader. It was intended for the 1927 competition but it was evident that it would be too slow to win and so was used as a practice aircraft instead. It crashed prior to the competition.

The third reason for biplanes winning production orders was that with the engine power then available, the extra wing area of biplane fighters gave them a higher rate of climb and a higher ceiling than their monoplane contemporaries. There was no point striving for all-out top speed if the resulting aircraft could not climb fast enough to intercept opposing bombers coming over at height.



This is the de Havilland DH77 semi-cantilever monoplane fighter, one of four types of monoplane paid for by the Air Ministry for the F20/27 specification for a fast-climbing
interceptor. The other monoplanes ordered were the Westland F20/27 low-wing braced monoplane, the Westland "Wizard" high-wing parasol monoplane and the Vickers Type 151 "Jockey" (see below).



The Vickers Type 151 "Jockey" was structurally the most advanced monoplane fighter paid for by the Air Ministry for specification F20/27. It did not need bracing wires for the wing, using methods perfected by French engineer
Michel Wibault. However, none of the monoplane entries for the specification could meet the climb requirements. The Hawker Fury biplane was ordered instead.


On the left is the anachronistic-looking Vickers biplane COW fighter, on the right is the Westland monoplane COW fighter, both submitted for F29/27 the other 1927 specification calling for an interceptor. This was to mount a large calibre Coventry Ordnance Works (COW) gun. While it looks more modern, the Westland monoplane has bracing wires above and underneath the wings and it had a lacklustre performance. The biplane Vickers design had a much faster rate of climb to better meet the interceptor requirements.

One particular issue that plagued the early cantilever monoplanes was "aileron reversal". If the monoplane wing could not be made rigid enough, then the application of the ailerons at speed would cause the wing to bend in the opposite direction. This meant the aircraft banked in the opposite direction to that intended! Very disconcerting for the test pilot! Aileron reversal issues on even the tiny, stubby wings of the Bristol Type 72 "Racer" monoplane of 1922 caused its abandonment. The same issue scuppered the Bristol Type 95 "Bagshot" that first flew in 1927. Aileron reversal issues also plagued the Boulton Paul P31 "Bittern" twin-engined monoplane fighter; although the problem on the Bittern was eventually fixed, the delays incurred by doing so rendered the design obsolete².


One of the few advanced British inter-war monoplane designs that were not financed by the Air Ministry was the Bristol Type 72 "Racer". It was primarily built to demonstrate the superiority of the Bristol Jupiter radial engine. Even though its stubby wings were braced by wires it still suffered from aileron reversal. It was judged to be very dangerous to handle and was scrapped after only seven flights.


Another Bristol monoplane, this one fully financed by the Air Ministry, was the Type 95 Bagshot (first flight July 1927). It was designed as a bomber-destroyer, able to carry two large calibre Coventry Ordnance Works (COW) guns. It suffered from alarming twisting of the wings, causing aileron reversal. The Air Ministry paid for the development of a stronger wing. When the Bagshot was cancelled the wing design was transferred to a three-engined bomber/transport project. When that in turn was cancelled, the multi-spar wing design was used on the Bristol Bombay bomber/transport project; skinned with Alclad, the wing became the first British stressed-skin monoplane to be designed. Financed at every stage by the Air Ministry.


Yet another monoplane bomber-destroyer financed by the Air Ministry; The Boulton Paul P31 Bittern, which first flew in 1927, was designed to have machine guns in the nose-mounted on a drum, so they could be rotated to point upwards to attack enemy bombers from below. This photo shows it in its early configuration, in which it suffered from aileron reversal. The issue was eventually solved by adding extensive bracing struts to the underside of the wing. Because of its prolonged development period, its performance fell behind that of contemporary bombers and it was cancelled in 1933.

There seems to have grown up a perception that the British Air Ministry of the 1920s and 30s was composed of crusty old conservative Air Marshals who were somehow out of touch with modern trends. Nothing could be further from the truth. We are talking about a generation who had grown up surrounded by meteoric technological change, from horse transport to cars in a few short years, the introduction of the telephone and radio, the development of the aeroplane from a playboy's toy to a deadly weapon of war. This generation expected change in a way that even we in the 21st century do not. Many of their reasons for being cautious were not out of some hidebound outlook, on the contrary, it was a fear of investing too heavily in some new "fad" only to find it overtaken by some better innovation.


The Parnell Parasol was another research monoplane commissioned by the Air Ministry (AM Specification 15/28).



The Air Ministry wanted to see if a lightweight, all-metal aircraft with a small engine could replace the Fairey Flycatcher carrier fighter. In 1925 they issued specification 17/25 and selected a biplane design from Avro, the Type 584 Avocet, and a monoplane from Vickers (pictured above) the
Vickers Vireo. Both the biplane and monoplane had all-metal construction and were powered by the same 230-horsepower AW Lynx engine. They both had an armament of 2 machine guns. The Avocet biplane ended up being 15 mph faster than the Vireo monoplane (135 mph v 120 mph). The Vireo had alarming stalling characteristics, largely caused by interference drag at the wing roots. Investigating this problem helped Beverley Shenstone, the Vickers and Supermarine aerodynamicist, avoid the same issue on the Supermarine Spitfire. Again, all funded by the Air Ministry.



If the Air Ministry was prejudiced against monoplanes and thought them dangerous what were they doing putting the heir to the throne in one? The Air Ministry purchased a
Vickers Viastra metal monoplane for the use of Edward, Prince of Wales. It first flew in 1933 and was used by the Prince for about a year. It was deemed unsatisfactory because of the high noise level in the cabin (this was despite efforts to soundproof the aircraft). It was passed on to the RAF where it was used for the experimental testing of new radio equipment.

It was largely a given that the increasing power of aero engines would enable speeds where the added
parasitic drag of a biplane would become unacceptable and that monoplanes must, at some stage, begin to predominate, particularly if the monoplane wing could become entirely self-supporting, without the added drag of wires or struts. Advances were made during the 1920s, thick-winged monoplanes with internal structures of metal were built, but their increased weight meant they did not show any advantage in performance over biplane types. For example, the Beardmore Inflexible was so heavy it could not carry any useful load.


The huge Beardmore Inflexible was credited with being a bomber at the time, in fact, it was only intended as a one-off research aircraft. Its protracted development (ordered in 1923, first flight in 1928) was paid for by the Air Ministry. Note that it required a thick cable under the wings to prevent them from folding up in flight. Although the Inflexible was skinned all over with duralumin alloy, only the central "core" of the wings had what could be called a "stressed-skin" structure (and a very thick one at that), rather like a modern concrete box-girder bridge. Any passengers carried on the Inflexible were expected to constantly scan the internal structure and wings for signs of structural failure!



The equally huge Beardmore Inverness flying boat (
Rohrbach Ro IV). A parallel project to the Inflexible, they were built using construction methods developed by the German Adolf Rohrbach, who had set up a factory in Denmark after World War One to manufacture his designs. The first Inverness was built in Denmark, the second was built by Beardmore in Scotland. Testing showed poor performance and handling compared with contemporary biplane flying boats. Again, the project was bankrolled by the Air Ministry.



One of the more unusual features of the Rohrbach Ro IV were telescopic masts so that the flying boat could be sailed home in the event of engine failure!



A typical "Rohrbach" wing construction as used on the Beardmore Inflexible and Inverness. You can see the heavy plating along the central section of wing to form a simple set of self-supporting metal boxes, a very crude method of "stressed skin" construction. The leading edge and a large section of the trailing edge of the wing were constructed with traditional internal bracing trusses, albeit the wing was covered in duralumin rather than fabric.

By the end of the 1920s, advances were being made in both materials and design techniques that started to make cantilever monoplanes practical, although for large designs this usually involved having to have a very thick wing. With the he added weight of these thick wings, they had little advantage over biplane types.


The internal structures of these thick-winged monoplanes were dependent on internal stressed struts and wires, similar to the wings of a biplane.


Built to a 1927 Air Ministry specification (33/27) for a long-range mail carrier, the Fairey Long Range Monoplane had huge, thick wings.



The Fairey Hendon bomber utilised the wing design pioneered on the Long Range Monoplane. It became the first monoplane bomber to enter service with the RAF although it showed no advantage over the contemporary Handley Page Heyford biplane bomber. The Hendon could only be used from the very largest airfields available to the RAF at the time. One old RAF fitter once told me the Hendon was "Not so much a monoplane, more a biplane with the gap between the wings filled in!"



Another thick-winged monoplane ordered by the Air Ministry was the
Blackburn RB2 Sydney flying boat. Built to a 1927 specification (R5/27), its wings had a duralumin structure covered in fabric, except for metal walkways next to the engines. The heavy weight of the thick wing, coupled with the low power of its three Rolls-Royce early Kestrel F.XIIMS engines (only 525 horsepower each), meant it had a marginal performance and the single prototype suffered from bad serviceability during testing. It first flew in July 1930.



One monoplane winged flying boat that the Air Ministry spent a lot of money on was the
Supermarine Type 179, sometimes called "the Giant". It was to have had six Rolls-Royce Buzzard engines mounted over the wing, carry 40 passengers and a crew of 7. Construction of the prototype was well advanced when the UK "National" government (elected in1931 to sort out the financial crisis following the Great Depression) cancelled the project as part of a round of spending cuts. This is the final layout of the Type 179, with tapered wings and three rudders. Supermarine's chief designer, RJ Mitchell, had earlier considered using an elliptical wing layout on the Type 179, prescient of his later Spitfire design.

In 1928, the Air Ministry went as far as asking the Blackburn Aircraft company to build a biplane and monoplane that both had the same type of engines, fuselage, and landing gear so that a direct comparison could be made. The 1928 specification (18/28) was refined the following year (6/29) and the two aircraft first flew in 1932. They had very similar performances, with the monoplane being marginally faster and, perhaps surprisingly, having a higher ceiling. However, the heavy weight of the monoplane's wing meant the biplane could lift a greater weight of cargo. By the time the two aircraft were evaluated a revolution in stressed-skin aircraft construction had taken place, so the results were inconsequential.


The ten-passenger Blackburn CA15C biplane and monoplane. Built for a direct comparison of the benefits of monoplane design; there was little to choose between them. After the trials, the biplane was quickly scrapped but the monoplane saw service for trials of radio equipment and was much in demand as an aerial taxi, ferrying RAF officers home for weekend leave from Northolt aerodrome near London.

That revolution took place at the end of the 1920s when many new technologies came together to make the true cantilever monoplane jump ahead of biplane designs in terms of performance and economy.

Firstly, the design of flaps and leading edge slats evolved to the point where they were dependable. Coupled with more efficient aircraft brakes this made the landing and take-off runs of monoplanes shorter, opening up smaller landing grounds for monoplane operation. By the mid-1930s a growing realisation that aircraft sizes and speeds were only going to increase meant that the Air Ministry finally bowed to the inevitable and started to plan larger airfields with concrete runways, with all the added expense that entailed.

Secondly, commercially available aero engines started to approach 800 horsepower with the promise of 1,000 horsepower and above. Increased engine power led to increased speed. Increased speed led to increased parasitic drag, which meant the drag-reducing monoplane format became increasingly desirable. Also, as the power-to-weight ratio of fighter aircraft increased the power of the engine began to have much more of an impact on the rate of climb, slowly eclipsing the advantage of biplanes in this area. Improvements in superchargers to give greater power at height accelerated the trend.

Lastly, and most importantly, the availability of thin sheets of
Alclad, duralumin-like alloy with an outer layer of pure aluminium to resist corrosion, suddenly made possible "stress-skinned" designs; in these the metal skin of the aircraft wing itself forms a major part of the cantilever structure of the wing. This made monoplane wings much lighter and without the need for internal bracing, opened up the interior of wings to accommodate fuel tanks and retracting undercarriages. At the same time, it was found that advances in glue technology and denser sheets of plywood made wooden stressed-skin construction possible.


On the brink of the introduction of these new technologies, the Air Ministry paid for the construction of the Short S.18 "Knuckleduster" flying boat (first flight November 1933). On evaluation it was found to be inferior in performance and handling to the biplane offerings of Saunders-Roe (the A.27 London) and Supermarine (the Stranraer). Although the money paid out by the Air Ministry for the Knuckleduster went a long way towards perfecting the methods used on the later Shorts Empire and Sunderland flying boats.

The claim for the first stressed skin aircraft is clouded by national sympathies and misunderstanding. To simply cover a wing with metal or plywood does not make a wing "stressed skin". At the same time, a stressed skin design that has to use a gauge of metal that is so thick that it adds so much weight that the wing might as well have been internally stressed can hardly be regarded as a success. The first really successful multicellular, metal, stressed skin aircraft was the American Northrop Alpha which first flew in 1930. It led directly to the Douglas DC2 and DC3 and also inspired other American airliner designs. Meanwhile in Britain, almost by accident the Bristol aircraft company also stumbled onto multicellular stressed skin design when Alclad was substituted for the fabric covering of a new multi-spar wing being designed for the
Bristol Bombay bomber-transport.


The Bristol Bombay (first flight June 1935) was the first British aircraft to be designed with an entirely multicellular, stressed skin wing, although it was not the first to actually take to the air with one...


Because Bristol jumped on the promise shown by the new technology and used it in their Type 133 fighter (first flight in June 1934). The single prototype crashed before it could be evaluated by the Air Ministry. The Type 133 was a private venture by by Bristols, with no government financial support, although the Air Ministry did go on to pay for the follow-on Type 146 fighter and Type 148 army cooperation monoplanes.

All the other British aircraft manufacturers quickly adopted the stressed skin method of construction, often sending their designers to the USA to inspect the new American methods first-hand. The growing tension caused by the rise of the Nazi party in Germany led to the expansion of the RAF and new stressed skin monoplane designs began to predominate.

However, there were a couple of other methods of monoplane construction that held out the promise of certain advantages. The first of these was the geodetic method pioneered by Barnes Wallis at Vickers. This was not picked up by the Air Ministry when first put forward for specification P27/32 for a single-engined bomber in 1932. The Vickers tender was much more expensive than the offerings of other companies and the Air Ministry went for the stressed-skin Fairey Battle instead. However, the Air Ministry did sponsor the geodetic fuselage of the Vickers Type 253 biplane which helped cut the development costs of the Vickers Type 246 monoplane which ended up being adopted as the
Vickers Wellesley bomber, leading to the Wellington, Warwick and Windsor bombers.

The other method of monoplane construction was the "monospar wing" designed by Swiss-born Engineer H.J. Steiger. He had been involved in the Beardmore Inflexible project and had become convinced he could do much better. He designed a wing with a strong single duralumin Warren girder spar that was braced by tie rods. The resulting wing was covered in fabric, which might seem very old-fashioned today, but at the time its light-weight, ease of construction and low cost held out great promise. The Air Ministry paid for the construction of the first wing of this type, which was exhibited at an exhibition in London in 1929 before going for tests by the Royal Aircraft Establishment (RAE). The design led to the formation of the
General Aircraft Company which designed a series of small twin-engined civil aircraft in the 1930s. The Air Ministry would go on to pay for the building of a larger monospar wing that was fitted to an experimental Saro Cloud flying boat. This in turn led to the huge four-engined Saro A.33 flying boat which used a monospar wing.


The Saro Cloud (K2681) fitted with the experimental monospar wing. What looks like a smaller wing lower down on the fuselage are sponsons used instead of wingtip floats.



General Aircraft
ST-12 "Monospar" VH-UTH preserved at the Newark Air Museum. Note the exposed spars running from the side of the fuselage into the wings. The simple and light monoplane wing design enabled the various marks of "Monospar" to be produced at a price that filled a niche in the 1930s civil aircraft marketplace. The initial development of the monospar system had been directly supported by the Air Ministry.



The huge
Saro A.33 used the "monospar" wing structure. It was built to meet the same specification as the Sunderland flying-boat. It had large sponsons instead of wingtip floats.

Thus it is evident that there was no "ban" on monoplanes by the Air Ministry in the 1920s and early 1930s. On the contrary, the Air Ministry actively paid for research into monoplane wings and also paid for the construction of many monoplane aircraft tendered for specifications. The fact that few monoplanes made it into service during that period just reflects the fact that, with the then-current construction techniques, monoplanes showed no advantage over biplanes. The Air Ministry was evidently exasperated by the lack of progress on monoplane designs, to the extent that they considered specifying "monoplanes only" for their
F7/30 specification for a new fighter. The advances that came to the fore in 1928-1932, particularly the availability of thin Alclad sheets, made monoplanes jump ahead of biplanes in performance and economy.

So where does the myth come from? Because of the constraints of the British
Official Secrets Act, the officers and civil servants involved in the drawing up of specifications and selecting aircraft for use could not talk about the process. Information that was available to journalists and aviation pundits therefore largely came from the aircraft manufacturing companies. Those companies naturally presented their offerings in a good light, while often disparaging the Air Ministry. They explained away the rejection of some of their monoplane offerings by suggesting an aversion to monoplanes within the Air Ministry and that the ban on monoplanes that had briefly existed in 1912 was essentially still in force into the early 1930s.³ This was not helped by a certain element within British aviation journalism, typified by CG Grey editor of The Aeroplane magazine, that were very critical of the Air Ministries' role in specifying aircraft and wanted a more "free-market" approach to aircraft procurement and a return to the "survival of the fittest" policy of the RNAS in the early years of WWI. Thus, starting in the 1940s and continuing through until the early 1980s, when all the various "definitive" histories of aircraft companies were written, there grew up this myth of prejudice against monoplanes by the Air Ministry. This perception was magnified by the assertion that both the Spitfire and Hurricane had been private-venture projects by Hawker and Supermarine respectively, accepted by a reluctant Air Ministry only at the last minute. In fact, both the Spitfire and Hurricane were seized upon in their early design stage by the Air Ministry as just the sort of monoplanes they had been hoping for and their design and construction were fully financed by the government.

There were, perhaps inevitably, a few members of the RAF who retained a personal suspicion of or prejudice against monoplanes. For example, William Forbes-Sempill, the notorious
"Master of Sempill", who had a hand in the testing of the Beardmore Inverness flying-boat, is reported to have expressed some distinctly derogatory comments about monoplanes. However, there seems to be no evidence that anyone in the Air Ministry actually concerned with selecting aircraft in the 20s and 30s held such views. Some online articles attribute Hugh Trenchard with a dislike of monoplanes, but they do not offer any references to back up this claim and it seems that it was Trenchard who specifically asked for more Morane-Saulner parasol monoplanes for the RFC in 1916.

For all the money put into monoplanes by the British Air Ministry, it is ironic that the explosion of stressed-skin monoplane construction took place in the USA. Here it was driven by commercial, rather than military considerations. By subsidising air-mail routes, the US government had provided the ideal conditions for commercial airlines to thrive. The purely financial considerations of economy and faster journey times caused the revolution in monoplane airline design that left the military designs of all the major powers playing catch-up.


Two of the American airliners that caused such a sensation in the 1930s. On the left is the Boeing 247 (first flight February 1933), on the right is the Douglas DC-2 (first flight May 1934).

It was only in the late 1980s that the records of the Air Ministry for this period started to become available under the "50-year rule". Some historians (notably Colin Sinnott) have attempted to put the record straight but the legacy of all those aviation books written in the 40s through until the 80s still hangs heavily around the history of the period and unfortunately the myth still gets repeated as fact, even in newly published articles and books.

Alclad: the turning point in metal stressed-skin design.

Aluminium (UK spelling) is a lightweight metal (one-third the weight of steel), abundant in the Earth's crust. It was only isolated in 1825 and the first industrial production began in 1856, although increased and cost-effective production only started in 1886 with the use of the
Hall–Héroult process. The light weight of aluminium and its resistance to corrosion makes it desirable for aviation use but in its pure form it is not strong enough for major structural items or the skin of aircraft. In 1909 (not 1903 as is commonly cited) the German metallurgist Alfred Wilm patented an alloy of aluminium, copper and certain other elements that was as strong as steel (German patent number 6485/10). This was then produced by the German company Dürener Metallwerke AG, who called it by the trade-name duralumin. However, Wilm's development was built on earlier work by another German, Conrad Claussen, who had developed his own form of strong aluminium alloy and patented it in 1905 (British patent number 19282/05). He sold the rights to produce his alloy to the British Vickers armaments company. From 1915 the British alloy was produced by James Booth & Co of Birmingham which was jointly owned by Rolls Royce and Vickers.

Both the German and British forms of "duralumin" were at first primarily used for airship construction, the German Zeppelin airships were only made possible by its use. Vickers used it on various airship projects from the ill-fated Mayfly of 1911 through to the R100 of 1929. The German form of duralumin made possible aircraft like the all-metal
Junkers D1 at the end of WW1. Vickers and other British aircraft manufacturers were much slower to produce aircraft designs that incorporated it (although Booth's products were used in the construction of both the Beardmore "Inflexible" and "Inverness" monoplanes). In the 1920s, the French aircraft designer Michel Wibault had to approach Vickers to secure supplies of the British version of "duralumin" for his innovative cantilever monoplane designs. Vickers latched on to Wibault's methods and licensed them to produce their range of duralumin skinned monoplanes (the Scout parasol fighter, Vireo lightweight fighter, Jockey fighter and Viastra airliners).

But duralumin has one major weakness; it is subject to corrosion. That corrosion can occur suddenly and without warning, sometimes starting deep within the interior of metal parts if cracking has occurred. This made aircraft skins made of duralumin a bit of a liability; designers had to build in the ability to take off the skin of an aircraft if it started to suffer from corrosion. Equally as troublesome was building in the ability to inspect the interior of wings to check for corrosion in the first place.

In 1927 a new form of aluminium alloy sheet appeared in the USA; called
Alclad, it was a sheet of duralumin-like alloy but with its surface covered with a layer of pure aluminium. Pure aluminium was a barrier to corrosion, so effective that the re-skinning of an aircraft during its normal working lifetime became unlikely. Within a few years, this new sheeting revolutionised the aircraft industry, first in the USA and then in the rest of the world. It allowed the cheap construction of lightweight monocoque fuselages, engine cowlings and most importantly stressed-skin monoplane wings. In Britain a version of Alclad was produced by Imperial Chemical Industries (ICI) at their factory near Swansea in Wales. Their version had the trade-name "Kynal", or more specifically "Kynal-Core".



Notes

¹ Articles that refer to the monoplane ban of 1912 often list the wrong accidents as being its cause. The committee was only concerned with the unexplained break-up in-flight of the two monoplanes operated by the Royal Flying Corp. Other monoplane crashes that involved civilians or that could be explained by pilot error were not considered.

² The full story of the Boulton Paul P31 Bittern is an interesting one (Les Whitehouse's book " Boulton Paul 1917-1961" tells it well - see sources below). When the performance of the Bittern began to lag behind that of other Aircraft its designer (J D North) looked at ways to streamline it to increase speed. He came up with a wing-profile ring to surround the cylinders of its radial engines. The Bittern was the first aircraft to fly with such a cowling around its engines. When it was discovered that Dr Townsend of the National Physics Laboratory had patented a very similar system only a few months before, Boulton Paul purchased his patent from him. For a brief period such cowlings were known as "North-Townsend rings" or "Boulton Paul -Townsend rings". - Today they are remembered only as
"Townsend Rings".

³ One particular source for the stories of Air Ministry prejudice against monoplanes was
"The Book of Bristol Aircraft", published in 1946 by Harborough Publishing Ltd and edited by D.A. Russell, it was produced with "the cooperation and approval of the Bristol Aeroplane Company Ltd". It was a follow-on to the wartime "Aircraft of the Fighting Powers" series. The book was sponsored by Bristols, who purchased quantities to give away to staff and as promotional give-aways for the company. Naturally, it was written to show Bristol in the best light possible, while the rejections of various monoplane projects were inevitably blamed on the Air Ministries' short-sightedness towards monoplanes.


In the TV show "Scrapheap Challenge" (US version called "Junkyard Wars") 2003 special double episode "Flight of the Century", teams from the USA, France and the UK were challenged to build aircraft using only the technologies available before WW1. The US and French teams elected to build monoplanes while the UK team built a biplane - the results are very illuminating. The episode is available on YouTube at
<this link>.

Sources

"
That Ban - The Outlawing of Monoplanes, 1912": An article by Paul R Hare in issue 104 (March/April 2003) of Air Enthusiast magazine.

"The RAF and Aircraft Design 1923-1939": By Colin Sinnott, published by Frank Cass. ISBN 0 7146 5158 3. It is a brilliant source that deserves to be more widely read. The book presents a picture of the Air Ministry, in the late 1920s and early 1930s, being exasperated by the British aviation industry repeatedly offering biplane designs. Moreover, they found it even more frustrating that when British monoplanes were designed and tested, they often performed worse than the biplanes.

"Bristol M.1C" - An article in Issue 124 (Winter 2005) of Air-Britain Aeromilitaria magazine. Unattributed, probably by the editors, James Halley and Ray Sturtivant. It has a listing of all the Bristol M.1B and M.1C aircraft built.

"Beardmore's Heavy Metal Monsters": An article on the Bearmore Inflexible by Philip Jarrett in the March 1990 edition of Aeroplane Monthly magazine.

"
Boulton Paul 1917-1961- Aircraft, Projects and Studies" : By Les Whitehouse, published by Crecy in 2021, ISBN: 9781910809488.

Flight Magazine of September 29th 1921 carried an article about the de Havilland DH29 monoplane. It was a little sceptical of the notion of cantilever monoplanes. The article was reprinted in "de Havilland - The Golden Years - 1919-1939" published by the IPC business press in 1981.

"R&D and competition in England and the United States: the case of the aluminum dirigible":
An article by Margaret BW Graham in the June 1988 edition of Business History Review. Online copy at <this link>.

"Three? One? Two? Vickers and the Viastra": An article by Arthur WJG Orde-Hulme in Air Enthusiast No 123 (May/June 2006).

"English Electric's Light Touch - The Wren Ultra-Lights" : An article by Bob Dunn in Air Enthusiast No 114 (Nov/Dec 2004).


Futher Reading

I strongly recommend Reg Winston's book
"The Right Flyer". It tells the story of the different approaches to flight taken in the USA and France at the dawn of heavier-than-air, powered flight. Published in 2017 by Faustroll. ISBN: 978-0-9569811-0-3.