The CLAs

CRANWELL

Nick Comper joined the Boys’ Wing RAF College Cranwell on 7 October 1922, in charge of the Metallurgical Laboratory.

Flying Officer Comper (he was promoted to Flight Lieutenant on 30 June 1923) lost no time in bringing his skills and enthusiasm to bear on his new job.  From the Boys’ Wing magazine we find that he lectured to the Engineering Society on 10 January 1923 on the “Evolution of Aircraft”, and on 5 March to the Model Aircraft Society on “The Elementary Theory of Flight”.  He was also the inspiration behind the formation of the Model Aircraft Society, becoming its Secretary and Treasurer, but perhaps most importantly, it was on his personal initiative that the Boys’ Wing Glider Club was formed in January 1923, from which later developed the Cranwell Light Aeroplane Club (CLAC).  Over the next 6 years the CLAC produced 4 designs under Comper’s direction that would do much to enhance his reputation as an innovative and influential designer.

Although construction of a glider by the CLAC commenced almost immediately it was soon decided to concentrate on powered light aircraft.  Work had already begun on the C.L.A.1, a single seat machine when the Air Ministry competitions for 1924 were announced and further progress abandoned in favour of building a new design.  The club was, however, in something of a quandary, it did not have the resources to wait for clarification of the competition rules and yet by starting construction too soon they would be unable to optimise the design.  Inevitably, when the detailed requirements were issued, it was discovered that the C.L.A.2 with its low top speed and side by side seating was not best suited to the competition.  Even so, the C.L.A.2 fitted with a Bristol “Cherub” engine and flown by its designer gave a very good account of itself at the Lympne trials held in September 1924, and, to the surprise of many, won the Reliability Prize of £300.  It was not too far-fetched to suggest that the CLAC had single-handedly successfully challenged the aircraft industry.  The Aeroplane was moved to comment:  “……it is the nearest approach in England to the display of a private, as opposed to a trade effort in the sporting and experimental side of flying on lines which have been so successfully encouraged in Germany, and if the Air Ministry is really sincere in its desire to encourage Light Aeroplane Clubs it will go out of its way to give a little extra encouragement to those who are ready to follow the Cranwell example…..”  All in all, it was a magnificent achievement and whilst a great deal of credit was clearly owed to the engineering team and members of the CLAC, notably Flight Lieutenant Pack (construction) and Flying Officer Cashmore (engine), there was no doubt that it was Nick Comper’s “…….infectious enthusiasm and untiring zeal in pursuit of a great idea……..” that had been the driving force.  (Boys’s Wing Magazine, Apr 25, pages 21-28).

The C.L.A.2 was unfortunately destroyed later in the year when under evaluation by the Air Ministry, but the compensation payment and prize money permitted a new design, the C.L.A.3, a single-seat parasol monoplane, to be developed for the 1925 Air Ministry trials; also to be held at Lympne.  Once again, the CLAC’s efforts were successful, the aircraft flown by Nick Comper making the fastest time in the performance tests as well as winning the International Single-Seater Light Aeroplane Scratch Race and coming third in the Grosvenor Challenge Cup Race and in the Private Owners’ Handicap.

Buoyed by their success, it was only natural for thoughts to turn to the 1926 Lympne competitions, sponsored by the Daily Mail, but again, the club was faced by a quandary.  Captain Douglas Pobjoy, who had arrived at Cranwell as the Boys’ Wing Education Officer in 1924 and with considerable experience in engine design with the British Aeroplane Company, had been so impressed by the work of the CLAC that he had undertaken the design of a lightweight seven cylinder radial engine suitable for the club’s aircraft.  The new, as yet untested, Pobjoy “P” engine offered the prospect of an unrivalled power-eight ratio, but it was uncertain whether it would be ready in time.  By way of a compromise, the CLAC decided to build two aircraft for the 1926 trial, one (the C.L.A.4A) powered by the Pobjoy “P” and the other (the C.L.A.4) by an improved Bristol “Cherub”.  Other than the power plant, and appropriate structural provision, the designs were identical, comprising a 2-seat all wood biplane with an inverted sesquiplane layout and a fuselage of similar construction to the C.L.A.3.

It is difficult to avoid the conclusion that this time the club had stretched itself a little too far, notwithstanding the enthusiasm of its membership. The timetable for constructing two aircraft was extremely tight, even without the distraction of preparing the C.L.A.3 for the 1925 Kings’ Cup Air Race.  With hindsight it seems almost inevitable that the 1926 season should be beset by problems – some of which might have been resolved had time been available for more testing – the most significant being the breakdown of the Pobjoy “P” during type testing at Farnborough.  As a result, only the C.L.A.4 participated in the trials but was quickly eliminated because of technical problems.

Sadly, the disappointments of the 1926 season also marked the end of the CLAC’s existence.  The Boys’ Wing had moved to Cranwell in the first instance because of the lack of permanent accommodate at Halton, but by early 1926 Halton was ready and the transfer of the Boys’ Wing, or No 4 Apprentices Wing as it was now formally known, could not be delayed further.  Nicholas Comper remained behind in a supernumerary capacity, presumably to wrap-up the season’s work, and it would not be until early November that he was posted to Felixstowe on the staff of the Marine Aircraft Experimental Establishment.  Coincident with this move, the CLAC’s name was changed to the Felixstowe Light Aeroplane Club, but no designs appear to have been completed under the new title.  Nick Comper was to remain at Felixstowe until he resigned his commission in April 1929 in order to pursue his developing commercial interests.

In concluding the story of the CLAC it would be remiss not to mention one further aspect.  Amongst the Boys involved in the construction of the C.L.A.2 was Frank Whittle, who was also a leading figure in the Model Aircraft Society.  One of the attractions was that Nick Comper would take one of the members as a passenger when he was doing flying practice.  Thus it was that Frank Whittle made his first flight in an aircraft.  He later recalled that he had devoted hundreds of hours to the club and found it “…….difficult to over-emphasise the importance of the Model Aircraft Society on my subsequent career….” (Sir Frank Whittle, ‘Jet’, 1953, pages 16-17).  According to a fellow apprentice, Frank Whittle was a particular favourite of both Comper and Pobjoy and contributed a great deal to the CLAC’s activities.  (Geoffrey Ellis, Tool Box On The Wing, pages 17-33).  It is tempting to speculate on the influence of these talented and visionary engineers on the 16 year-old Frank Whittle.  Their example cannot have failed to inspire him in his subsequent endeavours and, surely, of those at Cranwell in the 1920’s, it was not just Nick Comper who could be said to have possessed “…….untiring zeal in pursuit of a great idea?” (Source: Group Captain Peter Dye - RAF Museum Cosford)

The CLA 1

During the latter part of 1923 Comper at 26 years of age gathered the staff and apprentices of No. 4 Apprentices wing of the RAF College at Cranwell to form the Cranwell Light Aeroplane Club.

The first plane they designed was the CLA1.  It never progressed beyond the drawing board and the plans have been lost.

Extract from an article written by Air Vice Marshall R M Austin:

The Cranwell Light Aircraft Club was formed in 1923 as a glider club and a glider was constructed, but the members believed that powered aircraft offered greater scope and Comper, who had become the club's designer, started work on a single seat machine which was given the designation CLA 1.  At the that time, the Air Ministry (which was then responsible for both civil and military aviation) was actively encourgaing light aviation and with the object of finding a suitable type of 2-seat light aeroplane for use in flying clubs, it put up £3,000 in prixe money to be competed for at a Light Aeroplane Competition which the Royal Aero Club was to organise at Lympne, in Kent, at the end of September 1924.  The Cranwell Club set their sights on this competition, somewhat handicapped by the fact the rules had not yet been fully defined, but knowing the broad requirement.

The CLA 2

They then set to work to build a robust, low cost, low-powered trainer that would be cheap to build and economic to operate.    The result was a crude boxy aeroplane of little beauty.  Its side-by-side seating was unusual for the time   This meant the fuselage was twice the normal width and a consequent increase in drag.  To offset this the forward fuselage "longerons" converged almost to a point at the engine mounting.

The fuselage was of normal wire-braced construction with ash longerons in the front section.  All cockpit controls were interconnected, enabling the aircraft to be flown from either seat.  The 32 hp Bristol Cherub engine was mounted on a minute bulkhead.  The entire aircraft was fabric covered.

After taking part in several trials at Lympne, eventually it won £300 for its continued lapping over ten hours in a reliability trial.  It was at the cost of all but destroying its Cherub engine.  But all agreed that Comper's achievement was outstanding having flown a total distance of 762.5 miles having been airborne for 17 hours 53 minutes.

The CLA2 only survived a short while after these trials in 1924  but the prize money and additional funds from the Air Ministry funded the building of the next plane in the class. 

Extract from an article written by Air Vice Marshall R M Austin:

Comper turned his attention to a new machine, the CLA 2.  He took the brave step of opting for side-by-side seating which, for all its instructional advantages, would cause increased drag and would limit the performance achieveable with the specified 1100 ccengine.  The CLA 2 was a biplane with a 29ft 8in span upper wing and a smaller, 22ft span lower wing.  The engine was a twin-cylinder air-cooled Bristol Cherub which produced 30 hp from its 1096 cc; the fuel tank held 4 and a half gallons.  The wings and fuselage were constructed primarily of spruce with fabric covering.

Once built and tested, the CLA 2 was registered as G-EBKC and taken to Lympne in July 1924.  It caused some astonishment and perhaps a little amusement because, having been designed for robust utility rather than peak efficiency, it looked fat, heavy and unwieldy when compared with the other competitors but, when it was weighed and found to be just 510 lbs empty, it was by no means the heaviest.  It was, however, the only aircraft with side-by-side seating and the only amateur machine in the competition.  

On September 26th, Flt Lt Comper and the reserve pilot, his (wife's) cousin Flt Lt (Percy) Mackay, carried out a satisfactory 15 minute test flight and the next day the CLA 2 completed the test which required the ground crew to dismantle the aircraft, pass it through a 10 ft test gate to show its practicability of getting it from a field, and re-erect it.  The par time for the whole exercise was amaximum of 2 hours but the CLA 2 completed the exercise in only 79 minutes, a tribute to Flt Lt Pack who had designed the dismantling mechanism. 

The CLA 2 handled well but was under-powered.  When it demonstrated its speed range, the humourists alleged that on a slow run it was 2 mph faster than its average speed round the high speed course!  The Cranwell team decided to concentrate on the reliability prize which entailed flyingfor a minimum of 10 hours and covering at least 300 miles without replacing any part of the aircraft or engine.  This proved to be a wise decision because the aircraft covered 61 laps at 42 mph, an aggregate distance of 762 miles in 17 hours and 53 minutes; the CLA 2 wonthe Reliability  Prize of £300, a remarkable achievement for an aircraft designed and built by a flying club.  In addition to Comper, many officers and airmen played a part in this success.  There was also a small team of apprentices; one of them was called Whittle.

To mark the event, the Officers' Mess presented Comper with a silver model of the CLA 2 and the Shell Mex Compony presented a similar model to the club.  It is now held in York House Officers' Mess and graces the table on Dinner Nights.

The CLA 2 crashed later that year whilst under evaluation by the Air Ministry at Martlesham and compensation money received by the club, together with the £300 prize money, enabled them to make plans for the 1925 Lympne meeting.  Comper has his eye on the speed competition and began to work on a machine which he hoped would reach 100 mph;  it was to be the CLA 3.

The CLA 3

This design was a minute single-seat high wing monoplane powered by a 32 hp  Bristol Cherub engine.  Its streamlining attracted much comment.  Frank Whittle and Philip Sassoon are thought to have helped in its construction of a half scale model of the plane.

The rear fuselage had a Warren Girder construction.  A wirebraced construction was used forward of the cockpit.  The wing had no dihedral and was carried above the fuselage on four steel struts, braced at either side with two steel tube wing struts.

At the 1925 Lympne trials it finished second overall, even though the plane was barely ready to fly at the time.  It was the only new aircraft to take part in those trials.  Comper later achieved third place in the  Grosvenor Challenge Cup Handicap.

The CLA3 was scrapped in 1929, the year Comper founded his aircraft company at Hooton.

(Source: Extracts from Aeroplane Monthly, August 1980)

Extract from an article written by Air Vice Marshall R M Austin:

The CLA 3 was a single seat monoplane with a parasol wing of only 21 ft span and Comper retained the Bristol Cherub engine.  Empty weight was a mere 325 lbs.   The aircraft (G-EBMC) completed the initial flight trials at Cranwell and it was fortunate that there was no need for any major adjustments because there was no time available before it had to be transported by rail to Lympne in late July.  In his first race of the competition, Comper had to retire with an overheating engine but the problem was solved by making extra holes in the cowling and the aircraft was ready for the next race, the International Single Seater Scratch Race over 50 miles.  The CLA 3 won with an average speed of 82 mph and it went on to win the 3 kilometre speed test at 87 mph.  In addition, it was well placed in some of the other races in 1925 and was a most successful meeting for the Cranwell Club.  The other aircraft to have a successful meeting that year was the RAE Aero Club's Hurricane (no relation to the WWII fighter) flown by Flt Lt JS Chick, a well known RAF Rugby player.  The CLA 3 and the Hurricane were the only amateur produced aircraft at the meeting. 

The CLA 4

In 1926 Comper built the CLA 4, specially designed for the Lympne trials.   Two were constructed, one powered by a Bristol Cherub III engine and the other by a revolutionary new engine designed by another Cranwell officer, Captain Douglas Rudolph Pobjoy. 

In competitions and trials the CLA 4 was dogged by ill fortune.  On one occasion it did win a race for planes that had previously been eliminated from trials.  Even this nearly ended in failure for as Comper circled at the end of the race his engine cut out and he was forced to make a "dead-stick" landing in a field outside the aerodrome.  The plane was undamaged and the engine failure was diagnosed as being a bluebottle fly that had entered the air intake.

Extract from an article written by Air Vice Marshall R M Austin:

After celebrating their success (with the CLA 3), the Club looked forward to the 1926 competition.  The rules stipulated a 2-seater with dual controls and an airspeed indicator which could be read from both cockpits. The aircraft would be required to complete not less than 20 flights covering an aggregate distance of 2,000 miles at not less than 50 mph and carrying a load of 340 lb.The earlier limit on engine capacity had wisely been changed to a limit on engine weight )to be less than 170 lbs) and, as in previous years, the wings had to fold.  Comper returned to his slide-rule and drawing paper and the CLA 4 was born.  At this time another Cranwell instructor entered the story: Capt Douglas Pobjoy BSc, who had arrived in 1924 as an Education Officer on No 4 Apprentices Wing, was so impressed by the work of the Cranwell Light Aeroplane Club that he determined to design and produce an engine which was optimised for their machines.  The result was a 7-cylinder air-cooled radial engine which Pobjoy designated the "P".  Power from its 2 1/2  litres   was expected to be 60 hp and yet the weight was only 100 lbs.  (About 600 Pobjoy engines, including the Niagara series, were eventually built  - but that's another story.)   The appearance of the Pobjoy engine presented the Cranwell Club with a quandary: should they plan to use the new Pobjoy engine which was only a paper design at the time but which promised an excellent power/weight ratio and a very low fuel consumption or should they stick with the proven Bristol Cherub?  They decided to build two aircraft, a CLA 4 (G-EBPC) with the Pobjoy engine and a CLA 4A (G-EBPB) with the Bristol Cherub (although both were eventually completed with the Cherub).

The CLA 4A's fuselage was similar to that of the CLA 3 but was 4 ft longer to accommodate a second cockpit in tandem.  It was a biplane and, unusually, the upper wing span was smaller than the lower, 22 ft compared with 27 ft 4 in (technically an inverted sesquiplane!); ailerons were fitted to the lower wing only.  Empty weight was 450 lbs.  A practical point about the design was the location of the front cockpit wasz behind the trailing edge; upward visibility  - often a problem with biplanes - was therefore good for both occupants.

Only a few weeks before the 1926 competition, the Pobjoy P engine suffered a minor failure whilst on type testing trials at Farnborough.  There was insufficient time to correct the problem before the Lympne meeting and the Club lost the potential benefit of a fine engine.

On arrival at Lympne, Comper declared to the judges that the CLA 4A had a minor problem with an undercarriage leg; a replacement part was en route from Cranwell.  There was no protest from the judges but, when the leg bent during the competition and the replacement was fitted, the CLA 4A was promptly disqualified under the very strict rules governing aircraft and engine rectification.  The Cranwell team were horrified, as were other contestants  who suffered a similar fate.  Sp strong was the feeling against these decisions that a strike by the pilots was proposed but was abandoned as undignified in view of a recent general strike of transport workers and miners.  After witnessing so much bickering the St John's Ambulance men, after a day with nothing to do, quipped that they had better go to the Steward's tent where they would probably find more blood spilt than in crashes!  In spite of extreme reactions to their judgements, the officials were adamant and the Cranwell team had to be satisfied with a £50 prize for winning the race for those had been eliminated in the trials.  It was a great disappointment after so much hard work.    

THE ONLY SURVIVING CLA 4

In Canada a flying club built a CLA 4, the only one constructed outside of England, and is the sole survivor of its type.  In its original form it used a Blackburn Thrush 3 cylinder radial engine (which is in the Alberta Aviation Museum collection) but was re-engined with a more powerful American Velie 5 cylinder radial due to altitude and higher weight of pilot's in Canada.  The plans (the only surviving set) are held by the Want family, descendents of Alf Want who built this aircraft.

After the Great War there was a group in Edmonton that wanted to form a flying club.  It was at the time the Lympne Trials were taking place in England and it was assumed one of those aircraft would be the winner.  One of the members was an ex-Cranwell instructor who told the committee that he had heard the trials were "fixed",  and that the CLA-4 would be chosen so that the Air Ministry could then avoid paying a royalty fee to the Cadets who had designed it.  But he, the ex-instructor, said he could get a set of plans for them and if they purchased some fittings and engines they could build their own training planes and be ahead of everyone else.  This they did, ordering two sets of fittings and 2 Thrush engines. 

The building went on apace until they met the requirements for a Flying Club and applied to Ottawa.  They were the first Flying Club approved under the Commonwealth Scheme in Canada (1927).  But interest in completing the CLA-4 waned as everyone wanted to fly the Moths.  Alf Want, who had done the major work on the project, purchased the aircraft, plans and fittings and finished the aircraft for his own use.  As it was homebuilt it didn't at the time require a registration. 

It was flown locally from about 1930 to 1934 when it had an accident in a wind storm and was damaged.  Alf collected the pieces intending to re-build it, but never got round to it.  He donated the CLA 4 to the Alberta Aviation Museum in the 1980's where it was intended to be re-built to flying condition for local flights, but when Mr. Want died the project changed, as it was realised this was the oldest surviving aircraft built in Edmonton.  It is now displayed with the Velie engine half fabric covered to display the work that went into building a wooden aircraft of that period.  The Thrush engine is displayed beside it.  The second Thrush was taken from the Flying Club hangar without Mr. Want's permission for use in a powered glider, and is now part of the Reynolds-Alberta Museum collection in Wetaskiwin.