The Honourable Company of Air Pilots visited the team at their base at North Weald Airfield

On 27th April, members of the Honourable Company of Air Pilots, a Livery Company of the City of London, visited the team at North Weald Airfield. The Company’s activities are centred on sponsoring and encouraging action designed to “ensure that aircraft are piloted and navigated safely by individuals who are highly competent, self-reliant, dependable and respected.”

Following the visit, Group Captain Tom Eeles wrote an article in the Air Pilot magazine and has been kind enough to let us publish it here.

 

THE FOLLAND GNAT – AN APPRECIATION

 Sixty years ago, on 11 August 1954, a tiny swept wing jet fighter made its first flight. It was the Folland Fo 139 Midge, powered by a Viper turbo jet. It was the precursor of the definitive version, the Folland Fo141 Gnat, which first flew on 18 July 1955. The Midge and the Gnat were the brainchildren of W E Petter, the Managing Director of Folland Aircraft Ltd. Petter was a very talented designer who started work with Westlands, where he designed the Whirlwind and Welkin twin engine fighters. After the end of World War 2 he moved to English Electric where he designed the famous and successful Canberra; he was also involved in early work on the P1, which subsequently became the Lightning. At Follands he became increasingly concerned with the escalation in cost and size of the emerging generation of jet fighters; his solution was a small, agile fighter that would cost far less to purchase and maintain. In an advertisement in the September 1954 issue of Aeroplane magazine Follands claimed that ‘Twenty light fighters, fitted with all essential flying, navigational and armament equipment, can be built for the price of six standard fighters.’ As for fire-power, it was claimed that ‘The five light fighters produced in the time needed for one standard fighter can bring to bear 10 x 30mm cannon instead of the 4 x 30mm cannon, or 6 x 0.5 in machine guns of the standard fighter’.

 

The Gnat was powered by a Bristol Siddely Orpheus turbo jet and had a built-in armament of 2 30mm Aden cannons. An order for six Gnats was placed by the Ministry of Supply with a view to using the aircraft to replace the Venom in the day ground attack role but subsequently the RAF did not order it, preferring a ground attack version of the Hunter. Twelve Gnats were delivered to Finland and two to Yugoslavia, but the main order came from India which subsequently involved license production by Hindustan Aircraft Ltd in large numbers. However, in the late 1950s the RAF was seeking to replace its advanced jet trainer, the Vampire T11, with a more modern design suitable as a lead-in to the advanced aircraft it hoped to bring into service in the 1960s, such as the TSR2, Lightning and Hawker’s supersonic VSTOL fighter project. In the event only the Lightning made it into service. Follands offered a two seat version of the Gnat fighter and in 1957 an order was placed for a batch of two seaters to be used as advanced trainers. The first one flew in August 1959. The new generation of front line aircraft were to be equipped with an advanced instrument display known as the Integrated Flight Instrument System (IFIS). Given that this system had already been installed in the Hunter T7, with its side-by-side seating favoured by the RAF for flying training, it therefore seemed an odd decision to opt for a trainer with tandem seating and only a partial IFIS installation. Perhaps it was a consolation prize for Follands, who had failed to get the RAF to order the fighter version.

 

The Gnat T1 entered service with the RAF at CFS in 1962 and at 4 FTS RAF Valley shortly afterwards. In August 1963 your Hon Editor found himself on the second course along with a number of his colleagues recently graduated from the RAF College Cranwell. The Gnat T1 was a tremendous advance on the Vampire T11. It was very small, with a wingspan of just 24 feet and length of 37 feet, its maximum permitted speed was 0.90M below 11,000ft and 500kts above; Pilot’s Notes stated that supersonic flight could easily be achieved in a dive and that ‘well-contoured airframes in steep dives approach 1.3M.’ It also looked terrific after the rather stubby Jet Provost we had flown previously. However, whatever Petter’s original concept for simplicity had been, the aircraft was technically complex with much packed into the tiny airframe. Its ailerons and slab tailplane were fully powered but the longitudinal control system was particularly complicated. There were two different mechanisms to govern the gearing between control column and tailplane movement, a cam mechanism and a Q feel mechanism. In addition there was an automatic tailplane datum shift mechanism which compensated for the large Centre of Gravity and trim change that took place when the landing gear travelled. Plenty to go wrong here ! Manual reversion in the event of hydraulic failure was available. The slab tailplane would freeze in its last position following hyraulic failure but longitudinal control was achieved by unlocking small elevators from the slab and moving the slab (slowly) through use of a standby electric trimmer. In this condition the automatic datum shift did not work, so plenty of handling challenges here for the student, especially when carrying out a practice forced landing. The Instructor was able to select the hydraulics off by use of a cockpit selector; this was usually done in the middle of your aerobatic sequence, with predictable disastrous results. Another innovative feature was the landing gear, the doors functioning as the airbrake when partially extended. Moving the gear selector lever from up to its first detent gave the airbrake selection, moving it further aft to the next detent selected gear down and turning it through 90 degrees and moving it all the way back selected emergency down. Beware selecting only airbrake in the rush to do your downwind checks !

 

The Gnat seemed always to be short of fuel; it carried only 383 gallons (or 3063 lbs) of AVTUR and used it up very quickly. Despite a complex arrangement of tanks – nine in the fuselage and two in each wing – the system worked pretty well. With its narrow track landing gear it was tricky to handle in a cross wind, especially on a wet runway. The runways at Valley were usually wet and the runway that faced the prevailing westerly wind was too short for the Gnat ! With its relatively long heavy fuselage and short wings the Gnat could be prone to suffering from inertia coupling at high rates of roll. To prevent this, control column lateral movement was restricted by airspeed operated switches above 150 kts which meant full aileron deflection could not be achieved. You could sense these switches operating as you came round finals at 150 kts in the form of tapping on the control column. It didn’t take long before someone on the Red Arrows discovered that if the fuse controlling these switches was removed very high roll rates could be achieved throughout the whole flight envelope. When Higher Authority heard about this practice an order was issued to the effect that the fuse was never to be removed before flight. The Reds got round this irritating restriction by simply blowing the fuse and then re-installing it, thereby conforming to the letter if not the intention of the order.

 

What was it like to fly? It was a joy to fly from the front seat, despite the small size of the rather snug cockpit. With the long pitot tube sticking out in front of you it was like riding a rocket propelled witch’s broomstick. It was exceptionally manouverable and light on the controls, formation flying was a bit twitchy until you got used to it. It was not so nice instructing from the back seat when all you could see in front of you was the back of the student’s ejection seat. You hoped for for a light crosswind from the right on finals so you could see both the runway and keep an eye on the sector ASI mounted on the left hand side of the rear seat coaming. Landing away from home base needed forethought, as there was no internal starter and an external gas turbine starter was needed, not always available at all airfields. The Gnat suffered from the rough and tumble of flying training and the salt-laden climate of Anglesey. With its complex systems packed into such a small airframe serviceability was not good. A  Hunter squadron had already been formed at Valley to make up for the Gnat’s poor serviceability, to cater for those pilots too tall to fit in the Gnat’s cockpit and to train students from overseas who might have difficulty understanding Gnat flying techniques.By the mid ’70s the RAF was looking out for a replacement. This ultimately took the form of the Hawk, which although not quite as slippery as the Gnat was a much superior trainer, the instructor having a superb view, the aircraft having a significantly greater range and much more reliable systems. By 1980 the Hawk had replaced the Gnat both as a trainer and as the mount of the Red Arrows and is still in service today. A number of Gnat  airframes were allocated to the ground training schools at Halton and Cosford where they were maintained in a serviceable condition, whilst remaining groundborne.

 

However, this wasn’t the end of Gnat flying. When no longer needed for ground training work the Gnats were sold and proved capable of being returned to airworthy status. Today the Heritage Aircraft Trust, based at North Weald, operates three Gnat T1s on the display circuit. The pilots are a mixture of ex military, military and purely civil and only need  a PPL. The Gnats are all on the civil register but wear RAF colours, one being painted in Red Arrows livery, one in the 4 FTS colour scheme and one in the livery of the Yellowjacks team which preceded the formation of the Red Arrows. The Trust discovered in scrap yards a couple of ex Royal Navy Palouste air starters, originally capable of being carried as an external store. These, mounted on a road trailer, solve the starting problem at away venues. The team display as a three aircraft formation at Air Displays both at home and overseas.  Thanks to Freeman Samantha Waller members of The Honourable Company of Air Pilots were invited to North Weald on 27 April to witness the team’s final practice session before the 2014 air display season. It was a great pleasure to see and hear the diminutive Gnats flying again, especially as two of the pilots were students of the author’s at Cambridge University Air Squadron in the late ’90s. The Heritage Aircraft Trust’s aim is ‘ To preserve and protect Gnat and other historic aircraft for the benefit of the public and to demonstrate and display such aircraft at public events and to conserve them as heritage assets.’  Further details of the Heritage Aviation Trust can be found on their website, www.gnatdisplayteam.com.

Tom Eeles and his students

%d bloggers like this: