Short SC.1 – Barely VTOL
The notion of aircraft capable of vertical take-off and landing (VTOL) is as old as the idea of aviation itself and the Short SC.1 was the first major attempt.
When Leonardo Da Vinci sketched his ideas for a flying machine in the 15th century, he envisaged a VTOL aircraft. When eccentric genius Nikola Tesla applied for a patent for an aircraft design in 1928, it was for a machine capable of VTOL; he called it the “helicopter-airplane.”
During World War Two, the obvious military applications of VTOL renewed interest in this concept. German aviation designers produced proposals for two very different single-seat VTOL fighters.
The Focke-Achgelis Fa 269 was a tilt-rotor design while the Focke-Wulf Triebflügeljäger was a ramjet-powered tail-sitter. Neither progressed further than the production of mock-ups, but the benefits of a VTOL military aircraft were very evident.
Such an aircraft could provide point defence in areas far from conventional airbases and did not require a runway that was vulnerable to enemy bombing.
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In the years immediately following World War Two, jets became commonplace, take-off and landing speeds rose and runways got even longer and even more vulnerable to attack. In America, two VTOL designs progressed to the stage of flying prototypes.
Both the piston-engine Convair XFY-1 Pogo and the jet Ryan X-13 Vertijet were essentially single-seat aircraft that was designed to take off and land while sitting vertically on their tail. Both proved capable of taking off vertically and transitioning to horizontal flight.
However, both were so difficult to land vertically that achieving this safely would have been beyond the ability of most pilots.
What was needed was an aircraft that could take off and land vertically while in a conventional horizontal attitude. The first aircraft to achieve this, and arguably the first safe and practical VTOL aircraft, was designed and built not in America but Northern Ireland…
Short Brothers were established in 1897 by brothers Eustace and Oswald Short. Initially, the company produced balloons at a factory in Sussex, but in 1908, Short Brothers became the first manufacturer of production aircraft in the world.
By the time the Second World War began in 1939, Shorts was one of Britain’s most important aircraft manufacturers, working from a factory in Rochester in Kent and responsible for the design and production (amongst other aircraft) of the Short Sunderland flying boat and the Short Stirling heavy bomber.
To avoid German bombing, Shorts built a new HQ in Belfast in Northern Ireland in 1941 and 1948, moved all design and manufacturing facilities to Belfast.
Just like their American counterparts, the British Air Ministry became interested in the possibility of VTOL military aircraft after the end of World War Two.
In 1953, the Ministry of Supply issued Specification ER.143 which called for the design and manufacture of a research aircraft capable of taking off vertically while in a horizontal attitude and then accelerating forward into normal flight.
Several proposals were considered, but only Short Brothers were awarded a contract in October 1954 to produce two flying prototypes.
Design and Development
Shorts were aware of the American Convair XFY-1 Pogo (flight testing of that aircraft began in April 1954). They were also almost certainly also aware of the problems involved in safely landing a VTOL tail-sitter, and their design was very different.
The new aircraft, which was given the designation Short SC.1, would use no less than five of a new, lightweight turbojet engine developed by Rolls-Royce.
The RB-108 was designed by Rolls-Royce in the early 1950s specifically for use in VTOL aircraft. The concept was that several RB-108 engines would be used to lift an aircraft into a hover before a more powerful conventional thrust engine propelled it forward into normal flight.
The SC.1 would use four of these engines, mounted vertically in pairs near the aircraft’s centre of gravity, to provide over 8,000lbs of vertical thrust.
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Both pairs of engines were to be mounted on gimbals, allowing them to be swivelled fore or aft to assist in acceleration and deceleration. A single additional RB.108, mounted horizontally near the tail, would provide forward thrust.
The aircraft itself was to be a stubby, rather ungainly low-wing, tail-less delta design with a single-seat cockpit in the nose. Flying controls were conventional, but with the addition of a single throttle control for the four lift engines.
The aircraft used conventional control surfaces during forward flight but bleed air from the lift engines was routed to puffer-jets in the wingtips, nose and tail to provide pitch and roll control in the hover or slow flight.
The method by which control was achieved was unusual and innovative on the SC.1. This aircraft used an early “fly-by-wire” system.
On most of the aircraft of World War Two and before, control surfaces were directly linked to flying controls by heavy steel cables. On SC.1, the flying controls were electrically connected to three servo-motors which then operated the control surfaces.
That presented challenges for pilots; fly-by-wire systems lack the feedback that comes from being able to actually feel what control surfaces are doing.
However, on the SC.1, this approach was considered essential because it allowed the incorporation of an auto-stabiliser which monitored feedback from control surfaces and made adjustments as required to maintain a stable attitude.
Three modes were incorporated in the system: Full, where all controls were monitored and adjusted by the system, Partial where the ailerons, elevator and rudder were directly controlled through the flying controls and only the puffer-jets were auto-stabilised and Direct, where all controls were controlled from the cockpit with no auto-stabilisation.
The fly-by-wire system was complex and innovative, but it was felt to be essential because it was believed that achieving stable flight at slow speed and in the hover would only be possible with the assistance of the auto-stabiliser.
SC.1 Flight Testing
The first prototype, XG900, was completed at the Shorts factory in Northern Ireland in late 1956 and underwent engine-run trials there in early 1957. XG900 was then transported by sea to the Royal Aircraft Establishment (RAE) experimental aircraft unit at Boscombe Down in Wiltshire.
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Flight testing began in April 1957, but initial flights only tested the aircraft’s ability to take off and land conventionally.
The second prototype, XG905, was completed in early 1958. A gantry was constructed at Boscombe Down to allow testing of vertical take-off and landing while the aircraft was safely tethered.
XG905 was placed on a platform six feet above the ground and was able to rise only 15 feet above this as well as being constrained to move no more than 10 feet horizontally from its starting position.
With the aircraft in this gantry, initial training was undertaken from May 1958 with eight pilots who were allowed to become familiar with the aircraft’s handling in the hover and while rising and descending.
In October 1958 the SC.1 performed its first free vertical take-off and landing without the gantry at Boscombe Down. In April 1958, it successfully made the transition from vertical to conventional horizontal flight.
As flight testing continued, several things became apparent. First, the pilot workload was very high during the transition from vertical to horizontal flight and vice-versa. Due to high fuel consumption, the four lift engines had to be shut down when the aircraft was in conventional horizontal flight.
When preparing to land vertically, these engines had to be re-started, a complex and time-consuming procedure.
The second issue was speed, or rather the lack of it. With only a single RB.108 providing forward thrust, the top speed was less than 250 knots. The third issue was associated with the final phase of approaching the ground in the hover.
As it neared the ground, the aircraft would enter turbulence created by its own jet-wash which made it difficult to maintain attitude. The engines also began to ingest their own expelled, hot exhaust gases at this point, meaning that they produced less lift.
This created something called “suck-down” where the rate of descent could suddenly increase to a dangerous level as the aircraft descended vertically towards the ground.
However, given that it had always been intended purely as a research aircraft, identifying these issues and devising ways to deal with them was an important part of the SC.1 programme. As test pilots found ways to deal with these issues, the SC.1 provided the data needed for the VTOL programme.
The SC.1 was demonstrated in public for the first time at the Farnborough air show in 1960 and the following year at the Paris air show.
Flight testing was marred by a tragic accident in October 1963. Shorts test pilot J.R. Green was flying XG905 when the auto-stabiliser system started to behave erratically.
He reverted to direct control, but a fault in the system led to the auto-stabiliser causing the aircraft to roll into the ground. Green died in the accident and XG905 was badly damaged, though it was repaired and returned to flying condition.
It was also provided for the first time with a heads-up display (HUD) and subsequently used for night flying and bad weather flight testing.
Both SC.1 prototypes continued to be used for flight testing into the early 1970s and both did precisely what they were supposed to do; discover the inherent problems involved with VTOL flight.
The data obtained from these two aircraft proved invaluable when the British Air Ministry decided to continue working towards the development of a military VTOL aircraft. However, it wasn’t Shorts who were given this work but Hawker when, in 1959, the Ministry of Supply placed an order for two prototypes of the P.1127.
The Hawker P.1127 would further refine the SC.1 design. In particular, Hawker’s Chief Designer, Sydney Camm (the man behind the Hawker Hurricane and Hunter) insisted that the new aircraft must be less complex than the SC.1. Instead of five engines, the P.1127 would use a single Rolls-Royce engine for both vertical and horizontal flight.
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This in turn would lead to the creation of the Hawker Siddeley Kestrel FGA.1 and finally to the Hawker Siddeley Harrier which would enter service with the RAF in 1969. The Harrier would prove to be practical, reliable and above all, relatively easy to fly.
It remained in service with the RAF and other users including the US Marine Corps for over 35 years. The creation of the Harrier would not have been possible without the lessons learned from the bold and successful SC.1 project.
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- Crew: 1
- Length: 25 ft 6 in (7.77 m)
- Wingspan: 23 ft 6 in (7.16 m)
- Height: 10 ft 8 in (3.25 m)
- Empty weight: 6,260 lb (2,839 kg)
- Max takeoff weight: 8,050 lb (3,651 kg)
- Powerplant: 1 × Rolls-Royce RB.108 turbojets, 2,130 lbf (9.5 kN) thrust (forward flight)
- Powerplant: 4 × Rolls-Royce RB.108 turbojets, 2,130 lbf (9.5 kN) thrust each (lift engines)
- Maximum speed: 246 mph (396 km/h, 214 kn)
- Range: 150 mi (240 km, 130 nmi)
- Service ceiling: 8,000 ft (2,400 m)
- Rate of climb: 700 ft/min (3.6 m/s)