Early VTOL history
The Balzac V
The end of the programme
During the 1960s there was a great drive to develop VTOL (Vertical Take-Off and Landing) aircraft. Many aircraft were designed, but most of these projects ended in failure. Only two aircraft - the BAE Systems Harrier and Yakovlev Yak-38 - were put into production. One of France's greatest attempts was the Mirage III V, which was successful in many ways. Its most impressive achievement was high speed – today it still holds the record for the fastest VTOL aircraft, having achieved a top speed of Mach 2. However, after numerous crashes and the deaths of test pilots, the project was finally abandoned and France never received a VTOL fighter.
Early VTOL history
The Balzac V
The end of the programme
Early VTOL history
When the Cold War was at its peak from the late 1950s to the early 1970s, military technology was being developed at a fast and ever-increasing pace. New weapons kept the two superpowers locked in a spiralling arms race, with each one developing something new to outdo the other. The ICBM (Intercontinental Ballistic Missile) was one of these new weapons that had a great impact on the design and operation of Cold War weapons. It caused many aircraft, especially bombers and fighter-bombers, to be cancelled as ICBMs were seen as quicker, cheaper, less vulnerable and more effective than manned aircraft.
Since the 1950s aircraft had become bigger, heavier, faster and had come to depend on large, fixed runways that were difficult to conceal. Governments, and especially NATO, were worried that ICBMs, both nuclear and conventional, could easily wipe out these conspicuously visible bases. The solution was thought to be dispersed basing, which would require VTOL, or at least STOVL (Short Take-Off and Vertical Landing) aircraft.
NATO was so keen to develop V/STOL aircraft that in 1960 they drew up 'NATO Basic Military Requirement 3', which was designed to produce a V/STOL aircraft that would enter service in 1964. But in March 1961 the requirement was changed to a VTOL aircraft that could do Mach 2.2 at high altitude, Mach 1 at low altitude and deliver nuclear weapons over a 460 km (285 mile) radius. The British Hawker P.1154 and Mirage III V (pronounced ‘three-V’, the V for VTOL) took part.
The
Hawker P.1154 was to be powered by a four-exhaust-nozzle vectored thrust Bristol-Siddeley
BS 100 engine developing 15 000 kg (33 000 lb) of thrust with afterburning
(the afterburning taking place at the front two exhaust nozzles of the engine).
In April 1962 the P.1154 ‘won’ the contest, but the French refused
to accept the British aircraft. Because of this, and doubts over the feasibility
of workable VTOL aircraft, NATO decided not to choose between either aircraft
and the project subsequently lapsed, leaving nations to develop their own
VTOL aircraft.
Even before the NATO competition, a number of governments began designing V/STOL aircraft. The British began work on the Hawker P.1127, which first flew in October 1960 and soon led to the BAe (British Aerospace – now BAE Systems) Harrier. The Americans tested a number of VTOL aircraft, including designs like the Lockheed XV-4 Hummingbird and Ryan XV-6 Vertifan. Some success was achieved with designs like the X-13 Vertijet and the Convair XFY-1 'Pogo', which took off with their noses pointed into the air. However, landing difficulties ensured they never went into production.
The
Dutch and West Germans collaborated to produce the VFW-Fokker Vak 191B, which
was powered by two lift jets and a vectored/propulsive turbofan for vertical
and horizontal flight, in many ways similar to the Harrier. The first prototype
made its maiden flight in 1971, but was cancelled in the mid-1970s. The Soviets
achieved some success with their Yak-38 'Forger', which was powered by two
lift jets behind its cockpit and one vectored thrust turbojet used for vertical
and horizontal flight. Although less capable than the Harrier, it was only
the second VTOL aircraft to enter service, which it did in 1976.
Early
French VTOL history
The
French had made good progress with vectored thrust engines and, ironically,
it is to the French engineer Michel Wibault that the Harrier owes its engine.
Wibault filed the patent for a jet engine whose exhaust was directed through
two jet pipes which could be swivelled horizontally or vertically. As the
French government was not interested, Wibault sold the idea to the British
company Bristol, who bought the license for it. They modified Wibault’s
engine and produced the Pegasus turbojet which used four swivelling jets.
(Rolls Royce now produces the Pegasus engine.)
France’s
biggest aviation company Dassault noted British progress with the Pegasus
and began design work a swept-wing aircraft that would be built around the
Pegasus engine or an equivalent. This aircraft was called the Cavalier and
the first version, the MD 610, was planned to have a Bristol BE 53/8 engine
developing 8 600 kg (19 000 lb) of thrust with two vectored thrust exhaust
nozzles on each side of the fuselage. The aircraft was similar to the Harrier
in layout and had twin air intakes mounted on each side of the fuselage, a
gently swept shoulder-mounted wing and a single vertical tailfin with the
tailplane mid-mounted on it. Landing gear was a bicycle-type with twin outriggers.
The aircraft would have a VTOL operating weight of around 7 480 kg (16 500
lb).
Dassault
briefly studied another two Cavalier variants. The MD 620 was planned to have
a Rolls Royce RB 165 engine developing 4 080 kg (9 000 lb) of thrust and four
Rolls Royce RB 153 lift engines producing 1 590 kg (3 500 lb) of thrust each.
Other changes were mid-mounted wings and conventional tricycle-type landing
gear. The MD 630 Cavalier was the third variant and was planned with two RB
165 engines and two RB 162 lift engines developing 2 270 kg (5 000 lb) of
thrust each. For VTOL operation it would weigh around 5 580 kg (12 300 lb).
The
vectored thrust engine Cavalier was presented to the French Air Force general
staff. However, it was not approved since it didn’t allow supersonic
flight – the swivelling exhaust nozzles would not permit it. In addition,
it was considered less safe than a multi-engined aircraft.
After their initial lack of interest, the French government warmed to the idea of a VTOL aircraft. On 16 September 1959 the DTIA (Direction Technique et Industrielle de l' Aeronautique) issued a requirement to the French aviation industry for a VTOL attack and reconnaissance aircraft that would be able to use any front-line airstrip and would be able to carry nuclear weapons. The French government later specified that the aircraft had to have a top speed of Mach 2 and would have to carry nuclear and conventional weapons as well as two internal 30-mm cannons.
Dassault proposed its Mach 2 capable Mirage III V and in September 1960 it was accepted. Around 120 aircraft were required to replace L'Armee de L'Air (French Air Force) Mirage IIIE attack aircraft by 1967.
The
Balzac V
The
aircraft had nine engines: one conventional horizontally-mounted Bristol-Siddeley
Orpheus 3 turbojet producing 2 268 kg (5 000 lb) of thrust for horizontal
flight and eight Rolls-Royce RB 108 turbojets for vertical lift. There were
four compartments in the aircraft, each containing two vertically mounted
engines: one compartment on the outside of each air intake of the Orpheus
engine and one compartment on each side of the Orpheus exhaust pipe. Four
intakes situated on the top of these compartments provided the lift jets with
air, while their exhausts were situated in apertures underneath the fuselage.
The exhausts were fitted with blanking caps that were closed during horizontal
flight to minimise drag. If one lift jet failed, its diagonal opposite would
be reduced to idle in order to maintain stability.
Each
RB 108 engine weighted 122 kg (269 lb) and generated a total of 1 002 kg (2
210 lb) of thrust, of which 82 kg (180 lb), 11 % of the total thrust, was
bled off for the jet reaction control system. This system was comprised of
a series of pipes that used lift jet bleed air to provide thrust and keep
the Balzac V stable in flight. One pair of pipes exhausted just under the
nose, one pair exhausted under the middle of each wing leading edge and another
pair exhausted below the tail.
A
control valve, which the pilot could alter by using a joystick, distributed
the exhaust gases for the reaction control stabilisation system. To control
the physical stabilization jets, a triple channel electronic flight control
system was used. It was chosen over conventional linkage controls in order
to provide greater precision. This system was the beginning of modern fly-by-wire
flight controls in that there was redundancy (through the three channels)
and no linkage.
Total internal fuel capacity of the Balzac V was just 1650 litres, which gave an endurance of just 12 minutes with all engines running. The Balzac V was unarmed and carried no operational equipment. Even so, it didn’t have a high enough thrust-to-weight ratio to fly past Mach 1 – its maximum speed was only Mach .90. In addition, the area-ruled ‘wasp-waist’ of the Mirage III that decreased drag and increased speed was not included on the Balzac. This helped make it a much slower aircraft than it could have been.
These
successes were overshadowed by two fatal accidents that were partly as a result
of the complexity of the flight control system, jet reaction control system
and nine-engine layout. The first accident occurred on 10 January 1964 on
the Balzac V’s 125th sortie. Jean Pinier, of France's Flight Test Centre,
lost control of the aircraft after he directed it into a crosswind to eliminate
drift. The speed and angle of attack were beyond the safe limits of controlled
flight and so the aircraft crashed, killing Pinier. After the crash the aircraft
was rebuilt and first flew again in February 1965.
The United States Air Force also tested the Balzac and lost one of their pilots as a result – ironically with the rebuilt aircraft that killed Pinier. On 8 September 1965 USAF pilot Major Neal was killed when the vertical lift jets ran out of fuel and his ejection seat malfunctioned.
International
agreements
In
the early 1960s, Boeing was looking to enter the light combat aircraft market
and saw co-operation with Dassault as the key. On 23 December 1961, the two
corporations signed technical co-operation and licensing agreements, mainly
to do with vertical takeoff stabilisation devices and Dassault-designed flight
controls. One of their first joint project goals was an aircraft that would
be entered in the NATO Basic Military Requirement 3 competition. Since Boeing
was involved in the project, giving technical assistance to Dassault, they
were obliged to offer it to the US government as well as NATO and the French
government. Early in 1963 the US Air Force considered buying three two-seat
Mirage III Vs with the intention to test them and in May 1964 was prepared
to buy. Boeing was to reassemble the aircraft in the US and test them there,
but in the end the deal fell through and no aircraft were bought.
In 1963 Dassault tried to collaborate with the Federal Republic of Germany (West Germany) on the single- and two-seater combat prototype Mirage III Vs. Three prototypes were planned in 1963, but were reduced to two in May 1964, to be designated Mirage III V 03 and 04. After no one showed any serious interest in a two-seater, the idea was dropped.
The
new lift jets, internal weapons bay, and extra fuel made the Mirage III V
much larger and heavier than the Balzac V. The Mirage III V also differed
from the Balzac V in that it had a taller vertical tail fin and the wing was
larger, thinner and had a cranked leading edge. Unlike previous Mirage designs,
twin landing gear wheels were used on all three legs. Armament was to consist
of two 30 mm DEFA cannon with 125 rounds each and a mere 544 kg (1 200 lb)
of ordnance in an internal weapons bay. Even for the mid-1960s, this was an
unacceptably small weapon load for any fighter. Unfortunately it was the eight
vertical lift jets that weighed the Mirage III V down and greatly limited
weapons (and fuel) carriage.
The first Mirage III V prototype, the Mirage III V 01, was fitted with a TF 104B engine (modified Pratt and Whitney [P&W] turbofan) developing around 6 400 kg (14 100 lb) of thrust in afterburner, and eight Rolls Royce RB 162-1 lifting jets. The new lifting jets had fibreglass casings and incorporated reinforced plastics to reduce weight and cost. Each engine weighed 125 kg (275 lb), was 1.315 metres (4 ft 4 in) long and had a diameter of 66 cm (2 ft 2 in). Its normal thrust rating was 2 000 kg (4 409 lb), but it could produce 2 140 kg (4 718 lb) in an emergency.
The modified P&W engine was still at its development stage and size and weight had not been finalised. It was decided to first test the American engine, and so a Mirage III was converted into a flying test-bed called the Mirage III T and equipped with the TF 104 developing 6 300 kg (13 900 lb) of thrust. It made its first flight at Istres on 25 January 1965, piloted by Jean Coureau, with the more powerful TF 106 engine (also a modified P&W). Many problems were encountered with both engines, the worst of which was stalling on takeoff! The Americans experienced similar problems when they installed the engines in their own aircraft.
Free-hovering
trials with the Mirage III V 01 began on 12 February 1965 at Melun-Villaroche
with René Bigand at the controls. There were many problems that emerged during
testing. The TF 104 was troublesome, the lift engines didn’t give the
expected thrust and the airframe was too heavy. The more powerful TF 106 engine
developing about 8 tons (17 000 lb) of thrust was installed in the Mirage
III V 01 in December 1965 for the aircraft’s 15th sortie.
By
this time the French authorities were beginning to doubt the viability of
VTOL aircraft, especially with all the problems encountered with the Balzac
V and Mirage III V. The excessive weight of the lift engines significantly
limited performance and weapons load, greatly restricting the aircraft’s
fighting abilities. And ground support for a dispersed VTOL aircraft would
prove very difficult – all the fuel, spares and weapons would have to
be transported to the aircraft, which could be almost anywhere – in
a forest, on an island, in a swamp, or high up on a mountain. The aircraft
would be an easy target if it had to re-supply from fixed bases.
In
addition, there were problems with operating on unprepared ground. Debris
from roughly prepared landing ground was often sucked back into the Mirage
III V’s engines, causing them to stall. A semi-prepared landing zone
would be needed to ensure the engines didn’t stall, but even this was
no guarantee, since the engines also stalled when their own exhaust gases
were sucked back into their intakes. Meanwhile other aircraft were improving
their short-field performance, especially swing-wing aircraft like the American
General Dynamics F-111 and Soviet Mikoyan-Gurevich MiG-23. These aircraft
had been designed to STOL requirements and were much more successful than
VTOL aircraft in that they could use short, roughly prepared and dispersed
airstrips with minimal effort and be able to carry a heavy weapon load over
long ranges.
By
the end of 1965, even though VTOL was beginning to look increasingly impracticable,
the French Air Force staff had not totally given up on Dassault’s project.
Instead, they drew up requirements for the Mirage III V ‘1970’,
as they saw a need for a nuclear-armed aircraft to replace the Air Force’s
F-100s and Mirage IIIEs by 1970.
In
the meantime, the Mirage III V 01 reached a significant milestone: it made
its first full transitioning flight on 24 March 1966, piloted by Jean-Marie
Saget. But even this achievement was overshadowed by lateral instability during
the transition phase of the flight. On 28 March 1966 the Defence Ministry
halted the Mirage III V production programme for technical and financial reasons.
Only limited testing was allowed to continue in order to gain more experimental
data on VTOL aircraft. The Mirage III V 01 eventually went supersonic when
it was flown to Mach 1.35 without its lift engines.
Mirage III V 02
Piloted by Jean-Marie Saget, the second prototype made its first flight on 22 June 1966. On 12 September that year, on its 11th sortie, it reached Mach 2.03 in level flight, breaking the world speed record for a VTOL aircraft. Today it is still the only such aircraft to have exceeded Mach 2 - the closest any other VTOL aircraft came was the prototype Yak-141, which reached Mach 1.69.
The end of the programme
Instead of the Mirage III V, the French Defence Ministry pursued other aircraft that could take off and land in short distances from roughly prepared strips. First were the Mirage F1 and F2/F3. These all had the same general configuration of a high-mounted swept wing with high-lift devices and horizontal tail surfaces. They had much better slow-speed performance than Dassault’s other delta-winged designs, as well as greater internal fuel capacity.
At
the same time Dassault developed a series of swing-wing aircraft, the first
of which was the single-engine Mirage G. First flown on 18 November 1967,
it showed great promise, but the French Air Force dropped the project after
they opted for a twin-engine variant. Thus the Mirage G4/G8 was developed.
The Mirage G4 was the initial two-seat variant, but was abandoned in favour
of the single-seat Mirage G8. First flown on 8 May 1971, it was cancelled
because of high costs and changing mission requirements. In the end, the Mirage
F1 was put into production and went on to sell around the world. Together
with the Anglo-French SEPECAT Jaguar, the F1 filled the Mirage III V’s
intended role, with the Jaguar being used for attack and the F1 being used
mainly for interception.
The
Mirage III V programme was abandoned because the aircraft was extremely complex,
resulting in many crashes, and could not carry a large enough payload because
of the heavy lifting jets. Fuel consumption was extremely high, especially
during hovering flight and consequently range was very poor. The Harrier,
which uses a vectored thrust engine, is so successful because it uses the
same engine for vertical and horizontal flight and doesn’t have to carry
heavy lift jets that remain unused for most of the flight.
The
Mirage III V programme failed in the end and cost a lot of money - in 1972
the French Court of Auditors estimated the cost at 270 million francs. However,
the Mirage III V programme did have some use in the end. Much of the research
data gained in the Balzac V’s 179 flights, the Mirage III V 01’s
40 flights and the Mirage III V 02’s 24 flights was used in other Dassault
programmes and increased the knowledge of VTOL aircraft flight characteristics.
Advances
made with the Mirage III V’s triple channel analogue flight control
system were later applied to the variable geometry, or ‘swing-wing’,
version of the Falcon 20 business jet, the Mirage 2000 and the Rafale.
The Balzac V was the first aircraft to transmit flight data to the ground
by telemetering and pioneered the process. Together with tape recording, telemetering
greatly increased the amount and quality of data gathered. Although France’s
VTOL aircraft programme was cancelled in the end, it was not considered to
have been a complete failure. Through various spin-offs, many aircraft flying
today owe something to the Balzac V and Mirage III V. Although the two aircraft
never entered service, they opened up the then unexplored field of VTOL flight
– they were the early pioneers.
