Miloch
May 17th 20, 06:47 AM
https://en.wikipedia.org/wiki/Northrop_YA-9
The Northrop YA-9 was a prototype attack aircraft developed for the United
States Air Force A-X program. The YA-9 was
passed over in preference for the Fairchild Republic YA-10 that entered
production as the A-10 Thunderbolt II.
Background
Criticism that the U.S. Air Force did not take close air support seriously
prompted a few service members to seek a specialized attack aircraft. In the
Vietnam War, large numbers of ground-attack aircraft were shot down by small
arms, surface-to-air missiles, and low-level anti-aircraft gunfire, prompting
the development of an aircraft better able to survive such weapons. Fast jets
such as the North American F-100 Super Sabre, Republic F-105 Thunderchief, and
McDonnell Douglas F-4 Phantom II proved for the most part to be ineffective for
close air support. The Douglas A-1 Skyraider was the USAF's primary close air
support aircraft.
In mid-1966, the U.S. Air Force formed the Attack Experimental (A-X) program
office. On 6 March 1967, the Air Force released a request for information to 21
defense contractors for the A-X. The objective was to create a design study for
a low-cost attack aircraft. Discussions with A-1 Skyraider pilots operating in
Vietnam and analysis of the effectiveness of current aircraft used in the role
indicated the ideal aircraft should have long loiter time, low-speed
maneuverability, massive cannon firepower, and extreme survivability; an
aircraft that had the best elements of the Ilyushin Il-2, Henschel Hs 129 and
Skyraider. While turboprop engines were requested in the initial request, by May
1969, requirements had changed to specify use of turbofan engines.
In May 1970, the USAF issued a modified, and much more detailed request for
proposals (RFP). The threat of Soviet armored forces and all-weather attack
operations had become more serious. Now included in the requirements was that
the aircraft would be designed specifically for the 30 mm cannon. The RFP also
called for an aircraft with a maximum speed of 460 mph (740 km/h), takeoff
distance of 4,000 feet (1,200 m), external load of 16,000 pounds (7,300 kg),
285-mile (460 km) mission radius, and a unit cost of US$1.4 million. Simplicity
and low cost were also vital requirements, with a maximum flyaway cost of $1.4
million based on a 600 aircraft production run. Performance was to be sacrificed
where necessary to keep development and production costs under control. During
this time, a separate RFP was released for A-X's 30 mm cannon with requirements
for a high rate of fire (4,000 round/minute) and a high muzzle velocity. Six
companies submitted proposals to the USAF, with Northrop and Fairchild Republic
selected on December 18, 1970 to build prototypes: the YA-9A and YA-10A,
respectively. Meanwhile, General Electric and Philco-Ford were selected to build
and test GAU-8 cannon prototypes.
Design
The A-9 was a shoulder-wing monoplane of all-riveted aluminum alloy
construction, with honeycomb structures and chemically milled skins. The
required twin turbofans were fitted in nacelles under the aircraft's wing roots.
Northrop selected the 7,200 pounds-force (32 kN) Lycoming YF102 engine for the
YA-9 rather than the more powerful (9,280 pounds-force (41.3 kN))
General Electric TF34 used by the A-10, although either engine could be
accommodated. The F-102 engine was a new design, based on the T55 turboshaft
that powered the CH-47 helicopter, which was selected in order to minimize
costs. The aircraft had a large cruciform stabilizer in order to improve
directional stability for low-level flight. Split ailerons were fitted that
could be used as airbrakes. When these airbrakes were operated asymmetrically in
conjunction with the aircraft's rudder, sideways control forces could be applied
(and the aircraft moved sideways) without yawing or banking, easing weapon
aiming.
The pilot sat under a large bubble canopy well ahead of the leading edge of the
wings. The cockpit was surrounded by a bathtub of armor (aluminum in the
prototypes, which would have been replaced by titanium if production occurred)
while the wing-mounted fuel tanks were self-sealing and filled with foam to
minimize the potential for fires or massive fuel loss. Dual redundant hydraulic
flight control systems were fitted, with a further manual backup to prevent a
single hit from causing control failure. These design features were hoped to
reduce combat losses by as much as 90% in Vietnam-type operations. A single 30
mm Gatling gun was to be fitted in the belly of the aircraft, with the gun
barrels extending under the nose. As the gun was mounted on the aircraft's
centerline, the undercarriage nosewheel was offset one foot (0.30 m) to the
left. As the GAU-8 Avenger cannon was not ready, both the YA-9 prototypes (as
well as the two YA-10s) were instead fitted with the smaller 20 mm M61 Vulcan.
Ten underwing hardpoints were fitted, allowing up to 16,000 pounds (7,300 kg) of
weapons, including bombs and AGM-65 Maverick air-to-ground missiles, to be
carried.
Role
Attack aircraft
Manufacturer
Northrop
First flight
30 May 1972
Status
Canceled
Primary user
United States Air Force
NASA
Number built
2
Fly-off
The YA-9 took its first flight on 30 May 1972, with the second prototype flying
on 23 August. Northrop's flight testing was successful, with the aircraft
claimed to have "fighter-like" handling and to be a good weapon platform. A
fly-off by USAF test pilots of the two competing designs took place between 10
October and 9 December 1972. While the YA-9 fully met the USAF's requirements,
the YA-10 was declared the winner on 18 January 1973. The use of the
established TF34 engine rather than the untried F102 by the YA-10 may have been
preferred by the Air Force, while Fairchild had no alternative work available
and was unlikely to survive if it did not win the A-X contract.
The two YA-9 prototypes were subsequently relegated to NASA for continued flight
testing before being retired. When retired, the YA-9s' custom-built engines were
removed and were later mated to a C-8 Buffalo airframe as part of the
NASA-Boeing joint Quiet Short-haul Research Aircraft (QSRA) study into a quiet
short-haul commercial aircraft.
Specifications (YA-9A)
General characteristics
Crew: 1
Length: 53 ft 6 in (16.31 m)
Wingspan: 58 ft 0 in (17.68 m)
Height: 16 ft 11 in (5.16 m)
Wing area: 580 sq ft (54 m2)
Gross weight: 25,000 lb (11,340 kg)
Max takeoff weight: 41,000 lb (18,597 kg)
Powerplant: 2 × Lycoming YF102-LD-100 turbofan engines, 7,200 lbf (32 kN) thrust
each
Performance
Rate of climb: 5,000 ft/min (25 m/s)
Armament
1x 20 mm M61 Vulcan Gatling gun (Substitute for GAU-8/A)
Up to 16,000 lb (7,260 kg) of ordnance
*
The Northrop YA-9 was a prototype attack aircraft developed for the United
States Air Force A-X program. The YA-9 was
passed over in preference for the Fairchild Republic YA-10 that entered
production as the A-10 Thunderbolt II.
Background
Criticism that the U.S. Air Force did not take close air support seriously
prompted a few service members to seek a specialized attack aircraft. In the
Vietnam War, large numbers of ground-attack aircraft were shot down by small
arms, surface-to-air missiles, and low-level anti-aircraft gunfire, prompting
the development of an aircraft better able to survive such weapons. Fast jets
such as the North American F-100 Super Sabre, Republic F-105 Thunderchief, and
McDonnell Douglas F-4 Phantom II proved for the most part to be ineffective for
close air support. The Douglas A-1 Skyraider was the USAF's primary close air
support aircraft.
In mid-1966, the U.S. Air Force formed the Attack Experimental (A-X) program
office. On 6 March 1967, the Air Force released a request for information to 21
defense contractors for the A-X. The objective was to create a design study for
a low-cost attack aircraft. Discussions with A-1 Skyraider pilots operating in
Vietnam and analysis of the effectiveness of current aircraft used in the role
indicated the ideal aircraft should have long loiter time, low-speed
maneuverability, massive cannon firepower, and extreme survivability; an
aircraft that had the best elements of the Ilyushin Il-2, Henschel Hs 129 and
Skyraider. While turboprop engines were requested in the initial request, by May
1969, requirements had changed to specify use of turbofan engines.
In May 1970, the USAF issued a modified, and much more detailed request for
proposals (RFP). The threat of Soviet armored forces and all-weather attack
operations had become more serious. Now included in the requirements was that
the aircraft would be designed specifically for the 30 mm cannon. The RFP also
called for an aircraft with a maximum speed of 460 mph (740 km/h), takeoff
distance of 4,000 feet (1,200 m), external load of 16,000 pounds (7,300 kg),
285-mile (460 km) mission radius, and a unit cost of US$1.4 million. Simplicity
and low cost were also vital requirements, with a maximum flyaway cost of $1.4
million based on a 600 aircraft production run. Performance was to be sacrificed
where necessary to keep development and production costs under control. During
this time, a separate RFP was released for A-X's 30 mm cannon with requirements
for a high rate of fire (4,000 round/minute) and a high muzzle velocity. Six
companies submitted proposals to the USAF, with Northrop and Fairchild Republic
selected on December 18, 1970 to build prototypes: the YA-9A and YA-10A,
respectively. Meanwhile, General Electric and Philco-Ford were selected to build
and test GAU-8 cannon prototypes.
Design
The A-9 was a shoulder-wing monoplane of all-riveted aluminum alloy
construction, with honeycomb structures and chemically milled skins. The
required twin turbofans were fitted in nacelles under the aircraft's wing roots.
Northrop selected the 7,200 pounds-force (32 kN) Lycoming YF102 engine for the
YA-9 rather than the more powerful (9,280 pounds-force (41.3 kN))
General Electric TF34 used by the A-10, although either engine could be
accommodated. The F-102 engine was a new design, based on the T55 turboshaft
that powered the CH-47 helicopter, which was selected in order to minimize
costs. The aircraft had a large cruciform stabilizer in order to improve
directional stability for low-level flight. Split ailerons were fitted that
could be used as airbrakes. When these airbrakes were operated asymmetrically in
conjunction with the aircraft's rudder, sideways control forces could be applied
(and the aircraft moved sideways) without yawing or banking, easing weapon
aiming.
The pilot sat under a large bubble canopy well ahead of the leading edge of the
wings. The cockpit was surrounded by a bathtub of armor (aluminum in the
prototypes, which would have been replaced by titanium if production occurred)
while the wing-mounted fuel tanks were self-sealing and filled with foam to
minimize the potential for fires or massive fuel loss. Dual redundant hydraulic
flight control systems were fitted, with a further manual backup to prevent a
single hit from causing control failure. These design features were hoped to
reduce combat losses by as much as 90% in Vietnam-type operations. A single 30
mm Gatling gun was to be fitted in the belly of the aircraft, with the gun
barrels extending under the nose. As the gun was mounted on the aircraft's
centerline, the undercarriage nosewheel was offset one foot (0.30 m) to the
left. As the GAU-8 Avenger cannon was not ready, both the YA-9 prototypes (as
well as the two YA-10s) were instead fitted with the smaller 20 mm M61 Vulcan.
Ten underwing hardpoints were fitted, allowing up to 16,000 pounds (7,300 kg) of
weapons, including bombs and AGM-65 Maverick air-to-ground missiles, to be
carried.
Role
Attack aircraft
Manufacturer
Northrop
First flight
30 May 1972
Status
Canceled
Primary user
United States Air Force
NASA
Number built
2
Fly-off
The YA-9 took its first flight on 30 May 1972, with the second prototype flying
on 23 August. Northrop's flight testing was successful, with the aircraft
claimed to have "fighter-like" handling and to be a good weapon platform. A
fly-off by USAF test pilots of the two competing designs took place between 10
October and 9 December 1972. While the YA-9 fully met the USAF's requirements,
the YA-10 was declared the winner on 18 January 1973. The use of the
established TF34 engine rather than the untried F102 by the YA-10 may have been
preferred by the Air Force, while Fairchild had no alternative work available
and was unlikely to survive if it did not win the A-X contract.
The two YA-9 prototypes were subsequently relegated to NASA for continued flight
testing before being retired. When retired, the YA-9s' custom-built engines were
removed and were later mated to a C-8 Buffalo airframe as part of the
NASA-Boeing joint Quiet Short-haul Research Aircraft (QSRA) study into a quiet
short-haul commercial aircraft.
Specifications (YA-9A)
General characteristics
Crew: 1
Length: 53 ft 6 in (16.31 m)
Wingspan: 58 ft 0 in (17.68 m)
Height: 16 ft 11 in (5.16 m)
Wing area: 580 sq ft (54 m2)
Gross weight: 25,000 lb (11,340 kg)
Max takeoff weight: 41,000 lb (18,597 kg)
Powerplant: 2 × Lycoming YF102-LD-100 turbofan engines, 7,200 lbf (32 kN) thrust
each
Performance
Rate of climb: 5,000 ft/min (25 m/s)
Armament
1x 20 mm M61 Vulcan Gatling gun (Substitute for GAU-8/A)
Up to 16,000 lb (7,260 kg) of ordnance
*