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.
Design
The A-9 was a high-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prototypes, which would have been replaced by titanium if production occurred)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 (16.30 m)
Wingspan: 58 ft 0 in (17.68 m)
Height: 16 ft 11 in (5.15 m)
Wing area: 580 sq ft (53.88 m2)
Loaded weight: 25,000 lb (11,340 kg)
Max. takeoff weight: 41,000 lb (18,597 kg)
Performance
Maximum speed: 520 mph (837 km/h)
Combat radius: 288 mi (463 km)
Rate of climb: 5000 ft/min (25.4 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
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