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Hughes 369 / 500 / OH-6



Both the Hughes 500 and the Bell Jet-Ranger, rivals in the light turbine helicopter market, were commercial outgrowths of the U.S. Army light observation helicopter competition between 1961 and 1965. Hughes won, and their vehicle became the OH-6A, a machine greatly respected for its agility and survivability in combat. Unencumbered by the production of LOHs, Bell put their design into commercial production, beating Hughes to the civilian marketplace by several years. Then the Texas firm outbid Hughes in a follow-on military production procurement and eventually sold more LOHs to the Army than had the original winner of the competition.

First flown in February 1963, the Hughes Model 369 prototype won the US Army’s Light Observation Helicopter contest against Bell and Hiller helicopters, and was ordered into large-scale production. The OH-6A Cayuse (the initial production model) entered service in September 1966. Production was curtailed at 1,434 units out of a planned 4,000, however, when costs rose and production rate fell. The Cayuse proved well suited to the Vietnam War, where it flew armed missions with a multi-barrel machine gun or 40-mm grenade launcher. Some surviving helicopters have been upgraded to OH-6D standard with more advanced electronics and heavier armament. Owing to military orders, it didn’t become available to commercial operators until 1967. It was offered in three versions, the 369HM military export model, 369HE commercial executive model ad 369HS standard model, the difference between the three being in the interior equipment fit. The 369HE was dropped in 1970 after only 25 had been built. The first civilian 500s, powered by the 317-shp Allison 250-C18A derated to 278 shp for five minutes operation and 243 shp for continuous use, were delivered in late 1966, but only a few were available.

The Model 369 was marketed as the 500 Series, with the 369HS as the Series 500C, and 369D as Series 500D.

In 1972, the 400-shp C20 version of the engine was installed in the 500C to provide better density-altitude performance, but the C's 2,550-pound gross weight and 126-knot cruising speed remained identical to the 500's since their rotor systems, transmissions and derated horsepower were the same.


Hughes 500C


In 1975, Hughes started on a 500D model that would be produced with a five-blade rotor system, the 420-shp Allison 250-C20B turbine, a new transmission capable of absorbing 375 shp for takeoff-350 for continuous use and a horizontal T tailplane for improved longitudinal stability. To provide adequate anti-torque control for the more powerful engine and rotor system, the tall boom would be strengthened and extended two inches, and the tail rotor diameter would be increased four inches. The underbelly of the distinctive egg-shaped 500 fuselage also would be strengthened, as would the gear struts, to accept higher gross weights; and the plexiglass canopy supports would be beefed up to withstand the greater air loads imposed by the aircraft's higher airspeeds.

The five-blade rotor system would enable the 500D to lift a one-ton sling load and have a 3,000-pound gross weight with internally carried items. Because its lifting capacity would be distributed over five blades, the D would be quieter than its four-blade predecessor when both models were operating at identical weights; each blade of the D model could be at a lower collective pitch angle, where the aerodynamic noise produced would be less, yet the total lift generated by the set of five blades would be equivalent to the performance of the four-blade system. Weight saved by using elastomeric lead-lag dampers in place of the heavier friction dampers employed on the earlier 500 models would offset the weight of the fifth blade, even though each blade would have double the number of structural ribs near the rotor tips to compensate for the helicopter's higher lifting capability.


Hughes 500 D


When the 500D finally was granted a type certificate in 1976, its test program had been as extensive and time-consuming as the licensing of an original design. The 500D is an original design in ways that are significant to the operator: there's a 28-percent increase in useful internal load and a 12-per-cent increase in maximum cruising speed over the 500C, which had been the fastest light helicopter. Projected maintenance costs have been reduced by extension of replacement and overhaul times for many costly components. Hughes anticipates that the main gearbox TBO (now 1,800 hours) will be raised to 5,000 hours; the C model gearbox's TBO is 1,200 hours. After more flight time has been put on customer ships, Hughes expects the engine TBO to reach 3,000 hours, and the minimum time to replacement for any component will be 5,000 hours. With a maximum speed of 152 knots at reduced weights and a comfortable 140-knot cruise, the Hughes 500D has fixed-wing cross-country performance.



Breda Nardi Costruzioni Aeronautiche SpA  was established on February 15,1971 by Nardi SA per Costruzioni Aeronautiche, and Breda, a member company of the EFIM state-owned financial group, each with a 50 percent holding. Initiated manufacture of helicopters under a license granted by Hughes Helicopters, and is building the Hughes 300C, 500C, 500D, and 500M under the respective designations of Breda Nardi NH-300C, NH- 500C, NH-500D, and NH-500M-D (TOW). The last is a multirole military helicopter armed with TOW missiles.

The model 500E is essentially a 500D with a more streamlined nose, thereby giving the front seat passengers extra leg room, and larger tail fins. These should not be confused with the earlier 500E which was simply a 500 with an executive interior. Only a few were built.


Model 500/530 Defender  - A series of Defender military helicopters is based on the Model 500/530 civilian range. Available were the 500MD Scout Defender, which is the basic military variant armed with gun and rocket pods; the 500MD/TOW Defender with four TOW anti-tank missiles and standard stabilised sight or optional mast-mounted sight; the 500MD/ASW Defender with nose mounted search radar, towed MAD, and torpedo armament; and the 500MD Defender II multimission version, with optional mast-mounted sight, TOW and Stinger missiles, Flir, an infrared supression system, and upgraded avionics. The 500MG and 530MG Defenders, the latter with an uprated 317kW Allison 250-C30 engine, are multirole helicopters intended primarily for anti-armour and attack missions. The 530MG features an advanced cockpit and control system. Operational equipment is similar to that of the 500MD Defender, but in addition a Racal RAMS 3000 integrated control and display system, operating with a MIL 1553B digital databus, is used for adverse weather or nap-of-the-earth flying. A Nightfox version is also available for enhanced night operations, using Flir and night vision goggles.
The last 369E built under the Hughes name was cn 0179, all later being McDonnell Douglas Helicopters.
The 369FF is basically a 369F with an up-graded drive system.

February 19, 1999 : Boeing sold MD commercial line to RDM The dutch company bought the ex Mc Donnell Douglas models MD 500E and MD 530F single-engine helicopters with conventional tail rotors, the MD 520N and MD 600N single-engine NOTAR helicopters and the MD Explorer series of twin-engine, eight-place helicopters.



Engine: Allison, 317 shp derated to 278 shp.

Engine Allison 250-C20, 400 shp.
Takeoff power 278 shp.
Max continuous power 243 shp.
Shortest service life, limited component: tailboom 2,030 hrs.
Disc loading 4.68 lbs/sq ft.
Power loading 9.2 lbs./hp.
Max. sling load 1,600 lbs.
Seating 5/7.
Gross weight 2,550 lbs.
External load gross 3,000 lb.
Empty weight 1,240 lbs.
Useful load 1,310 lbs.
Fuel capacity 64 USG/412 lbs.
Overall length, including rotor disc 30.3 ft.
Height 8.5 ft.
Max. cruise speed, sea level 125 knots.
Max. cruise speed. 4,000 ft: 126 knots.
Max. range, sea level 300 nm.
Max. range, 4,000 ft 328 nm.
Max. rate of climb 1,700 fpm.
Service ceiling 14,500 ft.
HIGE 12,900 ft.
HOGE 6,700 ft.
Vne SL: 130kt, 6000ft: 142 kt.
Max side-wind hover 20 kt.

Engine: Allison 250-C20B, 420 shp.
TBO: 1,500 hrs hot section, 3000 hrs.
Main rotor: five-blade, fully articulating, 26.4 ft.
Seats: 5.
Length: 30.5 ft.
Height: 8.9 ft.
Max ramp weight: 3000 lbs.
Max takeoff weight: 3000 lbs.
Standard empty weight: 1620 lbs.
Max useful load: 1380 lbs.
Max landing weight: 3000 lbs.
Max sling load: 2000 lbs.
Disc loading: 5.5 lbs/sq.ft.
Power loading: 7.1 lbs/hp.
Usable fuel capacity 64 USG/432 lbs.
Max rate of climb: 1900 fpm.
Service ceiling: 15,000 ft.
Hover in ground effect: 8500 ft.
Hover out of ground effect: 7500 ft.
Max speed: 143 kts.
Maximum cruise 139 kts.
Economy cruise 130 kts.
Duration at max cruise 1.8 hrs.
Normal cruise @ 3000 ft: 143 kts.
Fuel flow @ normal cruise: 189 pph.
Endurance @ normal cruise: 2 hr.
Minimum-time component  tail-rotor hub.
Minimum replacement time 2,440 hrs.

Engine: Allison 250‑C18A turboshaft, 317 shp TO, 243 shp Max continuous
Rotor diameter: 26 ft 4 in / 8.03 m
Fuselage length: 23 ft 0 in / 7.01 m
Empty weight: 1088 lb / 493 kg
Max normal TOW: 2550 lb / 1157 kg
Max overload TOW: 3000 lb / 1360 kg
Max range cruise SL: 117 kt / 135 mph / 217 kph
ROC SL: 700 fpm / 518 m/min
Service ceiling: 14,400 ft / 4390 m
Range at 4000ft/1220m: 327 nm / 377 mi / 606 km
Seats: 5
Cabin length: 8 ft 0 in / 2.44 m
Cabin width: 4 ft 6 in / 1.37 m
Cabin height: 4 ft 3.5 in / 1.31 m


OH-6A Cayuse
Engine: one 317-shp (236-kW) Allison T63-A-5A turboshaft derated to 215 shp (160 kW).
Maximum speed 130 kts / 150 mph (241 kp h) at sea level
Cruising speed : 117 kts / 216 km/h
Initial climb rate 1,840 ft (561 m) per minute
Service ceiling 15,800 ft (4,815 m
Range 413 miles (665 km).
Empty weight: 1,156 lb (524 kg)
Maximum take-off weight: 2,700 lb (1,225 kg).
Main rotor diameter 26 ft 4 in (8.03 m)
Length overall, rotors turning 30 ft 9.5 in (9.39 m)
Fuselage length: 22.999 ft / 7.01 m
Height 8 ft 1.5 in (2.48 m)
Main rotor disc area 544.63 sq ft (50.60 sq.m).
Payload: four passengers or 431kg freight.

Hughes 369E (500E)
Engine: Allison 250-C20B, 420 hp.

Engine: 1 x Allison 250-C20R, 280 kW (375 shp).


Hughes 500D





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