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OH-6 Cayuse McDonnell Douglas
MD 500/
OH-6 Cayuse
Light Helicopter
(military and civil)

DESCRIPTION:
When the US Army put forth a requirement for 4,000 new helicopters to fulfill a variety of support and combat duties, a number of helicopter and airplane manufacturers submitted bids for designs. Ultimately, Bell and Hiller were selected to build prototypes to compete in the Light Observation Helicopter (LOH) program. In a controversial move, the newly-formed Hughes Helicopter was also permitted to participate. Though the Hiller design was generally considered to be the best of the three entrants, the industry was stunned when Hughes was announced the winner of such a massive contract. In its favor, the Hughes 369 was a remarkably small and agile design, but the project was so fraught with cost overruns and engineering difficulties that the Army cancelled production after only some 1,400 of the projected 4,000 had been built. The type did prove valuable in Vietnam but was soon relegated to second-line units after the Army awarded a new LOH contract to the Bell OH-58.
Despite these difficulties, Hughes proceeded to develop a civil version, the MD 500, that has become one of the most popular civil helicopters in history. The latest versions include the 520N/600N which use a NOTAR (No TAil Rotor) system. Instead of using a traditional tail rotor to counteract torque, NOTAR employs an air jet at the end of the tail boom. More advanced military versions based on the civil variants have also been developed, namely the 500MG and 530MG Defender series.
In addition to the US Army and other militaries, major users of the MD 500 include police departments and border patrol agencies. Including all variants, over 4,000 MD 500 helicopters have been built including about 100 NOTAR models.
Data below for OH-6A, 500E, 500M, 500MD, 500MG, 520N, 530N, 530MG, and 600N where noted
Last modified 15 April 2011

HISTORY:

First Flight 27 February 1963

Service Entry

(OH-6) September 1966

CREW: two: pilot, co-pilot

PASSENGERS: (500E) 2-4
(OH-6) 4 armed troops
(500MG) 7 armed troops or 2 stretchers
(600N) 7-8

ESTIMATED COST:

unknown

AIRFOIL SECTIONS:

Rotor Blade Root NACA 0012

Rotor Blade Tip

NACA 0012

DIMENSIONS:

Length (OH-6) 30.31 ft (9.24 m) rotors turning
(OH-6) 23.00 ft (7.01 m) ignoring rotors
(500E) 28.25 ft (8.61 m) rotors turning
(500MD) 30.83 ft (9.40 m) rotors turning
(500MD) 25.00 ft (7.62 m) ignoring rotors
(500MG) 32.08 ft (9.78 m) rotors turning
(500MG) 23.92 ft (7.29 m) ignoring rotors
(520N) 32.10 ft (9.78 m) rotor turning
(530N) 28.50 ft (8.33 m) rotor turning

Rotor Diameter (OH-6/500M) 26.33 ft (8.03 m), 4-bladed rotor
(500MD/530) 27.33 ft (8.33 m), 5-bladed rotor

Width (rotor folded) (500E) 6.25 ft (1.91 m)
(500MG) 6.42 ft (1.96 m)
(520N) 6.60 ft (2.01 m)

Height (OH-6) 8.13 ft (2.48 m) to top of rotor head
(500) 8.67 ft (2.64 m) to top of rotor head
(500) 11.19 ft (3.41 m) with mast-mounted sight
(530N) 9.00 ft (2.74 m) to top of rotor head

Rotor Disk Area

(OH-6) 544.63 ft² (50.60 m²)

WEIGHTS:

Empty (OH-6) 1,230 lb (560 kg)
(500E) 1,445 lb (655 kg)
(500MD) 1,975 lb (895 kg)
(500MG) 1,980 lb (900 kg)
(530N) 1,635 lb (740 kg)

Normal Takeoff unknown

Max Takeoff (OH-6) 2,400 lb (1,090 kg)
(OH-6) 2,700 lb (1,225 kg) [overloaded]
(500E) 3,000 lb (1,360 kg)
(500MD) 3,000 lb (1,360 kg)
(500MG) 3,550 lb (1,610 kg)
(530N) 3,350 lb (1,550 kg)

Fuel Capacity internal: unknown
external: unknown

Max Payload

(OH-6) 1,000 lb (455 kg)

PROPULSION:

Powerplant (OH-6) one Allison T63-5A turboshaft
(500E) one Allison 250-C20B turboshaft
(500M) one Allison 250-C18 turboshaft
(500MD) one Allison 250-C20B turboshaft
(500MG) one Allison 250-C30B turboshaft
(520N) one Allison 250-C20R turboshaft
(530F) one Allison 250-C30 turboshaft

Thrust (OH-6) 252 shp (188 kW)
(500E) 350 shp (261 kW)
(500M) 278 shp (207 kW)
(500MD) 375 shp (280 kW)
(500MG) 425 shp (317 kW)
(520N) 375 shp (280 kW)
(530F) 425 shp (317 kW)
(530N) 650 shp (485 kW)

PERFORMANCE:

Max Level Speed at altitude: unknown
at sea level:
(OH-6) 150 mph (240 km/h)
(500E) 153 mph (245 km/h)
(520N) 156 mph (250 km/h)

Maximum Climb Rate (OH-6) 1,840 ft (560 m) / min
(500MD) 1,650 ft (505 m) / min
(500MG) 2,055 ft (625 m) / min

Service Ceiling unknown

Hover Ceiling
(out of ground effect) (OH-6) 7,300 ft (2,225 m)
(530MG) 14,100 ft (4,300 m)

Range typical:
(OH-6) 320 nm (595 km)
(500E) 235 nm (430 km)
(500MD) 210 nm (390 km)
(530MG) 180 nm (335 km)
(520N) 220 nm (440 km)
(530N) 190 nm (355 km)
ferry:
(OH-6) 1,930 nm (3,560 km)

Endurance (500MG) 1 hr 56 min

g-Limits unknown

ARMAMENT:

Gun provision for up to two .50 caliber guns, M230 30-mm chain guns, EX-34 7.62-mm chain guns with 2,000 rds, or GE 7.62-mm miniguns

Stations 2 external hardpoints and provision for 2 stub-wings with 2 hardpoints

Air-to-Air Missile AIM-92 Stinger

Air-to-Surface Missile BGM-71 TOW/TOW 2, Hellfire, Pescador, Mathogo

Bomb none

Other XM8/M129 40-mm grenade launcher with 150 rds, 7.62-mm machine gun pod, 12.7-mm machine gun pod, 2.75-in rocket pods, Mk 44 torpedo, Mk 46 torpedo, MAD sensors, ECM pods, searchlights

KNOWN VARIANTS:

Hughes 369 or HO-6 Original LOH entry and Army evaluation aircraft

OH-6A Production observation helicopter for the US Army; 1,434 built

OH-6B Upgrade standard to which many OH-6A models are being rebuilt, includes the addition of a FLIR system and a new engine

EH-6B Command and control model

MH-6B Little Bird Transport and utility model able to carry 6 troops on light assault missions, can be armed to support special operations forces

AH-6C Little Bird US Army special forces attack helicopter, can be equipped with guns, rockets, and missiles to provide support for air and ground special operations

AH-6E Improved attack helicopter used by US Army special forces units

MH-6E Stealthy light attack and transport helicopter for US Army special forces units

AH-6J Updated light attack helicopter based on the MD 530MG and equipped with an improved engine, FLIR, and a GPS/inertial navigation system

MH-6J Improved special forces transport similar to the AH-6J

TH-6 Trainer

500D Civil variant, also produced under license by Agusta (Italy), RACA (Argentina), Kawasaki (Japan), and Korean Air (South Korea)

500E Improved civil model

500M Military model for export based on the 500E

500MD Defender Improved military model based on the 500M with subvariants optimized for anti-tank (carrying TOW missiles), observation (Scout model), and naval (ASW model) missions

500MG Defender II Improved 500MD military model with a more powerful engine

520N NOTAR version of the MD 500 using the same cabin as earlier 500 models but a new tail boom housing the NOTAR system and an H-tail

530F Lifter Similar to the 500E but optimized for carrying cargo and other heavy lifting, an uprated engine allows better takeoff performance

530N Proposed improved version of the 520N with an uprated engine for operation in high temperatures and altitudes, cancelled due to lack of interest

530MG Defender Advanced military model based on the 530N

600N Enlarged 520N with a 6-bladed rotor and a more powerful engine allowing carriage of 7-8 passengers, may also be called the 630N

KNOWN COMBAT RECORD:

Vietnam War (US Army, 1966-1972)
Panama - Operation Just Cause (US Army [AH-6], 1989)
Iraq - Operation Desert Storm (US Army, 1991)
Somalia - Operation Continue Hope (US Army [MD 500], 1993)

KNOWN OPERATORS:

Military Argentina, Comando de Aviación del Ejército Argentina (Argentine Army Air Arm)
Bahrain, Bahrain Amiri (Royal Bahraini Air Force)
Bolivia, Fuerza Aérea Boliviana (Bolivian Air Force)
Brazil, Aviação do Exército Brasileiro (Brazilian Army Aviation)
Chile, Fuerza Aérea de Chile (Chilean Air Force)
Colombia, Fuerza Aérea Colombiana (Columbian Air Force)
Colombia, Policía Nacional de Colombia (Columbian National Police)
Costa Rica, Fuerza Pública (Costa Rican Public Force)
Croatia, Hrvatske Zracne Snage (Croatian Air Force)
Cyprus (Cyprus Air Force)
Denmark, Kongelige Danske Flyvevåbnet (Royal Danish Air Force)
Dominican Republic, Fuerza Aérea Dominicana (Dominican Air Force)
Ecuador, Fuerza Aérea Equatoriana (Ecuadorian Air Force)
El Salvador (Salvadoran Air Force)
Finland, Suomen Ilmavoimat (Finnish Air Force)
Haiti
Honduras, Fuerza Aérea Hondureña (Honduran Air Force)
Indonesia, Tentara Nasional Indonesia - Angkatan Udara (Indonesian Air Force)
Iraq, Al Quwwat Al Jawwiya al Iraqiya (Iraqi Air Force)
Israel, Tsvah Haganah le Israel - Heyl Ha'Avir (Israeli Defence Force - Air Force)
Italy, Aeronautica Militare Italiana (Italian Air Force)
Japan, Nihon Rikujyo Jieitai (Japan Ground Self Defence Force)
Japan, Kaijo Jieitai (Japan Maritime Self Defence Force)
Japan, Kaijo Hoan-cho (Japan Coast Guard)
Jordan, Al Quwwat al-Jawwiya al-Malakiya al-Urduniya (Royal Jordanian Air Force)
Kenya (Kenya Air Force)
Mauritania (Mauritania Air Force)
Mexico, Fuerza Aérea Mexicana (Mexican Air Force)
Morocco, Al Quwwat al Jawiyya al Malakiya Marakishiya (Royal Moroccan Air Force)
Nicaragua, Fuerza Aérea - Ejército de Nicaragua (Nicaraguan Air Force)
North Korea (Korean People's Army Air Force)
Peru, Fuerza Aérea del Perú (Peruvian Air Force)
Philippines, Hukbong Himpapawid ng Pilipinas (Philippine Air Force)
South Korea, Han-guk Kong Goon (Republic of Korea Air Force)
Spain, Ejército del Aire Española (Spanish Air Force)
Taiwan, Zhonghuá Mínguó Haijun Lùzhàndùi (Republic of China Marine Corps)
Taiwan, Zhonghuá Mínguó Haijun (Republic of China Navy)
United States (US Army)
United States (US Navy)

Civil Greenlandair

3-VIEW SCHEMATIC:
OH-6 Cayuse:

MD 500MD:

SOURCES:

Aboulafia, Richard. Jane's Civil Aircraft. Glasgow: Harper Collins Publishers, 1996, p. 242-245.

Bishop, Chris, ed. The Encyclopedia of Modern Military Weapons: The Comprehensive Guide to Over 1,000 Weapon Systems from 1945 to the Present Day. NY: Barnes & Noble, 1999, p. 320.

Bonds, Ray, ed. The Modern US War Machine: An Encyclopedia of American Military Equipment and Strategy. NY: Military Press, 1987, p. 203.

Donald, David, ed. The Complete Encyclopedia of World Aircraft. NY: Barnes & Noble, 1997, p. 525-526, 618-619.

Gunston, Bill and Spick, Mike. Modern Fighting Helicopters. London: Salamander Books, 1998, p. 130-131.

MD Helicopters MD 500/600 site

Munro, Bob and Chant, Christopher. Jane's Combat Aircraft. Glasgow: Harper Collins Publishers, 1995, p. 160-161.

Rendall, David. Jane's Aircraft Recognition Guide, 2nd ed. London: Harper Collins Publishers, 1999, p. 423-425.

US Army OH-6 Fact Sheet

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	McDonnell Douglas MD 500/ OH-6 Cayuse Light Helicopter (military and civil)

DESCRIPTION: When the US Army put forth a requirement for 4,000 new helicopters to fulfill a variety of support and combat duties, a number of helicopter and airplane manufacturers submitted bids for designs. Ultimately, Bell and Hiller were selected to build prototypes to compete in the Light Observation Helicopter (LOH) program. In a controversial move, the newly-formed Hughes Helicopter was also permitted to participate. Though the Hiller design was generally considered to be the best of the three entrants, the industry was stunned when Hughes was announced the winner of such a massive contract. In its favor, the Hughes 369 was a remarkably small and agile design, but the project was so fraught with cost overruns and engineering difficulties that the Army cancelled production after only some 1,400 of the projected 4,000 had been built. The type did prove valuable in Vietnam but was soon relegated to second-line units after the Army awarded a new LOH contract to the Bell OH-58. Despite these difficulties, Hughes proceeded to develop a civil version, the MD 500, that has become one of the most popular civil helicopters in history. The latest versions include the 520N/600N which use a NOTAR (No TAil Rotor) system. Instead of using a traditional tail rotor to counteract torque, NOTAR employs an air jet at the end of the tail boom. More advanced military versions based on the civil variants have also been developed, namely the 500MG and 530MG Defender series. In addition to the US Army and other militaries, major users of the MD 500 include police departments and border patrol agencies. Including all variants, over 4,000 MD 500 helicopters have been built including about 100 NOTAR models. Data below for OH-6A, 500E, 500M, 500MD, 500MG, 520N, 530N, 530MG, and 600N where noted Last modified 15 April 2011
HISTORY:
First Flight	27 February 1963
Service Entry	(OH-6) September 1966
CREW:	two: pilot, co-pilot
PASSENGERS:	(500E) 2-4 (OH-6) 4 armed troops (500MG) 7 armed troops or 2 stretchers (600N) 7-8
ESTIMATED COST:	unknown
AIRFOIL SECTIONS:
Rotor Blade Root	NACA 0012
Rotor Blade Tip	NACA 0012
DIMENSIONS:
Length	(OH-6) 30.31 ft (9.24 m) rotors turning (OH-6) 23.00 ft (7.01 m) ignoring rotors (500E) 28.25 ft (8.61 m) rotors turning (500MD) 30.83 ft (9.40 m) rotors turning (500MD) 25.00 ft (7.62 m) ignoring rotors (500MG) 32.08 ft (9.78 m) rotors turning (500MG) 23.92 ft (7.29 m) ignoring rotors (520N) 32.10 ft (9.78 m) rotor turning (530N) 28.50 ft (8.33 m) rotor turning
Rotor Diameter	(OH-6/500M) 26.33 ft (8.03 m), 4-bladed rotor (500MD/530) 27.33 ft (8.33 m), 5-bladed rotor
Width (rotor folded)	(500E) 6.25 ft (1.91 m) (500MG) 6.42 ft (1.96 m) (520N) 6.60 ft (2.01 m)
Height	(OH-6) 8.13 ft (2.48 m) to top of rotor head (500) 8.67 ft (2.64 m) to top of rotor head (500) 11.19 ft (3.41 m) with mast-mounted sight (530N) 9.00 ft (2.74 m) to top of rotor head
Rotor Disk Area	(OH-6) 544.63 ft² (50.60 m²)
WEIGHTS:
Empty	(OH-6) 1,230 lb (560 kg) (500E) 1,445 lb (655 kg) (500MD) 1,975 lb (895 kg) (500MG) 1,980 lb (900 kg) (530N) 1,635 lb (740 kg)
Normal Takeoff	unknown
Max Takeoff	(OH-6) 2,400 lb (1,090 kg) (OH-6) 2,700 lb (1,225 kg) [overloaded] (500E) 3,000 lb (1,360 kg) (500MD) 3,000 lb (1,360 kg) (500MG) 3,550 lb (1,610 kg) (530N) 3,350 lb (1,550 kg)
Fuel Capacity	internal: unknown external: unknown
Max Payload	(OH-6) 1,000 lb (455 kg)
PROPULSION:
Powerplant	(OH-6) one Allison T63-5A turboshaft (500E) one Allison 250-C20B turboshaft (500M) one Allison 250-C18 turboshaft (500MD) one Allison 250-C20B turboshaft (500MG) one Allison 250-C30B turboshaft (520N) one Allison 250-C20R turboshaft (530F) one Allison 250-C30 turboshaft
Thrust	(OH-6) 252 shp (188 kW) (500E) 350 shp (261 kW) (500M) 278 shp (207 kW) (500MD) 375 shp (280 kW) (500MG) 425 shp (317 kW) (520N) 375 shp (280 kW) (530F) 425 shp (317 kW) (530N) 650 shp (485 kW)
PERFORMANCE:
Max Level Speed	at altitude: unknown at sea level: (OH-6) 150 mph (240 km/h) (500E) 153 mph (245 km/h) (520N) 156 mph (250 km/h)
Maximum Climb Rate	(OH-6) 1,840 ft (560 m) / min (500MD) 1,650 ft (505 m) / min (500MG) 2,055 ft (625 m) / min
Service Ceiling	unknown
Hover Ceiling (out of ground effect)	(OH-6) 7,300 ft (2,225 m) (530MG) 14,100 ft (4,300 m)
Range	typical: (OH-6) 320 nm (595 km) (500E) 235 nm (430 km) (500MD) 210 nm (390 km) (530MG) 180 nm (335 km) (520N) 220 nm (440 km) (530N) 190 nm (355 km) ferry: (OH-6) 1,930 nm (3,560 km)
Endurance	(500MG) 1 hr 56 min
g-Limits	unknown
ARMAMENT:
Gun	provision for up to two .50 caliber guns, M230 30-mm chain guns, EX-34 7.62-mm chain guns with 2,000 rds, or GE 7.62-mm miniguns
Stations	2 external hardpoints and provision for 2 stub-wings with 2 hardpoints
Air-to-Air Missile	AIM-92 Stinger
Air-to-Surface Missile	BGM-71 TOW/TOW 2, Hellfire, Pescador, Mathogo
Bomb	none
Other	XM8/M129 40-mm grenade launcher with 150 rds, 7.62-mm machine gun pod, 12.7-mm machine gun pod, 2.75-in rocket pods, Mk 44 torpedo, Mk 46 torpedo, MAD sensors, ECM pods, searchlights
KNOWN VARIANTS:
Hughes 369 or HO-6	Original LOH entry and Army evaluation aircraft
OH-6A	Production observation helicopter for the US Army; 1,434 built
OH-6B	Upgrade standard to which many OH-6A models are being rebuilt, includes the addition of a FLIR system and a new engine
EH-6B	Command and control model
MH-6B Little Bird	Transport and utility model able to carry 6 troops on light assault missions, can be armed to support special operations forces
AH-6C Little Bird	US Army special forces attack helicopter, can be equipped with guns, rockets, and missiles to provide support for air and ground special operations
AH-6E	Improved attack helicopter used by US Army special forces units
MH-6E	Stealthy light attack and transport helicopter for US Army special forces units
AH-6J	Updated light attack helicopter based on the MD 530MG and equipped with an improved engine, FLIR, and a GPS/inertial navigation system
MH-6J	Improved special forces transport similar to the AH-6J
TH-6	Trainer
500D	Civil variant, also produced under license by Agusta (Italy), RACA (Argentina), Kawasaki (Japan), and Korean Air (South Korea)
500E	Improved civil model
500M	Military model for export based on the 500E
500MD Defender	Improved military model based on the 500M with subvariants optimized for anti-tank (carrying TOW missiles), observation (Scout model), and naval (ASW model) missions
500MG Defender II	Improved 500MD military model with a more powerful engine
520N	NOTAR version of the MD 500 using the same cabin as earlier 500 models but a new tail boom housing the NOTAR system and an H-tail
530F Lifter	Similar to the 500E but optimized for carrying cargo and other heavy lifting, an uprated engine allows better takeoff performance
530N	Proposed improved version of the 520N with an uprated engine for operation in high temperatures and altitudes, cancelled due to lack of interest
530MG Defender	Advanced military model based on the 530N
600N	Enlarged 520N with a 6-bladed rotor and a more powerful engine allowing carriage of 7-8 passengers, may also be called the 630N
KNOWN COMBAT RECORD:	Vietnam War (US Army, 1966-1972) Panama - Operation Just Cause (US Army [AH-6], 1989) Iraq - Operation Desert Storm (US Army, 1991) Somalia - Operation Continue Hope (US Army [MD 500], 1993)
KNOWN OPERATORS:
Military	Argentina, Comando de Aviación del Ejército Argentina (Argentine Army Air Arm) Bahrain, Bahrain Amiri (Royal Bahraini Air Force) Bolivia, Fuerza Aérea Boliviana (Bolivian Air Force) Brazil, Aviação do Exército Brasileiro (Brazilian Army Aviation) Chile, Fuerza Aérea de Chile (Chilean Air Force) Colombia, Fuerza Aérea Colombiana (Columbian Air Force) Colombia, Policía Nacional de Colombia (Columbian National Police) Costa Rica, Fuerza Pública (Costa Rican Public Force) Croatia, Hrvatske Zracne Snage (Croatian Air Force) Cyprus (Cyprus Air Force) Denmark, Kongelige Danske Flyvevåbnet (Royal Danish Air Force) Dominican Republic, Fuerza Aérea Dominicana (Dominican Air Force) Ecuador, Fuerza Aérea Equatoriana (Ecuadorian Air Force) El Salvador (Salvadoran Air Force) Finland, Suomen Ilmavoimat (Finnish Air Force) Haiti Honduras, Fuerza Aérea Hondureña (Honduran Air Force) Indonesia, Tentara Nasional Indonesia - Angkatan Udara (Indonesian Air Force) Iraq, Al Quwwat Al Jawwiya al Iraqiya (Iraqi Air Force) Israel, Tsvah Haganah le Israel - Heyl Ha'Avir (Israeli Defence Force - Air Force) Italy, Aeronautica Militare Italiana (Italian Air Force) Japan, Nihon Rikujyo Jieitai (Japan Ground Self Defence Force) Japan, Kaijo Jieitai (Japan Maritime Self Defence Force) Japan, Kaijo Hoan-cho (Japan Coast Guard) Jordan, Al Quwwat al-Jawwiya al-Malakiya al-Urduniya (Royal Jordanian Air Force) Kenya (Kenya Air Force) Mauritania (Mauritania Air Force) Mexico, Fuerza Aérea Mexicana (Mexican Air Force) Morocco, Al Quwwat al Jawiyya al Malakiya Marakishiya (Royal Moroccan Air Force) Nicaragua, Fuerza Aérea - Ejército de Nicaragua (Nicaraguan Air Force) North Korea (Korean People's Army Air Force) Peru, Fuerza Aérea del Perú (Peruvian Air Force) Philippines, Hukbong Himpapawid ng Pilipinas (Philippine Air Force) South Korea, Han-guk Kong Goon (Republic of Korea Air Force) Spain, Ejército del Aire Española (Spanish Air Force) Taiwan, Zhonghuá Mínguó Haijun Lùzhàndùi (Republic of China Marine Corps) Taiwan, Zhonghuá Mínguó Haijun (Republic of China Navy) United States (US Army) United States (US Navy)
Civil	Greenlandair
3-VIEW SCHEMATIC: *OH-6 Cayuse:* *MD 500MD:*
SOURCES: Aboulafia, Richard. Jane's Civil Aircraft. Glasgow: Harper Collins Publishers, 1996, p. 242-245. Bishop, Chris, ed. The Encyclopedia of Modern Military Weapons: The Comprehensive Guide to Over 1,000 Weapon Systems from 1945 to the Present Day. NY: Barnes & Noble, 1999, p. 320. Bonds, Ray, ed. The Modern US War Machine: An Encyclopedia of American Military Equipment and Strategy. NY: Military Press, 1987, p. 203. Donald, David, ed. The Complete Encyclopedia of World Aircraft. NY: Barnes & Noble, 1997, p. 525-526, 618-619. Gunston, Bill and Spick, Mike. Modern Fighting Helicopters. London: Salamander Books, 1998, p. 130-131. MD Helicopters MD 500/600 site Munro, Bob and Chant, Christopher. Jane's Combat Aircraft. Glasgow: Harper Collins Publishers, 1995, p. 160-161. Rendall, David. Jane's Aircraft Recognition Guide, 2nd ed. London: Harper Collins Publishers, 1999, p. 423-425. US Army OH-6 Fact Sheet