Daily Archives: September 27, 2023

27 September 2008

Sikorsky MH-53M Pave Low IV, 68-8284, “Cowboy 26,” prepares for its final combat mission, Iraq, 27 September 2008. (A1C Jason Epley, U.S. Air Force)

27 September 2008: A United States Air Force Sikorsky MH-53M Pave Low IV special operations helicopter, serial number 68-8284, assigned to the 20th Expeditionary Special Operations Squadron, flew its final combat mission before being withdrawn from service and retired after 40 years and 12,066.6 flight hours.

“Cowboy 26” was flown by Major Philip Cooper, Captain Peter Hettinger, and Colonel Scott Howell, with Technical Sergeant Henry Woodie, Staff Sergeant Shawn Lewis, Senior Airman Eric Harp, and Airman 1st Class Joshua Lucas.

68-8284 was built by the Sikorsky Aircraft Corporation at Bloomfield, Connecticut, as one of 40 HH-53C Super Jolly Green Giants for Combat Search and Rescue (CSAR). It was delivered to the Air Force in August 1968. 68-8284 was assigned to the 40th Air Rescue and Recovery Squadron  at Nakhon Phanom Royal Thai Air Force Base, 1971–1972. It operated as “Jolly Green 55.”

On 5 September 1971, with flight crew Major Jerry R. Thompson, Gary L. Gamble (CP),  FE Raymond Duarte and PJs William D. Brinson and Michael D Vogele, it rescued the survivors of “Knife 33,” a 21st SOS CH-3E that went down in Laos. On 19 December 1971 (Capt Harold O. Jones (P), David G. Daus (CP), FE Jerrold T. Dearmans, with PJs Leon Fullwood and William D. Brinson, the crew of Falcon 74, a 13th TFS/432 TFW F-4D Phantom II which had gone down shot down 17 December by a SAM near Ban Poung Ban in northeastern Laos. Maj. William T. Stanley, Capt. Lester O’Brien were safely recovered.

A U.S. Air Force Sikorsky HH-53C Super Jolly Green Giant hovers to hoist a pararescueman with one downed pilot, while a second waits on the ground, 16 June 1967. The blade tip vortices are visible because of the high humidity. (This image has been reoriented and cropped from the original photograph.) (National Archives at College Park)

8284 was later assigned to the 67th Aerospace Rescue and Recovery Squadron (39th Aerospace Rescue and Recovery Wing) at RAF Woodbridge, Suffolk, England. 68-8284 has been constantly modernized and upgraded. It was initially converted to the MH-53J Pave Low III/Enhanced configuration by the Naval Air Rework Facility, NAS Pensacola, Florida, in the late 1980s. The helicopter was further modified to the MH-53M Pave Low IV configuration at the Naval Air Depot, MCAS Cherry Point, North Carolina.

The MH-53M Pave Low IV is designed for operations in darkness. (Staff Sergeant Aaron Allmon, U.S. Air Force) 080927-F-7823A-433

The MH-53M Pave Low IV is a variant of Sikorsky’s S-65 heavy-lift military transport helicopter series.  The MH-53M is a single main rotor, single tail rotor, twin-engine helicopter. It has a crew of six: 2 pilots, 2 flight engineers and 2 gunners. The Pave Low IV is equipped with Terrain-Following Radar and Forward Looking Infrared (FLIR) for low-level operations in darkness and low visibility.

The MH-53M fuselage is 67 feet, 2.4 inches (20.483 meters) long, and the helicopter has a maximum length of 91 feet, 11.34 inches (28.025 meters) with rotors turning and the refueling boom extended. The height to the top of the main rotor pylon is 17 feet, 1.68 inches (5.224 meters). The maximum height (rotors turning) is 24 feet, 10.88 inches (7.592 meters).

Sikorsky HH-53C 3-view illustration with dimensions. (Sikorsky Historical Archives)

The fully-articulated 6-blade main rotor has a diameter of 72 feet, 2.7 inches (22.014 meters). The main rotor turns counter-clockwise at 185 r.p.m. (100% Nr), as seen from above. (The advancing blade is on the helicopter’s right.) The main rotor blades are built with titanium spars and have -16° of twist. The semi-articulated four-blade tail rotor has a diameter of 16 feet, 0 inches (4.877 meters) and is positioned on the left side of the tail pylon. It turns clockwise at 792 r.p.m., as seen from the helicopter’s left side. (The advancing blade is below the axis of rotation.) The gap between rotor arcs is just 4.437 inches (11.270 centimeters).

Empty, the MH-53M weighs 32,000 pounds (14,515 kilograms). Its maximum takeoff weight is 46,000 pounds (20,865 kilograms).

Its two General Electric T64-GE-100 axial-flow turboshaft engines have a Normal Continuous Power rating of 3,810 shaft horsepower at 85 °F. (30 °C.), Military Power rating of 4,090 shaft horsepower, and a Maximum Power rating of 4,330 shaft horsepower. The T64-GE-100 is 79 inches (2.007 meters) long, 20 inches (0.508 meters) in diameter and weighs 720 pounds (327 kilograms). Output (100% N2) is 13,600 r.p.m.

Two Sikorsky HH-53C Super Jolly Green Giants of the 39th Aerospace Rescue and Recovery Wing fly in formation over Goose Bay, Canada, 11 June 1978. 68-8284 is the ship closest to the camera, painted gray. (TSgt. Robert C. Leach/U.S. Air Force)
Two Sikorsky HH-53C Super Jolly Green Giants of the 39th Aerospace Rescue and Recovery Wing fly in formation over Goose Bay, Labrador, Canada, 11 June 1978. 68-8284 is the ship closest to the camera, painted gray. (TSgt. Robert C. Leach/U.S. Air Force)

The MH-53M has a maximum speed of 196 miles per hour (315 kilometers per hour) and a service ceiling of 16,000 feet (4877 meters). It carries two 450-gallon (1,703 liter) jettisonable fuel tanks under each sponson.

The MH-53M is armed with two M134 7.62mm miniguns and a GAU-18/A .50 caliber machine gun.

A Sikorsky MH-53J Pave Low III Enhanced from the 16th Special Operations Wing ready to refuel from a Lockheed MC-130E Combat Talon, 21 October 2001, classified location Operation Enduring Freedom. (TSGT Scott Reed, USAF) U.S. National Archives 6523525

At the time they were retired, the MH-53Ms were the fastest, heaviest, most powerful helicopters in the United States Air Force inventory.

After leaving Iraq, 68-8284 was transported by C-17 Globemaster III to England. It was loaned to the Royal Air Force Museum Cosford, where it is on display.

Sikorsky MH-53M Pave Low IV 68-8284 with another Pave Low IV on their final mission . 27 September 2008. (U.S. Air Force 080927-F-7823A-409)

Recommended: On a Steel Horse I Ride: A History of the MH-53 Pave Low Helicopters in War and Peace, by Darrel D. Whitcomb. Air University Press, Air Force Research Institute, Maxwell Air Force Base, Alabama, September 2012.

© 2019, Bryan R. Swopes

27 September 1964

Captain Michael N. Antoniou with YUH-1D 60-6029. (FAI)

27 September 1964: Captain Michael N. Antoniou flew the number two Bell YUH-1D-BF Iroquois, 60-6029, Bell Helicopter serial number 702, from Edwards Air Force Base in the high desert of southern California, non-stop to Rogers, Arkansas. The distance flown was 2,170.70 kilometers (1,348.81 miles), and established a Fédération Aéronautique Internationale (FAI) World Record for Distance Without Landing.¹

Captain Antoniou was a project test pilot assigned to the U.S. Army Aviation Test Activity at Edwards.

60-6029 was modified by Bell to reduce aerodynamic drag and weight. The windshield wipers, door handles, main rotor stabilizer bar and associated dampers, tail rotor drive shaft cover and 42° gear box cover had been removed. Gaps at the doors, crew steps, tail boom cargo compartment, etc., were sealed with tape.

Bell YUH-1D Iroquois 60-6029. (FAI)

The Bell Helicopter Co. UH-1D Iroquois (Model 205) was an improved variant the UH-1B (Model 204). The type’s initial military designation was HU-1, and this resulted in the helicopter being universally known as the “Huey.” The UH-1D has a larger passenger cabin, longer tail boom and increased main rotor diameter.

The UH-1D was a single main rotor/tail rotor medium helicopter powered by a turboshaft engine. It could be flown by a single pilot, but was commonly flown by two pilots in military service. The helicopter had an overall length of 57 feet, 0.67 inches (17.375 meters) with rotors turning. The fuselage was 41 feet, 5 inches (12.624 meters) long. The helicopter had a height of 13 feet, 7.4 inches (4.150 meters), measured to the top of the mast. The maximum gross weight of the UH-1D was 9,500 pounds (4,309.1 kilograms).

The two blade semi-rigid, under-slung main rotor had a diameter of 48 feet, 3.2 inches (14.712 meters), and turned counter clockwise when viewed from above. (The advancing blade is on the helicopter’s right.) At 100% NR, the main rotor turned 324 r.p.m. The two blade tail rotor assembly had a diameter of 8 feet, 6 inches (2.591 meters). It was on the left side of the pylon in a pusher configuration and turned counter-clockwise as seen from the helicopter’s left. (The advancing blade is above the axis of rotation.)

The YUH-1D was powered by a Lycoming T53-L-9 or -11 turboshaft engine which was rated at 1,100 shaft horsepower at 6,610 r.p.m., for takeoff (5 minute limit). The T53-L-11 was a two-shaft free turbine with a 6-stage compressor (5 axial-flow stages, 1 centrifugal-flow stage) and a 2-stage axial-flow turbine (1 high-pressure stage, and 1 low-pressure power turbine stage). As installed in the UH-1, the engine produced 115 pounds of jet thrust (511.55 Newtons) at Military Power.

Its maximum speed, VNE, was 124 knots (143 miles per hour, 230 kilometers per hour). With full fuel, 206.5 gallons (781.7 liters), the helicopter had a maximum endurance of three hours.

60-6029 was later modified to the prototype YUH-1H.

Captain Michael N. Antoniou with Bell YUH-1D-BF 60-6029 (c/n 702), circa 1965. (David Hatcher Collection)

¹ FAI Record File Number 2180

© 2018, Bryan R. Swopes

27 September 1956

Captain Milburn G. Apt, U.S. Air Force, with a Bell X-2. (U.S. Air Force)
Captain Milburn Grant Apt, United States Air Force, with a Bell X-2. (U. S. Air Force)

27 September 1956: Captain Milburn G. (“Mel”) Apt, United States Air Force, was an experimental test pilot assigned to the Air Force Flight Test Center at Edwards Air Force Base, California. After Frank Everest and Iven Kincheloe had made twelve powered flights in the Bell X-2 supersonic research aircraft, Mel Apt was the next test pilot to fly it.

The X-2 was a joint project of the U.S. Air Force and NACA (the National Advisory Committee on Aeronautics, the predecessor of NASA). The rocketplane was designed and built by Bell Aircraft Corporation of Buffalo, New York, to explore supersonic flight at speeds beyond the capabilities of the earlier Bell X-1 and Douglas D-558-II Skyrocket.

In addition to the aerodynamic effects of speeds in the Mach 2.0–Mach 3.0 range, engineers knew that the high temperatures created by aerodynamic friction would be a problem, so the aircraft was built from stainless steel and K-Monel, a copper-nickel alloy.

The Bell Aircraft Corporation X-2 was 37 feet, 10 inches (11.532 meters) long with a wingspan of 32 feet, 3 inches (9.830 meters) and height of 11 feet, 10 inches (3.607 meters). Its empty weight was 12,375 pounds (5,613 kilograms) and loaded weight was 24,910 pounds (11,299 kilograms).

Bell X-2 46-675 on its transportation dolly at Edwards Air Force Base, California, 1952. (NASA)
The second of two Bell X-2 supersonic research rocketplanes, 46-675, on its transportation dolly at Edwards Air Force Base, California, 1952. On 12 May 1953 this X-2 exploded during a captive test flight, killing Bell’s test pilot Jean L. “Skip” Ziegler. (NASA)

The X-2 was powered by a throttleable two-chamber Curtiss-Wright XLR25-CW-1 rocket engine that produced 2,500–15,000 pounds of thrust (11.12–66.72 kilonewtons)

Rather than use its limited fuel capacity to take off and climb to altitude, the X-2 was dropped from a modified heavy bomber as had been the earlier rocketplanes. A four-engine Boeing B-50D-95-BO Superfortress bomber, serial number 48-096, was modified as the drop ship and redesignated EB-50D.

The launch altitude was 30,000 feet (9,144 meters). After the fuel was exhausted, the X-2 glided to a touchdown on Rogers Dry Lake at Edwards Air Force Base.

Bell X-2 46-674 after drop from Boeing EB-50D Superfortress 48-096. (U.S. Air Force)
Bell X-2 46-674 after drop from Boeing EB-50D Superfortress 48-096. (U.S. Air Force)

With Mel Apt in the cockpit on his first rocketplane flight, the B-50 carried the X-2 to 31,800 feet (9,693 meters). After it was dropped from the bomber, Apt ignited the rocket engine and began to accelerate. He passed Mach 1 at 44,000 feet (13,411 meters) and continued to climb. Apt flew an “extraordinarily precise profile” to reach 72,200 feet (22,007 meters) where he put the X-2 into a dive. The rocket engine burned 12.5 seconds longer than planned, and at 65,589 feet (19,992 meters) the X-2 reached Mach 3.196 (2,094 miles per hour, 3,377 kilometers per hour).

Milburn Apt was the first pilot to exceed Mach 3. He was The Fastest Man Alive.

Bell X-2 46-674 in flight over Southern California, 1955–56. Note the supersonic diamond-shaped shock waves in the rocket engine's exhaust. (Bell aircraft Corporation)
Bell X-2 46-674 in flight over Southern California, 1955–56. Note the supersonic diamond-shaped shock waves in the rocket engine’s exhaust. (Bell Aircraft Corporation)

It was known that the X-2 could be unstable in high speed maneuvers. The flight plan called for Apt to slow to Mach 2.4 before beginning a gradual turn back toward Rogers Dry Lake where he was to land, but he began the turn while still at Mach 3. Twenty seconds after engine burn out, the X-2 began to oscillate in all axes and departed controlled flight. His last radio transmission was, “There she goes.” ¹

Mel Apt was subjected to acceleration forces of ± 6 Gs. It is believed that he was momentarily unconscious. Out of control, the X-2 fell through 40,000 feet (12,192 meters) in an inverted spin. Apt initiated the escape capsule separation, in which the entire nose of the X-2 was released from the airframe. It pitched down violently and Mel Apt was knocked unconscious again. He regained consciousness a second time and tried to parachute from the escape capsule, but was still inside when it hit the desert floor at several hundred miles per hour. Mel Apt was killed instantly.

Since 1950, Milburn G. Apt was the thirteenth test pilot killed at Edwards Air Force Base.

Wreckage of the Bell X-2, 46-674. (U.S. Air Force)
Wreckage of the Bell X-2, 46-674, in the Kramer Hills, east of Edwards Air Force Base. (U.S. Air Force)
Wreckage of the Bell X-2, 46-674. (NASM 9A08208)

Milburn Grant Apt was born at Buffalo, Kansas, 8 April 1924. He was the third child of Oley Glen Apt, a farmer, and Ada Willoughby Apt.

“Mel” Apt enlisted as a private in the Air Corps Enlisted Reserve, United States Army, 9 November 1942. On 23 June 1943, Private Apt was appointed an Aviation Cadet. After completing flight training, Cadet Apt was commissioned a Second Lieutenant, Army of the United States (A.U.S.). He was promoted to First Lieutenant, A.U.S., 4 September 1945. Apt was released from active duty on 11 August 1946. On 10 October 1947, he was reclassified as a Second Lieutenant, Air Corps, United States Army, with date of rank 8 April 1945.

In February 1950, Lieutenant Apt, then stationed at Williams Air Force Base, Arizona, married Miss Faye Lorrie Baker of Phoenix. They would have two children.

Mel Apt earned a Bachelor of Science degree from the University of Kansas, Lawrence, Kansas, in 1951, and a second bachelor’s degree in aeronautical engineering from the Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio. He then attended the U.S. Air Force Experimental Test Pilot School at Edwards Air Force Base, California, graduating in September 1954. Apt was assigned to the Fighter Operations Branch, Air Force Flight Test Center, as a test pilot.

On 22 December 1954, Captain Apt was flying a chase plane during a test at Edwards. The test aircraft crash-landed on the dry lake and caught fire with its pilot trapped inside. Mel Apt, with his bare hands, rescued the other test pilot, saving his life. For this courageous act, he was awarded the Soldier’s Medal.

Captain Apt was posthumously awarded the Distinguished Flying Cross for his flight in the X-2. The medal was presented to his widow in a ceremony at Edwards in March 1957.

Captain Milburn Grant Apt, United States Air Force, was 32 years old at the time of his death. His remains were buried at the Buffalo Cemetery, Buffalo, Kansas.

Captain Iven Carl Kincheloe and Captain Milburn Grant Apt (seated in cockpit) with the Bell X-2 at Edwards Air Force Base, 1956. (Jet Pilot Overseas)

¹ Recommended: Coupling Dynamics in Aircraft: A Historical Perspective, by Richard E. Day, Dryden Flight Research Center, Edwards AFB, California NASA Special Publications 532, 1997.

© 2018, Bryan R. Swopes

27 September 1946

Geoffrey Raoul de Havilland, Jr. (Sport & General Press Agency, Ltd, 1 September 1946; © National Portrait Gallery, London. NPG x184369)

27 September 1946: Geoffrey Raoul de Havilland, Jr., O.B.E., Chief Test Pilot of the de Havilland Aircraft Co., Ltd., and the son of the firm’s founder, was killed during a test flight of a prototype DH.108 Swallow, TG306.

Geoffrey de Havilland, Jr., in the cockpit of the second DH.108 Swallow prototype, TG/306. (Flight)
Geoffrey de Havilland, Jr., in the cockpit of the second DH.108 Swallow prototype, TG306. (FLIGHT)

De Havilland had taken off from the company airfield at Hatfield at 5:26 p.m. for a planned 45 minute flight. Flying over the Thames Estuary, east of London, England, de Havilland put the swept-wing jet into a high-speed dive from 10,000 feet (3,048 meters). As it approached 5,000 feet (1,524 meters) at 0.88 Mach, (658 miles per hour, 1,060 kilometers per hour), the shock waves building up along the wings’ leading edges disrupted the air flow over the wings, causing them to stall. TG306 pitched violently downward. A NASA report called this “. . . an undamped violently divergent longitudinal pitching oscillation at Mach 0.875. . . .”  The extreme aerodynamic loads cracked the main spar and both wings failed. The DH.108 crashed into Egypt Bay, Gravesend, Kent.

The wreck was located the following day. The body of Geoffrey de Havilland was found ten days later. He had suffered a broken neck and fractured skull as a result of his head striking the canopy during the violent oscillations of the aircraft.

(Grace’s Guide)

FLIGHT reported:

Geoffrey de Havilland was one of the outstanding test pilots in the country, and his work has played a vital part in the perfecting of such noteworthy types as the Mosquito, Hornet, Vampire and 108. His death is a serious blow not only to the company but to the country, for in the exploration of the unknown threshold of sonic flight, a combination of skill and cool courage are qualities demanding the utmost of test pilots. Geoffrey de Havilland had these qualities in a very high degree.

FLIGHT and AIRCRAFT ENGINEER, No.1971, Vol. 1, Thursday, 3 October 1946, at page 364

De Havilland DH.108 TG/306. (Unattributed)
De Havilland DH.108 TG306. (Unattributed)

The DH.108 was a single-seat, single-engine jet fighter prototype with swept wings and no conventional tail. It was similar in configuration to the Messerschmitt Me-163 rocket-powered interceptor. The first two prototypes, TG283 and TG306, were built using production English Electric DH.106 Vampire F.I fuselages. TG283 had a 43° sweep to the wings’ leading edge, while TG306 had a 45° sweep. The airplane was powered by a de Havilland Goblin 3 centrifugal-flow turbojet engine (a development of the Halford H.1) which produced 3,350 pounds of thrust (14.90 kilonewtons).

The first and third DH.108s also crashed. VW120 was destroyed on 15 February 1950 when it crashed after a dive. The left wing had separated and the pilot, Squadron Leader Stuart Muller-Rowland, also suffered a broken neck as a result of the airplane’s violent oscillations. On 1 May 1950, while conducting low-speed tests, TG283 went into an inverted spin. Squadron Leader George E.C. Genders, AFC, DFM, bailed out but his parachute did not open before he hit the ground and he was killed.

Geoffrey de Havilland, Jr., exits the cockpit of one of the company's jet aircraft. (Photograph Courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)
Geoffrey de Havilland, Jr., OBE, exits the cockpit of a DH.108 Swallow prototype. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

© 2018, Bryan R. Swopes