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The HU-16 Albatross was a large twin-radial engine amphibious flying boat that first flew in 1947. Originally designated SA-16, it was renamed HU-16 in 1962 and a total of 466 machines were built.
The Albatross was designed to be able to land at sea in open ocean situations in order to effect the rescue of downed pilots. Its deep-V cross-section and substantial length helped make it possible for it to land in wavy conditions.
Power comes from two nine cylinder two-speed supercharged Wright R-1820-76 radial engines of 1450 horsepower each. Versions of the same engine are used on the T-28 and the B-17. Each engine drives a three-bladed constant speed propeller. Unlike most constant speed propellers, these propellers are electrically controlled and hydraulically actuated independent of engine oil. The governor RPM is set by toggle switches, and the governor and prop hydraulic pump are driven by the engine. A prop oil cooler is integrated into the hub dome. The propeller uses a lighter weight oil than the engine. This system allows immediate control of the propellers on engine start without waiting for the engine oil to warm up. On the water at low speeds, the air rudder is not effective, and no water rudder is installed. The primary means of directional control is differential power. At idle power settings, control is best accomplished by moving one prop in and out of reverse. No beta range was available on these propellers. When the engine is running, the propeller is thrusting one way or the other, so immediate control is necessary.
Primary fuel is carried in main wing tanks. Additional fuel can be carried in the tip floats. However, water operations are prohibited with more than 100 gallons of fuel in each tip floats. Otherwise the tip floats wouldn't. Runway landings are also prohibited with more than a 100 gallon difference in fuel load between the tip floats. This aircraft is equipped with wing racks capable of carrying bombs or drop tanks. With main, tip, and drop tanks, this aircraft can carry a total of 10,200 pounds (1700 gallons) of fuel, for a reported range of 3000 miles. This aircraft has flown non-stop from Nome AK to Japan in 16.5 hours.
Landing gear was installed for land operations. The main gear retracted into the side of the fuselage, and the main gear strut folded into the side of the fuselage and underside of the wing. During water operations, the main gear well is flooded with approximately 1000 pounds of water. During the takeoff run, the acceleration forces this water through a hole in the rear bulkhead, through a tube which exits near the center of the hull in the low pressure area immediately behind the step. A smaller hole near the bottom of the bulkhead lets out the remaining water.
The nose gear lowers through doors in the center of the forward part of the hull. Damage to these doors can occur if the aircraft if landed on the water in a too nose-low attitude. True to Navy tradition, the nose gear has two wheels. I suspect this was more to save space in the lower fuselage by using smaller wheels than for straddling a catapult track. The nose gear is free castering with no nose wheel steering provided. Directional control during land taxi is provided by differential thrust, augmented by differential brakes. A less than desirable note about the brake system was that every application of the brakes required pumping the pedals several times. This increased the difficulty of taxiing. The requirement to pump the brakes was verified by the owner as "normal" for this aircraft.
The nose gear compartment is sealed from the hull, and is partially flooded during water operations. A small window in the top of the compartment is visible from the flight deck, giving a quick check if the nose gear is up or down (doors open or closed), at least for daytime operations.
Tip floats are provided for lateral stability in water operations. The underside of the fuselage is assembled with round head rivets, while the remainder of the aircraft is flush riveted. The Albatross was originally designed and built with flush rivets on the underside. After an operational accident, a large hole in the underside of an Albatross was repaired in the field, but the mechanic only had round headed rivets available. Much to their surprise, the water takeoff performance improved, getting off the water 5 to 10 knots sooner. Word was sent back to Grumman, who verified this with testing. Therefore, all subsequent Albatrosses were completed with round headed rivets on the hull bottoms. In an odd twist to the story, because the sheets were already dimpled/countersunk, they used a special rivet which was essentially a flat head rivet, but with a round head added on top of it. Countersunk round head rivets-only on the Grumman flying boats...
The flight control system is fully reversible (cables, pulleys, pushrods), with hydraulic boost available for the rudder. Hydraulic rudder boost is normally only used during takeoff and landing, and is mostly intended to relieve pedal forces during single engine flight. Rudder boost is not required for normal flight.
Electric trim is provided for all axes, driving trim tabs on the elevators, rudder, and left aileron. A fixed tab is provided on the right aileron. Each elevator has a trim tab, and each elevator trim tab is controlled and driven independently, providing redundancy. Trim is controlled by toggle switches on the panel between the pilots. A coolie hat switch was added to the yoke. Fore and aft movement controls the left elevator tab. Side to side movement controls the rudder trim, not aileron trim. This was judged as more useful during normal operation, allowing easy trimming for p-factor, torque, and single engine flight.
The flaps are electrically controlled and hydraulically operated. The flaps are also hydraulically balanced, a feature unique to Grumman aircraft. In the absence of air loads, lowering the flap lever lowers the flaps, which may come down asymmetrically. However, as soon as air loads are applied, a cross-feed between the actuators will allow the flaps to re-adjust until the loads, and thus position, are symmetric.
The lion's share of Albatrosses were used by the U.S. Air Force, primarily by the Air Rescue Service. The USAF utilized the SA-16 extensively in Korea, where it gained a reputation as a rugged and seaworthy craft. Later, the HU-16B (long-wing variant) Albatross was used by the U.S. Air Force's Aerospace Rescue and Recovery Service in the Vietnam conflict. The HU-16D Albatross was used for United States Navy Search And Rescue and "skunk runs" on Guam during the Vietnam War at NAS Agana. Goodwill flights were also common to the surrounding Trust Territory of the Pacific Islands in the early 1970s. Open water landing and takeoff training using JATO was conducted frequently at Apra Harbor, Guam. The aircraft was also operated by the United States Coast Guard for many years.
In 1970, Conroy Aircraft marketed a remanufactured HU-16A with Rolls-Royce Dart turboprop engines as the Conroy Turbo Albatross, but only the single prototype (registration N16CA) was ever built.
Argentina, Brazil, Canada, Chile, Republic of China, Colombia, Germany, Greece, Iceland, Indonesia, Italy, Japan, Malaysia, Mexico, Norway, Pakistan, Peru, Philippine Air Force, Portugal, Spain, Thailand (Royal Thai Navy), United States: US Air Force, US Navy, Coast Guards, Venezuela.
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