The Aero Commander 500 family is a series of light-twin piston-engined and turboprop aircraft originally built by the Aero Design and Engineering Company in the late 1940s, renamed the Aero Commander company in 1950, and later a division of Rockwell International in 1965. Final production occurred under the Gulfstream Aerospace name. The initial production version was the 200 mph (320 km/h; 170 kn), seven-seat Aero Commander 520. An improved version, the 500S, manufactured after 1967, is known as the Shrike Commander. Larger variants are known by numerous model names and designations, ranging up to the 330 mph (530 km/h; 290 kn), 11-seat Model 695B/Jetprop 1000B turboprop.[1]
As of recent, the Aerocommander is know as the Twin Commander.
Design and development
The first model, the five-seat 520, was certified in January 1952 with two 260 HP Lycoming GO-435s
The idea for the Commander light business twin was conceived by Ted Smith, a project engineer at the Douglas Aircraft Company.[2] Working part-time after hours throughout 1944, a group of A-20 engineers formed the Aero Design and Engineering Company to design and build the proposed aircraft with a layout similar to their A-20 bomber.[2][3] Originally, the new company was going to build three pre-production aircraft, but as the first aircraft was being built, they decided to build just one prototype.[2] The final configuration was completed in July 1946 and was designated the Model L3805.[2]
RegisteredNX1946, the prototype first flew on 23 April 1948.[2] The L3805 accommodated up to five people and was powered by two Lycoming O-435-A piston engines.,[1] it was an all-metal high-wing monoplane with retractable undercarriage using components from a Vultee BT-13 Valiant. The market segment planned for this aircraft to be sold to small feeder airliner firms and was originally designed to carry seven passengers, but instead found use in the private business aircraft and military market.[4]Walter Beech test flew the aircraft in 1949 and expressed interest in buying the project, but passed on it, to instead develop the Beechcraft Twin Bonanza. Fairchild Aircraft also evaluated the prototype at its Hagerstown, Maryland, headquarters.[3]
The prototype flew successfully and the company leased, at no cost, a new 26,000 square feet (2,400 m2) factory at Bethany near Oklahoma City to build a production version, certified on 30 June 1950. Nearly 10,000 hours of redesign work went into the model, including more powerful Lycoming GO-435-C2 engines, with a combined rating of 520 horsepower (390 kW). The production model was named the Commander 520. The first Commander 520 was rolled out of the new factory in August 1951. Serial number 1 was used as a demonstrator, then sold in October 1952 to the Asahi Shimbun Press Company of Tokyo.[citation needed]
In military service it was initially designated the L-26, though in 1962 this was changed to U-4 for the United States Air Force and U-9 for the United States Army.
According to the July 1, 1968 Frontier Airlines (1950-1986) system timetable, series 500 aircraft were being operated on scheduled passenger flights by Combs Aviation on behalf of Frontier via a contract agreement with service to several smaller communities in Montana and Wyoming at this time.[10][11]
The unpressurized, long-fuselage 680FL was operated as a small package freighter by Combs Freightair in the 1970s and 1980s, and by Suburban Air Freight in the 1980s and 1990s. The aircraft was popular with pilots, because it was extremely "pilot friendly" and with its 380 hp (280 kW) supercharged engines did well in icing meteorological conditions. A number are still operated on contracts for cargo and fire control applications, as their piston engines offer good fuel specifics at low altitudes and longer loiter times.
Wing spar fatigue
Beginning in June 1991, senior engineers met with FAA officials to discuss concerns over the Aero Commander's main wing spar, which was believed to be susceptible to stress fatigue and subsequent cracking, and was believed to have resulted in a number of fatal crashes.[12] From approximately 1961 to 1993, 24 aircraft crashed when spar failures caused the loss of the wing in flight.[12] 35 more spars were found cracked during inspections.[12]
Single-engine safety
In 1950, when the developers were working to satisfy Civil Aeronautics Authority (CAA) regulations for certification of the 500, they chose a novel method of demonstrating its single-engine safety and performance: they removed one of the two-bladed propellers, secured it in the aft cabin, and flew from Bethany to Washington, D.C., on one engine. There they met with CAA personnel, then replaced the propeller and returned to Oklahoma in the conventional manner. The flight received nationwide coverage in the press.[13][14]
In 1979, the National Transportation Safety Board reviewed light-twin engine-failure accidents, involving the 24 most popular model-groups of light twins between 1972 and 1976. They found that the piston-engined twin-Commanders had averaged slightly over 3.4 engine-failure accidents per hundred-thousand hours, the second worst number of all aircraft under review.[15][16] The most engine failures were suffered by the small-engine versions of the Piper Apache, at 6.9 failures per hundred thousand hours; the third-worst, the Beechcraft Travel Air, averaged 2.9 failures; the average for all models was only 1.6.[15][16]
Countering the statistical evidence, Rockwell demonstration pilot Bob Hoover's famous airshow stunt routine, with the Shrike Commander, included a full aerobatic routine performed first with both engines, then with one engine out (and the critical engine, at that), then both engines out, and gliding. Then in his final airshow performance, in a supreme demonstration of conservation of momentum, he did all that, then landed the Shrike Commander dead stick (engines off), coasted the airplane down the runway then from the runway down the taxiway and silently let the craft roll slowly to a full stop right in front of the crowd.[17][18][19]
The turboprop twin-Commanders—with much more powerful engines (and most with longer bodies, allowing greater rudder leverage, critical for single-engine control[14][20]) – came out on the opposite end of the rankings, with one of the lowest rates of engine-failure accidents of all "light" twins examined, at only 0.4 per hundred-thousand hours.[15]
Variants
Certified from 1954, the seven-seat 560 is powered by two 270–295 hp (201–220 kW) Lycoming GO-480s.
From 1955, the 680 has Supercharged 340–380 hp (250–280 kW) Lycoming GSO-480s.
more powerful 520 with increased weight and swept tail, revised wing, landing gear, fuselage, vertical tail, and primary control system
560A
1955-07-01
6A1
2× GO-480-D/C/G
2× 275
6000
7
156
560 with longer fuselage, revised engine installation, wing, landing gear, fuel and oil systems
560E
1957-02-21
6A1
2× GO-480-C/G
2× 295
6500
7
223
93
560A with Larger wings and greater payload[a], revised engine installation, wing, wheel and brake installation, fuel system with outboard tanks, and landing gear location
World War II hero and actor Audie Murphy died in an Aero Commander 680 crash while flying as a passenger on 28 May 1971. The aircraft was flying in bad weather at night and was on approach to Roanoke, Virginia when it flew into the side of Brush Mountain outside Blacksburg, Virginia, West of Roanoke. Four others and the pilot were also killed.[64]
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