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, 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, 11-seat Model 695B/Jetprop 1000B turboprop.[1] As of recent, the Aero Commander is known as the Twin Commander.
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.[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. The final configuration was completed in July 1946 and was designated the Model L3805.
Registered NX1946, the prototype first flew on 23 April 1948. 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.
The prototype flew successfully and the company leased, at no cost, a new 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 . 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.
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.
Under ownership of Rockwell in the 1960s, World War II pilot R. A. "Bob" Hoover demonstrated the Shrike Commander 500S for decades in a variety of "managed energy" routines, including single-engine and engine-out aerobatics.[5] [6] His Shrike Commander is displayed in the colors of his last sponsor, Evergreen International Aviation, at the Steven F. Udvar-Hazy Center of the Smithsonian National Air and Space Museum. Bob Odegaard continued the tradition in 2012, flying a 1975 Shrike 500S in a Bob Hoover tribute routine.[7]
One U-4B became a presidential transport aircraft for Dwight D. Eisenhower between 1956 and 1960. This was the smallest "Air Force One", and the first to wear the now-familiar blue-and-white livery. This aircraft is now owned by the Commemorative Air Force.[8]
As of 2004 Shrike Commanders remained in service with the United States Customs Service, United States Coast Guard, and United States Forest Service.[1]
A single 560F was operated by the Belgian Air Force as the personal transport of the late king Baudouin of Belgium from 1961 to 1973.[9]
According to the July 1, 1968, Frontier Airlines 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 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.
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. From approximately 1961 to 1993, 24 aircraft crashed when spar failures caused the loss of the wing in flight. 35 more spars were found cracked during inspections.
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.[12] [13]
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.[14] [15] 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.
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.[16] [17] [18]
The turboprop twin-Commanders—with much more powerful engines (and most with longer bodies, allowing greater rudder leverage, critical for single-engine control[19]) – 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.
| name | approved | TC | engines | power | MTOW | ceiling | seats | fuel | built | |
| L.3805 | 1 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 520 | 1952-01-31 | 6A1 | 2× GO-435-C2/C2B | 2× 260 | 5500-5700 | 5 | 145 | 150 | ||
| 560 | 1954-05-28 | 6A1 | 2× GO-480-B/B1C | 2× 270 | 6000 | 7 | 145 | 80 | ||
| 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, revised engine installation, wing, wheel and brake installation, fuel system with outboard tanks, and landing gear location | ||||||||||
| 560F | 1961-02-08 | 2A4 | 2× IGO-540-B | 2× 350 | 7500 | 7 | 223 | |||
| 680F with unsupercharged engine and reduced gross weight | ||||||||||
| 360 | 2× 180 | 4 | 1 | |||||||
| Lightened 560E | ||||||||||
| 500 | 1958-07-24 | 6A1 | 2× O-540-A2B | 2× 250 | 6000 | 7 | 156 | 101 | ||
| 560E with decreased gross weight, powerplants, and 560A landing gear | ||||||||||
| 500A | 1960-04-07 | 6A1 | 2× IO-470-M | 2× 260 | 6000 | 7 | 156 | 99 | ||
| 500 with new nacelles, fuel injection engine and new landing gear | ||||||||||
| 500B | 1960-07-13 | 6A1 | 2× IO-540-B/E | 2× 290 | 6750 | 7 | 156 | 217 | ||
| 500A with fuel injection | ||||||||||
| 500U | Shrike Commander | 1964-12-11 | 6A1 | 2× IO-540-E | 2× 290 | 6750 | 7 | 156 | 56 | |
| 500B with pointed nose and squared off tail | ||||||||||
| 500S | Shrike Commander | 1968-03-15 | 6A1 | 2× IO-540-E | 2× 290 | 6750 | 7 | 156 | 316 | |
| 500U with minor changes | ||||||||||
| 680 Super | L-26C → U-4B L-26C → U-9C | 1955-10-14 | 2A4 | 2× GSO-480-A1A6 | 2× 340 | 7000 | 7 | 223 | 254 | |
| supercharged 560A | ||||||||||
| 680E | 1958-06-19 | 2A4 | 2× GSO-480-B1A6 | 2× 340 | 7500 | 7 | 223 | 100 | ||
| 680 with Lightened 560E/560A type undercarriage, extended wing and increased maximum weight | ||||||||||
| 720 | AltiCruiser | 1958-12-05 | 2A4 | 2× GSO-480-B1A6 | 2× 340 | 7500 | 6 | 223 | 13 | |
| Pressurized 680-E, structural modifications to the fuselage, extended wing and increased maximum weight | ||||||||||
| 680F | 1960-08-23 | 2A4 | 2× IGSO-540-B | 2× 380 | 8000 | 7 | 223 | 126 | ||
| 680E with fuel injection engine, new nacelles, new main gear and increased maximum weight | ||||||||||
| 680FP | 2× 380 | 223 | 26 | |||||||
| Pressurized 680F | ||||||||||
| 680FL | Grand Commander | 1963-05-24 | 2A4 | 2× IGSO-540-B | 2× 380 | 7000-8500 | 11 | 223 | 157 | |
| 680F with larger tail, 2 built for the US Army as the RL-26D → RU-9D with, Courser Commander after 1967; stretched | ||||||||||
| 680FL(P) | Grand Commander | 1964-10-08 | 2A4 | 2× IGSO-540-B1A/B1C | 2× 380 | 8500 | 11 | 223 | 37 | |
| pressurized 680FL | ||||||||||
| 680T | Turbo Commander | 1965-09-15 | 2A4 | 2× TPE-331-43 | 2× 575 | 8950 | 25,000 ft | 11 | 286.5 | 56 |
| 680FL/P turboprop | ||||||||||
| 680V | Turbo Commander | 1967-06-13 | 2A4 | 2× TPE-331-43 | 2× 575 | 9400 | 25,000 ft | 11 | 286.5 | 36 |
| 680T with slightly improved cargo capacity | ||||||||||
| 680W | Turbo II Commander | 1968-02-05 | 2A4 | 2× TPE-331-43BL | 2× 575 | 9400 | 25,000 ft | 11 | 286.5 | 46 |
| 680V with pointed nose. squared off fin, one panoramic and two small cabin windows and weather radar | ||||||||||
| 681 | Hawk Commander | 1969-03-20 | 2A4 | 2× TPE-331-43BL | 2× 575 | 9400 | 25,000 ft | 11 | 286.5 | 43 |
| 680W with improved pressurisation, air conditioning system and nose | ||||||||||
| 681B | Turbo Commander | 25,000 ft | 29 | |||||||
| Marketing designation for economy version of the 681 | ||||||||||
| 685 | Commander | 1971-09-17 | 2A4 | 2× GTSIO-520-F/K | 2× 435 | 9000 | 25,000 ft | 9 | 256-322 | 66 |
| 690 powered by piston engines | ||||||||||
| Commander 690 | 1971-07-19 | 2A4 | 2× TPE-331-5 | 2× 717.5 | 10250 | 25,000 ft | 11 | 384 | 79 | |
| 681 with new wing centre section and engines moved further outboard | ||||||||||
| Commander 690A | 1973-04-25 | 2A4 | 2× TPE-331-5 | 2× 717.5 | 10250 | 31,000 ft | 11 | 384 | 245 | |
| 690 with changed flightdeck layout and increased pressurisation | ||||||||||
| Commander 690B | 1976-10-05 | 2A4 | 2× TPE-331-5 | 2× 717.5 | 10325 | 31,000 ft | 10 | 384 | 217 | |
| 690A with improved soundproofing and internal lavatory | ||||||||||
| 690C | Jetprop 840 | 1979-09-07 | 2A4 | 2× TPE-331-5 | 2× 717.5 | 10325 | 31,000 ft | 11 | 384 | 136 |
| 690B with increased wingspan, wet wing fuel tanks and winglets | ||||||||||
| 690D | Jetprop 900 | 1981-12-02 | 2A4 | 2× TPE 331-5 | 2× 748 | 10700 | 31,000 ft | 11 | 425-474 | 42 |
| 690C with internal rear cabin extension, improved pressurisation and five square cabin windows | ||||||||||
| 695 | Jetprop 980 | 1979-11-01 | 2A4 | 2× TPE-331-10 | 2× 733 | 10325 | 31,000 ft | 11 | 425-474 | 84 |
| more powerful 690C | ||||||||||
| 695A | Jetprop 1000 | 1981-04-30 | 2A4 | 2× TPE-331-10 | 2× 820 | 11200 | 35,000 ft | 11 | 474 | 101 |
| 695B | Jetprop 1000B | 1984-02-15 | 2A4 | 2× TPE-331-10 | 2× 820 | 11750 | 35,000 ft | 11 | 474 | 6 |
| 695A with minor changes | ||||||||||
