Aero Commander twins
690C Jetprop 1000
Role	Utility and business aircraft Type of aircraft
National origin	United States
Manufacturer	Aero Design and Engineering Company Aero Commander Rockwell-Standard Corporation North American Rockwell Rockwell International Gulfstream Aerospace
First flight	23 April 1948 (Model L3085)
Introduction	October 1952
Status	Active
Produced	1951–1986
Number built	~2,902 (1951 piston-engined, 951 turboprops)

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 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]

Registered NX1946, 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]}

Operational history

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.^{[citation needed]} This was the smallest "Air Force One," and the first to wear the now-familiar blue-and-white livery.^{[citation needed]} 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 State Forestry 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 (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.
• 
  From 1958, the lighter 500 is powered by two 250–290 hp (190–220 kW) Lycoming O-540s or Continental IO-470s.
• 
  From 1963, the stretched 680-FL offered up to eleven seats.
• 
  It gained two 575 hp (429 kW) AiResearch TPE-331 turboprops from the 680-T in 1965.
• 
  From 1971, the heavier 690 has a larger wing and more powerful 717.5–748 hp (535–558 kW) TPE-331s.
• 
  From 1979, the final 695 Jetprop 980/1000 is powered by 733–820 hp (547–611 kW) TPE-331s.

Type certificate data sheet 6A1^[21] and 2A4^[22]

model	name	approved	TC	engines	power	MTOW	ceiling	seats	fuel	built[a]
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[a], 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[a]
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	Aero Commander	1960-04-07	6A1	2× IO-470-M	2× 260	6000		7	156	99
	500 with new nacelles,[a] 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[a]
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[a]
500S	Shrike Commander	1968-03-15	6A1	2× IO-540-E	2× 290	6750		7	156	316
	500U with minor changes[23][page needed]
680 Super	L-26C → U-4B[b] L-26C → U-9C[c]	1955-10-14	2A4	2× GSO-480-A1A6	2× 340	7000		7	223	254
	supercharged 560A [a]
680E		1958-06-19	2A4	2× GSO-480-B1A6	2× 340	7500		7	223	100
	680 with Lightened 560E/560A type undercarriage[a], 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[a]
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 SLAR, Courser Commander after 1967;[a] 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[a]
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[a]
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 [a]
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[a]
681B	Turbo Commander						25,000 ft			29
	Marketing designation for economy version of the 681[a]
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[a]
690	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[a]
690A	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[a]
690B	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[a]
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[a]
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[a]
695	Jetprop 980	1979-11-01	2A4	2× TPE-331-10	2× 733	10325	31,000 ft	11	425-474	84
	more powerful 690C[a]
695A	Jetprop 1000	1981-04-30	2A4	2× TPE-331-10	2× 820	11200	35,000 ft	11	474	101
	more powerful 690D with higher takeoff weight, built for the NOAA[a]
695B	Jetprop 1000B	1984-02-15	2A4	2× TPE-331-10	2× 820	11750	35,000 ft	11	474	6
	695A with minor changes[a]

Operators

Government operators

Military operators

Zdroj:https://en.wikipedia.org?pojem=Aero_Commander_500
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