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30th of August 1913 and 1985

Today a double feature in our history blog! 1913

US Navy pilot Lt. Patrick Ballenger pilots a US Navy flying boat on this day in aviation history and becomes the first pilot to successfully hand over control of the aircraft in flight to the gyroscopic automatic stabilizing device on his flying boat. You could say the very first Sperry autopilot. Invented by Lawrence B. Sperry. L.W. Sperry in 1928

Besides inventing the autopilot Lawrence Sperry is also credited with inventing the artificial horizon.


72 years after the first flight of an aircraft controlled by a form of autopilot the Bell D-292 ACAP (Advanced Composite Airframe Program) helicopter took flight for the first time.

The Bell D-292 ACAP on its maiden flight

The Bell D-292 was an all-composite

helicopter built by Bell Helicopters Textron under a contract from the US Army as part of the Light Helicopter Experimental program. The aircraft was powered by 2 Avco Lycoming LTS 101-750C-1turboshaft engines, producing 684 hp each. A lot of parts were common to the Bell 222, a short overview:

  • Engines

  • Transmission LTS 101-750C Engine

  • Main rotor

  • Tail rotor

  • Tail boom

  • Vertical fin

  • Rotor pylon

Three airframes were built for different test purposes;

  1. Tool proofing

  2. Static testing

  3. Flight testing

The use of a composite airframe gave a 22% saving in aircraft weight (with a comparable helicopter) and a 17% saving in cost. The initial test program consisted of 15 hours of ground testing and 50 hours of flight testing, After this initial testing, a military test phase started which was completed in 1988. This military testing consisted of a large number of tests, among others:

  • Landing Gear crash absorption tests (including dropping the aircraft from 42 feet (~13 meters) and a 50 m/s {97 knots} impact with 10 degrees pitch and 10 degrees roll. All without serious "Injury" to the occupants (crash test dummies)

  • Lightning protection tests

  • Repairability test

  • Interior acoustics testing

Another experiment that the Bell D-292 was used for was the 1986 research by Boeing and US Air Force into the protection of the electric equipment against lightning strikes. With the aid of a 200.000 Ampere / 1.600.000 volt lightning generator, several tests were carried out.

A Bell D-292 airframe during the Boeing & US Air Force static lightning strike tests

Specifications for the Bel D-292 General characteristics

  • Crew: four

  • Length: 40 ft 5 in (12.32 m)

  • Height: 11 ft 2 in (3.40 m)

  • Empty weight: 5,765 lb (2,615 kg)

  • Max takeoff weight: 7,485 lb (3,395 kg)

  • Powerplant: 2 × Avco Lycoming LTS 101-750C-1 turboshaft, 684 hp (510 kW) each

  • Main rotor diameter: 42 ft 0 in (12.80 m)

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