The Lockheed L-188 Electra is an American turboprop airliner built by Lockheed. It was the first turboprop airliner produced in the United States. It first flew in 1957, and when first delivered had performance only slightly inferior to that of a turbojet airliner while at a lower operating cost.
Design and development
The design of the Electra was started by Lockheed in 1954, and the following year the company received a launch order from American Airlines. The prototype first flew on December 6, 1957. The aircraft is a low-wing monoplane with retractable tricycle landing gear, powered by four Allison 501D turboprops. Standard accommodation was for 66 to 88 passengers, with an optional high-density layout for 98 passengers. The initial production version was the L-188A. Later a longer-range L-188C was produced. A total of 170 aircraft were built, with production stopped earlier than planned due to the lack of confidence in the design after two fatal crashes. The aircraft were modified following the accidents but by then customers were interested in operating turbojets. Most of the aircraft currently in service are operated as freighters. In 1957 the United States Navy issued a requirement for an advanced patrol aircraft. Lockheed proposed a development of the Electra which was later placed into production as the P-3 Orion.
American Airlines was the launch customer, followed by Eastern Airlines and Braniff Airways. Many airlines in the US flew Electras, but the only European airline to order the type was KLM. In the South Pacific, TEAL and Air New Zealand flew the Electra. In Australia TAA and Ansett operated Electras on routes between Melbourne, Sydney and Brisbane, and to Port Moresby from 1959 until 1971. Qantas also operated four Electras, VH-ECA,B,C & D at about the same time across the Tasman. The Electras flew in commercial service until the mid-1970s. Some units were sold to Brazilian airline Varig, operated with a perfect safety record until 1992 on the Rio de Janeiro-São Paulo (that route is called Ponte Aérea - air bridge, in Portuguese) shuttle service before being sold to Zaire. Others were retired into air cargo use. A total of 144 L-188s were built, 57 of which have been destroyed in accidents, according to the Aviation Safety Network. The most recent Electra accident was in July 2003.
In 1983, after the retirement of their last SP-2H Neptunes the Argentine Navy modified several civilian Electras for maritime patrol , and widely used them until their replacement by P-3s in 1994. One of the Argentine Navy's Electras, known locally as L-188W Electron for electronic warfare, is preserved at the Argentine Naval Aviation Museum (MUAN) at Bahia Blanca.
Electra operators today
Accidents and incidents
These two accidents mirrored each other and shocked the aviation industry. The FAA Administrator requested Lockheed Aircraft Corporation to reevaluate the Electra. NASA and Lockheed engineers eventually determined that the engine mounts---following the failure of an engine mount during a hard landing---allowed too much precessional movement of the propellers at a critical frequency which allowed "whirl-mode" aeroelastic phenomenon, "flutter" in flight. This flutter, by pure chance, occurred at the wings' natural resonance frequency, which further excited the harmonic oscillations, which increased the wing flutter, that eventually led to separation of a wing from the fuselage. The engine mounts were redesigned and the wing stiffened so the problem was solved by 1961.
Published in July 2009.
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