The Lockheed 188A Electra first flew on 06 December 1957. The transport, a four-engine turboprop airliner of short-to-medium range with a maximum capacity of 99 passengers, received its type certificate on 22 August 1958, and entered scheduled airline service with Eastern Air Lines on 12 January 1959.
In August 1957, the US Navy called for design proposals for a new advanced aircraft for maritime patrol and antisubmarine warfare (ASW) to replace the aging P-2 Neptune. The Navy strongly suggested that a variant of an existing aircraft or one in the advanced design stage be used to save cost and permit rapid introduction into fleet service. Accordingly, Lockheed proposed a military version of the Electra. Development of the Electra to provide the Navy with replacements for its land-based Lockheed P2V Neptunes and Martin P5M Marlins was initiated in 1957, before the first flight of the turboprop-powered airliner. With its design meeting fully the requirements of the Navy, Lockheed easily won the design competition.
In April 1958, the Navy announced that the Electra derivative had won the competition. Lockheed was awarded an initial research and development contract in May 1958, and first flew the Orion's aerodynamic prototype on 19 August 1958. Known initially as the P-3V, the aircraft was redesignated in 1962 as the P-3 Orion. The Orion retained the wings, tail unit, basic fuselage structure, power plant, and many subsystems of the Electra, although its fuselage was about 7 ft. shorter than the Electra's.
In the fall of 1958, Lockheed began deliveries of a new four-engine turboprop Model L.188 civil transport to US airlines. The sleek airliner, known as the Electra, set a new pace for luxury and speed for propeller transports. Over 170 Electras were built by Lockheed and delivered to US and South American airlines.
Soon after introduction to the civil transport fleet, the Electra suffered two widely publicized fatal accidents with suspicious wreckage that raised concern over the structural integrity of the aircraft. On September 29, 1959, a Braniff Electra cruising near Buffalo, Texas, disintegrated without survivors. Investigation of the dispersal of aircraft wreckage revealed that the left wing had failed and separated from the aircraft in flight. The Electra exploded in flight, with the loss of all 34 persons aboard.
On 17 March 1960 another Lockheed Electra lost a wing in turbulent air and crashed near the towns of Tell City and Cannelton, Ind., with startling similarity to the Texas accident. Its right wing was found over 11,000 ft from the crash site, which indicated that it had also been torn from the aircraft. All 63 persons aboard the Northwest Airlines flight were killed. On 20 March 1960, FAA reduced the top cruising speed of the Electra Model 188 series turboprop airliners from 373 to 316 m.p.h., pending determination of the cause. Additional restrictions effective on 25 March included a further cutback in permissible speed (down to 259 m.p.h., or 225 knots) and a series of rigid tests and inspections. These measures seemed warranted by similarities between the Tell City crash and the crash of another Electra in Texas.
Over 130 Electras were operating in the civil fleet at the time, and authorities immediately reduced the cruise speed of the airliners while the investigation attempted to identify the cause of the fatal crashes. On April 12, the Civil Aeronautics Board unanimously recommended grounding all Electras not inspected since the Tell City accident. FAA Administrator Quesada decided, however, that the aircraft could safely continue to operate under the 25 March restrictions. On May 12, Lockheed announced its conclusion that the two aircraft destroyed in the accidents had sustained prior damage. This had permitted their power-package nacelles to wobble, allowing development of a "whirl-mode" phenomenon that overstressed their wings.
Working under great pressure (about 130 Electras were in service at the time), a NASA and industry team conducted wind tunnel tests along with analytical calculations. Lockheed and NASA Langley experts were concerned that the propeller driven Electra may have exhibited the phenomenon known as propeller-whirl flutter, in which the stiffness of the engine mounts interacts with the gyroscopic torques produced by the engine and propeller combination. This interaction results in an unstable wobbling motion that could resonate with natural frequencies of the wing structure and could cause cata-strophic flutter of the wing. The wobbling motion coupled with the natural flutter frequency of the wings. The fatal resonance could build up and tear the aircraft apart in 30 seconds. Based on these results, the engine mounts on all Electra aircraft were strengthened.
On 04 October 1960 an Eastern Air Lines Electra plunged into Boston Harbor shortly after taking off from Logan Airport, killing all but 10 of the 72 persons aboard. The accident marked the fifth Electra crash in two years and touched off renewed demands to ground the aircraft, which was being allowed to operate by FAA under a reduced speed regime. The presence of many dead birds on the Logan runway helped to convince FAA Administator E. R. Quesada that the accident had probably been caused by ingestion of birds into the aircraft's engines rather than structural failure. Quesada decided not to ground the Electra. This judgement was later supported by laboratory tests that pointed conclusively to bird ingestion. Following the Boston crash, FAA engaged in studies and research on the bird hazard and methods of protecting aircraft from the effects of bird strikes.
The FAA lifted the speed restriction on Lockheed Electras on 31 December 1960 when modification to prevent recurrence of the nacelle-wing whirl mode phenomenon had been accomplished. The agency informed all known operators of the Electra by telegram and published the airworthiness directive in the Federal Register on 17 January 1961. The Electra and its derivative P-3 aircraft have since operated safely.
Quickly rendered obsolete in the eyes of travelers by the introduction of pure-jet transports, the Electra remained in production for only four years and was rapidly withdrawn from use by most major carriers. Fortunately for Lockheed, the Electra's technical difficulties were easily resolved and, unlike airliners, the US Navy and several foreign air forces found considerable merits in turboprops, as the ASW and maritime patrol missions for which the Orion was derived from the Electra favored long loitering capabilities over higher cruise speed.
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