Lockheed L-188 Electra

https://en.wikipedia.org/wiki/Lockheed_L-188_Electra

The Lockheed L-188 Electra is an American turboprop airliner built by Lockheed.
First flown in 1957, it was the first large turboprop airliner built in the
United States. Initial sales were good, but after two fatal crashes that led to
expensive modifications to fix a design defect, no more were ordered. With its
unique high power-to-weight ratio, huge propellers and very short wings
(resulting in the majority of the wingspan being enveloped in propwash), large
Fowler flaps which significantly increased effective wing area when extended,
and four-engined design, the airplane had airfield performance capabilities
unmatched by many jet transport aircraft even today—particularly on short
runways and high field elevations. Jet airliners soon supplanted turboprops for
many purposes, and many Electras were modified as freighters. Some Electras are
still being used in various roles into the 21st century. The airframe was also
used as the basis for the much more successful Lockheed P-3 Orion maritime
patrol aircraft.

The Model 188 Electra is a low-wing cantilever monoplane powered by four
wing-mounted Allison 501-D13 turboprops. It has a retractable tricycle landing
gear and a conventional tail. It has a cockpit crew of three and can carry 66 to
80 passengers in a mixed-class arrangement, although 98 could be carried in a
high-density layout. The first variant was the Model 188A, followed by the
longer-range 188C with room for 1,000 US gallons (3,800 L) more fuel and maximum
take-off weight 3,000 pounds (1,400 kg) higher.


Role
Turboprop airliner

National origin
United States

Manufacturer
Lockheed Corporation

First flight
December 6, 1957

Introduction
January 12, 1959 with Eastern Air Lines

Status
In limited use

Primary users
American Airlines
Eastern Air Lines
Braniff Airways
National Airlines

Produced
1957–61

Number built
170

Variants
Lockheed P-3 Orion

American Airlines was the launch customer. Eastern Air Lines, Braniff Airways
and Northwest Airlines followed. The Electra suffered a troubled start.
Passengers of early aircraft complained of noise in the cabin forward of the
wings, caused by propeller resonance. Lockheed redesigned the engine nacelles,
tilting the engines upwards three degrees. The changes were incorporated on the
production line by mid-1959 or as modification kits for the aircraft already
built, and resulted in improved performance and a better ride for passengers.

Three aircraft were lost in fatal accidents between February 1959 and March
1960. After the third crash, the FAA limited the Electra's speed until the cause
could be determined.

After an extensive investigation, two of the crashes (in September 1959 and
March 1960) were found to be caused by an engine mount problem. The mounts were
not strong enough to damp a phenomenon called "whirl mode flutter" (analogous to
the precession of a child's top as it slows down) that affected the outboard
engine nacelles. When the oscillation was transmitted to the wings and the
flutter frequency decreased to a point where it was resonant with the outer wing
panels (at the same frequency, or harmonically related ones), violent
up-and-down oscillation increased until the wings would tear off. The company
implemented an expensive modification program (the Lockheed Electra Achievement
Program or LEAP) in which the engine mounts and the wing structures supporting
the mounts were strengthened, and some of the wing skins were replaced with
thicker material. All Electras were modified at Lockheed's expense at the
factory, the modifications taking 20 days for each aircraft. The changes were
incorporated in later aircraft as they were built. However, the damage had been
done, and the public lost confidence in the type. This and the smaller jets that
were being introduced eventually relegated Electras to the smallest airlines.
Production ended in 1961 after 170 had been built. Losses to Lockheed have been
estimated as high as $57 million, not counting an additional $55 million in
lawsuits. Electras continued to carry passengers into the 1980s, but most now in
use are freighters.

In 1973, the Argentine Navy bought three Electras equipped with cargo doors.
These were used during the "Dirty War" to toss political prisoners into the Rio
de La Plata in the infamous death flights. The Electras were also used for
transport duties during the Falklands War in 1982.

Specifications (Model 188A)

General characteristics
Crew: Five (3 flight deck)
Capacity: 98 passengers
Payload: 33,800 lb (15331 kg)
Length: 104 ft 6 in (31.85 m)
Wingspan: 99 ft 0 in (30.18 m)
Height: 32 ft 10 in (10.00 m)
Wing area: 1,300 sq ft (120.8 m²)
Empty weight: 57,400 lb (26,036 kg)
Max. takeoff weight: 113,000 lb (51,256 kg)
Powerplant: 4 × Allison 501-D13 turboprop engines, 3,750 eshp (2,800 kW) each

Performance
Maximum speed: 390 knots (448 mph, 721 km/h) at 12,000 ft (3,660 m)
Cruise speed: 324 knots (373 mph, 600 km/h)
Range: 1,913 nmi (2,200 mi, 3,540 km) with maximum payload, 2,409 nmi, 2,770 mi,
4,455 km with 17,500 lb (7,938 kg) payload
Service ceiling: 32,000 ft (9,753 m)
Rate of climb: 1,970 ft/min (10 m/s)






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