MIAMI – Today in Aviation, the MD-11 airliner and the Latécoère 521 flying boat performed their maiden flights in 1990 and 1935, respectively.
As of July 2019, the MD-11’s global fleet totaled 118 aircraft in commercial service with major cargo operators and other operators with fewer aircraft. On its part, the French Latécoère 521 (Laté 521) flying boat set several world records involving payload and endurance.
The MD-11 aircraft was developed by McDonnell Douglas (MDD) and later by Boeing. The program was introduced on December 30, 1986, following DC-10 implementation studies. As such, the MD-11 is basically a stretched DC-10.
On December 30, 1986, the company launched the MD-11 with commitments for 52 firm orders and 40 options in three different versions (passenger, combi and freighter) from ten airlines and two leasing companies. The first prototype assembly started on March 9, 1988, and the type was rolled out in September 1989.
FAA certification for the MD-11 was obtained on November 8, with Finnair (AY) receiving the first delivery of the type on December 7. The aircraft entered service on December 20. On January 10, 1990, the first MD-11 performed its inaugural flight.
The MD-11 Design
The MD-11 is a medium to long-range widebody airliner with two engines at the base of the vertical stabilizer mounted on the underwing pylons and a third engine at the base. It is based on the DC-10, but has a stretched fuselage, expanded wingspan with winglets, refined wing and tailplane airfoils, new engines and increased composite use.
The winglets are credited with improving approximately 2.5% fuel efficiency. The MD-11 has a lower empennage than the DC-10 on which it is based. The aircraft also had modified GE CF6-80C2 or PW4000 turbofans.
Although the MD-11 program was launched in 1986, MDD had started to search for a DC-10 derivative as early as 1976. Two versions were considered then: a DC-10-10 with a fuselage stretch of 40 feet (12 m) and a DC-10-30 stretched by 30 feet (9.1 m).
The type has a glass cockpit included, removing the need for a flight engineer. The type failed to reach its targets for range and fuel burn.
After Boeing merged with MDC in 1997, the last of the 200 aircraft was completed in October 2000. While some were initially built as freighters, many have also been converted and are in service for cargo airlines.
The Latécoère 521
The Latécoère 521 was a French six-engined double deck flying boat designed and built by Pierre-Georges Latécoère. At the time of its completion, it was the largest aircraft to be constructed in France and one of the first large passenger aircraft to be able to fly trans-Atlantic routes.
On January 10, 1935, the first Laté 521 performed the type’s inaugural flight. A widely publicized demonstration flight had been performed in December 1935, following a series of test flights, flying via Dakar to Natal, Brazil, before turning north towards the French West Indies.
This long-haul flight was planned to purposely coincide with the 300th year of French rule in the Americas. However, disaster struck when the aircraft was trapped in a hurricane and wrecked shortly after having safely reached Pensacola, Florida.
Passenger operations for the Laté 521 began with Air France (AF), which was able to launch many previously unattainable long-distance passenger routes. As a civilian aircraft, the type was configured as a luxury airliner, providing up to 72 passengers with a high level of comfort.
Typical trans-Atlantic services, however, usually carried only about 26 passengers, all of whom would be on the lower deck. On the shorter trans-Mediterranean routes for which the concept had originally been designed to serve, larger passenger supplements could be carried.
Latécoère 521 Design
A wide sesquiplane, the designated Laté 520, build consisted of a central double-decked hull and a pair of stub wings, somewhat resembling the smaller Latécoère 300. It was the largest aircraft to be produced by the French industry at the time, weighing roughly 37 tonnes when loaded and 17 tonnes empty.
It provided a maximum range between refuelling stops of 2,800 miles. The four inboard water-cooled engines, which were built as tandem push-pull pairs and were designed to produce up to 1,000 hp, made it possible for the aircraft to reach a maximum design speed of 160 mph.
The Laté 520 had a wide double-decked hull that provided 80 passengers with space. It had an all-metal structure, consisting mostly of duralumin. A longitudinal building technique was used for the hull, dissipating tension through its transverse frames from the skin. The hull was divided into seven water-tight compartments as a measure to mitigate against potential damage.
A center section and two fabric-covered outer parts were used in the wing of the Laté 520, which were braced to the stub wings. This wing used a conventional two-spar design, made of duralumin for both the box spars and ribs. A combination of duralumin tubular tie rods and round high-tensile steel tubing was internally braced into the wing structure.
The initial design of the 520 series was powered by 4 × 1,000 hp (750 kW) Hispano-Suiza 18Sbr W-18 engines in tandem pairs.
The Laté 521 Lieutenant de Vaisseau Paris was the first completed aircraft, powered by 6 × Hispano-Suiza 12Ydrs. Operated by AF on route proving flights ,the 521 was militarized in 1939 and operated by the Vichy government until stored at Marignane, finally being destroyed when Axis troops retreated from advancing Allies.
Featured images: Finnair MD-11 landing to Helsinki-Vantaa airport and the Latécoère 521. Photos: Wiki Common. Article sources: Boeing, Popular Mechanics, Popular Science.