Why did the three-engine version of the Boeing 747 fail?


Why did the three-engine version of the Boeing 747 fail?

Boeing 747

The Boeing 747 needs no introduction. This is one of the most successful aircraft in the history of — February 2019 marked the 50th anniversary of its first test flight. Since then, Boeing has released several different modifications of the giant, and almost 1 600 copies have been delivered in total.

The last model of this type was the 747-8 and its cargo twin, the 747-8F. In a three-class configuration, Korean Air aircraft can accommodate 368 passengers — 6 in First, 48 in business and 314 in economy class. Lufthansa took to the skies in June 2012 and its 747–8 four-class configuration seats 364 — 8 in First Class, 80 in Business, 32 in Premium Economy and 244 in Economy.

Boeing 747–8 — the longest airliner in the world, it “overtakes” The Airbus A340-600 is only 1.5m away.

Boeing is currently working on two new Air Force One B747 aircraft for the US government. Initially, their delivery was planned for 2024, but judging by the manufacturer's information, they will be ready at the earliest by 2026. The last commercial aircraft of the — cargo 747-8F — was handed over to Atlas Air last October.

Why did the three-engine version of the Boeing 747 fail?

Three-engine variant

All the Boeing 747s we've seen have four engines. Largely due to their voracity, they lost the competition to younger and more economical twin-engine competitors. However, in the 1960s and 1970s, Boeing considered building a three-engine variant of the Sky Queen, with one engine on each wing and an additional tail-mounted engine. The narrow-body Boeing 727 was made in a similar design.

The three-engined Boeing 747 was significantly shorter than the base 747. It was designed to compete with the modern wide-body airliners Lockheed L1011 and McDonnell Douglas DC-10. At the same time, Boeing had a greater passenger capacity, greater payload and flight range than both potential competitors.

Why did the three-engine version of the Boeing 747 fail?


Why did the project fail?

The idea with the new liner turned out to be unsuccessful mainly for two reasons.

Reason #1. To make the three-engined 747 structurally sound, the aircraft needed a completely different wing design, because the existing one was designed for two engines on each side. In the end, Boeing decided to abandon the development of the new wing.

Reason #2. Pilot training. Boeing sought to create a product that would be identical in terms of piloting to the regular 747. To minimize the retraining of pilots for the transition to the three-engine version, Boeing sought to maintain the existing handling characteristics. And it turned out to be an impossible task with two main engines on the wings and a third installed in the tail.

What happened to the three-engine Boeing 747?

In fact, Boeing did not completely abandon the three-engine configuration of the 747, settling on a shorter version with the usual four engines. It was named 747SP — Special Performance Boeing built a total of 45 747SP aircraft. And the first of them entered the Pan Am fleet in 1976. It is said that four of these aircraft are still in operation.

Perhaps the most interesting 747SP still in service is known as SOFIA, which stands for Stratospheric Observatory For Infrared Astronomy — “The Stratospheric Observatory for Infrared Astronomy”. There is a huge door at the back of the fuselage that hides a flying telescope. Built in 1977, this aircraft was previously operated by Pan Am and United Airlines before being acquired by NASA in 1997.

Ultimately, the three-engine version of the Boeing 747 proved to be an outsider in competition with the Lockheed L1011 and McDonnell Douglas DC10. Moreover, by the end of the 20th century, McDonnell Douglas released a second-generation airliner — MD-11 with three engines.

The commercial debut of the MD-11 took place at Finnair in December 1990 and withstood fierce competition from the Boeing 777 and Airbus A340. Its basic configuration was similar to that of the older DC-10; however, it benefited from updated engines. The MD-11 also boasted a longer fuselage and wider wings than its predecessor. 

However, McDonnell Douglas managed to build only 200 of these machines, with many orders left unfulfilled. This type now serves only cargo airlines. It turns out that Boeing, having abandoned the production of the three-engine 747, avoided the fate of the MD-11 as a passenger airliner, focusing its efforts on more promising and successful projects.

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