The introduction of the Boeing 747 in the late 1960s and early 1970s marked the beginning of the widebody market in commercial aviation. Aircraft like the Boeing 747, the McDonnell Douglas DC-10, and the Lockheed L-1011 introduced an unprecedented payload capacity and long-range capability compared to earlier narrowbody jets. These jumbo jet designs allowed airlines to move more passengers and cargo farther and faster. This helped to accelerate international connectivity and transformed the economics of both passenger and air cargo operations.

The competitive widebody industry in the 1980s led to the development of the McDonnell Douglas MD-11, a derivative of the popular DC-10. When the MD-11 entered service in 1990, it featured aerodynamic refinements, modern avionics, more efficient engines, and increased range. Although the MD-11 had a relatively short life in the commercial aviation industry, it remained a major workhorse in the air cargo industry for years to come. Alongside many notable design features, the MD-11 also utilized a unique main landing gear configuration, with 12 tires. Let’s take a closer look at this popular widebody aircraft and its unique main landing gear configuration.

A Brief History Of The McDonnell Douglas MD-11

The development of the MD-11 can be traced back to the mid-1970s. At this point, McDonnell Douglas was seeing success with its popular widebody offering, the DC-10. However, the DC-10 was introduced in 1971 with American Airlines. This meant that the existing commercial fleet was beginning to age out, prompting McDonnell Douglas to develop a derivative widebody aircraft.

However, throughout the late 1970s and the early 1980s, McDonnell Douglas repeatedly halted the program, mostly due to declining sales of the DC-10, which made up the majority of the company’s revenue. However, McDonnell Douglas was able to start the MD-11 program in December 1986. When it was launched, McDonnell Douglas received orders from a significant number of global airlines, including Swissair, British Caledonian, Korean Air, Thai Airways, VARIG, Finnair, and Alitalia. McDonnell Douglas also received several cargo freighter orders, including from FedEx Express.

McDonnell Douglas engineering teams began developing the program at the company’s Long Beach, California, facility. The new widebody aircraft featured a trijet configuration, similar to the McDonnell Douglas DC-10. As the prototype build began to take shape, the engineers intensified aerodynamic testing and systems integration work to ensure the aircraft met the ambitious targets set for it. After several years of refinement and assembly, the first MD-11 rolled out of the factory for the first time in September 1989.

The Introduction Of The McDonnell Douglas MD-11

In January 1990, just a few months after the first MD-11 rolled off the production line, the first MD-11 conducted its maiden flight. The first two aircraft were made in the cargo configuration, for delivery to Fedex Express, and featured a large side cargo door. The Federal Aviation Administration (FAA) granted the aircraft its type certification in November 1980, while the European Joint Aviation Authorities (JAA) type certified the aircraft in October 1991.

The first MD-11 was delivered to Finnair in December 1990. Finnair entered the aircraft into commercial service on December 20, 1990, flying from Helsinki Airport (HEL) in Finland to Tenerife South Airport (TFS) in the Canary Islands, Spain. Delta Air Lines was the first domestic customer of the MD-11, which entered commercial service the following year.

In the coming years, many airlines became dissatisfied with the MD-11, mostly due to poor performance in terms of range and fuel-burn targets. This led to American Airlines and Singapore Airlines canceling both of their orders. American Airlines later sold its fleet to FedEx Express, as the airline realized that the MD-11 was incapable of flying the Dallas-Hong Kong route as it had previously planned. The company attempted to make design changes to improve its range. Even so, many prospective customers instead turned to ordering the Boeing 767, the Boeing 777, or the Airbus A330. Boeing later merged with McDonnell Douglas in 1997, which led to the production of the MD-11 being scaled back to only freighter aircraft. Overall, McDonnell Douglas produced about 200 total aircraft, with production officially ending in 2000.

The Major Operators Of The McDonnell Douglas MD-11

When the MD-11 was introduced in 1990, McDonnell Douglas received orders from a diverse group of customers, many of which were focused on its long-range capability and efficiency improvements compared to the DC-10. The first customer, Finnair, was also one of the most prominent operators of the MD-11. Finnair operated a small fleet of just five MD-11s, although it was used extensively on long-haul routes to Asia and North America. Finnair operated the aircraft for more than twenty years before transitioning to Airbus widebody aircraft.

Elsewhere in Europe, Swissair was another popular operator of the MD-11. Swissair operated a fleet of 16 MD-11s at one point. After it ceased operations in 2002, all the aircraft were transferred to SWISS. KLM was another major European user, ultimately becoming one of the last carriers to fly the MD-11 in passenger service. KLM operated a fleet of 10 MD-11s, the last passenger service flying on October 25, 1914. Overall, some of the most popular commercial operators of the MD-11 include:

Although the MD-11 saw limited commercial success, McDonnell Douglas received significant interest in the aircraft in the cargo industry. Even today, UPS and FedEx Express are the largest operators of the aircraft. According to ch-aviation, in the air cargo industry, FedEx Express operates a total of 58 MD-11s while UPS Airlines operates 26. Additionally, Western Global Airlines operates a small fleet of 14 MD-11s.

The Major Design Features And Performance Specifications Of The McDonnell Douglas MD-11

The MD-11 is considered a medium to long-range widebody airliner. It features three total engines, with the third engine located at the base of the vertical stabilizer. Like many other airliners, the MD-11 utilized two different engine options. This includes the Pratt & Whitney PW4000 and the General Electric CF6 turbofan engines. Each of these three engines provided the aircraft with up to 62,000 pounds of thrust, helping the aircraft achieve the following performance specifications:

As a widebody aircraft, the aircraft featured a large cabin with a high capacity for both passengers and cargo. In a passenger configuration, the aircraft could accommodate up to 323 passengers. However, it typically seats up to 305 passengers in a two-class configuration or up to 270 passengers in a three-class configuration. The freighter variant has over 21,500 cubic feet of space on the main deck, along with the capacity for 32 LD3 cargo containers on the lower deck.

Inside the cockpit, the MD-11 uses six 8-inch CRT display units and advanced Honeywell VIA 2000 computers. The cockpit design is called the Advanced Common Flightdeck (ACF), which is shared with the Boeing 717. It also features an electronic instrument system, a dual flight management system, and GPS.

Why The McDonnell Douglas MD-11 Utilizes So Many Wheels On Its Main Landing Gear

Beyond several upgraded features on the MD-11, one of the aircraft’s most notable features is its large main landing gear, which has 12 wheels total. Overall, the MD-11’s landing gear is a derivative of the DC-10’s landing gear system. However, McDonnell Douglas strengthened and lengthened the gear to support the aircraft’s significantly higher takeoff and landing weights. Each landing gear utilizes three axles with paired tires, while the nose landing gear uses two wheels.

This landing gear configuration allows the aircraft’s weight to be spread across a larger footprint. This allows the MD-11 to operate on runways that may otherwise be unable to handle its high pavement loading. All in all, the biggest factor behind the MD-11’s design was the aircraft’s MTOW, which is over 600,000 pounds. McDonnell Douglas was unable to increase the tire size of the aircraft, as it was limited by the existing gear-bay geometry from the DC-10. Instead of redesigning the entire gear-bay, McDonnell Douglas opted to add more tires. Additional tires helped reduce the load carried by each individual tire, which ensured compliance with tire certification limits and runway pavement stress regulations.

Additionally, the extra tires helped improve the aircraft’s braking performance. More tires meant more brake assemblies, allowing the MD-11 to dissipate heat more effectively during high-energy stops. This redundancy helped to improve safety margins and brake durability. Overall, the MD-11’s landing gear design supports a heavier, longer-range airframe within the structural constraints of the DC-10 platform.

A Closer Look At The Main Landing Gear Of Other Widebody Airliners

Other widebody airliners feature a wide variety of landing gear configurations. One of the most common layouts is the twin main-gear bogie arrangement. Aircraft like the Boeing 767 and the Airbus A330 utilize this configuration, which features two axles and four wheels on each side, for a total of eight main landing gear wheels. These are lighter aircraft, which means they can meet pavement-loading requirements without adding extra axles.

However, on the larger side of the widebody industry, the main landing gear is configured differently. For example, the Boeing 747 uses a unique five-gear system, which includes a nose gear, two wing gears, and two body gears. This amounts to a total of 16 wheels spread across the landing gear assembly.

Furthermore, the larger Airbus A380 uses four main landing gears. The larger aircraft has a higher weight, so Airbus incorporated a total of 20 wheels across the landing gear assembly. Comparing these configurations to the MD-11 highlights the different engineering strategies used across generations of widebodies.