Chapter 32 Landing Gear

The landing of an aircraft is usually explained as no more than an aircraft crash controlled event.

There are different landing gear designs. The design and location of the landing gear is determined by the characteristics of each aircraft, i.e, geometry, weight.

Weight of the aircraft in addition to the MTOW (Maximum Take Off Weight) and MLW (Maximum Landing Weight) are essential factors in the decision in the design of the landing gear. These factors determine the number and size of tires, the type of wheels and brakes, the shock absorber.

When the aircraft manufacturer is designing the landing gear, they have to obey some industry and federal standards. There have been some landing gear changes when a new series in a model aircraft has been introduced in the market.

The DC 10-10 only had one nose gear and two main gears as the initial configuration. The introduction of the later DC 10 model, the DC 10-30, required the addition of another gear in the configuration of this airplane. The centerline gear maintains this airplane stable on the ground and aids in the balance and proper distribution of the increase of the payload on the Dc 10-30 model. The inclusion of the centerline gear on the DC 10-30 reduced the risk of loading and unloading the wrong way and making it tail heavy. Some accidents happened during the unloading and loading of this aircraft.

Another change in gear design from one model to another was the one done on the Airbus A300/A310 with the introduction of LaGuardia landing gear design. Messier-Dowty the manufacturer of the landing gears for the A300/A310 had to develop a landing gear with bigger print for better weight distribution in order for the New York airport authorities to allow the airplane to land in La Guardia airport.

This page also includes some pictures of the JetBlue 90 degree landing gear incident. I was involved in the inspection and part of the investigation of this landing gear. After the investigation several recommendations and modifications were made to the landing gear. One recommendation adopted was the decrease the number of times the computer check the alignment (lock in place straight attitude) of the nose landing gear. The computer was programmed to check the gear lock down position each second. The computer sent signals to the steering actuator,RVDTs to apply forces to the shock absorber to ensure the shock absorber was still locked down in position. Each airline has different policies for the extension of landing gear during approach. In the event an airline had as a policy to extend the gears three minutes before landing that means the computer in the A320 would have applied forces to the shock absorber 180 times! In the case of the JetBlue landing gear it was adopted to decrease those checks in flight to reduce the risk of stress raises (cracks) and to modify the top part of the absorber of the landing gear to make it idiot proof. This particular gear was re-assembled incorrectly. I believe it took more than 10 landings before the landing gear failed.

The landing gear did its job and avoided a fatal event. By the way, the main housing in this gear is made out of a special aluminum to reduce weight on the aircraft