The FAA design rulings incur hefty costs to the manufacturers.

Grounded Boeing 737 MAX 8 aircraft parked at Boeing field in April 2020
Photo: VDB Photos/Shutterstock

The Federal Aviation Administration (FAA) has been busy introducing new rules and policies due to recent events that have occurred in aviation. While disrupted flights with unruly passengers have given rise to stricter legal enforcement policies, tragic events such as the crash of two Boeing 737 MAX aircraft (on different occasions) incur new aircraft certification rules from the FAA. New certification rules often result in significant design and operational changes in the aircraft.

The “malfunctioning” of the MCAS system

The Maneuvering Characteristics Augmentation System (MCAS) was supposed to have malfunctioned on both occasions involving the 737 MAX aircraft. Engineering reviews by diverse investigative teams revealed other design problems associated with the aircraft.

The faulty design of the aircraft prevented pilots (on both occasions) from taking corrective actions to counteract the malfunctioning MCAS. In the aftermath of the crashes, the FAA set out new rulings for aircraft design.

The Airworthiness Directive (AD) issued by the FAA requires the installation of a new flight control computer (FCC) software, revision to existing flight crew procedures, the inclusion of a new MAX display system (MDS) software, changes to the horizontal stabilizer trim, and an angle of attack (AOA) sensor system.

American Airlines Boeing 737 MAX 8

Photo: Vincenzo Pace | Simple Flying

The FAA also evaluated a range of other factors, including proposed pilot training by Boeing. A revised pilot training, certification process, and maintenance considerations were implemented in addition to the AD. A Technical Advisory Board (TAB) was founded that independently evaluated the design recommendations by the FAA and the design changes by Boeing.

While the TAB included some FAA certification specialists, technical members involved in the original certification of the 737 MAX aircraft were excluded from the team. After all the changes were implemented, the FAA ended the 20-month grounding of the 737 MAX. Boeing got hit with an expense of nearly $20 billion from the two accidents and the grounding of the jet, not including indirect losses for canceled orders.

The center wing tank design

On July 17, 1996, Trans World Airlines Flight 800, operated by a Boeing 747-100, crashed into the Atlantic Ocean 12 minutes after taking off from New York’s JFK airport due to an explosion in the center wing fuel tank. A mixture of fuel and fuel-air vapor was found in the tank. The air conditioning packs installed just below the tank generated large amounts of heat.

Investigation into the accident showed that a short circuit in the Fuel Quantity Indication System (FQIS) within the center wing tank ignited the high-temperature fuel-air vapor in the tank, resulting in a catastrophic explosion. The FAA proposed a new ruling to prevent similar accidents by demanding additional protection against vapor ignition.

British Airways (Negus Retro Livery) Boeing 747-436

Photo: Vincenzo Pace | Simple Flying

The FAA required safe temperature margins in the fuel tanks with preventive layers protecting against any source of ignition in the fuel tanks. Moreover, redundancy in prevention against ignition sources where a single failure must not result in ignition. Other preventive measures were proposed to eliminate the flammable vapor in the center fuel tank.

The FAA estimated $800 million (in 2008) as the industry compliance costs for the new ruling. More than 3,200 Airbus and Boeing aircraft with center wing fuel tanks were affected by the change.

What do you think about new FAA rulings due to tragic events? Tell us in the comments section.


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