“A set of stairs may have never caused so much trouble in an aircraft,” writes The Los Angeles Times (March 18, 2019). First introduced as a short-hop commuter jet in 1968, the Boeing 737-100 had folding metal stairs attached to the fuselage that passengers climbed to board before airports had jetways. Ground crews hand-lifted luggage into the cargo holds in those days, long before the advent of motorized belt loaders.
That low-to-the-ground design was a plus then, but it has proved to be a constraint that engineers modernizing the 737 have had to work around ever since. The compromises required to push forward a more fuel-efficient version of the plane — with larger engines — led to the controversial flight control software system now under investigation. The crisis comes after 50 years of remarkable success in making the 737 a profitable workhorse. (Boeing has a massive 737 backlog of 4,700 orders).
But the decision to continue modernizing the jet, rather than starting at some point with a clean design, resulted in engineering challenges that created unforeseen risks. “Boeing has to sit down and ask itself how long they can keep updating this airplane,” said a former pilot. Few, if any, complex products designed in the 1960s are still manufactured today. The IBM 360 mainframe computer was put out to pasture decades ago. The Apollo spacecraft is revered history.
Over the years, the FAA has implemented new and tougher design requirements, but a “derivative” gets many of the designs grandfathered in. Still some aspects of the legacy 737 design are vintage headaches, such as the obsolete ground clearance designed to allow a staircase. To handle a longer fuselage and more passengers, Boeing added larger, more powerful engines on the 737 MAX, but that required it to reposition them to maintain ground clearance. As a result, the MAX can sometimes pitch up. Hence the software fix..
The 737 has survived other crises. In a 1988 accident on a Hawaii flight, the entire top of the plane came off. A flight attendant was sucked out and 65 were injured because of faulty lap joints in the aluminum skin of the fuselage, which Boeing reengineered.
Classroom discussion questions:
- What are the plusses and minuses of reengineering an older plane model?
- Is it possible that this is a training or maintenance problem–not a design one?