By Erik Dolson
Last week it was reported that versions of the MCAS software on planes sold by Boeing to the military were required to have three angle of attack sensors installed. Planes sold by Boeing’s competitor, Airbus, also have three angle of attack sensors. Three sensors are designed to compensate if one should be damaged.
Two civilian Boeing planes that crashed earlier this year, killing 346 people, had only one angle of attack sensor with similar software. It is believed that faulty sensors indicated the planes were approaching a nose up stall, and triggered software that flew the planes into the ground.
Why did Boeing sell planes with only one sensor, when most experts say that “critical systems” need redundancy, and the airplane maker was clearly aware of this issue from their experience with the military?
One possible explanation is that Boeing expected customers to order the planes with the additional sensors as “options.” This strategy, employed often by automobile manufacturers, allows a car, for example, to be advertised at a low price and then be sold at a higher price if options are selected, and the options themselves can be sold at a higher margin.
According to the New York Times, options can add millions of dollars to the price of a plane.
So, a question to be asked is whether Boeing deleted one or two of the angle of attack sensors with the expectation of adding them back to planes at customer request and at a greater profit, or “gaming” the sales process.
If so, a follow-up question is where in the development process of the civilian 737 Maxx was that decision made, who made that decision, and who signed off on it.
Because it is hard to imagine engineers in a company that claims that “safety is our top priority” would have signed off on such an obvious problem.