A recent article by Daniel Michaels, European Aerospace and Aviation Editor of the Wall Street Journal, discussed the potential dangers of retrofitting existing hardware with today’s software in an effort to make “dumb” components smart. Doing so allows more widespread use of automated control. His opening sentence reads, “Investigators probing two deadly crashes of Boeing Co. 737 MAX airliners are grappling with a hybrid of old and new technology, where a complex piece of software controls hydraulic pumps and motors similar to those used when Lyndon Johnson was president.”
First of all, I wonder why Michaels singled out hydraulic pumps and motors. Hydraulic cylinders and many of the valves on the 737 MAX are also similar to those used when “Lyndon Johnson was president.” However, so are many of the mechanisms used in this aircraft. I also take exception to his description of the airliners’ hydraulic pumps and motors as “dumb.”
By today’s standards, the hydraulic pumps used in the first-generation 737 were, indeed, dumb. Pilot pressure and fluid logic were used, and the pump circuits—not the pumps themselves—provided analog electronic feedback of pressure to the aircraft’s controls. Today’s pumps, however, are fitted with sensors for detecting output pressure, flow, and other important parameters. And with predictive maintenance becoming more widely used in industry, software in today's commercial airliners makes use of input from sensors and trend analysis to detect issues before they become problems.
Although I follow the author’s point, he singled out hydraulics technology as if it may be the root cause of the crashes. This early in the investigations, we don’t know whether hydraulic pumps or motors contributed these crashes. But when you consider the thousands of other components, mechanisms, and assemblies used on the 737 MAX, it’s just as likely hydraulics had nothing to do with the crashes.
Michaels seems to imply that if developers of the plane’s software did not fully understand all the workings of the pumps and motors, somehow the pump or motor is to blame. This reasoning has become all too common because most people are not very familiar with hydraulic systems or components, so hydraulics technology is a convenient target to blame.
But what I find interesting in all this is that some of the pumps used in the LBJ-era 737 use technology that has become a growing trend throughout the hydraulics industry. This trend is the use of electric motors for driving hydraulic pumps in mobile equipment. Granted, commercial airplanes are not normally considered off-highway equipment, but they definitely are mobile, and they don’t travel on highways.