Readers react

Examining the MAX

Our July/August article “Learning from the MAX” gave readers lots to think about. Herbert “Skip” Hickey, AIAA senior member emeritus, said that although the article was interesting, the pilots’ lack of surprise in the depicted scenario did not “properly emulate the performance” of the Lion Air and Ethiopian Airlines crews.

“Since the cause of the loss of control was known beforehand, the proper commands from the captain to the first officer [in the article] were given precisely and unequivocally and did not follow procedures as given in the flight manual to wit, the throttles were moved to idle. This was not in the flight manual. This eased the recovery procedure by reducing the nose up pitching moment and decreasing speed. As pointed out in the article, speed is the enemy because the increase in elevator hinge moments could result in excessive control forces making recovery from a nose low attitude difficult. So the simulation was interesting, it showed recovery could possibly have been accomplished provided the pilots did not follow handbook procedures.

“However, airline pilots assume emergency procedures have been verified and validated and, therefore, follow procedures. The MCAS is an ‘add on’ to the stall identification system already in the 737NG. … Since the MCAS was an add on, it was assumed by Boeing that the recovery procedures as provided for the 737NG would suffice. Thus, the simulation could have highlighted shortcomings in the procedures due to the addition of MCAS and their order of accomplishment. This could have been revealing and instructive,” wrote Hickey.

Others had a different take on the MAX story. For Mike Helton, a risk management expert and AIAA senior member, the article “relates the very tenuous boundary between a boring, ho-hum flight in a 737 MAX 8 airliner and one that suddenly goes unstable for the pilots, sending the aircraft into the ground at almost the speed of sound.

“It is rather obvious that the manufacturer does not have a process quality control system in the implementation of this aircraft. Reports on the continuing congressional hearings continue to expose other problems that were not considered before. A high-quality comprehensive set of processes at each phase with audit controls and standards would have picked up the many shortfalls in the design, development, testing and implementation of this vehicle. It might take a little longer and cost a little more up front, but today, we would have the MAX 8 flying and with a clean record.”

Jet A fuel vs. batteries

After reading our June article “Flying electric,” AIAA associate fellow Thomas Brogan doesn’t think the story adequately emphasized the “really stark issue for an all-electric aircraft” of the comparative energy/mass between batteries and Jet A fuel.

“The energy density of state-of-the-art batteries is about one megajoule/kilogram (mj/kg). It has remained at or near that level for many years, in spite of plentiful motivation to improve it. The energy level of Jet A is 43 mj/kg. This is an enormous differential even given that only a fraction of the Jet A energy content is recovered as work. Moreover, unlike with batteries, the Jet A is burned off during flight, reducing the work required to power the airplane,” wrote Brogan.

Accepting risk in aerospace

Frank Hurley, an AIAA associate fellow emeritus, thinks AIAA Executive Director Dan Dumbacher “hit the nail on the head” in his June Flight Path column, “Scar tissue,” which calls for a balanced approach in determining what are acceptable risks in technology development. As deputy chief scientist at NASA Headquarters in 1984, Hurley remembers the negative reactions he got to a suggestion of extending flight demonstrations for a remotely piloted experimental aircraft at NASA’s Dryden Flight Research Center in California [now NASA Armstrong].

“If our flight research (Dryden’s middle name!) isn’t scattering some debris across the Mojave Desert, we’re not trying hard enough. Yet, fear of failure rather than lust for success had ruled. By the way, I’m blaming NASA’s culture rather than its leadership for this, as an excellent team occupied the administrator’s office at that moment in history. Perhaps our engineers and managers could be more aggressive if some really gifted spinmeisters from the political world were protecting them. Here’s a sample press release: ‘NASA is pleased to announce that the ____ unmanned flight research vehicle has been tested to destruction, AS PLANNED, to capture data that will enable confident design of the Air Force’s ______ combat aircraft,’” wrote Hurley.

Modifying us for living in deep space

“Thanks for carrying the article ‘Homo sapiens astronauta’ [July/August],” AIAA senior member Michael Michaud emailed. “It is a fascinating look at future possibilities, well presented by Adam Hadhazy.”

Apollo 11 and risk

Reading our special section about the Apollo 11 anniversary, Robert J. Wetherall, an AIAA associate fellow and a program manager at Lockheed Martin Aeronautics, found “Curb your disillusionment” by Samantha Walters “honest, enlightening and telling, especially with regard to risk management.” He writes that with the advent of computer-aided design, manufacturing and simulation in the 1980s and 1990s, “an environment was created where taking risk in testing could prove embarrassing and costly, so the industry retrenched to the point where major systems can now take decades, not years to develop.

“Unfortunately, today’s industry views any failure as a significant setback, many times resulting in the end of a program or effort, which can be very damaging to the nation. A recent example is the Falcon HTV-2, which, after two imperfect but very valuable flight tests, was terminated. Shortly thereafter, we discovered that our adversaries (who had started or advanced their own hypersonics programs as a direct result of our Falcon HTV-2 effort) moved significantly ahead of us, and as a result our nation now finds itself playing catch-up. This was brought into clear focus in a quote from a Washington Post article attributed to U.S. Air Force Gen. John Hyten, commander of U.S. Strategic Command, ‘We had a couple of failures [with the HTV-2], so we kind of stopped and regrouped to look at the overall structure, to make sure we understood the technology — what was working, what was not working. From my perspective, I’d have liked to have just learned from that mistake and kept going. Don’t stop.’ To me he’s saying, ‘Let’s do what Apollo did … learn from the failures and continue toward the goal.’

“We understand that Cold War tensions fueled our commitment to Apollo. But that incredible program showed us what we can accomplish when we do commit ourselves to a goal, no matter the reason, and no matter the cost. I would hope that as a nation, and as a planet, that we can make similar commitments going forward, not out of fear but out of a desire to accomplish those goals that depend more on commitment and balanced risk-taking than about anything else.”

Also in reaction to our Apollo 11 anniversary section, Eli Gai, an AIAA fellow and former vice president for engineering at Draper noted the contribution of Draper Instrumentation Laboratory, then the MIT Instrumentation Laboratory, in navigation for Apollo 11.

“The instrumentation lab got the first Apollo contract on a sole source basis to design the guidance, navigation control and computer for the mission. They got it because NASA was reluctant to use radio navigation, suspecting that the Soviet Union will jam the system if they fall behind. The instrumentation lab proposed a self-contained inertial navigation system similar to the one they designed for the Polaris missile. The Apollo guidance computer that used integrated circuits was the beginning of the digital era,” wrote Gai.

Full text of edited letters

Readers react