FAA takes first steps for re-certification of the MAX

December 6, 2019, ©. Leeham News: The FAA issued a draft of the updated Master Minimum Equipment List (MMEL) for the Boeing 737 MAX 8 and 9 on its website yesterday. It’s there to be commented on by anyone who has input to its content within 30 days.

This step is the first external sign the re-certification of the 737 MAX has begun.

Master Minimum Equipment List, MMEL

A Master Minimum Equipment List, MMEL, is the reference for the pilots if the aircraft can fly on when a fault has appeared on the aircraft. A modern airliner has many systems with redundancy and several other less important part systems that are not needed if the flight crew adapts the flying on the next leg so they can return to a home base from an outstation for example.

A good example of how this works is an item that changed between the first revision of the MMEL and the updated one, Revision 2 (the one which is now presented for comment). MMEL for MAX 8/9 in Revision 1 accepted the aircraft could fly the next sector if the manual trim switches worked on one side of the aircraft’s dual control yokes. This then had to be the side of the Pilot Flying  (PF). In practice, a crew would let the pilot fly the next leg which had the functioning trim switch on his yoke. The MMEL position for the manual trim switches also prescribes how fast this fault must be fixed (if this times passes the aircraft is grounded until the item is fixed).

The updated list now says both manual trim switches must work. No malfunction is accepted as there is no longer an MMEL position for the trim switches. When an item like trim switches or warning lights or other functions which have redundancy in the aircraft does not have a position in the list, it means the aircraft’s base configuration has to be intact for dispatch = be OK for the next flight.

The revised checking of the Flight Control Computers (FCCs) and their sensors (see today’s Corner) means other positions are revised or are no longer needed/valid. MCAS has no position on the MMEL meaning any issues with MCAS or its sensors during a flight means it must be corrected after the flight before the aircraft can be dispatch again.

38 Comments on “FAA takes first steps for re-certification of the MAX

  1. Interesting, not required as it can be turned off or auto disable but but can’t dispatched unless its all working.

  2. The FAA and Boeing are going to have a lot of sleepless nights if this thing is allowed to fly again. They were warned, but they didnt listen. Later they will.

    • For the software audit which should be in the works, I wonder how long it takes. As if no mistakes will be found, it’s their job to find mistakes. So the audit holds the certification process now. After the audit sim testing might follow and I’m sure it will be checked in detail because last time the sim failed. Long time till flight testing can start and that might only be for FAA, EASA, Canada and Brazil. Other regulators might wait for them to certify first and then start their own process. Interesting times, the industry is changing.

  3. Good. I’m glad they’re bringing it back into service. If the DC-10 can (and did) make a comeback, the 737MAX will be alright!

    • …until it isn’t. What is your recommendation if the 737MAX decides to mimic a lawn dart, after it was cleared for return to service?

    • Too many delays, it will be good to have the 738 Mac back in the air! This is not all about Boeing and the 737, too many runaway trims fails every month and they don’t even get documented because there is no emergency. Too many AOA fails and no valid signal to help identify the fails. The industry as a whole needs to learn from these mistakes but too many people just want to find fault with Boeing!

  4. Rather an unfortunate choice of photo for this article…. showing a 737 in a nosedive!

    • Not sure what photo you are looking at but my computer shows 3 MAX in a level formation or two slightly climbing flight.

  5. It’s US only. I don’t think anybody outside of the US is listening anymore.

    But regulations are regulations. The FAA will go through them, even if nobody believes anymore. Afterall, regulations don’t apply to Boeing.

  6. Perhaps we could establish a Boeing/FAA bashing section for those who want to keep doing so and leave the main forum for those interesting in Aviation and the tech end?

    • A forum just for the Asto Turfers? you are too kind.
      ( I’d just move the “Boeing best” posters there.
      No extra hassle for the sane posters.)

    • TW for my part, I don’t care which airframer/authority it is, I’m not comfortable with any airframer knowingly putting faulty parts on an aircraft, submitting it for approval, and having aircraft flying with those faulty parts, are you ?

      I don’t care if it’s Airbus, Embraer, Irkut, Boeing, EASA, CAAC, or the FAA, or anyone. Real people, real families are flying on these aircraft, they have to be as safe as they can be.

      I note in the Seattle Times article it says “Boeing said Friday that all the affected planes in use have been inspected and fixed.”

      The sheer audacity to submit aircraft for approval knowing that there are faulty parts installed makes me shiver. To have those aircraft flying until you are found out is as you have put it before, beyond the pale.

      If I was in charge of the certifying authority, and it were up to me, I’d retain the certification authority for each, and every aircraft, and I would only certify the aircraft as fast as I could with the limited staff that I had, and I’d make sure everything was checked, and I mean absolutely everything.

      As far as the MAX fiasco goes, I don’t think that Boeing have done themselves any favours carrying on business as usual, I think they would have been better served being a lot more open. A lot of the doubts/conspiracy theories would be answered if they provided answers.

      • Bit of a quandary. ( and defective thinking : there is s reason neither lawyers nor MBA types design airplanes ) .

        What makes sense or is prudent behavior on the aircraft side of things is destructive in the share holder value ecology. There you must wag the dog at all cost.

      • Yep.

        I’m of the view that Boeing must lose their license. If history is anything to go by, it would then take 3-4 years to certify Boeing airplanes.

        With regard to the MAX, Boeing need to be forced to start again. Posting the minimum equipment list isn’t relevant if the equipment doesn’t work.

      • Think the slat tracks were made without serial numbers and when Boeing finally reacted at the higher levels it was not that easy tracking the faulty ones down. One could assume the FAA have a list of flight critical hardware that must have serial numbers and that the manufacturer must keep track of where that are installed and similar requirements for Airlines which sn’s they must track in their MRO systems and in an OEM defined tracking system, (like the Lookheed ALIS, but better executed).

    • @philip
      I disagree – regulations do apply to Boeing, rest of the world confirms that,for now. FAA is trying but I’m not sure if enough.

      You mean leave the main forum to Boeing Best Boys to not be troubled? 😉

      My position is the same – A, B or C or any letter – doesn’t matter for me.

      Yeap, last Boeing’s fine by FAA shows how much safety is a priority in Boeing :/ Only for me sum of 3,9mln USD seem so small for deliberate installing faulty parts, cheating in certification and putting in danger flying public? Boeing even doesn’t have to go to bank, just opens a small pocket in his walletto pay this. Well job done FAA, again :/

    • Transworld, Thank you, when the MAX is cleared to enter service, it should be one of the most safest planes in the sky. Boeing has made the MAX the main focus for many months and yet some can do no more than rant and rave that they won’t fly on it. Thank you gents, it will open a few seats for non-revs and I have no qualms flying the MAX.
      Very little on this forum about the pilots on both planes contributing to the crash. Never heard about any similar problems on MAX’s here in the states.

      • Not much chance to touch it off.
        US airlines didn’t have enough planes and got them late.
        Boeing seems to have been careful to foist those early frames on 3rd worlders.
        Accumulated US airline hours for MAX should be less than a third of MAX cohorte hours.

  7. MCAS Software will not solve Boeing’s Faulty Airframe. If they continue this Software Solution, more inocent people will die. Boeing must solve the Root Cause of the problem, that is the improper placement of the larger CFM Leap Engines forward and up in front of the wing, forward of the Center of Gravity.

    I, Dennis E Sullens (Aviation Quality Assurance 29 year’s, that includes 19 year’s with Boeing [1988-2007], Retired) feel that Boeing and the FAA are looking at the Max problem all wrong. The Root Cause of the Max Flight Instability (Tendancy to Stall during certain required FAA maneuvers) is the incorrect placement of the larger CFM Leap Engines being placed forward and up in front of the wing, forward of the Center of Gravity.

    Several Aviation Engineers believe that with the Engines being placed PROPERLY under the wing, similar to the 737 NG (Next Generation) Aircraft, close to the Center of Gravity, the Max can pass the Flight Tests required by the FAA, and do so without MCAS, thereby obtaining near 737NG levels of flight stability. The 737NG do not have, and do not need MCAS.

    No MCAS. No problems. Everybody is happy.

    For the flying public the mere mention of MCAS brings fear and distain, even nausea. This alone is enough for me to seek a better solution.

    For Boeing, this Reengineering solution will utilize more than 98% of the existing Aircraft body. They only need new engine hangers, and taller landing gear which they currently have on the 737 Max 10 that are 9.5 inches taller. See FN02 below. This height increase will provide more than enough room for the FAA required 17 inches of ground clearance with the larger Leap Engines. To view the 2018 September video just YouTube or Google search: “Boeing 737 Max 10 Landing Gear.” Or see FN02 below.

    The 2nd problem this will solve for Boeing and the FAA is that this Reengineered aircraft can be called a new Aircraft, perhaps with a new name like 737 Eagle? Something Majestic, and safe. I am confident that the general public, and other Civil Aviation Authorities around the world will be more accepting of a Redesign than a Software Patch or Band Aid solution such as MCAS.

    This reminds me of the Baseball comedy in 1987 where the Team Owner wanted to reduce Comfort and Safety of her team. The team was approaching there Charter Aircraft that is usually very comfortable and new. This time it was an old DC-3 where the mechanic was using “DUCT TAPE” on one of the Propellers. Everyone in the audience laughed. Little did they realize how close to the truth this really is. Ref. 1987 movie “Major League” with Charlie Sheen playing the “Wild Thing” Pitcher.

    MCAS is a Patch or Band Aid solution. The correct solution is to build the Aircraft where it doesn’t have inherent Flight Instability, such as the 737NG, that has a 50 times better Safety Record of 0.06 Crashes per Million hours of Flight time, as compared to the Max with 3.08 Crashes per Million hours of Flight time. See FN06 below.

    The alternative is a very reluctant FAA certifies the Max, and then later, other Civil Aviation Authorities (eg EASA, CAAC) find more items wrong, either Software or otherwise, thereby damaging the FAA’s more than 61 year world renowned reputation, and Boeing’s 103 year reputation for Quality and Safety. And most importantly, costing more inocent lives, some of which will be flight crew.

    You see, with a “Watered Down” version of MCAS, the Max could crash by MCAS NOT ACTIVATING because one of the Angle of Attack sensors malfunctioned, or because MCAS only activated one time, when more was needed. No, MCAS was a bad idea from the very start. And MCAS Software changes cannot remedy Boeings faulty Airframe. See FN01, FN04 and FN05 below.

    The Repositioning of the Engines properly under the wing solution is shared by many Aviation Engineers, see below. I will NOT fly a Max ever again, unless the Engines are placed properly under the wing, closer to the Center of Gravity, thereby eliminating the need for MCAS.

    Dennis E Sullens
    (503) 309-9490 Smartphone with text

    Weblinks and portions of various Articles below:

    [Inside Brackets are added by Dennis E Sullens, edits, additional info etc.]

    FOOTNOTE 01. Aviation Engineers Criticize Engine Placement.¶


    by AARON HILSZ-LOTHIAN, JULY 10, 2019¶

    “Past and present engineers within the aviation industry have flagged the aircraft as unsafe to fly because it is not a software problem, it is a structural problem that required the MCAS system in the first place.”¶

    “A redesign of the engine position on the aircraft would cost a ridiculous amount of money and would likely render the grounded aircraft useless [I, Dennis E Sullens think a safe reenginered Max will sell and make billions of dollars]. Flight testing and new production methods would have to be conducted, leaving the idea in the scrap bin.” [But there is still time for the Max 10, and may cost Billions more, and more death’s if MCAS’ short cut is pursued. The question that should be asked is: “What if MCAS can NOT safely solve the inherent Flight Instability in the Max? What if placing the larger Max Engines PROPERLY under the wing is the only safe solution, regardless of cost?]¶

    “Despite this the idea to add or redesign hardware hasn’t been completely disregarded as EASA director Patrick Ky said, retrofitting additional hardware relating to the angle of attack sensors was still an option.”¶

    FLAGNOTE 01 (Continued).¶



    “A former Boeing official has refused to turn over crucial 737 MAX development documentation, after he cited the Fifth Amendment.”¶

    “According to The Seattle Times, Mark Forkner, Boeing’s chief technical pilot on the 737 MAX program, refused to turn over documents requested by the U.S. Department of Justice as part of their investigation.”¶

    “During his time at Boeing, it is said that he was often anxious about deadlines and management pressure, during the development of the 737 MAX, resulting in frequent visits to peers for help.”¶

    “Adding to the curiosity within the investigation, Forkner was behind the suggestion of not informing customers of the Maneuvering Characteristics Augmentation System (MCAS).”¶

    “MCAS was designed in a last minute attempt to overcome a handling characteristic, this saw the nose pitch up as a result of the forward and high mounted CFM LEAP engines.”¶

    “A flawed design, the system would take angle of attack data, from a single sensor, and adjust the horizontal stabiliser to point the nose down if a stall was imminent.”¶

    “It is this system that is believed to be the cause of the crashes of Ethiopian Airlines Flight 302 and Lion Air Flight 610, both resulting in 346 lives gone.”¶

    “Worsening the situation, the zero mention of MCAS was paired with an agreement to train pilots digitally through a one hour differences course.”¶

    FLAGNOTE 01 (Continued).¶

    Software Won’t Fix Boeing’s ‘Faulty’ Airframe¶
    By George Leopold, 03.27.19 ¶


    The saga of Boeing’s 737 MAX serves as a case study in engineering incompetence, and in engineering ethics – or the lack thereof.¶

    New details have emerged about the competitive pressures placed on Boeing 737 engineers as the aircraft manufacturer scrambled to fend off defections by major U.S. airlines to rival Airbus. The European consortium was challenging Boeing’s flagship product with its upgraded A320neo. According to reports, U.S. carriers like American Airlines were preparing to switch to the longer-range Airbus mode.¶

    Boeing responded with what it claimed was an upgraded version of its workhorse 737 equipped with a larger CFM LEAP engine providing longer range and greater fuel efficiency. The larger engines required Boeing engineers to place them far ahead of the wing leading edge to achieve [FAA required 17 inches] ground clearance.¶

    That design decision meant the 737 MAX would tend to pitch up while accelerating or when the aircraft experienced a high angle of attack – the angle between the wing and the direction of flight. The proposed solution to the pitch-up problem—and a means of achieving flightworthiness certification—was a software system called MCAS.¶

    Critics assert the engine placement effectively made the 737 MAX series a fundamentally different aircraft with different handling characteristics requiring new operational software and pilot training. The re-certification process Boeing sought to avoid for competitive reasons would have been lengthy and expensive.¶

    Among Boeing’s critics is Gregory Travis, a veteran software engineer and experienced, instrument-rated pilot who has flown aircraft simulators as large as the Boeing 757. Travis posted a damning critique of the 737 MAX fiasco last week that concluded: “It is likely that MCAS, originally added in the spirit of increasing safety, has now killed more people than it could have ever saved. It doesn’t need to be ‘fixed’ with more complexity, more software. It needs to be removed, altogether. (Travis is sharing his evaluation as a Google Doc, located here.)¶

    Travis is unequivocal in his assessment of the Boeing 737 MAX. “It’s a faulty airframe. You’ve got to fix the airframe [and] you can’t fix the airframe without moving the engines” back and away from their current position.¶

    Ultimately, Travis also bemoans what he calls “cultural laziness” within the software development community that is creeping into mission-critical systems like flight computers. “By laziness, I mean that less and less thought is being given to getting a design correct, and simple – up-front,” he wrote. “What needs to happen, I think, is for liability to accrue where it is generated.”¶

    Incompetent or Unethical?¶

    Whether the cautionary tale of Boeing 737 MAX is a question of ethical engineering – doing things right the first time, making damned sure mission-critical systems work with five nines (99.999 percent) or higher reliability with built-in redundancy – remains an open question.¶


    That, or economic and competitive pressures that led Boeing to effectively conceal the existence of MCAS as a way to avoid a lengthy recertification process for the 737 MAX, a process requiring extensive pilot retraining on expensive new simulators. All would have raised the unit cost of each aircraft by millions of dollars, Travis noted, thereby reducing Boeing’s chances of competing with the Airbus 320neo.¶

    The Boeing 737 MAX tragedies also recall the engineering decisions that led to the shuttle Challenger disaster in 1986 and the Apollo 1 fire in 1967. Boeing’s haste in responding to the Airbus challenge reminds Travis and others of the group-think curse called “Go Fever” during Project Apollo that eventually killed the crew of Apollo 1 during a launchpad simulation. In that case, crew safety was sacrificed in the name of schedule.¶

    Boeing’s engineering decisions while hastily developing the 737 MAX have ultimately resulted in the deaths of [346] people.¶

    Travis expects one of two possible outcomes for Boeing. “I see a scenario where they don’t sell any more of these planes.” More likely, he continues, is an announcement in coming days [Posted 27 March 2019] that the aircraft maker is fixing the MCAS software to handle inputs from multiple angle of attack sensors.[FN 01 and FN 04].¶

    Either way, Travis concludes, “Software [now] stands between man and machine.”¶

    — George Leopold is the former executive editor of EE Times and the author of Calculated Risk: The Supersonic Life and Times of Gus Grissom (Purdue University Press, Updated, 2018).¶

    FOOTNOTE 02. 737 Max 10 Landing Gear are 9.5 inches taller.¶


    FLAGNOTE 03: Virgin Airlines switches Max 8 to Max 10’s.¶




    FLAGNOTE 05. US FAA Regulations for Anti Stall and Flight Stability of Commercial Aircraft against 737 Max.¶

    “The LEAP engine nacelles are larger and had to be mounted [if main landing gear is not taller as the B-Max 10] slightly higher and further forward from the previous NG CFM56-7 engines to give the necessary [17 inch] ground clearance. This new location and larger size of nacelle cause the vortex flow off the nacelle body to produce lift at high AoA [Angle of Attack]. As the nacelle is ahead of the C of G [Center of Gravity], this lift causes a slight [???] pitch-up effect (ie a reducing stick force) which could lead the pilot to inadvertently pull the yoke further aft than intended bringing the aircraft closer towards the stall. This abnormal nose-up pitching is not allowable under 14CFR §25.203(a) “Stall characteristics”.¶

    Several aerodynamic solutions were introduced such as revising the leading edge stall strip and modifying the leading edge vortilons but they were insufficient to pass regulation. MCAS was therefore introduced to give an automatic nose down stabilizer input during elevated AoA [Angle of Attack] when flaps are up. [Dennis E Sullens: According to “Aviation Best Practices” and many Aviation Engineers (FN01), at this point of failing the Wind Tunnel and Flight Testing, Boeing should have made BOTH main and front Landing Gear taller and then place Lager Max Engines PROPERLY under the wing, thereby bringing the Max to near 737NG levels of flight stability, passing the FAA Flight Stability requirements, and thereby eliminating the need for MCAS. No MCAS, no Problems. Everybody is happy.]”¶

    14CFR §25.203 Stall characteristics.¶

    “(a) It must be possible to produce and to correct roll and yaw by unreversed use of the aileron and rudder controls, up to the time the airplane is stalled. No abnormal nose-up pitching may occur. The longitudinal control force must be positive up to and throughout the stall. In addition, it must be possible to promptly prevent stalling and to recover from a stall by normal use of the controls.”¶


    FLAGNOTE 06. Flight Crashes Resulting In Death’s, Aircraft Company and Model Compared.¶


    Boeing’s Troubled Tanker Has Its Wings Clipped Again¶

    One of the company’s flagship military programs suffers a fresh setback.¶

    Lou Whiteman
    Sep 14, 2019 at 4:32PM


    “In a worst-case scenario, cargo pallets rolling free in the cargo hold could be a danger to crew and could unbalance the aircraft, making it hard to control. It is not yet clear if the issue was limited to one defective latch, or there’s a systemic problem that will lead to a comprehensive redesign and retrofit.” End of Article.¶

    [Dennis E Sullens: if “comprehensive redesign and retrofit” is appropriate for a 767 cargo latch when the problem is “systemic” then even more so justified with the systemic 737 Max Flight Instability (due to improper engine placement), don’t you think?]¶

    • “This height increase will provide more than enough room for the FAA required 17 inches of ground clearance with the larger Leap Engines.”

      That happens to be wrong.
      The rather complex articulation of the MAX10 gear leg does not provide for an increase in static “on the ground” height.
      What it does though, is by way of being softer sprung, increased height with buildup of lift. “lifted out of the springs”.

      Afaics any path to a sane arrangement of things on the 737 is blocked by carefully inherited ( set of thing that makes it competitive against the A320) ballast. Any sane fix would nix one or more of these advantages. They would also collide with given customers assurance “no change vs NG beyond better engines”.
      Painted into the corner of a hypercube.

      • Not saying I agree with everything Dennis says, but the spring/dampener action on the “longer” landing gear could be easily adapted (for the MAX 8 at least, maybe not for the MAX 10), to create enough space while under load (on the ground).

        • Any an inch higher and you need slides for the overwing exits. 🙂

          … as I wrote before : painted into the corner of a hypercube.

    • Thanks Dennis. I hope you won’t get shot for this. Given Boeing’s refusal to come clean, it’s necessary. Still taking it in.

    • If they finally put the engines down they would facepalm themselves and everybody would laugh since they could have done bigger and more efficient engines.

      But they should take the hit, learn the lesson and man up and do what they should have done directly. They lost all credibility and it will take a long time to earn trust.

      You have to imagine, if MCAS were little bit better they would have gotten away with it.

  8. Buy a majority the comments here are ill informed. Read the real reason as to why these planes lost control. You might be surprised.

    • Buy a majority the comments here are ill informed. ”

      I don’t buy that :-))))))))))

      • I guess no one in this thread read any of Bjorn Fehrm’s analysis?.. in which he stated that MCAS was not intended to address a safety deficit but rather to make the MAX handle like the NG to hasten certification. I guess no one realizes that both black boxes were recovered, root causes found, and the corrections are being targeted directly at those root causes. No doubt Boeing screwed up, and a lot of people died because of it. Sooner or later another Max may go down, and so may an A320. We don’t live in a perfect world. I work in in the same nonsense where corporate leaders get overconfident, and think success is automatic – overruling engineering recommendations. The current leaders of Boeing, Airbus et al have all learned a terribly painful lesson with this mess, but they’ll be mostly gone (retired) in 10-20 years and the next generation will end up doing the same thing all over again. Humans screw up, it’s sadly inevitable.

        • I prefer the JATR and the Lion Air crash reports. Those reports make it clear that Boeing deliberately misled pilots with regard to the existence of MCAS, causing the first crash, and then deliberately mislead pilots with regard to how to deal with an MCAS malfunction, causing the second crash.

        • NG behavior is certifyable ( barely :-).
          MAX not.
          Make the MAX behave like the NG and it too is certf… 🙂
          IMU MCAS ~= “make MAX behave like NG” is a rather big fib, a lie.

        • I’m afraid Boeing & the FAA didn’t get away with that one.

          They tried / try by all means to convince everyone MCAS doesn’t have to do anaything with Stall protection, it is just make a MAX fly like an NG. So, some uncountained elements suggest to fly without MCAS. That let to silense first, then a lot of discussions, diversions, further delay..

          ” The JATR report recommended the FAA review the stalling characteristics of the 737 Max without MCAS and associated systems to determine if unsafe characteristics exist and if so, if a broader review of the system design was needed.

          JATR said MCAS and those systems could be considered a stall identification or stall protection system, depending on how the aircraft handled without them.

          Boeing has said MCAS was not meant to prevent stalls and was instead designed so that the 737 Max would have similar handling characteristics to its predecessor, the 737 NG.”


          And I guess we can understand why “Stall Protection” is . If Boeing and FAA approved a Stall Protection system the way they did, that looks “complicated”. As do the $olution$.. So they tried/try powerplay, but that has worked counterproductive too.

      • Coming from someone who earlier today penned “in the share holder value ecology”?

        I don’t share [those] values: pot, meet kettle… :-))))))))))

        • Sadly its true, the TFH are running as rampant as the bull of Pampalano .

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