Arctic Ace

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Arctic Ace last won the day on April 4 2019

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  1. All the discussion regarding mandating MAX simulator training seems to be focused on the recognition and isolation of MCAS in the event that it is inadvertently triggered. There seems to be no consideration of why MCAS was designed in the first place. It was designed to artificially mimic the more stable flight characteristics of previous generation 737's at high AOA and therefore save customers the costly and time consuming process of simulator training. Any anomaly that results in the loss of electric trim and/or MCAS either through direct failure or a checklist following a system failure will result in an airplane being hand flown and manually trimmed with different flight characteristics at high AOA than previous models - the very reason for MCAS being designed in the first place. Simulator training should be a requirement not only for the exposure to and training to deal with an MCAS/runaway stab incident but also for the different flight characteristics and feel at high AOA that MCAS was designed to solve. Not requiring simulator training for this is akin to not requiring single engine simulator training because the airplane has two engines.
  3. My understanding is that in the flight regime MCAS is designed to operate in it is not so much a tendency for the airplane to pitch up but pitch control feel becoming lighter than desired when it should in fact feel heavier. MCAS AND trim designed to provide the proper "feel" to the pilot. A stability system more specifically than a stall prevention system.
  4. One other clue that the trim is running is sound. Unfortunately that would have been drowned out by the shaker. The sound of the trim spinning while hand flying and not manually (electric) trimming gets your attention.
  5. "From 05:40:42 to 05:43:11 (about two and a half minutes), the stabilizer position gradually moved in the AND direction from 2.3 units to 2.1 units. During this time, aft force was applied to the control columns which remained aft of neutral position." Just a WAG but possibly air loads from the nose up elevator position caused the stabilizer to creep nose down.
  6. Previously the Stab Cutout switches to cutout was not a memory action in the Runaway Stabilizer QRC. The only memory actions were Control Column - Hold Firmly and Autopilot (if engaged) - Disengage. I believe the logic behind this was that the control column actuated cutout switches which stop operation of the main electric and autopilot trim when the control column movement opposes trim direction would prevent further trimming until the checklist could be consulted. Unfortunately MCAS operation disables this function. Modern day training ingrains a sense of touch nothing without checklist guidance unless it is a defined memory action. This possibly resulted in delaying moving the trim cutout switches to the point of being unrecoverable - especially at lower altitudes. Opposite trim using the thumb switches should have worked though. This I don't understand.
  7. This is what I've been trying to say. This statement is right out of the Max and NG flight crew training manuals "Excessive air loads on the stabilizer may require effort by both pilots to correct the mis-trim. In extreme cases it may be necessary to aerodynamically relieve the air loads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually." Several years ago on the NG there was a requirement to trim the stabilizer full nose down prior to deicing to ensure the fluid was drained. In order to accomplish this the electric trim was used to its limit - which is not full nose down - the cutout switches were then moved to cutout and the remaining trim travel was done manually. From that experience I can tell you that holding a mis-trimmed elevator control back while trying to lean forward and operate a very stubborn crank would be no easy task! It is possible they were not successful trimming manually and flipped the switches back on. According to what we've been reading opposite trim inputs with the thumb switches should revers the MCAS inputs. Perhaps they ran out of time? MCAS, or any other runaway trim condition needs an immediate response or the possibility exists of it becoming unrecoverable IMHO
  8. Extreme cases of mis-trim may require the efforts of both pilots on the trim wheel and/or aerodynamic unloading to trim manually. What puzzles me is after the switches were reselected "on" the trim should have responded to the pickle switches being selected to nose up as MCAS can be reversed with opposite trim.
  9. Just to clarify. The stabilizer brake is actually two independent brake systems to hold the stabilizer in place. Either one can hold the stabilizer in its trimmed position. If they both were to fail without pilot intervention (holding the trim wheel) air loads could drive the stabilizer to its mechanical stops. Main electric trim can resist this motion, but control column opposition (elevator) will make the condition worse. MCAS does not affect this brake system. The MCAS disables the control column actuated cutout switches which stop operation of the main electric and autopilot trim when control column movement opposes trim direction.
  10. - I don't believe the auto pilot could have been engaged with a faulty stall warning -the control column (not the pickle switches) activated stabilizer cutout switches are on the MAX (control column movement opposite of trim direction) and will stop operation of the main electric and autopilot trim but is inhibited during MCAS operation of the trim - the Stab Trim override switch on the centre console when positioned to OVRD overrides the control column activated stabilizer cutout switches - the pickle switches actuate the trim motor through the main elec stab trim circuit - the auto pilot uses the auto pilot stab trim circuit - either of the STAB TRIM PRI and STAB TRIM B/U cutout switches will disconnect both the main and autopilot electric trim inputs to the stabilizer trim motor (different than the NG) - extreme cases of mis-trim may require the efforts of both pilots on the trim wheel and/or aerodynamic unloading to trim manually - last memory item on the Runaway Stabilizer QRC for pretty much all 737's is Grasp and Hold the trim wheel if the runaway continues after the Stab Trim Cutout switches have been positioned to cutout. All the switches just provide electrical commands to the trim motor. The cutout switches just cut these electrical connections off so I'm guessing the last memory item is in the event of the motor somehow being powered even though all switch connections have been terminated but that's just a WAG.
  11. Wonder if in the heat of the moment the guards were flipped without the switches actually being moved
  12. The MCAS trim inputs can be stopped and reversed with the pickle switches but may restart 5 seconds after the switches are released.