Vsplat

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Vsplat last won the day on March 22

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  1. Kip, do you really want to see that bet called?
  2. Agreed. Saved my Dad. 'But', he said with a smile, 'this really is a pain in the ...' Sorry, could not resist Vs
  3. A minor point here. The 737MAX still holds a valid type certificate in most parts of the world. The aircraft is not technically grounded - it is restricted from commercial service. Many have flown since the restrictions came into force, ferry flights to storage for example. Re-certification would require an additional step of revoking the existing certification. Given how much time has passed, I think that still possible, but remote. Reading some of the other threads on this, there does appear to be some smoke to the story about refurbished AOA sensors. Whether that turns into something more, we'll see. That might attract a lot of lightning and split the focus somewhat. None of this takes away from the obvious - serious errors were made in the certification of this design and the prioritization of getting the common type rating seems to have resulted in the introduction of a fatally flawed MCAS system. What I would like to know is, for operators who own only the MAX and for whom a common type rating is unimportant, why have MCAS at all? Can it be disabled at this point? Vs
  4. I think there are two discussions being woven here and that is causing conclusions from one discussion to apply to both. Permit me an attempt to separate the discussions for a bit. First off. I agree with Don that, once the unusual attitude has been reached, the useful time for AoA as a reference in a civilian transport has passed. The purpose of the AoA, if any (and that is the subject of some debate here), is predictive and intended to refine situational awareness in order to avoid an undesired aircraft state. As we have seen, the transition to that state can be rapid and confusing. The AoA provides information directly that must be inferred from other instruments such as airspeed, pitch, etc. That is valuable at times. In the case of MCAS, we have a unique threat, in that an aggressive intervenor may create an unsafe state from safe one. In this case, the first sign of trouble would have been that AoA indication and the associated DISAGREE message. While we will never know for sure, in my opinion a crew faced with that warning ahead of entering the MCAS active zone would have had a leg up. So yes, AoA is a valid countermeasure, but in a proactive, vice reactive sense. WRT the input of thrust couple at high pitch angles, I have to disagree with your assertion that the moment would be constant or not rapid in onset. When airspeed is low, control surface authority is diminished. Higher pitch, decaying speed would lead to lower authority. So the countering effect to a thrust couple would reduce commensurately. Apart from the couple, where the vector below the C of G rotates the aircraft up, the thrust vector becomes more vertical as pitch angle increases, adding an increasing vertical acceleration component. All this adds up to: Apply firewall thrust at a high pitch angle and the effect can be very dramatic and the response would not feel at all linear. On a twin, with all of the excess thrust normally available, this is not going to be a gentle thing. To Don's point, this would be even more evident on the MAX. Vs
  5. boestar, there are other pitching moments in play when the engines are mounted either underwing or above the fuselage. In high pitch, low speed events, firewalling the thrust on aircraft like the MAX will induce a pretty strong upward pitching moment that can worsen the situation. I believe this was one of the guiding forces behind MCAS to begin with. Then there are the swept wing characteristics at mach. There are low and high speed buffet boundaries and a high altitude, unusual attitude event in any direction can lead you to a jet upset in pitch, roll or both, where the forces in recovery can be close to structural limits. While most modern designs should avoid control surface 'blanking' from deep stall, I wonder now how carefully that lesson is applied in modern designs where digital override is seen as an artificial substitute for good aerodynamics. If the stab loses any authority during a deep, very high AOA stall, then recovery can involve roll as well as pitch input. This was spoken to during the ancient (and now discredited) American Airlines Advanced Aircraft Manoeuvring course. Stall avoidance systems for these aircraft tend to incorporate predictive logic, 'phase advance' to start recovery ahead of the onset of anticipated pitch or roll forces that might deepen the stall. The AOA plays an important roll there, not during recovery, but in establishing situational awareness ahead of an event so the crew is not trying to catch up to the aircraft in a deteriorating situation. All IMO. Vs
  6. I have to wonder what happens after the first lightning strike. These aircraft aren't exactly festooned with static wicks. Vs
  7. Thanks Don. Yes, that 20 deg value keeps coming up and while I've seen it associated with full scale deflection in a couple of other places, your AMM reference is definitive. The damage may ultimately hide the true state of that sensor and any installation-induced issues from us, but hopefully the investigators will be able to identify whether a bad ground, perhaps static discharge during installation or some other issue crept into the mix. All the best Vs
  8. Don, when you way the AOA sensor cannot be incorrectly installed, it gives me pause. I've seen so many foolproof systems defeated, I have to think this would be just one more. That said, I know nothing about this particular part number or what connections have to be made (correctly) for it to work. We have a rich history of trouble from bent pins, excessive solder, a pin hole puncture, kink, overtorque, and a couple of dozen I know you could easily add - and all that is assuming that the correct part went into the correct spot - is there a left and right to these things, does the NG take the same part number, etc etc. Vs
  9. No. The computers will only work out what fits their model. If a condition is outside the range of assumptions of the programmer, as the MCAS failure demonstrates, the computers may generate inappropriate solutions or diagnose the situation as something else. When the aircraft is approaching an upset, there is no substitute for raw data and direct control. It may be comforting to suggest that this all goes away when the AP is engaged, but we have to remember that there are limitations on AP engagement. If the aircraft is this far out of trim, is it certain the AP would function? All IMO. Vs
  10. Regarding AOA and who has what feature. I find the press coverage interesting. Air Canada has a more comprehensive installation, yet the press articles start with 'Air Canada and Westjet' and downplay the role of the AOA indication. I have to wonder, if the situation was reversed, would we see, 'Air Canada lacks important safety component'? And nothing from Sunwing. Hmm. IMO the AOA indication's value depends a bit on the aircraft envelope. The Citation I flew a million years ago had it, and it was a straight wing aircraft. Far from being a distraction, I found it provided a great immediate reference in a number of situations. For the MAX, the AOA location just becomes one more scan item. The pilots I have spoken with about it have no issues and are generally happy it's there. Given what we now know about the link between AOA and unexpected aircraft behaviour, just having an 'AOA disagree' without an immediate visual indication of which AOA is saying what, that creates a period of confusion as to whether the failure is on the low side or the high. Finally, the AOA indication is not going to be a distraction during an MCAS firing. What it IS going to do is warn the pilots of an impending problem while they are still configured (flaps not yet retracted) so they can decide on a mitigation up front (leave the flaps out for a bit perhaps, so delay acceleration, get some altitude or stay configured and return, etc). AOA indications are a good thing. The customers who shelled out on their own to install them should get a credit from Boeing when the rest of the world gets them for free. Finally, as soon as Boeing and the regulators start rolling out the fix, the grounding should shift from total airspace bans to unmodified aircraft and crew. If we don't recognise investment in additional layers of safety, that investment will not continue, human nature being what it is. The reasons for this grounding are ample proof of that sad fact. All just my opinion. Vs
  11. I'm guessing the R&D delta would be relatively low. The remote drive by wire is already proven in settings like de-icing trucks, the navigation would actually be far easier than for city streets as the airport is defined, confined and controlled. You might need a LIDAR for surprises like wildlife but you might not need stuff like agile collision avoidance or pedestrian handling. Then there is the concept of 'driverless'. I'm thinking the thing is monitored with remote takeover possible 100% of the time. Vs
  12. I can see an application as a member of a 'snowpack', where the lead is live but they control an echelon of drones. Vs
  13. I think the public hysteria will die down once there is a fix. The alternative, not to go where they want, when they want, at the price they want, will be too unpalatable to serve as a long term option for the bulk of passengers. Regarding the conflict of interest of delegation and the predictable knot that the FAA common type rating game tied here, this hum has been growing louder decade after decade. But when judging the FAA, we should be careful of our own complacency. SMS is hardly a shining example of oversight north of the border. We may be seeing the worst case scenario in the B737MAX accidents. That said, La Megantic was every bit as catastrophic and we largely just carried on. A few regulatory changes but did our attitude toward delegation really get checked? Properly done, the worldwide grounding and eventual return to service of this fleet should be the start of several sweeping enquiries into how regulators meet their mandate, or fail to, along with how often the delegates give into the pressure of those who pay their salaries while they are supposedly acting on behalf of the regulator. There will either be a major restoration of focus, division of duty and competency in oversight, or we are going to be right back here, talking about something similar, before much longer. To say that would be sad would be insulting in its insufficiency. Vs
  14. Two thoughts: 1) I have not heard any official story disputing that the FO TOTAL time was 200 hours. Like so many I wonder if there is a correction coming to that figure. In the absence of same, Sully's perspective is more articulate than anything I can add; 2) To Blues' point, the cadet program has been running for some time. That said, I consider how long it takes in this business for bad policy to make it to an accident scene. I wonder if the intrinsic safety of this industry has resulted in new cadets having the benefit of low aircraft malfunction rates (and relatively minor events when they do occur) while they get their feet under them. This accident may be one of the few cases where a low time cadet had the misfortune of encountering a severe problem near the very beginning of their time on the line. So much that we don't yet know. Vs