Originally Posted by
GroundedDinosaur
Would it work, or am I completely insane?
In the movie "Flight" Denzel Washington rolls a plane inverted that is stuck in a dive.
In the ET302 accident, the pilots turned the trim motor back on because they were trying to relieve back pressure, and the manual trim was stiff. Would rolling a 737-MAX inverted and relaxing the column have the plane gain altitude, buying the pilots more time to work the trim wheel manually, maybe even while the plane was inverted, with relaxed elevator forces, or not? I"m sure Boeing isn't considering this, to include in their flight manuals, and you wouldn't win any applause from the passengers, but, would it work? Would you be able to roll inverted, quickly enough, and would then relaxing back pressure, and even pushing forward on the controls, gain altitude?
OK, finally have a few minutes to hopefully answer this intriguing question. First caveat: I have not seen the movie as I assumed that it would be a hack description of an impossible event. That said I have seen the trailer umpteen times.
I'm was going to break this down into three scenarios but only one is really worth discussing. Scenario 1 is one where the trim has reached an unmanageable state, but the PF has still been able to hold the nose on or above the horizon. Scenario 2 is where the trim has become unmanageable and the nose is passing vertically downwards through the horizon. Scenario 3 is where the nose is significantly below the horizon. For all scenarios I'm using an arbitrary 5000' AGL as the starting point.
Scenario 1:
This is by far the most likely scenario to succeed. If the pilots recognized they were in deep with the trim pegged and unmoveable,
before they allow the nose to pass through the horizon then it could possibly be recoverable.
1. Immediately begin an aileron roll by putting full aileron deflection.
2. As the airplane rolls towards 90 degrees the nose begins to drop. Anticipate this by retarding power and try to hold the nose on the horizon with top rudder. (Congratulations you just made 200 people puke...) If the nose goes below the horizon you aren't going to bring it back with the rudder, but even then you might be OK.
3. Airspeed will be increasing and hopefully so will roll rate. As the airplane passes through 90 degrees it is likely going to be increasing AS very quickly and the nose will move more quickly towards the vertical. Here power should be at flight idle and PF should firmly begin feeding in forward stick. The heading is going to change wildly due to dishing the roll, but that's the least of your worries now.
4. Here is where you are either going to save the day or fail like the others did. At the moment you went to negative G the fuel ports in the tanks were uncovered, meaning you only have any engine thrust for as long as the fuel remaining in the lines lasts. I have no idea how long, but probably 10 to 30 seconds at most.
YOU MUST now get the nose not only above the horizon, but well above it- in order to give yourself enough time to wind back the trim and roll the airplane upright before you have once again become a lawn dart. You do this by pushing hard enough to hold a 2G or so constant. As speed bleeds off you will have to push harder to maintain this constant level of G loading.
5. As you pass through the horizon again you will need to restore power to the trim circuits by hitting the cutouts and then trimming via the column switch before switching the cutouts back off. While you are doing that you need to be rolling with full aileron deflection (and perhaps one engine at 100% and the other at idle, I need to think about that one- also it is likely that at this point you have no engines, so probably moot point) until you have passed through 90 degrees of bank, at which point you also start puling very aggressively to again keep the nose from dropping any further than necessary.
Scenario 2 and 3 are simply not possible due to overspeed and running out of altitude before the pilots can arrest the descent and convert to an ascent.
Thoughts: I know that seems like a lot to process in a very short period of time, but I can tell you straight up that it is not a complicated sequence at all. Just one figure in an Unlimited routing can read like this: Pull to a vertical upline, 1 1/4 outside snap roll, 1/2 aileron roll (opposite), hammerhead, 1 3/4 inside snap on the downline. And there are up to ~16 figures in a sequence. So it is definitely possible for a qualified and capable pilot to perform the maneuver I described, but only if the pilot has been properly trained and (ideally) has flown the maneuver in real life to get an idea of how daunting the G forces will be. Is this maneuver going to save a 737 one day when the trim runs amok?? I highly doubt it. But with a horizontal trim tab that can be locked into position well within the flight envelope it is probably worth exploring what your options are if it ever does lock up and try to stick you into the ground nose first.
Cheers!!
dce