Clean at altitude, the B737 has a gentle stall behaviour, easily within FAR25.203 criteria. Adding power is as noted almost irrelevant at high altitude. The most notable characteristic is a low frequency moderate vertical acceleration at the flight station, from aerodynamic buffet on the tail.
At low to mid altitudes, the effect of thrust is more significant, and will reduce nose down elevator authority for a fixed trim condition. At the low to mid altitudes, if conducted dirty, the stall buffet is pronounced, with moderate to heavy vertical acceleration felt at the flight deck. The aircraft meets 25.203 again, but you can expect reasonably sharp rolloff if the stall is accelerated. Any mis rigging of the slats will result in a rolloff with autoslat extension as well.
The stalls at low to high altitude, clean through to landing configuration are obvious with good control response available, with the caveat that thrust couple can compromise the fixed trim pitch authority. While the B737 has a speed trim system, with it working, the stick force per g remains positive through the flight regime.
Any test or flight resulting in aerodynamic stall requires an inspection per the AMM, which is heavy on the empennage, for good reasons. The buffet is pronounced. Having investigated other types that have had deep buffet boundary excursions, resulting in flow conditions that have literally torn carbon fibre outer elevators in half, buffet events should be taken seriously with post flight inspections.
Mach buffet on the B737 is different to the stall buffet, but is probably not going to be recognised as such without cross check of the instruments. The onset on a B737 at 1.0G is very gentle, and increases amplitude as speed increases. The frequency of Mach buffet is higher than the stall buffet. In both cases, any unloading of the aircraft will reduce the buffet amplitude.
The most recent changes to the FCOM for all Boeing and Airbus aircraft are rational, and reflect the necessity to ensuring the AOA is reduced. The discussion on roll, rudder etc continues to approach areas of structural integrity concerns. The use of bank might well be applicable when you are flying a Folland Gnat with a jammed full aircraft nose up stabilator, but otherwise, it doesn't take much bank to get the nose coming down in the real world. Sim training ends up with examples of extreme flight angles being exhibited which will be pretty interesting in a dark night, when the reason for the upset is possibly due to instrument failure or vertigo etc. Goldilocks rule.
Unless you have ripped off tail feathers, then every aircraft known to man (other than the F101) will look after itself if the damn pilot stops mussin' with it. The aircraft will recover unless the pilot prohibits that by his actions, which we as a group have routinely done. AF429 had full back stick on for almost the entirety of its descent, there is no Cessna, Pitts, Cub, Boeing or Airbus that will survive that level of mishandling. Other than the aforementioned 101, even T tails will recover; post the magic B727 zoom climb in the eastern US from having pitot heat turned off, Boeing conducted a vigorous deep stall series and could not get the plane to "dig in", or "pitch up" (again, not so for the F101), and unless mishandled further, the plane recovered when left to its own devices.
For Airbus drivers, the control laws which are pretty neat when they are working proper like (as all computers dooooooooo.....) you are inherently set up for a pitch issue on reversion, like Perpignan, the stab trim is outside of your immediate experience of use, until the moment when you absolutely need it to control thrust pitch couple, and get the nose down so that you can collect your thoughts. The addition of the note on the ECAM of use THS trim is nice, but probably not within the cognitive capture of a dynamic upset event, where you are guaranteed to have lots of stimuli happening promptly. If THS is used, the plane is a happy camper, alternatively, if the thrust coupling is not disturbed, the plane will exhibit normal speed stability (unless you have uncommanded flight control inputs through bad sensors etc.... which is not detected as a sensor failure, almost hardly ever happens... :| ).
P.S. If you try hard enough, a B737 will autorotate... data showing that had been found in the smoking hole in the ground before today. >180 degrees a second is not impressive for a Pitts but it is pretty impressive for Ma and Pa in 35EF. AOA management will make for happier endings.
The B737 is not a bad aircraft, it wants to fly if the pilots don't mess with it too much.
In respect to AMS, going into the hover, OGE in any jet aircraft, with insufficient altitude to recover is going to end badly. The failure of the LH LRRA ws insidious, as the immediate result was not apparent to the PF and certainly the PM and the other people not looking at the energy state of the aircraft. The more emphasis management has on the flight crew acting as observers and monitors of the system, the more frequent the failure mode of out of the loop control will occur. Humans are poor at monitoring systems, that is the thing that computers do well. Humans are capable of identifying patterns that are otherwise unprogrammed, but not always. The slam dunk approach that was flown at AMS places the aircraft and crew in a position that care is needed to ensure that the performance of the aircraft as a system is monitored effectively, the systems need to act correctly and in a timely manner to achieve the outcome. In the end, the failure of the ATS to maintain a target airspeed as it had already gone to idle for the landing was not identified, and the energy loss on pitching to the glideslope and the associated speed bleed was not recognised. It was a high workload event, and the crew were unable to deal with the cognitive demand on the day, and stuff happened. Expectancy of the system behaviour being nominal becomes a reinforced trait of our flight crew due to the overall success that occurs on almost all occasions, except when it doesn't. Healthy skepticism is hard to maintain for a complete career.
Last edited by fdr; 21st Feb 2018 at 22:57.