Hello
Lyman;
In re the autopilot disconnect and, "
It was difficult. " (
post #1124)
No, it was not. And a disconnect is most certainly not like "hovering a Harrier".
An autopilot disconnect is a non-event.
If the airplane is descending/ascending slightly when the disconnect occurs, a gentle nudge on the stick (millimeters in terms of movement of the top of the stick) brings the airplane back within the expected requirement, which here is maintaining a cruise altitude.
A disconnect simply is unimportant to a pilot - and absolutely should be a non-event. One takes over, commands the airplane and makes it do what you want, returns it to what you were doing before the disconnect, and when available, re-engages the autoflight system. It's what we do.
The terms "Select" and "Managed" have specific meaning for Airbus pilots. They refer to an autoflight mode where control of the aircraft is either through the MCP (Mode Control Panel - autopilot panel) or the FMGC.
When the AP disconnects and there is a rate of climb or descent occuring, (including a small deviation such as occurred here), the vertical speed window will display VS (as opposed to other modes such as FPA or just dashes in "managed" mode). In other words, the display defaults to VS and will show what the rate was at disconnection but isn't a "command"...it's just information at that stage.
In terms of response, no pilot is going to slavishly follow an FD command to "descend at 5000fpm" because a flight director says so. He is instead going to "look through" the temporary FD "command" and get his airplane gently back to cruise or whatever it was doing prior to the disconnect and get on with the drills/checklists. No big thing. Really.
Hello,
Machinbird;
I do appreciate your comments and the fact that you present such a different view of 'the wing' than I have as a transport pilot - it is very engaging and well worth the discussion, thank you.
Re, "
The natural place to be using AOA is on approach."
I like knowing and using AoA. I used to interrogate the ACMS Alpha Parameter functions on the ACARS units all the time and keep the AoA displayed down on the pedestal especially during heavy turbulence. So it can be done (though it isn't taught!), and likely easily with software and pixels (rather, raster scan!).
So I do not argue against an AoA presentation to the pilots...I like it and agree that training on it would be straightforward in terms of the mechanics of learning and applying the information. I am not personally arguing against it but I'm recognizing some of the impediments to making the change and the likelihood of such change in the face of certification regs, training/standards/checking and the like. Airline budgets are thinner than they ever were and "safety as a business case" is not an atypical approach, it is THE way it is done. Agree or not, cost and cost control are enormous factors in daily operations.
The one argument which I think may be convincing is in knowing that one was stalled but the counter-argument is, the blaring "Stall, Stall" and loud warning chirp didn't get their attention...would AoA have? What else does a pilot need to tell them their aircraft is stalled?
The industry has been largely successful without AoA so the argument that AoA would have "saved" AF447 vice other standard handling procedures (not stalling, pushing the nose down once stalled), is not convincing. It wouldn't have saved Colgan, it may have saved the Airborne Express DC8, it may have saved the FedEx ATR72 at Lubbock and (IIRC) a B727 where the pitot heat was turned off, but in the millions and millions of hours flown in all types, lack of AoA has not been an issue until AF447.
So the argument must demonstrate that an AoA indication would have made a difference to the outcome,
for this crew and while it may have, we just don't know. The captain may have noticed from his vantage point and called out "push down!"...we don't know. I agree that one accident prevented makes such change highly desirable but again, what shall we argue next? I absolutely know through data that there are some things that can be done right now that would prevent CFIT and overrun accidents in the approach and landing phase but short of exorting the stabilized approach, very little is left up to technology and presented information.
But we could have an electronic "energy-status bar"...showing the potential landing distance, even on contaminated runways as a digital presentation relative to the aircraft's energy level on the approach.
Now that kind of presentation would be used thousands and thousands of times because that is the number of non-stabilized approaches that are occurring in airlines' FOQA data.
The argument for AoA is not "natural" but is nevertheless a good one...the more info the better, but it comes with much more than just putting in the guage and both manufacturers and airlines are going to look at the cost.
It is the way this business is done, much to my (and most others who work in it) frustrations.
My comment about "how quickly things unfold" is an observation on the amount of time it took to lose control. Time is always "relative to perception and familiarity". When a pilot is highly trained, highly experienced and very familiar with his/her airplane, the flow of even huge amounts of information and lots of events flow much more slowly, perceptually, because the mind anticipates much more effectively and easily, (depending upon other factors such as distraction, fatigue) than if one is relatively inexperienced in such circumstances.
In terms of this loss of control, while it unfolded literally over a period of about 40 seconds, oddly that is tons of time to do something, but it is not a lot of time for assessment, discussion, action.
This is a really important point: Most things that happen in an aircraft that cause trouble or an accident take a few seconds and one has a bit longer for response. This is what training (and training and training) is for - to reduce the time needed to assess accurately and respond. The response to the UAS was instantaneous without, in my view, good reason to do so and without the requisite crew coordination. One simply never does that in a transport aircraft, period, unless it is a TCAS, GPWS warning. The SOP is, first establish control of the flight path, (in other words, don't give up a stable flight path for one that is unpredictable, uncertain, unannounced and unplanned); once control is assurred, call for the drills and/or checklists, all the while keeping a very close eye on the aircraft.
By the time the aircraft had stalled, they had backed themselves into such a corner of confusion that there were no breadcrumbs to get back to stable flight because they completely lost situational awareness even though the nose was pointed up, the stick was full back and the altimeter was unwinding at about a thousand feet every three seconds.
PJ2