Flydubai Flight 981 Crashes on Landing in Rostov-on-Don, Russia

[Evan]

Hmmm... I didn't know that.

So, I am in an IMC approach with one AP engaged (and AT too). I reach the minimums, I don't have the runway on sight, so I hit the GA button.
What exactly happens after that, assuming that I don't touch anything else?

My understanding (which can be wrong) is that the AT would go to TOGA power, that the FD roll mode would go to heading hold, and that the FD pitch mode would go to GA climb to the preselcted altitude. And... that the AP (that is still on) would have no choice but to follow the FD commands. Or does the single AP disconnects itself the moment you hit GA?

All correct except that the single autopilot WILL disengage and you will be hand-flying with A/T. To terminate TO/GA below 400ft RA you must switch off both FD's. Above 400ft RA you simply re-engage the autopilot in a selected pitch mode and the roll mode becomes HDG SEL.

Note: the other issue is power and pitch coupling. By using the AT and pushing the TO/GA buttons once, you will get a manageable reduced N1 sufficient for a 1000-2000fpm climb. Once the N1 has reached that reduced limit, you can push the TO/GA buttons a second time to get full TO/GA N1. This prevents underswung issues with sudden thrust. However, if you simply firewall the thrust levers you might get more than you bargained for in pitch, especially if your pitch trim is so inclined and your mind is fatigued. THAT is why procedure is so important here.

[Evan]

BTW: From AvHerald today:

On Mar 29th 2016 the MAK condemned all "leaked" information reported by Russian media as false and stated, that no information whatsoever has been leaked from the investigation. About one hour of CVR has been transcribed so far including the crew communication in the final stages of the flight. Mechanical reconstruction as well as preliminary analysis of the flight data recorder so far do not suggest any malfunction of the engines of the aircraft and no failures of aircraft systems or components, the aircraft had all necessary documentation and certificates of airworthiness, passed all required maintenance and was airworthy at the time of departure. The MAK is now undertaking mathematical modelling of the aircraft's flight trajectory in combination with the sounds available on the CVR. The identification of wreckage pieces and mechanical reconstruction of the aircraft continues.

[Black Ram]

Then again, the BEA had a similar reaction after leaked information about AF447 appeared on Le Figaro. You never know.

[3WE]

Hmmm... I didn't know that.

So, I am in an IMC approach with one AP engaged (and AT too). I reach the minimums, I don't have the runway on sight, so I hit the GA button.
What exactly happens after that, assuming that I don't touch anything else?

My understanding (which can be wrong) is that the AT would go to TOGA power, that the FD roll mode would go to heading hold, and that the FD pitch mode would go to GA climb to the preselcted altitude. And... that the AP (that is still on) would have no choice but to follow the FD commands. Or does the single AP disconnects itself the moment you hit GA?

Not picking on you AND this reply is not really "in context" but notice how you make no mention of "and then watch the instruments" in these statements...

...I think that when you do indeed push those buttons for hundreds upon hundreds of landings and "watching the instruments" is an unnecessary exercise time after time after time, that "watch the instruments" get's overly automatic and forgotten.

[TeeVee]

ok, so not wanting to sound like i relish the idea of providing pilots with yet another crutch, i will once again state that i am tempted to wish for an automated TOGA button, as in ONE BUTTON DOES IT ALL regardless of the state of the AP's. the point being that although nearly every GA is uneventful (i must have personally been in over 10 as a pax), when things get really shitty, to the point where pilots are overwhelmed and lives are at stake, they have that "get out the shit free" card/button.

key word here is tempted.

[Gabriel]

ok, so not wanting to sound like i relish the idea of providing pilots with yet another crutch, i will once again state that i am tempted to wish for an automated TOGA button, as in ONE BUTTON DOES IT ALL regardless of the state of the AP's. the point being that although nearly every GA is uneventful (i must have personally been in over 10 as a pax), when things get really shitty, to the point where pilots are overwhelmed and lives are at stake, they have that "get out the shit free" card/button.

key word here is tempted.

The "regardless of the state of the AP" part is very complicated. First of all, the AP doesn't decide what to do, it just moves the flights control to do what the FD told it to do. Second, there are all sort of altitude restrictions, speed restrictions, heading restrictions, etc restrictions in the GAs. The go around in instrument approaches, called "missing approach procedure", have a protected airspace so the pilot doesn't need to ask for a clearance when initiating the go around. On the other hand, there can be planes out of that protected airspace.

So, you are hand flying (AP and AT are off), you have nothing specific programmed in the FD, you hit GA, and the AP does what? And the AT does what? (climbing without adding a significant amount of fuel flow will not take you very far up).

Now, if you are in AP, I don't see why the AP (even a single one) cannot transition from approach to GA keeping the plane in AP. I am almost sure that many planes do just that. I don't know why the 737 doesn't, and it is a surprise for me.

[3WE]

Basically concur, Tee Vee. Go around is a rather critical and busy affair. A go around button shouldn't be too complicated nor a source of work, complication or confusion.

[Evan]

Now, if you are in AP, I don't see why the AP (even a single one) cannot transition from approach to GA keeping the plane in AP. I am almost sure that many planes do just that. I don't know why the 737 doesn't, and it is a surprise for me.

When you are in close proximity to the ground, i.e takeoff, approach, flare, autoland and go-around, Boeing wants the autopilot to be fault-passive for obvious reasons. That's why you need the dual AP for go-around.

Your description of autopilot is a bit analogue, perhaps from the MD-80? On the NG there are two FCC's that make up the AFDS and they obey the flight management computer via the MCP commands. They also position the FD bars. The autopilot is not following the FD, it is the same system - the Autopilot Flight Director System (AFDS).

To answer Teevee's question, the dual-autopilot TO/GA mode is engaged simply by pushing the TO/GA buttons once. With one push of one button you will get climb thrust and a 15° pitch command with the AP holding heading. You won't stall and you won't become disoriented. So yes, there is a essentially a magic button there. But in order for this to work you must be in a dual-autopilot APP mode prior to the go-around. Why a fatigued pilot making a challenging approach would not follow this procedure is a mystery to me... Perhaps one of the autopilots was MEL'd on this flight...?

[Gabriel]

When you are in close proximity to the ground, i.e takeoff, approach, flare, autoland and go-around, Boeing wants the autopilot to be fault-passive for obvious reasons. That's why you need the dual AP for go-around.

Sorry but I don't get it. If one single autopilot was good enough to fly the approach down to X ft AGL, I don't see why it would not be good enough to fly the go around from the same X ft AGL. Or in other words, if you can't relay on one AP to fly a go around from as low as X ft AGL, then you should not rely on it to fly the approach that low in the first place.

Or in yet other words, if an AP was happy to fly your approach (and it is still doing it), it should not self disengage when you hit GA.

[3WE]

Yes, flying down towards a very special, small, hard and unforgiving block of concrete versus flying up into big, wide fluffy air is generally much different in criticalness and 'skill' required.

[TeeVee]

The "regardless of the state of the AP" part is very complicated. First of all, the AP doesn't decide what to do, it just moves the flights control to do what the FD told it to do. Second, there are all sort of altitude restrictions, speed restrictions, heading restrictions, etc restrictions in the GAs. The go around in instrument approaches, called "missing approach procedure", have a protected airspace so the pilot doesn't need to ask for a clearance when initiating the go around. On the other hand, there can be planes out of that protected airspace.

So, you are hand flying (AP and AT are off), you have nothing specific programmed in the FD, you hit GA, and the AP does what? And the AT does what? (climbing without adding a significant amount of fuel flow will not take you very far up).

Now, if you are in AP, I don't see why the AP (even a single one) cannot transition from approach to GA keeping the plane in AP. I am almost sure that many planes do just that. I don't know why the 737 doesn't, and it is a surprise for me.

Let's remember that the aircraft we are talking about "know where they are." they all have GPS and should be accurate to within a few meters if not a few feet. my iphone gps is accurate to within feet even indoors, so if whatever boeing stuffed in isn't...

how difficult is it to have approach plates (seriously antiquated briefcase style navigating) programmed into the flight computers? we are talking about minuscule amounts of data here.

so plane is on approach to runway X at airport Y. HAL is tracking his location the entire time even if both AP's are disconnected cuz Johnny-fresh-ou-of-puppy-mill wants to show off and hand fly his shiny new 737NG in rough weather--near autoland type stuff. at about 150' johnny wisens up and admits he is out of his league so stabs the Magic TEEVEE TOGA button. HAL immediately does what HAL needs to do to keep his circuits from smashing into the concrete by commanding both AP's to ON, AT to ON, thrust @ XX%, pitch up to YY degrees etc etc etc. Based upon the missed approach procedures for specific locations, we are safe having HAL deal with this since there shouldn't be any other aircraft in the path. A few seconds later, HAL says, wake up Johnny, aircraft is safely at XXXX feet flying missed approach pattern for Turkeyville, Indiana.

best part of this is, the very same plane can autoland in total shyte weather based upon antiquated, yet functional and obviously accurate ILS beacons yet we don't trust it to do an automated go around.

[Evan]

Sorry but I don't get it. If one single autopilot was good enough to fly the approach down to X ft AGL, I don't see why it would not be good enough to fly the go around from the same X ft AGL. Or in other words, if you can't relay on one AP to fly a go around from as low as X ft AGL, then you should not rely on it to fly the approach that low in the first place.

Or in yet other words, if an AP was happy to fly your approach (and it is still doing it), it should not self disengage when you hit GA.

Really? In critical phase you want to rely on a single autoflight system prone to failure with no redundancy?

Let me give you an odd example of this: Turkish 1951. This is an odd example because they WERE in a dual channel approach mode BUT the system that was supposed to provide the cross-check redundancy was unreliable (Boeing knew about this and quietly changed the system after 2003). With the comparator system malfunctioning, the second autopilot was essentially asleep so, in effect, this is a rare example of an NG flying a critical phase autopilot mode (FLARE) on a single AP that is also malfunctioning: Essentially, the AP, behaving due to the aforementioned comparator failure as a single-channel, had an RA fault in FLARE mode and sent the A/T prematurely into RETARD mode. And, because the crew did not expect this and were not alert, down she went. WIth the current post-2003 retrofit, this could never happen because FLARE requires both AP's and the cross-check systems are now fully reliable. Nor could it happen in autoland or TO/GA.

You see? In a single-channel operation, a single failure (in this case a single radalt) can cause a very stealthy and dangerous situation whereby the autopilot is trying to crash the airplane. At altitude it is expected that the crew can recognize this and react in time, but down low, as we have seen, it's not something you can rely on.

Gabriel, what reason, aside from a failed or MEL'd AP, would a pilot have for not flying an ILS approach in approach mode with both autopilots? I just think, if they are both available on an ILS approach, the APP button should be pressed and both AP's should be selected in CMD. Why would you not do that?

BTW, this isn't as 3WE likes to imagine, an anti-flying skills complacent thing. Even with Otto on both channels and established in GS mode the autopilot WILL ignore stall warning and WILL stall while trying to hold the glideslope in windshear. If this happens the pilots MUST take action to avoid the stall.

[3WE]

Really? In critical phase you want to rely on a single autoflight system prone to failure with no redundancy?

You missed the point. Gabriel is saying that you can use ONE autopilot to fly an ILS, but need two for a go around?

This defies logic- A Chevrolet Category I ILS is a fairly PRECISE affair, while the vast majority of go arounds are Power up and fly away into the big, wide, open sky (at least significantly bigger and wider as compared to arriving at a fairly specific area 200 feet above the ground and close to the centerline.

[Evan]

You missed the point. Gabriel is saying that you can use ONE autopilot to fly an ILS, but need to for a go around?

This defies logic- A Chevrolet Category I ILS is a fairly PRECISE affair, while the vast majority of go arounds are Power up and fly away into the big, wide, open sky (at least significantly bigger and wider as compared to arriving at a fairly specific area 200 feet above the ground and close to the centerline.

What is critical are TRANSITIONAL phases of flight in ground proximity. You can fly an ILS approach in single channel autoflight but you can't FLARE, you can't autoland and you can't go-around. Accidents happen during these transitional moments from, for example, a steady glidepath to a 2000fpm climb. If the autoflight is doing that and something fails (see my post above), you have very little time to a) gather situational awareness and b) react correctly. Boeing is playing it safe. Why would anyone have a problem with that?

Moreover, answer the question I asked Gabriel: why wouldn't you engage APP and both autopilots on an ILS approach if they are both available?

[3WE]

No and sorry.

It is not that difficult!

I'll give you 15 seconds of very critical management of pitch and airspeed where regardless if it's one Otto or two Ottos or Boeng Bobby working the controls, you are riveted to the instruments (as you transition from an 800 fpm descent to the proverbial "positive rate")...

but then

It's generally keep the nose pointed 'properly' upward to the big open sky.

Guiding a 180 MPH airliner down to 200 or 100 or 50 ft AGL (or full autoland) and on the centerline is much more critical. (And again, regardless of how many Ottos or Bobby's are doing the flying, I want a human watching the needles too!)

To add full power and "gently but aggressively" transition to a climb attitude...high level of attention, but it's a fairly ordinary skill.

PS 1- Gabriel is saying you can do an ILS with one autopilot, correct...I hear his point- why in the hell is 1 ok for an ILS but you need 2 for a go-around?
PS 2- Is some of this irrelevant since you said auto land was not an option due to the crosswind (ok, you meant the gusty winds)