explain the "auto throttle" to me/us

[gums]

From the Asiana threads, I am not sure how the "auto throttle" really works, or even the intent.

If the thing is set to hold an airspeed and change the engine thrust to hold that airspeed, then sounds like what we USAF pilots usually flew. You know, point the nose and move the throttles to hold speed. The nasal radiators did it different. Hold an AoA that gave you best approach speed for weight and such, then move throttles to control rate of descent. We SLUF ( A-7D) pilots found that the Navy procedure was great, but we still did a slight flare just before touchdown as we were not trying to catch a wire on the deck of a pitchin/rolling boat.

The Asiana crew appears to have used the procedure/technique we USAF dweebs used - point the jet, and move throttles or let HAL move them.

I would appreciate some explanations and rationale for different implementations.

[Wizofoz]

The Auto throttle does different things dependent on the mode it is in and the phase of flight.

As a general rule, though, I would suggest that in Airline flying, your "Point the jet use thrust to control speed" is what is normally used on approach.

As an example, the most usual approach in an Airliner would be an ILS- if done with the automatics, the AP would use pitch to follow the Glide Path, Roll to follow the Localiser, and the A/T would be in SPD mode, adjusting thrust to maintain the selected speed.

There are modes when this is not true, however- for instance if wishing to make a flight-idle descent, Flight Level Change mode simply reduces the thrust to idle, then uses pitch to maintain selected speed.

A pertinent factor about THAT mode is that after a few seconds at idle, the A/T mode changes to "Hold", which means it is basically dis-engaged and in standby. This allows manual changes to thrust to be made if you wish to vary your ROD.

In the Asiana case, it SEEMS that what the crew did was manually use pitch and roll to follow the approach path, EXPECTING the A/T to manage the speed, but the A/T was in fact in "Hold", and thus not doing so.

Hope that helps somewhat!!

[Capn Bloggs]

Never understood why Nasals used the secondary effect of controls to fly approaches. :E

When engaged, the AT moves the throttles as required to try to achieve the speed.

Only when the flight guidance system mode is in "Open Descent" (Airbii)/"Flight Level CHange"/Real Boeing/"Level Change"(others) does the AT generally go to Idle/Standby: in these modes the pitch position is used to control the speed (ala Nasals). The trap in this mode is, if hand-flying and ignoring the Flight Director (which probably is saying fly down) by pulling up the nose, the speed will reduce but the AT won't react. If the speed gets too slow because Bloggs continues to pull/hold the nose up, any decent AT system will spring to life regardless of previous pilot selections and save the day.
Apparently the 777 doesn't do this.

[Wizofoz]

Only when the flight guidance system mode is in "Open Descent" (Airbii)/"Flight Level CHange"/Real Boeing/"Level Change"(others) does the AT generally go to Idle/Standby:

Also VNAV SPD in the Boeing, and it then reverts to "Hold"

The trap in this mode is, if hand-flying and ignoring the Flight Director (which probably is saying fly down) by pulling up the nose, the speed will reduce but the AT won't react.

Good chance the PFs F/D was off.

If the speed gets too slow because Bloggs continues to pull/hold the nose up, any decent AT system will spring to life regardless of previous pilot selections and save the day.
Apparently the 777 doesn't do this.

It will in any mode EXCEPT "Hold"- INCLUDING disengaged!

Yes, I think it's a shortcoming.

[Denti]

Interesting differences to the tiny boeing (aka 737). It reverts to ARM instead of HOLD and low speed will revert it to active, except below 27ft RA where it will revert to RETARD. THR HLD is only used during takeoff on that plane. But then, according to Capn Bloggs above it is not a "real" boeing as it uses Level Change and not Flight Level Change.

[Capn Bloggs]

But then, according to Capn Bloggs above it is not a "real" boeing as it uses Level Change and not Flight Level Change.
My profuse apologies, Denti! You do fly a "real" Boeing. :ok:

[Desert185]

When going slower than the normal Ref+5 that an airliner would do, ROD is more effectively controlled with power, which is what the Navy does. Even I transition to that technique in my 185 when the necessity for going slow into a short strip is required. However, when increasing speed from the backside is necessary, then power comes to the rescue. Pitch only isn't enough.

In normal operations with an autopilot, the A/P controls pitch/glideslope and the autothrottles (if equipped) control power/airspeed, and of course, a combination of pitch and power is a blend for maintaining speed and profile.

[gums]

Yeah, Desert, guess we were used to a higher AoA than the big jets. Our Viper used about 13 degrees AoA, so we were close to the area of reverse command WRT power.

Of course, we trimmed like crazy to get to and then hold the AoA, then began using the throttle for precise touchdown point and rate of descent.

I still have trouble with all the throttle modes and such due to "connections" with the other HAL - the autopilot. And that's where my questions come from, as I only flew one jet with an Otto-coupled ILS mode and we had to use the throttle manually. And you better have had the sucker trimmed for best approach speed/AoA before "coupling". Figure 180 knots IAS basic, then more for gas/loadout.

It also looks like there's a plethora of implementations depending on what heavy you're flying.

[TLB]

And that's where my questions come from, as I only flew one jet with an Otto-coupled ILS mode and we had to use the throttle manually. And you better have had the sucker trimmed for best approach speed/AoA before "coupling". Figure 180 knots IAS basic, then more for gas/loadout. Gums,

You must be referring to the Mighty Voodoo, which I had the great pleasure of flying for 12 years/2,000+ hrs.

As a bit of a sidebar, I have considerable difficulty with the current culture/attitude regarding automation in general and auto-throttle use in particular. Acknowledging that I have never flown with an A/T, I find it very scary how it would appear that some folks on the flight deck these days seem to have an overwhelming reliance on this piece of automation.

For example, it would appear to me that in both this Asiana accident and the Turkish Airlines Flight 1951 in Amsterdam, the flight deck crew (three pilots in both cases) were under the impression that the A/T was handling the throttles, when in fact it was not, for different reasons. Regardless, in both cases, these six pilots did not recognize that the IAS dropped 40 KIAS below Vref, resulting in … guess what … a stall !

The problem that I have with the culture/attitude I referred to above is because, in my opinion at least, many pilots in this culture will say: “well, the faulty RADALT disconnected the A/T … or whatever … so it was not my fault”.

Wrong !

It is, it has been, and it always will be the pilots responsibility to ensure that the aircraft flies within its aerodynamic parameters. If the automatics aren’t doing the job, then the guy who signed for the aircraft has to take over. It's his responsibility, his job; it's why he is the aircraft captain !

I acknowledge that I am clearly a dinosaur as far as today’s automatics are concerned. But I am a pilot and I firmly believe that all pilots must be capable of keeping their aircraft flying.

[gums]

Yep, actual Dash-1 was 175 plus some knots for fuel over 3,000 pounds, but what the hell. Only the 104 had similar speeds on approach, best I recall.

Only had about 500 hours in the jet before the "war" called me, and I remained an attack puke next 16 years.

We sure appreciated the Cannucks flying 200 miles north of us toward the North Pole, but from our Grand Forks' orbit north of Gimli we could still see Baffin Bay, heh heh.


I am not a dinsosaur steeped in "hand flying" all the time, and I flew two of the latest and greatest jets with advanced avionics and nav features that the airlines did not get for years.

But I still have a problem understanding exactly how that auto-throttle fits in when merged with the auto pilot modes. I am confused. And I can't get a sim ride to see how it all works.

The folks on the AF447 thread know me, and they know my opinions regarding FBW, so we can skip all that stuff. They also know my opinion about a HUD, and I think a good HUD would have helped a lot for the Asiana pilot.

[japandwell]

Recent article quoted FAA as saying auto throttle will adjust power to maintain speed. Boing aircraft, the thrust lever actually moves when AT steps in to add power. Airbus, the throttle remains fixed.
The pilot said he noted the throttle position was not moving, but he thought the AT was going to step in and fix the problem.
No link found. Read it.

[Capt Claret]

G'day Gums,

The venerable Douglas/Boeing 717, a DC9 on steroids, works thus:

Selecting Autoflight on the takeoff roll once symmetrical power increase is observed engages the Auto-throttles to the target takeoff power, be it REF power or flex/derate.

Passing the acceleration altitude entered into the FMS as part of the pre-departure procedures will see the take-off power reduce/increase to climb power, with the aircraft accelerating towards (usually) 250 kias. During this phase the AFS uses pitch to accelerate to or maintain 250 kias, and once through transition altitude to further increase to enroute climb speed. The Flight Mode Annunciator panel (FMA) will indicate SPEED on PITCH & T/O or CLIMB THRUST.

Once cruise level is reached the FMA will change to indicate SPEED (FMS or manually selected speed) on THRUST and LEVEL HOLD, and the auto throttle system will adjust power within the bounds of its capabilities to maintain the set speed.

When commencing a normal descent, the auto throttle system will for the most part continue to use thrust to manage speed, whereas pitch will manage the flight path. Should the aeroplane get higher than the computed flight path, the auto throttle will reduce power to idle, and may increase the IAS/MN to the maximum allowable minus a margin that is too small for comfort. On regaining profile the auto throttle will revert to SPEED on THRUST

A normally flown instrument approach or visual approach will see the SPEED on THRUST relationship remain, and in the flare the thrust will be reduced to idle, with reverse thrust being manually selected.

In any of the above modes, if the FMS detects the speed at Vmin - 5 kts, the auto throttle will advance the thrust, or if it had been turned off (but not broken) it will engage the auto throttle, and use a combination of thrust and pitch to maintain Vmin-5 and sacrifice altitude until the pilot intervenes and selects a faster speed.

In essence the 717 philosophy is to engage auto throttles during takeoff and leave them engaged until landing.

I think in my 8 years on type I've only had two occasions where the auto throttle system didn't work and both were a result of FADEC failures.

[Capn Bloggs]

speed with thrust is a much better, although less Boing/manly, way of describing the speed control mode, Clarrie... :)

[RetiredF4]

gums, tlb and all Fj- guys,
we had some kind of auto throttle as well, computed in our brain by reference to speed and attitude (present and desired) and implemented in our left elbow and hand.
Or did either of us need to do any kind of lengthy computing what kind of thrust setting would be suitable, aside from the first hours in the respective aircraft? How did we close formation takeoffs/ landings and WX penetration, how air refueling and AG bomb runs partly in single seat aircraft while navigating, comunicating and in bad days watching not to get shot down?

Now in the days of automation and magenta line training this ability to correlate speed and attitude to the thrust necessary has been lost, and a few (as i hope only a few) occupants of the front office ( i dare to name those pilots) even don't know anymore, what a AS indication is good for and what keeps an aircraft flying. Too many accidents happened that way.

[roulishollandais]

we had some kind of auto throttle as well, computed in our brain by reference to speed and attitude (present and desired) and implemented in our left elbow and handAdding eyes's scan it is what I call "Gesture algorithm".:D
Now in the days of automation and magenta line training this ability to correlate speed and attitude to the thrust necessary has been lost, and a few (as i hope only a few) occupants of the front office ( i dare to name those pilots) even don't know anymore, what a AS indication is good for and what keeps an aircraft flyNTSB hearings show they have no intention and are no more able to modify that :mad: misbehaviour, individually or in crew. They call it their culture.... The folks on the AF447 thread know me, and they know my opinions regarding FBW, so we can skip all that stuff. They also know my opinion about a HUD, and I think a good HUD would have helped a lot for the Asiana pilot.Designing his HUD, GILBERT KLOPFSTEIN wrote and showed that it was easier to be aware of the actual State of the Bird considered as a dynamic system and to control the path in one sight with correct speed, thrust, attitude.

[gums]

Thanks, Clarie.

Now for the bigger jets.

And is there an overall philosophy according to the manufacturer?

[LW20]

Yes there is a tendency regarding the use of automation in "airline flying".
Save money in selection and training of pilots.
It is easier( = cheaper) to tell somebody to let the autopilot and autothrust do all the work, than to train him and to keep him proficient in manual flying.

[gums]

I didn't want to hear that, LW.

I used otto a lot in my single-seaters, and even the family model I flew as a nugget. But it was simply a task management thing so I could pull out an approach plate for a strange field or figure out a new course or.....

My back seater in the VooDoo was never hesitant to ask me what the hell are you doing if I did something strange, heh heh. Same for my wingies in the SLUF and Viper.

[Jwscud]

Basic Boeing philosophy on the old types (737) - use AT with AP engaged. With AP disengaged, disconnect AT.

The automatics on the 737 are not top drawer though - the AT needs "help" in gusty conditions. The thrust levers move according to the AT demands.

The modes available for the 737 NG AT:

N1 - AT holds commanded N1 limit. Used in takeoff and climb, with aircraft pitching for speed

MCP SPD - AT holds target speed set on the MCP using thrust up to current N1 limit. Used in level flight, approach mode and in climb/descent when V/S is the active pitch mode

FMC SPD - AT holds target speed from the FMC - normally in cruise or in a path descent on a geometric descent path with VNAV PATH as the pitch mode

ARM - thrust levers static and able to be positioned manually. Normally idle thrust in descent with MCP SPD as the pitch mode (Level Change) Also provides very limited low speed protection.

GA - provides reduced thrust if the TOGA button is pressed once on a go around equivalent to around 2000fpm climb rate

It's a fairly simple system, with the main point being that if you are flying manually, you should be using manual thrust. I have never tried manual flight on approach with the AT in, and I imagine with the pitch couple it is fairly interesting.

[tdracer]

In the olden days (pre-FADEC), the autothrottles had a pretty important task in protecting engine ratings and keeping things like the 'climb' rating during the changing altitude/temperature during a climb.


With the advent of FADEC, that's no longer a significant issue - climb rating occurs at a constant throttle position, and it's pretty hard to have a significant overboost in Normal FADEC mode without really trying.


BTW, the autothrottle on all Boeing airplanes used to be more 'aggressive' in turbulence - it was intentionally slowed down for a number of reasons.

[gums]

Thanks Scud.

Not what I wanted to hear, but if the heavy folks can live with such an implentation ( or die with 200 SLF in the back), then seems their choice( the SLF don't vote).

I can understand some basic profile settings, like climb for optimum rate of climb or range when cruising, and descent to a specified atltitude, tho I don't like that one, and the Asiana crew witnessed that sub-mode of Otto and throttle otto).

My only experience with the climb and descent otto, held the speed or mach, and I set the throttle to whatever I wanted or needed.

I can also understand the jet adjusting the power once level to get the best cruise mach and such. Ditto for a climb profile, but don't know why otto would adjust the throttle(s) as the crew could just set the power to the basic setting from the manaul.

But seems to me that there are still a plethora of modes and sub-modes that are connected with the autopilot modes, and it gets confusing.

If the policy is to fly the USAF technique of point the jet and use throttle for speed, regardless of the optimum AoA for an approach, then I understand that. But the last thing I wanted was a system that was hard to understand depending upon a host of other systems that were supposed to "help" you.

Even if the whole profile was flown by HAL, then the faux pilots would have to monitor system operation and detect a problem or whatever. Why not just fly the jet yourself and take pride in nailing the mach for climb and cruise and setting power for descent to reach the initial approach fix at the right altitude and.....

[flyboyike]

Gums, if you don't mind my asking, what's an implentation?

[gums]

Sorry Flyboy, I mean "implementation", how a concept is implemented.

Start with the operational requirement, get some ideas from the players, refine the requirements, get some proposals, then decide to go with brand "x" or brand "y". Basic systens engineering and procurement stuff. Gone are the days that a company can roll out a plane and get some customers.

Bus and Boing seem to figure out what the "need" is, and propose something. If the major carriers don't seem interested, then they refine and improve what is already flying.

[flyboyike]

So...you're saying this is a bad thing?

[Capn Bloggs]

My only experience with the climb and descent otto, held the speed or mach, and I set the throttle to whatever I wanted or needed.
Different philosophy in airliners. The aim of climbing is to do it as quickly as possibly to get up into the thin, fuel-efficient air. So the throttles (ATS or not) go to full/climb power and the speed is controlled by the nose position.

but don't know why otto would adjust the throttle(s) as the crew could just set the power to the basic setting from the manaul.
For jets, the best situation is flying at a specified speed eg Long Range Cruise. So the power (ATS or otherwise) is used to control/maintain the speed. Apparently, turboprops use the opposite technique: level off then set cruise power and accept whatever speed you get. Claret will confirm: he has plenty of boat time. ;)

If the policy is to fly the USAF technique of point the jet and use throttle for speed, regardless of the optimum AoA for an approach
Approach speeds are determined to the knot; that gives the optimum AoA. Pitch for attitude and thrust for speed is just another way (IMO more logical) of flying at the correct AoA. After all, that's what the autopilot does on a coupled approach. Maybe when sitting on the back of the drag curve using power to control the descent worked OK; we didn't use that technique in our 190kt-approach land-based delta...

[FE Hoppy]

Auto throttles are very simple things and they all work pretty much the same way. Speed on thrust or speed on elevator depending on the selected vertical mode. The will also have a hold or clamp mode if they are used for take off, this is to prevent the AT system buggering up the take off and a retard mode that is triggered at some radio height over the threshold.

Nothing to it really.

[gums]

C'mon, Bloggs

The optimum AoA for approach, climb, range etc. is what it is. The speed is a result of your configuration at the AoA ( slotted flaps, leading edge devices, etc factored in).

The jet stalls at "x" AoA, and speed could be above or below the manual's number - think accelerated stall and such.

I did not appreciate the concept of the AoA "indexer" lights on the gunsight/HUD until flying the SLUF. Then, we had the actual AoA bracket next to our flight path marker in the HUD. Sheesh, how could it have been easier, with no flight directors or auto-anything? Our AoA was the real deal, and compensated for gross weight without us doing anything. Some configuration factors came into play, but the basic AoA didn't change much - figure a degree or so AoA.

We usually set a power of 95% or so for our wingies when climbing. Then we climbed at a mach or a generic speed while trimming for such. Sheesh. Easy. Upon level, got to the best mach and used whatever power we had to, duhhhh? Why is that so hard?

It would seem to me that basic throttle settings for climb, cruise and descent would be easy to know. For approach, if you need otto to help, then fine. but quit connecting the throttle to the AP modes. If you want to "point" and use throttle for speed, your choice.

[Rick777]

The advantage to modern auto flight systems is just like the cruise control in your car is that can operate very efficiently making very small corrections. The basic operating is very simple, but really understanding them is much more difficult. As shown by the Koreans --they could use but didn't really understand about the hold mode. The other problem is that you need to actually know how to fly when things don't go perfectly. Apparently the Koreans couldn't do that either. I flew the A 320 for a long time and always told new guys that the magistrate stuff works great so use it, but don't ever completely trust it. It is kind of like flying with a student--never let it put in a position that you can't recover from. Another problem the Koreans had and something they don't teach you in training.

[Capn Bloggs]

The optimum AoA for approach, climb, range etc. is what it is. The speed is a result of your configuration at the AoA ( slotted flaps, leading edge devices, etc factored in).

The jet stalls at "x" AoA, and speed could be above or below the manual's number - think accelerated stall and such.

Gums, you've lost me. For any configuration, there is only one speed that will give you a particular AoA. That is why Vref to the knot is used by airliners. Somebody decided many moons ago that speed would be a better "target" to use.

Airliners generally don't do accelerated stalls :eek: so the stalling speed is always the same for a particular configuration and in any case is calculated by the FMS (taking into account all sorts of things like C of G) and is displayed on the ASI by way of Vref, being the stall plus 30%.

We usually set a power of 95% or so for our wingies when climbing. Then we climbed at a mach or a generic speed while trimming for such. Sheesh. Easy. Upon level, got to the best mach and used whatever power we had to, duhhhh? Why is that so hard?
Who said it was hard? What you've described is exactly what happens in a jet airliner; climb at constant power using pitch to control the speed, then in the cruise, use power to stay on speed.

For approach, if you need otto to help, then fine. but quit connecting the throttle to the AP modes. If you want to "point" and use throttle for speed, your choice.
?? As has been pointed out already, having the autothrottle control the speed reduces workload. The autothrottle can be used with or without the AP being engaged. It is not "connected" to the AP modes. It does different things depending on what the AP is doing with the aircraft but that is generally reactionary eg AP pulls nose up to get back on GS, autothrottle pushes up power to keep speed on target.

Some types, like mine, recommend using the autothrottle all the time, AP in or out. And it does a far better job than I ever could. "pointing and using the throttle for speed" is simply flying without the AP or the autothrottle. Problem?

[Denti]

From his posts gums is addressing two very different things in my opinion. One is the use of automatics including autothrust and the other is basic airmanship.

Using automatics has improved safety considerably, however as we now see for a couple years, despite a record breaking low accident count, is the fact that pilots still need to be pilots and need basic airmanship. That said automatic flight systems are tools. Nothing more, nothing less. A professional pilot needs to know his automatics inside out as well as he needs to be able to fly manually if the need arises and of course has the ability to monitor what the aircraft and its system are doing. The latter one is actually the hardest task and human beings are not very good at monitoring,

Autothrust is very good at what it does, and over the long and incredibly boring hours of commercial flight, it is much better than any human being could ever be. However as any system it has its limitations, design criteria which it follows and different modes that work according to what state of flight they were designed to be used in. Using Level Change, or Flight Level Change, for a visual approach seems to be a rather odd use of autothrust mode in my opinion, certainly no mode i would ever use in the tiny boeing, however as i'm not rated on the huge twin i can't possibly comment if it is a normal use of AT mode there. In my outfit we would usually fly a visual in manual flight with the AT in arm (which provides low speed protection) and knowing that we have to set thrust manually.

[VNAV PATH]

If the speed gets too slow because Bloggs continues to pull/hold the nose up, any decent AT system will spring to life regardless of previous pilot selections and save the day.
Apparently the 777 doesn't do this.


It will in any mode EXCEPT "Hold"- INCLUDING disengaged!


Answering Wizofoz saying it will in any mode EXCEPT hold , including disengaged

It´s not true ...you seem to mix ARMED and DIDENGAGED/DISCONNECT functions

Even in HOLD mode , A/T will react , I agree lately , but it will react provided A/T arm switch on the MCP is armed which is always the case .

Precisely, when speed is approaching middle part of speed amber scale , your autothrottle becomes "awake" , Speed mode engages et your auto throttle is keeping speed on top of speed amber scale which is MMS minimum manoeuvring speed.

More info on PLI activation, caution air speed low and trim inihibits are available by your nearest retailer ..

[roulishollandais]

Gums, you've lost me. For any configuration, there is only one speed that will give you a particular AoA. That is why Vref to the knot is used by airliners. Somebody decided many moons ago that speed would be a better "target" to use.

Airliners generally don't do accelerated stalls so the stalling speed is always the same for a particular configuration and in any case is calculated by theFMS (taking into account allsortsof thingslikeC of G)and is displayed on the ASI by way of Vref, being the stall plus 30%.

NO NO NO! That is only true in steady flight. Stall is a transient situation.
See the PRANDTL basic curve : all the points are mesured at the same speed, but different AoA.
Speed is a bad indicator of stall. Only AoA is true
gums is true.

[galaxy flyer]

I can't understand the aversion to using AoA to control flight in the take-off, approach and landing phases in heavies, airlines, FAA-world. I used it in the T-38, the Citation (same indexer display) and the C-5 (no indexer, but 7 units for approach, from configuring to landing). Not very useful in cruise, I'll admit. An AoA indication was installed on our Bombardier planes, but NO flight-verified recommended indications for any operations. We were told to "let us know how it works and what approach indications are, the FAA won't certify it".

The wing flies on AoA, not airspeed.

[galaxy flyer]

When 4D gets here, I'm going to shooting range. :E. I didn't say airspeed Could be replaced, just that AoA can be better in some regimes. And, not subject to incorrect weight calculations, for example. A thousand hours in the A-10 and hardly ever used that Tweet airspeed indicator on approach.

[OK465]

A thousand hours in the A-10 and hardly ever used that Tweet airspeed indicator on approach.

That's 'cause you couldn't go as fast as a Tweet. :p

I agree with you entirely about the use of AOA....and you don't have that much time before heading to the shooting range. :}

edit: BTW 1000 hrs in the Hog doesn't cover a lot of mileage.

[galaxy flyer]

Well, not much mileage, but it was several years in C-5 before I flew a leg exceeding the 10.2 hour, Yenisheir to Lajes leg in Hawg.

Back to A/T, the bizjet systems work like the Boeings--they move. The modes are Thrust (idle, if descending, CLB, if climbing) or Speed, if the vertical FD mode selected is Vert Spd or on a VNAV PATH. We have the same "FLC Trap", that is, in THRUST mode in a descent, the throttle setting commanded will be IDLE until reaching an altitude or intercepting a VNAV PATH, when they switch to SPEED and fly the commanded speed by using the throttles. IF altitude is the runway and no path is selected, no power until they see a min speed about 5 KIAS above low speed cue.

[Dave Wilson]

I'm not a commercial pilot but having read this post with interest and being amazed at the plethora of modes that there are which all need learning, wouldn't it be a lot easier just to use manual control of the throttles? I mean, there are two of you...

[Capn Bloggs]

wouldn't it be a lot easier just to use manual control of the throttles?
In ten letters, no.

[gums]

Thanks GF and Okie. I am getting a clearer picture from the ex-lite folks than the steeped heavy folks.

Despite my basic views of auto-throttle, I can tellya that if trying to get absolute best range in the SLUF, we would gradually pull the throttle back using the TOT ( turbine outlet temp, not EGT). The deal was as TAS wnet up, we would pull back 3 degrees of temp at a time. I forget the increase in TAS we used. But once flew from McChord to The Beach unrefueled using four bags and step climbing like the heavies seem to do for long hauls. An auto throttle rule based on mach and altitude hold would have been nice. Seems Concorde was only heavy that let altitude increase to get the best performance. Ditto for SR-71.

My main concern is if the throttle moving or not, and then the modes where the thing isn't really doing anything and the pilot thinks the sucker is working, but ain't. So think Asiana. My buddy that flew B757 and then B747 said it was easy to tell if the thing was working, as the throttle moved. 'course, he was one that kept his right hand on the throttles.

My focus upon AoA is that for a given configuration, then it is a great cross check for the calculated speed. We lites didn't have a hundred thousand pounds or more of basic weight, so a 1,000 pounds of gas was significant. After a quick WAG and rules of thuimb from the flight manual, it was comforting to see the optimum AoA in the HUD agree with the calculation. From then, you only needed to glance at speed every few seconds, and the flare was also easier looking at the AoA next to the flight path marker.

Thanks to all so far, but I still have questions about implementations and company philosophy.

[galaxy flyer]

Short story, gums,

Landing on a beautiful day in Dallas area in a Global. Former schoolhouse IP is playing with FMS entering a " hand drawn" visual by copying the runway threshold and adding an distance/altitude final fix and cranking down the altitude selector to the field. Hand flying with A/T engaged. Because I was flying a visual pattern, I was a steeper than the defaulted 2.5 degree path and would never intercept that 2.5 degree path. As we rolled out on 2 mile final, hands on throttles, I noted speed slowing to approach expecting the throttles to start "waking" up to about 1200-1300 pph of fuel flow which they weren't doing. I clicked them off and noted THRUST in the HUD. It dawned on me what was going on. The A/T were in idle because we lacked a vertical constraint--altitude or path. Good debrief followed.

Now, I never fail to announce modes shown in the HUD or the mode annuciator.

The problem you, I and others who came out of the old generation is that we have thousands of hours of hand flying, due to the nature of the planes we flew. That experience isn't easily or, more to the point, economically, replicated today. The conversion from those planes to "magenta line" isn't always easy for types like us, but we can fallback on those previous hours of flying. Imagine never flying those hours and they take away the automatics, then add in the fact that you rarely saw throttles move.

[flyboyike]

Despite my basic views of auto-throttle, I can tellya that if trying to get absolute best range in the SLUF, we would gradually pull the throttle back using the TOT ( turbine outlet temp, not EGT).


Gums, I beg your forgiveness, because I'm not very smart. What does your "basic view of A/T"(which you admit yourself you don't entirely understand) have to do with the SLUF?

[gums]

@ Flyboy

Simple, we duplicated the AT function that Bloggs, et al describe for cruise. But we did it by using the available steam gauges. So an AT would have been nice on our longer missions.

Our TF-41 was the first fan for a single-motor jet in USAF, and it behaved differently than the pure turbojets the others used, although the Vaark had fans.

[AerocatS2A]

I'm not a commercial pilot but having read this post with interest and being amazed at the plethora of modes that there are which all need learning, wouldn't it be a lot easier just to use manual control of the throttles? I mean, there are two of you...
Well it's really not that complicated. It may seem complicated when you try and put it down in words and you do need to have an understanding of how the auto-flight systems work, but it's a piece of piss, and it is a nice tool to have. I wish all of our aircraft had it.

[Capt Claret]

The 717 is my only auto throttle system experience. It's so easy to use that the only down side that I can see is that one loses the ability to set power manually & intuitively. We're not encouraged, in fact actively discouraged from, turning the AT off and keeping the hand in. From the perspective of the 717 I can't see why it seems so hard.

[Capn Bloggs]

I clicked them off and noted THRUST in the HUD. It dawned on me what was going on. The A/T were in idle because we lacked a vertical constraint--altitude or path. Good debrief followed.
Including a suggestion to add an SOP for FMA change callouts! ;)

PS: Wouldn't "Thrust" indicate speed was being controlled by thrust, not pitch, as appears to the case in your example?

From the perspective of the 717 I can't see why it seems so hard.
Agreed. Gums, trust the people who actually use this stuff in their job (I assume, from your posts, that you don't). It has improved safety no-end and is p155 easy to operate. BUT, one must be ready (and able) to notice stuffups and to fly it manually! If you're not, you're Turkish/AF447 dead. Unfortunately, that is where the bosses of the industry are pushing us.

[Dave Wilson]

Well it's really not that complicated. It may seem complicated when you try and put it down in words and you do need to have an understanding of how the auto-flight systems work, but it's a piece of piss, and it is a nice tool to have. I wish all of our aircraft had it.

I take your point that it's easier to use than describe. I have an understanding of the systems being an ex avionics eng...:). I can understand using them in other phases of flight but looking at it personally I wouldn't want to let a machine control the speed on approach. I only fly GA so don't have to worry about having it on or not as there's not that choice to make. I just like to think I have some instant control over things when I'm near the hard bits.

As pax on commercial flights I'm always slightly apprehensive on approach as I know that the best of us can have a switch pigs. I just hope that someone on the deck is keeping a beady eye on the IAS.

[AerocatS2A]

I take your point that it's easier to use than describe. I have an understanding of the systems being an ex avionics eng.... I can understand using them in other phases of flight but looking at it personally I wouldn't want to let a machine control the speed on approach. I only fly GA so don't have to worry about having it on or not as there's not that choice to make. I just like to think I have some instant control over things when I'm near the hard bits.
Well we let the autopilot control pitch and roll on the approach. We fly with hands on yoke and power levers though so can always make instant corrections if required.

[Dave Wilson]

I'm not au fait with modern autothrottles (obviously!) but if you have the AT controlling the approach speed what happens if you command more thrust? Does it let you move the throttles or do the throttles move but when you take your hand of them they try and restabilise at the commanded speed? In otherwords if you need a handful of go and need to manouvre hard both hands say to avoid another aircraft will it still try and go back to the command speed?

[Denti]

Manouvering hard during a go-around? Shouldn't happen or ATC didn't do its job in the first place. If something gets in the way it is a go around which on my tiny boeing means i will press the TOGA buttons upon which the autopilot will fly the go around path (both laterally and vertically) and the AT will produce enough thrust for a low climb rate of 1500 to 2000fpm or full climb thrust if i click the buttons a second time. If already flying manually the same is gonna happen, except that i will get flight director guidance only with the same thrust settings (we use the ARM feature, otherwise thrust would have to be set manually).

[Jwscud]

Reading other contributors, it seems one big issue is "mixed operation" - manual flight with automatic thrust. Like Denti, I fly the baby Boing (738). It is either all manual flight or all automatic. We fly short haul with regular short legs so are in fairly recent hand-flying practice. I am still in the RHS and the 73 is the only airliner I have flown so bear that in mind when listening to my opinions.

When disconnecting one, you generally disconnect the other, though I have flown occasionally with the AT inop but used the autopilot (RVSM requirement). Unlike Denti's company, we do not use the ARM mode in manual flight (that is a debate involving plenty of religious schisms in itself!) so for a go-around in manual flight one just stretches out the thrust arm, sets a fixed thrust level and sticks both hands on the control column. When manually flying the 73 one is very aware not only of the speed but the thrust set - even if the speed is good, a glance at the N1 will tell you if you need to add or reduce thrust in short order before you get any observable trend.

The difference is in the Airbus/777 where it appears the SOP is AT use through touchdown, which I can see could lead to a lack of awareness of actual thrust, and losing it I'm your scan while simply controlling the flight path.

[flyboyike]

I fly approached A/P off A/T on all the time. Works peachy.

[Jwscud]

In what type if I may ask? FBW or conventional controls?

[Dave Wilson]

Thanks for the replies, most interesting. When I did my IMC rating and was doing NDB holds and approaches, (if you've ever flown those in a light single in actual bad weather and crosswind you'll know they are interesting...) my instructors day job was 747 pilot. I said to him in the gaps where I actually had the capacity to speak 'What's this like in a big jet then?' 'Oh I just press a button' he said. Git.

[galaxy flyer]

Bloggs,

Yes, THRUST mode is speed on pitch, power is either idle or CLB, depending vertical direction. We do call out the FD modes, but not being an airline, not obsessive about it, just when the mode shown is not expected.

[flyboyike]

E-170/175. FBW, except for ailerons.

[gums]

Thanks, Okie, a good point about engine failure for a twin or even a four-motor plane.

I recall the DC-8 training flight at MSY back in 1967 or so during a "simulated" two engine approach. What would an AT do if you got a little slow?

I also like Okie's observation that you fly years with the AT, but then when airmanship counts, you can't or should not use the AT.

I have to fall back and lurk, now, and let the heavy folks contribute. but before I go....

We lost two folks in the A-37 during single-engine go-arounds( not practice, but battle danage or basic failure). The big motors caused the plane to act more like a "conventional" twin versus "centerline" thrust. One motor put out 50% more than BOTH motors on the T-37!! So even with plenty of power available, you had better get the ruddder in early and not cram the throttle forward. Otherwise, you began a roll and could not recover unless you eased forward and got the yaw under control. At high AoA, the thing acted like a swept wing jet, and roll-due-to-yaw was about the same.

@ Bloggs....... My perspective on flying AoA developed when I started in the SLUF ( A-7D). Being a Navy design, our approach was the slowest you could fly depending on weight with gear and flaps down. it was "draggy". I soon found that you had better get the power in early if pulling up a bit for glide path or to maintain the AoA you were supposed to use. I doubt if an AT would have helped much, but maybe it would have. My other jets were less sensitive to AoA and I flew the basic power for speed, and used AoA to confirm the manual's calculated speed. I would have liked the AT for cruise to optimize mach, but it wasn't a big deal to retard power a bit to maintain optimum mach.

and so I return to the lurk mode.

[tdracer]

but if you have the AT controlling the approach speed what happens if you command more thrust?


The way Boeing A/T works, throttle position always equates to thrust command. There are friction 'brakes' the connect the throttle levers to the autothrottle drive - if you don't like what the A/T is doing or want to override for any reason, it takes ~2.5 lbs. force at the knob to make the brake slip and move the throttle independent of the A/T (i.e. ~5 lbs. total for a twin or ~10 lbs. for a 747-400/-8).


Now, once you override the A/T, unless you disconnect the A/T (button on the thrust lever) the A/T will continue to try to drive the throttle so you'd need to continue holding the thrust lever.


This is pretty much common across the Puget Sound built Boeing aircraft.


Clear enough?

[Capn Bloggs]

Yes, THRUST mode is speed on pitch, power is either idle or CLB, depending vertical direction.
That makes sense. Must be Canadian! In a real aeroplane that would be PITCH mode.

if you have the AT controlling the approach speed what happens if you command more thrust? Does it let you move the throttles or do the throttles move but when you take your hand of them they try and restabilise at the commanded speed? In otherwords if you need a handful of go and need to manouvre hard both hands say to avoid another aircraft will it still try and go back to the command speed?
The speed, obviously, will not reduce because the autothrottle is holding it there, like the cruise control on your car. You don't put your foot on the accelerator when you start going up a hill, do you?

Why you'd want to slam on the power/go a lot faster to avoid another aeroplane is also a bit of a mystery. In any case, as soon as you started pulling (or pushing) in your dogfight, the AT would change the power to maintain the speed.

And yes, if you really need to override the AT, you can do so; just push or pull the throttles as you want. As soon as you let them go, the AT will set the power to achieve the speed target. And you can easily disconnect the AT if it goes ape on you.

Reading other contributors, it seems one big issue is "mixed operation" - manual flight with automatic thrust. Like Denti, I fly the baby Boing (738). It is either all manual flight or all automatic. We fly short haul with regular short legs so are in fairly recent hand-flying practice. I am still in the RHS and the 73 is the only airliner I have flown so bear that in mind when listening to my opinions.
It is becoming more apparent to me that the 737 is the only airliner where it is recommended to disconnect both, and that seems to be because of the pitch-power coupling. There is absolutely no problem flying around with the AP out and AT in in other types (in mine, recommended), provided you monitor the speed; in fact it is a damn-sight easier to do visual manoeuvring handflying with the AT in than out.

What struck me was in the event of a single-engine approach it was prohibited (not just discouraged) to use the A/T system. (Don't know if same applies to the 717.)
No it doesn't.

[Dave Wilson]

Why you'd want to slam on the power/go a lot faster to avoid another aeroplane is also a bit of a mystery.

Yes I see your point in a big jet that has plenty of reserve power and a large speed range. I keep relating it to flying SEP's, my bad.

[galaxy flyer]

Bloggs

Well, PTCH is vertical FD/AP mode, THRUST an autothrottle mode associated with FLC FD/AP vertical mode. Not sure, but not very different from Seattle ideas.

[roulishollandais]

Something we pilots love is the fact that we never live two times the same flight. Had anybody here another experience ?

Automation & systems (what I call "butterfly") at the contrary work only with something that physicists call models, who are math algorithms. Math algorithm mimicks reality, but like some sodas mimick whisky, it is not whisky, it is not the reality. The pilot is mandatory to adapt the model to the reality and use safely the best usable mode to do the real flight.

The NTSB Dec 11. 2013 enquiry shows that Asiana SOPs and pilots trust only in math algorithms not very well adapted, and ignoring some situations like the loss of the glide !

That airline, these pilots have no ability to adapt their real flight to the infinite situations of flight always different, always new.

Butterfly can only do some very specified tasks.

[EMIT]

Hello Gums, please return from lurk mode.

To answer your original question, I apply the old adage, to try to explain it in such a way, that your granma would understand it. Following is the way I explained it to my son when he was in flightschool.




AUTOFLIGHT

A summary for the subject assignment Autoflight.

In this assignment, a lot of terms are used, that may cause confusion if they are not properly explained: autopilot, flight management, autothrottle, autothrust, flight guidance, flight control computor, flight control panel, flight control unit, etcetera, etcetera.

An autopilot is a simple apparatus, that can somewhat fly an airplane.
An aircraft is controlled through the use of elevator, ailerons, the rudder and thrust. Furthermore there are (leading and trailing edge) flaps and speedbrakes.

Autopilots normally provide only control with the elevator and ailerons, they have a pitch channel and a roll channel. In exceptional cases they may also provide yaw control with the use of the rudder.
The control of the gas (thrust / jets or power / props) is managed by the autothrottle (or autothrust), nomenclature is more a matter of taste of the manufacturer. There is a certain relation between autothrottle and autopilot functions, but that can probably not be called real cooperation.

The flaps (and slats), speedbrakes and landing gear are never controlled by an autopilot, all configuration changes are made manually by the pilot.


AUTOPILOT

Basically an autopilot performs only some very simple functions:

Attitude hold - the attitude is maintained (pitch and/or roll)

Steering towards a certain value -

Pitch/ maintaining an altitude
a speed
a rate of climb or descent

Roll/ maintaining a heading (Heading Hold)

steering towards a heading (Heading Select)

Furthermore there are complicated modes whereby steering is based on the deviation of a radio signal, for instance pitch for following the ILS Glideslope and roll for following the ILS Localizer. Also the final phase of the autoland function is complicated – signals from the radio altimeter are used to flare the aircraft and accomplish an acceptable touchdown. On the runway nosewheel steering is integrated to stay on the centerline of the runway.

A factor that can complicate the picture, is the description of what happens at the moment that the autopilot is engaged: that is not necessarily during a static situation, it can also be during a dynamic situation.

Let’s say you select Heading Hold during a turn – during the rollout of course the heading will change a little bit. Should the autopilot now turn back to the heading that existed at the moment of engagement, or should it continue on the heading that exists at the moment of wings level (which could be defined as reaching a bank angle of less than 5 degrees)? That sort of “submodes” of course is described in the documentation.

For a mode such as Heading Hold, it is not necessary to set a value anywhere. Of course, a source of information is needed (for instance the Inertial reference System).

For a mode such as Heading Select of course it is necessary as pilot, to set the desired heading. That is accomplished with a knob on a panel that is usually located near the windscreen (within reach). The name of that panel is again a matter of taste of the manufacturer – Mode Control Panel (MCP) or Flight Control Unit (FCU). It is also possible to let the desired heading be determined by the navigation system. The autopilot is then “controlled” by the Flight Management Computor, or the Flight Guidance System, or whatever name they have given to the equipment. The mode will then have a name like NAV (Navigation) or LNAV (Lateral Navigation).

The pitch mode will normally work in conjunction with the autothrottle. Note specifically that I do not say that they cooperate – they work each in splendid isolation, but their functions are selected in such a way, that there is a logical relation.

The gascontrol can operate in a thrust mode or in speed mode.
In thrust mode, a certain level of thrust is maintained (e.g. take-off thrust, but idle thrust is also possible).
In speed mode, thrust is varied as needed to maintain a certain speed.

The pitch control can vary the pitch attitude to maintain a certain altitude (or a specific rate of climb or descent, or even an ILS glidesope, in other words, the vertical value), or it can maintain a certain speed (that is an horizontal value).

The inter relation now is as follows: when the pitch control steers towards the vertical value, then the autothrottle takes care of the speed.

When the autothrottle maintains a certain thrust, then the pitch control will take care of the speed.

In that way, altitude changes are taken care of: when you are flying at a certain altitude (pitch in altitude control and autothrottle in speed mode) and you want to climb, then autothrust goes to thrust mode and increases to climb thrust. Simultaneously, pitch mode switches to speed mode. The increased amount of thrust will want to accelerate the aircraft. Pitch control will react by pulling up the nose, executing its task to maintain speed constant. As a result, aircraft will climb.
When approaching the new desired altitude, the functions are swapped again: pitch will maintain the altitude and autothrottle must maintain speed constant. Because pitch will have to decrease attitude in order to maintain altitude, speed will increase when thrust remains at climb thrust. So, autothrust will reduce thrust in reaction to the level off by pitch control.

Of course you will read about “altitude capture modes”, those are temporary modes for the transition between the level change mode and level flight. The autopilot will calculate a nice transition between those two phases and tries to fly that as smoothly as possible, otherwise you get rough movements and sick passengers.

The mode names again depend on fashion: Altitude capture is annunciated by one as ALT CAP, by the other as ALT*

The setting of speed can be done by the pilot, with a knob on the glareshield panel (MCP or FCU), but can also be delegated to the Flight Management System. That sytem can maintain pre-programmed speed restrictions in Standard Instrument Departures (SID’s), or the standard limit of 250 kts below 10.000 ft. During the climb, economic climb speed, depending on the entered cost index; at altitude, the desired cruise speed, based on cost index and actual wind conditions, etcetera.
The name of the pitch mode again depends on the fantasy of the manufacturer – VNAV (Vertical Navigation), CRZ (Cruise), or PROFILE, you name it.

For descent the operation is as during the climb, only then of course, the autothrottle will choose idle thrust.

There are also somewhat more complicated level change modes – for relatively small altitude changes it is possible that the autothrottle will go to a sort of half gas value, this in order to prevent extreme thrust changes (jet engines suffer most from large temperature changes of the hot components).
Boeing for instance has the Flight Level Change mode (FLCH), where the thrust computer calculates approximately what thrust is needed to reach the new altitude in 2 minutes. If it is for a climb, then of course for a large altitude differential you will run into the climb thrust limit; if it is for a descent, then for a large altitude differential you will reach idle thrust. In case of large altitude differences, of course you will need more than 2 minutes, but in case of small altitude changes (1.000 or 2.000 ft), you will achieve that the engine life is spared and the flight movements are smoother.

For the descent there also is a sort of PROFILE mode: the descent is then flown in principle with idle thrust, but programmed altitude and/or speed restrictions in the arrival route will then be respected.
In that way, it is possible that on certain stretches, the autothrottle will increase thrust above idle, when the “desired” segment is too flat for an idle descent at the desired speed.
Complicated? For instance, when approaching from Germany to Amsterdam, waypoint NORKU (on the border) is restricted to BELOW FL280, speed 280 – 300 kts. Later on, at the TMA boundary, BELOW FL100, ABOVE FL070, speed 250 kts. At ILS interception point NOT BELOW 2.000 ft.
It is also possible that a segment is so steep that, with idle descent, maintaining the path leads to an increase in speed. It is possible that the system than advises with a message “DRAG REQUIRED”, or it may even anticipate the problem with a message “TOO STEEP PATH AHEAD”. What you then do as a pilot is up to you - perhaps you have the bigger picture that everything will nicely settle without any fuss, perhaps those messages open up your eyes that action is necessary, anyway, as stated earlier, speedbrakes are not under the authority of the autopilot.

Note that all the modes that have been mentioned, are indicated on the Primary Flight Display, just above the Attitude Indication in the so called Flight Mode Annunciation (FMA), green letters, every change highlighted by a box drawn around the change for some 10 seconds.

Some snags are possible for the unwary. Mostly those snags are in the combination of manual flight and autothrottle, but not all.

The autopilot calculates what it would do, when in control of the aircraft. With the A/P in command, it does as it calculates and as long as all systems are serviceable, A/P and A/T do a nice job of flying the aircraft, if need be, from shortly after take-off all the way to rollout after landing.
When the A/T is tits up (case, almost stall of Thomson at Bournemouth), or when it is OK by itself, but fooled by another system input (case, crash of Turkish at Amsterdam), then you will see that the A/P happily maintains ILS Glideslope, with nobody taking care of the speed.
When all systems are OK, but the pilot does not check that he has selected the correct mode, then you may see the aircraft happily tracking down the ILS at ever increasing speeds, rather than starting the Go Around, when the pilot has increased the thrust manually, but failed to trigger the Go Around mode and failed to notice the Flight Mode Annunciation that still is in LOC G/S !!! (multiple occurrences of Air France at Paris De Gaulle with anything from A-320 to B-777.

When the A/P is not in command, its calculations can be shown as output of the Flight Director – if you follow the pitch and roll steering commands of the FD, then you will follow the path that the A/P would have flown.
Remember, the division of tasks is the same as described for the A/P modes – A/P and A/T swap roles, but they work in splendid isolation. If you do not follow FD commands at a time that A/T is in a thrust mode, actually nobody is taking care of the speed !!!

A/T may have a bottom function to kick in regardless when angle of attack reaches a threshold value. This function may surprise pilots and also, the pitchup effect may exceed A/P authority if the A/P had trimmed to a very aft setting in the attempt to maintain G/S at a very low speed (case, Thomson at Bournemouth, even though thrust selection there was associated with Go Around).
The just mentioned A/T protection feature may also be defeated by the A/T being in THR HOLD mode – a situation that may be associated with FLCH mode: after the A/T has set the calculated thrust value, it disconnects or goes dormant to allow the pilot to set a different amount of thrust without having to constantly fight the A/T.
Note that THR HOLD is annunciated in the FMA !! This gotcha got the Asiana crew.

Bottom line
– take note of what the aircraft is telling you
- monitor what the aircraft is actually doing (e.g. speed)
- take action if you don’t like what is happening

With regards gums, to your question about use of AoA (indicators) in commercial big jets – here is a reference to an excellent article on that in the Boeing AERO magazine, edition 2000 quarter 4, find it via link
AERO (http://www.boeing.com/commercial/aeromagazine/articles/2013_q1/archive.html)

As the edition is already quite old, the text and pictures are not anymore collated, but it still is well worth the effort to retrieve and read it all.

With regards to your questions about use of A/T in engine out situations – depends on make and model and also on what options companies have been willing to buy into. Sometimes engine out means manual thrust only certified, sometimes A/T and Cat 3a ILS to autoland is still certified.

Use of rudder in engine out case – same deal. Some aircraft provide yaw control with rudder always, some rely on manual rudder until multiple autopilots are engaged for a coupled approach.

Reaction of aircraft also depends on whether FBW or not – if engine out causes yaw, then roll coupling will occur in non FBW system, but counter aileron (and skidding flight) is result in FBW system.

Hope this will clear up matters for you a bit, just post if any questions remain.
Check six.

Edit - only some layout items

[flyboyike]

Holy MCDU, AirRabbit has a brother!

[Jwscud]

Interested to learn that the 737 is one of the few medium aircraft that recommends manual thrust in manual flight. Strikes me as no fun flying with the AT engaged!

There is more food for thought on the autothrust complacency in another Air France approach to stall (http://avherald.com/h?article=46d16a49&opt=0) on Avherald.

This one obviously not just to do with autothrust (10° NU in landing config :ooh:) but another one to add to the discussion.

[Capn Bloggs]

the pilot monitoring later provided testimony that he was monitoring the alignment with the runway.
Like moths to the light, they all look at the runway... :ouch:

I don't like the term complacency. That crew were not complacent; they were out of their depth.

Gums had better not read that report; he'll say it confirms we're all nuts saying what a wonderful system the autothrottle is! :eek: :}

[Jwscud]

I posted this during discussion on the autothrottle thread on Tech Log, but deserves a wider audience:

Avherald - Air France A320 approach to stall (http://avherald.com/h?article=46d16a49&opt=0)

I don't fly the Airbus so the stuff on mode manipulation is lost on me slightly, but 10° NU pitch in the landing config is pretty scary :eek:

Again, with an AT supposedly engaged, nobody was looking at the speed!

[gonebutnotforgotten]

Yes, not nice, but I thought the most interesting bit in the report might be this (end of para 3.4):

Lors de ce dernier virage, la PF a donné un ordre à cabrer pendant dix secondes en contradiction avec les ordres des FD. Le facteur de charge a augmenté ainsi que la vitesse du seuil de la protection ALPHA FLOOR. La vitesse a chuté en dessous de VLS jusqu’au déclenchement de la protection ALPHA FLOOR.
Les pilotes indiquent qu’ils pensaient que l’A/THR ajusterait la poussée pour maintenir la vitesse. L’action à cabrer de la PF sans intervention du PNF montre que l’équipage n’a pas identifié les risques associés au non-suivi des FD en mode OPEN DESCENT

Which roughly translates to:

During the final turn, the PF applied a pitch up command for 10 seconds, opposite to the FD indications, The g increased as well as the Alpha Floor Threshold speed. The speed fell below VLS until Alpha Floor Protection was triggered.

The pilots said that they thought that the A/THR would adjust thrust to maintain speed. The pitch up command from the PF, without intervention from the PNF, showed that the crew did not identify the risks associated with not following the FD in OPEN DESCENT.

I would go further, the rearward heave on the side stick showed that the PF simply hadn't a clue about how the C* control law worked in pitch, and that she thought she was still flying a conventional aircraft aircraft like a 737. She ALSO didn't understand the concept of thrust versus speed modes of the A/THR, but it is hard to know which is more egregious.

Later on the report says:

L’enquête a montré une méconnaissance du fonctionnement de l’A/THR et de l’importance du suivi des FD en mode OPEN DESCENT. La même incompréhension des automatismes se retrouve dans l’événement survenu cinq jours plus tard sur le F-GKXO.

The investigation has shown a lack of knowledge of the A/THR function and the importance of following the FD in OPEN DESCENT. The same lack of understanding is seen in another event 5 days later on [another aircraft].

With respect, it shows a lot more, just as the investigation into AF447 showed a lack of knowledge that went far beyond the stall warning system, basic instrument flying for a start. But the world, FAA, EASA, ICATEE et al, is reacting to the bits the BEA noticed, not the ones they missed.

[Chris Scott]

The moral is: on the A320 NEVER disobey the FD pitch bar in OP DES mode, particularly if you are relying on A/THR to control speed (it won't, because it will be in IDLE mode).

When you no longer want to obey the pitch bar, turn BOTH FDs off, which will (or should...) change the A/THR into SPD mode.

We learned that lesson over 25 years ago...

:ugh::ugh::ugh:

[captplaystation]

What a :mad: of an approach & go-around.

It seems that AF ( with the longest history of any A320 operator if we include the ex Air Inter crews) & this particular Capt (who had "only" 9800hrs on type ) still haven't grasped the modes/logic/idiosyncrocities of the Bus.

Am I alone in finding that concept slightly disturbing, particularly whenever I am forced to clamber in the back of one to (hopefully) be conveyed from home to base.

[Chris Scott]

Quote from captplaystation (my emphasis):

It seems that AF ( with the longest history of any A320 operator if we include the ex Air Inter crews) & this particular Capt (who had "only" 9800hrs on type ) still haven't grasped the modes/logic/idiosyncrocities of the Bus.

This mistake rapidly became a classic no-no by the latter part of 1988 in my airline. The best spin one might be able put on this incident is that the low-hours-on-type co-pilot/PF forgot his recent training, and the captain was so distracted (for reasons unknown) that he failed to notice the pitch bar disappearing downwards, and failed to monitor the speed. (In OP DES mode, with A/THR consequently in IDLE mode, only the elevator can control the speed.)

I'm a little surprised that the speed got down to Valpha-floor, however. After the Bangalore accident, the FMGS logic was modified to switch automatically from OP DES mode to VS mode when the IAS fell much below VLS. (can't remember the figure right now). When the FMGS switches to VS mode, the A/THR mode changes from IDLE to SPD.

You got one thing badly wrong, though. The joint launch-customers for the A320 were AF and BR (British Caledonian... remember?). Air Inter was third in the line. BR became BA on 1/4/88, the day our first A320 (G-BUSB) was delivered. BA's accident-free operation (we bought 10) may have got less publicity than the others. See the Habsheim (http://www.pprune.org/tech-log/528034-habsheim.html#post8159637) thread?

[Winnerhofer]

AF and Airbus are a lethal mix ideologically and technologically.
In fact, if there had been a plebiscite by AF Unions, they would have voted to be an all-Boeing fleet hands-down.

[kick the tires]

Shaking my head at how the conduct of a crew on a national flag carrier can result in this.......

Report: Air France A320 at Tel Aviv on Apr 3rd 2012, approach to stall on turning final results in Alpha Floor and flaps overspeed (http://avherald.com/h?article=46d16a49&opt=0)

Hmmmmm

[galaxy flyer]

Puts paid to the notion that Koreans, for unique cultural reasons, can't fly.

[Lonewolf_50]

The pilot flying decided to go around but did not call out the go-around. The pilot flying moved the throttle levers into the TOGA detent and applied nose up inputs, the pilot monitoring applied nose down inputs for about 2 seconds (dual input). At that point Alpha Floor protection activated applying TOGA thrust and TOGA Lock,
Am I corect in believing that this all happened in Normal Law?
The pilot flying stabilized the aircraft, positioned for a second approach and landed safely.
Good. Go Around on a bad approach, come back, get her back on the ground.

[Torque Tonight]

Why is the PM applying control inputs contrary to the PF's inputs? Why is the PM applying control inputs at all? Do they not state 'I/you have control'? Forgotten some of the basics and past lessons? Similar stuff was going on in the stall non-recovery of AF447.

[boofhead]

Re Puts Paid (GF):

What notion; that they can't fly?

[galaxy flyer]

Boofhead

Spend some time over at the Asiana thread. Lots of comments that Korean (French?) culture makes them poor at CRM, ability to handle large aircraft.

[McBruce]

Pull up into a stall or push into a recovery... Airbus saves the day.

[Herod]

A First Officer with 27,500 hours? Something odd there.

[claychristman]

Maybe he's an 80,000+

[Winnerhofer]

Les français sont souvent arrogants.
The French are often arrogant.
Des pilotes français se sont crus injustement très forts ..
Some French pilots wrongly considered themselves as being TopGuns.
Généraliser leur incompétence est stupide!
To generalise their incompetence is stupid.
L'erreur relaté sur le Tel-Aviv a été décrite sur toutes les compagnies mondiales sur tous les avions mais plus sur les Airbus (problème du mini-manche).
The incident regarding Tel-Aviv has happened to all carriers on all aircraft but afflicts Airbus more because of the problematic S/S.

[NordicMan]

I think the F/O is 27 years old with 500hrs on type... The french did it again... does not surprise me:D

[Lonewolf_50]

Herr Winnerhoffer
Auf Englisch, bitte. ;)

Here is what I gather from your post. My French is nearly non existent.

The French are arrogant.
French pilots are good (at something I didn't quite parse). Generalization about incompetence is stupid.
The problem at Tel Aviv has to do with companies, and Airbus machines. (I am sure I lost something in that)
The forums in the internet are at a low level.

We certainly agree on that last part. :ok:

Do you think that it's time to invade through Sedan, yet again, and set them straight Herr Winnerhofer? :} :E

Dear Mr NordicMan:
Let us perhaps praise our French friends for their most excellent protection freatures in the Airbus, which seem to have helped the pilots avoid a mess, and thus allow them another chance after that unsettling Go Around event.

[Permafrost_ATPL]

More appalling monitoring from the captain than appalling CRM. If you don't follow the flight directors, turn them of. Understandable from the 200 hours on type FO, unless he had previous Airbus experience.

[Capn Bloggs]

The moral is: on the A320 NEVER disobey the FD pitch bar in OP DES mode, particularly if you are relying on A/THR to control speed (it won't, because it will be in IDLE mode).

On any aeroplane when in a similar FLCH/Level Change/Speed with Pitch mode...

[ettore]

@Lonewolf 50

Wengen is not in Germany. It's in Switzerland. But true : Swiss-Germans are still more pedantic as Germans used to be invasive... :ugh:

Back to the topic : looks as if the computer rightly corrected the "500-hours-on-that-type" FP misbehaviour. Do I get it right ? :8

[srobarts]

I think the F/O is 27 years old with 500hrs on type... The french did it again... does not surprise me
As I read it in the linked page, the F/O has 500hrs total and 200hrs on type.

[gonebutnotforgotten]

Quite right, but what the Tel Aviv AF incident shows is that there are some people flying A320s who still think they have to apply rear 'stick' in a turn, as they would have done in a conventional C152 or Boeing 737…. you don't, the stick is in effect a flight path command, if you want to continuously increase the flight path angle, then keep pulling, otherwise, one small input and leave it mostly to itself.

[gasbag1]

Another classic case of Automation helmet fire. No smoking hole so in the end the automation did work. However it is poor monitoring by the PM and the Capt. not taking control at a earlier point in the approach, especially given the low experience level of the F/O.

And it is interesting that a visual approach is described as a "indiscriminate" approach? TLV has used this procedure for some time now and flying a visual to the runway should be a relatively easy procedure with the usual good visibility and daylight hours for this flight.

[TLB]

I, and others, have posted this before, so apologies to those who have already seen it.

It is long - 25 mins - and it is dated - 16 years - but in my simple fighter pilot mind, should be required viewing by anyone flying with automatics.

Children of the Magenta on Vimeo

[Bpalmer]

Am I corect in believing that this all happened in Normal Law?

Alpha Floor only functions in Normal Law. So, yes.

[ATC Watcher]

Just read the full BEA report (in French only at the moment) . It is a bit more complicated that 2 pilots botching an APP. (but it always is )
The second similar incident that occurred 5 days later is also briefly analysed,
The report also mention that AF had received 5 previous ASR on the RNAV Visual APP in TLV prior the 2 incidents.

main points :
The RNAV Visual procedure is unique to TLV and not similar to what is routinely done elesewhere ,especially in USA
This is the only such APP in the AF A320 network.
This perticular visual APP was not included in the SIMs at time incidents .
ATC instruct crews to follow that procedure whereas the actual procedure is "to be on request by pilots"

How ATC is giving those RNAV APP and how they are designed are being investigated.

but also :
The non clear understanding on how A/THR automation works , especially in OPEN DESCENT mode,led the crew to believe that the ATHR would maintain speed .
(De plus, la compréhension insuffisante du fonctionnement de l’A/THR et de
l’importance du suivi des FD en mode OPEN DESCENT a laissé penser à l’équipage que l’A/THR assurerait le maintien de la vitesse.)
In both incidents the BEA indicates that PNF and PF were not monitoring speed .:rolleyes:
No not only a 777 training issue ..

Yes the PF had 500h TT and 200 on type. I suspect one of the MPLs , probably not a CPL ( my remark )

[kick the tires]

This perticular visual APP was not included in the SIMs at time incidents .

Maybe not, however the following most certainly would be:

How to SPEAK to the other pilot about the state of your/their approach planning.

That when flying visual approaches, ie manual flying, the correct mode is TRK/FPA, FD's off.

How to correctly Go Around.

How PM should take over control: I have control, NOT dual input without pressing the sidestick takeover button.

How to read the FMA's - its one of the basic principals of flying the Airbus.

ALPHA FLOOR - one has to seriously mishandle the aircraft to achieve this. When demonstrating it in the sim, it takes a looonnnngggg time and some gross mishandling to get there.

MPL's - if I have one of these chaps/chapess's in my RHS I am at a heightened sense of monitoring throughout the whole flight. They have NO experience and shouldn't be expected to cope with such an approach without mentoring and guidance. Some are excellent people, some are gung-ho, I know it all types who are more dangerous than they realise.

What the F was the Captain doing??

[A and C]

Two issues seem to be at play in this thread the first is easy to deal with, the second is shrouded in cultural issues that are mostly individual opinion rather than hard fact.

There seems to be a problem with the Airbus machine/ human interface, the aircraft is clearly a very good flying machine but it has become so good that it gives pilots an attitude of followership, when it does something unexpected the usual reaction from the crew is to go heads down and start tapping away on the FMC......... Not to disconnect ALL the automatics and revert to old fashioned manual flying. My second flying lesson was all about Attiude & Power = Performance, perhaps some professional pilots are getting too far away from the basics ?

The French pilot attitude and as some people see it arrogance is unique but not universal, I spent some time based in France working with French cabin crew, they at first appered very distant and it was clear that there was a big authority gradient across the flight deck door that did not help communication. After a while we broke down this authority gradient barrer, it became clear that MOST French pilots do have a very ridged veiw of their place in the system and the place of the cabin crew. From my cultural background I do not see this as helpfull from a flight safety point of veiw and the cabin crew expressed the opinion that as a group of pilots we were much easier to work with.

In twenty five years on the flight deck the only person that I have felt it nessesary to report to the management was a French FO who clearly had swallowed the arrogant sky god attitude whole and uncooked, he was very rude to the cabin crew and when I questioned a clearance he told me that I was wrong and he was correct, it took three requests to check the clearance and then a direct order to get him to check with ATC ! He had I fact made an error and had not understood the clearance........... In the next four hours of flight he said nothing about the incident and after the flight left the Crewroom in a way so as to avoid the de-brief.

As he had walked out of the Crewroom before the de-brief I had no option but to report the matter to my fleet boss...................... Who was French and in CRM terms the polar opposite of the FO.

From what I have seen in aviation good CRM is alive and well in Scandinavia, Northern Europe and the English speaking world but those nations who insist on not speaking the ICAO standard language in professional aviation do for the same cultural reasons find it difficult to accept the concept of CRM.

[F-16GUY]

Where did the Air France approach to stall into Tel-Aviv thread go?:confused:

[captplaystation]

I'll save the Mods some work (as an early Xmas treat :rolleyes: )

Twas put back into here


http://www.pprune.org/tech-log/529731-explain-auto-throttle-me-us-5.html

[vilas]

Chris

The moral is: on the A320 NEVER disobey the FD pitch bar in OP DES mode, particularly if you are relying on A/THR to control speed (it won't, because it will be in IDLE mode)."
"After the Bangalore accident, the FMGS logic was modified to switch automatically from OP DES mode to VS mode when the IAS fell much below VLS. (can't remember the figure right now). When the FMGS switches to VS mode, the A/THR mode changes from IDLE to SPD."

Isn't that basic? Open des or des means only pitch will maintain speed. If you are manual and you ignore FDs and drop speed at Vls-2 FDs will go off and managed descent speed will change to select speed and ATHR will change to speed mode to capture that speed. No Chris FDs don't change to VS mode only ATHR changes to speed.

[roulishollandais]

In consequence SEC and FADEC ar not independant. The global shematic show them independant.