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Uplinker
13th Aug 2015, 10:57
Thought I might start a new thread just to explore the subject of moving and non moving thrust levers, as touched on by some other threads.

It would be interesting to know which of us like and dislike each system, and for those who dislike non moving levers, did you fly with moving ones before?

For those now flying Airbus but who have used moving levers before; what do you miss? Is it the feedback of the autothrust in your hand or is it the ease with which adjustments can be made if the autothrust gets it wrong?

I personally never flew an autothrust aircraft until I qualified on Airbus FBW, so I don't have any moving thrust lever experience.*



*apart from BAe146, but that doesn't really count !

ASRAAM
13th Aug 2015, 13:41
Flown both, now on the bus where they don't move. Prefer ones that move.
I presume not moving ones are quite a lot cheaper to build hence the attraction for manufacturers.

Times when I would like moving ones are as follows.

In the cruise, usually fairly high when a bit of turbulence/ wind change runs you close to an over speed and the jet is way to slow to respond.

On the approach in a 319 when its holding 10kts fast due to " auto thrust misbehaviour".

Mainly though for those few moments approaching the flare when the speed washes off and the auto thrust does nothing.

Moving levers should not really be used for SA though, just because the levers have motored all the way forward does not mean the engines are producing that power. The BA 777 that dropped short at LHR would be an example.

Amadis of Gaul
13th Aug 2015, 14:37
I was on the E170/175 prior to the 320. I remember playing with the thrust levers quite a bit on approaches, the FMA showed OVRD in the Thrust window more often than not. Can't say I miss it, the 'Bus system seems to work fine so far.

Goldenrivett
13th Aug 2015, 15:16
I prefer moving thrust levers and agree with the findings of the 1991 poll of BA Airbus rated pilots:

"BA concludes that from a Flight Operations perspective a future system should consider providing movement between the idle and climb power positions, whilst retaining the A320 thrust setting and engagement “detents” technique."
by Steve Last & Martin Alder.
British Airways Airbus A320 Pilots' Autothrust Survey (http://papers.sae.org/912225/)

If this had been the case, then we wouldn't be having the discussion:
flying below VAPP - What to do? (http://www.pprune.org/tech-log/565790-flying-below-vapp-what-do.html) with over 4,800 PPrune observers wondering the same. (as of Aug 13)

vapilot2004
13th Aug 2015, 20:37
For SA, movement is certainly useful, despite the example of the (exceedingly rare*) failure of both RR powerplants on BA038. On approach, TL movement can provide clues of misconfiguration or near-windshear conditions.

The thing about 'old-fashioned' driven levers I appreciate the most however, is I can, without a doubt, move the thrust levers and know (*see above) I will get an engine response and not have to spend time second-guessing the automation mode. During low altitude operations this can be critically important.

In defence of the Airbus non-moving philosophy, as they say, training, training, training. In critical situations, if you perform the memory items correctly, the design is in no way an impediment to the safe operation of the aircraft. Turns out that is the case with just about everything flying today.

RAT 5
13th Aug 2015, 22:18
In defence of the Airbus non-moving philosophy, as they say, training, training, training.

This topic has been touched on in other threads. Now there is a direct question. My thoughts, following the quote above, is that I'm not sure training for its own sake should be opposite to what is natural instinct when under a moment of pressure & stress. Human natural instincts will generally take over when the brain is scrambled. Don't fight it, embrace it.
Non-AB; when on a manual approach you set a thrust for the job in hand. If slowing down through the flaps you have a low power setting. When final configuration is achieved you set a sensible thrust setting and make fine adjustments to maintain speed. Even on an LVO ILS you 'follow through' the a/c including the A/T. It is reassuring to feel the a/c doing its proper job. When you can not 'feel' the a/c responding to circumstances you have to increase your scan rate to include the thrust meters. Is it a sensible setting?? Is this increased work load what you really want; is it a good idea? Does it lead to a false trust and a blasé attitude that all will be OK. Feel is a great sense that pilots use at all times. This is now removed and transferred to sight. That requires more brain power & concentration; IMHO. Is that an improvement?
On take off and CLB non-moving thrust levers is no problem. In CRZ it is no problem as long as you monitor speed and the N1%; in descent they are mostly at idle; you should monitor speed and N%. All these phases are usually a monitoring phase. However, on approach and G/A, following the a/c and what it's doing is very important. So why not, when the a/c goes into 'APP Mode" design the T/L's to move? It would be a doddle and put the pilot back into the loop where they should be. A visual approach, manually flown, is not a time to be a monitor. If you fly manually and control the T/L's yourself, that's normal. If you fly an A/P ILS with A/T why not make the A/T's move and keep the piloting sense alive? It would be so easy, technically. Is there a will? There is certainly a way.

Why are line pilots not more involved with the evolution of technology and the feedback after a coupe of years of introduction? Sometimes I feel we are forced into adjusting our behaviour, not always naturally, to suit the ideas of the technocrats. I'm not a dinosaur, but a round peg fits a round-ish hole better than a square one.

Smilin_Ed
15th Aug 2015, 01:08
Some months back a young pilot's post asked for advice on intercepting the ILS glideslope from above. What I wanted to say was, "Ensure that the plane is trimmed for the proper approach speed. Ease back on the power to increase the rate of descent while holding speed. Just above the glideslope, ease the power forward and establish the correct rate of descent."

I realized that would not answer his question so I didn't answer. What he wanted was what buttons to push. He didn't want to know how to fly the airplane. He wanted a rote procedure. Aircraft developers talk about reducing pilot workload but there are certain things that are integral to flying and one is feeling the airplane respond to throttle movement.

I'm reminded of AF447. They didn't know how to fly an airplane either. :ugh:

vilas
15th Aug 2015, 02:58
Smilin_Ed
May be the pilot who asked knew how to do it manually but wanted to know how to do it with automation. What's wrong with that? Good, what you wanted to say but didn't, because that wouldn't have helped him. A good pilot must also have thorough knowledge of automation as well.

vapilot2004
15th Aug 2015, 05:24
"Ensure that the plane is trimmed for the proper approach speed. Ease back on the power to increase the rate of descent while holding speed. Just above the glideslope, ease the power forward and establish the correct rate of descent."

Works a treat, nearly every time.

stilton
15th Aug 2015, 06:22
No one on the AB 'side' wants to hear this but it's simple.


There is NO advantage to non moving, non backdriven autothrottles / thrust whatever.


For the Pilots that is, same with the non linked sidesticks.


It mat save a few bucks in maintenance but it's a crappy idea that has worked brilliantly to isolate Pilots from what is going on with their aircraft.

kbrockman
15th Aug 2015, 10:02
Has there ever been an accident where the non moving throttles where a substantial contributing factor, honest question, I don't recall one but there might be those that do ?

What I do know is that moving throttles are by no means an assurance for better piloting per se.
Just look at the TK 737 crash at AMS where there where no less than 3 pilots in the cockpit, the speed decreased too much, throttles iddled but nobody seemed to notice until it was too late anyway.

Also not 100% sure but ASIANA214 also had pilots thinking the AT was still connected, it was not but the non moving throttles seemed to make both pilots non the wiser.

stilton
15th Aug 2015, 10:59
I can accept that you can get used to non moving autothrottles
what I've never heard from an Airbus fan is the advantage of this design for the Pilots.


Just one..

Chris Scott
15th Aug 2015, 11:29
Quote from kbrockman:
"Has there ever been an accident where the non-moving throttles were a substantial contributing factor, honest question, I don't recall one but there might be those that do ?"

If there has, it's very hard to establish beyond doubt.

During final approach using A/THR on an aeroplane with "driven" thrust levers, it's normal good practice for the PF to rest his/her hand gently on the levers. That applies whether the AP is being used or not. As has been said, it has the twin advantage of providing tactile feedback to the PF, and enabling him/her to override or modify the A/THR inputs on the rare occasions that may be necessary.

It's also been pointed out (particularly by Airbus Industrie) that, in a decaying-speed situation, any forward movement of the thrust levers MIGHT be taken by the PF as sufficient indication that total thrust is increasing. The only true indication of that are, of course, the N1 and/or EPR gauges. However, what can be said is that an absence of thrust-lever movement would alert the PF to A/THR failure. On FBW Airbuses, the thrust levers are stationary in the CLB gate until landing, unless the PF is using manual thrust.

In the early days on the A320, there were a number of incidents on visual approaches using A/THR during which the PF did not realise that, due to his mismanagement of the FMGC and with one or both FDs still on, the system was still in IDLE mode (OPDES). In those days, there was no protection in IDLE/OPDES mode to stop the speed dropping below VLS (until Alpha-Floor). This was a contributory factor to the fatal accident of an Indian Airlines A320 at Bangalore.

Sidestick_n_Rudder
15th Aug 2015, 11:52
For long time I have considered myself a proponent of moving TL (as most pilots are) even though the only A/T aircraft I have flown was the Bus.

However, I had a couple of jumpseat visits in the 737/767/787 FFS and witnessed quite a lot of trouble the moving TL's (sorry, throttles :}) could give - eg. when the pilot forgot to disconnect the A/T during low speed RTO, or understanding mode reversions, fighting with A/T during flight, disconnecting servos the etc.

Having seen this (plus reading some accident/incident reports where A/T was a contributor), I have started to lean towards the Airbus system being actually simpler and more intuitive.

The only problem of the non-moving TL's is less intuitive intervention when the system is not doing what pilots want. I believe, however, that this could be addressed by training and some changes in procedures. We should be taught/trained/encouraged to grab the TL's (like Boeing guys do) instead of pushing buttons to get the engines do what we want...

vilas
15th Aug 2015, 13:18
Chris Scott
Bangalore accident was not due to non moving thrust levers but due to basically not monitoring the FMA to confirm ATHR mode but assuming it to be in speed mode. And off course they did not monitor the speed at all because there was not a single call about speed despite the fact it was 27KTS. below Vapp. If you consider SFO accident where despite moving auto throttle and tactile feed back of B777 the result was same because the reason was also same, not monitoring speed which was 31KTS. below Vapp. In both the incidents very experienced captains were under command checks. The fact is no matter which aircraft one is flying you cannot fly an approach without monitoring speed. One of the reasons a new system is disliked because it takes you out of your comfort zone. You need to develop a new skill, a new habit. I noticed Airbus FBW seems to bring out strong emotional responses, it is loved or hated but rarely ignored. A casual inquiry about an airbus procedure draws even some Boeing pilots to respond to it with ridiculous caveats like " I don't know anything about airbus but". Where there are discussion threads by all means give your opinions. But when a airbus guy asks for type specific procedure it should be left to airbus guys to answer.

Chris Scott
15th Aug 2015, 13:35
vilas,
You should try reading the whole of my post more carefully - in particular the last paragraph. I said that pilot mismanagement of the FMGC was a "contributory factor" in the Bangalore accident. I left it to the reader to decide if, in a conventional system with moving ("driven") thrust levers, the PF might have realised that the thrust was commanded to idle by the A/THR system.

Centaurus
15th Aug 2015, 14:10
Slight thread drift for a moment but still has something to do with throttles.
The Boeing 737 FCTM under the sub-heading Manual Flight, states the PM should make AFDS mode selections at the request of the PF.

Sub-heading Automatic Flight, states when the autopilot is in use, the PF makes the AFDS mode selections. The PM may select new altitudes but must ensure the PF is aware of any changes.

The problem arises when the aircraft is flying with one engine inoperative with the autopilot engaged. In normal two engine flight the rudder is rarely used. In asymmetric flight, rudder is used especially where thrust changes mean rudder adjustment to correct for changing yaw. In asymmetric flight the autothrottle is switched off as per QRH.

So what we have in the one engine inoperative situation, with autopilot engaged is actually a combination of manual and autoflight. That is, manual throttle and manual rudder plus autopilot pitch and roll.

Because of the half automatics and half manual tasks associated with one engine inoperative, it then becomes an unwieldy situation where the PF makes changes to the MCP involving airspeed and heading and even altitude changes, while at the same time having one hand on the live throttle and maybe also making rudder trim adjustments. The one arm paper hanger comes to mind.

Clearly Boeing should amplify its advice on MCP changes by the PF when on one engine and the automatic pilot is engaged. . It would be sensible to have the PM make MCP changes at the request of the PF during asymmetric flight. This leaves the PF with the task of simply operating the live engine thrust and adjusting rudder pressure changes backed up by manual rudder trim if required.
While this becomes a matter of common sense, the fact remains there are pedants in the simulator who arc up if the Boeing FCTM advice is not followed to the letter

Chris Scott
15th Aug 2015, 14:33
Quote from Sidestick_n_Rudder:
"The only problem of the non-moving TL's is less intuitive intervention when the system is not doing what pilots want. I believe, however, that this could be addressed by training and some changes in procedures."

Hear, hear... The problem is that, as I understand it, the majority of airlines are forbidding - or at least discouraging - pilots from practising their manual-thrust skills on revenue flights. That means that pilots are poorly placed in the event of an A/THR failure, as the BA762 investigation has demonstrated:

https://www.gov.uk/aaib-reports/aircraft-accident-report-1-2015-airbus-a319-131-g-euoe-24-may-2013

In my day, in my airline, there was no specific rule for the manual flight case. My preference for manual landings was to use manual thrust, and that included those in gusty crosswinds with windshear:

http://www.pprune.org/rumours-news/564529-ba762-report-released-cowl-doors-openning-9.html#post9078674

Because of its relative complexity, the best way to practise the transfer to manual thrust in flight is to do it when workload is low. If the AP is engaged, I recommend leaving the it engaged until manual thrust is established. During my time on the A320 series (1988 - 2001), I'm not aware of any incident attributed to the voluntary use of manual thrust. By the time I retired in 2001, however, the majority of line pilots, trainers and managers rarely disconnected the A/THR. Pity...

Denti
15th Aug 2015, 16:01
@Centaurus it becomes even more weird when you have experienced that the 737 can quite wonderfully use the autothrust in OEI flight as well as keep the rudder where it belongs as well, thus providing full automatic flight. Sadly that is only available below 1500ft during an ILS dual channel approach and during go around until another roll mode is engaged. I'm quite sure the autoflight system could work that way throughout the envelope, but it wasn't certified that way and thus we have to continue impersonating the "one armed paper hanger".

Quite honestly, the non moving thrust lever were surprisingly a non-issue during training and on the line. Except for those rare occasions where one would love to nudge the thrust up a bit for a second or two or pull it back for the same time span. That is much more easily done with a moving thrust lever where one simply overpowers the servos for a bit. Apart from that it really is not an issue. But then, i do work for an outfit where manual, FD off flight is encouraged the same way that manual thrust is during manual flight. Rarely do i see a colleague using AT during manual flight. Easiest way to get there is of course during a phase of flight where thrust is idle anyway, just pull those levers back and there you have it.

Goldenrivett
15th Aug 2015, 16:30
Hi Chris,
By the time I retired in 2001, however, the majority of line pilots, trainers and managers rarely disconnected the A/THR. Pity...

M Scott's paper "The Management of Flight Safety"
https://www.google.com/webhp?sourceid=chrome-instant&rlz=1C1ZMDB_enUS505US505&ion=1&espv=2&ie=UTF-8#q=Incidents%2BBA%2BAirbus%2Bmanual+thrust has an interesting observation: " In British Airways, for example, the flexibility to use manual thrust on the Airbus fleet has been banned, so that pilots are increasingly relegated to monitoring the automatics. Thus the ‘system’ has become increasingly poorly ‘engineered’ from a cognitive point of view."

I gather the reason was because there were far more "incidents" on the Airbus fleet than any other fleet with low speed during manual flight. Since all BA pilots have a similar ability (on average on all fleets) one is led to conclude that there is an ergonomic disadvantage with the Airbus TL set up, or the absence of "feel" due to flight path stability with auto trim.

Hi Denti,
Easiest way to get there is of course during a phase of flight where thrust is idle anyway, just pull those levers back and there you have it.


If you had conventional TL, you could simply disconnect and leave the TL where they were during any stage of flight.

Chris Scott
15th Aug 2015, 17:31
Hi Goldenrivett,
"I gather the reason was because there were far more "incidents" on the Airbus fleet than any other fleet with low speed during manual flight."

Thanks for the link to that paper. I can only hazard a guess at the identity of the "senior airline manager" in April 2004 to whom M. Scott refers.

By "manual flight", do you mean manual thrust? Up to the end of 2001, I was aware of at least one serious, windshear-related loss of airspeed in manual flight, leading - IIRC - to a firm-ish impact with the runway during the go-around. But that was using A/THR. Maybe the incidents you heard of happened later?

(It may seem perverse, but I was never entirely convinced that the AI policy of using Flaps 3 for A320-series landings when only light or moderate windshear was expected was justified. Except in a strong headwind, the thrust requirement can be lower than ideal. Sometimes the A/THR reduces the power so much in a temporary headwind shear - almost to flight idle in some cases - that the engines take a while to spool up for the inevitable loss of IAS when the headwind dies away. An experienced pilot would never retard the thrust that much at a low height - say, around 100 ft.)

The understandable desire for cross-fleets standardisation created minor problems for the BA Airbus fleet in my day, but I wonder if BA has reassessed its policy since BA762... Differing beasts can't always be ridden the same way. Pilots can and do adapt. I doubt that any pilots are dual-rated on, say, B744 and A380?

vilas
15th Aug 2015, 17:38
In conventional aircraft when you make flight path change or thrust change visually the tactile feed back and speed stable behaviour provides additional cue. Airbus FBW in manual flight you fly only by visual cues. The changes to flight path, speed and thrust are visually noticed and effected. Not only there is no feed back in the stick, the flight path stable aircraft does not pitch up or down to speed changes, power changes only large increases will cause a dampened response. In airbus since any displacement of side stick is a demand for change either in pitch or bank the stick needs to be in neutral most of the time, it is essentially intermittent contact flying. Basically in manual thrust in any aircraft pitch changes require thrust change but in airbus you only see and do as your hand will feel nothing. It is different but not difficult. Elevator integrator holds the elevator where ever you leave it and trim catches up automatically. The aircraft is always in trim. But pilot always needs a good scan. It is immaterial whether AP is on you still scan instruments in the same manner but only watch changes happening instead of making. In SFO they never monitored the speed because may be over confidence in automation or it is possible never developed raw data skills in the first place. Design of the automation had nothing to do with it. Any one who has the skill can maintain it with very little practice.

Chris Scott
15th Aug 2015, 18:05
Quote from vilas:
"Basically in manual thrust in any aircraft pitch changes require thrust change but in airbus you only see and do as your hand will feel nothing. It is different but not difficult."

What do you mean by "[in manual thrust] ... in Airbus your hand will feel nothing." ?

(BTW, I agreed with your previous interpretation of the B777 accident at SFO and the B737 at AMS, and the fact that moving throttles are not a panacea for ignorance or complacency.)

Goldenrivett
15th Aug 2015, 18:16
Hi Chris,
Maybe the incidents you heard of happened later?
The incidents I heard of all happened before 2004. They were mostly low speed events during ILS Approaches in good weather. Crews were practicing manual thrust approaches in anticipation of their next sim check.

Due to the number of events, management perceived it was safer to ban manual thrust practice on the line and devote extra sim time for manual thrust practice. I don't know what the current position is.

vilas
Basically in manual thrust in any aircraft pitch changes require thrust change but in airbus you only see and do as your hand will feel nothing. It is different but not difficult.
The difference is that all clues are visual and there is no priority over any parameter.
On conventional aircraft, "feel" is devoted almost entirely to Angle of Attack control.

RAT 5
15th Aug 2015, 20:05
@Centaurus it becomes even more weird when you have experienced that the 737 can quite wonderfully use the autothrust in OEI flight as well as keep the rudder where it belongs as well, thus providing full automatic flight.

Is an autopilot rudder channel available on B737? None I've flown. Every QRH I've seen B733/737/738 has instructed A/T off with SE ops. True, if an engine fails in CRZ the A/T will increase and try to maintain speed. I'm not sure how long it will remain connected. On takeoff it will disconnect during climb out.

Question to the AB pilots: when flying an approach with A/T engaged do you follow through on the T/L's? If not where do you have your inside hand? I suspect the B777 Asiana PF had both hands on the yoke; might be wrong.

tdracer
15th Aug 2015, 22:59
RAT, according to the reports, the Asiana pilot was having to exert ~80 lbs. force on the yoke as the airspeed decayed towards stall. I think we can safely assume he wasn't doing that with one hand on the throttles :sad:.
Although not a pilot, I've spent lots of time on the flight deck during flight tests - and observed countless simulator sessions - and the PF has always had one hand on the throttles during approach/landing. I've assumed that was SOP and pilots who flew Boeings were taught to do that.

BTW, I don't think BA 38 (777 that landed short at Heathrow) is particularly relevant to this discussion. Those engines were incapable of producing additional thrust due to the ice-blocked heat exchangers, regardless of how the thrust was being controlled. There was nothing that the pilots could have done to prevent the crash landing.

birdspeed
16th Aug 2015, 00:56
I would say that the Capt under training flying the Asianna B777 at SFO had lost his link between speed and the throttles. He was converting from the A320.

I fear will will see more of these types of accidents in the future as a whole generation of pilots no longer touch the throttles. The thinking is that we're there to back up the autothrottle-- WRONG. I always view the autothrottle is there to back me up. Not possible if the throttles don't move.

Accidents where non-moving throttles may have been a factor-

Tam3054 at Sao Paolo,
Air Inter at Strasbourg

Winnerhofer
16th Aug 2015, 01:13
Indeed, he forgot that there's no Alpha Floor on Boeings...

RAT 5
16th Aug 2015, 02:55
Yes, but back to my question of AB pilots: if you are making an approach, of any sort, but especially a manually flown approach with ATHR engaged, where is your inside hand?

AB pilots have said that they need to increase their scan to include N1% gauges to monitor the ATHR system. To me this is increased work load at a time you might not find it the most convenient. On some a/c, with PFD and speed tape & speed trend vector display, as speed increases or reduces you can see the speed vector move. If the correct thrust adjustment is made you see the trend vector respond in the opposite sense. I'm not suggesting tunnel vision scan, but this important information is in your central scan. If using ATHR with moving levers you can 'feel' the a/c respond, then see its effect. If manual thrust then you apply the correction yourself and see the result. It's using more senses and having a solid feedback loop in your brain. IMHO you are more 'engaged' with the a/c. It is intuitive. If you have set a datum thrust for the phase of flight you can monitor speed and make a nudge forward of backwards as appropriate; or feel the ATHR do the same. You then follow up that sense with a quick scan of the N1% gauges.

Back to my earlier thought about the basic design philosophy of AB. This is not a FBW thing, but a whole a/c design thought. It may be true of EB and others as well. I wonder if the basic concept was to design an a/c that would fly approaches automatically, via ILS, LNAV/VNAV, RNAV, MLS etc. Program the approach in the FMC, engage the automatics and monitor. At minimums, no autoland, the human intervenes (gwad forbid) and attempts to bring a/c back to earth safely. Thus PF is really PM of the automatics. The non-handling pilot is then PM of the other PM/PF. The big difference between the two is one moves the gear & flaps, the other doesn't. One plants it on the ground or monitors the a/c do it and then one taxis the a/c. With 2 PM's I wonder how alert the PNF/PM is?

The certifying authorities need to ensure the human (let's call them pilots) could takeover if HAL goes awol to walkabout. That was seen by the designers as last resort, not the norm. Thus the depth of training to do such things is minimal, and the amount of 'on the line' practice is likewise. Many managements don't like pilots intervening and screwing up; so it's automatics to the max. Safer, cheaper, smoother.
All this might be great if operating from the major airport hubs. Perhaps the fully automatic a/c works great there. Take it out of its comfort zone and the basic design might not be quite so good. If you started with an a/c system design to operate in Africa, the Greek islands, Nepal, Indonesian islands would you have created the modern AB solution? Yet that is where they operate.
Note this is nothing about FBW; it is about the extent of automatics. The B737NG is very capable of flying, using automatics, from 400' on take off to a full autoland ILS or automatic NPA to MDA. It's more about the way there a/c is managed.
We hear many times from human factors professors that humans are not the best monitors of automatic systems, especially for hours on end. Airlines demand a high education from their plot recruits and then, due to a/c design, put them in a place they are ill-designed for. When airlines buy expensive a/c they buy the best design to suit the route demands. The same with the military. You try to balance and match your resources to maximise success of the operation. I wonder if modern automatic a/c, and the type of pilot in charge, is the best combination. Have modern high tech a/c been designed with human pilots in mind, or are they dream of lab' technocrats; designed because they can be? Has it all been necessary, and has it all been for the best? Will the future become better, or will it steam full ahead with the pilots out of the loop? Will they be given new toys and then enter the trained monkey system and be forced to adapt their natural skills to learn how to play with them? Square pegs, round holes. Are a/c best suited to those who should be managing them. If the technocrats win the argument and a/c continue to become more automatic, then the ground environment needs to keep pace: and, perhaps a different sort of human needs to be the PF/PM.
It seems to me that the technology is advancing at a much faster rate than any other link in the chain; because it can. It is all sold on cost benefit. The customers lap that up and so new a/c are designed in the R & D centres. Meanwhile the XAA's are so far removed from this that pilot training, checking, monitoring is still in the dark ages relative to the task involved. The certifiers are involved in that the a/c have to jump through time tested hoops. All the other links in the chain, including the pilots, as well. Is this the best way forward? Should thee be different hoops?
In some theatres a much more simple a/c is demanded, e.g. DH twin otter in Papua NG mountains. An automatic AB/Boeing type a/c would not work. That requires special pilot skills. B747 flying short hops in Japan is very different than a conventional long-haul B747 operation. Different pilot mind set. The same is true of the USA commuter market. Pilots fly in/out of tiny strips, but also JFK & Chicago. Different mind set and skills. Eventually, if it continues, all a/c may become FBW with associated automatic systems, but the pilot skills will still be very varied. Yet the basic training & checking will still be the same to obtain & maintain the licence the world over.
Perhaps it's time for a think tank or brains trust to sit down and have a good hard analysis about the world wide industry, its requirements and how best to create the ideal balance between the human and the task at hand. Even the a/c designers. Have a feedback loop from the customers and ask them if the suppliers are on the right track for the operators.

Denti
16th Aug 2015, 02:56
Is an autopilot rudder channel available on B737? None I've flown. Every QRH I've seen B733/737/738 has instructed A/T off with SE ops. True, if an engine fails in CRZ the A/T will increase and try to maintain speed. I'm not sure how long it will remain connected. On takeoff it will disconnect during climb out.

Yes, the Rockwell-Collins autoflight system (new MCP with the slightly larger buttons) on the 737NG has a rudder channel. You need to order the rudder servo as a customer option though. It is needed to use the CAT IIIb fail operational mode including automatic rollout and OEI CAT IIIa capability. We fly 737s equipped that way for around 10 years now.

Question to the AB pilots: when flying an approach with A/T engaged do you follow through on the T/L's? If not where do you have your inside hand? I suspect the B777 Asiana PF had both hands on the yoke; might be wrong.

I guess it depends on your SOPs. As part of our general SOPs for all fleets we have to "guard" (have the hand on them) the controls below FL150 with the autopilot engaged. Thrust levers have to be "guarded" latest below 1000ft, but it is advised to have the inside hand there below 5000 ft. So yes, we "follow through" (not that anything is moving) on the thrust levers on the airbus.

vilas
16th Aug 2015, 03:26
Chris Scott
Sorry I meant in manual flight. In a conventional aircraft the pressure felt on the yoke varies with thrust or speed change. That offers you another cue. That is what I meant.
Golden: the thrust/drag couple effect is also felt in the yoke. It is dampened in airbus. Basically it comes from the design of maintaining 1g when stick free.
Bird speed: It is airbus SOP to keep hands on thrust levers during approach. Latest being 1000ft. AGL. SFO pilot was perhaps not following SOPs even in Airbus.

kbrockman
16th Aug 2015, 09:31
Accidents where non-moving throttles may have been a factor-

Tam3054 at Sao Paolo,
Air Inter at Strasbourg

too much airspeed and too fast/long landing leading to a crash happened numerous times on other airliners before moving TL or not.
Air Inter seemed to be a myriad of automation unfamiliarity, yes some design issues , questionable procedures (speed, no GPWS) , again where come the non moving TL in play?


Asiana
Indeed, he forgot that there's no Alpha Floor on Boeings...

BS, pardon my French, no pilot in their right mind has the alpha floor protection as part of a landing procedure.
BTW at 50' RA the Airbus switches to flare mode.

vilas
16th Aug 2015, 10:04
He is joking about alpha floor. And they were 31kts below Vapp so if there was alpha floor it would have come before 50ft. In Bangalore crash it triggered at 135ft. but did not have the time to spool up and stop the descent.

kbrockman
16th Aug 2015, 10:14
He is joking about alpha floor.

Now there's a joke that flew right over my head, still seems a bit of a strange statement.

Bangalore crash it triggered at 135ft. but did not have the time to spool up ad stop the descent.

...And they where flying below the flightpath ignoring the altitude warnings altogether failing to increase thrust.

vilas
16th Aug 2015, 12:19
kbrockman
They were coming off VOR approach converted to visual approach. But because one side FD was on FMGS went in OP DES with thrust at idle. Pilot tried to maintain visual 3 degree flight path with falling airspeed. Obviously they were not waiting for alpha floor but did not monitor speed assumed ATHR in speed mode.There were no warnings. Same as SFO but being an airbus alpha floor triggered and then they themselves triggered TOGA. In the ultimate analysis they lost there life because they did it five seconds too late.

Chris Scott
16th Aug 2015, 13:49
RAT 5,
I like and agree with your analysis of the current automation problems in the aircraft industry as a whole.

You suggest, however, that a/c like the FBW Airbuses are designed to be operated into large hubs with autoland facilities. It needs to be said that the A320-series is well capable of doing anything that, say, the B737-200 can do, and do it better in most cases.

Non-precision approaches and/or visual circuits are easier to fly: with or without AP; with or without A/THR. Manual thrust is a delight on the Airbuses, partly because the FADEC gives such accurate responses to small thrust-lever movements. Used as designed, GS-Mini is a treat in gusty wx. FPA is, as you probably know, terrific for non-precision approaches: with or without the FD; with or without the AP. (In the airliner field, these were all innovations of the A320 in 1988, although the A310 had pioneered a basic FPA in 1983.)

Back to the thread topic! Quote from vilas, re the A320 accident at Bangalore in 1990:
"They were coming off VOR approach converted to visual approach. But because one side FD was on FMGS went in OP DES with thrust at idle. Pilot tried to maintain visual 3 degree flight path with falling airspeed. Obviously they were not waiting for alpha floor but did not monitor speed assumed ATHR in speed mode.There were no warnings. Same as SFO but being an airbus alpha floor triggered and then they themselves triggered TOGA."

Thank you for now reiterating my brief analysis in my post #14 (http://www.pprune.org/tech-log/566091-thrust-levers-moving-not.html#post9083108) yesterday (final paragraph), to which you took exception at the time. No need to apologise for changing your mind! :)

Centaurus
16th Aug 2015, 14:28
Although not a pilot, I've spent lots of time on the flight deck during flight tests - and observed countless simulator sessions - and the PF has always had one hand on the throttles during approach/landing. I've assumed that was SOP and pilots who flew Boeings were taught to do that.


Several years ago I was involved training crews from an Asian military operator on the 737-Classic. I understood at the time the military wanted to expose their 737 crews to various training providers in Europe and USA rather than their own airlines. The first thing I picked up was that in flight both pilots had their hands firmly placed on their knees in between MCP selections during automatic flight.

Through the interpreter, I suggested that during any autopilot instrument approach it was wise to have one hand lightly on the throttles rather than both hands on the knees. My suggestion was curtly declined by the chief pilot who was PF and he continued with their own policy. Through the interpreter, I said that each throttle had a clutch motor and if a clutch motor happened to fail, the auto throttle would not move except by hand. By lightly resting one hand on the autothrottles during an approach, a split in the throttles could be quickly picked up.

Again this was ignored with an imperious wave of the chief pilot's hand. I found his attitude irritating especially as during the pre-flight briefing I specifically mentioned the wisdom of one hand resting lightly on the autothrottles during an instrument approach and particularly on final approach.

Accordingly, I re-positioned the simulator at 5000 ft on an automatic pilot/autothrottle descending DME arc leading into a coupled ILS approach. Both thrust levers were back at idle as expected for the clean descent at 210 knots. Via the instructor panel IOS, failure of the No.1 engine AT clutch motor was initiated while both throttles were at idle of 30% N1

Approaching 10 miles and coupled to the ILS, the pilot called for gear down, and various flap selections as the speed bled back at each flap selection until the automatic throttles started to increase thrust towards landing configuration thrust settings. Naturally, the No 1 thrust lever remained at idle as its clutch motor was inoperative. All the time both pilots had their hands on their knees apart from configuration selections by the co-pilot

At five miles in IMC on final, No. 2 engine was around 75%N1 to make up for the lack of thrust from the closed No.1 throttle which indicated 30% N1.. The autopilot was struggling to track the ILS under significant asymmetric power and the control wheel was now 45 degrees off centre. Rudders were central. Neither pilot said anything and did nothing but stolidly gaze at the displaced control wheel and presumably at the split in the thrust levers.

I was amazed, as I had never witnessed anything like this before. Eventually I leaned over to the interpreter who was sitting in the jump seat and asked her to tell the captain about the split in throttles with No.1 at idle and No.2 at 75%N1. Still with both hands on his knees the captain shouted at his co-pilot in Chinese that No.1 engine had failed and called for the engine failure and shut down checklist from the QRH. There was of course nothing wrong with the engine and the throttle could be moved manually if desired.

As the co-pilot dived to locate the QRH from somewhere on the cockpit floor (he never queried the captain's actions probably due to cultural mores), the autopilot disengaged itself under excessive control deflection, and the 737 started to roll rapidly left under the influence of asymmetric thrust. The captain still kept both of his hands on his knees making no attempt to stop the ever-increasing yaw and roll. He did however shout louder at the co-pilot presumably urging him to get to the right page of the QRH. I saw the co-pilot flipping the pages of the QRH as fast as a bank teller counting notes and I fully expected him to lick his fingers to get a faster flick.

I watched in great interest knowing that no one would ever believe my story at what I was seeing. By now the simulator ADI was showing 30 degrees nose down and 80 degrees angle of bank with a massive rate of descent. At no stage did the captain take his hands off his knees and at no stage did the co-pilot look up from flicking then pages of his QRH. All this below 1000 ft on final and in IMC.

All the captain had to do early in this drama was to use both throttles to get equal power and full aileron to level the wings and go-around. The GPWS was going mad and to avoid the inevitable loss of face that would have occurred with the chief pilot crashing the aircraft, I froze the simulator when the crash was inevitable.

We all went for coffee in silence. There was no point in labouring the point while culture reigned supreme. I didn't operate in the simulator with that crew again so I have no idea if they changed the company policy of hands on the knees on instrument approaches...

Southpole
16th Aug 2015, 14:47
Flew both of them, but I have many more hours on "not moving"..

I personally don't like those who are trying to convince the others that one system is better than the other one, these are just opinions.
That being said, on Airbus you are supposed to keep your hand on the thrust levers as well as on Boeing and you can "help" the autothrust in any moment. If you feel you need to.

I personally do not see any advantage in having my hand rallying forward and back all the time to follow the autothrust.

Airbus and Boeing pilots make the same mistakes, they just do not crosscheck properly their instruments and many times they keep their hands on the armrests.

My opinion: there is no safer system here, and I prefer the not moving.

RAT 5
16th Aug 2015, 20:57
Centaurus: I sometimes wonder why people make an easy job difficult.

I guess it depends on your SOPs. As part of our general SOPs for all fleets we have to "guard" (have the hand on them) the controls below FL150 with the autopilot engaged.

What's it got to do with SOP's? Airmanship is an SOP, IMHO. Covering the controls on approach is surely an airmanship item. I've flown with the trained monkey brigade and it is very disturbing. "it's to an SOP, so I don't do it." "Where's that written?" For gawd's sake!

Centaurus
17th Aug 2015, 03:00
That being said, on Airbus you are supposed to keep your hand on the thrust levers as well as on Boeing and you can "help" the autothrust in any moment

I don't know about the Airbus, but to "help" the autothrottles is frowned upon by Boeing 737 series. In fact, Boeing published a bulletin many years ago warning crews not to apply pressure to the throttles with AT engaged as any pressure more than a certain figure (I don't recall the psi) can damage the clutch motors in each throttle.

This mostly happens when selecting TOGA and misguided PM's urge the throttles forward with their hand behind the levers as a backing up policy when there is no need since they won't slip back because of the internal throttle friction system.

Like those pilots that "follow through" on the flight controls while the other pilot is PF, there is nothing more annoying for the pilot to be smoothly opening the throttles manually and feel the other eager beaver pushing them from behind. In fact, something goes wrong and the PF suddenly whips the throttles to idle to abort and the PM still has his hand behind the levers as a following through habit, severe hand damage has happened when the PM's his hand is jammed between the throttle and the top of the start levers because he can't remove it in time. . I have seen it happen in the simulator and it is very very painful.

vilas
17th Aug 2015, 03:25
RAT 5
Keeping a hand on thrust lever is a habit for moving throttles. In AB FBW it doesn't make sense since it gives you no clue as to what's happening. you watch the actual thrust. This can make pilots believe that it is never required. So they need to be told that at least during an approach you need to keep your hand on the thrust lever not because it gives any clue on approach but to switch to manual thrust if required without grabbing something else in a hurry. Approach starts a long way up so SOP defines a limit. The habit of disregarding SOPs is not necessarily a sign of superior piloting skill. Many do it out of ignorance also. In FBW, armed with only FCOM/FCTM you are not in a position to change or device your own procedures. Some airlines have almost come to grief doing that. You need to keep the manufacturer in the loop because behind the SOP software/hardware and design characteristics are involved. In FBW it may not be what it appears.

Uplinker
17th Aug 2015, 12:09
Centaurus, your Chinese SIM story is very scary. I suspect that the Chief pilot was not up to the job, and that he probably was one of those delightful barons who did not like a woman (the interpretor) or you pointing out his mistakes.

Given the Chief pilot's appalling lack of ability I would have let the SIM crash. No point saving a person's embarrassment if they are clearly not up to the job and peoples' lives might be at stake.

A colleague who now flies with another asian airline sat on the jumpseat on a line flight and during the climb watched both pilots reading newspapers that obscured the instruments, and he later had to speak up when they had both mis-set the arrival QNH by 8mb.


Back to the thrust levers. Flying Airbus, we keep our hand on the non-moving levers on approach and the other hand on the side stick. At any moment something could happen or a failure or a runaway might occur which would require instant manual reversion, or a Go-Around, so the hands should be on the controls.
As far a nudging or helping the A/THR, I suppose that on Airbus we learn to trust the A/THR and how it will react, (or not react) coupled with good instrument scanning. In theory, we could use the levers in a similar way to Boeings: nudge the levers just forward of the CLB gate and back to speed up, and backward from the CLB gate to limit the maximum thrust available to the A/THR to slow down.

However we should not invent our own procedures, because there may be unintended consequences.

RAT 5
17th Aug 2015, 12:48
Thank you, guys, for the information. I ask this from a human factors point of view.
We use many senses when flying, subtle and often without realising it. Sound is one that not many are aware of. It was ably demonstrated when on B733, on approach, you had the wipers beating back & forth like having a bag of bolts in the washing m/c. It deadened all outside noises including the engines. Turning them off was such a relief.
Another subtle sense is touch. On approach, you see the speed dribbling back (or increasing) and you 'feel' the T/L's opposing the drift, or you do it yourself with a suitable nudge. It's instinctive. You see, you feel, you hear.
Now in non-moving T/L's you remove the 'feel' and rely purely on sight = scan, then sound. I see every day, and in the sim, B738, the younger pilots and cadets with tunnel vision on the PFD. They don't even look at the ND never mind the N1% gauges. IMHO they are as important as a flight control imparting energy to the a/c. Give it the wrong amount and it ain't going to do the job. You can anticipate the speed will decay or increase. I try to encourage PM to include them in their scan to ensure PF is on the ball.
So my question; with non-moving T/L's you have to be more vigilant with the N1% and the scan is a very visual only affair. Do you find this instinctive and are you aware of any more work load? Or do you notice many pilots having blind faith in the system and not monitoring it at all?
Notice I'm not advocating one system being better than the other; I'm asking from those who've operated both if they are aware of any change in workload between the two. Or any other comments they'd like to share.

vilas
17th Aug 2015, 14:49
RAT 5
Let me analyse what you say:

1. On approach, you see the speed dribbling back (or increasing) and you 'feel' the T/L's opposing the drift, or you do it yourself with a suitable nudge. It's instinctive. You see, you feel, you hear. First it is not instinctive but habitual and habits can be unlearned or learned. Second suitable nudge is not manufacturer's recommendation. Also it doesn't ensure that N1 is increasing. In Airbus also you can nudge forward against manufacturer's recommendation and off course you see and hear.
2. They don't even look at the ND never mind the N1% gauges IMHO they are as important as a flight control imparting energy to the a/c. Give it the wrong amount and it ain't going to do the job. You can anticipate the speed will decay or increase.
N1 is a reference. The basic parameter that attracts you to N1 is speed. The anticipation of decay or increase of speed doesn't take much as speed trend arrow does it for you. The problem is not looking at N1 gauge but not looking at the speed at all till the point of crash experienced and inexperienced alike.
3. So my question; with non-moving T/L's you have to be more vigilant with the N1% and the scan is a very visual only affair. Do you find this instinctive and are you aware of any more work load?
As long as one knows how to manage trend arrow you don't need any more vigilance. Maintain correct pitch and manage trend there is absolutely no problem.

Uplinker
17th Aug 2015, 15:05
Hi RAT.

For what it's worth, (and I have never flown moving A/THR levers), I find the Airbus easy to fly and interpret. If the speed bleeds away, I see it on the speed tape and trend arrow. I feel the reduction of energy by the change in pitch and sink, and see the pitch trim wheel moving. While this is happening I flick my eyes to the N1 or EPR gauges and expect to see the blue arc(s) appear that signifies a change of thrust command. Then I expect to see the N1 increase in response to the demand and I sense the speed increase through all the cues I just mentioned, including sound, as you say. I don't think that is any more work load than an aircraft with moving levers, and non moving levers do force me to keep up a good instrument scan which is a good thing.

So although the thrust levers are static, I am still able to assimilate the speed state of the aircraft. However, if the A/THR is being lazy or misbehaving, then it is harder to tweak than moving levers.

The danger is that by feeling the levers moving, some pilots assume that the A/THR is working. It usually is, but the levers are only the input, i.e. the demand to the engines, whereas pilots should be checking the output, i.e. the result of the demand, which in the case of the engines is the N1/EPR gauges. It appears anecdotally and from several speed related crashes that if the levers stop moving owing to a fault, or incorrect mode selection then this does not always get noticed by pilots, so a proper instrument scan is very important, as it always has been.

As we all should know and Centaurus's SIM demonstrated, not making a proper instrument scan can lead to disaster.

No Fly Zone
18th Aug 2015, 11:32
I admit that this is no more than a WAG! My WAG is that those who hand-fly frequently probably appreciate the visual ques and physical movement of the levers. Those who do not hand-fly frequently are probably relying on graphic displays to report thrust details, rather than lever position. While firm SOPs 'may' help, every pilot has his or her own routine for scanning and obtaining important information during 'critical phases' of flight. As long as s/he obtains the information from a reliable source, does it matter which source is used?
I'm old, grey and very used to pushing/pulling multiple levers, must of which have friction adjustments. If I noticed an un-commanded change of any lever's position, I think I'd test it a little bit, reset it as necessary and tighten the friction lock.
(FBW, including auto-thrust) is not for me. It is perfectly OK for our grand-kids, but only if they fully understand exactly how every component works and interacts with every other. Some do - and some do not.) And please forgive the rant.:(