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B777 single engine go around and TOGA switches

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B777 single engine go around and TOGA switches

Old 6th Jul 2021, 22:11
  #41 (permalink)  

Only half a speed-brake
 
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The thing is, Airbus pilots are trained to have a hand on the thrust levers. Not to mention it's kind of complex to have both on the stick given the location, thus the TLs become a natural resting place.

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Old 6th Jul 2021, 22:26
  #42 (permalink)  
 
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But the Airbus thrust levers are not back driven, so simply having your hand on the lever doesn't tell you much. On Boeing, if you have your hand on the lever and it's all the way back at idle and not moving - while your speed is getting dangerously low - a competent pilot should make the connection (at least if he'd been trained to)...
Reportedly, due to the way the Boeing back drives the yoke on the 777, as Asiana was approaching stall the pilot was having to pull back on the yoke with something approaching 100 lbs. force. Not many people could have done that with one hand on the thrust levers...
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Old 6th Jul 2021, 23:28
  #43 (permalink)  

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The idea that a hand on non-moving levers (stuck at idle) tells you more than a hand on non-moving levers (placed in CL detent) is illogical.

And likewise is the implied suggestion the crew would had received vital information from those non-moving thrustlevers if they had a hand on them and would have reacted, the same crew who could not react to the low speed situation unfolding right in-front of them on the PFDs because it has never occured to them that low speed is no good.

Let's face it, there are real-pilots (Boeing), half-pilots (Airbus) and non-pilots. All of them make mistakes, but the outcome differs accordingly. An Airbus half-pilot does not need to have his hand on the TLs to know what the engines are doing (as you well explained already it's non-moving and the placement is not corelated to thrust under A/THR ops) since he's vitally trained by necessity to watch the N1/EPRs.

Thus an Airbus half-pilot moving to B will have no need of touching the TLs to derive information (yet again, those were not moving anyway in the Asiana case) but would know what the engines are doing or not by looking at EIS. Still, he would have the hand there anyway, a fact showing even the last sentece of the post above is incoherent.

Now, take a non-pilot from Airbus to Boeing and there's your dish as ordered. Served on a plate of autothrottle logic that apparently has more downgrading mode reversions than the Airbus FBW itself (hyperbole).

Last edited by FlightDetent; 7th Jul 2021 at 07:13.
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Old 7th Jul 2021, 00:52
  #44 (permalink)  
 
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Originally Posted by tdracer View Post
With the notable exception of the 787, the autothrottle system on Boeing aircraft is not designed or certified as 'flight critical' - but I bet they don't teach the pilots that part...
Can you elaborate on this bit please tdracer ?
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Old 7th Jul 2021, 00:57
  #45 (permalink)  
 
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Never understood why Airbus wants us to fly with a hand on the levers if the AT is on. It always feels pretty useless to me. If I'm that worried about the wind, I probably have the AT off anyway.
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Old 7th Jul 2021, 01:47
  #46 (permalink)  
 
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@FlightDetent

I can see your post is full of humour, which might be missed by a few, but it is also some valid points re: "feedback" via the back driven thrust levers.

When I began flying, it was taught, actually, drummed into us. One hand on the "lever" at all times.

In the following 30 years, this has worked out well across all types, SE Pistons, Twin Pistons, Twin Turbine, and 4 different Jet types. (3 Real-Pilot types (WW24, Jet, B787), and 1 Half-Pilot type, (A320)) The first Jet type didn't have any form of "Auto Throttle/Thrust" or even "Glass". No idea how I survived??!!

Having back driven thrust levers on a modern Glass cockpit really doesn't make any difference to my life. I went from being a Half-Pilot to a Real-Pilot then back to being a Half-Pilot, A320->B787->A320. There is so much information directly in-front of you on the PFD, and the Engine instruments are a great back up.

Having all this Automation makes me very "Lazy".

Recently in the SIM, during a manual thrust exercise, the Instructor was talking about manual handling of the speed and the best reference for Thrust setting on approach. We have IAE which have EPR as the primary reference, fairly useless, but the N1 works well. We discussed the expected pitch/thrust for the approach. We all managed to regurgitate the "numbers" ie: 2.5º N/U with Thrust = GW-10%.

His next question was an eye opener. "How are you going to set the Thrust from then on?"

At this point I needed to re tie my shoelaces, and my mate had something important in his flight bag that needed to be repacked.

"THE BEST REFERENCE FOR THRUST SETTING IN A MODERN A/C IS THE AIRSPEED TREND VECTOR"

This is true for the Boeing, Embraer or the Airbus, regardless of the back driven Thrust Levers.

As far as the Airbus v Boeing thrust lever debate, I vote for the Table and Sidestick. ;-)
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Old 7th Jul 2021, 04:22
  #47 (permalink)  
 
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Agree with your instructor 100%. Get it in the ballpark, then do the rest with the ASI. If your instrument scan is good, you'll only occasionally need to glance at the N1, and mostly to make sure they are synched.
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Old 7th Jul 2021, 04:51
  #48 (permalink)  
 
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Smile

Or get a HUD
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Old 7th Jul 2021, 06:46
  #49 (permalink)  
 
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On final Approach hands should be on Thrust levers that's because pilots may not have to search for them when they are desparately needed and not because of anything else.That's not the cause of SFO. Any approach in any aircraft is doomed if no one is going to look at the speed at all. In Bangalore A320 was the same problem. Every few seconds the eyes must glance at the speed. That's what must be drilled and not so much the hand position. In a fully serviceable aircraft in VMC, flying 26kts(Bangalore) or 31kts below Vapp(SFO) is simply unacceptable. The pilots had lost the basic scan. In both the cases they didn't even check ATHR modes. How can You trust automation without even checking that it's in appropriate mode? The systems worked as designed but the pilots didn't fly as they were supposed to.

Last edited by vilas; 7th Jul 2021 at 07:09.
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Old 7th Jul 2021, 07:38
  #50 (permalink)  

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Combine symbology change with unusual attitude presented to a non-trained, fatigued crew right on the wrong side of WOCL: the mix has killed before ("B" Rostov). Could happen on any type. Just like speedtape confusion mixed with stomagravic illusion ("A" Sochi).

Thanks gentlemen. I went from a novice real-pilot to half-pilot 16 years ago. The transition was not a problem as I was trained on the 737 to watch my N1s. 1) Set the target, 2) check your V/S + speed and move the levers accordingly, 3) review and memorize the new N1 value. Noting extreme, scan the "T" once and then peak at the EIS, rinse & repeat.

Speed vector turned me to a lazy engine scanner over time, significant drop there once the EPR models came by. Eyes never learned to pick the N1 from the new location, I guess. My personal feelings about AB non-moving is beyond the scope of the thread.

Back to the scheduled programming, now that the obligatory hijack of a BA thread by AB semi-pilots is done, shall we? Before we do: The suggestion that Asiana disaster was majorly contributed by the training on an advanced previous model is absurd, moreover because that training (if done) actually reinforces the vital skills that were missing on the accident day. I threw in the pandora's box because the opinion re-occurs - how airbus experience unteaches the skills needed to survive boeing - while the exact opposite is true. Yes, there are organs that atrophy naturally and weathervane on the 'bus, airspeed control is not one of them, same as where your hands go.

Last edited by FlightDetent; 7th Jul 2021 at 09:15.
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Old 7th Jul 2021, 11:38
  #51 (permalink)  
 
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Judging by how many pilots of other types cannot seem to understand how the Airbus FBW and A/THR works, there is nothing "half" about being an Airbus pilot.

Why do some pilots find it so hard to simply look at N1/EPR gauges, instead of the position of the thrust levers? Both tell you exactly what the A/THR is doing, but moving thrust levers can become a proxy for the engine gauges, so the pilot's scan of their engine instruments gets forgotten. The levers are the input, not the engine output, so the engine gauges in any type need to be looked at anyway; witness Centaurus's SIM test where he failed a Boeing thrust lever and the crew did not notice, ending in a 'crash'.

Never mind which type one flies: one hand should be on the thrust levers during approach in case a go-around is required, or if the A/THR does not react correctly and/or manual thrust control is required. A turbulent day and an approach where manual thrust or TOGA becomes necessary is not the time to start trying to put your hand on the levers, it should be there already.

As regards only one hand on the (conventional) yoke: Is there any situation in which both hands on the yoke would be helpful? I can think of a few. Would there ever be a situation in which PF would ask PM for TOGA while he, PF, put both hands on the yoke to ensure correct pitch and bank and not overshoot?
For example, I always found it much easier and more accurate to do 60° banked level turns* if I had both hands on the yoke rather than one. Both hands also means both sides of the brain are used, and gives finer control.

* obviously a SIM exercise, not part of normal flying !
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Old 7th Jul 2021, 21:05
  #52 (permalink)  
 
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"Reportedly, due to the way the Boeing back drives the yoke on the 777, as Asiana was approaching stall the pilot was having to pull back on the yoke with something approaching 100 lbs. force. Not many people could have done that with one hand on the thrust levers..."

Tdracer, why were they pulling on the yoke while approaching the stall anyway?


Last edited by Pugilistic Animus; 7th Jul 2021 at 22:34.
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Old 7th Jul 2021, 23:14
  #53 (permalink)  
 
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Most people's intuitive concept of what the yoke does, has little to nothing to do with its effect on AOA and/or airspeed. It's considered simply for pointing the nose, and in turn, for pointing the flight path.
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Old 8th Jul 2021, 01:56
  #54 (permalink)  
 
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Indeed Vessbot... what you say is true about untrained people but these guys were pilots they should know about stall recovery.
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Old 8th Jul 2021, 02:49
  #55 (permalink)  
 
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Apologies for diverting this into another 'Boeing moving throttles vs. Airbus non-moving throttles debate' - that wasn't my intent. Rather I was trying to point out that I believe the differences training the Asiana PF received was inadequate - something I didn't see in the final report... The Boeing and Airbus design philosophies are considerably different - not saying one is better - but they are very different. That needs to be thoroughly accounted for in the training when switching between.
To understand the Boeing design philosophy for the autothrottle systems, you need to go back in time a bit. The original A/T installed on the 747 (FFRATS - Full Flight Regime Auto Throttle System) was an analog device and quite crude. It was simply intended to relieve crew work load on long haul flights, not to completely take over the task. Move on to the 757/767 A/T - which was digital and far more sophisticated than FFRATS, but had numerous potential failure modes (slipping lever clutches being a common one due to down-stream cable loads), and it was a single servo so could not control the levers independently. The software was only developed to DAL C (essential) - not flight critical - which was consistent with the rest of the system design. When we went to FADEC on the 767 and 747-400, the basic system didn't change that much from the original - getting rid of the throttle cables helped a lot (simple friction devices where added to the thrust levers to give 'feel' and prevent uncommanded movement since the force to move the thrust lever resolvers was minimal), and a 'trimmer' function was added to the A/T software that sent small adjustments to the commanded EPR/N1 of each engine to align EPR/N1 across the wing (to account for pilot induced throttle stagger or small rigging errors). But it was still single thread, with a single servo drive, and the s/w was DAL C. In short it was still viewed as an 'aid' and the pilot was still expected to monitor what it was doing.
The 777 got a completely new A/T relative to what was used in the 747-400/757/767 - dual servo so independent control of both engines, s/w was DAL B, but it still wasn't certified as a 'flight critical' function. On the engine side, we always had to assume 'worst case' - that the A/T could be lying and so we still needed provisions to disable it and ignore all inputs. We complained mightily that the A/T should be considered flight critical - that the pilots were starting to treat that way, but got nowhere.
My understanding - based on conversations with my cohorts who worked on the 787 - is that they finally designed the 787 autothrottle as a flight critical system. But I don't know details.
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Old 8th Jul 2021, 02:52
  #56 (permalink)  
 
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Pugilistic Animus

I don't think they realized they were about to stall until it was too late. The pilot kept pulling back because he was headed for the seawall. Four pilots on that flight deck, and only one noticed that airspeed was getting critically low and he didn't voice it strongly.
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Old 8th Jul 2021, 04:09
  #57 (permalink)  
 
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tdracer

Thanks as usual for your insight. I learned something new today.
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Old 8th Jul 2021, 04:10
  #58 (permalink)  
 
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tdracer

We'll agree to disagree on the number of pilots in the cockpit that day.
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Old 8th Jul 2021, 04:39
  #59 (permalink)  
 
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Interesting chronology thanks for that,

Still curious as to why the Toga and AT disconnect switches changed positions after the 757 / 67 ?
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Old 8th Jul 2021, 06:30
  #60 (permalink)  
 
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That I don't know - I was involved in the thrust lever design aspects - but only on the engine side, not the A/T side.
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