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Flying below VAPP - What to do ?

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Flying below VAPP - What to do ?

Old 12th Aug 2015, 06:30
  #41 (permalink)  
 
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These 3 pages alone tell the real AT HF interface story

After having flown, tested, or evaluated all four big jet manufacturer's types in some of the most stressful conditions or configurations experienced within the flight envelope, and some times in ranges beyond the edges, ...for nearly four decades, ... these three pages of comments alone, addressing this simple question, ...provide a "telling story" regarding the suitability and characteristics of the modern Bus non-moving throttle design. In that regard, these three pages of comments alone are all that's needed, to begin to draw conclusions about the real story, of both the suitability, strengths, and weakness of that particular pilot-aircraft thrust/speed interface. It should be as simple as either AT ON, or alternately push forward for more thrust, and pull back for less, as needed, ...if the AT isn't doing what you expect or need. Even the issue of electing to disconnect the AT, or not, is secondary.
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Old 12th Aug 2015, 06:56
  #42 (permalink)  
 
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This Airbus thread is squawking 7500.

Last edited by vilas; 12th Aug 2015 at 08:42.
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Old 12th Aug 2015, 07:38
  #43 (permalink)  
 
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I have to say in some way i do agree with 7478ti. After switching to the airbus i sometimes missed the in-between way of dealing with slow or non-behaving autothrust on boeings. If it is to fast pull it back a bit and then let it continue on its own, or push it forward somewhat and then let it continue on its own.

On the bus i have to disconnect it completely, after i have to sync the thrust levers to the current thrust level first. It is somewhat more cumbersome. Interestingly enough 99% of us do fly (nearly) always in manual thrust when in manual flight as a result of that. In fact, some have to do the odd autothrust on approach to keep current in this kind of operation. It is just much easier to fly manually in manual thrust, but that is of course my personal opinion. Even manual thrust in automatic flight sometimes works better than both in automatic.
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Old 12th Aug 2015, 11:46
  #44 (permalink)  
 
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Zenj,

Regardless of whether you're legit or not, I don't think this is a place to learn much of anything anymore (I'm not sure it ever was). This is cheap entertainment, sometimes even pretty good entertainment.
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Old 12th Aug 2015, 12:15
  #45 (permalink)  
 
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The german philosophy (in LH and others) is to disconnect the A/THR every time disconnect the AP. No matter what Airbus says. I kind of like that.

On the bus i have to disconnect it completely, after i have to sync the thrust levers to the current thrust level first. It is somewhat more cumbersome.
one going manual thrust should be done before 1000ft according to Airbus.
The problem here is that we don't have freaking options when we face that situation!

The A/THR is not doing the job? Disconnect… No, wait! It is too late to disconnect already, So… What the f*** do we do??

Answer: Go around.
That is what it all comes to: go f****n around. No other options. So in this regard, it is clear that the autothrolle system of Boeing is superior. It gives more control. I have to admit it.
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Old 12th Aug 2015, 13:22
  #46 (permalink)  
 
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On the 319 it is nearly a "standard procedure" to add 2 -3 kts extra on the Vapp, as it does not hold it's speed. Does not matter even if in fairly calm conditions! It will even fluctuate/flicker below Vls if nothing is done. I personally prefer NOT to sit and wait and see what might happen or how low it might go, as I am not paid to be an Airbus test pilot!

The ATHR disconnect in the FCU does work, it goes momentarily into THR LOCK until engaged again.

I never saw this problem on the A320 with IAE engines, but I did see it also on the A320 "sharklets" with CFM engines.

No idea if any connection between this, just my observation.
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Old 12th Aug 2015, 15:14
  #47 (permalink)  
 
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I don't see why so many people get het up about non-moving thrust levers. If A/THR engaged, you don't move them, if in manual THR, you do move them. This the same principle in both both Boeings and Airbuses.
Bottom line: Monitor A/T response; if this doesn't work, use manual thrust.

The two or three most significant & well-known accidents/incidents I can think of where crew failed to monitor approach speed, and assumed the A/THR was working when it wasn't, were all Boeings. So what does that say about the benefits on moving thrust levers? (Asiana @ SFO, Turkish at AMS, Thomson at BOH, 2009)
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Old 12th Aug 2015, 15:27
  #48 (permalink)  
 
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Agree with GL. Airbus FBW A/THR does encourage a proper instrument scan.
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Old 12th Aug 2015, 17:05
  #49 (permalink)  
 
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Ref GL and (Asiana @ SFO, Turkish at AMS, Thomson at BOH, 2009)

True... any airplane can be improved, even the T7 ...and any FCOM or FCTM or pilot qualification program can better cover more of those 1x10E-4 or less probable situations that we often see "once a week", ...it's just that some airplanes can benefit much more from improvement due to chronic weaknesses than others.

It would take many more than three pages here, and citing a mere three examples, to comprehensively address this "non-Moving throttle" and AP/AT disconnect subject. An entire FAA report was dedicated to subjects like this (back in 1996), and it still stands. In fact, hardly anything has changed on this non-moving throttle issue since those very first discussions with advocates like Gordon Corps, PB, and B Zed, ...on the troubling HF aspects of this subject, that began at least in the early 80s. I still vividly remember those meetings, and the predictions of the inevitability of this entire discussion.

Jun 18, 1996 - Federal Aviation Administration. "The Interfaces Between Flightcrews and Modern Flight Deck Systems".

Last edited by 7478ti; 12th Aug 2015 at 20:17.
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Old 12th Aug 2015, 22:23
  #50 (permalink)  
 
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Guys: there have been various opinions voiced here about the ATHR systems and some of their idiosyncrasies. Some have outlined their weaknesses and slightly inconvenient characteristics. I've expressed my thoughts on complicated non-moving ATHR systems. An attempt to reinvent the wheel. But, a further observation; guys have suggested 'work arounds', 'tips & tricks' to bypass the basic design and overcome the unwelcome quirks. If that is the case then surely it says that the original design is not correct and should be re-done? It's not healthy to have a weak system design and allow random crews to devise their own working solutions, while others follow the manufacturer's ideas and fall into the lurking traps.
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Old 12th Aug 2015, 22:32
  #51 (permalink)  
 
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Hi RAT 5,
If that is the case then surely it says that the original design is not correct and should be re-done?
British Airways Airbus A320 Pilots' Autothrust Survey
"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."
Steve Last & Martin Alder.

We've been waiting since 1991 - so don't hold your breath!

Last edited by Goldenrivett; 12th Aug 2015 at 22:44.
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Old 12th Aug 2015, 22:46
  #52 (permalink)  
 
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Might very well work better

That BA based pilot suggestion might very well work better (i.e., less bad), particularly if the FHA, FMEA, and SSA was carefully done, and the conclusions supported that change... good comments by both RAT 5 and Goldenrivett!

But I also concur... "Don't hold your breath!". I've been dealing with Busses and waiting for that change of heart, and philosophy, since at least the first A300B2K in the US back in the 70s, ...and then later waiting, since at least those 1982 conceptual discussions, for a better thrust solution, and sidestick interconnection solution, and soft limit solution, ...since well before the first AutoBus even flew !

[Also see the other PPRuNe parallel thread, about recent A320 speed mgt issues]
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Old 13th Aug 2015, 10:03
  #53 (permalink)  
 
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I wonder if the faults/short-comings being exposed can be traced back to the operational design philosophy. A B732, even 733/4/5 were designed to be sturdy workhorses and could fly into some inhospitable tiny places and also the large cosy nests of major hubs. They, later models, even had LNAV/VNAV and could autoland. I wonder if the AB's FBW started life with a clean sheet of paper and were envisaged to be flown into major hubs with autopilot + auto throttle down an ILS to minima and then the human intervened; or autoland. It was designed to be an automatic pilot monitored a/c from immediately after takeoff to immediately before landing. It was route tested as such. OK, it had to jump through the various certification processes for VMCA/G stalls etc. but largely it was operated via automatics.
Then it was sold outside its design nest and replaced many of the older simple Boeings on routes outside major hubs. Adventures arrivals into nasty weather/winds Greek islands: tiny mountainous terrain infested airfields, all of which involved human intervention long before "immediately before landing". Mk.1 eyeball arrivals with hand on stick. Scare Blu!
Those with much more experience of AB's, and perhaps those with experience on both AB & Boeing, will inform us which is the easier/better to land in nasty gusty X-winds. Speaking to easyjet friends who flew both, it was common to want AB on smooth days and Boeing on nasty ones. What is the consensus? They should both be able to do both adequately. But having seen some videos of PIO on short finals the side stick brigade seem to have it much harder to keep the bucking bronco under control and not be spat out of the saddle.
There was a significant difference in B737 family & B767 on nasty days. The control column was much calmer in the larger a/c. B733 was stirring the pot; B767 more gentle inputs. How is it from A319 - A330/340/even 380. I suspect the large super whale might treat mother nature with some disdain, or is it still a handful? It will be interesting to hear, after many years of line experience, just how the revolution has succeeded, or not. In the early days of AB FBW, on Prune, there was an ongoing debate of the B757 v A320. There were definitely 2 camps. How now?
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Old 13th Aug 2015, 10:23
  #54 (permalink)  
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I feel sorry for you lot having never flown the E195 which has the best AT system ever.
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Old 13th Aug 2015, 12:39
  #55 (permalink)  
 
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Hey RAT, that is interesting, there might be a lot of truth in what you suggest, I don't know.

For what it's worth, my two penn'orth is that in my experience, Airbus is very poorly taught. They are so keen to get us into the air and learn how to do ECAM, that basic handling stuff is really glossed over, and in my case was not properly taught at all. All that was said about the side stick were really stupid things such as "pretend it's a docker's dick and don't touch it unless you have to", or "only hold it at the top" or "only hold it at the base", and other such useless comments which did nothing to actually explain how to use it. We have never been taught or shown how to do turbulent approaches in the SIM or for real. PIO's on FBW Airbus are therefore mostly a result of poor training in my view. I eventually taught myself how to use the side stick correctly - after watching a video of a Tornado pilot. Years later I explained how to use the side stick to a TRE who had trained me !

The one thing you cannot do in an FBW Airbus is 'follow through' on the controls - i.e feel what inputs the trainer is making - since the sidesticks are not mechanically linked. This is a shame because that is a valuable way to learn to handle a plane.

I have not flown Boeing apart from in the SIM, and my previous types were non auto thrust. However, from a handling point of view I did fly the BAe146, and many was the time I could feel myself overiding the servo tab controls and hitting the mechanical stops on the control surfaces when I needed to reverse control direction as I flew a turbulent approach. I have never needed to do this on an Airbus - well of course it's hydraulic not servo tabs - and you just centre the stick when your input starts having an effect. So I probably find the Airbus easier than the dear old 146. The Airbus side stick needs a different method and the knowledge that the FBW is helping you and doing some of the work for you.

I have flown A320/321/330, and their response is similar thanks to FBW, but the 330 is obviously much larger, has more inertia and is less upset by the atmosphere, like any large aircraft.

The idea of a hybrid system of having moving thrust levers from Idle to CLB and then detents for MCT and TOGA is interesting. Of course we must bear in mind that even moving thrust levers are the input, not the output of the system - which can only be seen on the N1/EPR gauges, so a scan of the engine instruments is still required. You can select the engine instruments onto your ND in the A330 which makes the scan easier on short thermally finals if the A/THR is being lazy', though it is not SOP.

Last edited by Uplinker; 13th Aug 2015 at 12:58.
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Old 13th Aug 2015, 13:29
  #56 (permalink)  
 
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Very real differences

RAT. Excellent comment.

I cannot speak to the 380 at all (no experience with it)... , but after at least three decades of dealing with both, for all the other AutoBusses and their comparable Seattle products through the superwhale and plastic jet, there are very real differences in both philosophy, as well as control system design (as well as FMS/FMF). These lead to meaningful differences in performance in difficult WX conditions reference limits, margins, phase margin, gain margin, and vulnerability to PIO/APC. With firsthand experience in the most difficult of conditions, there were days where I'd be quite comfortable operating with one, and wouldn't even consider anything but parking it, or a diversion if airborne, with the other.

As to the subsequent E195 AT comment by CM... note that an AT alone, ...without an also excellent RNP, GLS, and a capable FMS/FMF is pretty useless. No E195 can yet even come close to touching a Cat III LAND3 while handling an unexpected a 40kt gusting XW, with an engine shutdown, or RNP .1 into or out of PAJN, NZQN, CYLW, or ZULS with a first E/O, or lightning strike electrical bus shed... and never will, at least not with their current Piper Apache 1950s vintage systems and flight control architecture, and primitive FMS.
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Old 14th Aug 2015, 00:58
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Simple fact is Airbus FBW is a different philosophy. It is completely different from the trainer aircrafts a pilot learns his craft on. It is not only thrust but vector stable behaviour also is different than what you get to learn during your transition to commercial pilot. It all started in 1988 and the order book of airbus in 2015 is pretty impressive. That shows this philosophy is here to stay and is successful. It may not be technically and commercially possible to mix and match different concepts and commercial success obviates any need for that. Humans will always like and dislike things. It is a good topic for discussion but non airbus pilots or who detest it's concept should not hijack every topic airbus pilots are discussing towards their favourite past time of airbus bashing. Because it defeats the purpose of the original post. Start a new thread by all means. Also the opponents add nothing new and keep chewing the same bones.
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Old 14th Aug 2015, 04:17
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Pilots still move between types...

With all due respect sir, pilots still routinely need to move between types, and they deserve to know the truth about what they're seeing, and why. That knowledge void, and those kinds of HF interface differences, was a main cause of the A300 accident at Nagoya decades ago, and that directly led to the 1996 FAA/Industry HF team Report (see below).

On 26 April 1994, the Airbus A300B4-622R was completing a routine flight and approach, when, just before landing at Nagoya Airport, the First Officer inadvertently pressed the Takeoff/Go-around button (also known as a TO/GA) which raises the throttle position to the same as take offs and go-arounds.

"The Interfaces Between Flightcrews and Modern Flight Deck Systems"
June 18, 1996
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Old 14th Aug 2015, 05:36
  #59 (permalink)  
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Originally Posted by 7478ti View Post
As to the subsequent E195 AT comment by CM... note that an AT alone, ...without an also excellent RNP, GLS, and a capable FMS/FMF is pretty useless. No E195 can yet even come close to touching a Cat III LAND3 while handling an unexpected a 40kt gusting XW, with an engine shutdown, or RNP .1 into or out of PAJN, NZQN, CYLW, or ZULS with a first E/O, or lightning strike electrical bus shed... and never will, at least not with their current Piper Apache 1950s vintage systems and flight control architecture, and primitive FMS.
Well I'm pretty sure the discussion was about AT behaviour. The Embraer still beats the others hands down at that but it must be useless because it can't CAT III auto land OEI in a 40kt crosswind (what can?).

I'm also reasonably certain that when I was doing GNSS only approaches on it the RNP/ANP was probably quite small.
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Old 14th Aug 2015, 07:18
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There was a significant difference in B737 family & B767 on nasty days. The control column was much calmer in the larger a/c. B733 was stirring the pot; B767 more gentle inputs. How is it from A319 - A330/340/even 380
The 767 has excellent control authority (notably in roll), and rarely needs coarse inputs to keep it on the straight and narrow. For me, the problem with the A330/340 (can't comment on the other Buses) is the amount of lag in the flight control system. You simply don't have the sense of a direct and immediate connection with the controls. Again, this is most obvious in roll. When everything's smooth there's no problem, but it makes things a bit busy and unpleasant in the rough stuff. I can live with the non-moving thrust levers, but the autothrust system is slow to react and then applies excessively large inputs. This means it does things for which a human pilot would deserve a smack over the knuckles with a ruler (e.g. idle thrust at 150' due to a few excess knots).
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