Have looked further at our FCOMs and I notice that Hotrods line is indeed on the IAE 320 but not the CFM 319 & 320 or IAE 321.

I cannot be sure, but my understanding that the thrust levers still need to be idle, but the ground spoilers will extend in a different way during autoland.

Just had a look at the latest FCOM CD for one of our newest CFM A320s.

The note is indeed as Hotrod describes on 1.27.10 P12 but only as a Note in Flight Controls - Ground Spoiler Control - Full Extension Landing Phase.

While I agree that it is as Hotrod describes, as with other deficiencies of the FCOM, it is less than clear that this note is not a full desccription of the deployment conditions, but rather only a note to tell you when (in time) and at what rate the Gnd Spoilers deploy during an autoland.

I stand by my earlier statement - and those of others - that the TLs must be at idle for the Gnd Splrs to deploy and hence for autobrake to work.

Cheers all,
mcdhu

This is not an attempt to bash Airbus but seriously can any Airbus Pilot name one real advantage of having non moving Autothrottles ?



It seems most counterintuitive to me and a constant 'gotcha' in waiting if you confuse what 'mode' you are in.

I can't think of many advantages, but I can't think of any disadvantages either. Personally, I find them good. You just have to change your mindset if coming from a Boeing.

If the AT is in, you just treat them as the thrust limit selection switch and let the FMGS do it's work. And having the switch move in the correct sense rather than having to use the rather confusing THR switch on the MCP of the Boeing is a big plus. If you want to use man thrust, then they work just as any other aircraft. The fact they don't move with the power setting with the AT in is fairly inconsequntial and I have found in over 3500 hours of bus flying that I haven't missed that.

One small advantage I can think of is that on the take off roll, you get the thrust you ask for and if not set correctly, you get ample warning. Remembering the Bus takes off in manual thrust, AT is only armed until thrust reduction altitude when Climb is selected. Personally, I was never that happy with the way Boeing managed the thrust on the take off roll. You could manage it yourself by overriding the clutches, but it was one more thing to worry about at a critical part of the flight. Have a look at the thread regarding the Air France RTO at Lagos in Rumours and News to see how it can go wrong.

Hotrod`s quoting out of context would mean that on an autoland there would have to be some additional circuitry which DISREGARDED the usual thrust lever position sensors! I think not!
PS Airbus rated since 1994 (A330, A340, and currently A320 family.

Interesting point you raise Meikleour and I see what you mean, but there is such a difference already. On a normal manual landing, how does the thrust get to idle? - answer: the pilot puts it there by closing the TLs. On an autoland, the FMGC commands the thrust to idle at a height known only to itself and then invites you to follow up with the TLs at 10' RA by shouting 'RETARD' at you thus allowing Gnd Splrs, Autobrake etc.

How does the ac know to do this? Answer: with 'LAND' annunciated and at least 1 autopilot engaged, that is what it will do.

This begs the question what would happen if you didn't close the TLs on a manual landing. Well as the unfortunate TAM pilots discovered too late at Congonhas (Sp?), since you are in speed mode, the thrust will come on to try to maintain Vapp as you flare and when the wheels touch, the A/Thr will disconnect and leave you in Thrust Lock perhaps with Clb Thr. Messy.

Interesting debate, this one.

Cheers
mcdhu

Just checked again. It is only valid for A-320 and not for 319/321.

MCDU: rather than trying to unravel the FCOM script (ie. written by a frenchman and translated into english by a german!!!) look instead at the flow diagram. This has AND and OR gates and you will see that you cannot satisfy conditions for groundspoiler deployment without either IDLE on the thrust lever positions or selection of one engine into reverse. Thrust to idle during an autoland is an autopilot function via the FADEC and not related to the spoiler deployment.
Regards.

I think I have a vague and basic idea of how the Airbus AT system works but I still don't see the point.


Why should you have to 'think of them as thrust limit switches' Throttles are and have always been a very basic control since the dawn of Aviation. What was the point of changing that ?


A backdriven, moving autothrottle system is a natural and constant reminder of the commanded engine thrust. You don't have to 'think' of it as anything other than what it is.



As you say Dan, there don't seem to be any advantages to the AB system. I don't really see the problem with the Boeing system either so I suppose you can get used to it.


I do think the Airbus system is still, potentially more confusing and pointlessly so.

Meikleour,

I think we are in agreement. Thrust is set to idle by the combination of FMGC, A/Thr and FADEC. Spoiler deployment is a function of the TL position - and a few other things. Good innit!

Cheers
mcdhu
PS I went from clockwork 146s to the 'bus (some years ago) and, because I have never experienced TLs that move under the influence on Auto Thrust/Throttle, it has never been a problem to me. I guess it is what you are used to. ''Pilots like what they know.''

''Why should you have to 'think of them as thrust limit switches' Throttles are and have always been a very basic control since the dawn of Aviation. What was the point of changing that ?''

Because when AT is engaged, the TLs are redundant. Airbus has effectively added another function to them. It's more logical to move the TLs back a notch to engage climb thrust at the acceleration altitude than to accept what the FMC commands. At least you have the option of delaying it if you are in turbulence, or you just don't want it at that stage.

"I do think the Airbus system is still, potentially more confusing and pointlessly so''.

Not when you get used to it. And it took me about the same time as it took to get used to the side stick - about thirty minutes. I take it you haven't flown the Airbus. I like it and think it's better system than the one in the than the only modern Boeing I've flow (the 744 with GEs) which was not that special with regards to thrust management.

HOTROD.

You are absolutely right!!! spoilers will deploy if you play with the levers. The situation, however was that the TL are still in climb detent.

Sorry for the late reply

This half deployment of the spoilers on the 320 only is a pretty nice feature to make sure the the MLW is in possitive contact with the ground and will maintain that. (We don not have it on the 330), but i doubt however that it activates the AUTOLAND.

yours zonnair

reply to stilton: Moving lever pros and cons
 

FYI: SAE (Society of Automotive Engineers) Paper 912225 "British Airways A320 Pilots Autothrust Survey" (by Steve Last and Martin Alder) addressed this back in 1991.

BA was considering several new types for a fleet replacement programme and would have been a launch customer for the chosen one from A330/340, MD11 and Boeing 777. Given the somewhat heated moving/non-moving thrust lever controversy at the time, there was a question as to whether conventional "moving levers" should be a "Master Change" requirement with Airbus or "Fixed levers" with MD and Boeing. BA also happened to have ended up as A320 launch customer via its acquisition of British Caledonian after BCAL had ordered the A320 but before delivery. However none of BA 's top management pilots had experience of the A320.

As BA's A320 crews came from types with a variety of autothrottle systems it was decided to analyse their reactions to the various aspects. The author was at the time current on A320 and B757, the two most "advanced avionics" types on the market at the time. The conclusion was that "the A320 design provides advantages with respect to engagement and selection of rated power settings, and that (lever) movement provides better disengagement and information on system function". Personally I would still adhere to that view that both systems have their pros and cons.

BA's Flight Operations perspective was then that ideally, future systems should provide movement between the idle and climb power positions whilst retaining the A320 thrust setting and engagement "detents" technique.

Subsequently BA became launch customer for the B777. No master change requirement to the thrust lever system was called for: it was considered that neither system was perfect but both were more than adequate.

Provided the conditions are met....
Manual landing: the ground spoilers will automatically extend as soon as both main landing gears have touched down.

Autoland: the ground spoilers fully extend at half speed one second after both main landing gears touch down.

Simple, innit!

Ok, but what is the point of making the TL'S redundant ?


So you manually retard them to set climb thrust, how is that an advantage ?
on the 75/6 climb thrust can be set by selecting VNAV or FLCH or manually on the thrust computer.


It's just a different action for the same result, if you want TO power for longer you can easily reselect it.


I just cannot see any advantage. On the other hand I have never flown an Airbus so I suppose you can get used to anything.



The sidestick is a different subject. I think it's probably an advantage and quite comfortable to use.


From what little I know it can be a bit of a challenge in gusty conditions ?

Not saying the system is better than what you are using, especially considering my lack of Boeing time, but getting used to the bus is quite easy, the system works well IMO.

Stilton, the biggest advantages are not to do with flight ops directly, but engineering and cost. It's the reduction in mechanical stuff (weight, complexity, failure mode analysis/risks etc) that come from not having to create a back-driving system for a system (FADEC) that doesn't otherwise actually need it. And the comments from guys who were never accustomed to back-driven ATS levers shows that in that sense they were right - it's not essential. It's just another set of solutions. It just wasn't thought of first.

I understand it's an 'advantage' in weight saving for the manufacturer. As a Pilot, however, my un Airbus trained brain can still not see the benefit of removing what I consider to be a vital, dynamic, mechanical cue. If the power setting is changing the throttles should move.


Non moving autothrottles just seem to be another example of Airbus Isolating and removing Pilots from the loop.


Anyway, thanks for further educating me.

:}

stilton
Your profile does not indicate whether you are a pilot, or if you are what type you fly .. but I don't need a profile to realise that at times you operate with a closed mind. I will try to open it however briefly ..

I have flown airliners with manual throttles, moving autothrottles, and Airbus non-moving Autothrust levers (in that order). I reckon the only time that a moving autothrottle is really useful is when hand-flying an aircraft with conventional controls that requires manual trimming in pitch - e.g. B737 which has a large thrust-pitch couple. Pilots develop an instinctive response on the controls to autothrottle movement. Airbus FBW Normal law does pitch trim for you and that tactile cue is not required.

All pilots should include the EPR/N1/whatever you like to use in their scan - it is the dynamic IAS/RoD/CONFIG change situation that makes me check for correct autothrust response, not the autothrottle lever movement. To respond to lever movement by looking at the N1 means that your brain is behind the a/c.