A320 family autoland

[dontdoit]

Just curious - what happens on an autoland on the A320 family if at the "Retard, Retard" call the thrust levers remain in the climb gate ?

[zonnair]

The "RETARD" is as a reminder only. The trust is at idle already, as long the autopilot remains engaged. ROLL OUT will follow, but no spoiler deployment hence no AUTO BRK function (and obviously no reverse as the levers are in CL detent)

You better retard the levers before you disconnect the AP, as A/THR is still active and will increase the trust conform the lever position.

[groundfloor]

Thats why it says "RETARD" leave it long enough and you are...:}

[HOTROD_0414]

Hey ZONNAIR Just tried looking in the FCOM regarding spoilers activation, in an auto land, in case one does not bring the thrust levers back from CL gate to idle and FMA shows idle, after touch down ground spoilers would not activate???
As the book says "IF THE GROUND SPOILERS ARE ARMED AND THRUST LEVERS ARE AT IDLE GROUND SPOILERS WILL ACTIVATE AS SOON AS LANDING GEAR TOUCH"

[NVpilot]

Hotrod, are you mixing up Thrust Lever position and FMA?

[TyroPicard]

HOTROD is correct.

[Right Way Up]

Are you sure TP. If the thrust levers are not @ idle position then the ground spoilers and thus autobrake cannot activate.

[DragStrut]

In a full autoland you are merely putting the thrust levers to where they should be as a confirmation of what the autothrust has already done for you ie its already at idle ...

[Right Way Up]

Yes Dragstrut that is correct. But the ground spoiler function is based on thrust lever position.

Full extension - Landing phase


If the ground spoilers are armed and all thrust levers are at idle, the ground spoilers will automatically extend as soon as both main landing gears have touched down.



If the ground spoilers are not armed and both main landing gears have touched down, the ground spoilers will automatically extend as soon as reverse is selected on one engine (the other thrust lever remains at idle).


Note : The spoiler roll function is inhibited when spoilers are used for the ground spoiler function.
Partial extension

The ground spoilers partially extend (10°) when reverse is selected on at least one engine (other engine at idle), and one main landing gear strut is compressed. This partial extension, by decreasing the lift, eases the compression of the second main landing gear strut, and consequently leads to full ground spoiler extension.

Retraction

The ground spoilers retract :


After landing, or after a rejected takeoff, when the ground spoilers are disarmed.


Note : If ground spoilers are not armed, they extend at the reverse selection and retract when idle is selected.


During a touch and go, when at least one thrust lever is advanced above 20°.


Note : After an aircraft bounce, the ground spoilers remain extended with the thrust levers at idle.
FOR INFO


The landing gear touchdown condition is triggered for both main landing gear, either when their wheel speed is greater than 72 knots, or when their landing gear struts are, confirmed to be compressed by the radio altitude (RA < 6 feet).

The thrust levers are considered to be at idle when they are :


Below 4°, when the RA is above 10 feet,



Below 15°, when the RA is below 10 feet.

Thus although thrust will be at idle the logic will not. Try it in the sim if you have a chance!

[TyroPicard]

HOTROD wrote after touch down ground spoilers would not activate???I say again, HOTROD is correct!

[Right Way Up]

TP,

I have probably misunderstood but the question marks and last sentence in Hotrods post make me think he believes ground spoilers will deploy with thrust levers in the CLB gate.

[TyroPicard]

I only read what he wrote - what he believes is not mine to guess. And what he wrote makes perfect sense.

[Beeline]

Spoilers will deploy in the following modes.

Ground spoilers automatically extend when armed:
- both thrust levers at forward idle and both MLG touch down (Flight /
Ground transition),
-during Take Off (TO) run at speed greater than 72 knots (kts) and
both thrust levers retarded at forward idle.

Ground spoilers automatically extended (not armed):
- when both MLG touch down and reverse is selected on at least one
engine (remaining engine at idle),
- or during TO run speed greater than 72 kts and reverse is selected on
at least one engine (remaining engine at idle).

Ground spoilers partially extend:
- when reverse is selected on at least one engine (remaining engine at
idle) and one MLG is compressed.
This partial extension (10degrees) by decreasing the lift, will ease
compression of the second MLG, and consequently will lead to the normal
ground spoiler extension.

Thrust Reversers
SECs and EEC must have TLA below -3degrees for thrust reverser deployment and RA <6ft, this data is from the potentiometers of the throttle control unit and Rad alts respectively.

Regards
Beeline

[mcdhu]

Hotrod and Tyro are absolutely correct. If someone does not close the TLs after touchdown on an autoland, you will drift off the end of the r/w doing somewhere around 100KIAS with Pierre shouting ''(you) RETARD''.

Done regularly in the sim to prove to disbelievers who don't know their tech.

mcdhu

[HOTROD_0414]

Thanks Guys. Just read the FCOM 1.27.10 there's a NOTE which says " IN AUTOLAND, GROUND SPOILERS FULLY EXTEND AT HALF SPEED ONE SECOND AFTER BOTH MAIN LANDING GEARS TOUCH DOWN"

Very clearly as per this, in autoland TLA position has no meaning. Correct me if i am wrong.

[mcdhu]

I don't have access to the FCOM at the moment, but I am telling you what actually happens in 4 different A320 sims.

mcdhu

[Right Way Up]

Hotrod,

Can you confirm you are reading from the A320 series FCOMs, as I concur with MCDHU. In the last 12 years on the A320 I have never seen this line. I also have this view backed up by 4 different sims although they might well be the same ones MCDHU uses.

[Thunderbug]

Interesting debate guys...

Just checked my FCOM 1 and that note is included, but of interest is that the note appears applicable to only the A320, but not the A319 or A321!

T'Bug:ok:

[The Flying Cokeman]

Thunderbug is correct. The difference is whether we are talking about the 319 or 320 (sry I don't fly the 321).

On the 319, spoilers do not come out until you retard the thrustlevers on an autoland (although engines are already at idle). The 320 does as earlier mentioned, come out slowly when both landing gears have touched down.

[NVpilot]

Thanks for that Hotrod.

[Right Way Up]

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.

Full extension - Landing phase


If the ground spoilers are armed and all thrust levers are at idle, the ground spoilers will automatically extend as soon as both main landing gears have touched down.



If the ground spoilers are not armed and both main landing gears have touched down, the ground spoilers will automatically extend as soon as reverse is selected on one engine (the other thrust lever remains at idle).


Note :

In autoland, the ground spoilers fully extend at half speed one second after both main landing gears touch down.



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.

[mcdhu]

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

[stilton]

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.

[Dan Winterland]

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.

[Meikleour]

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.

[mcdhu]

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

[HOTROD_0414]

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

[Meikleour]

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.

[stilton]

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.

[mcdhu]

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.''

[Dan Winterland]

''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.

[zonnair]

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

[zonnair]

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

[slast]

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.

[TyroPicard]

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!

[stilton]

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 ?

[Dream Land]

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.

[slast]

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.

[stilton]

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.

:}

[TyroPicard]

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.

[slast]

<All pilots should include the EPR/N1/whatever you like to use in their scan> absolutely correct.

However, one thing we were trying to establish was the influence of non-instrument information cues in overall situational awareness. The survey we did got responses from 70% of the pilots on the fleet at the time - about 100 in all. One thing that came out was that some pilots make very little to no use of non-instrument information, but most use SOME peripheral cues. Thrust lever angle featured high on the list of cues for power demanded, and engine noise for power delivered. We concluded that neither existing concept as currently implemented was an ideal solution that would satisfy 100% of pilots 100% of the time. Some pilots will be very satisfied and others somewhat dissatisfied with either system. It's simple human factors - everyone comes with a different set of learned cues from experience so reacts slightly differently to new circumstances.

If there is any demand for it I can make this paper available but, it isn't going to result in any changes to system designs!

[rudderrudderrat]

Hi Slast,

Please may I have a copy of your paper.

I have a similar exposure to autothrust as TyroPicard - but even after 6 years on Airbus, I still miss the tactile feedback of moving thrust levers.

It would be interesting to see if there was any difference to crew recognition time and subsequent control, when managed speed is selected before the Approach phase has been activated.

[Dani]

and I fly moving AT levers now and still stand under the impression that it's useless: Those mechanical gimmicks move, but they are never accurate enough, thrust lever movement is not always symmetrical, and it doesn't always correspond to the indication of the engine display.

I admit, I grew up with Airbus (after years of turboprops without anything). I don't need tactile feedback since I know that Airbusses always take that speed you program it. And because their TL are so simple to set, I'm sure that they give me the thrust I really need.

Dani

[NSEU]

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.

Not sure what you mean by backdriving. On a Boeing, the A/T computer commands thrust lever movement and EEC/engines respond to that movement.
The pilot can intervene with or without A/T disconnection. i.e. a simple chain of command with the pilot always in the chain.

I'm sure if Boeing put their minds to it, the thrust levers/clutchpack could be made as small as Airbus thrust levers (so no weight disadvantage). The servomotor is not what you would call heavy.

Rgds.
NSEU

P.S. Sorry for the thread drift.

[stilton]

Yes Tpicard,


This 'closed minded' Boeing and Douglas Pilot has an opinion different to yours.



If you had read my comments a little more carefully you would have realised my statements were not an attempt to criticise Airbus but an attempt to elicit professional opinions from those with experience of such.

[slast]

rudderrudderrat
OK... how do I send it to you? Does this forum support file uploads or do you want to send me an email address?