Non-moving Auto-Throttle (Airbus... and others ?)

[leonard17F]

Hello Fellow PPruners....

For the Airbus drivers out there, do all models have a non-moving auto-throttle ? In all phases ? (T/O, Retard, Go-Around...)
How do you like it ? (In particular if you compare it to a moving one ?)
Do you believe that you may lack something, a clue that something is happening to the engines in some phases or is this behavior clear and self-explanatory enough ?

[Fursty Ferret]

Doesn't bother me after 9 years flying the A320. You just learn to keep the N1 gauges in your scan (EIS2 shows commanded thrust and a trend vector), and a lot of it's instinctive (ie negative speed trend and no thrust vector means trouble).

[Meikleour]

Pull up a chair - this should be good!

[slast]

If you are interested I have a paper based on a survey that was done in 1991 on our A320 fleet. At the time my airline was trying to decide on future fleet orders and was considering A330, B777 and MD11 as options. None of the senior flight ops management had flown the 320 and they wanted to know whether they should make a master change requirement for moving thrust levers if we went for the A330.

Based on a survey of all the pilots on the fleet, the conclusion we came to was that there were advantages and disadvantages to both Boeing and Airbus approaches and an ideal autothrust system would combine the best of both. "....a design similar to the A320 but modified to incorporate thrust lever feedback between the idle and climb power positions, and the ability to modify the autothrottle output temporarily without disconnecting the system."

This was the basis of a paper for the SAE. I can send it if you want it.

[Goldenrivett]

Hi deadcut,
Yea the moving thrust levers were very helpful to OZ214, EK521, TK1951 etc

Until those accidents, I was convinced that moving thrust levers helped crew's SA with regards to thrust. I think those accidents simply prove that some crews don't benefit from the tactile feed back.

However, to address the balance, here's one from AF A320.
Deviation below manoeuvring airspeed on final, go-around, triggering of Alpha Floor protection (https://www.bea.aero/docspa/2012/f-pe120403.en/pdf/f-pe120403.en.pdf)

I would like to think that moving thrust levers would have alerted the crew earlier that idle power was being selected by the autothrust - but I can't prove it.

Active side sticks (rather than passive Airbus types) would also have helped. But that's for another thread.

[tdracer]

do all models have a non-moving auto-throttle ?
All current production models do (everything A320 series and on). The A300 and A310 had moving throttles not dissimilar to Boeing.

[Denti]

In fact Airbus thrust levers are moving, just not moved by a servo but rather by the pilot. Yes, in normal flight with autothrust on they are in the CLB or MCT detent and don't move from there. However, in manual thrust they work like any other thrust lever too, just quite a bit more sensitive.

And what i think is much more intuitive is the go around case, just put them full forward and you are in go around mode (in the air) and you will get the thrust, even on the ground. Much more intuitive than the TOGA buttons on the boeings that may or may not work depending on where you are.

Of course moving thrust levers do have advantages too, not necessarily in SA, but one can easily intervene in autothrust operation if otto is doing something stupid (again). That is a much less intuitive task on the bus in my view.

And to answer the OPs question, they have to be moved during take off, go around and retard, there is just no servo to do it for you. Intuitive enough for sure, and thrust lever position on a boeing does not tell you thrust either, it just tells you thrust demand, not if it's met.

[Check Airman]

It's something that you quickly learn to adapt to. I prefer having the thrust levers move though, as that tactile feedback is another potential barrier. Yes there have been accidents on planes with moving levers, but how many incidents accidents were prevented because the levers moved? We'll never know.

[goeasy]

In fact, I believe AB fixed thrust lever make things much safer, because you actually follow the N1 gauge more closely, (actual thrust) rather than selected thrust from TL position.

[Check Airman]

How often does the actual thrust not match the selected thrust? Not saying it can't happen, but I've never experienced it, nor have I come across anyone who's said he's experienced it.

[Capn Bloggs]

In fact, I believe AB fixed thrust lever make things much safer, because you actually follow the N1 gauge more closely, (actual thrust) rather than selected thrust from TL position.
Just what you want. On a wild and wooly day, power going up and down like a whore's drawers, you're working overtime just to fly the thing, now you think it's it a great idea that you have to look at the N1s all the time to see what's going on with the thrust? No thanks. Give me moving throttles any day.

Check Airman +1.

[ElZilcho]

Honestly, both have their pro's and cons.

I do prefer the TOGA "detent" on Airbus, but for day to day flying I'm more in favor of the all moving levers.

Coming off multiple Boeings onto the A320 it did my head in for a few days, but was surprised how quickly I got used to it. After all, regardless of type, we should always keep the N1/EPR in our scans anyway, regardless of TR position.

That being said, the A320 does some silly things at time. If it levels off just prior to a decel point it'll firewall the thrust to level out then just as quickly command idle for the decel. Easily avoided with some FCU manipulation, but still, I find VNAV on the Boeing does a much better job.

[vilas]

There is nothing good or bad in absolute terms. Aircraft are built on design philosophies and we fly them according to those. Pilots, humans as they are have managed to beat all philosophies and protections and have been involved in accidents/incidents. What one prefers is a personal opinion, a personal comfort zone. But adaptability is great human virtue and the reason for it's survival when Dinosaurs could not. So pilots manage to handle whatever a system expects them to. B777 Dubai, SFO are examples that moving throttles is not a panacea. While there are at least three incidents which easily could have been accidents where airbus pilots didn't push it fully to TOGA position, remained in approach mode and came dangerously close to ground . Bad piloting has no favourites. Off course why a pilot did what he did may have other reasons.

[Uplinker]

Just what you want. On a wild and wooly day, power going up and down like a whore's drawers, you're working overtime just to fly the thing, now you think it's it a great idea that you have to look at the N1s all the time to see what's going on with the thrust? No thanks. Give me moving throttles any day.

It's really not that difficult, and is honestly not an issue. You don't have to look at the N1s "all the time", just occasionally, as I'm sure you do even on types with moving levers. There are other cues on Airbus FBW types, such as the speed trend arrow, the N1/EPR command and trend indications, and seat of the pants to tell you about engine thrust.

Also the FBW helps you fly by holding the last attitude you commanded (within certain limits) so there is less to do; leaving you with more capacity.

[Metro man]

On the A320 you need to remember to move the levers back so that commanded thrust is equal to current thrust before disconnecting A/T or power goes straight up to climb setting.

Being able to pull the levers back on a Boeing without looking at the instruments first, getting advanced warning of a commanded power increase and being able to prevent it simply by holding the T/Ls back would be something pilots transitioning onto Airbus would miss.

Experienced A320 pilots on approach can control thrust using the side stick, anticipating sink and applying back pressure will give a thrust increase, anticipating ballooning and applying forward pressure gives a decrease. Inexperienced pilots often have difficulty and get "out of synch" with the aircraft resulting in porpoising around the glide path with ever increasing thrust changes.

[vilas]

The technique is no different whether thrust levers move or not. With ATHR You don't need to get glued to EPR/N1. You have target speed and trend arrow which is enough. It is same with manual thrust but when you make changes to thrust either due to configuration change or to kill the trend you need to look at the thrust guage to get an idea of reference thrust.

[pineteam]

100% agree with Vilas. When flying with A/Thr off, you don't really have to look at the engine parameters. You set it around 50% n1 for the approach then just by looking at what the speed trend is doing you can adjust the power accordingly. Speed trend is so good you don't need to look at the n1 setting to fly accurately. I only have a quick look sometimes just to do fine tuning to match the N1 setting equally on both engines.