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Auto Throttles.

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Auto Throttles.

Old 27th Feb 2009, 16:18
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Auto Throttles.

Auto Throttles.

In the thread on the Turkish Airlines accident, there is a lot of discussion on auto throttles during the approach phase. I've never flown an aircraft with auto throttles, but have ridden in the back when they've been used. How do I know? The engines were forever 'hunting' to maintain speed. Most annoying. I could tell it made many passengers nervous.

When you guys/gals have the auto throttles engaged, what do you do with your right/left hand? Seems to me, without having your hand on the throttles, attention could be drawn away from your airspeed and just what the engines are doing. Seems like there's just too much reliance on auto throttles to perform the task that pilots have done themselves since the Wright Brothers.

But, I imagine all aircraft produced now-a-days come 'standard' with auto throttles. Is that right? I just think it's sad that more and more tasks are being taken away from the pilot leading to more and more problems. Next step is the drone for passenger carrying aircraft. Don't laugh.

OK.....let's hear how "ancient" my thoughts on this are.
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Old 27th Feb 2009, 16:23
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hold on to the auto throttle, while wondering what it's going to do next....

And no there's nothing subtle about it.

GC

edit: yes they move (luckily)
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Old 27th Feb 2009, 17:31
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On the last approach of a 4 sector day in gusty conditions, when you are told to "turn right heading 110degrees to establish on the localiser and intercept glideslope from above maintain 170kts to 5DME contact tower on 118.425 expect late landing clearence due to departing aircraft." You will be thankful for Auto Thrust, especially if you are a relatively inexperienced pilot like me.

On the note of system competence. I've only flown the A320 series, and unless its seriously gusty, it performs the job well. I don't think you can really judge how well the A/T is working by "sitting in the back". On approach, with A/T is engaged, it's SOP to keep your hand (left hand for me) on the Levers.

Unlike the Boeing, when the A320 is in A/T, the levers don't actually move, I found this quite strange at first, but quicky adapted. N1 is displayed on the upper ECAM, and airspeed on the PFD. The levers don't directly control the airpeed, so I'm not quite sure of the benifit of having your hands on moving levers and that being related to knowing your airspeed. You can "feel" and "hear" the aircraft engine power, which is an added bonus, but really, all of the information you need is provided to you in an efficient scan.

I don't think it's being "taken away", as on many days I enjoy a manual thrust approach, it's my choice. At the end of the day I must judge how much mental capacity I have, and if it is safe to take a particular course of action.

EpsilonVaz

Last edited by EpsilonVaz; 27th Feb 2009 at 18:10. Reason: typo
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Old 27th Feb 2009, 17:33
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When the A/T is engaged, never touch them! It is only when you fly with u/s A/T you realise what a boon it is. Always setting correct climb power for you, backing off power when you level, setting cruise power and maintaining it. When they are u/s, it actually becomes hazardous because you are varying between near clacker and near min buffet! You do lose continual situational awareness as you rely on it so much. Flying such a 747 back from BKK to LHR was very hard work! Are they worth it? Yes, a million times over! Takes away a very tedious task.

On approach, you can get hands on thrust levers, disconnect A/P and then do whatever your company does to the A/T. Safe, better monitoring and control of speed by the automatics, with warnings of speed discrepancy- what can be wrong with them? While they work!
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Old 27th Feb 2009, 19:02
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EpsilonVaz -
Unlike the Boeing, when the A320 is in A/T, the levers don't actually move, I found this quite strange at first, but quicky adapted.
I don't much like THAT idea at all; engines changing power and the throttles NOT moving. Guess I'm just too old fashined.
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Old 27th Feb 2009, 20:04
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On the airbus it's easiest to just think of the thrust levers as thrust limiters (with A/T engaged of course). Typically the thrust levers will be in the CLB detent from thrust reduction altitude until the flare. Obviously the thrust will vary throughout the flight but the levers will be stationary.
In manual thrust they work the same as any other aircraft.

I think some of the smaller Embraer aircraft do not have auto thrust installed but don't take that as gospel!
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Old 27th Feb 2009, 21:28
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I don't much like THAT idea at all; engines changing power and the throttles NOT moving.
Why, out of interest? The gauges tell you what the engines are doing... you don't need a great big lever constantly moving backwards and forwards to confirm that.

I personally find it to be a great system.
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Old 27th Feb 2009, 21:32
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Guess I'm just too old fashined.
Quite.

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Old 27th Feb 2009, 21:35
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I fly the B717, my first type with auto throttle.

For approach, say from 1500' AAL or thereabouts, when configuring for landing is usually complete, my hand is on the throttles moving with it, and if it wants to reduce power due to low level wind effects and I don't want it to, I resist the movement.

On take off, once the auto pilot is engaged my hand comes off the throttle, and sits on my knee, ready to intervene if necessary.

Originally Posted by DC-ATE
I've never flown an aircraft with auto throttles, but have ridden in the back when they've been used. How do I know? The engines were forever 'hunting' to maintain speed. Most annoying. I could tell it made many passengers nervous.
In my observation the hunting is caused more by technique than "it's got auto throttle".

I believe that if the pilot was not flying with auto throttle, they would manage the approach so that as constant a power as possible was held whilst progressively configuring for landing, to minimise power/pitch couple changes. However, with auto throttle and auto pilot engaged, Bloggs doesn't have to worry about it, and some let the automatics take care of it.

I find that on the 717, reducing from 250 kias (with some descent power on) to 210 kias (Co. min clean), and then configuring as the desired speed is progressively reduced, keeps the power at idle until configured, and then there is one increase to maintain Vapp, not an increase as the machine captures the 4 speed targets with configuring.
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Old 27th Feb 2009, 22:22
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Well at least on your 717, it sounds like the throttles MOVE with power changes. Apparently, on the Airbus they don't.

And, yes..."Quite"...I am old fashioned. Piston-powered aircraft, and 'steam-powered' jet aircraft served me well for thirty years. I only hope all this new stuff gives you all the same results.

Thanks for the input.
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Old 27th Feb 2009, 22:46
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Fair enough, DC-ATE...

...but you still haven't answered my question. What is it exactly about the non-moving thrust lever autothrust systems you don't like? Why is it? And what are these "more and more problems" to which you allude in your initial post? You haven't actually specified any, and there's no evidence yet that the 737 A/T system had anything to do with the Turkish crash.

I'm not having a go - just curious.
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Old 27th Feb 2009, 23:19
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DC-ATE,
As you can see, most of us like our auto throttles. I agree with what you say about more automation reducing handling skills but it also frees up a few neurons for other tasks. You were probably a better handling pilot than many of us these days but we probably have more traffic to dodge than you had so need to keep an eye on the TCAS. The A/T on th 733 is prety good and is said to be able to recognise wind shear earlier than a human but it doesn't always look that way. Getting back to the left/right hand, most pilots in my company guard the thrust levers at level off as sometimes one side can malfunction and cause a large split. The 73 will roll abruptly if this is not corrected as you will remember.
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Old 28th Feb 2009, 00:01
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bjkeates -
I just don't like the idea of engines changing settings without the throttles moving. Doesn't make sense...seems a little sppoky if you will. As someone has said the B-717 A/Ts move while engaged. I MIGHT be able to live with that.

And, I guess to say I don't like the idea isn't totally fair being as how I've never used them. All I can say is the idea does not appeal to me.

I guess I'm just one of those that wants to "be in control" all the time.

You're right, we don't know.....yet.....if auto throttles have played a part in recent accidents or not.
-------------------------
CHfour -
I can see by the replies that "most" of you like your auto throttles. But, I'm affraid that you could put any airplane equipped in any manner in front of many pilots and they'd fly it anyway. That's another reason why pay scales keep going down, but that's another topic!

As to your....."sometimes one side can malfunction and cause a large split."

Ah ha.....you admit something can and does go wrong with them. See, I told ya so!


OK.....again folks, thanks for the feed back. You all be careful out there.
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Old 28th Feb 2009, 00:37
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The moving throttles give you a sensory input through your hand on what is happening with the power setting and keeps you more in the loop.
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Old 28th Feb 2009, 01:09
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Let me add one more thing if I may.

The following link applies to automation in general (not just auto throttles) in today's cockpits.

While I realize automation is here to stay, it doesn't necessarily mean it is safer than what we had before.

Phase 1 Report - Flight Deck Automation Issues
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Old 28th Feb 2009, 01:42
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The moving throttles give you a sensory input through your hand on what is happening with the power setting and keeps you more in the loop.
Quite...and well worthwhile, IMO.
The autothrust on the 'ole L1011 is the same, and very accurate, without excessive throttle 'hunting'.
A superb arrangement...and oddly enough, I have never had it fail to function as advertised.
Combined with DLC, an unbeatable combination.
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Old 28th Feb 2009, 03:19
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DC-ATE,

If 411A is saying something "modern" in terms of an Autothrottle is good, it must be pretty damn good!

I find Airbus' decision to not have the thrust levers move an odd one, but plenty of people around the world fly them and have no issues.

The 767 has moving thrust levers and does a pretty good job, esp as a speed protection function. Its a little more agracultural than some would like, but when all said and done it does a pretty good job!
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Old 28th Feb 2009, 03:57
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DC-ATE

While I realize automation is here to stay, it doesn't necessarily mean it is safer than what we had before.
Well I beg to differ on that, if you compare the accident rate 20 to 30 years ago verse the last 10 years. Also remeber the number of jet transport aircraft has almost doubled since 1990 yet the accident rate has still dropped.

I cut my first 15 years flying out on very basic B732 (no auto thrust, no FMC, no Alt Cap on the A/P, no thrust computer) and F27 aircraft. The last 10 on a B733 with everything and I feel my management of flight is far superior than the good old days of "stick and rudder". I make better decisions and use less fuel with help from the automatics. Understanding what the aircraft is capable of and how to best manage the autoflight to achieve that is the key.
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Old 28th Feb 2009, 04:35
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Understanding what the aircraft is capable of and how to best manage the autoflight to achieve that is the key.
Yup, would agree.
When the FMS made its appearance on the TriStar, it was a huge improvement in flight management.
Full LNAV/VNAV and full time engine thrust management in a neat package.
Even today, it still works as advertised.
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Old 28th Feb 2009, 05:37
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"Without belaboring a point, which is probably obvious to the reader, there are two features of the B-757/767 aircraft (and shared, of course, the B-747 and the B-777) which enable these airplanes to achieve the greatest benefit from the fuel-efficient engines and aerodynamic efficiencies These are (1) a computer which is able to perform complex cruise calculations and (2) an autoflight system, including autothrottle, which is able to translate the cruise calculations precisely.
The first-generation of turbojet transports such as the DC-8 and B-707 did not have autothrottles. If a pilot attempted to operate at maximum range cruise, it would be counter-productive due to the inherent instability at these speeds and the constant attention demanded of the pilot to thrust manage- ment. As a result, the "practical" minimum speed for these airplanes was Long Range Cruise (defined as 99% best economy). The fact is that flight manuals didn't even publish data for speeds less than LRC.

Second generation airplanes, such as the B-747, while incorporating an autothrottle system, were still unable to operate at maximum range cruise due to inherent inefficiencies of the autothrottle system. The automatic system operated the fuel controller though the same linkage used by the throttle levers in the cockpit. The system was difficult to maintain and thrust overshoots and undershoots were common. Much of the time at cruise was spent manually aligning the throttles. The practical minimum speed remained LRC.
The767-200 and the RB211 version of the 757 permit the fuel controller to change engine thrust through a pre-determined range without back driving the throttles. Although the system is still hydro-mechanical, more precise control of cruise is possible. Finally, with the advent of the true fly-by-wire system found on the B-747-400, 777, 767-300 and the Pratt & Whitney version of the 757, almost flawless control of the engines is possible. Speeds from Max Lift/Drag to the Vmo are fully usable."
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