View Full Version : A/t In Speed Mode For Landing (737)

11th Jun 2007, 06:17
any 737 drivers have any views on landing with the a/t in speed mode or deselecting the speed mode (ARM) during cat 1 conditions . which is better during bad wx conditions rain/ low vis .

11th Jun 2007, 06:48
Either you put everything on or you put everything off in my opinion.
I know that my UK collegues disagree.

11th Jun 2007, 07:28
That's quite right. Either all on or all off. If wx is CAT 1. Minima, you can still fly a manual approach. According to Boeing if you fly manually you need to disconnect the A/T as soon as the A/T is off. (either by swtching off the hard switch or by depressing the speed mode, both is acceptable, but be very careful of the later, because in the ARM mode you still have low speed reversion (protection) from the A/T! If you do an extended flare the throttles MIGHT come up very slowly during the last 5-10 feet (if the flare and the speed reduction is very smooth) and if you don't notice it you are floating along wasting valuable rwy distance...) If it's below CAT 1. you're doing an autoland anyway so might as well have the A/T on for the landing. And finally if manual landing in the MCP SPD mode: again be carefull, the A/T will announce RETARD and it will close the thrust levers at 27 feet regardless if it is coupled to an A/P approach or not... And that might end up in a less than desirable landing in a heavy -900 in 35 degrees centigrade...

11th Jun 2007, 08:01
spd deselect is better, you have GA power with 1 push of the togas, you wont overboost the engines and you dont have to look on the power while doing the ga.also the min speed rev is fine, protects you

11th Jun 2007, 13:17
Boeing says that ARM mode is normally not recommended because its functions can be confusing. As many of us here I think that after a "few" hours on type these functions are not so confusing after all, but that is what the manufacturer states indeed. If you get into troubles during an approach with A/T ARM and speed off it will be difficult to prove that this was the best solution at that time. In CAT I for me it is A/P off, A/T off. In case of G/A the PM will adjust the N1 value, exactly as it happens in the SIM (or should happen:p).
Bye !

11th Jun 2007, 14:08
All on or all off. I say. What's the problem with setting G/A thrust yourself? Just push the levers fwd.

Tee Emm
11th Jun 2007, 14:40
or by depressing the speed mode, both is acceptable, but be very careful of the later, because in the ARM mode you still have low speed

Speed mode is not correct according to the 737 FCTM. Boeing recommend the autothrottle system be switched off completely when hand flying except in take off and climb. They have done the research and development on the autothrottle operation and their advice is good enough for me.

11th Jun 2007, 16:11
Boeing recommends many things. However I personally disagree with the all on or all off philosophy.

whats the problem with deselecting spd mode with A/T armed?

why would leaving it armed cause confusion. if it confuses you then you shouldn't be flying it.

I can see only good points about it.. underspeed protection, automatic goaround thrust selection when toga is pressed.

11th Jun 2007, 19:45
During linetraining I had cpts saying both versions so it was just to fly the way the specific cpt wanted you to fly with the modes.
Now afterwards I personally like to fly it with the A/T armed and speed deselected as others described the valuable functions still available for you.

Tee Emm
12th Jun 2007, 14:23
whats the problem with deselecting spd mode with A/T armed?

why would leaving it armed cause confusion. if it confuses you then you shouldn't be flying it

Perhaps you should contact the manufacturer and suggest that the FCTM be revised as your experience reveals the Boeing auto-throttle recommendations are flawed. Don't forget to quote the results of your measured flight tests to back your argument.

12th Jun 2007, 16:44
In my company it is SOP to just deselect speed during manual flight. That is to assure low speed protection and automatic G/A thrust. But then, we don't use Boeing procedures but rather our own which are developed in-house.

13th Jun 2007, 20:00
I wonder if on-house procedures are approved by boeing? If not, what will you do in case of an accident? The manufacturer can not be held accountant for something if you don't follow it's procedures.
Regarding ARM use for the a/t , you'll have a "nice" surprise if landing low weight,on a gusty wind...high thrust set by the a/t just during flare,as it senses the approach to stall (low speed,momentary high AOA) . It has happened before ,it will happen again, and we'll talk then about your view of using the a/t in ARM.
The Bus is different in design of the autothrust, so don't try to duplicate it.
Also, on the Ng there is nothing to worry,you may firewall the throttles ,no problem..
My 2p,do as the manufacturer says..it has test pilots and engineers to create its procedures.

15th Jun 2007, 09:27

If you fly by chance for [Airline X], let me warn you that their "in-house" SOP's are sometimes verging on the ridiculous and more seriously, dangerous.

I know of FO's who were not allowed to have their approach plates on the joke due to [Airline X's] SOP's...:=

"deselect Speed mode" is another ridiculous practice that can potentially cause a highly dangerous situation (see some former posts).

Is the SOP still to ask for Altitude Hold after an Engine failure at EFFRA? If so, did your trainers EVER try this with max. weight on a restricted field in the sim?

Is your callout on a G/A still: "Go around set GO around thrust, flaps 15"?:ugh:

16th Jun 2007, 17:37
Lou,so you've really signed off people?...wow
I've met guys like you , saying that following manuals means we're monkeys,not pilots...One of those 'experienced' guys tought me to use HDG SEL and the EGPWS in case of terrain avoidance , no matter the wing level procedure Boeing instructs,or the fact that the EGPWS is not allowed to be used for navigation..
One other guy had a habit of doing smooth landings by selecting flap 40 at 5' :sad: , reason beeing smooth landing and saving the brakes :ugh:
I can give you some other examples like that,all experienced pilots, who tend to think they know the plane better than the ones that build it.
One word I've learned long ago is that in our business the ones that die are the stupid ones and the better ones .The first are obvious but the last ones do it from the reason you say,they are damn good pilots,know all,had done all, they are not monkeys, so ignore the SOP,books,etc..those are for rookies.
I'm happy to fly with any pilot, rookie or top gun,but if he won't follow the SOP we'll have a problem..
If the on-house SOP it's bad ,then you may try to improve it,using the right channels.We are using the Standard Boeing SOP,and it's ok.
You are talking about teaching the low-experienced pilots to stop the a/t from retarding thrust during flare?...what next?..land on the left wheel,for a smooth landing? they are low-experienced pilots,how many instruments do you think they are able to include in a landing scan...too long to remember,maybe
Teach them to follow the SOP and they'll have a long and safe life...as one said those books are written in blood.

28th Jun 2007, 20:53
I asked the Boeing 737 Chief Tech Pilot this question today. He said he is asked this a lot.

The Boeing recomendation is to have the A/T switched off (don't leave armed) for the reason that it may under certain conditions (flaring too high, float or gust of tailwind) command an increase in thrust during the flare as a reaction to the loss of speed, which will destabilise the landing. This has lead to tailstrikes and could lead to an overrun.

Ignore this advice at your peril. If you have an accident due to this config, you will be asked why.

Surely now, debate over.

28th Jun 2007, 23:37
Woa there! Before you call for discussion over and done with.......who are we talking about ('Boeing 737 Chief Tech Pilot')- the Boeing man or your airline B737 Chief Pilot? I note use of the word 'recommendation' as opposed to 'instruction'. How are we to handle the many airlines and simulator trainers who recommend leaving it in? It is not so cut and dried. I have noticed occasionally the thrust levers come alive in the flare as the A/T re-engages itself. It should not be a problem- a large meaty fist should be covering both and selecting idle reverse. In fact no problem at all. And, should you suddenly have to do a go-around- one simple press of the TOGA switches and you're away, with automatic thrust selection and FD instruction. On manual A/T approaches, I've found one person is poncing around trying to select thrust instead of monitoring and selecting flap and gear close to the ground.

29th Jun 2007, 04:39
Dunno whether its different on the NG, but I have been doing the de-select thing on the 737 Classic for the last 10 years.

Its only drawback is when it enters low speed protection mode in the last 200 ft. My experience is that it goes low speed prot mode, plays with the thrust levers. At 27' RA it then goes into retard mode (aka an autoland). Left alone it can lead to the odd firm arrival (understatement). Solution, when ever it goes into low speed prot mode below 200' I click the A/T out...

..Having it there for the G/A is invaluble.

29th Jun 2007, 08:38
Isn't it iniquitous that Boeing apparently recommends not using A/T is Spd mode on final approach because you may have A/T engaging, yet after commencement of taxi, Boeing procedures are to turn A/T on? Just takes a flick to the TOGA switch and you find power going up on taxi. Seen it done (and done it myself). But it's not a problem if you have any sense

29th Jun 2007, 08:45
Hi Rainboe

I thought my post would wake you up !

It was indeed the man from Seattle. Full title “Chief Technical Pilot 737 Training, Technical and Standards Flight Crew Operations”. A Boeing TP and a man with 26 years on type. I for one defer to his knowledge & experience.

He is fully aware of the argument of having TOGA thrust available and has operated both ways, but his position was that on balance it is safer not to have the A/T armed. In fact he raised the subject first, just to check that we were not doing this.

The counter argument to not having TOGA available at the push of a button is that it is still available at the extension of your arm. It can take up to 8 secs to get TOGA thrust from idle, so just putting the thrust levers somewhere in the ball park while you hand fly the manoeuvre and then ask the F/O to set TOGA thrust (if necessary) is not a problem. With the minimum A/P engage height now being so low (400ft agl) the chances are that you will be able to engage the A/P & A/T very soon after the G/A anyway.

BTW I share your concerns about arming the A/T in the before start procedure and I am kicking myself for not asking him about this.


29th Jun 2007, 14:04
Lou Stulewater: Your hand should be on the thust levers therefore you can easily override any spurious commands by the a/t.up or down Are you pilots or not..Stop theorising so much and fly the plane. Re the fctm see the last sentence.

HAHAHA this is very funny.:D

You actually accuse us who take all automatics out of not being good pilots.

Now really............ "fly the plane" does that mean the samething as "use all automatics"??????:8

29th Jun 2007, 14:30
As an aside It can also help having the a/t in during early line trg sectors. Aids the candidate to concentrate on attitude during early stages of trg. Especially with so many coming with no attitude flying experience

Have to disagree on that point. They should have completed a full type rating course in the simulator by which time they should be competent at attitude flying. Secondly with autothrottle engaged during manual flight (apart from climb at max climb thrust), speed and height excursions are exacerbated by the AT moving forward and back trying to maintain MCP speed. The trim changes become difficult to anticipate. Much easier for the pilot to fly with AT disengaged as per Boeing FCTM recommendation.:ok:

1st Jul 2007, 15:32

Again, A/T is something very usefull for the pilot if that is used according to the manufacturer's guidelines. If you need to go around you stretch your arm and after that a good PM will set GA thrust as desired. Pilots who flew the -200 series or other airplanes without A/T are not so concerned about that :ok: