B777 logic - balked landing/GA after touch down
 

Hi,

There are a couple of threads running on the Emirates accident the other day so not looking to start a new debate.

As a B777 driver I have been looking in my manuals for information on what happens when you select TOGA after touchdown. My memory is failing me but it is along the lines of.......if you are less than 5' for less than 2seconds then you need to manually advance thrust levers. If you are less than 5' for more than 2 seconds you don't get FD guidance. In either case you are required to select TOGA again once airborne.

I appreciate that what I wrote above is most likely wrong, but you know where I am coming from. Not suggesting this is what happened, I am just trying to satisfy my own curiosity and find the reference which I cannot find in either FCOM or FCTM. Any help greatfully accepted.

Regards,

GBD

I have unofficial information(study guides, etc) for the 747 that say that it is inhibited once below 5' for 2 seconds until 3 seconds after climbing above 5 feet.

Then on the 777 I have similar but it says inhibited below 2 feet until 3 seconds after climbing through 5 feet.

But in both cases, none of this is in the official manuals. The FCOM in both just says "The TO/GA switches are inhibited when on the ground and enabled again when in the air for a go–around or touch and go"

Frustrating isn't it....perhaps a sign of the manuals being "dumbed down" or "why would you need to know that"...:hmm:

Like you gents a few years back I recall my previous type's FCOM (744) gave the numbers ( and yes, I recall it being something along the lines of below x feet for y seconds).

Not sure if I have ever seen the 777 FCOM with numbers quoted and as JS states now it just seems to be the narrative as described in our FCTM, FCOM, etc.

I guess all this means it's bound to be a question in this year's tech quiz.......:ooh:

I'm guessing a lot of it is hidden in the AMM these days, which they specifically don't want pilots reading in case it gives us any ideas.

Thanks for the replies so far.

I suddenly thought I might have written down the figures from the CBT in my notes, but no joy.

As you say wiggy, a possible dumbing down of the manuals! I guess Boeing don't want you trying to work it out just fly the aeroplane and once airborne hit TOGA.

Cheers,

GBD

On a similar type I believe it's 2 seconds after 5 feet radio. Seem to recall that's in the relevant FCTM and probably the FCOM too.

I'd have to check but I suspect you may not get FD bars until 400 feet either. That's just my guess from operating t'other large Boeing.

BBK

For a go-around, as long as the airspeed is above 80 knots and the flaps are not up pressing TOGA will give you TOGA flight director indications, even if the FD switch(es) are for some reason off(although the system has to be armed, which it always is). Except of course while inhibited on the ground after a landing.

Out of curiosity, as an Airbus driver, what happens if you firewall the thrust levers? Do you just get TOGA power but no flight director guidance, or does it merely guide you down the ILS with TOGA power set?

I believe that you would still be in Loc and GS with increasing airspeed. Air France tried it on a 777 and you can read about it here.
https://www.bea.aero/fileadmin/docum...p111116.en.pdf


As far as I know, the only way to get TOGA is to press either or both switches. Keep in mind that this is FD indications and a thrust setting but not necessarily full thrust. One push gives you enough thrust for a 2000 fpm climb as a nice way to keep you from rocketing up toward a potentially low level off altitude. The second push gives full thrust for situations where it is desired.

From the AMM
TMCS - A/T OPERATION - GO-AROUND
The go-around (GA) mode engages when all these
conditions are true:
- Autothrottle arm switches on
- Airplane in the air
- Glideslope active (engaged) or flaps not zero - Thrust limit mode not takeoff (TO)
- Push either TO/GA lever.

Being an old fart I ask forgiveness: I flew B767/757/738. Lots of automatics, but still quite basic if you wanted them to be. When you press TOGA the FD might, or not, give you guidance, but there is always a target attitude. The auto throttle might, or not, give you an increase in thrust, but does everyone not 'follow through' on the thrust levers? My thought is that if you want to GA you increase thrust & increase attitude. If you are in the mode for an automatic CMD GA then you'd expect it to comply, but you'd still follow though to ensure George fulfils its contract. If you are in split mode of autopilot and/or auto throttle surely you would ensure that the auto-part did its bit and you did your bit. Sitting back and watching after pushing a button does not sound the best technique.
I'm not relating to the Emirates particular accident; I haven't read all the threads, just a discussion on GA's after touchdown.

As a newcomer to the 777 from the 738, go arounds require a slight mental reprogramming as in manual flight, there is no pitch/thrust couple to ease the rotation to the go around attitude. Instead of a slight aft movement then a check forward to counteract the thrust coming on, a firm positive rotation is required to the new attitude.

Automatic go around is available on the 777 whenever the AP is engaged. With the AT armed (which it should be at all times even if disconnected using the push buttons) pushing TOGA will get you autothrottle and FD activation. If the FDs are off, the bars will disappear at ALT capture.

Sleeve of wizard - does the AMM tell you at exactly what point the TOGA switches are disarmed? Or does anyone have any earlier FCOMs/FCTMs which might contain more technical info than the current bunch?

Unfortunately RAT 5, the days of knowing pitch and power are going, more and more of us are working for airlines where manual flight is not encouraged and taking out the autothrust is not allowed with the result that our flying skills are diminishing. Those that work for more enlightened companies or fly older varients like the 757, I am envious.

I digress.

Whether or not the recent accident was a result of hitting TOGA but not getting the thrust, or not, we will find out in due course. Either way it is something I will be more aware of now.

Regards,

GBD

JWscud,

Just seen your post.

I believe it is less than 5' but no one can find a definitive answer. It used to be in my FCOM, but now can't find the info anywhere.

GBD

The 744 used to have the height/time restriction.

The 777 is easier to get your head around.... You can Go-Around right up to the point thrust reversers are deployed, beyond that you're landing.

We did a SIM training exercise recently which was all about baulked landings, its fair to say that 99% of are in a much more landing mentality than a go-around one.

The thread starts an interesting tech question, which might be better considered by asking why a pilot would need to know, and if so is this an essential function, i.e. should know / must know.
All of this suggests 'clumsy use of automation'. If the logic is essential, then explain why, but don't expect pilots to remember or recall obscure facts in remote corners of operations, particularly in time critical, high workload, or rarely flown manoeuvres.
With this view the function is a classic latent 'factor', waiting to catch the unwary and under resourced pilot in a rare situation; yet it is something which apparently meets the certification requirement.
If the function is an essential requirement, then describe it, add cautions about use in unusual circumstances. If not, then reconsider the design and certification, ... but then there is cost, risk, etc all driven from the manufacturers position; it easier to recommend more training, monitoring, etc; but do these actually work, would they work in this situation.
What we must learn from the question is to challenge the design and certification assumptions in increasingly complex (but rare) operational scenarios; not a safety report as why the human forgot, a report of the poor implementation of technology and documentation.

"The Clumsy Use of Computer Technology page 113 onwards

• ... the supervisor of automated resources must not only know something about how the system works but also know how to work the system.
• ... relatively easy for pilots to lose track of the automated systems' behavior during high-tempo and highly dynamic situations ...
  
  And page 122 onwards
  
  
• computer-based devices that influence cognition and behavior in ways that increase the potential for erroneous actions and assessments can be considered flaws in the human-computer cognitive system.
• One factor that contributes to clumsy use of technological possibilities is that new technology is often designed around "textbook " or routine scenarios."

Quotes from 'Behind Human Error: Cognitive Systems, Computers, and Hindsight'.

This is part of why I prefer to at least start my GAs fully manually. No need to wonder what the automation might do, if you're not using it.

This will always be the best practice. In my mind, pushing a TOGA button and confirming the automatics are with you works out to the same time and energy as doing it for yourself. One can then continue on flying the airplane whilst the PM takes care of clean up/COMMS duty per the procedure.

Agree - there is no greater guarantee for TOGA thrust than by manually pushing them fully forward to the stops.:ok:


Then come back to the automatics as required.

Go Around pitch xx, flaps yy, TOGA thrust!
This call out should be part of the approach brief and actually done at the initiation of a go around.
Traning and SOPs shound be updated before next crash.