737 Go around? [Archive]

RAT 5

26th Oct 2015, 19:25

Well, there is always the different double click: click once to go into go around mode, then click to disconnect the autothrottle and do a slow manual thrust increase.

Careful!! These are 2 very different clicks.

Then again; before you reply "that I know that," the original questioner might not understand your experienced comment. But then again, one click of TOGA gives you a very gentle manageable ROC, so why would you want to disconnect. This could bring about speed control at level off as your scan is diverted from the essentials. That is but one reason why, often, the normal all engine GA is messed up.

FlyingStone

26th Oct 2015, 19:57

...but if you float on landing, doesn't the AT come in and help you fly down the runway at 10ft???

It shouldn't, if you use your hand as you should - holding the thrust levers at idle. Never understood why one would use ARM mode during approach on 737 anyway.

framer

26th Oct 2015, 20:53

If I have the automatics in and a go around is needed with a level off less than 2000ft away, I disconnect the A/P and the A/T , then press toga and use the thrust I want. Works for me a bit nicer than leaving the A/T in.

galdian

26th Oct 2015, 22:12

Couple of years ago a new/old "esteemed" Captain almost created a smoking hole doing a do-around after having disconnected the A/T (hello 1960's!) and not applying sufficient thrust, company "policy" to that point was ARM mode the 737 operation having been set up by those with substantial 737 experience.

Fortunately for the company the F/O was able to talk the Captain through the stuff up without the Captain losing "face"; just dumb luck, the right F/O in the right place at the right time, some would have been too conflicted by culture to have saved the day,

There are times when the ARM mode does NOT work (primarily gusty unstable winds) and is best disconnected, the question is not "when do you use ARM mode", the question should be "when would you NOT use ARM mode?"
Bit of groundschool, 10 minutes in the SIM and - as if by magic! - seeing is believing, all understood and everyone happy!

ARM mode is both an operational mode and a safety mode - why would you disconnect a safety mode if you don't have to?
And call me crazy but I don't believe "too lazy or too stupid" is a valid reason in 2015 - you'll have to do better than that please! :ok:

Finally for the "flat earthers" out there who reckon ARM is white man magic and should never, ever be used: why would Boeing waste time and money on a feature (yes again a SAFETY feature) if it's never, ever to be used??

I thought it was only Airbus who were that way inclined at times! :E

Pin Head

27th Oct 2015, 00:59

All good stuff guys, keep the debate going.

As per the manual, Boeing recommends a/t out as well as A/p. I have always done that and call go around flaps 15 check thrust. The last two words always cover me.

It was only flying with some Americans that I saw this arm thing. As its not in the manual I questioned the rationale for doing it.

Denti be careful with these double clicks. If you have left the auto throttle in for Ga and then take out the a/t once the go around has been established sounds like a recipe for disaster. Completely non Boeing and truthfully would create organised confusion to the other guy!

Derfred

27th Oct 2015, 02:05

why would Boeing waste time and money on a feature (yes again a SAFETY feature) if it's never, ever to be used??

Boeing did not design A/T ARM mode to be used during manual approach and landing. If they did, they would recommend to use it. So your argument just kind of backfired didn't it?

galdian

27th Oct 2015, 02:44

So when exactly does Boeing say the ARM mode SHOULD be part of ANY SOP??
Not sure it's stated anywhere - but happy to be corrected.

If correct then the use of ARM is only restricted by your imagination - or lateral thought, a thing too often lacking in todays society IMHO:

- Push TOGA in a go-around and (if in ARM) 1st stage power is applied - therefore avoiding the very incident I mentioned of applying insufficient thrust at a time of high workload;
- leave in ARM on a dark and stormy 600' low vis circling approach and (after politely pointing out to the individual they are getting too slow) if uncorrected will apply power to avoid stickshaker and/or stall.

Using features that increase safety to....increase safety, interesting concept. When will such lunacy end?? ;)

And please - anyone - do not try and misquote Mr Boeings words against him - use of ARM not NORMALLY recommended as KISS principle for new jet operators; everything manual or everything auto.
With proper training and understanding - fill your boots (as I've done for over 26 years.) :ok:

Finally same question applies - why would Boeing bother with a function that is never, ever to be used??

Pin Head

27th Oct 2015, 03:41

Go around flaps 15 Check thrust

Those last two words cover the need not to use Arm in my view.

If he or she can't manually set an N1 target of day 88% ( two fat ducks, bingo speak) then I would scratch my head

Denti

27th Oct 2015, 03:44

...but if you float on landing, doesn't the AT come in and help you fly down the runway at 10ft???

Actually, if it comes on it will directly enter into flare logic aka RETARD mode if below 27ft RA, see the turkish airlines accident.

Denti be careful with these double clicks. If you have left the auto throttle in for Ga and then take out the a/t once the go around has been established sounds like a recipe for disaster Well, i didn't say until the go around is established, and even if you wait for that, where is the disaster? Thrust is established, attitude is established and one knows with the second click that it is now solely the pilots responsibility to regulate thrust.

The discussion about the use of the ARM mode is very old, but apparently some airlines use it and it doesn't cause smoking holes. Personally i used it during my stay on the 737 for about 15 years in several carriers that had it as their SOP and it has some advantages and some disadvantages, but nothing that cannot be trained for.

Wizofoz

27th Oct 2015, 03:48

A while since I flew the 73, but when I did, Boeing recommended against doing approaches in ARM because of the possibility of uncommanded thrust movement during flare and landing.

Gypsy

27th Oct 2015, 04:25

Boeing don't recommend it for a reason. Wise airlines (and pilots) just follow the manufacturers policies otherwise you could end up in an awful lot of legal quagmire

Derfred

27th Oct 2015, 04:38

Galdian, Boeing specifically recommends against using A/T ARM during manual approach and landing. Other phases of flight according to normal automation SOPs. Therefore, A/T ARM mode is SOP for takeoff (prior to TOGA and after THR HOLD), and idle thrust descent with A/P engaged.

Yes, some airlines include it in their SOP's, in specific defiance of Boeing's recommendations, because they think they know better. That's up to them. Other airlines fly in accordance with the manufacturer's recommendations, including mine which is one of the oldest airlines in the world.

The only near-smoking hole involving a normal go-around I've read about in recent times was in your (and my) country and it was caused by an operator varying it's SOP's in specific defiance of Airbus's recommendations, because they thought they knew better.

galdian

27th Oct 2015, 05:22

Gypsy
Please quote Boeing FCTM correctly:
"...do not NORMALLY recommend...."

Derfred
the almost "smoking hole" was in a smaller company in Asia in January almost 3 years ago, didn't make global news as the smoking hole was (only just) avoided so merely an incident for local and company information.

Regards your points ref use of A/T in ARM mode could I ask the question another way:
- why have Boeing included the ability for the PF to de-select the Autothrottle into ARM mode if this function is (apparently) never to be used?
Surely the A/T automatically going into ARM mode as you describe could be wired as a function of the on/off switch and A/T computer and other associated system computer logics etc?

Why is the tempting (well for me at least) button there on the MCP acting like an aviation siren and whispering "deselect, deselect" so seductively??

Cheers:ok:

galdian

27th Oct 2015, 05:50

To all:

I'm presently on hols and away from my FCTM, my understanding has always been per Mr Boeing:

- as the 737 is often the first jet upgrade for a turboprop operator use the KISS principle, everything auto or everything manual as the ARM feature CAN be confusing;
- if you have had proper training and have proper understanding then use ARM as desired and if for some reason (winds, other factors) the ARM mode is not acting correctly then disconnect the A/T...as you would any other system that is not performing correctly.

I am not aware of anything in the FCTM that is more specific to different phases of flight, if I have overlooked or misunderstood something then my bad.

Cheers
Galdian.

Gypsy

27th Oct 2015, 05:50

The large Company I used to fly the 737 for, had so many people asking about this that they wrote to Boeing to ask. The answer was clear. Boeing would not recommend it.

FlyingStone

27th Oct 2015, 05:50

Since Boeing recommends and large majority of airlines are not deselecting SPD on approach, I guess there must be something to it...

Regards your points ref use of A/T in ARM mode could I ask the question another way:
- why have Boeing included the ability for the PF to de-select the Autothrottle into ARM mode if this function is (apparently) never to be used?
Surely the A/T automatically going into ARM mode as you describe could be wired as a function of the on/off switch and A/T computer and other associated system computer logics etc?

Boeing has included a lot of features on the 737 that you shouldn't use as per their recommendation: A/T with manual flight (except during takeoff, climb or go-around), G/S capture before VOR/LOC (before respective SB), etc.

Aviation as all other industries learns its mistakes as times goes by and sometimes manufacturer's brilliant ideas during aicraft design turn out not to be so brilliant, so some capabilities of the aircraft are not recommended to be utilised in order to prevent some nasty situation to develop.

RAT 5

27th Oct 2015, 08:59

The ARM mode is a carry over from B757/767 where it is a design feature, I think, unless dementia has crept up on me unannounced. It's been a few years since....
People then went to the B737 MCP and played with the buttons and found that an 'ARM type mode' could be created and it seemed to be providing the same function as on B757/767. So guys started doing it and some CP's found out about that. As they didn't fly too much, and had never flown B757/767 they did not understand it. The normal human reaction of a manager who does not understand something is to ban it, so they did.
They also went to Boeing and asked the question; to back up their banning, and came back with the 'does not recommend' answer. So the ban stayed.
Now that begs the question how it can become an SOP? The manufacturer AND their XAA have to approve a 'non-normal'.

Regarding some comments about safety features and why Boeing would not recommend them: Boeing has this fixed philosophy that manual flight = manual controls + manual thrust. "period." So they changed TCAS RA to disconnect the lot. Previously it was AP only and leave AT in. Good idea. Then the philosophy gurus reviewed this, noticed the discrepancy and instructed AT disconnect. Bad idea. Why disconnect a safety feature? What problem had ever been created during a TCAS RA using AT? If it ain't broke don't fix it. Even if you apply the "what if' risk assessment I can not think of an answer that would cause the AT to be thrown out. When I asked a Boeing TC the reply was the philosophical one. No other reason.
However, they also had no idea about selecting 'TA Only' during an Emergency Descent or any other performance related non-normal incident; only the engine out case. Perhaps their philosophy nerds need some rebooting.

galdian

27th Oct 2015, 09:13

Thanks all for your input - and patience, maybe time for this dinosaur to pull the pin.

You have a function that affords safety (alpha floor protection and G/A thrust).

You can train a pilot to cope with many potential problems through ground school/sim training however understanding the use of ARM mode is beyond the capabilities of current airline training systems and/or (so it seems) pilots.

The answer: ignore the ARM function, turn it off 100% of the time and lose the safety potential 100% of the time.

The amusing thing: what is the No 1. stated concern for ALL and EVERY airline...safety!
And turning off a feature such as ARM that affords safety?? :ugh:

Anyone get the contradiction?

I realise conformity (with understanding) to company SOP's is an important part of operations, don't understand why not asking "why" is such a feared thing.

Maybe people have to die (like Airbus A330, finally "maybe basic flying skills and commonsense have been eroded too far..." before Boeing realise they have safety features in the ARM mode - so why not train to use them?

Cheers all
Galdian

galdian

27th Oct 2015, 09:24

RAT 5
Missed your response before I posted, thanks for your history/background.

Will only take issue with one point (and this may well simply be the difference between "official Boeing" Vs "talking to the Boeing delivery pilot over a few beers...."type stuff:

- all auto or all manual, KISS for new operators/turboprop upgrades;
- understand the ARM function then use it, fill your boots.

Now what was that thing about - safety...:ugh:

Cheers all
Galdian

ManaAdaSystem

27th Oct 2015, 10:29

Regarding some comments about safety features and why Boeing would not recommend them: Boeing has this fixed philosophy that manual flight = manual controls + manual thrust. "period." So they changed TCAS RA to disconnect the lot. Previously it was AP only and leave AT in. Good idea. Then the philosophy gurus reviewed this, noticed the discrepancy and instructed AT disconnect. Bad idea. Why disconnect a safety feature? What problem had ever been created during a TCAS RA using AT? If it ain't broke don't fix it. Even if you apply the "what if' risk assessment I can not think of an answer that would cause the AT to be thrown out

No, it's not a bad idea to take out the AT with a TCAS RA. If you get a descend RA with the AT in N1, you will very fast go into an overspeed situation. The AT will remain at N1 in this situation with no speed control.

cosmo kramer

27th Oct 2015, 11:00

Almost all of our aircrafts doesn't provide "minimum speed reversion" after G/S capture. Only some of the oldest ones provide that feature. So it seems Boing indeed removed "the feature" (or customer option). And worse you can't see it, as the A/T can still be deselected into ARM, so if you don't look in the manual, you won't know if your aircraft for the day has it or not.

Besides from that, the reason it's not recommended is most likely because it can be confusing when the throttle is armed and when not. If you do a VNAV approach, you HAVE to disengage the auto throttle completely.

So in a stressed situation, when flying a VNAV approach, a confused pilot might press TOGA without manually advancing thrust, and nothing happens!!

Better to keep uniform SOPs, so the pilot will always react the same, regardless of which type of approach is being flow. If you can't do a go-around with manual thrust, retraining is needed (badly)!

For the low speed scenario, Boeing invented the "airspeed low" GPWS call out. If that doesn't wake you up and cause you to advance thrust, you shouldn't be sitting in that seat either.

(...and I DO fly with ARM mode as it's SOP in my company).

RAT 5

27th Oct 2015, 18:43

For the low speed scenario, Boeing invented the "airspeed low" GPWS call out. If that doesn't wake you up and cause you to advance thrust, you shouldn't be sitting in that seat either.

Introduced after THY stall at AMS. So once again the solution/back-up is to insert another auto-function between pilot & a/c. As we seen over the years this only encourages, subtly, the pilot to reduce scan and rely on automatic warnings. Shades of SFX B777 and others. I suggest, strongly, that if THY had been a manual approach with manual thrust, and followed the exact same manoeuvre, they would not have stalled. Add to that the use of ARM, perhaps better. I've never been allowed to use it on B737 so can not comment on its function in reality. (Indeed, has anyone had it kick in the save their backside? or is it just a theory?)

No, it's not a bad idea to take out the AT with a TCAS RA. If you get a descend RA with the AT in N1, you will very fast go into an overspeed situation. The AT will remain at N1 in this situation with no speed control.

OK, true, if you are in a climb; but is it that critical? However, and I've seen it in the sim many times, they get a 'CLB CLB RA"; disconnect everything, apply 3g pull and forget to add power. Now do that at FL350 and see what the speed does. Is a low speed more/less critical than overspeed? One has a clacker the other a shaker & clacker. I've also seen the "DESC NOW RA + Increase ROD". Then "Clear of Conflict" = climb back to last cleared FL and forget to add thrust. Consequence? see above. IMHO on there balance of risks I'd rather keep AT engaged. Dogmatic philosophy has its weaknesses.

Regarding SAFETY and commonality of actions: agree. I know of some airlines that encourage maximum use of Automatics, at all times: yet they perform a single channel ILS or NPA with full automatics; make a G/A = AP disconnects, but AT remains engaged, but they fly the whole GA and flap retraction in manual with AT in engaged?????

ManaAdaSystem

27th Oct 2015, 22:16

Seriously?

OK, true, if you are in a climb; but is it that critical? However, and I've seen it in the sim many times, they get a 'CLB CLB RA"; disconnect everything, apply 3g pull and forget to add power. Now do that at FL350 and see what the speed does. Is a low speed more/less critical than overspeed? One has a clacker the other a shaker & clacker. I've also seen the "DESC NOW RA + Increase ROD". Then "Clear of Conflict" = climb back to last cleared FL and forget to add thrust. Consequence? see above. IMHO on there balance of risks I'd rather keep AT engaged. Dogmatic philosophy has its weaknesses.

There are no TCAS manouvers that require a 3 G pull. A manouve like that at FL 330 will be interesting, with or without thrust. It would be a FAIL and retake in my airline.
ANU = more thrust. Pretty basic, so if you many times have seen pilots who fail to understand this, then I suggest you may have a problem on your hands.
Maybe you should transfer them to Airbus?

TheiC

28th Oct 2015, 03:39

For the low speed scenario, Boeing invented the "airspeed low" GPWS call out. If that doesn't wake you up and cause you to advance thrust, you shouldn't be sitting in that seat either.

No, they didn't invent it. It was recommended by the Dutch Safety Board report. If I ever write a book on these topics you'll read its full story there.

Oh, and if it doesn't 'wake you up', you may be suffering inattentional deafness, which may affect anyone, so you seem to be saying that human pilots shouldn't fly the 737. Be careful what you wish for!

You have a function that affords safety (alpha floor protection and G/A thrust).

Leaving aside the philosophical challenge posed by 'affords safety', the feature has nothing to do with alpha floor, and the device which I prefer to use to apply go-around thrust, in the appropriate amount, at the right rate, is my right arm.

galdian

28th Oct 2015, 05:43

TheiC

Apologies if any confusion regards afford, certainly not meant in context of "affordable safety", perhaps "allow" would have been clearer.

In the go-around incident I mentioned it is indeed unfortunate your right arm was not there or quite clearly there would have been no incident.
Sadly your right arm was NOT there, the Captain applied insufficient power and an incident (almost accident) occurred which would NOT have happened had the A/T been in ARM mode. Fact!

Alpha floor - well if the A/T is disconnected and insufficient power set the aircraft will eventually stick shaker then stall if not corrected, if in ARM the power will come up BEFORE the stick shaker would activate thereby avoiding stick shaker and stall because the insufficient power setting has already been corrected.

Call me crazy but I'd call that Alpha Floor protection - possibly Boeing 737 style - but still protection which can improve (wait for it)...SAFETY!

Just a shame this system that allows SAFETY is too darned complex for the average knuckle-dragging pilot to understand! :p

Cheers all. :ok:

framer

28th Oct 2015, 06:40

and the device which I prefer to use to apply go-around thrust, in the appropriate amount, at the right rate, is my right arm.
Me too. That's why if I have a low level off from the miss I disconnect all automatics then carry out a manual go around.
This argument is really about pilots losing the ability to fly ( automation dependency ). If I was so overloaded that I I was at risk of not using thrust to fly my chosen airspeed to the level off then I certainly would not have the awareness to recognise that the level off is fairly low and make a conscious decision to fly it with the automatics out.
I agree with Theic about a pilot pulling 3G in a Tcas RA. I doubt any pilot in my airline has ever done that, even the ones known to struggle.
So if my assertion that at it's heart, this is a problem about automation dependency, is the answer rally to rely on automation more heavily? Or is it to provide an appropriate amount of manual flying training ?

galdian

28th Oct 2015, 07:03

framer
Don't quite see this is related to auto dependency, more about using a system in the standby mode that backs up the action of the PF to enhance safety.

That's certainly the case regards the alpha floor protection - it won't operate unless the PF has f**ked it up by not setting sufficient thrust - so it's about redundancy and safety.

We all have airports where different actions/procedures may be more appropriate - then you explain why, brief what functions you will/will not use, that's fine and all part of normal operations.
The question revolves around the 90-95% of flights where there are NO such consideration,

Disconnect a system that enhances safety. :ugh:

Yeah - that really makes sense in this day and age, love to see THAT logic explained in a court of law after an incident/accident. :E

Cheers.

TheiC

28th Oct 2015, 07:37

Adding go-around thrust without pilot intervention in an aircraft with under-slung engines such as the B737 has terrible potential to take the pilot out of the loop, and the aircraft outside the envelope, in tens of seconds. Alpha floor, in an envelope-protected FBW aircraft, is completely different to that.

As to 'more manual flying training', I'm more concerned that, one assumes, we and our colleagues could all fly a go-around in our PA28s, C152s, etc. But at what point, and why, do some of us cease to be able to carry our that simple manoeuvre in larger aircraft? Is it because the aircraft is too complicated for human pilots below a certain calibre? Is it lack of practice? Is it too much training in OEI operations (far less likely and yet the regulatory requirement for years) and the significant difference in that procedure?

Finally, the common errors in AEO go-arounds are speed exceedences and level busts, both of which are good reasons not to use all the installed thrust for this exercise, most of the time, and metering the right amount is again easiest achieved without automatic assistance, in my experience.

Boeing did not intend the A/T to be used in the way some here are describing, and they've said so. The 737's flight deck is elegantly simple, in functional terms, and there are few things which can be misused. But misusing those few has consequences: I don't believe the guys who designed the CDU meant the scratchpad to be used for noting radio frequencies. So perhaps they didn't foresee the brief disappointment we feel when the aircraft tells us it can't go to 135.375ORTAC.

KISIC.

Keep it simple, intelligent colleagues. Simple doesn't only work for stupid.

RAT 5

28th Oct 2015, 09:04

Guys!! Don't take it too literally. 3G pull up was only to make the point that the more inexperienced pilots, in their panic, over control on the escape manoeuvre and pull, or push, way outside the safety red safety boundary indicator with both hands on the stick and nothing on the thrust levers. I hope that is all clear now.

ManaAdaSystem

28th Oct 2015, 10:29

Clear as crystal!
You have pilots who panic when they get a TCAS RA. Pilots who forget to use thrust when they start a climb.

:eek:

framer

28th Oct 2015, 10:38

I'm with adasystem on that. A Tcas RA is not something that is met with panic in any airline I have flown for.

neville_nobody

28th Oct 2015, 12:19

The 737's flight deck is elegantly simple, in functional terms, and there are few things which can be misused

Yeah maybe if your last plane was an Ilyushin. A 777 is simple a 737 is not.

It can be mastered but it is not simple or easy by modern standards.

Pin Head

28th Oct 2015, 12:59

Good **** here guys, didn't realise my question would generate such passion.

Never seen deselect before until I flew with an American.

As I ve never seen it before can someone remind me the sequence of A/t and map selections just to clarify the chain of events.

On the basis of KISS, my European airline :) always says

Go around flaps 15 check thrust.

So PM after pF gas cautioned his drills,

Confirms the FMA, selects an actual flap position on PF request and confirms that two fat ladies, quack quack, 88% roughly is set.

Centaurus

28th Oct 2015, 13:25

Try doing an all-flaps up approach and landing in a 737 with ARM mode actuated and manual flying. Nearing the threshold at VREF +5 which is around 190 knots in that configuration, and especially at the flare, the throttles come alive and unless you hold them hard back they will apply thrust and you will float to buggery. Sticking to the recommended Boeing procedure covers your back side and is perfectly safe and keeps the lawyers at bay.:ok:

Kenny

28th Oct 2015, 17:42

Just to add to the discussion.

When I did my Type Rating/Endorsement about 6 years ago with Boeing, the instructors left us in no doubt that deselecting speed on final was not an approved Boeing procedure and as such they would not be teaching it. The stated Boeing philosophy was, Autopilot off, A/T off.

RAT 5

28th Oct 2015, 18:02

I'm with adasystem on that. A Tcas RA is not something that is met with panic in any airline I have flown for.

There was a case, some years ago, where an RA "Desc Now" was given at high FL.; IMC possibly. The subsequent push bounced the stewardess & trolley off the cabin roof and fell onto a pax breaking their arm. The stewardess was not in too good a shape either. No doubt many G & T's followed suit. I believe it was a LHS PF moment. I've no idea how many RA's are issued every year; might be interesting to hear. However, considering the vast dilution of front seat experience & exposure (discussed at length on PPr) & in light of AF447, it might not be too unexpected, with a CRZ F/O as PF and an SFO cockpit napping, in IMC at high level to find said newbie over reacting to a night time/IMC RA.
The sim is one thing; thinking you are going to die is another. To say it never will is IMHO one hope too far.

Centaurus: not joining the camp one way or the other, why would you keep AT in ARM all the way to flare. Would it not be sensible to click it out at DA. Surely the speed will be stable then: should be!

Capt Chambo

28th Oct 2015, 19:53

What Centaurus said....:ok:

Sticking to the recommended Boeing procedure covers your back side and is perfectly safe and keeps the lawyers at bay.

RAT 5

28th Oct 2015, 20:21

Capt Chambo: yes indeed, but the question has been asked: NOT using ARM is the recommended Boeing procedure, so how can Boeing and various XAA's sanction its use as an SOP in some airlines? The lawyers would have a field day with that one. One airline has an SOP for its use. Another airline has no comment so an individual pilot chooses to use it. Something happens; etc. etc. It's a grey area. Another airline has an absolute policy of "thou shall not". OK then, the individual is now in breach of SOP's.
Bugger's muddle.

(amazing how the topic morphed from GA to approach & flare)

Skyjob

28th Oct 2015, 21:01

how can Boeing and various XAA's sanction its use as an SOP in some airlines?

Possibly because Boeing has an NTO in this case.

For clarity for those who are unaware of what this is, an NTO is an approved change to manufacturer standards as there is no technical objection by amending the manufacturer's standard into an airline SOP.

TheiC

28th Oct 2015, 21:25

'No technical objection' <does not equal> 'no objection'.

c100driver

28th Oct 2015, 22:03

For clarity for those who are unaware of what this is, an NTO is an approved change to manufacturer standards as there is no technical objection by amending the manufacturer's standard into an airline SOP.

An NTO is not "an approved change". It means that they do not object to the technical application to the operators procedure. It is legal speak for the aircraft can do it but be it on your head.