When a company SOP deliberately contradicts FCTM advice without valid reason.

[Tee Emm]

One of the domestic airlines operating the B737NG is XXX. It is company SOP to have the autothrottle armed at all times in order to permit low speed protection. On a manually flown landing the pilot is permitted to deselect "Speed" so that manual throttle operation is not impeded but the AT `Arm` switch is left engaged.
This is in direct contradiction of the advice given in the B737NG FCTM that states: "The autothrottle ARM mode is normally not recommended because its function can be confusing. The primary feature the autothrottle ARM mode provides is minimum speed protection in the event the airplane slows to minimum maneuvering speed. Other features normally associated with the autothrottle, such as gust protection, are not provided"

Company management obviously made a courageous decision to display professional disinterest in the Boeing FCTM recommendation. But it makes you wonder why someone should ignore the FCTM when the reason why the recommendation is published is clearly stated in black and white.

[Sciolistes]

Absolutely no criticism of your rationale, as I agree that SOPs should be in line with the FCTM to have credibility, but I never understood how the A/T in ARM can be confusing and I can understand why VB might want to use the feature, providing they provide info/training to ensure that nobody is confused.

[latetonite]

The Boeing Company is protecting itself from the law by stating this in the FCTM, as there have been longer flares due inadvertent trottle movement during landing.
The Airline is aware of the odd go-around going wrong without proper thrust setting, and implements the landing procedure with A/T armed.
My previous carrier publishes only dual autopilot approaches in VOL 1 to circumnavigate this responsibility.
Pilots are getting confused are they think they can fly planes safely while monkey flying SOP`s.
At the end of the day, flying remains still a profession.

[mutt]

Generally an airline will write to Boeing with their proposed amendment, Boeing will issue a "No Technical Objection" if they accept the proposal.

How do you know that VB didn't do this?

Mutt

[rudolf]

The FCTM says not recommended rather than forbidden, as long as there is guidance on how the ARM function works then I don't see a problem. I fly for an airline that regularly uses this to provide low speed protection, however, we recommend not using it in gusty conditions because of the increased risk of it activating.

Can't speak for Australia but in Europe an NTO is no longer needed, as long as a risk assessment has been carried out then this will suffice.

[Denti]

We did receive a NTO when we started this 20 years ago. Boeing advised us that additional training during initial type rating would be a good idea which was incorporated into the type rating syllabus.

We never had a long landing incident because of inadvertent A/T activation, rather the opposite in some cases as the A/T reverts to landing retard mode below 27ft if it is active.

As stated above it is a good idea to switch it off completely in gusty conditions, apart from that it is an absolute non-issue.

[galdian]

Been stated before but years ago Boeing instructors stated that as 737 was often first/level entry jet then work on KISS principle ie all automatics either OFF or ON...HOWEVER in airlines with proper/sufficient training of various options available (in this case Autothrottle ARM rather than DISCONNECT) then fill your boots and use the features Boeing have made available to the maximum extent.

Monitoring rather than flying safer says Mr Boeing - makes sense.

Above applies to Control Wheel Steering, another great asset but for too many (sometimes people, sometimes authorities) simply white mans magic; all another story.

Cheers.

[Zorin_75]

have the autothrottle armed at all times in order to permit low speed protection

Isn't that a valid reason right there?

[sheppey]

Quote:
have the autothrottle armed at all times in order to permit low speed protection
Isn't that a valid reason right there?

Obviously not - since the latest 737 FCTM revision July 2011 still has the same recommendation it has had for decades of 737 operation and that is `autothrottle ARM mode is normally not recommended`. Obviously Boeing is on to something there or else what is the point of the "not recommended"? Some would argue it is better to go with the strength and accept the Boeing recommendations rather than open yourself to litigation if something went wrong. Lawyers are good at that sort of opening.

[Checkboard]

makes you wonder why someone should ignore the FCTM when the reason why the recommendation is published is clearly stated in black and white.

... because the opinion of the Boeing pilot who wrote the FCTM isn't chiseled into a stone tablet and brought down from Mount Olympus.

Just because it's an opinion from the manufacturer, it doesn't mean it's necessarily the best practice for EVERY operation around the world ...

[RainingLogic]

So do you think Boeing and Airbus designed their jumbos for 200 hour pilots?

[c100driver]

The real reason as was told to me is the possibility of tail strike as the thrust increases inadvertently at low level if you drop below min spd.

This was disucssed at a Boeing conference our fleet team attended and the Boeing flight test guys were all convinced that "all on" or "all off" is the best way to operate the machine. The Boeing guys even demonstrated the issue in the simulator to the head sheds from the training department.

Not long after that our FCOM was changed to all on or all off.

[Centaurus]

So what actually happens if the A/T Arm is left on during final approach and the pilot is using manual thrust? For example if Vref 40 is (say) 130 knots and the pilot crosses the fence exactly on Vref, do the throttles go forward to prevent the aircraft from going below Vref? After all the FCTM allows for a speed range between Vref to Vref minus 5 knots for touch down.

On a similar vein if perchance the aircraft floats with speed bleeding a few knots below Vref during the float - again do the throttles advance just when you don't want them to? And if unrestrained, how much is thrust (N1) is increased. It must be distracting for the PF when he feels the thrust levers opening up under his hand while he is manually controlling them. Seems to me Boeing made a wise decision in advising switching off the ARM mode for manual thrust

[Sciolistes]

Just reviwed fcom2 and it looks like min speed reversion works differently for different approaches and can kick in at 1.3vs (not 1.3g!). it certainly can be confusing.

[BOAC]

Centaurus and others - 'HC' to all - this 'argument' has gone around the houses at airlines and here before. (Did I mean 'discussion'...?)

Many years ago I produced a table for my 'then airline' demonstrating that if you flew correct speeds on finals, particularly at F40, the A/T would 'cut in'. It was dismissed, since - well no-one does, do they.? The 27'RA stops it 'cutting in' on an otherwise 'normal' flare thus eliminating the 'tailscrape' theory, but I flew with one 'senior' (in all respects) TC who often 'began' the flare ABOVE 27RA and we performed a terrific fly-by of the airport to tumultuous applause from the spectators.................

I eventually learned to live with it, disconnecting it around 1-200'ish when visual. The 'advantages' put to me (rolled up newspaper style) are significant:

Min speed reversion (a guarded 'plus' - ask THY)
The option of a reduced power 'auto' g/a (in manual A/T Full Power is required)

[Denti]

I guess BOAC meant the fact that the A/T does no longer provide min speed reversion below 27ft RA and instead goes into landing retard mode. Which is exactly what happened to those THY guys because the left RA showed below 27ft.

On the NG i haven't had the A/T cutting in smooth air when flown at the correct speeds, however in gusty weather it is quite common and usually solved by a simple click on the disconnect button.

[BOAC]

Alpa - THY - I know - hence the words 'a guarded plus' - it is well to be aware of the function of the RA on ANY A/T mode in the 737, in particular the false <27'RA that killed them..

Re G/A power- the 'first push' gives a CERTIFIED 2-eng g/a power and hence it is 'acceptable' for regulatory purposes for G/A. I reckon you (and all) would be incapable of working out the correct manual N1 for the min 2000fpm climb - right? Hence the need for Full Power on a manual G/A - find yourself an IRE and ask. If you do not do that you should fail an IR (in the UK anyway). I don't know about your 'land', of course.

Regarding your last two points, the answers are in the thread in which you have posted. If you do not know the Stick Shaker margins............................

Merry Christmas to you too.

[Centaurus]

while simultaneously establishing an initial pitch attitude of around 12 degrees

From 737 FCTM: ..".ensure/set go-around thrust and rotate smoothly towards 15 degrees"

[BOAC]

Originally Posted by alpa

I have long arms, so the resulting N1 will be approximatly 85-90%.

- and you are absolutely certain that '85%'ish' will give you the required rate of climb at +25deg and MLW and 2000' ASL? If you are using manual throttle, best to push them forwards and then have PNF set them to the bugs, then it will.

Part of the 'problems' in turbulent conditions arise from the use of the alpha vane to 'measure' 1.3Vs and that can bounce around a bit.

[cosmo kramer]

Alpagueur320,

FCOM2 Chapter 4:
Minimum speed is based on angle of attack and is approximately 1.3 Vs for the current flap configuration. It is sensed by the angle of attack vanes, one on either side of the forward fuselage.

Hence, with G-loading from bank and gusts, even when on correct speed, the stall speed may increase and factored with 1.3 may exceed commanded speed. Amazing that the proponents of this feature have been unable to give this simple answer, despite being asked several times.

I completely agree with you about setting go-around thrust. A well (normally) trained pilot should be perfectly capable of manually (gosh!) adjusting the thrust levers that the result is 1000-2000 feet pr. minute just like the auto throttle would have.

BOAC,
the auto throttle is does exactly what written above (gives you an arbitrary rate between 1000-2000 feet pr. min). It's not certified in any way and is no way guaranteed to give you exactly 2000 fpm. YOU have to figure out if 1000-2000 fpm is enough to meet the required climb gradient for the missed approach. Obviously mostly it would be.

Further, I would be very interested if you can point me to the document that says that I am required to set full go-around thrust in my vastly overpowered aircraft. All the documents I have seen says that I must to meet the required gradient for the missed approach.