Arming both ap for approach

[Centaurus]

A Boeing (Seattle)instructor pilot told me that the 737 Classics do a very nice autoland using just a single autopilot. There is no trimming back at 400 feet though. Since then I have seen countless737 Classic autolands in the simulator using single AP. Greasers every time.

[RAT 5]

I've heard it does it. Is it a design feature or just something that happens? 2 autopilots = fail passive such that a disconnect leaves the a/c in a trimmed state and no abrupt manoeuvres. I assume it's because the 2 A/P's talk to each other and compare notes, which is a requirement for LVO. I assume, therefore, a single autopilot can autoland in >Cat 1 but is not approved for LVO's. If that is the case why is it not a commonly taught technique, and is ti approved? An autoland in marginal Cat 1 might sometimes be useful; or other scenarios.

[Denti]

I'd argue that an autoland in marginal CAT I is a very bad idea indeed. As has been shown by a 777 from singapore airlines in munich some time ago. No protected areas, no increased separation and not enough visibility to judge whats going on at the other end of the runway...

And yes, we do CAT I autolands from both sides, but that is for training purposes, usually in much better than CAT I conditions.

Quite honestly, there is no real need for a single AP autoland, except in those very rare cases where the second AP is U/S.

[RAT 5]

Quite honestly, there is no real need for a single AP autoland, except in those very rare cases where the second AP is U/S.

Is that an approved procedure? I've flown 732(Cat 2 man land) B733/734/737/738, and for various airlines. I've never been taught. nor heard it discussed as an approved procedure.

The idea that it might be used in a marginal CAT 1 scenario is because I assume there is no nose up trim. Given, there would be no protected area, hence my thought that LVO's were not in use and you'd have sufficient time to decide, the same as you would on a manual landing but more relaxed. However, I can not say from personal experience because I've never been exposed to it. Hence the questions in good faith.

[Dan Winterland]

What could be more simpler for the average pilot than an all engines manual GA? No chance of an aileron hard-over there. After all, a one engine inoperative GA is flown manually so what's all the sweat about a two engine manual GA? You don't need a flight director for either. Unless of course one is the victim of automation addiction.

It's not simple, LOSA data shows that the all engine GA is one of the most mishandled actions and about a quarter lead to an undesired aircraft state. It's a rarely practiced highly dynamic high energy manoeuvre with lots of threats.

Second, and related to the above, we have had so many threads about a lack of manual handling skills that the idea of doing a dual channel approach in Cat 1 conditions as a matter of course appears to be evidence of a huge lack of confidence in manual flying skills.

Never a truer word. Proof of the pudding when you read Loss of Control In-Flight is now the major cause of airline fatal accidents

You have to analyse why these GAs go wrong and one significant cause of LOC-I crashes is spatial disorientation. Manually flown GAs have accounted for 7 large transport aircraft hull losses this century. It's not a case of a lack of flying skills or confidence, it's a basic human limitation. And 500 people may still be alive today if the pilot had flown the GA with the AP engaged.

[Dan Winterland]

The Trident was the first commercial operation to be cleared for AL use. The first fully operational AL system cleared for use was the RAF's Vulcan and Victor B2 force in 1962 (?) using the leader cable system.

[Denti]

@RAT 5, to be honest, as far as i know it is not approved for single autopilot autoland. It is a non-documented "feature". We never trained its use as we always use two autopilots on approach anyway, even if a manual landing is planned.

Someone mentioned above it would be better for a low disconnect height as in single autopilot operation there is no backtrim. That may be, however if trained for the backtrim it is a non issue to be honest. Same as the kick in the rudder during a single engine go around once another roll mode is activated.

[CaptainProp]

We angage both auto pilots (airbus) for any non manual ILS approach flown because the FCOM says so. Simple as that. It has nothing to do with manual flying skills, lack of trust in the system as someone pointed to. It's airbus procedure and I have never seen any company not following this procedure.

FCOM Normal Procedures Aircraft Guidance Management:

BOTH APs ENGAGE

- When APPR mode is selected AP1 and AP2 should be engaged

Having said that, in FCOM AUTO FLIGHT FLIGHT GUIDANCE Appr mode there is a note stating "Second autopilot may be selected". May, not should.

As those of you flying the Airbus are well aware of the Land and Flare mode disengages if BOTH autopilots are disengaged and also below 200' RA the Autoland warning light is triggered if both APs disengage. In other words, with two autopilots engaged you will not encounter these issues if one AP fails. Although not required for a CAT I approach this could be the reason that Airbus sops calls for engagement for both APs? Engaging two APs every time you fly an ILS approach also streamlines sops for CAT I II and III operations of course.

CP

[sheppey]

It's not a case of a lack of flying skills or confidence, it's a basic human limitation

Sorry, Dan. Must differ with you on that subject. It is a basic airmanship manoeuvre that should be taught on all aeroplanes. An all engines manually flown go-around from the flare and on instruments, should be taught as an essential part of a type rating in any aircraft; whether piston singles, turbo props, or jets. There can be no excuse for avoiding this in a simulator. Put bluntly, if the pilot under type rating training or being tested for instrument proficiency in the simulator, cannot fly this manoeuvre on instruments competently during the type rating training, then the instructor has no business in signing him out as competent. But commercial pressures on the instructor to keep within cost/time schedules often mean short cutting takes place on the quiet and the candidate is signed off when he shouldn't be.

Unfortunately, the accent during type rating training in the simulator is invariably biased from the first lesson towards full use of all automatic features. These include automatic pilot go-around manoeuvres where the press of the TOGA feature neatly disguises by default any shortcomings in the pilot's basic instrument flying ability. No problem if the main purpose is to tick the box and quickly move on to something else in the syllabus.

Spatial disorientation may well be (as you rightly say) a basic human limitation. Notwithstanding, it is also a convenient excuse often used for lack of flying ability on instruments. Even in accident reports where the investigators have a pretty good idea that a pilot stuffed up a low altitude go-around, then it is all to easy to slip in spatial disorientation as a contributing factor that explains everything; even though it can rarely be proven.

[Denti]

Thing is, no authority requires an all engine go around during training. Yes, of course it is part of the basic typerating. But with the low go around rate nowadays, in my company around one every 3 to 5 years per pilot, and no requirement to train it during simulator events, it is the least trained thing by far. Of course dual engine go arounds are trained every six months, but only during LVP training and that is on autopilot. Apart from that the only thing trained is OEI go arounds.

[Dan Winterland]

Sorry, Dan. Must differ with you on that subject. It is a basic airmanship manoeuvre that should be taught on all aeroplanes.

Read up on the somatogravic illusion. Being in Aus, there should be plenty of literature available to you from CASA. They're fairly hot on it. No matter how good you think you are, an IMC go-around is safest flown with the AP engaged.

[giggitygiggity]

@Judd

What could be more simpler for the average pilot than an all engines manual GA? No chance of an aileron hard-over there. After all, a one engine inoperative GA is flown manually so what's all the sweat about a two engine manual GA? You don't need a flight director for either. Unless of course one is the victim of automation addiction.

In your outfit, how often do you have to fly a 2 engine Go-Around? I've done 1 in the last three years. It's hardly a frequently practised manouveure so it would be pretty sensible to 'refresh yourself' with maximum use of automation. Unless your career is pinned up entirely on showing off, flying something manually doesn't always make you a better pilot does it?

[B737SFP]

I've seen a couple go arounds during the last years and I can tell you that only a few proceeded as expected.

Thanks god we have LNAV to help us nowadays, because for what I've seen, I believe things could get pretty messed up at times when all had to be flown manually and raw data.

I've tried to "program" myself during every single approach to review the steps of the go around manoeuvre, that's probably the best way to be sharp in case I have to discontinue the approach and move on.

One thing that really caught my attention is why 737 pilots tend to disconnect the auto throttle before commencing a go around. Man, this is something that really get to my nerves ! This has to be some kind of muscular memory or something (as we usually disconnect the autopilot and a/t at the same time)

I once heard from a captain, that even with the auto throttle disconnected the thrust levers would move once he press the Go Around button (I'm not talking about the ARM mode, I'm talking about a BLANK A/T mode on the FMA)...

Yeap, that was one of the most crazy ****s I've ever heard during my 6.5 years flying the 737.

Safe Go Arounds Folks !

[RAT 5]

It's hardly a frequently practised manouveure so it would be pretty sensible to 'refresh yourself' with maximum use of automation. Unless your career is pinned up entirely on showing off, flying something manually doesn't always make you a better pilot does it?

Which always makes me surprised & curious why there are some operators who have G/A profiles that are rushed, different to a normal takeoff, flown to flaps up manually irrespective of the complication of the lateral & vertical profile.

[Skyjob]

I agree it comes down to individual airlines' SOPs.
Boeing does recommend using both APs for all approaches.
If SOPs dictate otherwise it could be for many reasons that FOPS decided this course of action, old habits or being unfamiliar with the alternative being one of them.
Flying an approach dual channel on an average day is not a problem, as most pilots revert to hand flying no later then say 500'. The missed approach issue as discussed would be aided by automation in these cases.
As long as it is recognised that there is a trim issue below this, crew are aware of this and brief accordingly when weather minima dictate this may happen, there appears to be no issue.
Protected runways are only required for less then Cat 1 weather, thus this does not prevent crew using dual channel to minima and even let the aircraft land when Cat I minima exist on an unprotected runway.
Change the SOP, use the automation, or be prepared for some handling incidents when crews are caught out having to fly the missed approach manoeuvre manually late on in the approach.

[Centaurus]

Boeing does recommend using both APs for all approaches

On which Boeing type? Certainly not in the 737 Classics. Can you quote a reference for this?

[B737SFP]

I've never read anything like that on the FCOM or FCTM, nor it's my company's SOP.

I believe that 2 or 3 years ago there was a Boeing audit on our flight ops department that brought a lot of changes (our NOPs had a lot of differences from the manufacturer's suggestion), but nothing like that was pointed out by them.

If this is really something recommended by Boeing for every approach (737NG), please, I would like to know where I can find it.

Great discussion guys...

[Pin Head]

saw one the other day. I personally believe it is not allowed but what annoyed me the most was that the dual AP action was never briefed by the FO and it all came as bit of a surprise.

[Skyjob]

In Boeing's Master FCOM, this is actually described as the default mode of operation in NP - Landing Procedure - ILS [Option - Glideslope inhibited before Localizer capture], and in NP - Landing Procedures - ILS [Option - No Glideslope inhibit before Localizer capture], but not in Landing Procedure - ILS - Airplanes with IAN Capability.

Just to show there is a difference between setups.
Both answers given here are correct, depending what capability you have installed.

Of course, if flying the incorrect procedure for the aircraft flown, that's a different matter. Do you know what configuration OP is referring to? Until this has been established...

[Denti]

Interesting. We use both APs on IAN capability equipped airplanes. However, one has to be careful as only one AP is possible in non-GLS/ILS approaches and all use the same SOP set (using APProach Mode).