B737 autopilot

[RAT 5]

I am doing some research for out training dept., and would like collect SOP's from various colleagues. The family of B737 doesn't matter, classic or NG.
When do you engage A/P on departure, 2 engine G/A, engine failure on takeoff, SE G/A?
Boeing says the A/P is available after 400'agl and is designed to reduce workload. Who uses it to the design capability?

many thanks,

[TolTol]

A/P on departure:
When N1 thrust mode engages (1500').

2 engine G/A:
After ALT HOLD, or when flaps are up.

Engine failure on takeoff & SE G/A:
When flaps are up and after P.M. has engaged level change and maximum continuous thrust.

Hope this helps.

[Olendirk]

hmm why to fly the whole 2 enigne GA by hand in an busy area of traffic? can you explain that?

cheerio

[5150]

Above 400' we put A/P in on normal departure.

[Permafrost_ATPL]

2-engine DEP and G/A: 400'
EFATO and SE G/A: flaps up

British NG operator

Cheers

P

[TolTol]

hmm why to fly the whole 2 enigne GA by hand in an busy area of traffic? can you explain that?

Cant explain, just company procedures for the NG, earliest is when flaps are up.

[despegue]

Recommended to handfly the aircraft until at least 10.000', with or without
F/D unless weather/traffic/fatigue issues.

Never heard of an airline where on B737 you put on the autopilot at 400' already. Are they joking?!

[Shiny side down]

If the environment is busy, then the autopilot probably goes in after 500' (but before 1000') just to keep the workload sensible for the other guy. London, New York, etc.

If it's less busy, then I like to fly the departure using normally LNAV/FD, or until vectors put us on a straight line, or we get held at an intermediate level for a while. Preferably up to 10000'. I include it in my brief normally.

I do know some people who chuck the autopilot in as soon as possible, irrespective. I haven't managed to get bored of flying yet.

[5150]

Never heard of an airline where on B737 you put on the autopilot at 400' already

Not joking.

From Boeing:
"The autopilot is certified to allow engagement at or above 400 feet AGL after takeoff"
(737-600 - 737-900)

If you fly 'all types' it might be worth having a look through your FCTM. . .

[rogerg]

400' is normal for most airlines I have flown for, thats if you want to.

[RAT 5]

Folks: many thanks for the replies. What I'm really interested in, and some have hinted at it, is why the a/c is certified to engage A/P above 400' agl on Dep or G/A, but some airlines choose to wait until Flaps up and thus increase worK load and IMHO reduce safety in busy TMA's.
Further, why do some engage A/P at 400 on 2 engines, when life is normal, but wait until flaps up on SE when life is non-normal?
And please dont' say becasue our SOP's say so. That is because your current C.P wants it that way. It is not the way Boeing designed the a/c. If there are any Boeing T.C's out there will you please enlighten us. It is not possible to get a direct reply from Boeing; it has to done via the company, and they are not always responsive to radicals.

To those who wish to aviate, I too endorse hand flying, when appropriate, to all levels. I've had F/O's who've never hand flown above FL100. Soon cured that; no problem. One day it might be necessary. RVSM is not the place for it though; but a u/s A/P should not ground the a/c.

[despegue]

5150,

I do know the FCTM...
What I mean is that I know of no airline where it is SOP to engage autopilot on its minimum engagement altitude.
Remember that automatics can do faulty things, and that the autopilot is prone to "peculiarities" on the classics.
That said, in environments like JFK, Heatrow etc. I put on the automatics after 1000' as this is our company minimum, but keep guarded yoke/throttle until 10.000'.

Never put full trust into automatics, and remember, if in doubt what it is doing, disconnect and fly the aircraft.

[Pilot Pete]

RAT

Possibly for commonality across different fleets?

PP

[5150]

Thanks for that. . . . . .

[fivegreenlight]

Hi Rats

"Further, why do some engage A/P at 400 on 2 engines, when life is normal, but wait until flaps up on SE when life is non-normal? "

One answer is that when SE if you engage the a/p too early you might get a descent just when you don't need it, the a/p will attempt to maintain a speed rather than the altitude. Once in altitude hold at 'up speed' ( ie flaps up) the a/p is engaged. I guess the a/p isn't as sophisticated as we'd like it to be.

[RAT 5]

FGL:

That last answer has me foxed. The A/P will be engaged with he a/c climbing. The AFDS will maintain the speed at which the engine failed V2 - V2 + 15. This is done with pitch. It should do no worse than level off to accelerate. Hand flying the F.D. will do exactly the same.

When the Flaps are UP, after an MFRA or 1000'agl, you will likely be <2000'agl at nominal ATOW"s. Thus you will not be in ALT HLD.

PP: Commonality across fleets? When discussing things with an Airbus TC, who knew nothing of Boeings (and I know litle of Airbuses) he was astounded that common airline SOP's on Boeings were so archaic with A/P use on departure with non-normals e.g. engine failures.

Question: A/P engaged on departure at 1500'; not yet Bug UP and accelerating to retract flaps; engine fails. Do you disconnect the A/P?

Answer: I hope: No. You apply rudder to stabilise the a/c, BUg Up and retract Flaps and climb to suitable altitude.

If this is OK, why not engage the A/P earlier, say 1000', with an engine failure at lower height or speed? It is so certified. Why do we down-grade the a/c to a Low Tech version of a High Tech a/c? We use the automatics and most other things within their limitations and the way they were designed, so why not in this case? It has often seemed to me that SOP's are carried over from old generation a/c to newer ones to suit company philosophy, which has inertia. No-one questions it and so it stays. It is only when a whole new type of a/c arrives that minds open up. I saw this in an old company of mine with an old tech Boeing a/c. It was Flaps Up A/P engaged. The A/P was certified for 400'agl and was so used by a later operator I flew for. The first airline then bought a brand new high tech Boeing. The first LTC's had only Boeing sim experience and a few sectors in the USA. It was their first LNAV VNAV computer a/c. It was a 20 year leap in technology from what they were used to. The new SOP for the first year was A/P on at 400' and watch what it did. Let the a/c teach the pilots what it wanted to do. Meanwhile the old a/c was still flown in the old way.
I flew B767 for another airline, my 4th on type, and the SOP manual had some oddities. It had been writen by and old company pilot who had been on B707. Guess what; "if it was OK for that beast it was OK for this one". Same c@&p; hand fly engine failures including complicated emergency turns, plus other very non B767 procedures. I wonder what the insurance boys will have to say if you pile in on departure with a non-normal hand flying when the A/P was available? Following orders Guv!

I have my thoughts about this , but as I said, I'm looking for some real technical reasoning why so many do it the way they do, and do not make life easier.

[excrab]

RAT 5,

my copy of the FCTM states that "the autopilot is FAA certified to allow engagement at or above 1000 ft AGL after takeoff" (300 - 500) and "at or above 400 ft AGL (600 - 900)".

The UK CAA also says 1000ft for the 300 - 500, don't know about the NG.

Because of this the family of 737 probably will make a difference to company SOPs.

[Pilot Pete]

PP: Commonality across fleets? When discussing things with an Airbus TC, who knew nothing of Boeings (and I know litle of Airbuses) he was astounded that common airline SOP's on Boeings were so archaic with A/P use on departure with non-normals e.g. engine failures. I meant across Boeing fleets, as per excrab's comment.

[fivegreenlight]

Rat5, just to clarify, once in level flight , accelerating towards 'up speed', speed protection can actually give a descent.
When on a S.E missed apprch we climb to accel alt, then accelerate by calling for up speed. At high GW this is virtually a level segment. It is during this portion that a descent can occur.
Used this in 3 companies on the 737.

[A37575]

[QUOTE] but some airlines choose to wait until Flaps up and thus increase worK load and IMHO reduce safety in busy TMA's. /QUOTE]
What's the problem - are you frightened of a little bit of hand flying. Reducing safety is absolute rubbish. One dark night in a thunderstorm you will need hand flying skills and if you are a total automatics monkey then you should not be flying.

[Denti]

My FCOM states:

[737-300/400/500]
Do not engage the autopilot for takeoff below 1000ft AGL

[737-700/800]
Do not engage the autopilot for takeoff below 400 ft AGL.

Since we do mainly fly the classics (first NG arrives in around 10 days) our SOPs still require to handfly on a normal take off or single engine take off until we have cleaned up the aircraft.

Since all ILS approaches are flown with dual autopilots a normal go-around before we switch to manual flight will be fully automatical which reduces the workload considerably. However switching to manual flight is encouraged before 400ft so we do not have to fight the trimming forces. Personally i switch to manual flight way before that (either raw data from the beginning or manual after GS intercept), except if visibility is marginal and a go-around is likely.

[A37575]

Since all ILS approaches are flown with dual autopilots
I might be missing something here - but I thought the only time you are supposed to engage dual autopilots for an ILS is if the intention is to conduct an autoland (737) . And one important reason for dual autopilot is for the automatic go-around facility which may happen so close to the runway that the wheels may touch and that it is well nigh impossible for the human pilot to break visual at runway level and then not only decide he is not well placed but also to hand fly after barely a second of visual segment.


On the other hand a single autopilot ILS can be flown within the same flight path accuracy as a dual autopilot ILS to the minimum disconnect height of 50 ft and if not visual the autopilot is disconnected and a manual GA conducted. There is simply no point to making a dual autopilot approach just because a GA may be needed. So what? A competent pilot should have already been certified to conduct manually flown go-arounds both all engines and one engine inoperative. The danger is disconnecting the dual autopilots below 400 ft when landing is assured and then being caught by the significant mis-trim which was automatically applied on dual autopilot at 400 ft.

[RAT 5]

A37575:

To answer you first. I had heard some some curious 'go their own way' pilots who did this as a matter of course. Very non-standard. They considered that in the event of a G/A they would have the luxury of an A/P G/A. They did this even in VMC conditions on the assumption that they would disconnect before the nose-up trim was introduced. I agree with your sentiments about flying abilities.

Denti:

Your C.P seems to be misguided in many matters. A dual A/P approach with a requirement to disconnect before 400'agl. Hm? Curious. What consideration is given to Wx & minima? Close to Cat 1 on a Cat 1 installation? But then a man land? What do you do for a NPA? What do you do for a visual approach? Either you can fly a manual G/A or you can't!

Secondly; and back to my original question, and your company seems a classic example of misusing the NG a/c. You are flying a dual A/P approach expecting a manual landing. Requirement to disconnect before 400' agl. You also fly an NG a/c certified to engage the A/P at 400' agl on departure but you do not do so until flaps up. Why?

Somewhere I am missing something because this seems a crass condradiction of not using the a/c the way it was designed.

People: Why do we wait until Flaps up before engaging the A/P?

And once again: If the A/P will descend the a/c before ALT HLD so will the F.D. but it wont. It will accelerate in level flight V/S = zero to regain speed if below V2. It will desend if you do not fly the FD accurately.

And to answer A37575's earlier post about hand flying on departure. And Oh dear Mad Macho MIke has been Munching on the Crunchy bars and Cracking coconuts between his biceps again. The old argument of Right stuff versus common sense. I can, if I want to, fly the Red Bull air race course inverted with one eye closed. No bother. I might kill myself, and hopefully only myself.
On a dark ****ty night with a major failure, siiting at the sharp end of an aluminium tube full of pax + me, is not the time to show a 500 hr sprog what a Top Gun star I am. It is the time to use whatever resources are at hand to deliver all said & sundry to terra firma in one piece with no more broken than the original failure. That is what medals are won for. Scaring **** out of myself is left for days off in the right type of a/c on my own. If the A/P is broke I can handle it, but if it ain't broke then I am expected to use it. The F.D. is certified down below CAT 1 minima. Will anyone stand up and advocate flying LVO manually? Nuff said.

A skillful pilot is one who uses his skill to aviod situations where his skilled is needed to extricate himself.

Can anyone answer the original question from a technical reason?

[xetroV]

Our company operates both classics and NGs. Our SOPs prescribe a minimum AP engagement altitude of 1000 feet for both types, just to standardise on the lowest common denominator (being the classics). I think differentiating between the classics (certified above 1000 feet) and NGs (certified above 400 feet) would just increase the chances of inadvertent mistakes without offering any significant operational or safety benefits. We also use 1000 feet as the minimum AP engagement altitude in case of an engine failure during takeoff.

In the simulator the autopilot may slowly descend during one-engine acceleration. It shouldn't, but it does, sometimes. Especially if the engine failure occurs during a reduced thrust takeoff and the crew does not set maximum takeoff thrust on the operating engine. This might be more of a problem for the classics than the NGs, but still. However, I don't know if this simulator behaviour is realistic - never had an engine failure in real life.

[Denti]

RAT 5 you have to read a tad more carefully :)

As i said at the moment we operate purely Classics with the first NG arriving in around 10 days.

As i said above, it is recommendet to switch to manual flight before 400 ft AGL if you intend to do a manual landing, however you can happily let it fly down to 50ft and then disconnect for that, in fact that is actually trained to show us the effect of the trim up which is not at all hard to overcome if you are prepared. Of course that only applies to ILS, NPAs and visuals are flown with single autopilot or raw data. Raw data flying is heavily encouraged and i fly quite often into the london tma from cruising altitude manually and flight director off until touchdown.

Dual channel approach is recommendet because there is a possibility of a single channel autopilot hardover which actually happened in my company, if you use dual channel autopilot you wont get that but instead just a disconnect of both autopilots (every CAT D simulator can simulate that, just try it). As a plus you allways have automatic go-around capability and can allways switch to CAT II or III whenever you need to.

I have just rechecked and the autopilot actually may be used above minimum autopilot engagement altitude during take off, so 400ft in the NG is perfectly fine. That just recently changed in the ongoing standardization over the whole boeing fleet in our airline group and as i'm not officially trained on the NG yet (have to do a difference training consisting of CBT, selfstudy with a differences manual, written test, a simulator session and 5 days of supervision on the line) i wasn't really aware that with the NG our company now allows engagement at 400ft AGL.

[RAT 5]

Denti: Thank you for your input and I apologise for any short-sightedness.
To others, many thanks for your contributions. I see there are those who engage A/P at 1000' agl and those who wait until Flaps Up. It seems that the difference is the whim of the Chief Pilot and company SOP's. OK; so we have a difference and neither is the Boeing design criteria.
My question still stands. Can anyone provide a technical reason why the Boeing design standard is not applied? I understand that those who operate a mix fleet of classics & NG's chose the lowest common denominator of
1000'. Fine. Why is the UKCAA cerification 1000' and the FAA 400'? Why, if the NG is 400' do those operators choose Flaps up? What is the technical reason?

I once flew for an operator who cleaned up at 1000' on a V1 cut, SE G/A & 2 engine G/A. Keep it simple and all the same. Seemed like a good idea. It is above Boeing minima. Then I flew for an operator who cleaned up at 1000' on a V1 cut & SE G/A but 400' on a 2 engine G/A because it was standard Boeing, but still waited until Flaps Up to engage A/P. You understand my wondering at people's thinking? They use some of standard Boeing Ops but not others in the same manoeuvre.
Why do we operate the a/c down to Boeing minima on landing close to the ground ( the rock hard place) but some choose to make their own minima when climbing away from the rock hard place? It beats me! How many people get an instruction manual for a micro-wave and then choose to do it differently?