737 autoland

[alexban]

Hy!
Does anybody know where I can find the limitations of the autoland system in regard to the glideslope angle? I remember reading some time ago,something like autoland authorized for GS between 2.75-3.25 degrees ,but I can't remember where I read that.I would like to know this for sure,cause we fly to some airports with GS of less than 2.75 or more than 3.5 degrees.
I didn't find it in the AFM or FCTM ,where else?
Thks
Alex :ok:

[Flight Detent]

Hi Alexban,
Yeah, the limits you want are 2.5 to 3.25 degrees, with 30 and 40 flaps, and both engines operating.

Also, the autoland system is not certified for overweight landings, an approach on autoland is OK, but must disconnect and land manually.

I have these figures in my AFM. (B737-6/-7/-8/-900 airplanes.

Cheers

[Phoenix_X]

What exactly is an 'approach on autoland?'

[Flight Detent]

Hi PX,
If you don't know what I mean, you don't need to know!!

Cheers

[FlightDetent]

Ph_X: Judging from your profile, it is beneficial that you know. :}

So,
on a 737 (-3/4/500 in my case) approach on autoland would normally be a dual (i.e. ALL) channel approach that legally and technically prepares the AFDS for an autoland. Remember, both APs can only be engaged above 800ft RA. Then, the segment between 800' and 50' is an approach on autoland. In case you had a soul on board in need of urgent medical care, this may put you in a LVO overweight situation, see above.

Also, it is worth a mention, that your every-day single AP APCH is also an approach on autoland, since should you all of a sudden forget to fly, single channel WILL flare and land just as properly as any pilot, albeit without the system performance integrity monitoring associated with dual channel operation.

Strangely enough, CAT II manual landing is also approach on autoland, since your DH is at 100', but below approx 140' (on all approaches) the AFDS already is on autoland regime! This is best witnessed if either/all glideslopes fail, as nothing happens because vertical guidance is already provided by RA only.

Cheers t(w)oo,
FD.


At the end, you haven't been just a quibbler, have you?

[LEM]

Also, it is worth a mention, that your every-day single AP APCH is also an approach on autoland, since should you all of a sudden forget to fly, single channel WILL flare and land just as properly as any pilot, albeit without the system performance integrity monitoring associated with dual channel operation.

Hi FlightDetent, interesting, didn't know that.
Coud you quote the source of this information?
Thanks

[Phoenix_X]

Well, it might have been a slight joke :).

Though I've never heard it referred to as an 'Autoland approach' but an autopilot/dual autopilot coupled approach. An Autoland in my mind has always been the last bit where the aircraft puts itself down onto the tarmac.
So the way I've always heard things termed makes it sound strange to do an autoland approach with manual landing := .

I didn't know, though, that the single channel would flare? If I hadn't moved on to another aircraft type I'd love to try that in the sim. Do you have any references for it?

[Hobo]

The single channel will flare and land the aircraft because it all is done on RA at the end. It is mentioned in the tech manual.

Very useful if you were in the unfortunate position of taking off in low vis (with only the suitable Cat 1 return alternate max allowable distance away) with an uncontained fire after take off. The option would be there to do a quick radar circuit followed by a single channel, possibly single engined autoland. Think of the BOAC 707 that relanded on 05 at LHR in the late 60s (?) if the London area had been fogbound what would have been their fate?, I can only speak for the 737-200 but I would assume this would work on later models.

[4Screwaircrew]

Boeing Tech Manual offers the following regarding single A/P approaches.

Full automatic approach and touchdown capability are not available. FLARE is not annunciated, and stabilizer trim bias is not applied.
An A/P go-around is not available.
The FCTM instructs "For single autopilot operation, the autopilot must be disengaged no lower than the minimum altitude listed in the limitations chapter of the operations manual. ( 50 feet AGL at my airline)
It further states that for a CAT III that both engines and autopilots are required to be running and engaged.

Limits on glide slope for an autoland are as stated 3.25-2.5.

[alexban]

As I knew,single pilot autoland is not available. Flare is not armed,but I'll check it in sim next month ,and i'll see.But I think 4screwaircrew is correct.
Alex


4screwaircrew can you tell me exactly where are the limits indicated.I ,somehow,couldn't find them.thks

[NSEU]

Not familiar with the Classic, but the 737NG Boeing Maintenance Manual (22-11-01) has this to say:

"Single Channel Flare

Automatic flare is for dual channel approach, however, since it is part of the A/P design, it can function during single channel approaches. The flare mode does not annunciate on the FMC in a single channel approach. The autopilot should be disengaged manually when the airplane reaches the decision height"

Re 4Screwaircrew's quote:

"Full automatic approach and touchdown capability are not available. FLARE is not annunciated, and stabilizer trim bias is not applied.
An A/P go-around is not available."

The two quotes can probably sit happily, side by side, without too much fiddling ;) "Full automatic approach" probably means that the autoland has all the aircraft's safety features operating, such as stab trim bias, go-around, etc.

The Classic may or may not be similar to this.

Rgds.
NSEU

[fruitbatflyer]

I have a cryptic note in my 'good guts' book for the 300/400 that says 'can do single engine autoland (dual channel) at flap 15 in emergency provided APU used as second generator.'
Can't remember actually trying it in the simulator, but it would seem reasonable if the visibility was down and you had lost an engine and had a good reason for not diverting to your takeoff alternate. One could write up how you did it and why you did it in the ensuing incident report and no-one would notice or care, methinks, as once it is an emergency the gloves are off - even Boeing allows that if I read the preface to the manual correctly.

[4Screwaircrew]

alexban limits are in my company part b.

fruitbatflyer according to the FCTM "The use of dual autopilots with an engine inoperative is not authorised"

If you were to make an approach with one engine at idle you are as good as single engine but following the letter of the book if not the intent, and I believe the sim will fly that quite well.

I am in the sim next week and will try to have a look at an approach with only one auto pilot and report back. I think it will be like a dual channel approach with a fail in the flare mode, no danger of aquaplaning off one of those;)

[4Screwaircrew]

I tried it and it smacked into the floor, no flare at all. Which is exactly what the TRE said when we discussed it.:(

[alexban]

I thought so.The book says 'no flare available,no bias trim.'So it was to be expected.What was the Vs,did you retard engines?I think it hit with 600 f/min,right? too hard
Alex

[METO power]

Hmm........ Thats strange. I tried it as well, and it made a perfect Autoland on one Autopilot, one engine out and single AC source (no APU). Maybe ours hase a different config.

[FlightDetent]

Ours also lands nicely. I wonder if it has anything to do the AP installed. I cannot find it in any book I have access to. However, the whole issue was brought to my attention by our 737 top experienced examiner while on a semiannual LVO check ride. He claimed to have it discovered by chance whilst studying DFDR downloads.

FD.
Mind the gap!

edited for typos

[alf5071h]

For those Ppruners who are using the simulator as a research tool – take care with your conclusions. Training simulators are rarely configured to fly procedures that are not authorized i.e. single channel autoland. Furthermore different simulator manufactures may use totally different techniques for their simulation, hence the differences seen by METO power and Flight Detent. I knew of one aircraft type that in one simulator the autopilot was part of the simulation and in another the real autopilot equipment was used. Simulators are clever and capable video games, but they are not real aircraft in a real world.

There are many hazards with flying unapproved procedures. Whilst it may appear to be a good plan to return on a ‘single’ Cat 3 autoland after a fire, any one subsequent system failure (ground or air) may result in a hazardous maneuver – hard nose down pitch or no flare. The requirements for dispatch / diversion cover situations such as a fire after take off in limiting weather; these have considered the probabilities of failure events and the options open to the crew; therefore crews should always follow the approved procedures and stick to the limitations

[BOAC]

Well, here's one pilot who would have to be pushed VERY HARD into a VERY VERY TIGHT corner to try this!

It may well be that it WILL flare and land s/c and or s/e, it may not, but all this confusion could be a certification issue, where, as alf says, Boeing cannot be certain that protection willl be assured, so they will NOT certify it. As he also says, beware the simulator. It is only a computer. You and your passengers will not be injured in it.

My opinion - unless this is your absolute ONLY option, forget it.