Hi,

 

Anyone know what the usual altitude is for disengaging the A/P on approach and landing?

 

Thanks

 

Rob

If it's not an ILS CAT III approach, whenever you feel confortable. I usually disconnect the A/P around 1500ft in good weather conditions and I may leave it enganged all the way to 500ft or even the minimums if the weather is too bad.

 

 

Anyone know what the usual altitude is for disengaging the A/P on approach and landing?

 

If you are performing a CAT II, CAT III, or maintenance verification landing, automatic approach and landing is required.

 

If you are performing a visual, CAT I ILS, or ILS-backed approach, the autopilot must be disconnected prior to 50 feet below the DH (decision height)/MDA (minimum descent altitude). These figures can be found on your approach plates.

I am not a Pilot but I normally disengage AP in FSX at about 1000ft agl and fly manually until touchdown.

Would also depend on the aircraft type that you are flying.

Also see the FCTM for procedure

Just to add, Boeing recommend Auto/THR off if Autopilot disconnected.

 

The 737 Flight Crew Training Manual (FCTM), Reference C, page 2.8, states:

“when in manual flight, manual thrust control is recommended"

 

Something to do with the human (manual control) and computer control (Auto/THR) interface, not working well together.

Well, not quite. They recommend to use manual thrust, they don't recommend to turn A/T off.

If you push TO/GA when A/T is off, the Go Around thrust will not automatically be set. If A/T is armed but not active, Go Around thrust will be set automatically.

 

 

Anyone know what the usual altitude is for disengaging the A/P on approach and landing?

 

Depends on the pilot, the airline SOP and the weather that day.

 

I know of some pilots who will kick it off at 10,000, and others who wait until turning the base leg.  Some leave it on until established on the extended centerline.

 

The absolute minimum, however, is specified in CFR 121.579 (or 135.93, if you need to follow 135 regs):

[...] no person may use an autopilot at an altitude above the terrain which is less than 500 feet or less than twice the maximum altitude loss specified in the approved Aircraft Flight Manual or equivalent for a malfunction of the autopilot, whichever is higher.

 

It continues with exceptions for various approaches, and so on, but the general rule is above.

 

 

Anyone know what the usual altitude is for disengaging the A/P on approach and landing?

There are two answers to this, one is to do with operational limitations and the other SOP, preference or technique.

 

With regards to limitations, it depends on what rules, FAA or JAA. FAA, 50' AGL, with JAA 158' AGL (why 158' and not 150 or 160? I have no idea). In addition, for a non-precision approach the AP much be disconnected 50' below the MDA.

 

Talking about real world ops, in terms of technique/preference/SOP. Often SOP is at latest the minima for a CAT 1 or non precision approach. Preference, unless I want to practice a manual approach, I usually disconnect when cleared to land, when the preceding aircraft is disturbing the localiser, when it is gusty/turbulence, etc. These things are seldom factors in FSX though.

 

As mentioned by Overload above, It is normal recommended practice to disconnect the A/T with the A/P. I usually disconnect the A/T first to aid stability. I believe this is due to the thrust/pitch coupling characteristic of the 737 (add thrust it pitches up and visa vsera), it is impractical to continually fight the aircraft as and when it descides to increase or reduce thrust.

 

 

 

If you are performing a CAT II, CAT III, or maintenance verification landing, automatic approach and landing is required.

Actually, the HGS is approved for manual (AT and AP) landing to CAT II and IIIA.

 

 

With regards to limitations, it depends on what rules, FAA or JAA. FAA, 50' AGL [...]

 

You're missing a zero.  It's 500' feet, as quoted above, in 121.579 (135.93).  The 50' reference is only in reference to approaches, which would of course be what we're talking about, but there is in no way shape or form a reference to 50' AGL anywhere in that reg.  It's 50' below the MDA/DA/DH for approaches, or as approved by the Administrator.

They recommend to use manual thrust, they don't recommend to turn A/T off.

 

Inquiring minds would like to know: do you have a reference to the source of that recommendation? The following PPRuNe post talks of an Boeing-issued operational bulletin that states the exact opposite, and in fact prohibits the use of the A/T in ARM mode during landing: http://www.pprune.org/rumours-news/512476-lionair-plane-down-bali-22.html#post7796827

 

 

You're missing a zero. It's 500' feet, as quoted above, in 121.579 (135.93). The 50' reference is only in reference to approaches, which would of course be what we're talking about, but there is in no way shape or form a reference to 50' AGL anywhere in that reg. It's 50' below the MDA/DA/DH for approaches, or as approved by the Administrator.

Hmmm, interesting, thanks for that. I'm not an FAA guy so I don't have the references, but according to my company manuals, specifically FCOM 1, Limitations, the NG minimum use height is 50' (FAA) and not more than 50' below MDA (specifically non-precision) (FAA and JAA). I operate under JAA rules (probably should be called EASA now) so no AP is permitted below 158' AGL (single channel).

 

 

 

The following PPRuNe post talks of an Boeing-issued operational bulletin that states the exact opposite, and in fact prohibits the use of the A/T in ARM mode during landing

The use of ARM for landing is permitted by Boeing pending appropriate training by the operator. But generally you are absolutely correct.

 

 

Hmmm, interesting, thanks for that. I'm not an FAA guy so I don't have the references, but according to my company manuals, specifically FCOM 1, Limitations, the NG minimum use height is 50' (FAA) and not more than 50' below MDA (specifically non-precision) (FAA and JAA).

 

The FARs are a terrible beast.  The FAA reg does state that, for an ILS approach, the autopilot may be used down to 50' above the terrain, or the max altitude loss specified by the AFM, whichever is higher.  This would be in line with your FCOM, but only in the case of precision approaches.

 

Since the original poster's question was more generic, I went with the generic 121.579a language, instead of the c language regarding ILS approaches only (the b language addresses non-precision approaches, with d addressing special authorization to couple to the ground, and e takeoff/climb-out modes).

Inquiring minds would like to know: do you have a reference to the source of that recommendation? The following PPRuNe post talks of an Boeing-issued operational bulletin that states the exact opposite, and in fact prohibits the use of the A/T in ARM mode during landing: http://www.pprune.org/rumours-news/512476-lionair-plane-down-bali-22.html#post7796827

I did not know that, thanks for pointing it out. Our guys ( & gals, thank god!) must have had the supplementary training then.

Use of the Autothrottle is recommended not to be used with A/P off but its a very delicate matter i think.

 

There is a post with a link in here regarding the crash on Bali . Autothrottle comes to discussion as Boeing do approve Company SOP with the autotrottle in different mode than the Autopilot. 

 

There is also a video showing that pilot should still should remember to train so they recommend staing away frome the FMC on occasion (children of the magenta video) and just fly the god damn plane :-)

 

http://www.youtube.com/watch?feature=player_embedded&v=h3kREPMzMLk

 

 

Michael Moe