Autopilot failure

[Adilson737]

Hello everyone!

Where can I found data about altitude loss due autopilot failures in aproach mode for B737-300/400 ?
Thanks in advance.

[Denti]

Why should there be any altitude loss? Not attacking or anything, im just a bit puzzled about that question.

[roljoe]

Hi, also doubtfull about the "point" of the question...anyway..may be you'll find some relevant info's here..http://www.smartcockpit.com/plane/boeing/B737/

[411A]

Aircraft that are certificated for the use of the autopilot for approach, normally have, in the AFM, the certification data mentioned, including the maximum altitude loss allowed by the design.

Pretty basic info, and I'm surprised it would baffle anyone, except of course, if they don't teach this in ground school anymore....and more than likely many airlines do not.:}

In addition, sometimes this information can be found in the Type Certificate Data Sheets....older models, mostly.

[safetypee]

“Why should there be any loss?”
The manufacturers have to consider any system failures that result in a nose down change if the auto pilot disconnects. Some aircraft have a trim-up bias to limit the effects of any adverse failure, the 737 employs this feature, but it might not fully counter a worse case nose down failure.

Altitude loss should be published in the AFM; it may be in the limitations section under Minimum Use Height (MUH). In European manuals MUH is normally a statement, but in FAA manuals, MUH or altitude loss is part of the Cat 2 / 3 documentation and may be shown as a diagram.

Certification requirements CS25/Amendment4 (www.easa.eu.int/home/rg_certspecs.html) covers Minimum Use Height (MUH).
See the AMC section 2-F-70 to 77, AMC 25.1329 (about pages 515-522), there is a sample diagram.

IIRC the ‘flight test’ recovery manoeuvre from a failure on the approach used a 2 sec reaction and a 1.3g pull up into a GA and the resultant flight path should not infringe the 1:29 obstacle clearance plane.

[Adilson737]

Thanks Safety typee. The Figure FT-1: Deviation Profile Method on page 615 is very elucidative.