737NG LNAV arm before take-off

[koeletom]

Hello All.

With older 737 NG (Honeywell AP-710) and Collins 737 NG I see the LNAV engaging on ground instead of arming as expected.
The FMC used is 10.8a.
We see the same on simulator and real aircraft.

Does anyone know how this works and/or has a solution to this issue?

[FlightPathOBN]

Check the buglist for 10.8A....not sure if that is one of the MANY issues...perhaps go back to 10.7 and see if that clears it up...

good luck..

[dcman]

I have seen this as well. The system is supposed to remained armed until aircraft reaches 50' RA. If I see this, I personally de-select LNAV on the ground and re-select it at 400' per company policy to ensure proper sequencing.

[koeletom]

Buglist

Hello all,

Thanks for the reply.
Does anyone know where the buglist is published?, cause its hard to find with google...(or I am blind)

Going back to 10,7 shows the same problem.

Thanks in advance

Koeletom

[FlightPathOBN]

Here is what 11.0 is supposed to include/fix...

Update 11.0

1) Route 2

2) Improvements to LNAV Control Laws

3) Enable Cruise Descent to Sequence into a PATH Descent

4) Use transition altitude and transition level from the airport record

5) Altitude Intervention Revision

6) Enhanced Takeoff Error Checking

7) Allow the FMC to change flight phases during holding

8) Connect the EO SID Trigger to the Branch Point

9) Down track RNP Alerting

10) Use Airport Mag Var for Non-CF Approach Legs

11) Enhance FP Aux data

12) Optimize the Waypoint Linked List

13) Improve LG/PP interface

14) Improve bypass (flight plan revision) generation

15) WGS-84 model (all legs)

16) Enhance Handling of Runaway IRS

17) Large Area Display System (LADS) for 737-C for SWA, base changes only



It will also have the necessary bugfixes for U10.8A which include:

• Dual FMC Restart Due to Unsent ADS Messages
• Intermittent Altitude Intervention Function
• FMC Software Restart Due to Crossover Altitude Computation and the Speed Propagation Feature
• Display of “FMC DISAGREE − VERTICAL” Message during FMC descent in the approach environment.

Version 10.8 upgrade of the FMC software has the following features, this was taken out of service pretty quick due to dangerous 'anomolies'...

1. VNAV Armed Before Takeoff

2. Improved Engine-Out Logic

3. Improvements to Software Exception Handling Logic

4. Aviation Partners Boeing (APB) Winglets on 737-300/400/500 aircraft:

5. Increase Navigation Data Base (NDB) size to 16 megabytes:

6. Enhanced CFM56-7B26B2 Engine Rating:
In-Service Problem Report Fixes:

Bug fixes the bus interrupt overflow condition for the dual FMC failures.
Bug fix to updates the FMC DISAGREE message logic
Bug fixes the following software exception issues found inservice by the operators

Version 10.8A fixed the following: (note the dual FMS only fixs)

• VNAV commanding the airplane to descend below the expected path on approach, Ref Flight Crew Operations Manual Bulletin, TBC-79.
• Give proper descent path predictions/guidance for VNAV operation into airports above 10,000 feet.
• Allow full CLB thrust after a derate takeoff thrust has been uploaded via ACARS when the PERF Option code Zero is enabled.
• The FMC ACARS data buffer from filling up with a subsequent FMC restart.
• Position Hold Symbol displayed on the right display and expanded hold is displayed on the left display.
• FMC Disagree for certain vector/waypoint combinations (Dual FMC only).
• New advisory level message "FMC DISAGREE - VERTICAL" during VNAV Path Descents (Dual FMC only).
• A fix to correct a condition where an up linked Flight ID is not stored properly in the right FMC (Dual FMC only).
• Various in-service flight plan related software exceptions.

edit..while looking, I found this very good article on FMC NDB capacity...
http://www.mitre.org/work/tech_paper...24/12_1324.pdf