Falcon 900B - Full Perf Selection
 

Being new in the plane I am trying to sort out why after selecting the Full Perf option, the plane sometimes reverts back to Current FF/GS.

Anyone care to explain?

Thanks.

I assume you are referring to the FMZ2000.

During initialization, the FMS looks for an uploaded and learned aircraft database file to do time and fuel computations. If it does not see a file, it reverts to Current GS/FF. In this case to get FULL PERF you must manually populate the data fields. On subsequent legs, you should not see it revert. This often happens on the first leg after an FMS unit is serviced or the database was reinstalled.

Hope this helps,

Kevin

I select FULL PERF during initialization and sometimes while enroute it will revert to CURRENT FF/GS... When I try to re-select FULL PERF it will not accept it.

I'll re-check during initialization that all data fields are populated.

Thanks!

I've seen this issue with Honeywell on other aircraft. Usually, it happened when someone went in and changed a default setting, it would result in inaccurate computations and would revert to the mode you mentioned. You might try checking all the settings in the FULL PERF section..if you want to make a change in flight, try the WHAT IF PERF option rather than changing the settings in the FULL PERF pages.

Is this a new FMZ unit or has there been changes to the software made recently? I've seen that on newer A/C and if I remember correctly it is because the FMS doesn't have enough flights in the system to compute an "average"...if you will. After enough legs the Full Perf. feature will always be available. Could be wrong but that's what comes to mind.

This is possible but it sounds like on occation Jetflyger initially has full perf until some time during the flight. I know the box is designed to automatically revert to CURRENT GS/FF if the data becomes invalid for some reason.

I might look into why the data might have become invalid either through crew inputs, a set-up issue seeing bad data (cross-talking), or an internal issue with the box.

Kevin

True. In flight the box sometimes revert to Current GS/FF. Not a new box or any software changes. We normally operate Independent (not Dual) and transfer data between the two boxes after changes has been made. I'll take a look at the data and see if there's something that doesn't make sense.

Thanks again.

Hey Jet,

Not sure if you found a solution but I came across this Honeywell FMS news letter: http://www.honeywellaes.com/servlet/...7B36EMNJ4N0FXS

In the question and answer area at the end there was this question and answer:

Question 14: What will cause the system to drop from FULL PERF mode to CURRENT SPD/FF mode and
display the message FULL PERF UNAVAIL?

Answer 14: This is generally caused by a corrupted aircraft data base. This problem can be resolved by either
reloading a previously saved customized version of the aircraft data base or reloading the basic
aircraft data base file for that aircraft type contained on navigation data base disk 5.

Hope this helps,

Kevin

Kevin,

Thanks. I'll check with the mx and see if they can reload disk #5.