Date: 201909
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Aircraft: B747-400
Operator: Air Taxi
Operating under: Part 135
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Altitude Alert
Component problem: Malfunctioning
Reporter organization: Air Taxi
Reporter function: First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL
Contributing factors: Aircraft; MEL
Primary problem: MEL

Narrative: The aircraft had DDG (Dispatch Deviation Guide) 34-XX-XX-XX for a radar altimeter failure. We had reviewed the issues and had been told that the aircraft had previously given some 'configuration warnings' in the descent on a previous flight. The takeoff and initial climb was without incident. Once level at 34;000 ft we began to get Left Side Radar Altimeter readings and Aural Callouts. These progressively got worse and more frequent. We tried to inhibit the Terrain and ILS functions of the GPWS but that didn't stop the callouts. We received almost continuous radar altitude call outs and 'Too Low Terrain' callouts. These began to interfere with our ability to talk to one another and communicate on the radio.We checked the DDG again and reviewed the logbook again to see if we had missed something. We found that nothing seemed to be missing from the actions taken previously per the DDG. With the GPWS callouts making communications inside the flight deck and on the radio difficult we called to speak with Dispatch and to consult with Maintenance Control. We explained the issue and the fact that we had these callouts; which they could hear. At the direction of Maintenance Control we identified and pulled the Left Radar Altimeter. This stopped all callouts and generated the message that we expected to see per the DDG; that being the NO LAND 3.It appears that the DDG is missing the appropriate steps for the Maintenance Procedure to secure the malfunctioning Radar Altimeter and to change the Cat II/III status as appropriate. The CFR 91.213 normally requires inoperative or defective equipment must be deactivated or removed.In preparing this [report] I reviewed the Maintenance Tab. I found that no DDG items for the Radar Altimeter showed as open on the date of this flight even though we had the DDG on our release. Going back a month; there were two closed. Going back further I noted that the Left Radar Altimeter had been written up 5 times [in the last few months]. There were also additional; non-specified issues with Radar Altimeter callouts using the same MEL.Please consider forwarding this issue to [Company] for review and changes to the FAA MMEL. Modify the release paperwork to begin showing the due dates to make it clear to Dispatch and pilots. Improve tracking of repetitive maintenance discrepancies. Change procedure to have all discrepancies either called in or sent in via ACARS for better tracking during line operations.




Synopsis: B747-400 First Officer reported nuisance altitude alerts in cruise flight due to incomplete Maintenance procedures.