2011-09 · NASA ASRS report 969083
With their workload increased due to repeated failures and recoveries of the FMS displays; the flight crew of an MD80 failed to level at 14000' as cleared on their descent.
Several times during the flight; the FMC display would lock-up and both the Captain and First Officer's NAV display would lose the route and MAP displays and heading fail warnings received. Each occurrence would last 15-20 seconds and then both systems would recover. However; in all cases the active route would drop out and have to be reactivated. The first time I advised center of our problem; and they cleared us direct to the next nav aid on our route. Flying Nav aid to Nav aid worked out well as when we had these momentary problems headings on the RDMIs and compass rose of the NAV display were in agreement with the STBY compass. I called Dispatch and Maintenance Control to inform them of our situation. As we approached PHX we were cleared to descend via the KOOLY3 RNAV arrival. While in the descent and on the arrival the FMC CDU locked up and the NAV Display route data went blank. I immediately told Center that we were unable the KOOLY3 arrival because of problems with the RNAV equipment but we could continue on the SUNSS7 arrival using the VOR equipment. ATC granted our request and directed us to descend to cross SQUEZ at 14000' and 250K. What I heard was cross at 11000' 250K. All of this was occurring in a very compressed time period. The flight was handed off to PHX Approach. When checking in; we were descending through 13600'. Approach queried us about our assigned altitude and I responded 11000'. They repeated that we had only been cleared to 14000' but that we were now cleared to 11000'. The Approach controller gave me a number to call after landing. After landing I did call and we discussed the incident. We both realized that our equipment malfunction occurred at absolutely the wrong time. The change in the arrival at that point also presented some problems for the arrival sector controllers. Fortunately; there were no traffic conflicts.
The controller/supervisor had listened to the tapes and realized the extent of the incident -- switching arrivals; dealing with an equipment malfunction; and changing radio frequencies. He also realized that the fix SQUEZ is on both arrivals but that the altitude restrictions are different.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
Loading the flight search…
Pick an aircraft model — Boeing 737, Airbus A320, A380, Boeing 787 Dreamliner and more — enter your origin airport, and FlightFinder shows every route that plane flies from there with live fares.
We support Boeing 737/747/757/767/777/787, the full Airbus A220/A319/A320/A321/A330/A340/A350/A380 family, Embraer E170/E175/E190/E195, Bombardier CRJ and Dash 8, and the ATR 42/72 turboprops.
Search and schedules are free. Pro ($4.99/month, $39/year, or $99 one-time lifetime) unlocks the enriched flight card — on-time stats, CO₂ per passenger, amenities, live gate & weather — plus My Trips with push alerts.
Live schedules come from Amadeus, AeroDataBox and Travelpayouts. Observed routes (which aircraft actually flew a given city pair) are crowdsourced from adsb.lol ADS-B data under the Open Database License.