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The captain of a B73B miscalculated a descent profile for a crossing restr and was prompted by an ATC query before discovering that a mistake had been made. The flight crew initiated a descent, but were unable to inform the ARTCC radar controller that they would not be able to make the clearance restr due to frequency congestion.
| Attributes | |
| ACN | 332370 |
| Time | |
| Date | 199603 |
| Day | Mon |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : btg airport : pdx |
| State Reference | WA |
| Altitude | msl bound lower : 11000 msl bound upper : 23000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-500 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Route In Use | arrival other arrival star : star enroute airway : zse |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 240 flight time total : 20000 flight time type : 15000 |
| ASRS Report | 332370 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | altitude deviation : undershoot altitude deviation : crossing restriction not met non adherence : clearance non adherence : published procedure |
| Independent Detector | other controllera other flight crewa |
| Resolutory Action | none taken : insufficient time |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
In cruise at FL230 with clearance to cross kalma intersection at 11000 ft. Figured distance to descend the 12000 ft, but neglected to add 17 mi to it (distance from btg to kalma). Approaching helns intersection center asked our altitude and we replied FL230. We immediately realized the error and started down, but could not communicate with center, we would not make crossing restr because of number of users (frequency was going full time). Got at least one transmission in, but no response from controller. Handoff to approach and subsequent landing were uneventful. Obvious problem was my math which was not backed up by refiguring it again. This was partially due to trying to sort out a gate in portland and coordinate test equipment parts for our flight, on the other radio. In retrospect should have had #2 receiver 'off' on my side and let the first officer worry about the other problems.
Original NASA ASRS Text
Title: THE CAPT OF A B73B MISCALCULATED A DSCNT PROFILE FOR A XING RESTR AND WAS PROMPTED BY AN ATC QUERY BEFORE DISCOVERING THAT A MISTAKE HAD BEEN MADE. THE FLC INITIATED A DSCNT, BUT WERE UNABLE TO INFORM THE ARTCC RADAR CTLR THAT THEY WOULD NOT BE ABLE TO MAKE THE CLRNC RESTR DUE TO FREQ CONGESTION.
Narrative: IN CRUISE AT FL230 WITH CLRNC TO CROSS KALMA INTXN AT 11000 FT. FIGURED DISTANCE TO DSND THE 12000 FT, BUT NEGLECTED TO ADD 17 MI TO IT (DISTANCE FROM BTG TO KALMA). APCHING HELNS INTXN CTR ASKED OUR ALT AND WE REPLIED FL230. WE IMMEDIATELY REALIZED THE ERROR AND STARTED DOWN, BUT COULD NOT COMMUNICATE WITH CTR, WE WOULD NOT MAKE XING RESTR BECAUSE OF NUMBER OF USERS (FREQ WAS GOING FULL TIME). GOT AT LEAST ONE XMISSION IN, BUT NO RESPONSE FROM CTLR. HDOF TO APCH AND SUBSEQUENT LNDG WERE UNEVENTFUL. OBVIOUS PROB WAS MY MATH WHICH WAS NOT BACKED UP BY REFIGURING IT AGAIN. THIS WAS PARTIALLY DUE TO TRYING TO SORT OUT A GATE IN PORTLAND AND COORDINATE TEST EQUIP PARTS FOR OUR FLT, ON THE OTHER RADIO. IN RETROSPECT SHOULD HAVE HAD #2 RECEIVER 'OFF' ON MY SIDE AND LET THE FO WORRY ABOUT THE OTHER PROBS.
Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.