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An air carrier DC10 freighter flight crew descended below their assigned altitude when the captain changed autoflt modes at the wrong time removing its altitude capture capability.
| Attributes | |
| ACN | 401609 |
| Time | |
| Date | 199805 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : eca |
| State Reference | CA |
| Altitude | msl bound lower : 27550 msl bound upper : 28000 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zoa |
| Operator | common carrier : air carrier |
| Make Model Name | DC-10 10 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : flight engineer pilot : atp |
| Experience | flight time last 90 days : 80 flight time total : 7000 flight time type : 800 |
| ASRS Report | 401609 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : instrument pilot : commercial pilot : atp |
| Experience | flight time last 90 days : 100 flight time total : 8000 flight time type : 2000 |
| ASRS Report | 401610 |
| Events | |
| Anomaly | altitude deviation : overshoot non adherence : clearance non adherence : published procedure |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Captain flying the leg using autoplt, with INS for navigation. Center gave us descent from FL350 to FL280. Captain began briefing 'approach in use' at approximately FL300. Descending through FL290 I made company call of '29000 ft for 28000 ft.' captain acknowledged. Then we continued his 'brief' with both of us looking at the approach charts. At FL276 captain saw the altitude and 'arrested' the descent and climbed up to our assigned altitude of FL280. Simultaneously center called and said continue descent to FL260. I acknowledged. Captain saw that we had programmed the autoplt to 'automatic capture' the selected altitude 'FL280,' but he had changed modes to 'vertical speed' therefore eliminating his automatic capture function. Looking at my arrival approach 'plate' I didn't notice the loss of 'altitude' selected on my light panel flight mode annunciator. Another case of no one backing up the autoplt. I saw that once I made my '1000 ft' remaining call, I didn't pay any attention. Supplemental information from acn 401610: the first officer quickly realized what was happening and alerted the captain when the aircraft was at FL276 (400 ft low). The captain instantly reacted to stop the rate of descent and brought the aircraft up to FL280. I did not see the aircraft descend more than 450 ft below assigned altitude.
Original NASA ASRS Text
Title: AN ACR DC10 FREIGHTER FLC DSNDED BELOW THEIR ASSIGNED ALT WHEN THE CAPT CHANGED AUTOFLT MODES AT THE WRONG TIME REMOVING ITS ALT CAPTURE CAPABILITY.
Narrative: CAPT FLYING THE LEG USING AUTOPLT, WITH INS FOR NAV. CTR GAVE US DSCNT FROM FL350 TO FL280. CAPT BEGAN BRIEFING 'APCH IN USE' AT APPROX FL300. DSNDING THROUGH FL290 I MADE COMPANY CALL OF '29000 FT FOR 28000 FT.' CAPT ACKNOWLEDGED. THEN WE CONTINUED HIS 'BRIEF' WITH BOTH OF US LOOKING AT THE APCH CHARTS. AT FL276 CAPT SAW THE ALT AND 'ARRESTED' THE DSCNT AND CLBED UP TO OUR ASSIGNED ALT OF FL280. SIMULTANEOUSLY CTR CALLED AND SAID CONTINUE DSCNT TO FL260. I ACKNOWLEDGED. CAPT SAW THAT WE HAD PROGRAMMED THE AUTOPLT TO 'AUTO CAPTURE' THE SELECTED ALT 'FL280,' BUT HE HAD CHANGED MODES TO 'VERT SPD' THEREFORE ELIMINATING HIS AUTO CAPTURE FUNCTION. LOOKING AT MY ARR APCH 'PLATE' I DIDN'T NOTICE THE LOSS OF 'ALT' SELECTED ON MY LIGHT PANEL FLT MODE ANNUNCIATOR. ANOTHER CASE OF NO ONE BACKING UP THE AUTOPLT. I SAW THAT ONCE I MADE MY '1000 FT' REMAINING CALL, I DIDN'T PAY ANY ATTN. SUPPLEMENTAL INFO FROM ACN 401610: THE FO QUICKLY REALIZED WHAT WAS HAPPENING AND ALERTED THE CAPT WHEN THE ACFT WAS AT FL276 (400 FT LOW). THE CAPT INSTANTLY REACTED TO STOP THE RATE OF DSCNT AND BROUGHT THE ACFT UP TO FL280. I DID NOT SEE THE ACFT DSND MORE THAN 450 FT BELOW ASSIGNED ALT.
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.