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Autoflt and autothrottle systems of B737-800 malfunction during capture of lda with GS approach to dca.
| Attributes | |
| ACN | 783380 |
| Time | |
| Date | 200804 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : dca.airport |
| State Reference | DC |
| Altitude | msl single value : 5000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : dca.tower |
| Operator | common carrier : air carrier |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | ils localizer & glide slope : 19 |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| ASRS Report | 783380 |
| Events | |
| Anomaly | aircraft equipment problem : less severe other anomaly other anomaly |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : overrode automation flight crew : overcame equipment problem |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance |
| Primary Problem | Ambiguous |
Narrative:
Level 5000 ft with 3000 ft selected in MCP; flaps 5 degrees; autoplt on; approach armed for lda with GS runway 19 dca. Intercepting localizer; aircraft autothrottles rolled back to approximately 49% N1 and the nose pitched up to 16.2 degrees. Airspeed decreased from 170 KTS to 151 KTS (30 degrees flaps; vref was 145 KTS). I disengaged autoplt and autothrottles; added maximum power and pushed the nose over to regain airspeed. I called for flaps 10 degrees for increased lift for the recovery. At first I thought I had messed up on the programming of the MCP; we don't normally do lda's with GS and I second-guessed myself as to which mode I was supposed to be in. As it was; I was correct in the mode that I had selected. Reasons for this pitch up with power back are as of yet unknown. I have no idea.
Original NASA ASRS Text
Title: AUTOFLT AND AUTOTHROTTLE SYSTEMS OF B737-800 MALFUNCTION DURING CAPTURE OF LDA WITH GS APCH TO DCA.
Narrative: LEVEL 5000 FT WITH 3000 FT SELECTED IN MCP; FLAPS 5 DEGS; AUTOPLT ON; APCH ARMED FOR LDA WITH GS RWY 19 DCA. INTERCEPTING LOC; ACFT AUTOTHROTTLES ROLLED BACK TO APPROX 49% N1 AND THE NOSE PITCHED UP TO 16.2 DEGS. AIRSPD DECREASED FROM 170 KTS TO 151 KTS (30 DEGS FLAPS; VREF WAS 145 KTS). I DISENGAGED AUTOPLT AND AUTOTHROTTLES; ADDED MAX PWR AND PUSHED THE NOSE OVER TO REGAIN AIRSPD. I CALLED FOR FLAPS 10 DEGS FOR INCREASED LIFT FOR THE RECOVERY. AT FIRST I THOUGHT I HAD MESSED UP ON THE PROGRAMMING OF THE MCP; WE DON'T NORMALLY DO LDA'S WITH GS AND I SECOND-GUESSED MYSELF AS TO WHICH MODE I WAS SUPPOSED TO BE IN. AS IT WAS; I WAS CORRECT IN THE MODE THAT I HAD SELECTED. REASONS FOR THIS PITCH UP WITH PWR BACK ARE AS OF YET UNKNOWN. I HAVE NO IDEA.
Data retrieved from NASA's ASRS site as of May 2009 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.