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An SA227 metroliner first officer reports the remote possibility of having reversed both engines in-flight.
| Attributes | |
| ACN | 557013 |
| Time | |
| Date | 200208 |
| Day | Sat |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | msl single value : 5000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : zzz.tower |
| Operator | common carrier : air carrier |
| Make Model Name | SA-227 AC Metro III |
| Operating Under FAR Part | Part 119 |
| Flight Phase | descent : approach |
| Route In Use | approach : visual |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : commercial pilot : instrument pilot : multi engine |
| Experience | flight time last 90 days : 155 flight time total : 2440 flight time type : 1440 |
| ASRS Report | 557013 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | other flight crewa other flight crewb |
| Resolutory Action | none taken : detected after the fact |
| Consequence | Other |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
Narrative:
During a visual approach, approach control requested 'maximum forward speed until final, and keep your base in close.' thus, I kept the indicated airspeed at just under vmo. I knew the only way to bleed the speed off in time to configure for landing was to rapidly bring the power levers all the way back to the flight idle stops (thus sounding the gear warning horn). As I was about to turn final, I began quickly retarding the flight levers. The gear warning horn sounded as expected and I continued to retard the power levers expecting to hit the flight idle stops. However, before I hit the stops, the propellers made a loud sound similar to that of when they go into reverse. When this happened, I quickly pushed the power levers back forward until the gear horn stopped sounding. I then noticed the ignition lights were illuminated (indicating the propellers had sensed a negative torque condition). I did not notice what airspeed we had slowed to but continued to slow the airplane, configured for landing, and landed without incident. Once on the ground, I reviewed the situation with the captain and discussed certain scenarios. The only option I could think of was that I had lifted the flight idle locks thus allowing the power levers to go beyond flight idle into ground idle. This option didn't make sense for 2 reasons. During our postflt, we asked a mechanic what his thoughts on the situation were. He said that at that airspeed if the propellers were cruised up (96% RPM -- which they were) and the power levers were brought back very quickly, then the propeller governor could possibly sense a conflict by rescheduling the fuel control unit (which occurs about 97.5% RPM) between the propeller governor and the underspd governor, thereby causing some erratic pitch changes in the propeller which could simulate reverse mode. This scenario seemed the more likely scenario because of the reasons stated earlier. However, I have played the events over and over in my mind and I cannot determine definitively whether or not I touched the locks or whether or not the power levers were brought into ground idle.
Original NASA ASRS Text
Title: AN SA227 METROLINER FO RPTS THE REMOTE POSSIBILITY OF HAVING REVERSED BOTH ENGS INFLT.
Narrative: DURING A VISUAL APCH, APCH CTL REQUESTED 'MAX FORWARD SPD UNTIL FINAL, AND KEEP YOUR BASE IN CLOSE.' THUS, I KEPT THE INDICATED AIRSPD AT JUST UNDER VMO. I KNEW THE ONLY WAY TO BLEED THE SPD OFF IN TIME TO CONFIGURE FOR LNDG WAS TO RAPIDLY BRING THE PWR LEVERS ALL THE WAY BACK TO THE FLT IDLE STOPS (THUS SOUNDING THE GEAR WARNING HORN). AS I WAS ABOUT TO TURN FINAL, I BEGAN QUICKLY RETARDING THE FLT LEVERS. THE GEAR WARNING HORN SOUNDED AS EXPECTED AND I CONTINUED TO RETARD THE PWR LEVERS EXPECTING TO HIT THE FLT IDLE STOPS. HOWEVER, BEFORE I HIT THE STOPS, THE PROPS MADE A LOUD SOUND SIMILAR TO THAT OF WHEN THEY GO INTO REVERSE. WHEN THIS HAPPENED, I QUICKLY PUSHED THE PWR LEVERS BACK FORWARD UNTIL THE GEAR HORN STOPPED SOUNDING. I THEN NOTICED THE IGNITION LIGHTS WERE ILLUMINATED (INDICATING THE PROPS HAD SENSED A NEGATIVE TORQUE CONDITION). I DID NOT NOTICE WHAT AIRSPD WE HAD SLOWED TO BUT CONTINUED TO SLOW THE AIRPLANE, CONFIGURED FOR LNDG, AND LANDED WITHOUT INCIDENT. ONCE ON THE GND, I REVIEWED THE SIT WITH THE CAPT AND DISCUSSED CERTAIN SCENARIOS. THE ONLY OPTION I COULD THINK OF WAS THAT I HAD LIFTED THE FLT IDLE LOCKS THUS ALLOWING THE PWR LEVERS TO GO BEYOND FLT IDLE INTO GND IDLE. THIS OPTION DIDN'T MAKE SENSE FOR 2 REASONS. DURING OUR POSTFLT, WE ASKED A MECH WHAT HIS THOUGHTS ON THE SIT WERE. HE SAID THAT AT THAT AIRSPD IF THE PROPS WERE CRUISED UP (96% RPM -- WHICH THEY WERE) AND THE PWR LEVERS WERE BROUGHT BACK VERY QUICKLY, THEN THE PROP GOVERNOR COULD POSSIBLY SENSE A CONFLICT BY RESCHEDULING THE FUEL CTL UNIT (WHICH OCCURS ABOUT 97.5% RPM) BTWN THE PROP GOVERNOR AND THE UNDERSPD GOVERNOR, THEREBY CAUSING SOME ERRATIC PITCH CHANGES IN THE PROP WHICH COULD SIMULATE REVERSE MODE. THIS SCENARIO SEEMED THE MORE LIKELY SCENARIO BECAUSE OF THE REASONS STATED EARLIER. HOWEVER, I HAVE PLAYED THE EVENTS OVER AND OVER IN MY MIND AND I CANNOT DETERMINE DEFINITIVELY WHETHER OR NOT I TOUCHED THE LOCKS OR WHETHER OR NOT THE PWR LEVERS WERE BROUGHT INTO GND IDLE.
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.