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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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A bell 412 EMS pilot does not note the throttle creep reduction on #2 engine during a hover taxi procedure at his departure airport. He did not interpretation the low rotor warning as a possible 1 engine speed reduction and increases rotor beep (fuel control on cyclic) for both engines. The #1 engine suffers an overtemp and overspd. The pilot interps these signs as start, not flight, limits and continues flight. Corporation later grounds him for 4 days for incident.
| Attributes | |
| ACN | 410610 |
| Time | |
| Date | 199808 |
| Day | Mon |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : zzz |
| State Reference | US |
| Altitude | agl bound lower : 0 agl bound upper : 100 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Operator | other |
| Make Model Name | Bell Helicopter 412 |
| Operating Under FAR Part | other : unknown |
| Navigation In Use | Other |
| Flight Phase | other other |
| Flight Plan | None |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : single pilot |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 20 flight time total : 7500 flight time type : 1500 |
| ASRS Report | 410610 |
| Events | |
| Anomaly | aircraft equipment problem : critical non adherence : published procedure |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified |
| Resolutory Action | none taken : anomaly accepted |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation other |
Narrative:
Hover taxiing for departure at ZZZ, low rotor RPM warning horn sounded. I increased rotor beep and noted exceedance light illuminated on the aircraft system/engine monitoring device (PAR). I landed on the helipad and checked the aircraft throttles. Engine #2 had crept below full throttle. I checked the PAR which indicated 3 exceedances for the event. 1) (engine #1) itt 898 degrees C for 5.8 seconds. 2) (engine #1) itt 898 degrees C for 7.1 seconds. 3) (engine #1) N1 103.9% for 1.4 seconds. I misread the results, thinking about engine start limitations (not above 960 degrees for 2 seconds) and taking the N1 as torque. I joined the throttles and proceeded with the flight. I rechked the PAR upon return and conferred with maintenance, realizing the exceedances. I have been counseled, received training on the PAR, flight and start limitations, and was suspended from flight duties for 4 days. All flight personnel will receive the same training. I misread the indications the PAR displayed. I failed to consider the itt readings as one engine inoperative (oei) operations. I failed to read the N1 exceedance as such, thinking it was a momentary over tq, which this recording device commonly shows. The flight manual cautions pilots (in the normal operations section) to ensure both throttles are adequately frictioned. I believe this is what caused the drop in #2 engine power, throttle creep. The only interior cockpit monitoring I managed as I put the helicopter on the ground was to see the red PAR warning light and to glimpse the #1 engine itt in the oei range. Without the PAR, that and the low rotor warning, would have been the only indications. I reviewed the indications and did not correctly identify them, then proceeded with my mission. In the future, any exceedance will be much more carefully interpreted. I will consider the red PAR caution light a prompt for maintenance interpretation and possible intervention. This is the procedure all our pilots will use. These exceedances will require a hot end inspection of the ptg which I over temped/over sped.
Original NASA ASRS Text
Title: A BELL 412 EMS PLT DOES NOT NOTE THE THROTTLE CREEP REDUCTION ON #2 ENG DURING A HOVER TAXI PROC AT HIS DEP ARPT. HE DID NOT INTERP THE LOW ROTOR WARNING AS A POSSIBLE 1 ENG SPD REDUCTION AND INCREASES ROTOR BEEP (FUEL CTL ON CYCLIC) FOR BOTH ENGS. THE #1 ENG SUFFERS AN OVERTEMP AND OVERSPD. THE PLT INTERPS THESE SIGNS AS START, NOT FLT, LIMITS AND CONTINUES FLT. CORPORATION LATER GNDS HIM FOR 4 DAYS FOR INCIDENT.
Narrative: HOVER TAXIING FOR DEP AT ZZZ, LOW ROTOR RPM WARNING HORN SOUNDED. I INCREASED ROTOR BEEP AND NOTED EXCEEDANCE LIGHT ILLUMINATED ON THE ACFT SYS/ENG MONITORING DEVICE (PAR). I LANDED ON THE HELIPAD AND CHKED THE ACFT THROTTLES. ENG #2 HAD CREPT BELOW FULL THROTTLE. I CHKED THE PAR WHICH INDICATED 3 EXCEEDANCES FOR THE EVENT. 1) (ENG #1) ITT 898 DEGS C FOR 5.8 SECONDS. 2) (ENG #1) ITT 898 DEGS C FOR 7.1 SECONDS. 3) (ENG #1) N1 103.9% FOR 1.4 SECONDS. I MISREAD THE RESULTS, THINKING ABOUT ENG START LIMITATIONS (NOT ABOVE 960 DEGS FOR 2 SECONDS) AND TAKING THE N1 AS TORQUE. I JOINED THE THROTTLES AND PROCEEDED WITH THE FLT. I RECHKED THE PAR UPON RETURN AND CONFERRED WITH MAINT, REALIZING THE EXCEEDANCES. I HAVE BEEN COUNSELED, RECEIVED TRAINING ON THE PAR, FLT AND START LIMITATIONS, AND WAS SUSPENDED FROM FLT DUTIES FOR 4 DAYS. ALL FLT PERSONNEL WILL RECEIVE THE SAME TRAINING. I MISREAD THE INDICATIONS THE PAR DISPLAYED. I FAILED TO CONSIDER THE ITT READINGS AS ONE ENG INOP (OEI) OPS. I FAILED TO READ THE N1 EXCEEDANCE AS SUCH, THINKING IT WAS A MOMENTARY OVER TQ, WHICH THIS RECORDING DEVICE COMMONLY SHOWS. THE FLT MANUAL CAUTIONS PLTS (IN THE NORMAL OPS SECTION) TO ENSURE BOTH THROTTLES ARE ADEQUATELY FRICTIONED. I BELIEVE THIS IS WHAT CAUSED THE DROP IN #2 ENG PWR, THROTTLE CREEP. THE ONLY INTERIOR COCKPIT MONITORING I MANAGED AS I PUT THE HELI ON THE GND WAS TO SEE THE RED PAR WARNING LIGHT AND TO GLIMPSE THE #1 ENG ITT IN THE OEI RANGE. WITHOUT THE PAR, THAT AND THE LOW ROTOR WARNING, WOULD HAVE BEEN THE ONLY INDICATIONS. I REVIEWED THE INDICATIONS AND DID NOT CORRECTLY IDENT THEM, THEN PROCEEDED WITH MY MISSION. IN THE FUTURE, ANY EXCEEDANCE WILL BE MUCH MORE CAREFULLY INTERPRETED. I WILL CONSIDER THE RED PAR CAUTION LIGHT A PROMPT FOR MAINT INTERPRETATION AND POSSIBLE INTERVENTION. THIS IS THE PROC ALL OUR PLTS WILL USE. THESE EXCEEDANCES WILL REQUIRE A HOT END INSPECTION OF THE PTG WHICH I OVER TEMPED/OVER SPED.
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.