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Constant torque on takeoff system malfunctioned allowing engine to overtemp and overspeed resulting in engine damage and change.
| Attributes | |
| ACN | 88272 |
| Time | |
| Date | 198805 |
| Day | Mon |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : mci |
| State Reference | MO |
| Altitude | agl bound lower : 0 agl bound upper : 0 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Light Transport, Low Wing, 2 Turboprop Eng |
| Flight Phase | climbout : takeoff |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : cfi |
| Experience | flight time last 90 days : 200 flight time total : 7400 flight time type : 1000 |
| ASRS Report | 88272 |
| Person 2 | |
| Function | other personnel other |
| Qualification | other other : other |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem other |
| Consequence | other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
On the first takeoff from wichita the ctot switches (constant torque on takeoff) were armed to fire to produce the desired and selected 95%. The left engine accelerated to 112% and engine temperature went to approximately 947 degrees C digital readout. Maximum transitional temperature allowed is 960 degrees C and 118% torque for 12 seconds. Since my first officer was flying I turned the switches (ctot) off and power became more normal. Since this is not an unusual occurrence (I and my fellow pilots have seen torque overshoots before with subsequent takeoffs totally normal), I made a mental note of it. On the second takeoff where I was flying, we selected target torque (according to power charts) and 102% was dialed on ctot panel. Power was brought up slowly checking all engine parameters which were normal. At approximately 60-70 KTS, I called for switches on and after the usual one to one and a half second lag the ctot system fired. All seemed normal in power acceleration. I had to divide my attention to the runway, airspeed and power quadrant. We had a strong headwind so V1 call came fairly quickly. When I brought my eyes back to the temperature and torque gauges, both were accelerating past the 102% already selected. I am in reference to the left engine only. By the time I called for switches off the torque, had gone to 115+% and temperature had hit 975 degrees C digital. Both were there for 2 seconds or less. This was the first time I had witnessed an overshoot this bad and on successive takeoffs. Usually the second takeoffs were normal. A squawk written in 5/88 stated that the left engine had been starting hot. Several days of hot starts will damage an engine more than a 2 second overtemp. I wrote up my own squawk quoting the torques and temperatures listed above. An engine breakdown indicated damage to the turbine wheels and blades. I believe this occurred due to malfunctions in some parts of the ctot system. The takeoff was not aborted as we had already reached V1 and after the switches were turned off, all other parameters were normal.
Original NASA ASRS Text
Title: CONSTANT TORQUE ON TKOF SYSTEM MALFUNCTIONED ALLOWING ENGINE TO OVERTEMP AND OVERSPEED RESULTING IN ENGINE DAMAGE AND CHANGE.
Narrative: ON THE FIRST TKOF FROM WICHITA THE CTOT SWITCHES (CONSTANT TORQUE ON TKOF) WERE ARMED TO FIRE TO PRODUCE THE DESIRED AND SELECTED 95%. THE LEFT ENG ACCELERATED TO 112% AND ENG TEMP WENT TO APPROX 947 DEGS C DIGITAL READOUT. MAX TRANSITIONAL TEMP ALLOWED IS 960 DEGS C AND 118% TORQUE FOR 12 SECS. SINCE MY F/O WAS FLYING I TURNED THE SWITCHES (CTOT) OFF AND PWR BECAME MORE NORMAL. SINCE THIS IS NOT AN UNUSUAL OCCURRENCE (I AND MY FELLOW PLTS HAVE SEEN TORQUE OVERSHOOTS BEFORE WITH SUBSEQUENT TKOFS TOTALLY NORMAL), I MADE A MENTAL NOTE OF IT. ON THE SECOND TKOF WHERE I WAS FLYING, WE SELECTED TARGET TORQUE (ACCORDING TO PWR CHARTS) AND 102% WAS DIALED ON CTOT PANEL. PWR WAS BROUGHT UP SLOWLY CHKING ALL ENG PARAMETERS WHICH WERE NORMAL. AT APPROX 60-70 KTS, I CALLED FOR SWITCHES ON AND AFTER THE USUAL ONE TO ONE AND A HALF SECOND LAG THE CTOT SYS FIRED. ALL SEEMED NORMAL IN PWR ACCELERATION. I HAD TO DIVIDE MY ATTN TO THE RWY, AIRSPD AND PWR QUADRANT. WE HAD A STRONG HEADWIND SO V1 CALL CAME FAIRLY QUICKLY. WHEN I BROUGHT MY EYES BACK TO THE TEMP AND TORQUE GAUGES, BOTH WERE ACCELERATING PAST THE 102% ALREADY SELECTED. I AM IN REF TO THE LEFT ENG ONLY. BY THE TIME I CALLED FOR SWITCHES OFF THE TORQUE, HAD GONE TO 115+% AND TEMP HAD HIT 975 DEGS C DIGITAL. BOTH WERE THERE FOR 2 SECS OR LESS. THIS WAS THE FIRST TIME I HAD WITNESSED AN OVERSHOOT THIS BAD AND ON SUCCESSIVE TKOFS. USUALLY THE SECOND TKOFS WERE NORMAL. A SQUAWK WRITTEN IN 5/88 STATED THAT THE LEFT ENG HAD BEEN STARTING HOT. SEVERAL DAYS OF HOT STARTS WILL DAMAGE AN ENG MORE THAN A 2 SEC OVERTEMP. I WROTE UP MY OWN SQUAWK QUOTING THE TORQUES AND TEMPS LISTED ABOVE. AN ENG BREAKDOWN INDICATED DAMAGE TO THE TURBINE WHEELS AND BLADES. I BELIEVE THIS OCCURRED DUE TO MALFUNCTIONS IN SOME PARTS OF THE CTOT SYS. THE TKOF WAS NOT ABORTED AS WE HAD ALREADY REACHED V1 AND AFTER THE SWITCHES WERE TURNED OFF, ALL OTHER PARAMETERS WERE NORMAL.
Data retrieved from NASA's ASRS site as of August 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.