<< >> NASA ASRS Report 173317, March 1991

Torque gauge failure on commuter light transport causes flight crew to return land after takeoff from sea.

Attributes
ACN	173317
Time
Date	199103
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : sea
State Reference	WA
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : sea artcc : zjx
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 12000 flight time type : 3000
ASRS Report	173317
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : declared emergency
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

On climb out from sea, left torque gauge failed. Returned to sea and landed uneventfully. Problem with this situation is that torque gauge fails to the high indication when power is removed. This causes torque and temperature limiting system to sense an over torque situation and dump fuel, causing the engine to surge and other indications (i.e., temperature) to fluctuate, which could indicate other problems. Remedy is to turn ttl system off to eliminate the problem. If this were to happen at low speed, such as at or after rotation, a simple gauge failure could cause multiple problems in control and performance when no real power problem exists. It seems that designing a system to operate in this way is in error. A simple gauge failure can be compounded by another system, causing possibly major problems. At the other extreme, in a low power situation a torque gauge failure could lead to a flame-out of the affected engine, as the fuel being bypassed by the ttl system to limit the torque could be too little for the engine to continue running.

Related reports:

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• Light transport commuter hydraulic system failure as landing...

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Original NASA ASRS Text

Title: TORQUE GAUGE FAILURE ON COMMUTER LTT CAUSES FLT CREW TO RETURN LAND AFTER TKOF FROM SEA.

Narrative: ON CLBOUT FROM SEA, LEFT TORQUE GAUGE FAILED. RETURNED TO SEA AND LANDED UNEVENTFULLY. PROB WITH THIS SITUATION IS THAT TORQUE GAUGE FAILS TO THE HIGH INDICATION WHEN PWR IS REMOVED. THIS CAUSES TORQUE AND TEMP LIMITING SYS TO SENSE AN OVER TORQUE SITUATION AND DUMP FUEL, CAUSING THE ENG TO SURGE AND OTHER INDICATIONS (I.E., TEMP) TO FLUCTUATE, WHICH COULD INDICATE OTHER PROBS. REMEDY IS TO TURN TTL SYS OFF TO ELIMINATE THE PROB. IF THIS WERE TO HAPPEN AT LOW SPD, SUCH AS AT OR AFTER ROTATION, A SIMPLE GAUGE FAILURE COULD CAUSE MULTIPLE PROBS IN CTL AND PERFORMANCE WHEN NO REAL PWR PROB EXISTS. IT SEEMS THAT DESIGNING A SYS TO OPERATE IN THIS WAY IS IN ERROR. A SIMPLE GAUGE FAILURE CAN BE COMPOUNDED BY ANOTHER SYS, CAUSING POSSIBLY MAJOR PROBS. AT THE OTHER EXTREME, IN A LOW PWR SITUATION A TORQUE GAUGE FAILURE COULD LEAD TO A FLAME-OUT OF THE AFFECTED ENG, AS THE FUEL BEING BYPASSED BY THE TTL SYS TO LIMIT THE TORQUE COULD BE TOO LITTLE FOR THE ENG TO CONTINUE RUNNING.

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.