ATR 72
Flight Crew Air Transport Pilot (ATP)
Troubleshooting; Human-Machine Interface
Aircraft Equipment Problem Critical; Inflight Event / Encounter Weather / Turbulence
Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition; Flight Crew Inflight Shutdown; Flight Crew Executed Go Around / Missed Approach; Flight Crew Diverted; General Declared Emergency
Aircraft; Procedure; Staffing
We requested an immediate turn to the north after takeoff to maintain a safe distance from some thunderstorms. When climbing through 8;000 FT we looked down to verify torque and noticed the Number 1 indicator was at 120%.  We reduced throttle and the indication remained at 120%. We completed the Abnormal Engine Parameters Checklist which resulted in no correction to the torque indication; shut down the engine and then completed Single Engine Operations Checklist. We discussed possible diversions and decided returning was not the best option due to convective activity; and that ZZZ was the best closest option. We notified ATC of the engine trouble; declared an emergency; and requested current weather at ZZZ. They reported clear skies and winds at 10 KTS and good visibility; so we requested a diversion to ZZZ. The airplane would only maintain 8;000 FT. Enroute we notified the company that we were diverting and prepared for the approach. As we began the approach; winds increased significantly to 30 KTS with an unfavorable crosswind coming from the right side; which made directional control even more difficult as we were having to correct for asymmetrical thrust from the right engine. On final approach we could not maintain runway centerline and decided to go-around. The airplane had very poor performance on the go-around even with proper go-around torque set. We continued straight out to maximize climb performance and then discussed our options. We requested area airports weather and asked for a recommendation on which would be a better alternative; chose one with more favorable winds and decided to divert there. Enroute we asked for updates at our departure airport and learned the winds were strong; but right down the runway with no windshear reported for over an hour. There was no precipitation or convection reported in between our location and the airport; so we decided to return and land there. Winds were strong; but very closely aligned to the runway. The approach was stable and landing stable.I think an enhanced description of abnormal engine parameters would be helpful in the checklist. In our situation NP; ITT; and Nh were all normal which suggested just a bad torque indication; but the checklist stated that regardless the engine should be shut down. This is a scenario where judgment comes heavily into play and in evaluating whether we chose correctly would be heavily influenced by the outcome. If we decided to keep engine running and something else happened such as a fire or uncontained engine failure we would be asked why we didn't shut it down versus being asked why we shut down an engine that was responding to throttle movement with all other normal indications other than torque. Obviously checklists cannot cover every scenario.
We had climbed to about 9;000 MSL; but the airplane couldn't maintain altitude so we requested 8;000 and declared an emergency with Center. We got very poor climb performance on the single engine and barely climbed to 6;000 FT. The autopilot began to capture 6;000 FT at nearly 200 FT prior and pitched up abruptly to capture the altitude bringing our speed very low for our configuration very quickly even though it was in IAS mode.
When the flight crew of an ATR-72 was unable to get response from the right engine torque gauge during their enroute climb they felt compelled to shut the engine down per the checklist.  Weather at their departure airport and first selected alternate initially precluded a safe landing although; eventually; thunderstorms at their departure airport abated and they returned safely.