Narrative:

While flying on a planned cross country flight; with a student; with unlimited visibility and no clouds; at dusk; our airplane's left engine slowly began to lose power. Initially; the engine lost only a few percent load; and we thought we might have bumped the throttle with an errant knee. So we began to monitor the engine closely. No abnormal temperatures or pressures were noticed; so we kept flying; assuming the very slight loss in power to be inconsequential. A few minutes later; the engine began to surge up and down; in increasing amounts. So; per our preflight brief; the student went through the checklist to shut down the engine; and I got the checklist out to verify it was complete. After feathering the engine; the student got on the radio and notified ATC that we had lost an engine. However; he did indicate that he was not declaring an emergency. We then turned for home. A few minutes passed on the single engine while we tried to troubleshoot; and the decision was made to restart the engine. We did so; with the checklist; and the engine restarted easily. It then worked well for 5 minutes or so before it began; again; to act up. So we shut the engine down again; and returned to our home airport. The flight ended without incident; and it was diagnosed the next day as a mechanical default; and was serviced. The problem with our actions; and the reason for this report; is that I made poor judgements; and performed incorrectly; in several ways. First; I should have declared an emergency. We had effectively lost an engine; and were in an emergency situation. Consideration should have been taken because we were first; reading from the emergency checklist and second; that we were in a situation that demanded our emergency declaration. Second; we should have landed as soon as possible instead of returning to our home airport. From where the engine failure occurred; we were 40 minutes from our home base; and only 10 minutes from a suitable alternate. Upon reflection; because the situation demanded it; the correct choice was to divert immediately to the closer airport; instead of continuing flight on a single engine; and returning to our home base as we did.

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Original NASA ASRS Text

Title: Instructor and student pilots aboard a Diamond Twin Star failed to declare an emergency due to an engine failure. They returned to their home airport some 40 minutes away.

Narrative: while flying on a planned cross country flight; with a student; with unlimited visibility and no clouds; at dusk; our airplane's left engine slowly began to lose power. Initially; the engine lost only a few percent load; and we thought we might have bumped the throttle with an errant knee. So we began to monitor the engine closely. No abnormal temperatures or pressures were noticed; so we kept flying; assuming the very slight loss in power to be inconsequential. A few minutes later; the engine began to surge up and down; in increasing amounts. So; per our preflight brief; the student went through the checklist to shut down the engine; and I got the checklist out to verify it was complete. After feathering the engine; the student got on the radio and notified ATC that we had lost an engine. However; he did indicate that he was not declaring an emergency. We then turned for home. A few minutes passed on the single engine while we tried to troubleshoot; and the decision was made to restart the engine. We did so; with the checklist; and the engine restarted easily. It then worked well for 5 minutes or so before it began; again; to act up. So we shut the engine down again; and returned to our home airport. The flight ended without incident; and it was diagnosed the next day as a mechanical default; and was serviced. The problem with our actions; and the reason for this report; is that I made poor judgements; and performed incorrectly; in several ways. First; I should have declared an emergency. We had effectively lost an engine; and were in an emergency situation. Consideration should have been taken because we were first; reading from the emergency checklist and second; that we were in a situation that demanded our emergency declaration. Second; we should have landed as soon as possible instead of returning to our home airport. From where the engine failure occurred; we were 40 minutes from our home base; and only 10 minutes from a suitable alternate. Upon reflection; because the situation demanded it; the correct choice was to divert immediately to the closer airport; instead of continuing flight on a single engine; and returning to our home base as we did.

Data retrieved from NASA's ASRS site as of April 2012 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.