Narrative:

After getting a chip light on my #2 engine maintenance was performed and I was running this engine with the cowling back and the rotor brake on for a leak check. I then shut down the engine and waited at the controls for the mechanic to secure the cowling. He said everything was buttoned up, so I restarted the #2 engine for a 30 min ground run, and completed this with no problem. I then shut down and went inside to report that there was no problem and see if the aircraft was now airworthy. The mechanic said yes, so I decided to fly it locally for 10 mins to be sure I wouldn't get another chip light before a commercial flight. After takeoff and about 5 mins into the flight, my #1 engine N2 quit working. I called our radio man and told him to inform maintenance. As I was returning to the airport I then got a baggage smoke warning light. I landed immediately, shut down the engines and ran back to the baggage compartment. It was full of smoke but no fire. Smoke was coming out of the right hand engine compartment, but still no fire, so I walked around to the left hand side to undo the cowling latches. The left hand cowling latches were not latched and the slipstream had forced the cowling out and aft. This resulted in a misalignment of the engine exhaust and the cowling exhaust port. Because of this part of the exhaust was being deflected back inside on the engines. This exhaust melted many wires and burned paint on the cowling which resulted in the smoke. I failed, as a pilot, in not rechking both sides of the engine cowling, as my side was latched. At the time, it seemed inconceivable that a mechanic would only latch half of the cowling and then tell me it was completely latched.

Related reports:

Google
 

Original NASA ASRS Text

Title: EMERGENCY LNDG BY HELICOPTER DUE TO SMOKE WARNING.

Narrative: AFTER GETTING A CHIP LIGHT ON MY #2 ENG MAINT WAS PERFORMED AND I WAS RUNNING THIS ENG WITH THE COWLING BACK AND THE ROTOR BRAKE ON FOR A LEAK CHK. I THEN SHUT DOWN THE ENG AND WAITED AT THE CONTROLS FOR THE MECH TO SECURE THE COWLING. HE SAID EVERYTHING WAS BUTTONED UP, SO I RESTARTED THE #2 ENG FOR A 30 MIN GND RUN, AND COMPLETED THIS WITH NO PROB. I THEN SHUT DOWN AND WENT INSIDE TO RPT THAT THERE WAS NO PROB AND SEE IF THE ACFT WAS NOW AIRWORTHY. THE MECH SAID YES, SO I DECIDED TO FLY IT LOCALLY FOR 10 MINS TO BE SURE I WOULDN'T GET ANOTHER CHIP LIGHT BEFORE A COMMERCIAL FLT. AFTER TKOF AND ABOUT 5 MINS INTO THE FLT, MY #1 ENG N2 QUIT WORKING. I CALLED OUR RADIO MAN AND TOLD HIM TO INFORM MAINT. AS I WAS RETURNING TO THE ARPT I THEN GOT A BAGGAGE SMOKE WARNING LIGHT. I LANDED IMMEDIATELY, SHUT DOWN THE ENGS AND RAN BACK TO THE BAGGAGE COMPARTMENT. IT WAS FULL OF SMOKE BUT NO FIRE. SMOKE WAS COMING OUT OF THE RIGHT HAND ENG COMPARTMENT, BUT STILL NO FIRE, SO I WALKED AROUND TO THE LEFT HAND SIDE TO UNDO THE COWLING LATCHES. THE LEFT HAND COWLING LATCHES WERE NOT LATCHED AND THE SLIPSTREAM HAD FORCED THE COWLING OUT AND AFT. THIS RESULTED IN A MISALIGNMENT OF THE ENG EXHAUST AND THE COWLING EXHAUST PORT. BECAUSE OF THIS PART OF THE EXHAUST WAS BEING DEFLECTED BACK INSIDE ON THE ENGS. THIS EXHAUST MELTED MANY WIRES AND BURNED PAINT ON THE COWLING WHICH RESULTED IN THE SMOKE. I FAILED, AS A PLT, IN NOT RECHKING BOTH SIDES OF THE ENG COWLING, AS MY SIDE WAS LATCHED. AT THE TIME, IT SEEMED INCONCEIVABLE THAT A MECH WOULD ONLY LATCH HALF OF THE COWLING AND THEN TELL ME IT WAS COMPLETELY LATCHED.

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.