Narrative:

Operating short 30 minute flight; picked up the plane from hanger after finishing first flight of the day checks we did a single engine turn to the gate and picked up our passengers and proceeded towards the runway. It was first officer's turn to fly. During the take-off roll sometime right about 80 kts we heard an unusual sound from the left side of the aircraft. I took a quick glance on the left engine and then scanned all the engine instruments and annunciators; I found nothing; so continued. At about 100 ft above the ground observed the left torque gauge receding slowly to 3000 lbs. I immediately pushed the left throttle and synchronized it with the right side roughly setting it at 3500 lbs and tightened the friction locks. No more torque adjustments were made till acceleration altitude. Reaching 400 ft above the ground climb power was set as I pulled the propeller levers to 1550 RPM. As soon I finished my flows I was asked by tower to switch to departure frequency. Before I could flip the frequency switch; my mind got diverted with unsynchronized propeller sound. I looked over the propeller gauge and found the left prop had crept up to about 1700 RPM while the right side still sat at 1550 RPM. I also found the left propeller lever at full forward position. Meanwhile tower came back again inquiring if we had switched I acknowledged and said 'we are switching'. After checking in with departure we were instructed to climb up to 4000 ft. I pulled back the left propeller lever to sync with the right side and tightened the friction lock but this time I observed the uncommanded movement of the left propeller lever sliding forward; again showing about 1700 RPM on the left gauge only. Also since we were in the plane with an MEL the plane would not pressurize making a loud air rushing sound in our headsets. So between the loud air noise and the unsynchronized prop sound we were unable to hear any other relative engine sounds. So to get rid of one noise I pushed the right propeller lever forward so it could sync with the left side. After passing 1500 ft I called dispatch/maintenance control and informed them of the situation. Hoping to evaluate the situation and get a better understanding of the problem; I also mentioned how the left propeller lever kept on going forward even after the friction lock was tightened. Meanwhile we got instructions from departure to expedite the climb due to traffic up to 5000ft which was our cruising altitude. Dispatch/maintenance control came back on the radio and asked about the engine parameters which I replied as normal. I queried them saying could it be failure of prop governor. But realized after speaking that prop rpm in that case would have gone to 1802 instead of 1700. Dispatch/maintenance control asked if the aircraft was under control again to which I replied positively saying 'yes' as I both the propeller set to >1700 RPM. Still at that point I did not observe any limitations exceeding every engine instrument looked normal. Eventually we had reached cruise altitude and after setting cruise power about 2500 lbs I decided to pull back the propeller levers back to 1550 RPM and this time to my surprise the left propeller stayed at 1550 RPM. I called dispatch/maintenance control and told them that everything was normal again left prop was not moving uncommanded like before and we could proceed to our destination. But in reply we were given an amendment and asked to return back to our departure airport by dispatch/maintenance control. The first officer called center and asked for vectors back. Control at that time asked if this was an emergency issue and needed any assistance to which we replied saying 'negative emergency'. We were asked to turn towards a westerly heading which we initiated a turn. Probably around that time we got a call again from dispatch/maintenance control and this time we were asked to proceed to our original destination. So we asked center again with a request to continue toour destination. At that time the aircraft was responding well to the commands and every engine indication was in green and normal. We began our descent to land with all the normal indications and a normal landing was executed. It is not until we touched the ground I heard another peculiar noise from the left engine and it felt like churning noise probably like a metal grinding sound. I decided to bring the aircraft quickly out of reverse/ground fine mode and cleared the runway as soon as possible. After clearing I shut down both the engines and asked first officer to inspect the left engine when he gets out. During deplaning one last passenger inquired about the weird noise and churning sound and said she was scared a little. I told her we are aware of it and soon would be inspecting it. She thanked us and deplaned. After all the passengers were inside the terminal my first officer bought to my attention one hole on the left outboard exhaust stack. After closely inspecting it I found that blast tubes had broken loose from both outboard and inboard exhaust stack leaving big holes at the bottom where they are supposed to be connected. I also then tried to hand spin the prop to see if it was free but it would not rotate. After I completed inspection thoroughly of the entire aircraft I notified maintenance control of the entire situation. The aircraft was grounded there and a log entry was made in the book.

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Original NASA ASRS Text

Title: A B1900 Crew reported propeller creep during takeoff and climb. After inflight trouble shooting the aircraft systems appeared normal so the flight continued. After landing the crew found the exhaust stacks disconnected and the propeller would not turn.

Narrative: Operating short 30 minute flight; picked up the plane from hanger after finishing first flight of the day checks we did a Single Engine turn to the gate and picked up our passengers and proceeded towards the runway. It was First Officer's turn to fly. During the take-off roll sometime right about 80 kts we heard an unusual sound from the left side of the aircraft. I took a quick glance on the left engine and then scanned all the engine instruments and annunciators; I found nothing; so continued. At about 100 ft above the ground observed the left torque gauge receding slowly to 3000 lbs. I immediately pushed the left throttle and synchronized it with the right side roughly setting it at 3500 lbs and tightened the friction locks. No more torque adjustments were made till acceleration altitude. Reaching 400 ft above the ground climb power was set as I pulled the propeller levers to 1550 RPM. As soon I finished my flows I was asked by Tower to switch to Departure frequency. Before I could flip the frequency switch; my mind got diverted with unsynchronized propeller sound. I looked over the propeller gauge and found the left prop had crept up to about 1700 RPM while the right side still sat at 1550 RPM. I also found the left propeller lever at full forward position. Meanwhile Tower came back again inquiring if we had switched I acknowledged and said 'We are switching'. After checking in with Departure we were instructed to climb up to 4000 ft. I pulled back the left propeller lever to sync with the right side and tightened the friction lock but this time I observed the uncommanded movement of the left propeller lever sliding forward; again showing about 1700 RPM on the left gauge only. Also since we were in the plane with an MEL the plane would not pressurize making a loud air rushing sound in our headsets. So between the loud air noise and the unsynchronized prop sound we were unable to hear any other relative engine sounds. So to get rid of one noise I pushed the right propeller lever forward so it could sync with the left side. After passing 1500 ft I called Dispatch/Maintenance Control and informed them of the situation. Hoping to evaluate the situation and get a better understanding of the problem; I also mentioned how the left propeller lever kept on going forward even after the friction lock was tightened. Meanwhile we got instructions from Departure to expedite the climb due to traffic up to 5000ft which was our cruising altitude. Dispatch/Maintenance Control came back on the radio and asked about the engine parameters which I replied as normal. I queried them saying could it be failure of prop governor. But realized after speaking that prop rpm in that case would have gone to 1802 instead of 1700. Dispatch/Maintenance Control asked if the aircraft was under control again to which I replied positively saying 'Yes' as I both the propeller set to >1700 RPM. Still at that point I did not observe any limitations exceeding every engine instrument looked normal. Eventually we had reached cruise altitude and after setting cruise power about 2500 lbs I decided to pull back the propeller levers back to 1550 RPM and this time to my surprise the left propeller stayed at 1550 RPM. I called Dispatch/Maintenance Control and told them that everything was normal again left prop was not moving uncommanded like before and we could proceed to our destination. But in reply we were given an amendment and asked to return back to our departure airport by Dispatch/Maintenance Control. The First Officer called Center and asked for vectors back. Control at that time asked if this was an emergency issue and needed any assistance to which we replied saying 'Negative Emergency'. We were asked to turn towards a westerly heading which we initiated a turn. Probably around that time we got a call again from Dispatch/Maintenance Control and this time we were asked to proceed to our original destination. So we asked Center again with a request to continue toour destination. At that time the aircraft was responding well to the commands and every engine indication was in green and normal. We began our descent to land with all the normal indications and a normal landing was executed. It is not until we touched the ground I heard another peculiar noise from the left engine and it felt like churning noise probably like a metal grinding sound. I decided to bring the aircraft quickly out of reverse/ground fine mode and cleared the runway as soon as possible. After clearing I shut down both the engines and asked First Officer to inspect the left engine when he gets out. During deplaning one last passenger inquired about the weird noise and churning sound and said she was scared a little. I told her we are aware of it and soon would be inspecting it. She thanked us and deplaned. After all the passengers were inside the terminal my First Officer bought to my attention one hole on the left outboard exhaust stack. After closely inspecting it I found that blast tubes had broken loose from both outboard and inboard exhaust stack leaving big holes at the bottom where they are supposed to be connected. I also then tried to hand spin the prop to see if it was free but it would not rotate. After I completed inspection thoroughly of the entire aircraft I notified Maintenance Control of the entire situation. The aircraft was grounded there and a log entry was made in the book.

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.