Narrative:

At FL210; crew noticed propeller deice light and ran checklist per QRH; light re-illuminated and per checklist; crew pushed propellers forward and notified ATC that they were having a problem with their ice protection and requested a lower altitude. The flight crew leveled off at 11;000 ft. At this time; the crew noticed that the left oil pressure was at 77 psi. The oil pressure continued to rise until it was between 77-105 psi. Crew reported problem to company. After oil pressure rose again; the crew began talking about diverting to another airport and shutting the engine down. The crew determined that the oil pressure of 150 psi was too high and would have to shut the engine down. Captain contacted the flight attendants and told them that they would have to shut down an engine and divert to another airport. The captain made a PA to the passengers telling them that they would have to shut down an engine out of precaution and divert to another airport. Crew contacted ATC to notify them that they would have to shut down an engine and declare an emergency and divert. Crew ran engine/failure/fire shutdown inflight checklist. Captain took control of the aircraft prior to engine shutdown. First officer began to gather weather information. It was determined by the crew to go to ZZZ1 because there was moderate to severe turbulence reports in ZZZ2. At this time; there were no thunderstorm reports in ZZZ1. Upon gathering more weather information about ZZZ1; it was determined that it would not be a safe place to land and with the help from an ACARS message from dispatch; the crew redirected to ZZZ2. Captain contacted flight attendants and told them what was going on and made a PA to passengers about what was going on and what to expect upon landing in ZZZ2 (trucks; lights; stopping on runway and tow to gate). Captain made landing in ZZZ2 on runway 19; stopped on runway and put the parking brake in park. Contacted the flight attendants to make sure all passengers were ok. Captain told tower that a deplane was not necessary and was towed to the gate. All passengers deplaned at a hard stand unharmed. After landing; crew was notified that there was no oil in the #1 (left) engine. The engine had been shut down for at least 45 minutes. Last noted engine oil pressure was 178 psi in left #1 engine.

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Original NASA ASRS Text

Title: Q400 Flight Crew shut down the left engine and diverted to the nearest suitable airport due to excessive oil pressure indications.

Narrative: At FL210; crew noticed propeller deice light and ran checklist per QRH; light re-illuminated and per checklist; crew pushed propellers forward and notified ATC that they were having a problem with their ice protection and requested a lower altitude. The flight crew leveled off at 11;000 FT. At this time; the crew noticed that the left oil pressure was at 77 PSI. The oil pressure continued to rise until it was between 77-105 PSI. Crew reported problem to company. After oil pressure rose again; the crew began talking about diverting to another airport and shutting the engine down. The crew determined that the oil pressure of 150 PSI was too high and would have to shut the engine down. Captain contacted the Flight Attendants and told them that they would have to shut down an engine and divert to another airport. The Captain made a PA to the passengers telling them that they would have to shut down an engine out of precaution and divert to another airport. Crew contacted ATC to notify them that they would have to shut down an engine and declare an emergency and divert. Crew ran Engine/Failure/Fire Shutdown Inflight checklist. Captain took control of the aircraft prior to engine shutdown. First officer began to gather weather information. It was determined by the crew to go to ZZZ1 because there was moderate to severe turbulence reports in ZZZ2. At this time; there were no thunderstorm reports in ZZZ1. Upon gathering more weather information about ZZZ1; it was determined that it would not be a safe place to land and with the help from an ACARS message from Dispatch; the crew redirected to ZZZ2. Captain contacted Flight Attendants and told them what was going on and made a PA to passengers about what was going on and what to expect upon landing in ZZZ2 (trucks; lights; stopping on runway and tow to gate). Captain made landing in ZZZ2 on Runway 19; stopped on runway and put the parking brake in park. Contacted the Flight Attendants to make sure all passengers were OK. Captain told Tower that a deplane was not necessary and was towed to the gate. All passengers deplaned at a hard stand unharmed. After landing; crew was notified that there was no oil in the #1 (left) engine. The engine had been shut down for at least 45 minutes. Last noted engine oil pressure was 178 PSI in left #1 engine.

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.