IAI1124/1124A Westwind
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument
Flight Crew Last 90 Days 60; Flight Crew Type 2500
Aircraft Equipment Problem Critical
Flight Crew Inflight Shutdown; Flight Crew Landed As Precaution; Flight Crew Diverted; General Maintenance Action
Aircraft
[We] shut down an engine in flight due to loss of oil pressure indication in the right (starboard) side engine. Upon landing; the engine cowl on the effected engine was removed by a local field mechanic for inspection and it appeared the oil cap had not been secured properly causing a loss of engine oil and subsequently oil pressure. During the flight; my co-captain and I both discussed the matter and collectively decided an engine shut down was the prudent thing to do. We had two indications; both a low oil pressure indication and soon after an oil pressure light. As a safety precaution after finding acceptable weather along our immediate route; we agreed to and diverted into [a nearby alternate] on the one operating engine. Weather was acceptable for the ILS approach and we executed an uneventful ILS approach to a landing. We both noticed that even though we had hoped to salvage the engine with an inflight shutdown; the engine continued to rotate at approximately 30% rpm due to the aerodynamic loads on the engine at the velocity we traveled. This continual rotation caused the engine to seize near the downwind portion of our pattern for conducting the ILS approach. This low freewheeling rpm most likely kept the engine from a possible catastrophic de-containment. Immediately after the landing; we made sure our first priority was to the safety and security of our passengers who were put on another flight to their ultimate destination. We did not declare an emergency because we did not see the event as an actual in-flight emergency. ATC treated the event as an inflight emergency and provided us with priority handling. We had fire trucks standing by and fortunately; none of the local airport emergency services were needed.
Westwind Captain diverted to a nearby alternate after an inflight shutdown of the right engine. This was due to a loss of oil pressure later traced to failure to replace the oil cap.