Citation II S2/Bravo (C550)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 34.6; Flight Crew Total 15846; Flight Crew Type 565.7
Situational Awareness; Training / Qualification
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft; Human Factors
I was Pilot In Command (PIC) on a CE550 and weather was 2;500 overcast 2 miles with light snow. After about 3 minutes into the flight the left engine oil light illuminated with the oil pressure showing 40 psi. We returned to the airport by being vectored for the ILS; landing uneventfully 8 minutes after the light illuminated. I didn't shut down the engine feeling that it was safer to land with it operating at reduced power. Opening the oil access door; I noticed the loss of oil was from the dipstick not being fully locked in place. I had preflighted the aircraft a few days before the scheduled flight; and recall the oil level in both engines was in the normal range. I can't believe that I would not have secured the dipstick into its proper place. It is so routine. My inactions of not checking the oil dipsticks to make sure they were secure was the reason for this incident.My judgment was further clouded because after new oil was put into the engine I completed the two day trip. I wrongly perceived that having some oil pressure after landing I could still go on the trip. I regret not having a discussion with my supervisor and the other pilot about doing so. While taking full responsibility for my actions; the 'get the job done' attitude may have overshadowed my judgment. If any of us had raised some doubt; I don't believe we would have departed. I have implemented a new procedure that after the oil is checked by one pilot; the other pilot will check to make sure everything is secure.
A CE550 Captain reported a low oil pressure indication on the left engine shortly after takeoff and returned to the departure airport. Post flight revealed that the dipstick was not locked in place; causing the oil loss and the reporter was likely the last person to touch it. The oil is then replaced and the flight departs on a two day trip without any additional maintenance.