Narrative:

While in cruise flight at FL240 at xa:43 local; we experienced a #1 hydraulic iso-valve caution light. This event was due to the loss of more than 1/2qt hydraulic fluid from the #1 system.identification - #1 hydraulic iso-valve caution light illuminated.response - we confirmed this by looking at the #1 hydraulic-quantity-indicator that read slightly less than 1qt. Remaining. Pilot flying called for the emergency checklist. I ran the #1 hydraulic iso vlv checklist. We discussed all the services that would be lost. At this point we wanted to get up with dispatch and see if they would like us to divert or continue to our destination. We tried frequencies and received no answer. We had to use a commercial radio relay operator. We were asked if we were comfortable flying to our destination? We were and agreed to divert. We were only 18 minutes from our divert airport and about the same time/distance remained to our destination. We discussed it and felt it necessary to declare an emergency. I declared an emergency at xa:55 local with center and requested a turn to our destination. There were 13 souls aboard and 2.5 hours of fuel remaining at that point. We were given direct. I spoke to the flight attendant; told her the nature of the problem; that she had 20 minutes; we would not need to brace. He also made a brief announcement to the passengers with pertinent information. I picked up the ATIS; one challenge was the divert airport was using one runway due to wind 140@10g16. We discussed this; we were concerned with shooting an approach to an airport with surrounding terrain; circling with a compromised aircraft with higher than normal reference speeds to the shorter runway. We decided not to circle; accept a crosswind; and go straight-in. We needed 5300 feet if we had to do a 0 flap landing and the straight-in runway is 6800 feet long. We decided that a longer runway with a slight upslope was the better choice for this situation; even with a crosswind. We also discussed that we would try the flaps; just in case we might get some of them. As we descended on the approach; configured; we found that all the flaps were available; we used 15 degrees due to field conditions. The flaps deployed slower than normal. The #1 hydraulic iso vlv; roll splr inbd hydraulic; and #1 engine hydraulic pump caution lights continuously flickered during flap extension. During the landing checklist I noted that all the caution lights were out. We planned to have no normal brakes; but felt it possible that we might have some normal brakes available; so on touchdown pilot flying applied them and found there was some residual brake pressure before they completely faded. I ran the after landing checks; we feathered the props; with the APU running; and then shut down the engines. Pilot flying spoke to the passengers; told them to remain on board; we decided to be towed to the gate. As it turned out a bus arrived; took our passengers; we were towed to the maintenance hangar. The airport authority asked us questions for their report. PF called dispatch and reported to the shift supervisor. We spoke to the maintenance personnel and reviewed the emergency with them. Some time passed and scheduling called and rescheduled us into an evaluation flight; then a reposition flight if all went well; then a deadhead placing us at 15.2 hours of duty. This created considerable stress for the entire crew. We expressed our concern with this reschedule; first with crew scheduling; dispatch supervisor and eventually onto the chief pilot. Ultimately we reluctantly ended up flying the evaluation flight; which continued the reposition destination with no incident. Towards the end of the evaluation flight PF and I started to feel the initial stages of fatigue set in. Because of this we double checked everything on the decent/approach and landing checklists to make sure we didn't miss anything. We then deadheaded home on a flight for a 15-hour total duty day. We pushed off the gate with minimum dispatch quantity on the #1 system. We both had acknowledged this. Somewhere enroute we lost over 1/2 quart of fluid; which tripped the iso valve. Maintenance found the overspill container to be completely full indicating a likely hydraulic-accessory leaking; however; we don't know if they found this. Had we had more than minimum quantity; perhaps we could have noticed leakage prior to tripping the iso valve and generating this emergency. Perhaps it would be better not to operate at minimum dispatch; which greatly reduced our margin in tripping the iso valve. In this case it took some 45 minutes to drop 1/2 qt. Of fluid; so the loss was slow. Also; fearing possible disciplinary action from the company influenced us to accept a reschedule that we did not completely agree with.

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Original NASA ASRS Text

Title: A DHC-8-300 aircraft lost a significant amount of hydraulic fluid causing the #1 hydraulic ISO-valve caution light to illuminate. An emergency was declared with a diversion to an enroute airport the crew later ferried the aircraft at the end of a very long day.

Narrative: While in cruise flight at FL240 at XA:43 local; we experienced a #1 hydraulic ISO-valve caution light. This event was due to the loss of more than 1/2qt hydraulic fluid from the #1 system.Identification - #1 hydraulic ISO-Valve caution light illuminated.Response - We confirmed this by looking at the #1 Hydraulic-Quantity-Indicator that read slightly less than 1qt. remaining. Pilot flying called for the Emergency checklist. I ran the #1 HYD ISO VLV checklist. We discussed all the services that would be lost. At this point we wanted to get up with dispatch and see if they would like us to divert or continue to our destination. We tried frequencies and received no answer. We had to use a commercial radio relay operator. We were asked if we were comfortable flying to our destination? We were and agreed to divert. We were only 18 minutes from our divert airport and about the same time/distance remained to our destination. We discussed it and felt it necessary to declare an emergency. I declared an emergency at XA:55 local with Center and requested a turn to our destination. There were 13 souls aboard and 2.5 hours of fuel remaining at that point. We were given direct. I spoke to the Flight Attendant; told her the nature of the problem; that she had 20 minutes; we would not need to brace. He also made a brief announcement to the passengers with pertinent information. I picked up the ATIS; one challenge was the divert airport was using one runway due to wind 140@10G16. We discussed this; we were concerned with shooting an approach to an airport with surrounding terrain; circling with a compromised aircraft with higher than normal REF speeds to the shorter runway. We decided not to circle; accept a crosswind; and go straight-in. We needed 5300 feet if we had to do a 0 Flap landing and the straight-in runway is 6800 feet long. We decided that a longer runway with a slight upslope was the better choice for this situation; even with a crosswind. We also discussed that we would try the flaps; just in case we might get some of them. As we descended on the approach; configured; we found that all the flaps were available; we used 15 degrees due to field conditions. The flaps deployed slower than normal. The #1 HYD ISO VLV; ROLL SPLR INBD HYD; and #1 ENG HYD PUMP caution lights continuously flickered during flap extension. During the landing checklist I noted that all the caution lights were out. We planned to have no normal brakes; but felt it possible that we might have some normal brakes available; so on touchdown pilot flying applied them and found there was some residual brake pressure before they completely faded. I ran the after landing checks; we feathered the props; with the APU running; and then shut down the engines. Pilot flying spoke to the passengers; told them to remain on board; we decided to be towed to the gate. As it turned out a bus arrived; took our passengers; we were towed to the maintenance hangar. The Airport Authority asked us questions for their report. PF called dispatch and reported to the shift supervisor. We spoke to the maintenance personnel and reviewed the emergency with them. Some time passed and Scheduling called and rescheduled us into an evaluation flight; then a reposition flight if all went well; then a deadhead placing us at 15.2 hours of duty. This created considerable stress for the entire crew. We expressed our concern with this reschedule; first with Crew Scheduling; Dispatch Supervisor and eventually onto the Chief Pilot. Ultimately we reluctantly ended up flying the evaluation flight; which continued the reposition destination with no incident. Towards the end of the evaluation flight PF and I started to feel the initial stages of fatigue set in. Because of this we double checked everything on the Decent/Approach and Landing checklists to make sure we didn't miss anything. We then deadheaded home on a flight for a 15-hour total duty day. We pushed off the gate with Minimum Dispatch Quantity on the #1 system. We both had acknowledged this. Somewhere enroute we lost over 1/2 quart of fluid; which tripped the ISO Valve. Maintenance found the overspill container to be completely full indicating a likely hydraulic-accessory leaking; however; we don't know if they found this. Had we had more than minimum quantity; perhaps we could have noticed leakage prior to tripping the ISO valve and generating this emergency. Perhaps it would be better not to operate at minimum dispatch; which greatly reduced our margin in tripping the ISO valve. In this case it took some 45 minutes to drop 1/2 qt. of fluid; so the loss was slow. Also; fearing possible disciplinary action from the company influenced us to accept a reschedule that we did not completely agree with.

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.