Narrative:

Enroute; we noticed 'a' system hydraulic quantity trending lower. We initially attributed it to a non-emergency issue we had during gear retraction when the nose gear failed to remain locked up in the retracted position. The QRH procedure remedied that situation; but required continuous pressure on the landing gear up system. Just prior to descent; we began to feel certain that the unusually low quantity was due to a leak instead of increased system demands as the volume continued to decrease. We assessed that we would be able to approach and land at our filed destination without using emergency procedures if our routing and sequencing was close to normal. During the descent; we were instructed to proceed to holding. We both quickly agreed that was not a safe option and stated to approach we would be unable. They asked what our divert was and we stated it and were issued a clearance there; but we also quickly assessed that was also an unsafe alternative and stated we were unable to accept the clearance. The captain requested priority handling for our destination and then declared the emergency when ATC denied the request. System 'a' fluid level was roughly 20-25% below a low normal and continuing to drop. I was timing the loss rate and had noticed an increase in the loss rate over time. We then flew direct to the approach and landed without incident using normal systems. Airfield rescue and fire fighters (arff) at the end of the runway noted no apparent leaks. Our fluid levels had risen from 51% to 68% - still way below normal and we elected to taxi to the ramp with the arff commander trailing us. At the gate; closer examination revealed hydraulic fluid escaping from and pooling in the main wheel wells and a significant leak in the 'a' system.

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Original NASA ASRS Text

Title: A B737-800 crew left the 'A' Hydraulic System pressurized to keep the nose gear in the uplocks during flight; but developed a hydraulic leak which required that an emergency be declared for landing.

Narrative: Enroute; we noticed 'A' system hydraulic quantity trending lower. We initially attributed it to a non-emergency issue we had during gear retraction when the nose gear failed to remain locked up in the retracted position. The QRH procedure remedied that situation; but required continuous pressure on the landing gear up system. Just prior to descent; we began to feel certain that the unusually low quantity was due to a leak instead of increased system demands as the volume continued to decrease. We assessed that we would be able to approach and land at our filed destination without using emergency procedures if our routing and sequencing was close to normal. During the descent; we were instructed to proceed to holding. We both quickly agreed that was not a safe option and stated to Approach we would be unable. They asked what our divert was and we stated it and were issued a clearance there; but we also quickly assessed that was also an unsafe alternative and stated we were unable to accept the clearance. The Captain requested priority handling for our destination and then declared the emergency when ATC denied the request. System 'A' fluid level was roughly 20-25% below a low normal and continuing to drop. I was timing the loss rate and had noticed an increase in the loss rate over time. We then flew direct to the approach and landed without incident using normal systems. Airfield Rescue and Fire Fighters (ARFF) at the end of the runway noted no apparent leaks. Our fluid levels had risen from 51% to 68% - still way below normal and we elected to taxi to the ramp with the ARFF Commander trailing us. At the gate; closer examination revealed hydraulic fluid escaping from and pooling in the main wheel wells and a significant leak in the 'A' system.

Data retrieved from NASA's ASRS site as of July 2013 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.