Narrative:

Upon pushing back from the gate; I noticed that hydraulic system number one was slightly lower than number two so I told the first officer that I was going to transfer some hydraulic fluid from the number 2 system to the number 1 system. Once completed; both systems were at 50% (40% is required). Considering that the fluid was above the minimum level and for fear of being scolded or getting into trouble for returning to the gate; I decided to proceed with the flight. We landed in our filed destination without incident and didn't see any noticeable change in hydraulic fluid levels. I told the captain receiving the aircraft to watch the hydraulic system because there was something strange about it (just a feeling but nothing that I could prove or show). Both systems were at the same levels as they were when we departed but; again; I simply had an odd feeling about them. There are a few ways that I think this safety issue could have been avoided. Firstly; I have called maintenance previously when the hydraulic levels were not balanced and they told me to just balance it. By doing so; any slow leak would not be noticed. Due to the nature of the operation and the need to continuously swap aircraft such small leaks could also go unnoticed. Additionally; I personally believe; and I'm not an engineer; that a 40% minimum level of hydraulic pressure is too low for operation (but again I'm not an engineer and don't have the necessary knowledge to determine what is a safe amount). Also; I believe that by fostering a culture where a pilot could freely express his/her feelings may have made me less apprehensive about calling maintenance about an intuitive feeling even though the numbers were at or above the required levels.

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Original NASA ASRS Text

Title: A Q400 crew detected a hydraulic system quantity below 40% and transfered fluid to equalize both systems at 50% then learned later in the day the aircraft suffered a hydraulic system failure.

Narrative: Upon pushing back from the gate; I noticed that hydraulic system number one was slightly lower than number two so I told the First Officer that I was going to transfer some hydraulic fluid from the number 2 system to the number 1 system. Once completed; both systems were at 50% (40% is required). Considering that the fluid was above the minimum level and for fear of being scolded or getting into trouble for returning to the gate; I decided to proceed with the flight. We landed in our filed destination without incident and didn't see any noticeable change in hydraulic fluid levels. I told the Captain receiving the aircraft to watch the hydraulic system because there was something strange about it (just a feeling but nothing that I could prove or show). Both systems were at the same levels as they were when we departed but; again; I simply had an odd feeling about them. There are a few ways that I think this safety issue could have been avoided. Firstly; I have called Maintenance previously when the hydraulic levels were not balanced and they told me to just balance it. By doing so; any slow leak would not be noticed. Due to the nature of the operation and the need to continuously swap aircraft such small leaks could also go unnoticed. Additionally; I personally believe; and I'm not an engineer; that a 40% minimum level of hydraulic pressure is too low for operation (but again I'm not an engineer and don't have the necessary knowledge to determine what is a safe amount). Also; I believe that by fostering a culture where a pilot could freely express his/her feelings may have made me less apprehensive about calling Maintenance about an intuitive feeling even though the numbers were at or above the required levels.

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.