Narrative:

After gear retraction we heard a steady banging noise. I had the first officer check the hydraulics page as it sounded a lot like hydraulic hammering. ATC cleared us up to 11;000 and we requested a lower altitude to look into a problem we were having. We leveled off at 4;000 per ATC and began troubleshooting. I noticed that the #1 main gear was intermittently indicating 'in transit.' we then referred to the QRH which had no guidance on this malfunction. I slowed the aircraft to 180 KTS and cycled the landing gear. When extended we got a good positive downlock indication (3 green [lights]). When retracted one more time we got the same result of hydraulic hammering and intermittent 'in transit' indications. Not knowing if this was a hydraulic system about to fail or a failed up lock; I had the landing gear extended; declared an emergency and returned to the airport for landing. We did not brace the passengers as the gear was solidly indicating green; down and locked and was not giving any indications otherwise. Also; with the gear down the hydraulic hammering ceased. The landing was normal; and we were met by crash fire rescue equipment who inspected the aircraft for external damage and then cleared us to continue to the gate. The flight was canceled shortly thereafter.

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Original NASA ASRS Text

Title: An E-145 flight crew opted to declare an emergency and return to their departure airport when the landing gear repeatedly failed to retract completely and; instead; produced a loud hammering noise. The gear extended normally and a safe; normal landing was made. The flight was canceled.

Narrative: After gear retraction we heard a steady banging noise. I had the First Officer check the hydraulics page as it sounded a lot like Hydraulic Hammering. ATC cleared us up to 11;000 and we requested a lower altitude to look into a problem we were having. We leveled off at 4;000 per ATC and began troubleshooting. I noticed that the #1 Main gear was intermittently indicating 'in transit.' We then referred to the QRH which had no guidance on this malfunction. I slowed the aircraft to 180 KTS and cycled the landing gear. When extended we got a good positive downlock indication (3 green [lights]). When retracted one more time we got the same result of Hydraulic Hammering and intermittent 'in transit' indications. Not knowing if this was a hydraulic system about to fail or a failed up lock; I had the landing gear extended; declared an emergency and returned to the airport for landing. We did not brace the passengers as the gear was solidly indicating green; down and locked and was not giving any indications otherwise. Also; with the gear down the Hydraulic Hammering ceased. The landing was normal; and we were met by CFR who inspected the aircraft for external damage and then cleared us to continue to the gate. The flight was canceled shortly thereafter.

Data retrieved from NASA's ASRS site 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.