B747-400 captain reported a loss of hydraulic fluid during climb. A decision was made to return to t...

Narrative:

Our aircraft had just finished a 'heavy' maintenance check before our flight. During that heavy check; the landing gear was replaced. All indications on preflight and the maintenance sign offs were normal. Passing approximately 10;000; a low hydraulic fluid EICAS message appeared; followed shortly by a hydraulic system pressure message. We followed the checklists; securing the #4 hydraulic system. At maintenance's request we returned to our departure airport; dumping approximately 100;000 pounds of fuel to arrive below maximum landing weight. When we lowered the gear (by alternate means); the left wing landing gear did not show 'down and locked.' we complied with all appropriate checklists; but did not get a down and locked indication. We did a low pass at 300 feet and approximately 200 knots to have tower personnel visually check the gear. It appeared normal. We [advised ATC] at this time and asked for equipment to be standing by. We landed without event. We cleared at the high speed; shut down engines; and maintenance towed the aircraft to a gate. Post flight inspection revealed a 3 inch hole in gear actuator. The gear was down but not locked.

Original NASA ASRS Text

Title: B747-400 Captain reported a loss of hydraulic fluid during climb. A decision was made to return to the departure airport; which necessitated dumping fuel; and using an alternate method for extending the landing gear. A successful landing followed.

Narrative: Our aircraft had just finished a 'heavy' maintenance check before our flight. During that heavy check; the landing gear was replaced. All indications on preflight and the maintenance sign offs were normal. Passing approximately 10;000; a Low Hydraulic Fluid EICAS message appeared; followed shortly by a Hydraulic System Pressure message. We followed the checklists; securing the #4 hydraulic system. At maintenance's request we returned to our departure airport; dumping approximately 100;000 pounds of fuel to arrive below maximum landing weight. When we lowered the gear (by alternate means); the left wing landing gear did not show 'down and locked.' We complied with all appropriate checklists; but did not get a down and locked indication. We did a low pass at 300 feet and approximately 200 knots to have Tower personnel visually check the gear. It appeared normal. We [advised ATC] at this time and asked for equipment to be standing by. We landed without event. We cleared at the high speed; shut down engines; and maintenance towed the aircraft to a gate. Post flight inspection revealed a 3 inch hole in gear actuator. The gear was down but not locked.

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.

Attributes
ACN	1513663
Time
Date	201801
Local Time Of Day	0601-1200
Place
Locale Reference	RCTP.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Route In Use	Other Controlled
Flight Plan	IFR
Component
Aircraft Component	Hydraulic Fluid
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Weight And Balance

B747-400 captain reported a loss of hydraulic fluid during climb. A decision was made to return to the departure airport; which necessitated dumping fuel; and using an alternate method for extending the landing gear. A successful landing followed.