B747-400
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Bird / Animal
Aircraft Aircraft Damaged; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport
Environment - Non Weather Related
When we rotated we had a bird strike at approximately 50 feet AFE (Above Field Elevation). We saw the bird only a moment before we struck it. There were two birds together; one dove low; and the one that struck the aircraft stayed at the same height. When we passed the birds; we felt a large vibration; heard an audible change in engine sound; and at a safe altitude verified that there was indeed a large indicated N2 vibration on the #4 engine. We advised ATC; and at a safe altitude; we cleaned up the aircraft to flaps 1; and approximately 230 knots; and leveled off at 4000 feet with ATC's concurrence.   As a group; we delegated work load. The Captain (Pilot Flying) controlled the a/c; the First Officer (Pilot Monitoring) handled the left radio (ATC) and myself in the observers seat contacted our Dispatcher via SATCOM. Once initial contact was established and the First Officer took control of the a/c the Captain joined the call. As a group we decided that the vibration would be an issue that would prevent us from continuing to destination and the engine would not be shut down because at idle the vibration was within acceptable limits; and a return was the best course of action. The SATCOM was disconnected from the company and we advised ATC that we would be returning; and original pilot duties were resumed. We were given a hold and a climb to 6000 ft. Once in the hold and at our assigned altitude; we began a planned fuel jettison following the checklist to get below our max landing weight. We Jettisoned fuel from approximately 76;000 kgs to 34;000 kgs. After the fuel jettison checklist was completed; we advised approach that we were ready for vectors to the ILS. A normal approach and landing were executed with all 4 engines under our max landing weight and once on the ground we secured the #4 engine.
B747 Relief Pilot described a bird strike on takeoff that damaged the number four engine. After consulting with the company the crew elects to return to the departure airport after dumping fuel down to maximum landing weight.