A Virgin airlines 747 (Jumbo) VS 43 bound for Las Vegas, landed back at Gatwick (London) with one of its four main undercarriage ("gear" or wheel assemblies) not lowered to the down position. The plane took off but apparently one of the four hydraulic systems sufferered problems and the crew decided to return to Gatwick. In the event, one of the four gear assemblies did not lower even using the emergency lowering system . The 747 is designed to land on any three of its four main gear assemblies so there was no danger to the plane or its occupants. However in order to land as safely as possible, the crew had to dump many tonnes of aviation fuel in order to reduce the weight of the plane to its lowest possible value to reduce stresses on the remaining wheels. This is a routine enough procedure and the fuel vaporises and does not reach the ground. The final landing was perfect and the plane came to a halt with one wing slightly lower than the other on the failed gear side. There was no damage and no need for an evacuation using the slides. Some passengers according to reports were quite upset, which is understandable despite reassurances from the Captain and cabin crew. The flight was prolonged because Virgin and Boeing had asked the crew to try certain procedures in an attempt to free the failed gear assembly, and they flew past the control tower a couple of times so that the controllers could observe the landing gears with binoculars. Virgin flew them all out the next day on a replacement plane apart from about 13 who chose not to travel for personal reasons. So from a safety standpoint it shows that the 747 flown by a well trained crew is an extremely well designed and safe aircraft where every system including the landing gear can suffer failure without compromising safety - there is always a backup or alternative system.