Hello,the other day I experienced a Sys 4 Hyd failure. The manual says: Plan to land at the next suitable airport. I was flying VHHX - EHAM and was in the middle of China. What would you do in reality? Fly back to Hong Kong with fuel jettison? The plane was flying perfectly so why not handle the problem when landing at the destination.GreetingsEd

Different airlines have differing policies on such matters depending on the specific issue. In the real world you would likely consult with the airline maintenace dept. before making a final decision. However, you should keep in mind that although "the plane was flying perfectly," it was flying with less safety backup than before. If something else were to go wrong and you lost a second hydraulic system, especially the #1 SYSTEM which backs up the #4 system, you could find yourself facing greater complications. It may not seem likey that you would experiece two failures on the same flight, but it does happen.Andrew

The loss of a single hydraulic system is not, in itself, a cause for an enroute diversion. There may be associated reasons for considering a divert ie. If the aircraft was despatched with a single inop pump on another system (maybe an inop ADP or EDP on sys 1,2 or 3).The failure of a second system would be cause for diversion to the nearset suitable airfield.As you will have seen the aircraft flies well with sys 4 inop. The only considerations are a few spoilers wont work and you have to lower the wing gear manually. All the rest is taken care of by an associated back up or paired system.The worst 2 sytems to lose are 2 and 3. No autopilots and no stab trim. Yuk.CheersSteve

Just flew Shanghai-Frankfurt yesterday...lots of sparse country enroute! Many factors go into a good decision. In China it is VERY DIFFICULT to change the plan. I puked an engine over LASHIO Mynmar once (not a land at the nearest... deal), and getting permission to return through China to HKG would have been about impossible. What you have to bear in mind is that significant redundancy is now lost and ya have to start thinking along ETOPS type lines as to bail out points etc. Nearest Suitable can mean a lot of things, especially one has to take into account any degraded operational charcteristics of the aircraft when dealing with winds, runways, new alternates etc. Also ya just might not want to arrive with min fuel at your destination and then have some difficulty with alternate gear extension, crosswind control etc. If one deviates from established procedure, it is good to have really solid defensable reasons for doing so, not too likely to have any sympathetic ears at the following inquest in case of an incident.Tom

Back in the 80s I was on a BA 747 flight from EGLL to KSFO when we had a Hyd failure (I guess it was Sys 4) and they couldn't retract the flaps.After a few comforting words by the Captain and circling for 30-45 minutes we went back to Heathrow where we were ascorted by the rescue team.The aircraft was repaired and seven hours later we took of on the same aircraft.CheersThomas