777 back up actuator

[leewan]

If a 777 had a hydraulic failure, are there any electrical backup actuators to power the control surfaces. I know that there are cables directly linking it to some spoilers and stabilizers for limited control, but what about total hyd loss but full electric power ?

[TURIN]

Short answer, No.

Spoilers 4 and 11 (see I was listening during the course Mr Drake) are mechanically linked, via cables etc, to the contol column but hydraulic power is still required to move the spolier actuators.

So, if you lose all your hydraulics it's engines and luck as per DC10 Sioux City.

[BigJoeRice]

Turin.

10/10................ tick VG take the rest of the day off for a cold frosty one.

[leewan]

I thought they will have learnt from the sioux city and the jal 747. I just found out that a380 has a back up electrical actuator and a hyd/elec actuator. How's it like for the 747 and 330 ?

[Swedish Steve]

There are few large airliners with any sort of back up system to cope with total hyd failure. The notable exception is the B737 which has manual ailerons and elevators and a standby hyd rudder. But that is because it hasn't changed much since the B737-100! Before the A380, the last aircraft I know with independent hyd actuators was the VC10.

[thongkh]

as far as i know, B777 and A330 have 3 independent hyd system to power up the flight control surface, so if you both engine EDP failed, you should have center hyd system, with it, you still able to move the control surface, when both engine electrical pump failed, you will have APU to power up the aircraft electrical system, and center hyd, if you failed ur APU, you have RAT (Ram Air Turbine), which power up the aircraft and run the center electrical pump. and if RAT also failed... GOOD LUCK . besides, i think when the pilot encounter 2 engine EDP failed, they will land at the nearest airport.
as for B747, we have 4 independent hyd system from 4 diff engine... to have them all fail, possibility quite low

[leewan]

Yes, I know there are multiple redundancies built in.
1. Ctr Hyd Sys
2. APU
3. RAT
But what if it is a total hyd quantity loss due to a leakage or broken line ? I will guess a check valve doesn't help much in those cases.

[MrFixer!!!]

Leewan,

Its would be interesting to know what kind of scenario are you looking for???

Every PCU for all the flight controls have Back-ups meaning they are powered by 2 systems at 1 time, so if you lose either system, there is always control of the a/c.

Redundancy is also there as explained above, and also within the computers which controls them,

Then you have Check valves in the systems if you have any leaks of some sorts.....

But I cant figure out what kind of scenario are you looking at????

I know when Boeing(or Airbus) comes up with any design they have to satisfy all the scenarios to FAA/ or EASA for any eventualities, and then only the Type Certificate is issued. So I am sure most of it should have been covered.......except the ''Finger Trouble of the Crew'' ( sorry no offenses to anyone) !!!!

[SMOC]

Leewan,

On the 747, 757, 767, 777, A320, 330, 340.

No Hydraulics = NO flight controls.

You end up with Accidents like

JAL123

Japan Airlines Flight 123 - Wikipedia, the free encyclopedia

severed all four of the aircraft's hydraulic systems.

and

UA232

United Airlines Flight 232 - Wikipedia, the free encyclopedia

which destroyed all three of the aircraft's hydraulic systems.

Nasa did some research with Propulsion Controlled Aircraft (PCA)

NASA - Past Projects - PCA (Propulsion Controlled Aircraft)

On August 29, 1995, Gordon Fullerton once again made a successful landing using only engine power for control, but for this flight the PCA system was installed on a McDonnell-Douglas MD-11 transport aircraft.

[leewan]

Mr Fixer, my scenario was one of a total hyd loss in all systems due to a broken area where all hyd lines pass through or some other mishap. Well,SMOC answered my q short and simple Just wondered bcos the 380 and 737 classic seems to be the only 90s era a/c that can be controlled with a total hyd loss.