Plughoid oscillations
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IIRC do the hydraulic pipes not go through the ceiling rather than the floor in the 747? I thought that was why the crew were so concerned about hydraulic loss during UAL811...
Also, I think that JAL123 and UAL232 caused the development and retrofitting of fuses to the hydraulic systems in passenger transport. The DHL A300 was built in '79 so may not have been modified in this manner. Having said that it lost a lot more than a wingtip.
Also, I think that JAL123 and UAL232 caused the development and retrofitting of fuses to the hydraulic systems in passenger transport. The DHL A300 was built in '79 so may not have been modified in this manner. Having said that it lost a lot more than a wingtip.
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Originally Posted by chornedsnorkack
The problem with hydraulics seems demonstrated by 3 cases of airliners suffering total hydraulic failure despite redundancies.
A300 had a rocket in one wingtip. The aileron was served by three redundant hydraulic systems... so they all failed, and the aileron at the other wingtip as well as the aerodynamic controls of tail, though mechanically intact, became useless. DC-10 had engine shrapnel in tailfin... again, it was served by all three redundant hydraulic systems, so they all duly failed and ailerons, flaps et cetera became useless. B747 has rear bulkhead failure... again, it broke all 4 hydraulic systems, so that e. g. ailerons at the end of, mechanically intact, wings became useless.
How do airplanes deal with this kind of multiple common-cause failures?
A300 had a rocket in one wingtip. The aileron was served by three redundant hydraulic systems... so they all failed, and the aileron at the other wingtip as well as the aerodynamic controls of tail, though mechanically intact, became useless. DC-10 had engine shrapnel in tailfin... again, it was served by all three redundant hydraulic systems, so they all duly failed and ailerons, flaps et cetera became useless. B747 has rear bulkhead failure... again, it broke all 4 hydraulic systems, so that e. g. ailerons at the end of, mechanically intact, wings became useless.
How do airplanes deal with this kind of multiple common-cause failures?
Originally Posted by glhcarl
How do you get the ground spoilers to deploy when you have no hydraulic power?
Cannot understand why Lockheed did not make the flight controls symmetrical down to one system--easily doable, the L-1011 was.
GF
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Originally Posted by galaxy flyer
You made me think, glhcarl! The answer is, the flight manual procedure using the spoilers was for loss of systems 1,2,3, in which case all pitch control was lost. You could use the ground spoilers, powered by remaining system 4 to make rough pitch corrections. Systems 1,2,4 caused loss of roll control.
Cannot understand why Lockheed did not make the flight controls symmetrical down to one system--easily doable, the L-1011 was.
GF
Cannot understand why Lockheed did not make the flight controls symmetrical down to one system--easily doable, the L-1011 was.
GF
Gear Down and Locked:
Aside from the phugoid cycles, why did Boeing design the 737-200 to use hydraulic pressure on all primary controls, regardless of whether manual reversion is safe? The Douglas DC-9 has none, except for a little rudder boost from the right h. system, and accum. pressure available for the elevator control tabs to help recover from a (t-tail) deep stall. Without the right h. system (slats and flaps should extend at a slower rate etc), 135 knots or Vref + 5, until landing assured. No big deal.
Maybe Boeing planned to stretch the fuselage?
MD never had it on the MD-83 primary controls, any more than on the DC-9, from what friends tell me.
Aside from the phugoid cycles, why did Boeing design the 737-200 to use hydraulic pressure on all primary controls, regardless of whether manual reversion is safe? The Douglas DC-9 has none, except for a little rudder boost from the right h. system, and accum. pressure available for the elevator control tabs to help recover from a (t-tail) deep stall. Without the right h. system (slats and flaps should extend at a slower rate etc), 135 knots or Vref + 5, until landing assured. No big deal.
Maybe Boeing planned to stretch the fuselage?
MD never had it on the MD-83 primary controls, any more than on the DC-9, from what friends tell me.
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Trim only approaches and landing.
Trying to land using trim only on some types can develop some good phugoids mainly because one tends to overcontrol.
Best if you try it on a simulator first!
Trying to land using trim only on some types can develop some good phugoids mainly because one tends to overcontrol.
Best if you try it on a simulator first!
glhcarl:
From the guys that flew the L-1011, a lot was similar and recognizable, but the C-5 was definitely the Mark I version. OTOH, I lost a number of systems, one at a time. The book answer for loss of 2 was slow to 200 KIAS, land as soon as practical. 200 Kts approximated the correct stab time for landing. Friends who have landed with 2 out, said all was normal, until close to the ground when you suddenly found out how little authority you have, depending on the systems out.
GF
From the guys that flew the L-1011, a lot was similar and recognizable, but the C-5 was definitely the Mark I version. OTOH, I lost a number of systems, one at a time. The book answer for loss of 2 was slow to 200 KIAS, land as soon as practical. 200 Kts approximated the correct stab time for landing. Friends who have landed with 2 out, said all was normal, until close to the ground when you suddenly found out how little authority you have, depending on the systems out.
GF
