Possible MH-370 debris found on Reunion Island?

a reply to: lamore

The 777 had a manufacturing issue that allowed chafing around the crew oxygen system. That's how one aircraft was lost while sitting at the gate.

The rules of an emergency are aviate, navigate, communicate. Letting ATC know is step 5 of 5 steps when dealing with an emergency. The first thing you do is make sure the aircraft is OK, then figure out where you're going to land and start planning for that landing, THEN worry about letting people on the ground know.

a reply to: Flyingclaydisk

I've actually heard others acknowledge a frequency change in a similar fashion though.

As for the autopilot, it depends on what the damage was. If it took out the bus that the transponder was on, and the autopilot was on a different bus, it would keep going. If it destroyed the electronics bay the yes it would have taken both out.

a reply to: Zaphod58

Indeed, it could happen (and does, rarely), but it's still incorrect / lazy protocol. To me it casts some probable question on the integrity of the situation on the flight deck. Could there have been a distraction? Could there have been duress? We don't know (obviously), but it is odd...especially given what apparently took place very shortly afterwards.

Regarding the power bus arrangement, I am not familiar with the 777 power bus(es), (and I will attempt to look into them), but in any case that's a pretty big "if". Again, I am no expert on this architecture though.

a reply to: Flyingclaydisk

I believe the transponder and autopilot are on separate busses, but that's going by what others that know better have said.

a reply to: Zaphod58

Each system has its own set of multiple power buses though. Everything on an aircraft must have at least one form of redundancy to get past certification stage.

Interesting and relevant article about ELTs today.

NASA is in the process of crashing three Cessna 172s from an A frame, each loaded with multiple ELTs. This is in response to the crash in Alaska that killed Ted Stevens.

They don't have exact numbers yet, but in 2012 NASA reps testified in front of Congress that based on data they had then, the ELT would fail an estimated 50-60% of the time in a survivable crash.

www.flightglobal.com...

a reply to: lamore

Commercial aircraft only require double redundancy on critical systems. Not every system on the aircraft requires that redundancy.

originally posted by: Zaphod58
a reply to: lamore

Commercial aircraft only require double redundancy on critical systems. Not every system on the aircraft requires that redundancy.

The B777 have triple redudancy for most systems. 3 autopilots powered by seperate busses, 3 flight control computers and so on.

a reply to: Ivar_Karlsen

Not all systems are required to have that though. The critical systems only require double, but there are some that don't even require that. Doesn't mean they aren't set up that way, but they aren't required to have it to certify the aircraft.

originally posted by: Zaphod58
a reply to: Ivar_Karlsen

Not all systems are required to have that though. The critical systems only require double, but there are some that don't even require that. Doesn't mean they aren't set up that way, but they aren't required to have it to certify the aircraft.

The B777 was designed with ETOPS longer than 120 minutes in mind, and to do that at least 4 engine driven generators, 3 autopilots (Cat3B autoland) was required.
Basically, where other planes have bouble systems, the B777 have triple. It was the Boeing design philosophy back when the B777 came about.

a reply to: Ivar_Karlsen

Right, but that's what I'm saying. The critical systems are redundant. A transponder isn't a critical system. It's like when we'd fly a mission with a PMCM jet, because the third radio, or backup navigation system was broken. Yes, they can be important, but they're not going to stop you from flying, or require a precautionary landing.

originally posted by: Zaphod58
a reply to: Flyingclaydisk

I've actually heard others acknowledge a frequency change in a similar fashion though.

As for the autopilot, it depends on what the damage was. If it took out the bus that the transponder was on, and the autopilot was on a different bus, it would keep going. If it destroyed the electronics bay the yes it would have taken both out.

The 777 electric system is robust but the redundancies lead to complexity. The transponder is on the main DC bus, one for each side. Various components of the autopilot are on the left and right AC transfer buses, left and right DC buses, and captain and FO's flight instrument buses. And all of those can be powered by the integrated drive generators on each engine, a backup alternator on each engine, and an auxiliary power unit in the tail. If all else fails (literally) the trip7 also has a rat or ram air tubine which is like a pinwheel that can be extended out of the bottom to provide limited power.

It appears that some of the pasengers' family members believe it is a conspiracy,

"I can't trust them," Wang Wing Lei, whose parents were aboard the jetliner, told NBC News. "This is not the first time they get the wrong news … Why? You tell me why?" Dai Shuqin, another protester whose sister was on board the flight, refused to believe the find was connected to MH370.

"These findings are fake," Dai said. "This is a conspiracy. Everything is fake."

www.nbcnewyork.com...

a reply to: F4guy

The suggestion that there was a cockpit fire that incapacitated the pilots and crew, disabled the transponder, but not the autopilot, and yet happened so sudden that there was no time for radio contact, seems very improbable.

a reply to: F4guy

Provided someone is there to do switch systems. If the crew was incapacitated, the systems wouldn't switch over automatically. At least they didn't when I was working them.

a reply to: GetOutOfMyRoad

Again, communicating is the last thing you worry about. If there's a fire, especially in the cockpit, you deal with it first, you worry about where you're putting the airplane on the ground and how fast you can configure it and get it there, and only then do you worry about talking to anyone on the ground.

a reply to: Zaphod58

They would not send out a mayday?

Aren't 777's equipped with oxygen masks for the pilots?

a reply to: GetOutOfMyRoad

After they fought the fire they'd worry about radioing the ground. There's nothing anyone on the ground can do to help, so deal with the airplane first.

The fire in another aircraft started in the cockpit oxygen supply line area. When several aircraft were built, they didn't put zip ties around some of the wiring in that area, and it rubbed, until it shorted. It was right next to an oxygen line going to the crew oxygen system, which turned it into a blowtorch that eventually destroyed part of the cockpit and burned out the side of it near where the right seat is.

a reply to: Zaphod58

And did the autopilot survive in that case? Would that plane have been able to fly on?

From what I have been reading on the net, not many airplane experts are coming up with this scenario.

Many seem to suggest the transponders were turned off manually, for instance.

a reply to: GetOutOfMyRoad

That aircraft was at the gate when the fire broke out.

Actually, there were a number of them that said this scenario early on, but it's not nearly as exciting as pilot suicide/stealing the plane/hijacking so you almost never hear anyone talking about it being an accident anymore.