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  #101  
Old 03-17-2014, 03:12 PM
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Alley Dweller Alley Dweller is offline
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Originally Posted by Diceman View Post
Still, the point about stealing a cargo plane is a good one. A cargo plane with a couple of guys on it would be forgotten a heck of a lot quicker than a commercial airliner ever will be.
Getting your people on a passenger plane in order to hijack it is pretty easy if you are a government. How are you going to convince a cargo airline to let your people on one of their planes?

Unless, of course, the pilots are the hijackers, in which case getting your people on either type of plane is equally difficult.
  #102  
Old 03-17-2014, 05:45 PM
usedtobe usedtobe is offline
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Forget theft - in addition to a cargo configuration being better for use as a bomb, an empty plane with lots of fuel already aboard would be much more useful. Those things are thirsty, and getting a few hundred tons of Jet A fuel to a strip in the middle of nowhere would likely to also draw attention.
A fleet of tankers all loading Jet A and then heading away from nearby large airports would be suspicious.
Small airports do not stock enough Jet A to fill an empty 777.

Steal a cargo plane being readied for a flight to N. America or Europe, not something full of people and fueled for a short hop to Beijing.
  #103  
Old 03-17-2014, 09:46 PM
Siam Sam Siam Sam is offline
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Sorry, but I had a double take on that archaic term. Aeroplane? Are we living in the earliest part of the 20th century?
That's still standard British spelling. I see it here in Thailand all the time.

I'm afraid this is looking more and more like a case of pilot suicide. BBC mentioned that the deepest parts of the Indian Ocean are something like the third deepest on Earth. Maybe he wanted to minimize the chances of ever being found.
  #104  
Old 03-18-2014, 08:25 AM
nevadaexile nevadaexile is offline
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Originally Posted by Alley Dweller View Post
Getting your people on a passenger plane in order to hijack it is pretty easy if you are a government. How are you going to convince a cargo airline to let your people on one of their planes?

Unless, of course, the pilots are the hijackers, in which case getting your people on either type of plane is equally difficult.
The hijackers could conceal themselves inside the cargo and exit once the plane was in flight. Air cargo scrutiny, especially that from established shippers, is surprisingly lax. They then travel to the cockpit, overwhelm a surprised flight crew and they'd have an aircraft.
  #105  
Old 03-18-2014, 09:47 AM
bengangmo bengangmo is offline
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Originally Posted by nevadaexile View Post
The hijackers could conceal themselves inside the cargo and exit once the plane was in flight. Air cargo scrutiny, especially that from established shippers, is surprisingly lax. They then travel to the cockpit, overwhelm a surprised flight crew and they'd have an aircraft.
Which works fine except for the minor detail that (as I understand it) the hold of a cargo plane is not heated and that the cargo may very well be packed in a way that makes it impossible to exit your hiding place, and / or reach the cockpit.

Also - as to the idea of jet fuel. Sure, if you have to take enough jet fuel all in a day or two to refuel a 777 then eyebrows may very well be raised.

BUT

What if
a) You are a state level player? Then the amount to refuel is going to be chicken feed
b) You have a longer time frame - say 6 months, to refuel the plane? How hard would it be, really, to move a few thousand gallons a day from different places if you are not constrained by time?

Also - it's my understanding, that jet engines aren't particularly sensitive over what fuel they have - so perhaps "pure" jet fuel is not required - isn't jet fuel mostly just kerosene anyway?
  #106  
Old 03-18-2014, 11:40 AM
Diceman Diceman is offline
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Since we're speculating on state-level actors, one possible use of a stolen plane would be to carry a nuclear bomb. If one of the world powers wanted to nuke someone else and get away with it (ie, not start WWIII) then they would absolutely need a delivery vehicle that could not be traced back to them in any conceivable way. Any country capable of planning such an attack would be able to alter the plane's appearance, and these days they could probably fit the plane to fly by remote control, so finding someone willing to sacrifice themself would be unnecessary.
  #107  
Old 03-18-2014, 11:46 AM
bengangmo bengangmo is offline
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Well...indulging in conspiracy theories...

That being the case -

If somebody wanted to nuke NK without the rest of the world knowing who - does NK have the capability to intercept such an attempt?

Assuming that such a thing did happen - is there anyway to determine where the nuclear device originated from (a-la a Tom Clancy novel)?

Alternatively - what if someone was able to get a dose of something like bubonic plague or small pox - just how hard would it be to "weaponise" such a thing, and then use the 777 as a delivery vehicle?
  #108  
Old 03-18-2014, 11:54 AM
Siam Sam Siam Sam is offline
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Originally Posted by Diceman View Post
Since we're speculating on state-level actors, one possible use of a stolen plane would be to carry a nuclear bomb. If one of the world powers wanted to nuke someone else and get away with it (ie, not start WWIII) then they would absolutely need a delivery vehicle that could not be traced back to them in any conceivable way. Any country capable of planning such an attack would be able to alter the plane's appearance, and these days they could probably fit the plane to fly by remote control, so finding someone willing to sacrifice themself would be unnecessary.
Hmmm. And Iran was along the direction of that northern corridor they said was one possible flight path.
  #109  
Old 03-18-2014, 12:06 PM
ZenBeam ZenBeam is offline
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Radar suggests that the plane climbed to 45,000 feet shortly after is disappeared from civilian radar. Whoever took the plane was being very methodical, so he probably didn't climb to 45,000 feet just for fun. The only reason I can think to do that would be to incapacitate the passengers.

Could the pilot depressurize the plane (while wearing an Oxygen mask himself)? Could he disable the passenger compartment Oxygen masks, either overriding them dropping down, or disabling the flow of Oxygen? For that matter, how long will the Oxygen last if he can't disable it?

People can barely breath at 29,000 feet at the top of Everest, so I'd expect no one would last long at 45,00 feet. With the passengers dead, the pilot could set his waypoints for the autopilot, descend or repressurize the plane, then find and turn off any cell phones that anyone may have had out.
  #110  
Old 03-18-2014, 02:02 PM
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Originally Posted by ZenBeam View Post
Radar suggests that the plane climbed to 45,000 feet Could the pilot depressurize the plane (while wearing an Oxygen mask himself)? Could he disable the passenger compartment Oxygen masks, either overriding them dropping down, or disabling the flow of Oxygen? For that matter, how long will the Oxygen last if he can't disable it?
If the pilot/hijackers could do any of these things, it would eliminate the need to have to arrange some sort of "death squad" at the landing site. I suspect the oxygen wouldn't last more than a few hours max, since the plane's designers were no doubt assuming that the pilot would head to the nearest available airstrip in the event of a depresurization.
  #111  
Old 03-18-2014, 02:39 PM
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Kiber Kiber is offline
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I'll defer to Richard Pearse and others who have been very helpful in the other MPSIMS thread. But I believe the takeaway was that the passengers O2 system is only designed to last a few minutes - merely long enough for the pilot to fly the plane to a lower altitude where oxygen would not be necessary. The cockpit crew has a separate O2 system which lasts longer. Also, it is possible for the pilot to manually de-pressurize the aircraft, and then stay at a high altitude until the passenger oxygen ran out.

The bottom line is that it would by possible for a pilot to manually depressurize the plane and maintain a high altitude until the passengers were all incapacitated / dead, prior to descending to a lower altitude.
  #112  
Old 03-18-2014, 02:46 PM
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Originally Posted by Kiber View Post
I'll defer to Richard Pearse and others who have been very helpful in the other MPSIMS thread. But I believe the takeaway was that the passengers O2 system is only designed to last a few minutes - merely long enough for the pilot to fly the plane to a lower altitude where oxygen would not be necessary. The cockpit crew has a separate O2 system which lasts longer. Also, it is possible for the pilot to manually de-pressurize the aircraft, and then stay at a high altitude until the passenger oxygen ran out.

The bottom line is that it would by possible for a pilot to manually depressurize the plane and maintain a high altitude until the passengers were all incapacitated / dead, prior to descending to a lower altitude.
In the other thread, Richard Pearse said the passenger's oxygen only lasts about 10 minutes, long enough for the pilot to drop below 10,000 feet.

So, if the pilot/hijacker is able to depressurize the cabin, killing the passengers via oxygen deprevation would actually be pretty easy to do
  #113  
Old 03-18-2014, 03:33 PM
control-z control-z is offline
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Originally Posted by ZenBeam View Post
Radar suggests that the plane climbed to 45,000 feet shortly after is disappeared from civilian radar. Whoever took the plane was being very methodical, so he probably didn't climb to 45,000 feet just for fun. The only reason I can think to do that would be to incapacitate the passengers.
One reason to climb that high would be to attempt to put out a fire. This Wired article speculates they had a fire and wanted to starve the fire of oxygen.
  #114  
Old 03-18-2014, 03:55 PM
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One reason to climb that high would be to attempt to put out a fire. This Wired article speculates they had a fire and wanted to starve the fire of oxygen.
If so, a Mayday call would be likely. If intentional suicide, it would not be. So far, we haven't heard a Mayday. And turning off the transponder won't help put out a fire unless the fire caused the transponder failure, and suddenly.
  #115  
Old 03-18-2014, 05:22 PM
TonySinclair TonySinclair is offline
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I didn't know a passenger plane could even get to 45,000 feet. If they can, why is normal cruising altitude more like 30,000? Seems like the higher you go, the less air resistance. Does ice build up a lot faster if you go much higher?
  #116  
Old 03-18-2014, 06:02 PM
Raguleader Raguleader is offline
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Air gets thinner too, so go too high and your engine performance will suffer. Fighters intended for high-altitude combat in WWII had to have fairly specialized hardware to allow their engines to perform at 20,000 feet, which is why many cheaper but otherwise very good aircraft were sent to the Mediterranean, the Pacific, and Asia, where combat happened at lower altitudes. But yeah, icing is also going to be an issue. IIRC, the temperature drops something like 10 degrees F for every 1000 feet you go up, and where airliners operate the temperatures are usually below freezing. It's been pointed out by many a pedantic history nerd that Icarus was under no danger of burning up from flying too high, not that it'd matter to him once he got high enough to asphyxiate or for the wax on his wings to get brittle and break up from freezing.

Last edited by Raguleader; 03-18-2014 at 06:04 PM.
  #117  
Old 03-18-2014, 06:14 PM
nevadaexile nevadaexile is offline
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Originally Posted by bengangmo View Post
Which works fine except for the minor detail that (as I understand it) the hold of a cargo plane is not heated and that the cargo may very well be packed in a way that makes it impossible to exit your hiding place, and / or reach the cockpit.
The hold has to be heated as cargo planes carry various types of cargo, some of it is perishable or could be damaged if it were unheated. Also, many flights carry a loadmaster whose job it is to watch the load during the flight to make certain that it does nit shift and make the pilot if kit does ( a shifting load will throw the plane's center of gravity off and might cause a crash). The loadmaster would probably not wish to work in subzero conditions.

Finally, fluids flow through the cargo hold's walls, hydraulic fluid being one of them. If the cargo hold were unheated, the fluids could freeze and that would cause assorted problems with the controls.
  #118  
Old 03-18-2014, 06:40 PM
Daylate Daylate is offline
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[QUOTE ...the temperature drops something like 10 degrees F for every 1000 feet you go up][/QUOTE]

Actually, the temperature drop is 3.5 per 1000 feet. If you ask an engineer about this, he will call it "the adiabatic lapse rate" if you don't stop him.

Here's what Wikipedia says about it:

Quote:
Although the actual atmospheric lapse rate varies, under normal atmospheric conditions the average atmospheric lapse rate results in a temperature decrease of 3.5F/1,000 ft (6.4C/km) of altitude.
  #119  
Old 03-18-2014, 07:07 PM
PhillyGuy PhillyGuy is offline
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Originally Posted by TonySinclair View Post
I didn't know a passenger plane could even get to 45,000 feet.
According to this, the 747-400 has a 45,000 foot ceiling:

http://www.askcaptainlim.com/-air-sa...-altitude.html

Note what my link says about the 777:

Quote:
On a Boeing 777, the maximum service ceiling (altitude at which the maximum rate of climb is reduced to around 100 feet/min) or aircraft*s certification altitude is 43,100 feet.
It sounds like it is difficult to climb much past the service ceiling. How accurate is the radar that gave that 45,000 foot reading?

A lot of what I read about this is impossible to make sense of without knowing how often the situation occurs in normal aviation. Take this:

http://www.npr.org/blogs/thetwo-way/...-disappearance

Quote:
"The informal hand-off went against standard radio procedures, which would have called for the speaker to read back instructions for contacting the next control centre and include the aircraft's call sign, said Hugh Dibley, a former British Airways pilot and a Fellow of the Royal Aeronautical Society.
If an informal handoff happens a lot in the middle of the night in that part of the world, this is insignificant. If virtually unknown, it's important.
  #120  
Old 03-18-2014, 07:30 PM
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I'm going with it having been hijacked by pirates, who will sell it to cargo cultists. The passengers are enjoying life on an island paradise, but are getting sick of a diet of yams, taro, and coconuts. Some of the scientists among them are working out the final details of a coconut radio and we will be hearing from them real soon now.
  #121  
Old 03-18-2014, 10:58 PM
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Originally Posted by TonySinclair View Post
I didn't know a passenger plane could even get to 45,000 feet. If they can, why is normal cruising altitude more like 30,000? Seems like the higher you go, the less air resistance. Does ice build up a lot faster if you go much higher?
45K is above the 777's rated maximum altitude.

Yes, it gets easier to fly as you go higher, but other factors start to kick in, and you begin to get diminishing returns. 30-33K is a good compromise for all factors.
  #122  
Old 03-19-2014, 12:54 AM
erysichthon erysichthon is offline
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Originally Posted by Musicat View Post
If so, a Mayday call would be likely. If intentional suicide, it would not be. So far, we haven't heard a Mayday. And turning off the transponder won't help put out a fire unless the fire caused the transponder failure, and suddenly.
Did you read the Wired article? According to the author, an experienced pilot, turning the plane toward the nearest airport and dealing with the fire would have been the immediate priorities. They didn't send a distress call because they were busy trying to put the fire out, and it's likely that everyone aboard was incapacitated by smoke within moments.

This is the timeline of the theory, as presented in the article:

(1) Electrical fire starts and the cabin interior starts filling with smoke.
(2) Pilot immediately turns the plane toward the closest available airstrip. This accounts for the sharp turn west.
(3) Crew disconnects electrical circuits to isolate the fire. This would result in the transponder going silent.
(4) Passengers and crew are overcome by smoke and lose consciousness. (The crew doesn't go on oxygen because it can make a fire worse.)
(5) Plane continues on automatic pilot until the fuel runs out and it crashes.

Read the article. The author's theory is compellingly simple and straightforward.

I don't understand why people are so determined to believe that this is something weird and exotic like stealing a plane and hiding it somewhere for future use.

Last edited by erysichthon; 03-19-2014 at 12:57 AM. Reason: edit
  #123  
Old 03-19-2014, 01:05 AM
Conor Nielson Conor Nielson is offline
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Ideally based on its fuel capacity, it won't last up until this day. If they were able to land then it is impossible not to detect where they have landed. If they crashed, their debris would have been seen already. You know there's something wrong in this world when NSA can locate and listen to any mobile devices (including Merkel) yet handful of nations with frigate, destroyers, drones, aircrafts, Sats, radars can't locate 239 mobile, 2 transponders, ACARS, Sat-Com, VHF, UHF, beacons.
  #124  
Old 03-19-2014, 01:34 AM
usedtobe usedtobe is offline
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Cargo can be heated, but, last I heard, it was not all within the pressure vessel (the part of the plane which is capable of being pressurized).

Before you ask: Boeing uses "bleed air" for heat/pressure/de-ice. Bleed air comes from a part of the engines which gets hot - don't know exactly where, or if it is in the "hot section" or just near it.

When shipping live cargo (breeding animals, for one), you always specify heated and pressurized cargo hold.

Last time I saw an airliner being loaded, the stuff was placed in aluminum containers, sized and shaped to match the the bottom of the plane. The containers were closed, and nothing could escape. They were also jammed together to prevent their sliding out of assigned position.

If you remember the pic of the plane standing on its tail at the gate: a container that was supposed to go near the center of gravity got installed in the tail - and the tail was the only place with a container (it is the first loaded).
  #125  
Old 03-19-2014, 01:42 AM
Richard Pearse Richard Pearse is offline
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Originally Posted by steveroo View Post
Did you read the Wired article? According to the author, an experienced pilot, turning the plane toward the nearest airport and dealing with the fire would have been the immediate priorities. They didn't send a distress call because they were busy trying to put the fire out, and it's likely that everyone aboard was incapacitated by smoke within moments.

This is the timeline of the theory, as presented in the article:

(1) Electrical fire starts and the cabin interior starts filling with smoke.
(2) Pilot immediately turns the plane toward the closest available airstrip. This accounts for the sharp turn west.
(3) Crew disconnects electrical circuits to isolate the fire. This would result in the transponder going silent.
(4) Passengers and crew are overcome by smoke and lose consciousness. (The crew doesn't go on oxygen because it can make a fire worse.)
(5) Plane continues on automatic pilot until the fuel runs out and it crashes.

Read the article. The author's theory is compellingly simple and straightforward.

I don't understand why people are so determined to believe that this is something weird and exotic like stealing a plane and hiding it somewhere for future use.
Because as has been repeated many times, the aircraft wasn't turned towards the nearest airport in the usual fashion. The normal way to do that in an emergency is to go direct to the nearest suitable airport. That gets you there the quickest, and importantly, it requires the minimum button presses on the flight management computer (FMC). MH370 didn't do this, they turned west and then tracked via several published waypoints that are on an airways route. To get the aircraft to do that requires five times or more the button pressing in the FMC.

The tracking of the aircraft after the westerly turn is simply not consistent with tracking after an emergency. Something else has happened.

It is also being reported that the first waypoint was entered into the FMC before they lost contact, that indicates a deliberate act if true. (How do they know? Apparently it is something the ACARS can report.)
  #126  
Old 03-19-2014, 02:40 AM
Richard Pearse Richard Pearse is offline
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I didn't know a passenger plane could even get to 45,000 feet. If they can, why is normal cruising altitude more like 30,000? Seems like the higher you go, the less air resistance. Does ice build up a lot faster if you go much higher?
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Originally Posted by Musicat View Post
45K is above the 777's rated maximum altitude.

Yes, it gets easier to fly as you go higher, but other factors start to kick in, and you begin to get diminishing returns. 30-33K is a good compromise for all factors.
The effects of altitude on flight is that the air is thinner and colder. Cold is good but thin is bad, the thinness wins out over the cold. This means the engines are less effective overall and the wings are less effective which results in a higher stalling speed. Also the speed of sound is slower so you run into compressibility affects at a slower speed. On the other hand there is less air resistance so you go faster for a given amount of thrust.

So the reason we fly high is that we go faster and burn less fuel which reduces the cost of the flight. Another reason is that you are above most of the weather so it is safer. Icing is not a factor if you go high enough because once the temperature gets cold enough, any moisture is already in the form of ice crystals and doesn't build up on the engine or wings. You are also normally above all of the cloud and icing only happens in cloud.

The downside to flying high is that the max speed you can fly (expressed as a percentage of the speed of sound) decreases and the stall speed increases so you end up with a smaller margin of safe speeds you can fly at. Go high enough and min speed equals max speed and there is no way to be there without losing control.

A heavy aircraft can't fly as high as a light aircraft (ie the same aircraft fully loaded vs lightly loaded or with lots of fuel vs not so much.) That is why most airliners fly in the mid thirties instead of the max altitude they are certified for. The reason they can't go as high is because the increased weight means they need more thrust to climb at a given rate and they need more lift from the wings. Also stalling speed increases with weight so you run into the max/min speed issue, mentioned above, at a lower altitude. Once an airliner has burnt some fuel in the cruise they can climb higher and get the benefits of a further reduction in fuel consumption.

So how DO you get an airliner that's only certified for 43100 feet to climb to 450000 feet? One way is to use the excess speed you have from flying straight in the cruise to do a "zoom climb" where speed is traded for height. This will give you altitude but it is not sustainable altitude and you will have to come back down pretty much straight away.

That assumes you have a light aircraft though. I'm not sure if zoom climbing a B777 to 45000 feet is possible with eight hours fuel and 250 people on board. Maybe it is, but the 45000 foot report is one I'm skeptical of for the moment.

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Originally Posted by nevadaexile View Post
The hold has to be heated as cargo planes carry various types of cargo, some of it is perishable or could be damaged if it were unheated. Also, many flights carry a loadmaster whose job it is to watch the load during the flight to make certain that it does nit shift and make the pilot if kit does ( a shifting load will throw the plane's center of gravity off and might cause a crash). The loadmaster would probably not wish to work in subzero conditions.

Finally, fluids flow through the cargo hold's walls, hydraulic fluid being one of them. If the cargo hold were unheated, the fluids could freeze and that would cause assorted problems with the controls.
Yes, the cargo hold of both passenger aircraft and dedicated freighters is pressurised which means it is also heated as it is the air conditioning system that pressurises the aircraft.

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Originally Posted by Diceman View Post
In the other thread, Richard Pearse said the passenger's oxygen only lasts about 10 minutes, long enough for the pilot to drop below 10,000 feet.

So, if the pilot/hijacker is able to depressurize the cabin, killing the passengers via oxygen deprevation would actually be pretty easy to do
I pulled that 10 minutes out of my arse a bit. The type I fly is required to have 10 mins for the passengers but I have since refreshed my memory with a look through the books and it actually has 15 minutes supply, still not a lot, enough to get down to a safe altitude if you lose pressurization. I don't have a figure for the B777 but it would be in the ball park of that.
  #127  
Old 03-19-2014, 02:57 AM
Richard Pearse Richard Pearse is offline
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Originally Posted by usedtobe View Post
Cargo can be heated, but, last I heard, it was not all within the pressure vessel (the part of the plane which is capable of being pressurized).

Before you ask: Boeing uses "bleed air" for heat/pressure/de-ice. Bleed air comes from a part of the engines which gets hot - don't know exactly where, or if it is in the "hot section" or just near it.

When shipping live cargo (breeding animals, for one), you always specify heated and pressurized cargo hold.
I think you'll find that the cargo hold is entirely within the pressure hull and it is pressurised by the same conditioned air that the passengers get. The air is bled off one the compressor stages, so before the "hot section", but because it is at very high pressure it is also at high temperature. The air conditioning packs cool it down until it is too cold and the typically mix it back with some warm air to get an appropriate temperature. That is all generic info not specific to the 777. For interest, the B787 doesn't use bleed air for air conditioning, the air conditioning is all electric. This means more power available for the engines (bleeding air from the engines steals available mass airflow and therefore thrust) and cleaner fresher air.

Having a look at the B777 manuals at smart cockpit.com I see that the cargo holds have separate temperature controls but are still inside the pressure hull.
  #128  
Old 03-19-2014, 03:07 AM
Arabella Flynn Arabella Flynn is offline
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Originally Posted by TonySinclair View Post
I didn't know a passenger plane could even get to 45,000 feet. If they can, why is normal cruising altitude more like 30,000?
That depends on the plane, the route, and how long you intend to stay there. About a week ago, I was on a 737 from Logan to Minneapolis -- a fairly well-traveled corridor, as several airlines use the Twin Cities as a hub -- and the pilot indicated in passing that our cruising altitude was going to be 40,000 ft. FL400 is uncommon and FL450 even more so, but they're not totally unheard of. You can be cleared to fly higher than you'd normally do if in order to get over some nasty weather, for example.

The operational ceiling is less a matter of the airframe than the engines. I have a family member who works on small jet and turbofan engines, and I inquired once about the incident in 1999, where a Learjet depressurized and ended up drifting, pilotless, across the Midwest for quite some time before crashing. He says you can get the smaller engines a bit above their operational ceiling, but it takes a very long time to get those last few thousand feet. It can happen unattended, as it did with the Learjet, but you'd have to get stuck in a pretty aggressive climb for quite a while. Since the problem is a lack of air and therefore a lack of compression, I expect it would be the same deal with the big boys.
  #129  
Old 03-19-2014, 03:18 AM
usedtobe usedtobe is offline
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If the entire hull is now pressurized, how about the belly tank on the long-range 747 (and whatever else uses a belly tank)? Is it pressurized, and if so, how is it vented? Or is it vented in the conventional sense?
  #130  
Old 03-19-2014, 03:24 AM
usedtobe usedtobe is offline
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If you want a study in wringing out the last few feet of max ceiling, see Pinnacle Air 3701 - two pilots had the plane all to themselves, and the shop had a "secret" society for those who had gotten the plane to max ceiling - FL410, or 41,000'.

It is an incredibly pathetic story

Goggle has a story, didn't read.

Here is a link to the NTSB's aviation incident/accident database - their write-up is quite lengthy and detailed - a blow-by-blow of incredible arrogance gone wrong.

http://www.ntsb.gov/aviationquery/index.aspx
  #131  
Old 03-19-2014, 03:44 AM
Richard Pearse Richard Pearse is offline
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Originally Posted by usedtobe View Post
If the entire hull is now pressurized, how about the belly tank on the long-range 747 (and whatever else uses a belly tank)? Is it pressurized, and if so, how is it vented? Or is it vented in the conventional sense?
I wouldn't have thought fuel tanks would be part of the pressure hull, aren't they part of the centre section of the wing? I don't know. In general though it is simpler to have the round bits of fuselage holding the pressure in rather than having parts that aren't pressurised. It is structurally more sound than trying to make bits of flat floor part of the pressure hull.
  #132  
Old 03-19-2014, 07:45 AM
nevadaexile nevadaexile is offline
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Originally Posted by usedtobe View Post
Cargo can be heated, but, last I heard, it was not all within the pressure vessel (the part of the plane which is capable of being pressurized).

Before you ask: Boeing uses "bleed air" for heat/pressure/de-ice. Bleed air comes from a part of the engines which gets hot - don't know exactly where, or if it is in the "hot section" or just near it.

When shipping live cargo (breeding animals, for one), you always specify heated and pressurized cargo hold.

Last time I saw an airliner being loaded, the stuff was placed in aluminum containers, sized and shaped to match the the bottom of the plane. The containers were closed, and nothing could escape. They were also jammed together to prevent their sliding out of assigned position.

If you remember the pic of the plane standing on its tail at the gate: a container that was supposed to go near the center of gravity got installed in the tail - and the tail was the only place with a container (it is the first loaded).
The cargo HOLD needs to maintain a constant temperature, not necessarily the cargo itself. Having flown on military cargo aircraft in the past, I can tell you that they keep the temperature tolerable within the plane. A person wishing to commandeer the plane would have endure minor temp changes until it got to altitude and then find a way to escape the cargo carrier in which they are concealed.

However, this is beginning to look more like an on board fire and one or more mistakes by the pilots than an intentional act. Had they declared an IFE, this mystery would probably be "solved" by now.
  #133  
Old 03-19-2014, 01:27 PM
erysichthon erysichthon is offline
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Originally Posted by nevadaexile View Post
However, this is beginning to look more like an on board fire and one or more mistakes by the pilots than an intentional act. Had they declared an IFE, this mystery would probably be "solved" by now.
This whole situation reminds me of the JFK assassination: the abundantly obvious solution, that Oswald did it, is widely rejected because of this or that odd detail that "doesn't fit." The crew didn't send a distress signal, so therefore the plane MUST be inside a camouflaged hangar in Dr. Evil's secret lair. And so on.

That plane is undoubtedly at the bottom of the ocean right now.
  #134  
Old 03-19-2014, 03:34 PM
control-z control-z is offline
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Originally Posted by steveroo View Post
That plane is undoubtedly at the bottom of the ocean right now.
I would agree with that, but whether it was a sudden catastrophic accident or a deliberate act seems to be the big question now. The pilot, although very experienced, isn't looking so good the more I read about him.
  #135  
Old 03-19-2014, 04:54 PM
erysichthon erysichthon is offline
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Originally Posted by control-z View Post
I would agree with that, but whether it was a sudden catastrophic accident or a deliberate act seems to be the big question now. The pilot, although very experienced, isn't looking so good the more I read about him.
I'd be more inclined to consider the deliberate act theory if the aircraft had immediately crashed after the loss of communication. The fact that it flew on for another seven hours suggests a Payne Stewart kind of scenario to me.
  #136  
Old 03-19-2014, 05:23 PM
usedtobe usedtobe is offline
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Unless the computer (which does much more than the "autopilot" it replaces, but still operates as an autopilot, among other things) was programmed in advance to make those turns at those specific points (were these Victor way points?), somebody was entering new instructions, or was doing a real good job of manual flight.
Either way, at least one person with advanced knowledge of the FMC of a 777 was on the flight deck.
  #137  
Old 03-19-2014, 05:25 PM
aruvqan aruvqan is offline
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I am somewhat boggled that *anybody* thought it was a great idea to leave the off switch to the locator unit where someone could click it off, so the plane could vanish. One would think that one would find it important to be able to track ones very expensive piece of capital equipment ... not to mention crew cargo and passengers.
  #138  
Old 03-19-2014, 06:54 PM
Marley23 Marley23 is offline
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Originally Posted by aruvqan View Post
I am somewhat boggled that *anybody* thought it was a great idea to leave the off switch to the locator unit where someone could click it off, so the plane could vanish.
I think the bottom line is that it is a piece of equipment like any other: it can break or cause problems. That's why they can turn it off.
  #139  
Old 03-19-2014, 08:20 PM
Musicat Musicat is offline
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I think the bottom line is that it is a piece of equipment like any other: it can break or cause problems.
Or cause confusing clutter to controllers when many planes are in the same area. Why the controllers can't selectively disable some, I don't know, but remember, we are talking 1960's technology underneath all the sophistication.
  #140  
Old 03-20-2014, 01:24 AM
Richard Pearse Richard Pearse is offline
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Quote:
Originally Posted by aruvqan View Post
I am somewhat boggled that *anybody* thought it was a great idea to leave the off switch to the locator unit where someone could click it off, so the plane could vanish. One would think that one would find it important to be able to track ones very expensive piece of capital equipment ... not to mention crew cargo and passengers.
This has been addressed many times now, the bottom line is that this is not some kind emergency location device or anything, it is simply a tool that is used to make ATC's life easier and to allow more efficient movement of aircraft. As soon as you are out of radar coverage the transponder is of no particular use as a locator. Also when it is off ATC lose the data tag associated with your aircraft but they can still see your position if they want. Like any other tool in the aircraft it has an off button so it can be turned off, same as all of the other electrical equipment.

The transponder isn't actually a locator at all, the location is provided by Radar bouncing off the airframe, the transponder provides a unique code and altitude information so that ATC can see who you are and how high you are.

Last edited by Richard Pearse; 03-20-2014 at 01:26 AM.
  #141  
Old 03-20-2014, 03:23 AM
Raguleader Raguleader is offline
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Originally Posted by Conor Nielson View Post
Ideally based on its fuel capacity, it won't last up until this day. If they were able to land then it is impossible not to detect where they have landed. If they crashed, their debris would have been seen already. You know there's something wrong in this world when NSA can locate and listen to any mobile devices (including Merkel) yet handful of nations with frigate, destroyers, drones, aircrafts, Sats, radars can't locate 239 mobile, 2 transponders, ACARS, Sat-Com, VHF, UHF, beacons.
Well, it's easy to locate the aircraft the same way you'd locate the cell phone, assuming the radio transmitter is transmitting. The fact that the airplane's transmitters were turned off is the something that's wrong in this world (in this case).

As one of my friends pointed out, being able to track cell phones is irrelevant since most airlines make you turn your phones off anyways (or at least put them in Airplane Mode, which turns off their radios), assuming the phones (and their transmitting radios) survived whatever happened to the rest of the plane anyways. I doubt even a Nokia 3310 would survive a drop from 30K ASL.
  #142  
Old 03-20-2014, 08:33 AM
andrewm andrewm is online now
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Originally Posted by Musicat View Post
Or cause confusing clutter to controllers when many planes are in the same area. Why the controllers can't selectively disable some, I don't know, but remember, we are talking 1960's technology underneath all the sophistication.
As I mentioned in the other thread, the transponder protocols have a finite amount of bandwidth. If every transponder were active at all times, their transmissions would interfere with each other and ATC would receive bad data. Or, the protocol could have been designed for much higher capacity but that would have had to have been traded off with some other cost: less frequent updates, more expensive equipment, or a later introduction date.

Additionally, the older modes supported IDs of only 12 bits (4 octal digits). With fewer than 4000 usable IDs after special reserved, there is a hard limit on how many transponders in an area can be uniquely identified (newer modes have upgraded to 24 bits with permanently assigned unique IDs).
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