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.
Any realistic chance that that the missing plane landed safely & all the passengers are still alive?
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.
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.
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).
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.)
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.
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.
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.
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.
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.
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?
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.