Flight 370 and the cell phones on board

[jp1992]

I thought onstar worked through cellular connections?

You are right, onstar uses Verizon's network.

[WiWavelength]

Doesn't plain jane gsm have a maximum range of about 35km due to timing...

 

Yes, single time slot GSM is limited by timing advance to 35 km radius.  That is not the issue here, but it is correct, nonetheless.

 

AJ

[richy]

Yes, single time slot GSM is limited by timing advance to 35 km radius.  That is not the issue here, but it is correct, nonetheless.

 

AJ

Sorry I thought there wouldnt be much more than basic gsm coverage over many of the potential areas for the plane and the additional altitude of the plane would make a connection less likely.

[CaryTheLabelGuy]

 

No seriously, this is baffling to me as well. I'm actually a pilot (one of my many loves) with an instrument rating and have lots of simulator time in the T7 as well as several other airliners. I have several theories as to what might have happened. I don't subscribe to any particular theory, yet. There are just too many unanswered questions.

 

As for GPS on cellphones: GPS is a totally passive technology. There is no communication. The phone sees the satellites (that are in a geosynchronous orbit) and triangulates it's current position using these satellites. For the phone to be tracked in an active way, the phone uses what's called A-GPS (Assisted GPS), in where an active source uses cell towers to triangulate the phones current position. A-GPS is what is used by apps and 911....etc.

 

The GPS systems on an airliner go hand-in-hand with a much older system called an "INS" Inertial Navigation System, which uses gyroscopes and accelerometers to calculate the aircraft's position. The problem with both of these systems - they are both passive. Neither one report they're position to the outside world, they are only used by the navigation systems to calculate their own position.

 

The ACARS "Aircraft Communication Addressing and Reporting System" is used by the aircraft to report system's status as well as flight dynamics to the engineers on the ground, airline dispatchers and the manufacturer (in case of a failure of some sort).

 

The aircraft uses a transponder, with an ATC assigned "squawk" code (4 digits), so that the ground-based ATC radar can "see" the aircraft on the radar screen with the assigned transponder code. The transponder has what's called "Mode C" altitude reporting that must be turned on in order for the aircraft to report its altitude to ATC radar (and to other aircraft through TCAS), through it's assigned transponder "squawk" code. Otherwise, the civilian radar can't tell what altitude the aircraft is flying. The transponder can also be switched to a standby mode, in which it doesn't report at all. When this happens, ATC doesn't see the aircraft at all (other than a blip, which could be anything) and also disables the TCAS (Traffic Collision Avoidance System), which also operates off information given by the transponder in the aircraft as well as transponders from other aircraft. When flying over the ocean and outside of ground-based civilian radar coverage, the pilots report their position to ATC (Air Traffic Control) at scheduled intervals, using the navigation systems on the aircraft. This is because they cannot be seen on radar.

 

A new system called ADS-B is being slowly implemented and will go a long way to solving the issues with the systems mentioned above. It is part of the "Next Generation Air Transportation System".

 

Side note: The T7's navigation system cross-checks all of its instrument and navigation sources. If it senses any abnormal deviation, it warns the pilots of the error and allows them to do their own cross-checking and problem solving. All systems are redundant, including the older INS system.

 

Hopefully this helps some of you. If you guys have any other more in-depth questions, feel free to ask.

[richy]

No seriously, this is baffling to me as well. I'm actually a pilot (one of my many loves) with an instrument rating and have lots of simulator time in the T7 as well as several other airliners. I have several theories as to what might have happened. I don't subscribe to any particular theory, yet. There are just too many unanswered questions. As for GPS on cellphones: GPS is a totally passive technology. There is no communication. The phone sees the satellites (that are in a geosynchronous orbit) and triangulates it's current position using these satellites. For the phone to be tracked in an active way, the phone uses what's called A-GPS (Assisted GPS), in where an active source uses cell towers to triangulate the phones current position. A-GPS is what is used by apps and 911....etc. The GPS systems on an airliner go hand-in-hand with a much older system called an "INS" Inertial Navigation System, which uses gyroscopes and accelerometers to calculate the aircraft's position. The problem with both of these systems - they are both passive. Neither one report they're position to the outside world, they are only used by the navigation systems to calculate their own position. The ACARS "Aircraft Communication Addressing and Reporting System" is used by the aircraft to report system's status as well as flight dynamics to the engineers on the ground, airline dispatchers and the manufacturer (in case of a failure of some sort). The aircraft uses a transponder, with an ATC assigned "squawk" code (4 digits), so that the ground-based ATC radar can "see" the aircraft on the radar screen with the assigned transponder code. The transponder has what's called "Mode C" altitude reporting that must be turned on in order for the aircraft to report its altitude to ATC radar (and to other aircraft through TCAS), through it's assigned transponder "squawk" code. Otherwise, the civilian radar can't tell what altitude the aircraft is flying. The transponder can also be switched to a standby mode, in which it doesn't report at all. When this happens, ATC doesn't see the aircraft at all (other than a blip, which could be anything) and also disables the TCAS (Traffic Collision Avoidance System), which also operates off information given by the transponder in the aircraft as well as transponders from other aircraft. When flying over the ocean and outside of ground-based civilian radar coverage, the pilots report their position to ATC (Air Traffic Control) at scheduled intervals, using the navigation systems on the aircraft. This is because they cannot be seen on radar. A new system called ADS-B is being slowly implemented and will go a long way to solving the issues with the systems mentioned above. It is part of the "Next Generation Air Transportation System". Side note: The T7's navigation system cross-checks all of its instrument and navigation sources. If it senses any abnormal deviation, it warns the pilots of the error and allows them to do their own cross-checking and problem solving. All systems are redundant, including the older INS system. Hopefully this helps some of you. If you guys have any other more in-depth questions, feel free to ask.

 

Whats the chances of survivng landing something like that on anything other than a well maintained runway. If there was an attempt to divert then ransom after a landing on an old 70's \ 80's russian strip in one of the stans or on hard dirt it would be pretty risky if not outright crazy right?

[CaryTheLabelGuy]

Whats the chances of survivng landing something like that on anything other than a well maintained runway. If there was an attempt to divert then ransom after a landing on an old 70's \ 80's russian strip in one of the stans or on hard dirt it would be pretty risky if not outright crazy right?

Well, it depends. It depends on a lot of factors (aircraft weight and balance, altitude of airfield, atmospheric conditions, runway length, runway type, runway condition, pilot skill, luck.....etc). The landing gear of all airliners are very very robust. As long as the aircraft can get down and stopped before over-running the runway, they would most likely make it. The landing is the easy part with regards to runway length, the takeoff roll typically needs more runway length with an aircraft this size. If the T7 is relatively light (most fuel burnt), it's ground roll on a decent runway is surprisingly short, especially if the pilots didn't care about the condition of the aircraft after the landing. The 777-200ER would need at least 6000 feet of runway (in dry conditions with the proper runway condition) for a violent but successful landing roll at a relatively light weight, with a decent headwind, using full flaps, spoilers and reverse thrusters as well as heavy braking. There are plenty of runways out there that could accommodate this landing requirement. The width of a typical runway used by airliners is 150-200' wide. The T7 would need at least 100' width and a good pilot with very little cross-wind (for good measure).

[WiWavelength]

This thread has taken a very interesting turn -- at least 90 degrees.

 

AJ

[kyle_4thousand]

There's a theory of MH 370 following in the shadow of a Singapore Airlines 777 in order to avoid getting detected by Indian and Pakistani radar: http://keithledgerwood.tumblr.com/post/79838944823/did-malaysian-airlines-370-disappear-using-sia68-sq68

 

It's an interesting theory, worth a read.

[CaryTheLabelGuy]

There's a theory of MH 370 following in the shadow of a Singapore Airlines 777 in order to avoid getting detected by Indian and Pakistani radar: http://keithledgerwood.tumblr.com/post/79838944823/did-malaysian-airlines-370-disappear-using-sia68-sq68

 

It's an interesting theory, worth a read.

Somewhat plausible.

 

This theory would need a lot of factors to go perfectly as well as have before-hand information of the other flight's current position, route and destination. There would have been a ton of TCAS traffic to sort through when trying to find the right aircraft to "shadow" and even if they knew which aircraft they wanted to follow (for the correct flight plan) before-hand, their TCAS would not show them a squawk code to identify the aircraft, like ATC radar operators see. It would just be a small diamond that shows relative altitude and position to your aircraft.

 

They could have easily listened to ATC give the other aircraft instructions, but it's highly unlikely that ATC was vectoring the other aircraft at this point. Meaning, the other aircraft was most-likely following it's predetermined and filed flight plan using the autopilot's LNAV / VNAV mode, where the flight plan (longitudinal and vertical) is entered in the FMC (Flight Management Computer) while on the ground, during the pre-flight phase. Usually, the only ATC deviations from this flight plan are during the SID (Standard Instrument Departure) or the STAR (Standard Terminal Arrival Route), which ATC can give radar vectors and altitude restrictions based on traffic and other factors while climbing-out after takeoff (SID) or descending for approach and landing (STAR). Beyond that, at cruising altitude ATC only gives deviations if there is a traffic separation issue. The pilots will continue to fly their pre-filed flight plan from waypoint to waypoint, using autopilot.

 

So MH370 would have to have everything planned-out before hand and know exactly which aircraft they wanted to "shadow" and it's current location and would have to be able to intercept it after identifying it on their TCAS out of the several other TCAS "targets". It would be tough to do, but anything is possible.

 

 

[dstar2002]

I think this is a very logical, well thought out theory, and probably is 100% right.

 

http://www.wired.com/autopia/2014/03/mh370-electrical-fire/

[WiWavelength]

I am simultaneously fascinated by this story and also creeped out. Never flown by plane and this really makes me not want to!

 

Wait, you have never flown?  That is rare in this day and age.  We may have to start playing banjo music as the soundtrack to your posts.

 

Well, I am glad that I got to you in time.  If you ever do fly, remember this.  I had to instruct a middle school classmate about this very thing 20 years ago.  During takeoff, be sure to raise your hands above your head, open your mouth wide, and bawk like a chicken as loud as you can.  Otherwise, as a first time flier, the decompression might make your head explode.

 

AJ

[CaryTheLabelGuy]

I think this is a very logical, well thought out theory, and probably is 100% right.

 

http://www.wired.com/autopia/2014/03/mh370-electrical-fire/

This would be my most logical theory. I have thought about this very theory in-depth. I think it makes the most sense.

[mrknowitall526]

Wait, you have never flown? That is rare in this day and age. We may have to start playing banjo music as the soundtrack to your posts.

 

Well, I am glad that I got to you in time. If you ever do fly, remember this. I had to instruct a middle school classmate about this very thing 20 years ago. During takeoff, be sure to raise your hands above your head, open your mouth wide, and bawk like a chicken as loud as you can. Otherwise, as a first time flier, the decompression might make your head explode.

 

AJ

Nope, never! We used to vacation with my uncle who is afraid of flying so we always went within driving distance ... Even from eastern PA to TN several times.

 

Thanks for the advice...I'll make sure someone has a video of that for you!

 

Sent from my EVO using Tapatalk

 

 

[Mobilesolutions]

It's hard to believe anything the media says, the fire theory makes the most sense in my head.  

[khammondnm]

It's hard to believe anything the media says, the fire theory makes the most sense in my head.

The fire theory doesn't make sense in light of yesterday's news. It was released that the flight path had already been programmed to change before the co-pilot spoke on the last transmission. If it had been a fire, they would have likely signaled mayday on that last transmission.

 

Sent from my Nexus 5

 

 

[The Dave]

 

I have the undeniable truth of what happened.

[Mobilesolutions]

The fire theory doesn't make sense in light of yesterday's news. It was released that the flight path had already been programmed to change before the co-pilot spoke on the last transmission. If it had been a fire, they would have likely signaled mayday on that last transmission.

 

Sent from my Nexus 5

Another dying theory, I agree they wouldn't sign off calmly in a fire.

[CaryTheLabelGuy]

The fire theory doesn't make sense in light of yesterday's news. It was released that the flight path had already been programmed to change before the co-pilot spoke on the last transmission. If it had been a fire, they would have likely signaled mayday on that last transmission.

 

Sent from my Nexus 5

I wouldn't put too much weight on anything coming from the media at this point. They're just not reliable sources of information. They've screwed up all kinds of info since this thing has started and confused everybody in the process.

 

That being said, I'm not sure how they would know this. To my knowledge, there is now way for anybody to know what was programmed into the FMC and when it was programmed, remotely. If they knew when the flight plan was changed, they should know what was programmed.

 

If the FMC flight plan was changed after their last hand-off, it would make better sense. If they were overcome by smoke from say a blown or low-pressure tire that burned in the wheel well for an hour or so, they could have been trying to get to the nearest suitable airport and entered it into their FMC and executed the turn and just didn't have the chance to contact ATC about the emergency. We always Aviate, Navigate then communicate. So communication of the emergency is last on the list. They would have their hands full with shutting systems down (pulling breakers) trying to isolate the fire (which could explain the ACARS and transponder going dead).

 

If it was in-fact a blown tire, they would have a master warning in regards to the tire pressure of said tire, so I'm not sure how they would have missed that.

 

Pure speculation at this point. We may never know what really happened.

[uh60james]

When the plane went to 45k feet everyone would of died if the oxygen masks had already used up their supplies (chemical generation of oxygen), where the pilot(s) are on bottled oxygen which will last much longer.

 

Even with the masks providing oxygen at 45,000 feet the passengers and crew in the cabin would only have a few minutes for the plane to get down to about 10,000 feet.  These masks won't do much for you other than keeping you alive for a few minutes, there is a reason you are told to assist children put them on before you put yours on, the chance of losing of consciousness or simply not having the ability to function will present itself very quickly.  The crew of the flight deck should be equipped with pressure masks which will allow them to continue fairly normally until returning to a safe altitude.

[njjdnt]

 there is a reason you are told to assist children put them on before you put yours on, the chance of losing of consciousness or simply not having the ability to function will present itself very quickly.  

I thought you are supposed to put on your mask before assisting others?  Maybe I should pay more attention from now on. 

[uh60james]

I thought you are supposed to put on your mask before assisting others?  Maybe I should pay more attention from now on. 

No, you are correct.  I mispoke.  But the reason remains the same 

[CaryTheLabelGuy]

Even with the masks providing oxygen at 45,000 feet the passengers and crew in the cabin would only have a few minutes for the plane to get down to about 10,000 feet. These masks won't do much for you other than keeping you alive for a few minutes, there is a reason you are told to assist children put them on before you put yours on, the chance of losing of consciousness or simply not having the ability to function will present itself very quickly. The crew of the flight deck should be equipped with pressure masks which will allow them to continue fairly normally until returning to a safe altitude.

The passenger cabin's oxygen supply would last more than a "few" minutes. It is supposed to last at least 15 minutes, which is more than enough time for an emergency descent, pending the pilots reacted quickly to get their oxygen masks on and start their emergency decent checklist.

 

The passenger oxygen system only deploys if the cabin altitude reaches above 14,000' MSL. Typically, at normal cruising altitudes, cabin altitudes are much much lower (no more than 7,000', usually), depending on how high the aircraft is cruising and how high the aircraft was intended to cruise safely. In a slow decompression, the cabin altitude might not exceed the required 14,000' for very long, despite the aircraft cruising at a normal Flight Level for cruise. It should give the flight crew more than enough time to react and start the emergency descent checklist. In a rapid decompression, the cabin altitude could reach the cruising Flight Level very quickly and probably instantaneously. Even then, the system is supposed to give the passengers at least 15 minutes of oxygen, which again, should be plenty of time as long the plane is flyable.

 

As for the 45,000' info, I don't put much weight in this. 45,000' is a good deal above the 777-200LR's Max Service Ceiling (43,100'). The plane would have been heavy at this point, which would make getting to that altitude very difficult/dangerous and probably resulted in a stall from entering the "coffin corner", where the stall speed is equal to the critical Mach number for a given gross weight and G-loading.

[uh60james]

The passenger cabin's oxygen supply would last more than a "few" minutes. It is supposed to last at least 15 minutes, which is more than enough time for an emergency descent, pending the pilots reacted quickly to get their oxygen masks on and start their emergency decent checklist. The passenger oxygen system only deploys if the cabin altitude reaches above 14,000' MSL. Typically, at normal cruising altitudes, cabin altitudes are much much lower (no more than 7,000', usually), depending on how high the aircraft is cruising and how high the aircraft was intended to cruise safely. In a slow decompression, the cabin altitude might not exceed the required 14,000' for very long, despite the aircraft cruising at a normal Flight Level for cruise. It should give the flight crew more than enough time to react and start the emergency descent checklist. In a rapid decompression, the cabin altitude could reach the cruising Flight Level very quickly and probably instantaneously. Even then, the system is supposed to give the passengers at least 15 minutes of oxygen, which again, should be plenty of time as long the plane is flyable. As for the 45,000' info, I don't put much weight in this. 45,000' is a good deal above the 777-200LR's Max Service Ceiling (43,100'). The plane would have been heavy at this point, which would make getting to that altitude very difficult/dangerous and probably resulted in a stall from entering the "coffin corner", where the stall speed is equal to the critical Mach number for a given gross weight and G-loading.

I'm not going to argue with you, I really don't know much about how cabin pressurization works since my experience is all rotary wing.  But I will say that with my experience in the hypobaric chamber for training as well as flying at high altitudes in Afghanistan I would not trust non pressurized oxygen to keep me alive long at that altitude.