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I'll admit right off the bat that I know next to nothing about aviation. But why is it that such a high tech piece of equipment such as the Malaysian Air Boeing 777 has the ability to shut off it's tracking system? Isn't that something that should always be on? Nowadays with technologies like Onstar or even locating my iphone if it's lost, how can a multimillion dollar aircraft with hundreds of people onboard be able to go almost invisible? Shouldn't all commercial aircraft have a gps system that always stays on? Maybe there's a good reason for all this but I haven't found it yet.
I'll admit right off the bat that I know next to nothing about aviation. But why is it that such a high tech piece of equipment such as the Malaysian Air Boeing 777 has the ability to shut off it's tracking system? Isn't that something that should always be on? Nowadays with technologies like Onstar or even locating my iphone if it's lost, how can a multimillion dollar aircraft with hundreds of people onboard be able to go almost invisible? Shouldn't all commercial aircraft have a gps system that always stays on? Maybe there's a good reason for all this but I haven't found it yet.
Believe it or not, GPS is technically not the most accurate navigational tool aircraft have. Usually, when aircraft are flying, they are "pinging" ground based VOR (VHF Omnidirectional Range) towers. Based on the response time received back from the towers (and since the towers are fixed to the Earth and not moving like satellites) the aircraft can triangulate its position very accurately.
Second on the list is GPS (most aircraft have two) - which is, no doubt, extraordinarily accurate. But, depending on how it's tied in with other systems, a malfunctioning GPS can cause nuisance faults so a lot of aircraft offer the option to disable it.
Third, the aircraft has inertial reference units (6 of them on the 777) which are highly sensitive three-ring laser gyroscopes that detect movement of the aircraft on any axis. They are sensitive enough to detect the present latitudinal position of the aircraft based on the spin of the Earth. As the aircraft moves it is the inertia (hence inertial reference) that creates a signal which is used to compute position. IRU's do have a certain amount of gyroscopic precession which can degrade the accuracy over a period of time. That accuracy though, is still very solid. We're talking feet and meters here, not miles and kilometers. I should note that the pitch, roll, and heading (as well as vertical speed and other things like windshear detection in many modern aircraft) is also derived by the IRU systems.
If all of the above fail, then the aircraft can typically fall back on things like True Airspeed and a whiskey compass to determine a rough position.
Usually, two navigation sources are automatically selected to derive present position. In most cases, it's radio (VOR) and GPS with the inertial reference units serving as a "ready-to-go" tertiary backup.
When an aircraft is flying over water and there aren't as many VOR stations available, it is usually using a GPS/IRS combination to derive present position. Even still, with the absence of GPS, six inertial reference units is plenty to get you where you need to go. I believe the 777 doesn't even trigger a failure until 2 of the 6 IRU's have crapped out - that's how reliable they are.
All in all, GPS is really more of a luxury item that most flight crews dealt without having for many decades. There's no doubt that it's useful but it isn't even necessary on most modern aircraft - though all of them have it.
On some military aircraft I worked, the crews had 2 compass systems (and a third "whiskey compass"), 3 intertial reference units, 2 GPS systems, 2 radio navigation systems, and a periscopic sextant (navigating by the stars). If you got lost on one of those, you were freaking hopeless.
Believe it or not, GPS is technically not the most accurate navigational tool aircraft have. Usually, when aircraft are flying, they are "pinging" ground based VOR (VHF Omnidirectional Range) towers. Based on the response time received back from the towers (and since the towers are fixed to the Earth and not moving like satellites) the aircraft can triangulate its position very accurately.
Second on the list is GPS (most aircraft have two) - which is, no doubt, extraordinarily accurate. But, depending on how it's tied in with other systems, a malfunctioning GPS can cause nuisance faults so a lot of aircraft offer the option to disable it.
Third, the aircraft has inertial reference units (6 of them on the 777) which are highly sensitive three-ring laser gyroscopes that detect movement of the aircraft on any axis. They are sensitive enough to detect the present latitudinal position of the aircraft based on the spin of the Earth. As the aircraft moves it is the inertia (hence inertial reference) that creates a signal which is used to compute position. IRU's do have a certain amount of gyroscopic precession which can degrade the accuracy over a period of time. That accuracy though, is still very solid. We're talking feet and meters here, not miles and kilometers. I should note that the pitch, roll, and heading (as well as vertical speed and other things like windshear detection in many modern aircraft) is also derived by the IRU systems.
If all of the above fail, then the aircraft can typically fall back on things like True Airspeed and a whiskey compass to determine a rough position.
Usually, two navigation sources are automatically selected to derive present position. In most cases, it's radio (VOR) and GPS with the inertial reference units serving as a "ready-to-go" tertiary backup.
When an aircraft is flying over water and there aren't as many VOR stations available, it is usually using a GPS/IRS combination to derive present position. Even still, with the absence of GPS, six inertial reference units is plenty to get you where you need to go. I believe the 777 doesn't even trigger a failure until 2 of the 6 IRU's have crapped out - that's how reliable they are.
All in all, GPS is really more of a luxury item that most flight crews dealt without having for many decades. There's no doubt that it's useful but it isn't even necessary on most modern aircraft - though all of them have it.
On some military aircraft I worked, the crews had 2 compass systems (and a third "whiskey compass"), 3 intertial reference units, 2 GPS systems, 2 radio navigation systems, and a periscopic sextant (navigating by the stars). If you got lost on one of those, you were freaking hopeless.
Thanks. That's some good information. The question I still have is why can all those tracking systems be disabled by the pilot? I realize if a tracking system is on the fritz then it may be best to shut it off so that it doesn't interfere with the pilot flying the plane. But it seems to me all of those systems that you pointed out are completely controllable by the pilot and can be disengaged. Isn't there a tracking system on the plane that can not be turned off by the pilot and allows for traffic control or whomever to keep an eye on a plane?
Thanks. That's some good information. The question I still have is why can all those tracking systems be disabled by the pilot? I realize if a tracking system is on the fritz then it may be best to shut it off so that it doesn't interfere with the pilot flying the plane. But it seems to me all of those systems that you pointed out are completely controllable by the pilot and can be disengaged. Isn't there a tracking system on the plane that can not be turned off by the pilot and allows for traffic control or whomever to keep an eye on a plane?
But to your original point, none of those systems are "tracking systems". They are navigation systems that permit accurate positioning of the plane in lat/long on the earth (altitude is still derived from barometric pressure). You are assuming that the plane is always in contact with the ground (or a satellite) and that is just not true. Water covers 70% of the earth.
During the time that the plane is over the water and beyond "line of sight" with ground based tracking technology such as RADAR and the much discussed transponder, the plane would need to send tracking data to a satellite. That is expensive and currently not mandated as necessary. Planes fly from point to point in the sky through gates that are designated as reporting points. Transoceanic flights use long wave radio to send position reports or satellite based communications.
Problem is a lot of airlines won't and don't pay for sat comms as was the case with MH-370.
Now as to what can be turned off, it really isn't all that relevant. At the end of the day the flight crew have complete control over the plane. Any number of things could cause mayhem on the flight, we can't protect against them all.
I agree that some form of satellite based tracking device could be useful, but as a pilot, I want to be able to shut it down if it is causing problems. There's also the question of cost, which the passengers will end up paying, for what amounts to a minuscule probability.
But to your original point, none of those systems are "tracking systems". They are navigation systems that permit accurate positioning of the plane in lat/long on the earth (altitude is still derived from barometric pressure). You are assuming that the plane is always in contact with the ground (or a satellite) and that is just not true. Water covers 70% of the earth.
During the time that the plane is over the water and beyond "line of sight" with ground based tracking technology such as RADAR and the much discussed transponder, the plane would need to send tracking data to a satellite. That is expensive and currently not mandated as necessary. Planes fly from point to point in the sky through gates that are designated as reporting points. Transoceanic flights use long wave radio to send position reports or satellite based communications.
Problem is a lot of airlines won't and don't pay for sat comms as was the case with MH-370.
Now as to what can be turned off, it really isn't all that relevant. At the end of the day the flight crew have complete control over the plane. Any number of things could cause mayhem on the flight, we can't protect against them all.
I agree that some form of satellite based tracking device could be useful, but as a pilot, I want to be able to shut it down if it is causing problems. There's also the question of cost, which the passengers will end up paying, for what amounts to a minuscule probability.
Fair enough. I just find it interesting that there is not some sort of gps based tracking system of planes that is not tied into pilots control system. I guess in a world where I can find my car or phone remotely it is surprising that a sophisticated jet can turn virtually invisible.
Fair enough. I just find it interesting that there is not some sort of gps based tracking system of planes that is not tied into pilots control system. I guess in a world where I can find my car or phone remotely it is surprising that a sophisticated jet can turn virtually invisible.
Actually the plane knows pretty well where it is. The question is whether or not it will tell you.
Fair enough. I just find it interesting that there is not some sort of gps based tracking system of planes that is not tied into pilots control system. I guess in a world where I can find my car or phone remotely it is surprising that a sophisticated jet can turn virtually invisible.
Well, one of the biggest problems you'll find with things like that (to include video cameras in the cockpit) is ALPA... If there's some technology that might threaten to expose the idiocy of a few flight crew members, ALPA will fight it.
Well, one of the biggest problems you'll find with things like that (to include video cameras in the cockpit) is ALPA... If there's some technology that might threaten to expose the idiocy of a few flight crew members, ALPA will fight it.
That is not an ALPA issue. Just cost. Cheap capitalists?
Pilots need to have the ability to disable any system in the plane...if you're dealing with an electrical emergency, you may find the need to dump systems manually as opposed to the automatic shedding that the computers control. In our old school aircraft, the manual way to turn off a system would involve switching the knob to off then pulling and collaring the associated circuit breaker. On later model aircraft the circuit breakers are electronically controlled via the multifunction display (MFD), but they're still available for the pilots to "manually" disconnect.
Pilots need to have the ability to disable any system in the plane...if you're dealing with an electrical emergency, you may find the need to dump systems manually as opposed to the automatic shedding that the computers control. In our old school aircraft, the manual way to turn off a system would involve switching the knob to off then pulling and collaring the associated circuit breaker. On later model aircraft the circuit breakers are electronically controlled via the multifunction display (MFD), but they're still available for the pilots to "manually" disconnect.
Exactly.
Plus, there has never been a perceived need for systems to be "flight engineer proof." I mean, how many times has this issue come up before?
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