How does ground realize transponder/ACARS turned off?
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How does ground realize transponder/ACARS turned off?
I'm writing a TV show about a woman who investigates plane crashes for the NTSB.
In the pilot episode (pun intended), a plane goes missing. Everyone assumes it crashed from mechanical failure ... until they realize the transponder was turned off and they start to suspect foul play.
My question is -- how would people on the ground know someone turned off the transponder (and that it didn't just shut down from a catastrophic failure/crash)?
Also, how long would it take for people on the ground to piece this information together?
Many thanks!
In the pilot episode (pun intended), a plane goes missing. Everyone assumes it crashed from mechanical failure ... until they realize the transponder was turned off and they start to suspect foul play.
My question is -- how would people on the ground know someone turned off the transponder (and that it didn't just shut down from a catastrophic failure/crash)?
Also, how long would it take for people on the ground to piece this information together?
Many thanks!
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HI
I'm a pilot, I've also written 2 unproduced feature length film screenplays.
I even have my WGA numbers if you need them. ;-)
I'll ask you a question. IF you were in your house and you were looking across the street at night, and your across the street neighbors house light went out, how would you know if the bulb burned out, or someone switched off the light switch?
Short answer is you wouldn't know. Even the next night, the bulb could have been replaced or the switch could have been used.
IN SHORT, there is NO WAY to know and all the talk on MH370 about the transponder being switched off is null and void until the plane is found.
WHEN the plane is found, you can look at the position of the switch and read if it was on, standby, or off.
So, in your teleplay, you would have to find the plane and find the transponder and look at the position of the switch.
How long? Well, they have to find it, get to it, move stuff around etc.
There are so many little things and no one in the NTSB would assume anything until the investigation had substantial evidence.
There are still cases , decades old, that people disagree on the cause or probable cause. Even though the NTSB has spoken on the subject.
It will be a hard script to write if you want to be faithful to the truth and have dramatic license in an hour script.
And one more thing. Even if the transponder was found switched ON, the antenna cable may have been disconnected, destroyed by a saboteur's acid, or half a dozen other things which would allow the transponder to be ON, but not received by radar on the ground.
Do you have any flying experience? Have you written anything that has been produced? Do you have an agent? Have you ever watched the movie, "FATE IS THE HUNTER" ( you can see it on youtube for nothing) and you will really get ideas about why planes crash at least in the movies!
Oh, do you like butter on your popcorn?
Sugar in your COFFEE? ;-)
I'm a pilot, I've also written 2 unproduced feature length film screenplays.
I even have my WGA numbers if you need them. ;-)
I'll ask you a question. IF you were in your house and you were looking across the street at night, and your across the street neighbors house light went out, how would you know if the bulb burned out, or someone switched off the light switch?
Short answer is you wouldn't know. Even the next night, the bulb could have been replaced or the switch could have been used.
IN SHORT, there is NO WAY to know and all the talk on MH370 about the transponder being switched off is null and void until the plane is found.
WHEN the plane is found, you can look at the position of the switch and read if it was on, standby, or off.
So, in your teleplay, you would have to find the plane and find the transponder and look at the position of the switch.
How long? Well, they have to find it, get to it, move stuff around etc.
There are so many little things and no one in the NTSB would assume anything until the investigation had substantial evidence.
There are still cases , decades old, that people disagree on the cause or probable cause. Even though the NTSB has spoken on the subject.
It will be a hard script to write if you want to be faithful to the truth and have dramatic license in an hour script.
And one more thing. Even if the transponder was found switched ON, the antenna cable may have been disconnected, destroyed by a saboteur's acid, or half a dozen other things which would allow the transponder to be ON, but not received by radar on the ground.
Do you have any flying experience? Have you written anything that has been produced? Do you have an agent? Have you ever watched the movie, "FATE IS THE HUNTER" ( you can see it on youtube for nothing) and you will really get ideas about why planes crash at least in the movies!
Oh, do you like butter on your popcorn?
Sugar in your COFFEE? ;-)
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Thank you so much!
I was wondering why everyone was so convinced the transponder was turned off on MH370. But after reading your message, it seems like the conclusion is based on circumstantial evidence (i.e. because the plane continued to show up on primary radar after the transponder went dead, and ACARS sent that batch of signals that resembled a reboot after they crossed Malaysian military space).
I just finished Jeff Wise's book, and thought the theory about someone breaching the E/E bay on MH370 was pretty compelling. Then again, there are lots of interesting theories out there.
As for the rest of your message -- I'd like the script to be as grounded in facts/reality as much possible, but my primary focus is on telling a good story. I've got a pretty good feel for the character arcs and main emotional conflicts, but the technical, aviation details are coming a bit slower as my knowledge is limited. (Unfortunately I haven't learned to fly; maybe someday, if I have a hit show and make a lot of money).
To answer your question, I don't have an agent yet. I've gotten painfully close to things working out before, so I'm giving it another good run. Hard to know if anything will come of it, but it feels good to try.
In the meantime, yes to butter on popcorn. No to coffee. (I love it, but it doesn't love me. Gives me migraines for some reason).
That's great about your scripts. Would love to hear more.
Many thanks for your time and help. Good luck with flying and writing.
Also -- I'm halfway through "FATE IS THE HUNTER." Didn't even know about that film. It's a fun watch -- thank you!
I was wondering why everyone was so convinced the transponder was turned off on MH370. But after reading your message, it seems like the conclusion is based on circumstantial evidence (i.e. because the plane continued to show up on primary radar after the transponder went dead, and ACARS sent that batch of signals that resembled a reboot after they crossed Malaysian military space).
I just finished Jeff Wise's book, and thought the theory about someone breaching the E/E bay on MH370 was pretty compelling. Then again, there are lots of interesting theories out there.
As for the rest of your message -- I'd like the script to be as grounded in facts/reality as much possible, but my primary focus is on telling a good story. I've got a pretty good feel for the character arcs and main emotional conflicts, but the technical, aviation details are coming a bit slower as my knowledge is limited. (Unfortunately I haven't learned to fly; maybe someday, if I have a hit show and make a lot of money).
To answer your question, I don't have an agent yet. I've gotten painfully close to things working out before, so I'm giving it another good run. Hard to know if anything will come of it, but it feels good to try.
In the meantime, yes to butter on popcorn. No to coffee. (I love it, but it doesn't love me. Gives me migraines for some reason).
That's great about your scripts. Would love to hear more.
Many thanks for your time and help. Good luck with flying and writing.
Also -- I'm halfway through "FATE IS THE HUNTER." Didn't even know about that film. It's a fun watch -- thank you!
As a simple isolated yes/no, on/off event - skyhighfallguy covers it. There isn't normally any way to tell (from outside the aircraft) why a transponder has ceased transmitting simply from the occurence itself. It was switched off; it failed; it was broken intentionally; something else in the equipment failed - all will give the same appearance, externally.
Except...
I do see one possibility. Transponders have multiple "on" modes. The most basic is mode "A", that responds to a radar pulse with just a 4-digit "squawk" identifying the aircraft - e.g. 4-4-1-5. Next higher is Mode C, which alongside the 4-digit number, also transmits the plane's altitude. Most complex is Mode S, which transmits additional flight information.
In some transponders, these are controlled by a multi-position rotary switch, and it is theoretically possible (but practically, real-world, unlikely) that an observer - most likely reviewing the recorded radar data after the fact, not watching events in real time - might notice that the transponder changed modes a fraction of a second at a time, from S to C to A to "standby/off" (not responding) and determines from that, that the knob was intentionally turned, rather than the transponder being destroyed all at once.
However, against that, one would have to consider that computerized radars that can read and display transponder data, also usually have a "coast" mode - if they lose a plane's transponder, the aircraft does not immediately disappear. The computer behind the "radar" screen keeps showing a symbol for the aircraft, moving it "predictively" based on the previous speed and direction and last known data, with a color change to indicate the loss of real transmissions. That might tend to "muddy" any data on mode changes just before signal loss.
But hey - no one every claimed Sherlock Homes was true to life in every detail, either.
Except...
I do see one possibility. Transponders have multiple "on" modes. The most basic is mode "A", that responds to a radar pulse with just a 4-digit "squawk" identifying the aircraft - e.g. 4-4-1-5. Next higher is Mode C, which alongside the 4-digit number, also transmits the plane's altitude. Most complex is Mode S, which transmits additional flight information.
In some transponders, these are controlled by a multi-position rotary switch, and it is theoretically possible (but practically, real-world, unlikely) that an observer - most likely reviewing the recorded radar data after the fact, not watching events in real time - might notice that the transponder changed modes a fraction of a second at a time, from S to C to A to "standby/off" (not responding) and determines from that, that the knob was intentionally turned, rather than the transponder being destroyed all at once.
However, against that, one would have to consider that computerized radars that can read and display transponder data, also usually have a "coast" mode - if they lose a plane's transponder, the aircraft does not immediately disappear. The computer behind the "radar" screen keeps showing a symbol for the aircraft, moving it "predictively" based on the previous speed and direction and last known data, with a color change to indicate the loss of real transmissions. That might tend to "muddy" any data on mode changes just before signal loss.
But hey - no one every claimed Sherlock Homes was true to life in every detail, either.
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Thanks, Pattern_Is_Full. That's super helpful. And quite clever.
I read somewhere that it takes about 3 radar sweeps for a plane to actually fall off ATC's screen. Not sure if that figured in the "coast mode." (I wonder how long the plane would change colors and be in coast mode before it vanished?)
Either way, it's great for my purposes -- a plane changing colors before vanishing is a bit more cinematic than a blip disappearing. Excellent.
Hope you get some sleep this evening -- unless you're flying, in which case maybe not a good idea.
Thanks again!
I read somewhere that it takes about 3 radar sweeps for a plane to actually fall off ATC's screen. Not sure if that figured in the "coast mode." (I wonder how long the plane would change colors and be in coast mode before it vanished?)
Either way, it's great for my purposes -- a plane changing colors before vanishing is a bit more cinematic than a blip disappearing. Excellent.
Hope you get some sleep this evening -- unless you're flying, in which case maybe not a good idea.
Thanks again!
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writergirl
I take great pride in advising one of the principal aviation analysts you might see on tv, esp during the MH370 thing so well covered (at least in time spent) on CNN.
When ""THEY"" started saying someone had turned the transponder off, I was aghast, as THEY simply do not know for sure. THEY can guess, THEY CAN CONJECTURE, but the truth is THEY do not know. Even that guy with the BRITISH ACCENT is not correct by virtue of his BRITISH ACCENT.
IF you want , you may private message me about writing. When I wrote my screenplays, a well known producer said: IT IS WELL WRITTEN but after 9 11, who wants to see a movie about planes crashing?
Let me know when you finish the movie. and maybe you will understand one of my questions.
I take great pride in advising one of the principal aviation analysts you might see on tv, esp during the MH370 thing so well covered (at least in time spent) on CNN.
When ""THEY"" started saying someone had turned the transponder off, I was aghast, as THEY simply do not know for sure. THEY can guess, THEY CAN CONJECTURE, but the truth is THEY do not know. Even that guy with the BRITISH ACCENT is not correct by virtue of his BRITISH ACCENT.
IF you want , you may private message me about writing. When I wrote my screenplays, a well known producer said: IT IS WELL WRITTEN but after 9 11, who wants to see a movie about planes crashing?
Let me know when you finish the movie. and maybe you will understand one of my questions.
Some clarification on "coast mode" and ATC radar in general.
Different jurisdictions use different symbology - so it would pay to see if you can get a visit to a nearby ATC radar facility for some guidance. Post-9/11, not as easy as it once was, but worth exploring.
The picture linked to below is from the Athens, Greece, Area Control center. They use EUROCAT symbology, and since colors are used to define which controller has responsibility for which aircraft, "coast mode" is indicated not by color, but by replacing the "A" symbol for an aircraft with a "*".
In this image, there are two aircraft (top left, green) whose signals has been lost (likely due to high terrain blocking transponder returns, rather than a failure or crash, in this case) and are indicated by the * and a missing data block - i.e. in coast. The dots show their previous radar returns (one dot per sweep of the radar) - the straight lines show their projected paths.
(Personally, if this were MY screen, I'd be a bit twitchy. I've got two aircraft in coast mode, with no data on altitude, and with intersecting projected paths. One is farther away from the crossing point, but also moving much faster (spacing between prevous returns). But that's a different script.... )
http://www.hvacc.org/site/images/con...dep_vector.jpg
Different jurisdictions use different symbology - so it would pay to see if you can get a visit to a nearby ATC radar facility for some guidance. Post-9/11, not as easy as it once was, but worth exploring.
The picture linked to below is from the Athens, Greece, Area Control center. They use EUROCAT symbology, and since colors are used to define which controller has responsibility for which aircraft, "coast mode" is indicated not by color, but by replacing the "A" symbol for an aircraft with a "*".
In this image, there are two aircraft (top left, green) whose signals has been lost (likely due to high terrain blocking transponder returns, rather than a failure or crash, in this case) and are indicated by the * and a missing data block - i.e. in coast. The dots show their previous radar returns (one dot per sweep of the radar) - the straight lines show their projected paths.
(Personally, if this were MY screen, I'd be a bit twitchy. I've got two aircraft in coast mode, with no data on altitude, and with intersecting projected paths. One is farther away from the crossing point, but also moving much faster (spacing between prevous returns). But that's a different script....
)http://www.hvacc.org/site/images/con...dep_vector.jpg
Also note that the information presented to the controller can vary significantly depending on the radar system installed.
(Controllers have to do more or less the equivalent of a type rating to 'master' the system they are working with, which is usually common within a state, but across different countries, there are many different systems.)
Some research into the system in use at the particular location you're setting the story in would be indicated.
As an example, there is a thread here concerning a middair in Brasil. (It's big. Page 31 on gives some insite.) (Some more info here )
The information presented to the controllers on their system was such that it was not immediately apparent to them that one of the aircraft had an inoperative transponder.
(Controllers have to do more or less the equivalent of a type rating to 'master' the system they are working with, which is usually common within a state, but across different countries, there are many different systems.)
Some research into the system in use at the particular location you're setting the story in would be indicated.
As an example, there is a thread here concerning a middair in Brasil. (It's big. Page 31 on gives some insite.) (Some more info here )
The information presented to the controllers on their system was such that it was not immediately apparent to them that one of the aircraft had an inoperative transponder.
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Wow, this is seriously helpful (and fascinating). Huge thanks to each of you.
Sky High - I will DM you tomorrow. I look forward to hearing about your script and picking your brain more. Thanks!
Also want to say thanks to Tarq for the link on the Brazil mid-air, and to Pattern for the sample vector. My brain is going haywire with potential scenarios now.
I wonder if a sophisticated hijacker (i.e. one backed by the Chinese, Russian, or U.S. governments, etc.) could wire up a drone that sends a decoy signal. (And yes, I realize I'm way off in left field here, even for fiction).
Under this scenario, the drone would be programmed to send a transponder signal similar to that of a particular commercial flight. Hijackers could crash the commercial flight in one place, and activate the decoy drone near the crash site. The decoy drone would leave a false breadcrumb trail, and lure searchers to another part of the ocean entirely. That way, searchers would never find the downed plane, and the disappearance would remain a mystery.
Alternatively, hijackers could use the same mechanism to make it look like the plane went in one direction, when it really went in another. Under this scenario, they might be able to take control of the plane by breaching the E/E bay, and fly it into their possession.
I presume this is probably too complicated/out-there, even for TV. Perhaps the hijackers could turn off the transponder at the designated point, and hide the plane in the shadow of a strategically-situated military craft. Meanwhile, the decoy drone could transmit signals along the planned trajectory, and make it look like the commercial flight was going as planned. It might take awhile for people on the ground to figure out the drone signal wasn't, in fact, the plane. By that point, the commercial flight would be long gone, skirting the boundaries between air spaces.
Annnnnd....that's more than enough weird conspiracy theory for one night. My brain is going off on some weird tangents. Definitely time for sleep, I think.
Thanks again for all of the help; I sincerely appreciate it. Have a good night!
Sky High - I will DM you tomorrow. I look forward to hearing about your script and picking your brain more. Thanks!
Also want to say thanks to Tarq for the link on the Brazil mid-air, and to Pattern for the sample vector. My brain is going haywire with potential scenarios now.
I wonder if a sophisticated hijacker (i.e. one backed by the Chinese, Russian, or U.S. governments, etc.) could wire up a drone that sends a decoy signal. (And yes, I realize I'm way off in left field here, even for fiction).
Under this scenario, the drone would be programmed to send a transponder signal similar to that of a particular commercial flight. Hijackers could crash the commercial flight in one place, and activate the decoy drone near the crash site. The decoy drone would leave a false breadcrumb trail, and lure searchers to another part of the ocean entirely. That way, searchers would never find the downed plane, and the disappearance would remain a mystery.
Alternatively, hijackers could use the same mechanism to make it look like the plane went in one direction, when it really went in another. Under this scenario, they might be able to take control of the plane by breaching the E/E bay, and fly it into their possession.
I presume this is probably too complicated/out-there, even for TV. Perhaps the hijackers could turn off the transponder at the designated point, and hide the plane in the shadow of a strategically-situated military craft. Meanwhile, the decoy drone could transmit signals along the planned trajectory, and make it look like the commercial flight was going as planned. It might take awhile for people on the ground to figure out the drone signal wasn't, in fact, the plane. By that point, the commercial flight would be long gone, skirting the boundaries between air spaces.
Annnnnd....that's more than enough weird conspiracy theory for one night. My brain is going off on some weird tangents. Definitely time for sleep, I think.
Thanks again for all of the help; I sincerely appreciate it. Have a good night!
