TCAS alt readout
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From: surfing, watching for sharks
TCAS alt readout
Anyone aware of tables/formulas/algorithm, etc for figuring out the delay/lag between altitude observed on a TCAS from another aircraft to its actual altitude in a climb or descent?
Simply put, I see an aircraft on my TCAS at 10,000 but climbing/descending, is there a formula published for determining the difference in altitude between what it's at and what I'm seeing on my TCAS?
Before it's pointed out to me that has no practical application for in flight use, I recognize that. The question came up while killing time on a long flight.
Simply put, I see an aircraft on my TCAS at 10,000 but climbing/descending, is there a formula published for determining the difference in altitude between what it's at and what I'm seeing on my TCAS?
Before it's pointed out to me that has no practical application for in flight use, I recognize that. The question came up while killing time on a long flight.
Only half a speed-brake
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From: Commuting not home
Did not find it yet
but tried here:
http://www.faa.gov/documentLibrary/m...%2020-151A.pdf
maybe you will be more thorough.
FD.
http://www.faa.gov/documentLibrary/m...%2020-151A.pdf
maybe you will be more thorough.
FD.
Joined: Jan 2004
Posts: 3,247
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From: Here and there
Anyone aware of tables/formulas/algorithm, etc for figuring out the delay/lag between altitude observed on a TCAS from another aircraft to its actual altitude in a climb or descent?
Simply put, I see an aircraft on my TCAS at 10,000 but climbing/descending, is there a formula published for determining the difference in altitude between what it's at and what I'm seeing on my TCAS?
Before it's pointed out to me that has no practical application for in flight use, I recognize that. The question came up while killing time on a long flight.
Simply put, I see an aircraft on my TCAS at 10,000 but climbing/descending, is there a formula published for determining the difference in altitude between what it's at and what I'm seeing on my TCAS?
Before it's pointed out to me that has no practical application for in flight use, I recognize that. The question came up while killing time on a long flight.
Joined: Feb 2000
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From: Alaska, PNG, etc.
Anyone aware of tables/formulas/algorithm, etc for figuring out the delay/lag between altitude observed on a TCAS from another aircraft to its actual altitude in a climb or descent?
Simply put, I see an aircraft on my TCAS at 10,000 but climbing/descending, is there a formula published for determining the difference in altitude between what it's at and what I'm seeing on my TCAS?
Before it's pointed out to me that has no practical application for in flight use, I recognize that. The question came up while killing time on a long flight.
Simply put, I see an aircraft on my TCAS at 10,000 but climbing/descending, is there a formula published for determining the difference in altitude between what it's at and what I'm seeing on my TCAS?
Before it's pointed out to me that has no practical application for in flight use, I recognize that. The question came up while killing time on a long flight.
That formula will give you the altitude of the other aircraft at any moment. The difficulty is determining the value of those variables.
Thread Starter
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From: surfing, watching for sharks
Yes: Reported altitude + Climb rate X ( Transmitting Transponder system latency + Radio propagation delay + Receiving TCAS system latency)
That formula will give you the altitude of the other aircraft at any moment. The difficulty is determining the value of those variables.
That formula will give you the altitude of the other aircraft at any moment. The difficulty is determining the value of those variables.
Thread Starter
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From: surfing, watching for sharks
Joined: Mar 2008
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From: Malvern, UK
Quote:
Originally Posted by A Squared View Post
Yes: Reported altitude + Climb rate X ( Transmitting Transponder system latency + Radio propagation delay + Receiving TCAS system latency)
That formula will give you the altitude of the other aircraft at any moment. The difficulty is determining the value of those variables.
Originally Posted by A Squared View Post
Yes: Reported altitude + Climb rate X ( Transmitting Transponder system latency + Radio propagation delay + Receiving TCAS system latency)
That formula will give you the altitude of the other aircraft at any moment. The difficulty is determining the value of those variables.
Radio propagation delay <1millisecond
Receiving TCAS system latency [the display works on a 1s refresh so that is the maximum latency]
So potentially the height data is maximum 1101milliseconds old.
At 5000ft per minute that's around 92ft as a maximum. But as an average probably much less.
This is simply for the display of course. The internal tracking algorithms of the TCAS unit are not constrained to the 1s refresh rate.
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From: Here and there
Transmitting Transponder system latency < 100 milliseconds (mainly the refresh rate of the altitude from the air data computer. The internal interrogation / reply processing of the Transponder will be small in comparison)
Radio propagation delay <1millisecond
Receiving TCAS system latency [the display works on a 1s refresh so that is the maximum latency]
So potentially the height data is maximum 1101milliseconds old.
At 5000ft per minute that's around 92ft as a maximum. But as an average probably much less.
This is simply for the display of course. The internal tracking algorithms of the TCAS unit are not constrained to the 1s refresh rate.
Radio propagation delay <1millisecond
Receiving TCAS system latency [the display works on a 1s refresh so that is the maximum latency]
So potentially the height data is maximum 1101milliseconds old.
At 5000ft per minute that's around 92ft as a maximum. But as an average probably much less.
This is simply for the display of course. The internal tracking algorithms of the TCAS unit are not constrained to the 1s refresh rate.
Joined: Mar 2008
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From: Malvern, UK
Well, I would wonder about that latency, given the latency in the GPS position.
Altitude is barometric.
Range and range rate are calculated from interrogation pings.
Direction is highly approximate and for pilot situational awareness only.
Depending on the system, they handle they track and handle the threats differently, hence, there is a proprietary factor as well.
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From: nowhere
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From: Malvern, UK
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From: PA
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