Tcas question
Joined: Apr 2008
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From: Somewhere
Sorry, I actually meant aircraft type. The ADIRU(s) and associated interface with the TCAS Computer will be dependant on the type of aircraft.
Without knowing which type(s) of aircraft it's difficult to answer.
I would hazard a guess however, that the TCAS Computer is set-up in such a way that it receives inputs from ADIRU #1 and thus if ADIRU #1 was to fail, the TCAS would also fail.
Without knowing which type(s) of aircraft it's difficult to answer.
I would hazard a guess however, that the TCAS Computer is set-up in such a way that it receives inputs from ADIRU #1 and thus if ADIRU #1 was to fail, the TCAS would also fail.
Joined: Apr 2008
Posts: 147
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From: Somewhere
The type is irrelevant
I disagree. Not all aircraft that are fitted with TCAS have an Inertial Reference System.
Also, I imagine, although I don't have any data to hand, that the set-up of a Boeing's Avionics and an Airbus' are miles apart and where TCAS takes the inputs from will differ.
It would seem from the post above regarding the A320, that TCAS takes inputs from ADIRU #1. It would be interesting to know if there is any redundancy where TCAS is concerned. I.e. If ADIRU #1 fails, is the system capable of supplying data to the TCAS Computer from another ADIRU?
If not, then as I said in my previous post, the TCAS system will fail.
Thread Starter
Joined: Dec 2007
Posts: 256
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From: Over the clouds
Thanks MIN-JUMBO.
Everything you said is correct.
The second part of the question is “Does all the TCAS II needs hdg pitch and roll inputs?”
Pitch, makes sense to me, because when you are in an RA, the pitch input is used to know your vertical status, and compare it with the ROC/ROD proposed to solve the situation. Therefore you can receive a “Climb/Descend”, “Increase rate of descend/climb”, etc. msg.
Hdg and roll seems to be useful in order to know if there is a real risk of collision. In other words, TCAS must know where are you flying to calculate which of the traffics around you, are potential risks.
Not only that. If the IRU doesn’t work then it makes sense that it can not be displayed anything because PFD and ND associated are not working, as far as you don’t change the source of information (IRU).
The source for the hdg, pitch and roll, can vary between ADIRU, HSI, ADC, etc. It is not important to the question till here.
But now going into Airbus and ADIRUs. A318/A319/A320/A321 ATA 3.02.34 page 7. A330/A340 same ATA, page 4A or 5. Abnormal Procedures-Navigation-NAV IR FAULT. There is a note saying “In case of an IR1 fault, the TCAS may be inoperative, depending on the TCAS manufacturer”
In case it were only be affected the RA it should concrete on that fail, but it says all the TCAS and that includes also the traffics display and the TA.
Do that means that many of the TCAS needs hdg, pitch and roll to calculate the position of the traffics?
I thought that position was calculated by means of time of the radio signal to return-àdistance, mode c altitude report-àvertical separation, and directional sensing antenna-à bearing. Then you could have at least the presentation of the sensed traffics in case of not hdg, pitch and roll inputs
ADMIRAL, sorry if I
was not clear enough.
Tailwinds
Everything you said is correct.
The second part of the question is “Does all the TCAS II needs hdg pitch and roll inputs?”
Pitch, makes sense to me, because when you are in an RA, the pitch input is used to know your vertical status, and compare it with the ROC/ROD proposed to solve the situation. Therefore you can receive a “Climb/Descend”, “Increase rate of descend/climb”, etc. msg.
Hdg and roll seems to be useful in order to know if there is a real risk of collision. In other words, TCAS must know where are you flying to calculate which of the traffics around you, are potential risks.
Not only that. If the IRU doesn’t work then it makes sense that it can not be displayed anything because PFD and ND associated are not working, as far as you don’t change the source of information (IRU).
The source for the hdg, pitch and roll, can vary between ADIRU, HSI, ADC, etc. It is not important to the question till here.
But now going into Airbus and ADIRUs. A318/A319/A320/A321 ATA 3.02.34 page 7. A330/A340 same ATA, page 4A or 5. Abnormal Procedures-Navigation-NAV IR FAULT. There is a note saying “In case of an IR1 fault, the TCAS may be inoperative, depending on the TCAS manufacturer”
In case it were only be affected the RA it should concrete on that fail, but it says all the TCAS and that includes also the traffics display and the TA.
Do that means that many of the TCAS needs hdg, pitch and roll to calculate the position of the traffics?
I thought that position was calculated by means of time of the radio signal to return-àdistance, mode c altitude report-àvertical separation, and directional sensing antenna-à bearing. Then you could have at least the presentation of the sensed traffics in case of not hdg, pitch and roll inputs
ADMIRAL, sorry if I
was not clear enough.Tailwinds
Joined: Feb 2001
Posts: 461
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From: UK
737NG ADIRU supplies pitch/roll attitude and mag heading to the TCAS processor, but it is not currently used.
757/767 IRU's supply mag heading, and again it's not used.
I can only assume the TCAS processor is programmed to look for this data, and if missing, will fail itself.
757/767 IRU's supply mag heading, and again it's not used.
I can only assume the TCAS processor is programmed to look for this data, and if missing, will fail itself.
Thread Starter
Joined: Dec 2007
Posts: 256
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From: Over the clouds
I found this
http://www.halldale.com/Assets/Files...dowski%202.pdf
It is not the answer, but a good aproximation.
Edit to say:
Oooops
The correct link is this:
http://www.eurocontrol.int/msa/gallery/content/public/documents/ACAS_training_ver20.pdf
The first is interesting like this other one:
http://www.eurocontrol.int/msa/public/standard_page/ACAS_Overview.html
ppp
http://www.halldale.com/Assets/Files...dowski%202.pdf
It is not the answer, but a good aproximation.
Edit to say:
Oooops
The correct link is this:
http://www.eurocontrol.int/msa/gallery/content/public/documents/ACAS_training_ver20.pdf
The first is interesting like this other one:
http://www.eurocontrol.int/msa/public/standard_page/ACAS_Overview.html
ppp
Last edited by ppppilot; 14th April 2008 at 18:41.
