View Full Version : TCAS antenna
Maybe somebody can help me ?
We have installed TCAS II (Allied Signal) on our fleet. Is it possible to check somehow directional antenna ? For example we hade TCAS test fail & on TCAS processor was fault code which means that upper directional antenna faulty. How we can technically check the antenna condition ?
------------------
STAS
jetmech757
21st Mar 2000, 21:45
I'm sure you've tried replacing the antenna already, if not, DO IT! Is this problem on the entire fleet? Make sure the four coax cables are connected to the back of the computer and antenna correctly. They should be color-coded, too. Then get a megger and meg each wire out, (DISCONNECTED FROM EVERYTHING!!!)
If this all checks good, and you still can't find a problem, get the engineering dept. involved. I had these same problems before when I worked install many moons ago.
spannersatcx
22nd Mar 2000, 01:43
There is a couple of TCAS antenna test sets available, not sure of the ins and outs but it tests at 90/180/270/360 degs. Maybe worth getting the company to invest in one or borrow one from somewhere.
SeldomFixit
22nd Mar 2000, 02:02
Would second the post re thorough check of co-ax connex. Any tx/rx type of installation seems to suffer from hi resistance connex at some time in its life and the TCAS has been no exception in my experience. "TCAS system .......test okayyyyyyyyyyyyyyyyyyy"
growler
22nd Mar 2000, 03:12
We have had and still do have many TCAS problems on our 737 fleet (also Allied Signal). The Boe rep here tells me there are 2 systems avail on build, the good (expensive) one and the one we have.
After many antenna and processor changes, all of our problems to date have shown to be cable trouble. From badly routed cables putting strain on connections to finding connectors only slaved on and not crimped, we have seen just about everything and nothing surprises now.
Think I'll go for a job in Boeing QA coz I could do with a job where I get paid for doing nothing!!
Thank to all of you guys !
Actually all your advises was right.
Related to current problem we found that connectors of antenna was quite wet.We cleaned and dried it and now all is Ok.
But any way we have a lot of problems with TCAS and I think I`ll ask you again in the future.
I don`t know why I`m working for my company.
My workload is too heavy but salary is too small .
------------------
STAS
The hippy
22nd Mar 2000, 23:04
There is a TCAS test set, i think it is ATC601A series.
Tcas anntenna have internal amplifiers which if memory serves me right are CMOS powered an d very prone to static, inperticular the top antenna (in my experience).
make sure they are bonded correctly after that invest in a cherry picker!!!
sorry!
This for The Hippy,
I can`t catch your thought .What you mean internal amplifier ?
I have read about this antenna everything from Allied Signal manual and I found following: Directional antenna is passive device, it`s not require aircraft power.It`s electronically steerable(fromTCAS processor) phased array antenna which has four monopole elements.There is nothing about internal amplifier .
------------------
STAS
redtail
8th Apr 2000, 19:39
At my outfit we butter the connections with DC4 to keep moisture out, per da MM. There are also resistance measurements for the directional antenna, same reference.
Bus429
8th Apr 2000, 20:20
Heat gun + Scotch 33 keeps it working until you're off shift.
We had chronic problems last year with a lower antenna. Was not cured until both the antenna and feeders were replaced and the whole lot booted and smeared with PRC.
BUS429 ,
Did you replaced complete feeders , I mean from TCAS computer to antenna ?
------------------
STAS
REDTAIL,
Since we don`t have da MM , could you please explain me how to measure resistance of TCAS antenna and what are the normal figures ? Maybe you can advise me some technical publications related to this matter ?
------------------
STAS
redtail
13th Apr 2000, 17:48
I’m off for two days, but will look it up for you when I get back to the circus. A quick-and-dirty check is to order another antenna out of stock and compare the two, measured as inner conductor of each connection to outer shield. (I am at a hub, so we have the luxury of parts and airplanes). We see a lot of upper antennas go bad, usually from delamination and water rain getting in, and before we coated the connections we had a lot of corrosion problems with connectors due to condensation in the area.
When I worked at a smaller station, I used to go visit other airline’s maintenance shacks to read their manuals, since usually their tech pubs had more information than what my airline was providing us. Granted, I couldn’t print it and take it out on the ramp to use (The Friendly Aviation Advisors would have kittens if they caught me using another airlines manuals on an airplane) but still other peoples manuals could provide information that wasn’t clear in our manuals.
Sometimes the antennas come with a shop report, which will include measurements.
(P.S. I've worked line hangar for 12 years, so I've played with this system a few times. I have been chastised for referring to it as a "fish finder")
greycone
14th Apr 2000, 02:52
Another thing to look out for is enthusiastic Painters painting the Antenna.Saw it recently after a Check.Cleaned the paint off and the system worked fine.
I don't know if you should check the resistance of the Antenna.I would leave that to the Shoppie's.Smith's make a test set for checking the VSWR of line's and passive Antennae but I don't know if you would be able to check a non passive antenna with this box.
REDTAIL ,
Thanks I`m looking forward to hear from you.
If compare with your situation I live in very small country and our company is the biggest and I can say that almost sole carrier. Thats why I don`t have opportunity to use some libraries and our library is quite poor.At the same time in AMM it`s nothing about antenna checking.
------------------
STAS
Bus429
14th Apr 2000, 22:19
STAS - yes we did.
redtail
15th Apr 2000, 16:00
Here we go. We use the Honeywell/Sperry 4066010-90X series TCAS computers, with P/N 7514081-901 Directional antenna, and P/N DM1601354-001 Omni antenna (on some installations). Directional antennas can be checked: J1 - 850 to 1200 Ohms, J2 - 6500 to 9950 Ohms, J3 - 3250 to 4950 Ohms, J4 - 1650 to 2450 Ohms, all measured center conductor to shield of the antenna connector. A similiar reference had J1 - 1k +-100, J2 - 8k +-800, J3 - 4k +-400, J4 - 2k +-200. The cables should have at least 50k Ohms resistance, conductor to shield. Omni antenna should be less than 50 Ohms, conductor to shield, with examples in stores reading about 1 Ohm on my favorite Fluke.
Antennas should have 0.1 Ohm bonding to structure, and our maintenance manual calls for the connections at the antennas to be covered in Dow Corning #4 compound to prevent moisture entry.
I haven't played with the ATC601A test set, which we have at some stations, but I am familiar with the TIC-49 series. They work fairly well (with fresh batteries)for quantifying performance, and will read output wattage, frequency stability and sensitivity. I have found I have to put the antenna sleeves (or boots) over the ATC antenna's a few time to get optimun readings on Mode S, usually getting best readings when the cover is centered over the antenna. Like most test equipment, you have to play with it a bit to get comfortable with the procedure, so you can trust it.
Buy me a beer sometime.
[This message has been edited by redtail (edited 15 April 2000).]
REDTAIL,
Thanks a lot for your explanation. I`ll insert it in our AMM(joke).It`s really very usefull .
You know in Latvia(where I live) is quite good beer and I`ll buy it for you if you will visit Latvia.
If I will have any questions regarding Avionics I`ll ask you as expierenced guy.
------------------
STAS
redtail
19th Apr 2000, 03:02
STAS, no problem, just paraphrasing the manual. Initially our manuals did not give us this information, they only had information on replacing parts and testing the system. Then we noticed about two years ago that two of our aircraft types had included the antenna information in the 34-45-00 Page 100 section, even though all of our airplanes use the system. While technically we have to stick to the information given to us in the applicable manuals, being the airport rats we are and using any resource available to get the job done, we would use the antenna information from the other manuals to be sure we actually had an antenna fault (since it was a common part used on all fleets), or to find out if the TCAS computer was faulting the antenna when it actually had a cable fault. I think someone in our engineering support or technical training departments submitted the request to the technical publications department to add the information to the maintenance manuals. (A procedure slightly easier than getting the Vatican to endorse a miracle) Try to get your organization to contact the vendor for support information. Usually the vendors are interested in supplying all sorts of paperwork on their products, you just have to get around the folks who get in the way of you receiving this information.
One of the dirty secrets in our field is how little information is given to us to work with, compared to what the manufacturers and vendors will supply to the airline. Some Boeing representatives gave us a briefing class once when we started operating 747-400s, and they had a meter high stack of service bulletins and technical information. My company never processed any of that information to us on the floor level. My personal belief is that our tech pub department’s goal is to get each ATA chapter down to one page each. Sometime I am envious of auto mechanics and their manuals. Granted, they only have one engine and four brakes to be concerned with, but still we should have better manuals. Another point is that if I have a problem following a procedure in a manual, I can just imagine what it would be like for someone who does not speak english as their primary language.
I wouldn’t doubt that Latvia has good beer. American beer and food leaves a lot to be desired.
Redtail,
You right regarding the language. As you can see the English is not my native language and therefore often it`s very difficult to understand exactly what real americans talking about. But technical language not so difficult(all manuals we have on English). My native language is Russian and our state language is Latvian. So I have to speak at least three languages.
------------------
STAS