Moderators: richierich, ua900, PanAm_DC10, hOMSaR

 
User avatar
HAWK21M
Topic Author
Posts: 30130
Joined: Fri Jan 05, 2001 10:05 pm

Tcas / Acas

Mon Aug 06, 2001 7:01 pm

Is it the same thing.
ie TCAS & ACAS.
If not whats the difference.
regds
HAWK.
I may not win often, but I damn well never lose!!! ;)
 
modesto2
Posts: 2731
Joined: Sun Jul 16, 2000 3:44 am

RE: Tcas / Acas

Mon Aug 06, 2001 11:40 pm

HAWK21M, not sure what you're talking about. I know of TCAS and ACARS but not ACAS. If that sounds right, I can elaborate.
 
OO-AOG
Posts: 1395
Joined: Mon Dec 11, 2000 1:24 am

RE: Tcas / Acas

Tue Aug 07, 2001 12:37 am

I think, but not sure, that a TCAS is a more sophisticated ACAS. TCAS gives heading, distance and altitude of the traffic while ACAS gives only a warning.
Again I'm not sure and would be curious to see if I'm not completly wrong on that one.

Cheers
OO-AOG
Falcon....like a limo but with wings
 
cdfmxtech
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: Tcas / Acas

Tue Aug 07, 2001 4:22 am

ACAS - Airborne Collision Avoidance System
An ugraded TCAS II System (upgraded software).
 
Guest

RE: Tcas / Acas

Wed Aug 08, 2001 3:21 am

Actually the two terms TCAS and ACAS are identical in the technical sense. TCAS is used by the US (e.g. by Boeing and those who like it) and ACAS is the term used in Europe (e.g. by Airbus and those who like it).

Regards,
Nut
 
User avatar
HAWK21M
Topic Author
Posts: 30130
Joined: Fri Jan 05, 2001 10:05 pm

RE: Tcas / Acas

Wed Aug 08, 2001 5:44 pm

Makes sense Now.
Thanks.
regds
HAWK.
I may not win often, but I damn well never lose!!! ;)
 
cdfmxtech
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: Tcas / Acas

Wed Aug 08, 2001 6:10 pm

Well...check out Honeywells site and they make it seem as if ACAS is an upgrade.
 
Guest

RE: Tcas / Acas

Thu Aug 09, 2001 3:07 am

The Honeywell site says:
"Honeywell introduces the next generation of Collision Avoidance technology, the new Enhanced ACAS II (Airborne Collision Avoidance System) and Mode S System. ACAS II is TCAS II with additional software called Change 7, which is the basis for the worldwide requirement... enhanced because our new system goes beyond just Change 7."

They are talking about their ENHANCED ACAS II. TCAS and ACAS have been used interchangeably for sometime, as far I can remember. Keep in mind this is the Allied Signal TCAS/ACAS. The original Honeywell TCAS (in a great number of airliners) is now owned by L3 and is the L3 system now.

Regards,
Nut
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: Tcas / Acas

Thu Aug 09, 2001 3:25 am

The term ACAS was originally used by Eurocontrol which is the "European Organisation for the Safety of Air Navigation". The term stands for "Airborne Collision Avoidance Systems" as opposed to TCAS which stands for "Traffic Collision Avoidance System". The FAA chose to adopt the TCAS term in the beginning.

You can check out the definition of ACAS at this site:

http://www.eurocontrol.fr/ba_saf/acas/

Eurocontrol defined the operational and performance specifications of ACAS I, ACAS II and ACAS III and then further mandated the use of it (depending on aircraft type and operation) in European aerospace some time earlier this year.

At the time the specification was defined, there were no existing systems which met the specification. All of the existing TCAS II systems with MOPS (minimum operating and performance specification) 6.04 fell short.

The answer was to introduce MOPS 7.0 software. Therefore TCAS II with the so-called "Change 7" met the Eurocontrol ACAS II specification. Many airlines were scrambling late last year to modify their units to meet the new specification. There will be another rush soon to meet the new Mode S Transponder MOPS.

Honeywell decided to add a few extra improvments and introduce the new TCAS II system as "Enhanced ACAS". This is primarily a marketing ploy but it does show that the FAA world is slowly adopting the ACAS term to describe the systems.



 
737LAME
Posts: 75
Joined: Sat Apr 07, 2001 3:14 pm

RE: Tcas / Acas

Fri Aug 10, 2001 10:04 pm

TCAS II use software 6.04
ACAS use software 7.

In terms of use they are the same, It is inside the box, or software that is different.

And it is correct that it was the JAA that was the forerunner for the ACAS.

In terms of an engineers perspective there are a few other settings in the ACAS software, the computer checks the antenna impedance for the omnidirectiona upper and lower antenna. And in the software for the ACAS the fault reporting limit is substansially lower than on the TCAS software. So there has been a few upper antenna changes due to this problem (gives antenna fault on bite)
Upper antenna is also used in 80% of the time the TCAS/ACAS is in use.

Atle
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: Tcas / Acas

Sat Aug 11, 2001 1:36 pm

737LAME,

When you say "In terms of an engineers perspective" do you mean an aeronautical engineer or a maintenance engineer? Please don't consider this request a challenge (as often happens). I just want to understand your perspective.

I'd like to provide some clarification for your comments.

In terms of use, ACAS II and TCAS II (prior to change 7) are not the same. Some of the callouts have been changed. An upgrade to Change 7 requires changes to the Flight Manual in most cases to provide the flightcrew with the new callouts.

Your statement "the computer checks the antenna impedance for the omnidirectiona upper and lower antenna" implies that both the upper and lower TCAS/ACAS antennas are omni-directional. This is not true. TCAS/ACAS systems utilize either an upper and lower "directional" antenna or an upper directional and a lower omnidirectional (monopole) antenna, but never an upper omnidirectional antenna. It would make the system fairly useless as all of the RAs and TAs would lack relative bearing information.

When an aircraft is fitted with an upper and lower directional antenna, the lower one is placed in an "omnidirectional" mode when the landing gear is down. This reduces the chances of an erroneous traffic bearing due to reflections from the landing gear. Traffic signals received from "omni" antennas produce a "no bearing" traffic alert or display.

I have one more suggestion. I've been involved in curing upper antenna failures on some aircraft (757 especially). Water ingestion starts the problem, usually caused by bad or neglected antenna sealing and/or condensation. The coaxial connectors become worn fairly quickly on the line following antenna troubleshooting because maintainers seem to love to use pliers on them when finger power is all that should be needed and then use oversized probes to do continuity checks. Eventually the connectors on the antenna fail to connect properly and the antenna is garbage.

Installing an antenna disconnect near the antenna can faciliate maintenance without damaging the antenna. Make the connection close enough to the antenna that personell will notice it when accessing the unit.

P.S. Make sure you get the modification approved!


 
737LAME
Posts: 75
Joined: Sat Apr 07, 2001 3:14 pm

Thanks Airplay

Mon Aug 13, 2001 12:17 am

Hi Airplay

Thanks for correcting me. You are absolutely correct.

When I say from an engineers perspective I am talking about an maintenance engineer, my own experience.

I have also experienced the problems with the bad sealant and moisture ingress, or bad mounting of the antenna.Not by the manuals!

Most of the problems with the ACAS has been software/box hardware related though. But this is been taken care of by the manufaturers. So the system gets more and more reliable.

Atle
 
cricri
Posts: 540
Joined: Sat Oct 02, 1999 12:10 am

Tcas / Acas : Do They Communicate?

Mon Aug 13, 2001 8:02 pm

Do the TCAS systems communicate each others from one plane to another? Like one is given a "climb" command while the other gets a "descent one? thinking of near misses examples... I heard a few years ago that this communication among planes system was not really good and that two planes with their routes facing had the same command...
 
User avatar
HAWK21M
Topic Author
Posts: 30130
Joined: Fri Jan 05, 2001 10:05 pm

RE: Tcas / Acas

Thu Aug 23, 2001 9:39 am

I may not win often, but I damn well never lose!!! ;)

Who is online

Users browsing this forum: Flow2706 and 1 guest

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos