TCAS and MEL
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TCAS and MEL
I am a military transport pilot and for many years we have been operating around the world with a state exemption from the mandatory ACASII requirements. In the last 2 or 3 years our fleet has been fitted with TCAS to meet the ECAC agreemnt that Military Transport Type Aircraft (MTTA) would be fitted with ACAS. I believe that this was also precipitated by the German authorites removal of TCAS exemption as of January 1 2005. We are now faced with a confusing mixture of exempt/not exempt regulations.
My questions are:
1. What do commercial operators MELs generally say about TCAS?
2. Is TCAS a no-go item?
3. Does your MEL specify no-entry into certain countries/airspace? (ie aircraft not to be used for certain routes)
4. Would you return to stand for a TCAS failure on the ground?
5. If TCAS failed in flight would you return for rectification rather than enter for example NAT MNPS airspace where it specified as mandatory?
6. Can you continue operating with a TCAS failure for a certain period of time before rectification? (ie a specified no of sectors/flying hours)
Any info/advice spefic or general is appreciated.
Many Thanks.
My questions are:
1. What do commercial operators MELs generally say about TCAS?
2. Is TCAS a no-go item?
3. Does your MEL specify no-entry into certain countries/airspace? (ie aircraft not to be used for certain routes)
4. Would you return to stand for a TCAS failure on the ground?
5. If TCAS failed in flight would you return for rectification rather than enter for example NAT MNPS airspace where it specified as mandatory?
6. Can you continue operating with a TCAS failure for a certain period of time before rectification? (ie a specified no of sectors/flying hours)
Any info/advice spefic or general is appreciated.
Many Thanks.
Last edited by Tenlavs; 23rd Nov 2006 at 17:06.
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Ok, will have a go at these. No authority on the subject, but in possesion of our MEL/DDPG 
1), 2) and 6) It is generally found in the MEL with rectification interval C i.e. 10 days excluding the day the failure was discovered. Know that this C-status is under rewiev from EASA, but hard to proedict if any changes are afoot.
3) We must always consult with our route documentation to see if the states whose airspace we use have differences posted to ICAO standards regarding ACAS. Have not (yet) found any EUR region states where it's a problem.
4) Depends on when your rules state that your MEL stops taking effect and your QRH does. Doors closed? Park brake released? Taxi under own power? Thrust being advanced for takeoff? And even if you are into QRH territory - can you effect MEL release at your destination? If not, a return to gate might be better. However, most commercial operators test ACAS well before doors close, and with flt/gnd-logic inhibiting ACAS functions on ground, you might not find out until airborne.
5) Depends on how much fuel you have on board - can you accept/are you allowed routing below MNPS or RVSM areas?
Hope this helps
Empty
1), 2) and 6) It is generally found in the MEL with rectification interval C i.e. 10 days excluding the day the failure was discovered. Know that this C-status is under rewiev from EASA, but hard to proedict if any changes are afoot.
3) We must always consult with our route documentation to see if the states whose airspace we use have differences posted to ICAO standards regarding ACAS. Have not (yet) found any EUR region states where it's a problem.
4) Depends on when your rules state that your MEL stops taking effect and your QRH does. Doors closed? Park brake released? Taxi under own power? Thrust being advanced for takeoff? And even if you are into QRH territory - can you effect MEL release at your destination? If not, a return to gate might be better. However, most commercial operators test ACAS well before doors close, and with flt/gnd-logic inhibiting ACAS functions on ground, you might not find out until airborne.
5) Depends on how much fuel you have on board - can you accept/are you allowed routing below MNPS or RVSM areas?
Hope this helps
Empty
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Empty Cruise - Thanks, that's interestng and useful.
The Eurocontrol website explains the mandatory nature of ACAS implementation for Phase 1/Phase 2 and also explains how exemptions for delivery and maintenance flights can be applied for:
http://www.eurocontrol.int/msa/publi...xemptions.html
I read this as saying that special clearance for a flight without ACAS must be obtained and it cannot be a revenue flight. If so how can an airliner be dispatched without a functioning TCAS? Please forgive my ignorance , I am unfamilar with the concept of Interval C. I am guessing that various equpment falls into different categories with an allowable time for deferral of rectification? Is that an operator, manufacturer or regulatory decision?
We have particular problem as our TCAS installation is proving unreliable and we are trying to decide how far the "military exemption" still applies. Our equivalent of MEL differs slightly in concept as it has to cater for "operational" circumstances.
The Eurocontrol website explains the mandatory nature of ACAS implementation for Phase 1/Phase 2 and also explains how exemptions for delivery and maintenance flights can be applied for:
http://www.eurocontrol.int/msa/publi...xemptions.html
I read this as saying that special clearance for a flight without ACAS must be obtained and it cannot be a revenue flight. If so how can an airliner be dispatched without a functioning TCAS? Please forgive my ignorance , I am unfamilar with the concept of Interval C. I am guessing that various equpment falls into different categories with an allowable time for deferral of rectification? Is that an operator, manufacturer or regulatory decision?
We have particular problem as our TCAS installation is proving unreliable and we are trying to decide how far the "military exemption" still applies. Our equivalent of MEL differs slightly in concept as it has to cater for "operational" circumstances.
Last edited by Tenlavs; 24th Nov 2006 at 12:05.
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It's been a while but I always thought that one of the differences between Euro and N.Amer RVSM airspace was that, in Europe, revenue flights without functioning TCAS could be accomodated in RVSM airspace, provided traffic is such that ATC can apply larger separations for you. In North America, airliners with no TCAS = no RVSM. They can dispatch though as long as they stay below FL 290.
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I will try to answer based on my company's procedures.
1. What do commercial operators MELs generally say about TCAS?
2. Is TCAS a no-go item?
-- No it is not a no-go item. But if TCAS is found to be inop, it has to be deactivated/secured before flight and the ensuing enroute and approach procedures in-flight do not require its usage because if TCAS is inop, TAWS is unavailable as well.
3. Does your MEL specify no-entry into certain countries/airspace? (ie aircraft not to be used for certain routes)
-- It doesn't, to my understanding. For RVSM we need only 2 primary altitude measurement systems, 1 automatic altitude-control system and 1 altitude-alerting device as minimum standard equipments. While TCAS is not a requirement as yet for RVSM where I fly, if we have it, only TCAS II with version 6.04 (version 7.0 is recommended) and above is allowed.
4. Would you return to stand for a TCAS failure on the ground?
-- Depends on the flight profile as explained in 1 and 2. QRH is in force.
5. If TCAS failed in flight would you return for rectification rather than enter for example NAT MNPS airspace where it specified as mandatory?
-- No. We'd try get exemption in-flight for enhanced separation or fly lower if need be.
6. Can you continue operating with a TCAS failure for a certain period of time before rectification? (ie a specified no of sectors/flying hours)
-- In my company this type of failure is in category B . It has to be rectified within 6 consecutive days excluding day of discovery.
To expand further since you are interested, rectification intervals in my company fall into 4 categories. Category A has no specified interval but it has to be recitified within the conditions stated in the remarks column of the MEL itself (if any). Cateogry B is within 6 days, Category C 20 days and Category D 120 days. All days exclude the day of discovery.
1. What do commercial operators MELs generally say about TCAS?
2. Is TCAS a no-go item?
-- No it is not a no-go item. But if TCAS is found to be inop, it has to be deactivated/secured before flight and the ensuing enroute and approach procedures in-flight do not require its usage because if TCAS is inop, TAWS is unavailable as well.
3. Does your MEL specify no-entry into certain countries/airspace? (ie aircraft not to be used for certain routes)
-- It doesn't, to my understanding. For RVSM we need only 2 primary altitude measurement systems, 1 automatic altitude-control system and 1 altitude-alerting device as minimum standard equipments. While TCAS is not a requirement as yet for RVSM where I fly, if we have it, only TCAS II with version 6.04 (version 7.0 is recommended) and above is allowed.
4. Would you return to stand for a TCAS failure on the ground?
-- Depends on the flight profile as explained in 1 and 2. QRH is in force.
5. If TCAS failed in flight would you return for rectification rather than enter for example NAT MNPS airspace where it specified as mandatory?
-- No. We'd try get exemption in-flight for enhanced separation or fly lower if need be.
6. Can you continue operating with a TCAS failure for a certain period of time before rectification? (ie a specified no of sectors/flying hours)
-- In my company this type of failure is in category B . It has to be rectified within 6 consecutive days excluding day of discovery.
To expand further since you are interested, rectification intervals in my company fall into 4 categories. Category A has no specified interval but it has to be recitified within the conditions stated in the remarks column of the MEL itself (if any). Cateogry B is within 6 days, Category C 20 days and Category D 120 days. All days exclude the day of discovery.
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Interesting differences, we have the same 4 categories, however the times until the item in question has to be fixed are different, B is 3 days and C is 10 days, A and D are the same as above. Oh, and our MEL is valid until we "commence takeoff roll".
TCAS is an A item for us with a time to repair of 3 calendar days if operating in airspace that requires TCAS (for example airspace of ECAC states). It used to be a C item but was changed last year. However if only the RA display system or the TA display system is inoperative it is a C item.
TCAS is an A item for us with a time to repair of 3 calendar days if operating in airspace that requires TCAS (for example airspace of ECAC states). It used to be a C item but was changed last year. However if only the RA display system or the TA display system is inoperative it is a C item.
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As I understand, it seems that your companies allow you to operate for varying periods without a serviceable TCAS. However, the Eurocontrol regulations seem quite clear that exemptions can be obtained but only for delivery/maintenance and not for revenue:
http://www.eurocontrol.int/msa/publi...xemptions.html
I don't understand how you can take-off with passengers without TCAS. Am I interpreting these regulations wrongly?
Chrome, For years we had RVSM but no TCAS. Flight without TCAS does not require greater seperation or lower levels. We operated with a TCAS exemption and this had no effect on RVSM status. I understand that TCAS in RVSM must be V6.04 or better, as older versions gave a 1250ft RA protection which RVSM traffic would trigger.
Note: Flights operated under the provisions of this ACAS II exemption must be non-revenue flights.
I don't understand how you can take-off with passengers without TCAS. Am I interpreting these regulations wrongly?
Chrome, For years we had RVSM but no TCAS. Flight without TCAS does not require greater seperation or lower levels. We operated with a TCAS exemption and this had no effect on RVSM status. I understand that TCAS in RVSM must be V6.04 or better, as older versions gave a 1250ft RA protection which RVSM traffic would trigger.
I picked up the document below off the web in late 2003 when TCAS was being fitted to the VC10. At least one of our frames didn't meet the deadline of 1 Jan 2005.
As a general rule of thumb: no TCAS = not allowed in RVSM. Unless the aircraft is being delivered, or a trip to a destination for rectification, then it shoudn't be up there.
Slightly off topic but important neverthelss - as I recall, if you are part of a military formation, some ATC centres in Europe will insist that you have 2000 ft vertical clearance from other traffic (as opposed to RVSM 1000 ft). That could result in some ****ty levels/routing if you're not expecting it!
INFORMATION FOR MILITARY OPERATORS, ON ACAS POLICY AND IMPLEMENTATION WITHIN THE AIRSPACE OF THE ECAC STATES
The carriage and operation of ACAS II (TCAS II Version 7 equipment) is mandated in the entire airspace of the ECAC States for all civil turbine-engined aircraft having a maximum certificated take-off mass of more than 15000kg, or maximum approved passenger seating configuration of more than 30 (Phase 1).
Furthermore, the carriage and operation of ACAS II will be mandatory from 1 Jan 2005for all civil turbine-engined aircraft having a maximum ertificated take-off mass of more than 5700kg, or maximum approved passenger seating configuration of more than 19 (Phase 2).
State aircraft are currently exempt from this mandate for the carriage and operation of ACAS II. However, most European military authorities have committed voluntarily to fitting ACAS II, by 1 Jan 2005, to those State transport type aircraft which meet the Phase 1 criteria, and which, had they been civil, would have been required to fit ACAS II.
If an aircraft is civil-registered, but operating under contract to the military, then the civil ACAS II mandate provisions will apply. The category ‘transport-type military aircraft’ is considered to include, additionally, tanker aircraft and may well include other large-sized aircraft. It is not intended that ACAS II equipment is fitted to fast-jet aircraft.
One ECAC State, Germany, has made ACAS II mandatory within its airspace, from 1 Jan 2000, for all aircraft whether civil or military, which meet the Phase 1 criteria, and from 1 Jan 2005 for all aircraft whether civil or military which meet the Phase 2 criteria. Nevertheless, Germany recognises that the European 'norm' for carriage of ACAS II by military aircraft is currently a voluntary commitment to be met by 1 Jan 2005. Therefore, until 1 Jan 2005, Germany will permit 'guest air forces' to operate in German airspace without ACAS II, and without the need to apply for an exemption. However, with effect from 1 Jan 2005, all aircraft, whether civil or military, which meet the Phase 1 or Phase 2 criteria are required to carry and operate ACAS II within its airspace.
Clearly, States are encouraged to fit their military transport-type aircraft with TCAS II Version 7, which is ACAS II SARPs compliant, as soon as possible and by 1 Jan 2005 at the latest. Meanwhile, should TCAS II Version 6.04A be fitted, then its operation will continue to provide a significant safety benefit. This is also the case for Version 6.04A operation within RVSM airspace, even though extra Resolution Advisories (RAs) and a large number of nuisance Traffic Advisories (TAs) would be generated. (Please note that there is no direct link between the requirements for ACAS II and RVSM certification requirements for EUR RVSM airspace. So the installation of TCAS II Version 7 is not required for RVSM certification.).
Military operators who wish to register aircraft which meet the Phase 1 requirements and which periodically operate within the airspace of the ECAC States, may do so with the Eurocontrol ACAS Support Unit (ASU). Contact should be made with the ASU either by fax (+32-2-729-3719) or email ([email protected]).
Military operators are requested to make the ASU aware of any ACAS II fitment plans they might have.
As a general rule of thumb: no TCAS = not allowed in RVSM. Unless the aircraft is being delivered, or a trip to a destination for rectification, then it shoudn't be up there.
Slightly off topic but important neverthelss - as I recall, if you are part of a military formation, some ATC centres in Europe will insist that you have 2000 ft vertical clearance from other traffic (as opposed to RVSM 1000 ft). That could result in some ****ty levels/routing if you're not expecting it!
INFORMATION FOR MILITARY OPERATORS, ON ACAS POLICY AND IMPLEMENTATION WITHIN THE AIRSPACE OF THE ECAC STATES
The carriage and operation of ACAS II (TCAS II Version 7 equipment) is mandated in the entire airspace of the ECAC States for all civil turbine-engined aircraft having a maximum certificated take-off mass of more than 15000kg, or maximum approved passenger seating configuration of more than 30 (Phase 1).
Furthermore, the carriage and operation of ACAS II will be mandatory from 1 Jan 2005for all civil turbine-engined aircraft having a maximum ertificated take-off mass of more than 5700kg, or maximum approved passenger seating configuration of more than 19 (Phase 2).
State aircraft are currently exempt from this mandate for the carriage and operation of ACAS II. However, most European military authorities have committed voluntarily to fitting ACAS II, by 1 Jan 2005, to those State transport type aircraft which meet the Phase 1 criteria, and which, had they been civil, would have been required to fit ACAS II.
If an aircraft is civil-registered, but operating under contract to the military, then the civil ACAS II mandate provisions will apply. The category ‘transport-type military aircraft’ is considered to include, additionally, tanker aircraft and may well include other large-sized aircraft. It is not intended that ACAS II equipment is fitted to fast-jet aircraft.
One ECAC State, Germany, has made ACAS II mandatory within its airspace, from 1 Jan 2000, for all aircraft whether civil or military, which meet the Phase 1 criteria, and from 1 Jan 2005 for all aircraft whether civil or military which meet the Phase 2 criteria. Nevertheless, Germany recognises that the European 'norm' for carriage of ACAS II by military aircraft is currently a voluntary commitment to be met by 1 Jan 2005. Therefore, until 1 Jan 2005, Germany will permit 'guest air forces' to operate in German airspace without ACAS II, and without the need to apply for an exemption. However, with effect from 1 Jan 2005, all aircraft, whether civil or military, which meet the Phase 1 or Phase 2 criteria are required to carry and operate ACAS II within its airspace.
Clearly, States are encouraged to fit their military transport-type aircraft with TCAS II Version 7, which is ACAS II SARPs compliant, as soon as possible and by 1 Jan 2005 at the latest. Meanwhile, should TCAS II Version 6.04A be fitted, then its operation will continue to provide a significant safety benefit. This is also the case for Version 6.04A operation within RVSM airspace, even though extra Resolution Advisories (RAs) and a large number of nuisance Traffic Advisories (TAs) would be generated. (Please note that there is no direct link between the requirements for ACAS II and RVSM certification requirements for EUR RVSM airspace. So the installation of TCAS II Version 7 is not required for RVSM certification.).
Military operators who wish to register aircraft which meet the Phase 1 requirements and which periodically operate within the airspace of the ECAC States, may do so with the Eurocontrol ACAS Support Unit (ASU). Contact should be made with the ASU either by fax (+32-2-729-3719) or email ([email protected]).
Military operators are requested to make the ASU aware of any ACAS II fitment plans they might have.
Last edited by MrBernoulli; 25th Nov 2006 at 10:24. Reason: Formatting
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Not really what you are after but anyway.
Are you using the Honeywell TPU 67A system and are the failures usually at power up rather than during flight?
A software mod has cleared up the majority of the failures we were getting.
The failure was caused by excessive returns at power up. Operating in the London area meant regular failures.
If you are using this system look for a small white sticker on the TCAS processor that says SW 11/05 (software) if 11/04 Honeywell should mod it free of charge!
Are you using the Honeywell TPU 67A system and are the failures usually at power up rather than during flight?
A software mod has cleared up the majority of the failures we were getting.
The failure was caused by excessive returns at power up. Operating in the London area meant regular failures.
If you are using this system look for a small white sticker on the TCAS processor that says SW 11/05 (software) if 11/04 Honeywell should mod it free of charge!
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Tenlavs, dont confuse exemptions from operation according MEL. Those are quite different. There is a document regarding ACAS operation according MEL on the same site your quoting the exemption rules from, check out http://www.eurocontrol.int/msa/galle.../MELUpdate.doc, it quotes the same time to repair as we did above, ie 10 days in all ECAC states except germany and switzerland which restrict it to 3 days.
Although airspaces that require ACAS usage coincide with airspaces that require RVSM approval ACAS is not a requirement for RVSM, so
is just that, a rule of thumb, but not a RVSM requirement.
Although airspaces that require ACAS usage coincide with airspaces that require RVSM approval ACAS is not a requirement for RVSM, so
As a general rule of thumb: no TCAS = not allowed in RVSM. Unless the aircraft is being delivered, or a trip to a destination for rectification, then it shoudn't be up there.
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Thanks everyone.
Denti - you are quite right. I have no first hand experience of working with a MEL and was confusing exemptions with MEL relief. I have now seen the reference that you posted and it all becomes a little clearer -thanks.
Does anyone know if the lower 3 day limit apply to all aircraft flying through Germany/Switzerland or just to aircaft registered in those states? I notice that the FAA requiremnt is also 3 days.
For us there is still a grey area with Germany because their national ruling on ACAS includes military aircraft - but the JAA rules, giving the 10/3 day MEL grace, do not apply. However, I don't think the German authorites could object to military operators applying a similar interval to that granted under JAA rules.
Brizeguy - Yes it is Honeywell equipment. Check your PMs.
Mr B - No formation is RVSM compliant. If 2000' seperation is not granted then the formatiion must go below/above RVSM. Hence non-RVSM routing s and levels shoudl be planned. I agree with Denti that there is no automatic requirement for TCAS to be in RVSM - it's just that most airspace has a conjoint requirement. The document you pasted says:
Are you saying that in your company requires you to descend out of RVSM if you suffered a TCAS failure?
Denti - you are quite right. I have no first hand experience of working with a MEL and was confusing exemptions with MEL relief. I have now seen the reference that you posted and it all becomes a little clearer -thanks.
Does anyone know if the lower 3 day limit apply to all aircraft flying through Germany/Switzerland or just to aircaft registered in those states? I notice that the FAA requiremnt is also 3 days.
For us there is still a grey area with Germany because their national ruling on ACAS includes military aircraft - but the JAA rules, giving the 10/3 day MEL grace, do not apply. However, I don't think the German authorites could object to military operators applying a similar interval to that granted under JAA rules.
Brizeguy - Yes it is Honeywell equipment. Check your PMs.
Mr B - No formation is RVSM compliant. If 2000' seperation is not granted then the formatiion must go below/above RVSM. Hence non-RVSM routing s and levels shoudl be planned. I agree with Denti that there is no automatic requirement for TCAS to be in RVSM - it's just that most airspace has a conjoint requirement. The document you pasted says:
Please note that there is no direct link between the requirements for ACAS II and RVSM cerification in EUR RVSM airspace.
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TCAS in MNPS
TCAS (Traffic Collision Avoidance System)/ACAS (Airborne Collision Avoidance System)
Aircraft operating in the MNPS are required to have TCAS/ACAS installed. However, MEL relief is provided for inoperative TCAS/ACAS, for dispatch into MNPS Airspace. TCAS/ACAS improves operational safety by enhancing pilot situational awareness and by providing a system for collision avoidance – particularly in densely populated airspace.
REF:-NORTH ATLANTIC MNPSA OPERATIONS MANUAL Chapter 15 page 110
Aircraft operating in the MNPS are required to have TCAS/ACAS installed. However, MEL relief is provided for inoperative TCAS/ACAS, for dispatch into MNPS Airspace. TCAS/ACAS improves operational safety by enhancing pilot situational awareness and by providing a system for collision avoidance – particularly in densely populated airspace.
REF:-NORTH ATLANTIC MNPSA OPERATIONS MANUAL Chapter 15 page 110
Worth bearing in mind that you only have a problem if you have two aircraft in a conflict situation who BOTH have inoperative TCAS, as long as mode S is working then the other aircraft's TCAS will issue an RA to its crew.
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Johman, 1x is enough. What was meant by Max angle is that if TCAS unit in aircraft A is U/S but its SSR ( mode S or C, does not matter ) is operative, the working TCAS unit of aircraft B wil issue and RA. It will not be coordinated, but it will get an RA away from mode C or S equipped aircaft.
Arba : not only pax numbers seats, but MTOW as well Different rules in Europe and US.
Arba : not only pax numbers seats, but MTOW as well Different rules in Europe and US.
Chrome wrote:
-- No it is not a no-go item. But if TCAS is found to be inop, it has to be deactivated/secured before flight and the ensuing enroute and approach procedures in-flight do not require its usage because if TCAS is inop, TAWS is unavailable as well.
On another note, I have frequently seen targets jumping around on TCAS, and sometimes the only traffic in vicinity visually located in a very different location to that indicated by TCAS. Cost me a go-around in BOS once.
