ATA 34 Navigation Equipment

LEGEND

Procedures Required

(O) – An operational procedure
(M) or (M#) – A maintenance procedure
(O)(M) or (O)(M#) – Both operational and maintenance procedures

Repair Interval Categories

Category A

Items in this category shall be repaired within the time interval specified in the "Remarks or Exceptions" column of the air operator's approved MEL. Whenever the proviso in the "Remarks or Exceptions" column of the MMEL states cycles or flight time, the time interval begins with the next flight. Whenever the time interval is listed as flight days, the time interval begins on the flight day following the day of discovery.

Time Limited Dispatch - Some MMEL's for aircraft that are equipped with FADEC engines have relief that is subject to time limited dispatch expressed as a specific number of engine hours, and will start in accordance with the times established by the engine manufacturer or as indicated in the remarks column of the MMEL. Time limited relief cannot be extended.

Category B

Items in this category shall be repaired within 3 consecutive calendar days excluding the day of discovery.

Category C

Items in this category shall be repaired within 10 consecutive calendar days, excluding the day of discovery.

Category D

Items in this category shall be repaired within 120 consecutive calendar days, excluding the day of discovery. To be considered for placement in Category D, the item must be of an optional nature, or excess equipment which an air operator may, at his/her discretion, deactivate, remove from or install on an aircraft.

To be approved for Category D, the item must meet the following criteria:

  1. the absence of the item does not adversely affect crew member's workload;
  2. the crew members do not rely on the function of that item on a routine or continuous basis; and,
  3. the crew members' training, subsequent habit patterns and procedures do not rely on the use of that item.

Category D relief will generally not be approved for equipment which is considered to increase the level of safety, even if that equipment is of an optional nature.

ITEM:  34-10-1  ALTITUDE ALERTING SYSTEM

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Altitude Alerting System A 1 0 (O)

Except where enroute operations require its use, may be inoperative provided:

a) Autopilot altitude hold is operative, and

b) Repairs are made within three flight days.

D 2 1 One may be inoperative.
If not required by design standard and no autopilot installed C 1 0 (O) May be inoperative.

DISCUSSION:

References:  CAR 605.36, FAA PL 39 (Rev. 4, 29 Sep. 2008), FAA PL 84 (Rev. 1, 15 Aug. 1997)

The (O) must address increased altitude awareness.

Although there may be no requirement for an altitude alerting system in some aircraft, once installed, a category C is considered appropriate for pilot dependency and safety reasons.  These aircraft may not have an autopilot installed in which case the autopilot would not be a condition of relief.  For aircraft that have more than one altitude alerting system, a category D is assigned to the excess equipment.

This relief was harmonized with FAA PL 39 Rev. 3. However, Rev. 4 of this PL withdrew guidance to such relief, due to conflict with FAR 91.219 requirements.

FAA  Differences:  FAA does not provide guidance to this relief, due to conflict with FAR 91.219 requirements.

ITEM:  34-10-2  OUTSIDE AIR TEMPERATURE (or equivalent)

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Outside Air Temperature (or equivalent) - 1 At least one outside air temperature source must be operative.

DISCUSSION:

References:  CAR 605.18(e), CAR 605.30

Some indication of ambient temperature is required in order to determine icing conditions as well as correct power settings. Conversion charts may be required depending on temperature indication and format of performance information.

FAA  Differences:  FAA relief is identical to TCCA.

ITEM:  34-10-3  VERTICAL SPEED INDICATORS

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Vertical Speed Indicators
If required by design standard C 2 1 One may be inoperative for day VMC.
If not required by design standard C 2 1 For single pilot operations, the operative VSI must be on the side of the aircraft of the pilot flying.
A 2 0

Both may be inoperative for one flight day for day VFR.

NOTE:
Repair Interval extensions are not permitted.

DISCUSSION:

References:  AWM 525.1303(b)(3), CAR 605.16, CAR 605.18

There is no AWM 523 design requirement for a VSI.  In any case the CARs specify the requirement.

If the aircraft was certified with a VSI, it may be appropriate to grant relief on PNF side (e.g. DHC 8) for day VFR.  Consistent with the CARs, it is considered reasonable to require this instrument for the higher workload night environment as well as IFR.  However, relief is not considered appropriate for aircraft such as the B767, DC9 (withdrawn at Rev. 22).  Relief is 2/1, cat B on B1900; 2/1 cat C no restrictions on B400, but no relief on the Lear 60.  The relief is clearly aircraft dependent with considerations such as size, distance of flight deck above ground, handling qualities, etc.

FAA  Differences:  FAA has no Policy Letter for this item but the FARs consider the VSI as required equipment for Transport category aircraft.

ITEM:  34-20-1  FLIGHT DIRECTOR

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Flight Director C - 0

Except where enroute operations require its use, may be inoperative provided:

a) Approach procedures are not dependent on its use,

b) Autopilot is considered inoperative,

c) Windshear escape guidance is considered inoperative, and

d) If installed, takeoff and/or go-around switches are considered inoperative.

DISCUSSION:

References:  TP 1490E Manual of All Weather Operations (Categories II and III)

The C category may be upgraded to an A or B at the MEL level based on operational considerations such as the amount of reliance that is placed on the FD and the level of training with the FD inoperative.

AFM will identify any approaches that cannot be flown if the FD is inoperative as a result of certification flight tests.

Some autopilot installations are not dependent on flight director being operative, and basic attitude modes may still be available.  For highly integrated systems the autopilot may not function without the flight director, and therefore autopilot inoperative relief would also be applicable (Item 22-10-1).

FAA  Differences:  No FAA PL exists for this item.

ITEM:  34-20-2  FLIGHT INSTRUMENTS

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Flight Instruments

Standby Attitude Indicator

If required by regulation
(Stand-alone Display Configuration)

B 1 0 (M) May be inoperative for day VMC provided the instrument is clearly identified to the flight crew as inoperative.

If not required by regulation

C 1 0 May be inoperative provided an EADI is not installed.

Standby Attitude Indicator

(Shared Display Configuration)

(M) May be inoperative for day VMC provided the standby attitude indication is clearly identified to the flight crew as inoperative.

(if no gyroscopic rate of turn indicator)

C 1 0 (M)

May be inoperative for day VMC provided the indicator is clearly identified to the flight crew as inoperative.

Turn and Slip Indicator C 2 0 (M)

May be inoperative for day VFR provided the indicator is clearly identified to the flight crew as inoperative.

NOTE:
Does not include VFR OTT.

B 2 1 (M) One may be inoperative on the pilot not-flying side provided the indicator is clearly identified to the flight crew as inoperative.

DISCUSSION:

References:  AWM 523.1303 and AWM 525.1303, AWM 525.1321, AWM 525.1525, CAR 605.14, CAR 605.16, CAR 605.18, CAR 605.41, CASS 625.41, FAA PL 30 (Rev. 1, 15 Aug. 1997), FAA PL 111 (Rev. 1, 29 Jan. 2004)

No relief for standby airspeed indicator or standby altimeter, if they were required by certification.

AWM 523 and 525.1303 and .1321 list the flight instruments and navigation equipment that must be installed at each pilot station.  AWM 523 and 525.1525 state that the kind of operation to which the airplane is limited is established by the category in which it is eligible for certification and by the installed equipment.

The CARs contain operational requirements regarding flight instruments.  In reviewing the operational and airworthiness requirements it may be possible to permit some instrument alleviation (not for basic “T”) with restrictions e.g. day VFR, single pilot, etc.  Flight instruments in the basic “T” (airspeed, attitude, altitude and heading) must be installed and operative at each pilot station as required by the applicable regulations.  Alternate instrument location or alternate means of display such as “compacted modes” or standby instruments will not be considered unless certified as a primary means of display.

For smaller aircraft operated single pilot, relief for right side T instruments has been granted with certain restrictions.  Operational considerations or requirements may be more restrictive and could be reflected in the MEL.  If two pilots are required, then two sets of primary flight instruments are considered necessary.

It is noted that some European manufacturers grant relief for T instruments and the TC Supp will need to be amended accordingly.

FAA  Differences:  FAA sometimes includes operational regulation details in the relief.

ITEM:  34-20-3  NON-STABILIZED MAGNETIC COMPASS

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Non-stabilized Magnetic Compass B 1 0 May be inoperative provided any combination of three gyro or INS(IRU) stabilized compass systems are operative.
B 1 0 (O)

(O) May be inoperative provided:

a) Any combination of two gyro or INS(IRU) stabilized compass systems operate normally, and

b) Aircraft is operated:

1) With dual independent navigation capability, and

2) Under positive radar control by ATC during the en-route flight phase, or one of the navigation systems is a TSO’d GPS which provides track information.

C - - (O) May be inoperative for flights that are entirely within areas of magnetic unreliability provided at least two stabilized directional gyro systems are installed, operative and, if necessary, used in conjunction with approved free gyro navigation techniques.

DISCUSSION:

References:   CAR 605.14, FAA PL 10 (Rev. 1, 15 Aug. 1997)

Takes into account operators who have updated equipment and/or operate in areas where magnetic information is unreliable.

FAA  Differences:  TCCA adds the possibility of GPS in place of positive radar control.  FAA is cat B for third option.

ITEM:  34-30-1  RADIO ALTIMETER

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Radio Altimeter C - 0 May be inoperative provided approach minimums or operating procedures are not dependent on its use.

DISCUSSION:

References:  TP 1490E Manual of All Weather Operations (Categories II and III), CAR 704.36(1), CAR 705.47(1)

Consideration should be given to other equipment which may require radio altimeter information, e.g. ILS, Autoland, GWPS, TCAS, Master Warning/Master Caution inhibits, Stick pusher inhibits.  If there is other system dependency, the repair category of that other system will govern the radio altimeter repair category. (for example, if the radio altimeter is a required input to another system such as the GWPS, the repair interval for the GWPS should be applied to the radio altimeter).

Although the radio altimeter may not be required, once installed it is available to the pilots and there is some pilot dependency.  Therefore a cat C is considered appropriate.

FAA  Differences:  No FAA PL that addresses this item.

ITEM:  34-40-1  WEATHER RADAR

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Weather Radar D - - Any in excess of those required by regulations may be inoperative.

DISCUSSION:

References:  CAR 703.65, CAR 704.64, CAR 705.70, FAA PL 40 (Rev. 1, 15 Aug. 1997)

ETOPS has specific requirements.  TCAS may drive this relief as the same display may be used.

FAA  Differences:  The FAA has been inconsistent in assigning a category for the item.

ITEM:  34-40-2  GROUND PROXIMITY WARNING SYSTEM (GWPS) / TERRAIN AWARENESS AND WARNING SYSTEM (TAWS)

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Terrain Awareness and Warning System (TAWS) - Class A
1) GWPS A - 0 (O)

May be inoperative provided:

a) Alternate procedures are established and used, and

b) Repairs are made within three flight days.

a) Modes 1 to 4

A 4 0 (O)

May be inoperative provided:

a) Alternate procedures are established and used, and

b) Repairs are made within three flight days.

b) Test Mode A 1 0

May be inoperative provided:

a) The GWPS is considered inoperative, and

b) Repairs are made within three flight days.

c) Glideslope Deviation (Mode 5) B - 0 May be inoperative.
d) Advisory Callouts (Mode 6)*** C - 0 (O) May be inoperative provided alternate procedures are established and used.
e) Windshear Mode (Mode 7)*** C 1 0 (O)

May be inoperative provided:

a) Alternate procedures are established and used, and

b) Windshear Detection and Avoidance System operates normally.

C 1 0 (O)

May be inoperative provided:

a) Alternate procedures are established and used, and

b) Takeoffs and landings are not conducted in known or forecast windshear conditions.

2) Terrain System - Forward Looking Terrain Avoidance (FLTA) and Premature Descent Alert (PDA) Functions***

C 1 0 May be inoperative.

3) Terrain Displays***

C - 0 May be inoperative.

4) Runway Awareness and Advisory System (RAAS) ***

C 1 0 May be inoperative.
Terrain Awareness and Warning System (TAWS) - Class B
1) GWPS A - 0 (O)

May be inoperative provided:

a) Alternate procedures are established and used, and

b) Repairs are made within three flight days.

a) Modes 1 and 3

A 2 0 (O)

May be inoperative provided:

a) Alternate procedures are established and used, and

b) Repairs are made within three flight days.

b) Test Mode A 1 0

May be inoperative provided:

a) The GWPS is considered inoperative, and

b) Repairs are made within three flight days.

c) Modes 2, 4 and 5 *** C 3 0 May be inoperative.
d) Advisory Callouts *** C - 0 (O) May be inoperative provided alternate procedures are established and used.

e) Windshear Mode ***

C 1 0 (O)

May be inoperative provided:

a) Alternate procedures are established and used, and

b) Takeoffs and landings are not conducted in known or forecast windshear conditions.

2) Terrain System - Forward Looking Terrain Avoidance (FLTA) and Premature Descent Alert (PDA) Functions *** C 1 0 May be inoperative.
3) Terrain Displays *** C - 0 May be inoperative.
4) Runway Awareness and Advisory System (RAAS) *** C 1 0 May be inoperative.
Terrain Awareness and Warning System (TAWS) - Class C *** C/D - 0 (O)

May be inoperative provided alternate procedures are established and used.

NOTE:
Any mode that operates normally may be used.

DISCUSSION:

References:  CAR 605.37, FAA PL 54 (Rev. 10, 31 Oct. 2005)

This relief is predicated on the air carrier’s development and use of a flight crew operational procedure for increased aircraft altitude and performance awareness.

If there is no CAR requirement for a GWPS in an aircraft and no pilot dependency argument, category D may be appropriate.  However, because of the strong safety argument, it is recommended that a foreign category C be retained and the relief not be automatically downgraded to a D.

FAA PL 54 as well as FARs use TAWS as the standardized terminology for this type of equipment, which includes GWPS Modes 1 to 7 plus Terrain System elements (FLTA, PDA, and displays).  Some manufacturers use GWPS for the entire equipment, and refer to the Terrain elements as “Enhanced GWPS”.

TCCA currently adopts GWPS terminology, however, it is in the process of harmonizing the regulations with the FAA (see discussion below).

While the new regulations are not in effect in Canada, the relief used for equipment required as per CAR 605.37 should be the one related to TAWS Class A, as prescribed by this Guidance Book Item.

FAA  Differences: TCCA grants three flight days for repair whereas the FAA permits only two.  TCCA provides a second “C - 0” relief for Windshear Mode for TAWS Class A, which allows dispatch provided takeoffs and landings are not conducted in known or forecast windshear conditions.

TCCA uses GWPS terminology and addresses one class of equipment only, whereas the FAA uses TAWS terminology and addresses three different classes of equipment (A, B, and C) in their Policy Letter.  With respect to the FAA  regulations, FAR 91.223 requires TAWS Class B, FAR 135.154 requires TAWS Classes A or B (depending on passenger seating configuration), and FAR 121.354 requires TAWS Class A.

FAA TSO-C151b specifies minimum performance standards for Classes A, B, and C.

CAR 605.37 current requirements address GWPS and do not refer to different classes.  However, NPAs that are either pending legal editing or publication in the Canada Gazette I will likely harmonize the CARs with the FAA  regulations.  These NPAs introduce requirements for TAWS in CARs 703, 704, and 705.

As current Canadian regulations do not require the Terrain elements of TAWS, TCCA relief for FLTA, PDA, and the terrain displays (TAWS Class A) are assigned category C, while the FAA assigns category B.

ITEM:  34-40-3  WINDSHEAR DETECTION, WARNING, AVOIDANCE and GUIDANCE SYSTEM (PREDICTIVE)

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Windshear Detection, Warning, Avoidance and Guidance System (Predictive) ***
If required by regulation B - 0 (O)

May be inoperative provided alternate procedures are established and used.

NOTE:
Operator’s alternate procedures should include reviewing windshear avoidance and windshear recovery procedures.

C - 0 (O)

May be inoperative provided:

a) Alternate procedures are established and used, and

b) Windshear Warning and Guidance System (Reactive) operates normally.

If not required by regulation

D - 0 (O) May be inoperative provided alternate procedures are established and used.

DISCUSSION:

References:   FAA PL 67 (Rev. 3, 5 Dec. 2005)

There is no Canadian operational or aircraft certification requirement.

Since there is not the day-to-day crew dependency on the system as there is for TCAS, and since the system is passive until windshear is detected; once installed, but not required by regulation, a category D is considered appropriate.

Windshear Warning and Guidance System (Reactive) is normally designed as a function of the GWPS/TAWS.

FAA  Differences:  The FAA does not assign a cat D.  FAA only addresses air carrier with system installed in accordance with FAR 121.358.

ITEM:  34-40-4  TRAFFIC ALERT AND COLLISION AVOIDANCE SYSTEM (TCAS/ACAS)

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Traffic Alert and Collision Avoidance System (TCAS/ACAS)
TCAS II System B - 0 (M) May be inoperative provided the system is deactivated and secured

1) Combined Traffic Alert (TA) and Resolution Advisory (RA) Dual Displays ***

C 2 1 May be inoperative on the non-flying pilot side provided TA and RA elements and audio functions are operative on flying pilot side.
2) RA Display System(s) C 2 1 One may be inoperative on non-flying pilot side.
C - 0 (O)

May be inoperative provided:

a) All Traffic Alert display elements and voice command audio functions are operative, and

b) TA only mode is selected by the crew.

3) TA Display System(s) C - 0 May be inoperative provided all installed RA display and audio functions are operative.
TCAS I System B - 0 (M) May be inoperative provided the system is deactivated and secured.
1) TCAS Display System(s) C - 0 May be inoperative provided all installed audio functions are operative.

DISCUSSION:

References:  CAR 702.46, CAR 703.70, CAR  704.70, CAR 705.83, FAA  PL 32 (Rev. 7, 7 July 2006)

Wording may need to be changed to reflect a specific configuration.

For some designs, failure of a VSI/TRA would cause loss of the VSI function and result in a limitation for IFR flight at night; see Item 34-10-3 Vertical Speed Indicators.

ACAS is required in Canada as of July 1, 2007.

FAA  Differences:  FAA relief is different than TCCA in that TCAS I relief for TCCA is expanded to permit dispatch with display inoperative as done for TCAS II.

ITEM:  34-50-1  NAVIGATION AND APPROACH AID EQUIPMENT

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
Navigation and Approach Aid Equipment
VOR/ILS C - - Any in excess of those required by regulations and not powered by an emergency or standby electrical bus may be inoperative.
ADF, DME Systems D - - Any in excess of those required by regulations and not powered by an emergency or standby electrical bus may be inoperative.
GPS, FMS, MLS, INS, LORAN, Marker Beacons

If used routinely

C - - (O) Except where enroute operations require its use, may be inoperative provided alternate procedures are established and used.

If not used routinely

D - - May be inoperative.
GPS/FMS Data Base C - - (O)

May be out of currency provided:

a) Current Aeronautical Charts are used to verify Navigation Fixes prior to dispatch,

b) Procedures are established and used to verify status and suitability of Navigation Facilities used to define route of flight,

c) Approach Navigation Radios are manually tuned and identified, and

d) Approaches are not conducted using associated system.

DISCUSSION:

References:   CAR 605.18, FAA AC 20-138A, FAA AC 20-130A, FAA PL 3 (Rev. 1, 15 Aug. 1997), PL 63 (Rev. 3, 29 Jan. 2004), PL 98 (Original, 20 Jan. 1999)

Items such as VOR, ILS, GPS, etc., serve as primary navigation and approach aid equipment in Canada and a cat C is considered appropriate.

Cat D equipment may or may not be installed and/or used by an operator.  The MEL must reflect, through categorization, the nature of a specific operation (e.g. pilot dependency, frequency of use, etc.).  TC has adopted a cat C for Out-of Date Data Base information as per the FAA policy.

FAA  Differences:  FAA PL 3 only addresses DMETCCA policy on Navigation Database includes the FAA AC 20-138 and 20-130A guidance whereas this material is not yet included in FAA PL 98.

ITEM:  34-50-2  ATC TRANSPONDER and AUTOMATIC ALTITUDE REPORTING SYSTEM

System and Sequence No. Item Repair
Interval
Category
Number
Installed
Number
required
for
dispatch
Procedures
required
Remarks or Exceptions
ATC Transponder and Automatic Altitude Reporting System C - - As required by regulations.
If not required by regulations D - 0 May be inoperative.
ADS-B Squitter Transmissions A - 0

May be inoperative provided:

a) Operations do not require its use, and

b) Repairs are made prior to completion of the next heavy maintenance visit.

DISCUSSION:

References:   CAR 605.35, FAA PL 76 (Rev. 5, 24 Mar. 2008), PL 84 (Rev. 1, 15 Aug. 1997)

Note that TCAS relief may drive this relief.

Depending on the design (e.g. CL 604), the following may be required in the MMEL:

“NOTE:
Transponder and Flight Director/Autopilot must use same ADC data for RVSM operations.”

National regulations may prohibit transmission of incorrect ADS-B data even when it is not used for operations of the aircraft, as it can affect Air Traffic Control safety and efficiency.

FAA  Differences:  FAA assigns category B to Transponder and includes ADS-B relief.

Date modified: