ATA 22 Auto Flight

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:  22-10-1  AUTOPILOT

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

Autopilot

a. Transport Category Aircraft with only one Autopilot Installed

B 1 0

 

 

b. Transport Category Aircraft with two or more Autopilots Installed

C - 1  

Any in excess of operational requirements may be inoperative.

B - 0   May be inoperative except where enroute operations require its use.

c. Non-transport Category Aircraft

C - 0   May be inoperative provided operations do not require its use.
D - 0   May be inoperative provided routine procedures do not require its use.

DISCUSSION:

Reference:  FAA PL 101 (Rev. 1, 13 Sep. 2001)

In recognizing the foreign authority responsibility, TC will not change a cat B for a foreign airplane trusting that the cat B was assigned for valid certification and generic (human factor) operational reasons by the foreign authority.  For domestic airplanes TC will assign a category appropriate to the airplane after discussion with the manufacturer and operational regulators.

The cat D relief is to cater to mixed fleets where for aircraft of the same type some have autopilots and some do not, with no crewing restrictions.  The MEL authors will need to assign the appropriate category depending on specific aircraft fleets and operations.

FAA Differences: FAA assigns a cat B as discussed in PL 101 and cat C for small single engine aircraft.

ITEM:  22-10-2  AUTOPILOT DISCONNECTS

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

Autopilot Disconnect Functions (Quick Release Controls)

C - 1  

One may be inoperative provided:

a) The autopilot is not used below 1,500 ft AGL,

b) Approach minimums do not require the use of the autopilot, and

c) The pilot flying has the operative disconnect.

B - 0   May be inoperative provided the autopilot is not used.

DISCUSSION:

References:  AWM 525.1329, FAA PL 93 (Rev. 1, 11 Sep. 2006)

A review of autopilot certification hardover and slowover tests will determine the Autopilot Disconnect relief which can be permitted for this item and the specific altitude which will be used to define the approach minimums.  Some MMELs specify the initial approach altitude but this may not be appropriate for all aircraft nor is it meaningful for VFR operations.  Some operations do not have published initial approach altitudes.

Consideration must be given to what other functions are performed by the disengage buttons, e.g. stick pusher.

FAA Differences: TCCA requires the operative autopilot disconnect to be on the pilot flying side. 

ITEM:  22-10-3  AUTOPILOT DISCONNECTED WARNING SYSTEM

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

Autopilot Disconnected Warning System

B 1 0  

May be inoperative provided the autopilot is considered inoperative and not used.

DISCUSSION:

References:   AWM 525.1309(c)

Because ever increasing emphasis is being placed on the use of the autopilot for flight operations, an operative warning of disconnection is considered necessary.  If required by the basis of certification, there is really no compensating factor.  For some aircraft such as the B767, parts of the Disconnected Warning System may be inoperative as there are other indications.  In these cases it may be appropriate to limit autopilot use to 1500 ft AGL or above.

The requirement to consider autopilot inoperative and not used may not be sufficient in some circumstances (e.g. single-pilot operations), where pilots would still be tempted to use the autopilot in specific phases of the flight to minimize workload.  Therefore, operators should review the nature of their operations and consider adding an (M) procedure in the MEL to ensure the autopilot is disabled before dispatch with autopilot disconnected warning system inoperative.

FAA Differences: The FAA does not provide specific MMEL policy for Autopilot Disconnected Warning System relief.

ITEM:  22-20-1  MACH TRIM SYSTEM

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

Mach Trim System

C 1 0  

May be inoperative provided:

1) Enroute operations do not require its use, and

2) Operations are conducted at or below XXX KIAS/ .XXM when autopilot disengaged.

DISCUSSION:

References:  nil

Some aircraft require the Mach trim system to be functional throughout the whole flight envelope, so this relief may not be appropriate to all aircraft.

FAA DifferencesFAA relief is similar to TCCA.

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