ATA 00 General

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:  00-00-1  CAS (Crew Alerting System) MESSAGE MMEL RELIEF

EXAMPLE OF PROPOSED RELIEF FOR ITEM IN SECTION 2 OF MMEL

System and Sequence No. Item Repair
Interval
Category
Procedures
required
Remarks or Exceptions

1. CAS Message

2. Dispatch Consideration

SAFETY VALVE OPEN
(Advisory)

C

(O)

Except for ER operations, aircraft may be dispatched provided:

a) Both air conditioning packs operate normally,

b) Operations are conducted unpressurized at or below 9,000 ft MSL,

c) Take-offs and landings are not conducted on runways near bodies of water, and

d) Extended over-water operations are prohibited.

SMALL SERV DOOR
(Caution)

C

(O)

Aircraft may be dispatched provided prior to each flight all small service doors are verified CLOSED, LATCHED and LOCKED.

DISCUSSION:

References:  FAA PL 119 (Rev. 2 Draft, March 2008)

General:

The TCCA approved MMEL for the BD 700 aircraft introduced a Section 2 to cater for the use of failure indications (a message on EICAS, ECAM, etc.) of equipment as a means to provide relief for a failed system/component.  This GB item 00-00-1 is intended to provide guidance for MMEL developers to permit the use of this approach for aircraft equipped with modern technologies which allow some aircraft systems to carry out self-diagnostic tests to determine system health status and present it to the flight crew through indication in the flight deck (a message on EICAS, ECAMetc.).

Also, some fairly simple systems may provide failure annunciation in the flight deck, which points directly to the failed system/component, such that there is no need for fault isolation procedures to be carried out by maintenance personnel to determine that this equipment has failed.

Following discussion with members of the FAA Aircraft Evaluation Group and the North American Aerospace Industry, TCCA has developed the following guidance material while attempting to harmonize as much as possible with the FAA Policy.

Specific Considerations:

The MMEL item may grant relief for a failure indication (a message on EICAS, ECAM, etc. annunciating failure of aircraft equipment) rather than the failed equipment, in which case the determination of whether or not the aircraft can be dispatched in accordance with MMEL will be based on this failure indication. No failure isolation procedures are required to be carried out by maintenance personnel for such MMEL items (CAS message MMEL items) to determine the failed equipment.

The MMEL item may grant relief for a failure indication (a message on EICAS, ECAMetc.) if the justification supporting this MMEL candidate considers all potential failures triggering this failure indication and it is shown that the provisos of this MMEL item ensure safe operation of aircraft with any one or combination of these failure(s) present.

The MMEL relief may be granted for a failure indication that annunciates:

  • loss of redundancy within the system/component,

  • loss of system function,

  • failure of a single system/component,

  • failure of multiple components.

Such MMEL items (CAS message MMEL items) may include (O) procedures requiring deactivation or securing of the specified system or component into an acceptable configuration for aircraft operation under MMEL.

In reviewing such MMEL candidates (CAS message MMEL items), TCCA should use the normal MMEL review processes that are currently used for an MMEL candidate evaluation. Special attention should be paid to the possible effects of no maintenance personnel carrying out a failure isolation procedure, since the decision of whether or not the aircraft can be dispatched in accordance with MMEL will be based, in this case, on a failure indication (a message on EICAS, ECAMetc.).

Once approved, the CAS message MMEL items may be incorporated into the MMEL in a new Section, as described and illustrated below.

INCORPORATING WITH EXISTING MMEL RELIEF

Existing aircraft MMEL programs that may wish to incorporate a CAS message section may be permitted to do so, using the same principles of justification described above.

The optional MMEL shall be divided into two sections, the “LRU-oriented” MMEL section and the CAS message section.

The first section (Section 1) continues to use the existing “LRU-oriented” MMEL format and should address the following type of equipment failures:

  • failures which are not annunciated to crew, and

  • failures which are annunciated, but the failure indication by itself is not considered sufficient to determine the aircraft dispatch status.

The second section (Section 2) should address the equipment for which failure indication can be used to determine the aircraft dispatch status, and should be formatted as follows:

It should have only two columns. The first column should list the failure indications (messages) for which relief is given (if desired, the messages will be listed in alphabetical order with no ATA breakdown. The second column should include the corresponding MMEL limitations and/or procedures; the format of this column should be in line with the format requirements of “Remarks or Exceptions” column of the conventional “LRU-oriented” MMEL.

During the periodic revisions to existing MMELs, CAS message relief may be proposed for all new relief candidates, and also, in a process of gradual transfer from existing / approved “LRU-oriented” MMEL section, existing items and their respective relief provisos, can be transferred to the CAS message section. The transfer to this section, however, will only be possible providing the relief provisos for the associated message remain appropriate for failures of each and all of its underlying contributing causes.

In further consideration of the movement of “LRU-oriented” MMEL relief items / provisos to CAS message section, this does not necessarily exclude the “LRU-oriented” MMEL relief from continued inclusion in Section 1. Section 2 may be employed as an alternative dispatch relief methodology - Section 1 relief will be retained in order to provide maximum flexibility for relief.  Flight crews / operators may dispatch failures with reference to either Section 1 or Section 2, to the advantage that either may provide.

Under this dual-use approach, it will be expected that in many cases that when comparing dispatch relief provisos for posted messages in Section 2, to those of the related LRU / Component dispatch relief in Section 1, the provisos associated with dispatching the annunciated message may generally be expected to be more restrictive in content and relief interval. Without the opportunity for fault isolation through maintenance, it must be assumed that worst-case failure conditions always underlie the posted message - commensurately, dispatch may be expected to be more restrictive. Conversely, where maintenance personnel are available and fault isolation conducted, relief provisos in Section 1 may be found to provide fewer or less stringent restrictions upon operations and offer a longer relief interval.

Where a single set of provisos cannot be proposed that adequately supports all failure causes, dispatch will continue to rely upon the standard methods of failure determination and subsequent referencing of the “LRU-oriented” MMEL section for any available relief. 

Supporting analyses of CAS Message relief candidate proposals may determine that prior to dispatching, the flight crew must accomplish one or more steps to secure the affected system. Where deemed necessary, the familiar “(O)” indicates the need for such supporting tasks, the scope of which shall be at the discretion of TCCA.  Acceptable tasks include, but are not necessarily limited to the following duties:

  1. procedures described which exercise cockpit (or cabin) system controls utilized in normal flight operations;

  2. deactivation of affected systems, as achieved by pulling system breaker or use of remote electronic system isolation;

  3. visual inspection behind panels (internal or external) which are accessible without tools via quick-release latches and which clearly indicate their unlocked or unsafe state;(red/green safe window; flush fit latches)  (candidates to be verified by TCCA)

  4. visual confirmation of remote gauge indications, or valve positions as provided by integral external indicators.

To accommodate these dispatch (O) procedures, it is recommended that a separate section be added to the MMEL dispatch procedures manual, such that the alphabetized order of the CAS message relief do not conflict with the existing ordering sequence of Section 1 items.

INCORPORATING SECTION 2 INTO THE MMEL

With respect to incorporating Section 2 into the MMEL, in order to provide standardization, MMEL documents shall be assembled with consideration of the following:

  1. Front matter pages:

    1. Log of Revisions pages shall be updated to include Section 2 amendments when applicable.

    2. Control Pages shall be expanded to include revision status and date of each page in Section 2.

    3. Highlights of Change pages shall be updated to include Section 2 amendments when applicable.

    4. Following Preamble page, add a new section divider page entitled: “SECTION 1 LRU/COMPONENT MMEL Relief”

  2. Section 2

    1. Following the last page of relief for ATA 80 in Section 1, add a new section divider page entitled: “SECTION 2 CAS Message MMEL Relief”

    2. A new INTRODUCTION section shall explain principles of the CAS message relief methodology. A minimum Standard wording to the INTRODUCTION is provided below.

    3. A Table of Contents page should accompany section 2, wherein the list of included CAS Message relief items are listed in alphabetical order.

    4. Some flexibility may be exercised to add a separate page: “NOTES:”, following the INTRODUCTION, where deemed helpful to operators, in order to explain / accommodate specific aircraft variances. Such page(s) shall remain separate from those of which are standardized.

The following to be incorporated as standard wording to Section 2:

INTRODUCTION

The following new section has been authorized in accordance with the provisions of TCCA MMEL GB Item 00-00-1, Rev. 1 or later, regarding MMEL dispatching directly from displayed CAS (Crew Alerting System) messages. “CAS message” relief is an alternative to the standard method of MMEL dispatch relief, as is normally achieved through fault isolation procedures, and the subsequent dispatch under traditional LRU-oriented MMEL relief. This Section 2, as it is referred to, has been developed with the objective of allowing flight crews to dispatch from the displayed CAS message, without specifically identifying associated failed LRUs or components.

As Section 2 is intended as an alternative dispatch relief methodology the LRU-oriented relief (Section 1) will be retained in order to provide maximum flexibility for dispatch relief.  Flight crews / operators may dispatch failures with reference to either Section 1 or Section 2 of this MMEL to the advantage that either associated relief may provide.  Upon comparison, it may be recognized in some cases that dispatch relief provisos for posted CAS messages to those of the related LRU dispatch relief, the provisos associated with the CAS message can appear more restrictive in content and/or relief interval. Without the opportunity for fault isolation through maintenance, it must be assumed that worst-case failure conditions always underlie the posted message - commensurately, dispatch should be more restrictive.  However, where maintenance personnel are available and fault isolation conducted, relief provisos in Section 1 may be found to provide fewer or less stringent restrictions upon operations and offer a longer relief interval.

Section 2 has been arranged in alphabetical order of the indicated CAS message, without association to ATA Chapter.  However, to avoid any possible mis-identification, each message is identified beneath as to its alert level.

Repair intervals (A, B, C & D) associated with CAS message reliefs herein, remain consistent with those of Section 1, and as described in the Definitions section in the front matter of this MMEL.

In conjunction with Section 2, a new separate dispatch procedures section has also been developed, also arranged in alphabetical order of the indicated CAS message.  Where deemed necessary, the familiar “(O)” indicates the need for such supporting tasks, the scope of which shall be at the discretion of the MMEL approval authority.  Acceptable tasks include, but are not necessarily limited to the following duties:

  1. Procedures described which exercise cockpit (or cabin) system controls utilized in normal flight operations;

  2. Deactivation of affected systems, as achieved by pulling system breaker or use of remote electronic system isolation;

  3. Visual inspection behind panels (internal or external) which are accessible without tools via quick-release latches and which clearly indicate their unlocked or unsafe state;(red/green safe window; flush fit latches)  (candidates to be verified by TCCA)

  4. Visual confirmation of remote gauge indications, or valve positions as provided by integral external indicators.

FAA Differences:  FAA relief is identical to TCCA.

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