All Weather Operations (AWOPS) CAT II & CAT III Maintenance Program Considerations

Introduction

With modern aircraft the basic aircraft provides CAT II/CAT III as inherent functions of the basic design standard of the aircraft.

Therefore, typical related “Autoland” tasks are covered by the respective AMM Task driven from the maintenance program.

Typically, it is not necessary for the introduction of additional or special recommendations for scheduled maintenance tasks.

Never the less, operators are expected to demonstrate compliance with supplemental national requirements whenever applicable.

In general and specifically for Airbus aircraft there are no tasks called up which require scheduled periodic performance, confidence tests or functional checks to assure CAT II/CAT III certification.

Maintenance Program Guidelines & Criteria

The aircraft maintenance program (which is the responsibility of the operator) should ensure that the correct maintenance should be performed to ensure inherent safety of the equipment is ensured. In the case of AWOPS related systems, priority is focused on the equipment required to be operational for precision approaches.

In the event of unscheduled maintenance task required due to operational, maintenance or tasks which are driven by the regulatory authorities will be required to perform tasks in accordance with the requirements of the relevant AMM chapter.

Reliability Program

A reliability program should be developed/extended to monitor, track and control the CAT III operational status of the aircraft and to achieve at least 95% successful CAT III landings in real and/or simulated conditions.

Maintenance Procedures

A specific procedure should be established to govern the capability of the aircraft to conduct CAT III operations in the following conditions:

- Operational: Impossible to obtain (or loss of) CAT 3 capability
- Missed approach (illumination of the red AUTOLAND warning light)
- Maintenance. Confirmed defect with corrective action carried out
- Unconfirmed defect but with corrective action
- Aircraft dispatch under MEL conditions
- Unable to correct defect and not under MEL conditions
- Unable to perform the required test

Therefore, upgrading/downgrading procedure must be defined so as to assist the dispatch of the aircraft to assure maximum autoland capacity.

The dispatch policy should be based on the minimum equipment list (MEL) as it governs the basic criteria for operation.

Dispatch criteria and status of aircraft must be recorded in the Technical Log Book with reference to the MEL (if any); if the defect has been rectified it should be cleared accordingly and revalidation of the aircraft status performed.

A prominent placard should be displayed on the aircraft and in the maintenance control room to inform Flight Operations of the current aircraft status.

In general, aircraft which perform Cat III operation regularly under real or simulated conditions do not need to perform system checks except if specified in AMM.

After an adjustment or a repair is made on the equipment, a revalidation of the aircraft should be made by the corresponding AMM ground test.

A periodic check may be requested by national authorities on an aircraft, which has not performed CAT III operations for a specific period of time (to be agreed with national authorities).

Data Collection

The operator shall provide crew flight reports or automatic flight recordings during all the operational demonstration.

Typically, automatic flight recordings shall be provided in addition to crew reports for operations with DH below 50ft (15m).

Each authority provides the list of data to be recorded. The following list can be used as reference.

- Crew Reports (all modes of operation)
Example of the data to be reported is:
- Airfield and runway used
- Weather conditions
- Time
- Adequacy of speed control
- Any out-of-trim condition at time of automatic flight control system disengagement
- Compatibility of automatic flight control systems, flight director and raw data
- Indication of the position of the aircraft relative to the ILS centerline when descending through 100ft (30m)
- Touchdown position
- Reason for failure leading to aborted approach
- Automatic Flight Recordings (for DH < 50ft or no DH only)
- Additional Data which may be required include
- Deviation from localizer at touchdown
- Flare time
- Date of descent at touchdown
- Pitch and bank angles at touchdown
- Speed loss in flare
- Maximum deviation during ground roll-out (for aircraft with automatic ground roll control or guidance intended for operations with no DH)

SofemaOnline www.sofemaonline.com offers the following online training "Introduction to All Weather Operations (CAT II & CAT III) For CAMO & AMO Staff" for details please email us at online@sassofia.com