Operators with extended-range twin-engine operations (ETOPS) approval to fly their airplanes for more than 60 min from an en route alternate airport use the U.S. Federal Aviation Administration (FAA) Advisory Circular (AC) 120-42A for maintenance guidance as well as FAA Federal Aviation Regulation 121.161. Information in the AC includes the following:
- Maintenance planning.
- Oil consumption program.
- Engine condition monitoring (ECM).
- Airplane discrepancy resolution program.
- Reliability program.
- Propulsion system monitoring program.
- Maintenance training.
- ETOPS parts control.
Systems are purposely maintained to avoid working on redundant critical systems at one shop visit. Additional processes such as checklists and functional tests are developed for those occasions when such maintenance cannot be avoided during one shop visit.
Oil consumption program
Oil consumption analysis is performed to anticipate failures for both engines and other systems where oil
is used. For instance, some operators know the approximate oil consumption for a flight from Chicago to London. If the oil consumption is more or less than expected, a review is initiated to understand this
Engine condition monitoring (ECM)
Engine deterioration that might affect ETOPS operations is monitored through a disciplined data collection and analysis program. Some operators assess engine performance during flight with satellite data transfer processes. An ECM program is available from all engine manufacturers for their engines.
Airplane discrepancy resolution program
This focused process is established for dealing with engine shutdowns, primary system failures, and similar situations and is implemented by the ETOPS operator. For example, for one operator, all discrepancies on ETOPS flights are assessed by a team that includes the line engineers responsible for an airplane model, the system engineer for the system that produced the discrepancy, line maintenance, maintenance training, and the mechanics who perform the work.
A program for enhanced reliability is developed for early identification and prevention of ETOPS-related problems. The objective is to identify problems before they prompt an ETOPS flight discrepancy.
Propulsion system monitoring program
Specific criteria are developed for propulsion systems related to actions taken when various adverse trends occur. These criteria identify what events or rates of events will prompt action by the operator.
Operators enhance their normal maintenance programs to emphasize the key issues associated with ETOPS. For instance, mechanics learn about critical systems that could affect ETOPS operations.
ETOPS parts control
Operators implement a program to ensure that proper parts and configurations are maintained for ETOPS
Again, the basic rule for multiple similar systems is to perform maintenance on each unit at different maintenance visits. On many occasions, however, it is not possible or convenient for an operator to split this maintenance. In the document titled "ETOPS Guide, Volume II, Maintenance Program Guidelines" (D641T401, Rev B, April 1, 1998), Boeing describes a variety of practices to help operators avoid introducing problems into dual systems when maintenance is performed at the same visit.