MROs Developing the Air Carrier Interface

It’s not uncommon to have similar aircraft side-by-side, worked to different requirements and processes aimed at compliance to the same regulations.

The interface between maintenance repair organizations (MROs) and their air carrier customers is a complex stew of individual processes meant to meet each other’s regulatory requirements but developed separately. Each is based on experience, regulatory interpretation, and return to service goals. MROs must work on each operator’s aircraft in accordance with applicable provisions of its maintenance and inspection program. Each operator is separate but equal. As a result, it’s not uncommon for an MRO to have similar make and model aircraft side-by-side, worked to different requirements and processes aimed at compliance to the same regulations.

In planning work on an operator’s aircraft, the MRO tries to accommodate the unique maintenance program of each carrier. By combining the operator’s processes with its own it is able to provide the necessary services to deliver an aircraft. Such efforts are not without their challenges.


The hangar plan evaluates hangar space and dwell time for each hangar position. In a nose to tail schedule, the area must have the flexibility of allowing aircraft movement. Production plans allow for use of the hangar space for a predetermined period of time. Based on an operator’s program, the scope of inspection may drive use of the space over irregular periods. Two similar airframes may come in for a C check but the scope of inspection for either creates different dwell periods for the aircraft. One aircraft will sit 10 days; the other three weeks.


Managing tooling is a major headache for the reason that there is so much of it and it all costs a fortune. Equivalent tooling may be used. Having a robust equivalent tool development process can pay dividends in cost savings without impacting safety or compliance. However, it’s possible that certain carriers may restrict the MRO to only using manufacturer’s authorized tooling based on its process standards. Other carriers do not have a problem with equivalent tooling.

Tooling issues should be resolved well in advance to assure that production stoppage or bottlenecks don’t occur. The MRO’s quality unit needs to scope these requirements in advance of an operator’s arrival. The air carrier’s quality unit should be able to provide advance knowledge of these issues.

Current data

Most air carriers can provide current data for their aircraft. In fact when aircraft are customized to the operator’s specification it’s usually the only way. Operator’s manuals arrive in a variety of media. It’s not uncommon for classic aircraft operators to continue to have microfilm. Newer aircraft have a better time of it since they come with electronic media access. In this case the problem is more about access since the station where these data are located can be away from the aircraft and there is a line to use it.

One aspect of technical data that an MRO must control is the availability of “reference only” material. Technicians may hang on to obsolete data if access to computers or readers is limited by availability. Printed media left from other projects will find themselves in use if the processes for their control are weak. Data from one carrier’s 737 may show up on another without processes in place to prevent it.

Printed hardcopy from electronic media must be date stamped for the job and then at a designated time discarded. Old hard copy manuals may have value only if the MRO is maintaining classic equipment and the revision can be determined the most current. Otherwise they should be retired to a dumpster in a condition that precludes retrieval by inquiring minds and idle hands.


Effective training is necessary for the success of any project. Training goes beyond technical matters. MROs need to educate everyone involved on the carrier’s unique requirements defined in their general maintenance manual. In each carrier’s manuals lies its own method of record keeping, task card design, inspection criteria, part certification requirements, engineering criteria, and technician qualifications. The processes of two B-737s parked together in a hangar bay may have different required inspection item (RII) listings. MRO personnel need to be ready to learn the difference between the carriers. The differences create a rich environment for errors.

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