Returning aircraft to service

The return to service of aircraft is a hot topic. As the aviation world has been heavily impacted by the COVID-19 pandemic an unprecedented number of aircraft have been grounded. Travel restrictions have caused a huge decline in flying, with many planes put in extended storage. This situation causes severe pressure on air operators, as well as on their service providers. Thanks to a gradual lifting of travel restrictions however, passenger flights are now starting to resume again. This requires first of all, to restore an airworthy condition as many aircraft have been stored for weeks or months.

What is it?

The aircraft return to service statement, often referred to as CRS (certification for release to service) is the most important document to keep an aircraft flying. It contains the signature and certificate number of the person approving the aircraft for return to service and is part of the aircraft’s logbook. In most cases it is a written certification that tells whether or not the aircraft is airworthy and ready to fly. It is a formal statement and regulated by aviation authorities such as FAA, EASA.

When does it happen?

• After maintenance; A, B, C and D checks
• After each inspection; unscheduled maintenance such as lighting- and bird strikes
• After storage; restoring airworthiness

The process

Most of the aircraft parked due to the pandemic have not undergone major maintenance programs. Whether it is small check or a full maintenance check it is the engineers’ responsibility to check the aircraft for problems on behalf of the maintenance organisation and signing off the paperwork. Examples of issues found after extended parking periods include:

• Engine borescope ports found loose
• Flap access panel missing
• Depletion of brake accumulator pressure

All repair, maintenance and modifications made to the aircraft, including during storage, must be documented and carried out as per procedures set by manufacturers and authorities. Additionally, airlines have to comply with stringent redelivery conditions stipulated in lease agreements. Once everything is sorted out, the engineer signs off the paperwork or makes a digital stamp of all work performed. Nowadays this is mostly done on a digital tablet which holds all aircraft records and is stored in the aircraft cockpit.

Once the engineer has placed his (digital) signature the aircraft is airworthy again. In the last step the pilots pick up the plan and make a final check of the logbooks. When they see the signature of the engineer they know that the aircraft is fit to fly and that it can confidently return to service.