FAA Requires Aircraft Washing Before Annual and 100-Hour Inspections

A general aviation aircraft owner raised concerns after discovering that a maintenance shop had skipped washing the airplane during its annual inspection. Shop personnel told the owner that washing is no longer standard practice, prompting the owner to ask whether the omission violated regulatory requirements under Part 43, Appendix D of the Federal Aviation Regulations.

The FAA responded that thorough cleaning of both the aircraft and engine, including washing, is required before annual or 100-hour inspections. The agency said the purpose of this requirement is to ensure that no airworthiness issues are obscured and that every surface can be properly examined during the inspection.

The FAA also stated that it provides specific guidance on cleaning and corrosion prevention, and that maintenance personnel are required to follow applicable aircraft and engine manufacturer maintenance instructions for cleaning methods, materials, and precautions appropriate to the specific aircraft.

This case shows how a routine inspection step can become a point of dispute when shop practice diverges from what the regulation actually requires. An owner's question surfaced a gap between what one shop described as common practice and the FAA's own reading of Appendix D, a gap that could otherwise persist unnoticed across many annual inspections.

The requirement exists precisely so that surface-level dirt, grease or residue cannot mask corrosion, cracks or other airworthiness concerns during an annual or 100-hour inspection. Manufacturer-specific cleaning instructions matter because materials and methods appropriate for one airframe or engine may damage or compromise another.

Whether this prompts broader scrutiny of shop practices depends on how widely owners and inspectors raise similar questions, and on whether the FAA issues any further clarification beyond its response in this instance.