Which item must be removed prior to commencing a wash job on an aircraft?

In performing a wash job on an aircraft, it is essential to ensure proper safety measures are taken to prevent any damage to the equipment or to personnel. Removing "smokes" prior to washing the aircraft is critical because it typically refers to the exhaust smoke or what may be related to the hydraulic smoke (often seen in older aircraft or in specific contexts). This can interfere with the wash process as moisture and cleaning solutions can create issues with residue and visibility.

Additionally, unaddressed smoke systems could cause hazards or malfunctions during the washing process. Removing possible contamination sources supports a thorough wash without risking the functionality of critical systems. Ensuring that everything is in order before washing, particularly components that could be affected by water or cleaning agents, contributes to the maintenance of the aircraft's integrity and operational readiness.

The other items listed—radar systems, landing gear components, and engine covers—have different roles during maintenance, but "smokes" serves a direct connection to safety and efficiency in washing operations.