Ground crew check the number three engine of a Lancaster. An important part of maintaining the serviceability of a bomber squadron was “daily inspections” or “DI’s”. The routine maintenance of engines and their systems on a day-to-day basis was to prevent problems with the engines before they happened. A “DI” on a Lancaster would go something like this:

• Check all connections and joints on pipes and leads for tightness and leaks.
• Lubricate coolant pump.
• Check oil filter for metal particles and clean.
• Check coolant and oil levels.
• Test run engines and check mag-drop, temperatures and pressures