An important part of maintaining the serviceability of a bomber squadron was “daily inspections” or “DI's”. This was the routine maintenance of engines and their systems on a day-to-day basis, and was to prevent problems with the engines before they happened.

A “DI” on a lancaster would go generally 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

This of course had to be done for each of the four engines, and was aside from more specific problems to be fixed that the crew may have reported. This could be anything from a faulty propeller, to a troublesome main undercarriage.