Avro Lancaster - Dambuster special

The Avro Lancaster Mk.III Special were initially known as Type 464 Provisioning. Twenty-three of them were modified to carry the "Upkeep" bouncing bomb for the raids against the dams of the Ruhr valley.
Bomb bay doors were completely removed and Vickers-built struts were fitted to carry the bomb at Woodford Airfield, near Stockport. The bomb was spinned using an hydraulic motor that was driven by a pump that initially was part of the mid-upper turret and lamps were added both in the bomb bay and the nose in order to help the simple height measurement system which enabled the accurate control of low-flying altitude at night. Mid-upper turret was removed in order to save weight and the gunner moved to the front turret so the bomb aimer didn't have to man the turret while reading the maps.
All of them served with famous No.617 Squadron of the Royal Air Force and carried out the famous Operation Chastise when they bombed the heavily defended Ruhr valley dams using the bouncing bombs that, in order to detonate, required a long low altitude run and a timed releasing of the bouncing bomb that normally exploded at the base of the dam.

Sources:
1. https://en.wikipedia.org/wiki/Avro_Lancaster
2. https://en.wikipedia.org/wiki/No._617_Squadron_RAF
3. https://en.wikipedia.org/wiki/Operation_Chastise
4. Signal Squadron - Aircraft In action 52 - Lancaster in Action