What is the main advantage of bladder tanks?

Bladder tanks are specifically designed to be lightweight and removable, which is a significant advantage in various applications, especially in aviation. Their lightweight nature contributes to overall fuel efficiency and performance of the aircraft, as less weight means better fuel economy and the ability to carry more useful load. Additionally, the removable aspect allows for easier maintenance and inspection procedures. This is crucial in an operational context where minimizing downtime is a priority.

Furthermore, bladder tanks can be designed to fit into irregular spaces, maximizing the use of available volume for fuel storage while adhering to weight constraints. Their flexibility in positioning within the aircraft is another benefit, as it allows engineers to optimize the aircraft's center of gravity. While other choices may touch on ideas related to fuel efficiency or maintenance, the core advantage of bladder tanks is their lightweight design combined with the ease of maintenance due to their removable nature, making option D the most comprehensive answer.