Hybrid Airships were an early attempt to bring airships back to passenger aviation. They proved dificult to work with.
In 1783, the first hot-air balloon ride occurred. There was one problem though. How would a lighter-than-air aircraft move against the wind? In 1852, Henri Giffard built a powered hydrogen balloon which a steam engine. The steam engine was too weak to handle the wind. Steam engines were also too heavy. Even with lighter internal combustion engines, the airships were still too small. The first practical passenger airship was design by Ferdinand Graf von Zeppelin in 1893. For 44 years afterwards, airships were transporting passengers around the world. Then, in 1937, a zeppelin called the Hindenburg burst into flames. It would be a while afterwards before airships went back into passenger service. Hybrid airships running on helium were an early attempt.
Tech Level: 10
A hybrid airship got most of its lift from the helium it carried. The engines were there for the airship to become airborne. With that, hybrid airships could land like airplanes, and maintenance and loading and unloading of cargo were easier. The piston engines could rotate to change direction. Unfortunately, hybrid airships had problems. They were not aerodynamic. Control was difficult. The weather was capable of messing them up. Hybrid airships never became popular. More advanced full airships would take there place.