Thoroughness in research is a great thing, but realize that maybe 1% of what you find will actually make it onto the page. Research is also a great way to find out what NOT to do. For instance, if someone wrote, "I grabbed the 747's four throttles and jammed them forward to the afterburner detente," I'd scream bulls***! A 747 is not a bloody Concorde! I'd the writer was an idiot.
Onto airships.... I'd recommend researching the concept of "weighing off". It's a vital part of airship handling near the ground. Essentially, prior to both departure and landing, the ship must balance its lifting gas and weight to achieve proper buoyancy.
Departure was a balancing act. There are many factors in play here. There's of course the structural weight of the ship, loaded ballast, the weight of the fuel and stores, and the weight of people and cargo. There are also outside factors, such as temperature, barometric pressure, and the aerodrome's altitude above sea level, which play a dramatic role in the effectiveness of the lifting gas. The key is to get the airship off the ground, either with neutral or slight positive buoyancy. This is achieved by dropping ballast until the airship is able to rise on its own. Most vintage rigid airships were overloaded with ballast upon departure, allowing them some leeway in the effort to find the ideal weight.
One airborne, fuel is burned, food is consumed, waste matter produced, and drinking and bathing water is consumed. Lifting gas may be vented for altitude changes. Water ballast may be vented. The long and short is that the ship will never the weigh the same on arrival as it did on departure.
While in cruise flight, this change in buoyancy can be offset by trimming the flight controls. For instance, if the ship is too light, a slight bow down attitude can be dialed in to maintain level flight. Too heavy? Trim bow up.
However, once you're in the low speed landing phases, the flight controls don't have much aerodynamic authority. It then becomes crucial to achieve proper buoyancy. At this point, it's another balancing act. Gas may be vented to lower an overly lightened ship. Weight may even need to be dropped if too much gas was vented during the flight. As a side note, the operators of helium-based ships were very reluctant to vent gas, as helium is simply quite rare and expensive.
Later rigid airship designs took measures to combat the weight change and conserve their lifting gas. The German Zeppelins would not vent waste water from cooking/toilet and instead stored it in "dirty water" tanks. The
Graf Zeppelin actually used a propane-like gas - called blau gas - as engine fuel due to its buoyancy compensation effects. The
USS Akron and
Macon incorporated water reclamation devices to capture condensation coming off the engines and store the water in ballast tanks as an effort to counteract the burned fuel. You can see them below as the white stripes above each engine.
http://upload.wikimedia.org/wikipedia/commons/0/0f/USS_Akron_in_flight%2C_nov_1931.jpgThe
Macon and
Akron would also depart without their Sparrowhawk scouting aircraft aboard. While ten thousand pounds worth of airplanes would have impeded the airship from getting off the ground, once the ships were in cruise flight they could trim away the effects of the weight. Therefore, their aircraft would take off under their own power from an airport and join the ships in flight. Additional fuel and store weight would be burned away during the remainder of the flight, enabling the airship to land with the aircraft on board.
For more information, check out this Wikipedia page I just stumbled across:
http://en.wikipedia.org/wiki/Buoyancy_compensator_%28aviation%29You may not have to know the formulas, weight-and-balance sheets, checklists, and all the other minutia involved in weighing a ship off. That would make for some boring reading! However, a general working knowledge of lift vs. weight as applied in airship operations will certainly lend authenticity to your work.
