Quote Originally Posted by mklotz View Post
Surprisingly, this compilation...

https://bluejacket.com/usn_avi_lta.html

indicates that the the earliest classes of Navy dirigibles (A, B, C) were filled with hydrogen. It wasn't until C-7 that helium was used.

I suspect the smaller of the two tubes was used to spill the water ballast so the ship could rise. The other tube might be a gas vent for descending. Maybe that tube is a fill tube. In either case, why the strange angle?
According to the article provided by Denis G the tube being at the angle positioned near the prop was to force air into the ballonets the small tube would have been for venting said air.
Kind of an interesting way of controlling altitude plus ascending and descending. Also it would be a delicate balance between slightly compressing the helium by reducing its free volume with the air in the ballonets the air would also become denser under a slightly higher pressure making it negatively buoyant