The elevator valve controls the fuselage’s pitch. It consists of two main sections. Vacuum enters the bottom section via a pipe connected to the vacuum manifold. The vacuum is distributed by ports in the top section. Vacuum is supplied to either the South bellows causing the trainer to pitch UP; or to the North bellows causing the trainer to pitch DOWN. As vacuum is supplied to one bellows, causing the trainer to pitch; the opposing bellows is opened causing negative pressure. This pressure is relieved through exhaust ports in the top of the elevator valve.
We recently refurbished our model Esp’s Elevator Valve. The sections were stuck together with dirt and dried lubricant. This video shows how to refurbish the elevator valve, and describes its operation. We reconnected the valve with the manifold and front/rear pitch bellows using new 5/8” vacuum hoses.