Tandem Rotor Helicopter

0:00 Intro
0:08 Components
0:44 Engine Input
0:58 Engine Start
1:14 Two Engine Operation

An animation of a twin-engine, tandem rotor, helicopter drive system

This was loosely based on the CH-46 Sea Knight with two turbo shaft engines in front of the aft transmission. The engine output shafts are on the rear of each engine and both input power directly into only the aft transmission. The forward transmission is not directly powered from the engines, but rather from a synchronization shaft the runs the length of the fuselage.

Tandem rotor helicopters require a synchronization shaft which powers the front rotor system directly from the aft transmission. These aircraft can fly with one engine failed. With one engine powering the aft transmission, the forward transmission will also receive power via the synch shaft. A failure of the synchronization shaft is immediately catastrophic because the forward and aft rotor blades will contact each other soon after this failure.

I didn't model the rotor controls, but control of a tandem helicopter is done with collective and lateral cyclic blade pitch. Aircraft pitch control comes from differential collective pitch at each of the rotor heads. Yaw control comes from differential lateral cyclic pitch and roll control from simultaneous lateral cyclic pitch. Longitudinal cyclic commands are used for speed trim (in the CH-46 and CH-47) and not for aircraft pitch control.

I did the modeling in Fusion 360 and rendered this in Blender.