The term 'Spence two propeller' is used under which condition?

The term 'Spence two propeller' is used under which condition?

• A. When 1-1 is at GE
• B. When 1-1 is at OGE
• C. When 1-1 is at GPA
• D. When 1-1 is at CP

Answer: (A)

The term is used when the drive delivers a perfect 1:1 ratio at the generator end of the system. In that setup, the two propellers are effectively on the same shaft speed with no gearing between the source and that point, so they rotate in lockstep and share the same torque and speed. This equalizes the loading on both props and helps maintain balanced thrust and smooth operation. If the unity point weren’t at that end, the two propellers wouldn’t experience identical speeds or torques, so this specific configuration wouldn’t apply.

The term is used when the drive delivers a perfect 1:1 ratio at the generator end of the system. In that setup, the two propellers are effectively on the same shaft speed with no gearing between the source and that point, so they rotate in lockstep and share the same torque and speed. This equalizes the loading on both props and helps maintain balanced thrust and smooth operation. If the unity point weren’t at that end, the two propellers wouldn’t experience identical speeds or torques, so this specific configuration wouldn’t apply.