Hartzell HC-D2MV20-3 Series Owner's Manual And Logbook page 51

B. Propeller Model HC-D3(MV,V)20-6( ). Refer to Figure 2-3.
(1) This propeller model uses manual control and is reversing.
The basic components of this propeller assembly consist
of a propeller, a hydraulic unit, and a valve assembly.
(2) A blade angle range up to 33 degrees enables reverse
thrust operation for ground or water handling.
(3) The hydraulic unit is designed so the cylinder will attach to
engines with an SAE 20 splined thrust plate that uses six
attachment points. This requires six holes in the cylinder to
receive six studs from the engine and is secured in place
with one nut on each stud.
DESCRIPTION AND OPERATION
Propeller Owner's Manual
140
61-00-40
Page 2-11
Rev. 2 Jun/12