Spinner Approvals

[DaveF]

Can someone help me with the 170B TCDS?

The Propellers and Propeller Accessories are listed on page 7. The first prop, the McCauley 1A170, has two spinners listed. The first (0550101, the skullcap type) is listed as "eligible" for all 170s, while the second (the larger type) is listed with weight and arm. Propeller (b) only has one spinner, while (c), (d), (e) and (f) have none. See snippet below.

My questions are:
1. What does "eligible" mean? Optional? Does it mean that for the McCauley, either type can be used?
2. If a spinner is listed, must one be used?
3. If none is listed, may one be used?
4. Why is the weight listed for one but not the other?



Thanks,
Dave

[GAHorn]

...My questions are:
1. What does "eligible" mean? Optional? Does it mean that for the McCauley, either type can be used?
2. If a spinner is listed, must one be used?
3. If none is listed, may one be used?
4. Why is the weight listed for one but not the other? ...Thanks,
Dave

Not an authoritative opinion, but I believe:

Eligible means not required equipment, but may be installed without additional approval.

The spinners are not mandatory. (see previous)

Only approved spinners may be used. (Example: The MDM prop is an approved alternative prop replacing the DM, and the approved spinners may used on the alternate.)

These spinners do not fit the Aermatic/Koppers prop. That prop has movable counterweights that do not clear the spinners.

The weight of the skullcap is negligible (less than one pound) and is not considered to affect the wt/bal of the aircraft.