SENSENICH PROPELLER CO.
SERVICE BULLETIN NO. R-16
August 1, 1988
TO:
FAA APPROVED PROPELLER REPAIR STATIONS
SUBJECT:
IMPROVED PROPELLER BLADE-ANGLE DISTRIBUTION
PROPELLER MODEL AFFECTED:
69CK SERIES
AIRCRAFT MODEL AFFECTED:
CESSNA 150 SERIES with SENSENICH
PROPELLER
An improved blade-angle distribution. for SENSENICH 69CK series
propellers installed on CESSNA 150 serIes aircraft, has been developed. It
has been found that incorporating the revised angle distribution makes
possible a reduction of 2 inches in propeller pitch, improving takeoff and
climb without experiencing a reduction of cruise performance. Test data
shows that, with a "50" pitch (52 pitch is standard on CESSNA 150
airplanes) and the revised blade-angle distribution, time to lift-off
may be reduced by about 15%; rate-of-climb may be increased by a factor of
about 9%; and the airplane upon which the prototype propeller was tested
showed an 85 knot cruise at 10 rpm less than was required with the standard
propeller. (For those interested in "why" a revised blade-angle
distribution and a decrease in the pitch of a propeller at the 3/4 radius
blade station could improve takeoff and climb and not affect cruise, more
accurate knowledge of the natural flow in front of the aircraft cowling
makes it possible to design a propeller to waste less energy)
This revision in blade-angles may be incorporated by FAA approved
propeller repair stations when any propeller of the 69CK series is
reconditioned (overhauled) . Incorporation of the blade-angle
distribution (shown on page 13 of SENENICH repair manual SPRM 590) , dated
1 August 1988, shall be indicated by addition of a suffix "L" after the
propeller pitch identification on the hub face (with steel stamp)
and on the identification decal (with ink pen) . All new and
reconditioned propellers obtained from the SENSENICH facility will
incorporate the revised blade-angle distribution and have an "L" suffix
included after the pitch identification. An example of the model
designation of a propeller which incorporates the revised blade-angle
distribution is "69CK-0-50L". This propeller is 69 inches diameter and 50
inches pitch, incorporating the "L" revision to the blade-angle distribution.
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