• Version
• 154 Downloads
• 1.48 MB File Size
• 1 File Count
• November 4, 2016 Create Date
• November 4, 2016 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Drag and Cooling with Various Forms of Cowling for a ''Whirlwind'' Engine in a Cabin Fuselage

The National Advisory Committee for Aeronautics has under—
taken an investigation, in the 20~foot Propeller Research Tunnel
at Langley Field, on the cowling of radial air—cooled engines.

A portion of the investigation has been completed, in which sev-
eral forms and degrees of cowling were tested on a Wright "Whirl—
wind" J—5 engine mounted in the nose of a cabin fuselage. The
cowlings varied from the one extreme of an entirely exposed en—
gine to the other in which the engine was entirely enclosed.
Cooling tests were made and each cowling modified if necessary
until the engine cooled approximately as satisfactorily as when
it was entirely exposed. Drag tests were then made with each
form of cowling, and the effect of the cowling on the propulsive
efficiency determined with a metal propeller.

The propulsive efficiency was found to be practically the
same with all forms of cowling. The drag of the cabin fuselage
with uncowled engine was found to be more than three times as
great as the drag of the fuselage with the engine removed and
nose rounded. The conventional forms of cowling, in which at
least the tops of the cylinder heads and valve gear are exposed,
reduce the drag somewhat, but the cowling entirely covering the
engine reduces it 8.6 times as much as the best conventional one.
The decrease in drag due to the use of spinners proved to be
almost negligible.

The use of the cowling completely covering the engine seems
entirely practical as regards both cooling and maintenance under
service conditions. It must be carefully designed, however, to
cool properly. With cabin fuselages its use should result in a
substantial increase in high speed over that obtained with pres-
ent forms of cowling on engines similar in contour to the J~5