If you’re interested in reducing propeller noise, take a tip from an airport and a glider operator in California.
At Truckee-Tahoe Airport (TRK), airport management and glider operator Soar Truckee have been working together to reduce noise from glider tow planes, most of which comes from the tow planes’ propellers and exhaust systems.
A Hoffman four-bladed propeller was installed on one of Soar Truckee’s airplanes to assess its effectiveness, replacing a stock two-bladed McCauley prop. Initial assessments by airport staff show as much as a 12 dbA reduction, thanks to shorter blades and, thus, lower tip speeds. The propellers have been used for nearly 10 years in Europe.
A glider operation in Boulder, Colo., also has had great success with these propellers. Boulder is a high-altitude airport similar to Truckee-Tahoe, where density altitude is a serious consideration. The Boulder tests showed an even more substantial decrease in noise (18dbA) and no significant performance loss.