Propeller Safety Warnings
PLEASE FIND WARNINGS FROM A NUMBER OF PROPELLER MANUFACTURERS BELOW
PLEASE NOTE THE WARNINGS AND RECOMENDATIONS WOULD APPLY TO ALL TYPES & BRANDS OF PROPELLERS AVAILABLE FOR THE GENERAL AVIATION HOBBY.
APC Propeller Technical Advisories
All propellers are inherently dangerous. Model airplane propellers are especially dangerous. Model airplane propellers used in high performance racing are extremely dangerous. Model airplane engines designed and modified to achieve maximum operating capabilities create unpredictable and potentially severe loads, leading to various forms of potential propeller failure. Ignoring reasonable safeguards may likely be catastrophic. This concern is the motivation for the following discussion.
Warnings included with propellers are intended to protect consumers. They also protect manufactures against claims resulting from misuse of the product. Most products with potential for causing injury contain ample warnings about misuse. Some advertisements for products now contain warnings, even before the product is sold! There is a strong proliferation of warnings in most products having potential for creating injury or damage. This inundation of warnings may cause consumers to become inured to product warnings.
The warnings about propeller use must be taken seriously, especially for racing applications. It is very risky to assume that a racing propeller blade will not fail, especially when used with state-of-the-art racing engines. Yet, nevertheless, occasionally model aircraft operators are observed standing in the plane of propeller rotation of high performance racing engines running at full power. This is very frightening. The following information reinforces the assertion that dangers of misuse are very real.
Ideally, a product can be designed with credible knowledge of the environment (loads acting on the product) and capabilities of the product to withstand that environment (not fail). There is nothing ideal about designing a model airplane propeller because some major components of propeller loads are very uncertain. The principle load components acting on a propeller are:
- Centrifugal (from circular motion causing radial load)
- Thrust/drag (from lift and drag acting on blade sections)
- Torsional acceleration ( from engine combustion and/or pre-ignition)
- Vibration (from resonant frequencies or forced excitation)