ICING PROBLEMS in Aircraft Induction Systems 420081

HEAT and alcohol are the most common de-icing mediums, but they offer the disadvantages of loss in power and increased weight. The protected air intake is effective if the rate of water ingestion can be reduced during precipitation and the air temperature raised high enough to be effective during severe icing conditions.
The ideal induction system is one which requires none of these, and work is being done in hopes of reaching this goal.
The research program was initiated by the Special Subcommittee on Induction System De-Icing of the NACA. The project was set up at the Bureau of Standards, as they were well equipped to handle this sort of work. The apparatus is described and the method outlined for establishing the icing conditions.
Types of induction ice are described and pictures of formations found during tests are shown. Preliminary results are summarized as follows:
  1. 1.
    The rate of ice accretion was roughly proportional to the rate of water ingestion.
  2. 2.
    Through the lower temperature range, the smaller the droplet size, the faster the rate of ice accretion for a given rate of ingestion.
  3. 3.
    The most dangerous condition was found to be around 30 F air temperature and small droplet size.
Design criteria are set up as a result of this preliminary work which are the basis of rates for making a system which would be substantially ice-free.
Some new developments are described, such as two types of flush bulb thermometer and two icing indicators which would give the delayed action favored by the industry.
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