Draft AC Offers OEMs Guidance on Icing

 - September 30, 2010, 5:43 AM

The FAA’s Draft Advisory Circular 20-147A released last month provides new guidance to aircraft manufacturers on compliance with regulations covering engine ­induction system icing and engine installation ice requirements. Comments on the draft AC are due by November 1. One of the key changes in the draft AC is mixed phase or ice ­crystal icing conditions, which “has caused more than 100 turbine engine power losses,” according to the FAA. These conditions “occur when supercooled liquid water droplets and ice particles coexist in a cloud, often around the outskirts of a deep convective cloud formation.” This is the first time the FAA has introduced compliance methodologies for these conditions and is likely a response to instances of power rollbacks that have caused engine flameouts in at least three Beechjets. The FAA is also recommending that ice-detection systems be evaluated for TAT probe ­malfunctions during icing events. (See article on page 1.)