The Federal Aviation Administration (FAA) has issued an Airworthiness Directive (AD) for Air Tractor AT-802 and AT-802A airplanes with Wipaire, Inc. Wipline 10000 Amphibian Floats installed per Supplemental Type Certificate (STC) # SA01795CH, as well as previously floated aircraft that have been converted back to landplane configuration per the same STC. 

 

During routine maintenance, an Air Tractor Model AT–802 airplane was found with a hairline crack in the flange of the right forward horizontal stabilizer spar. The airplane had the above STC installed and is used in fire-fighting missions, which can propagate crack growth more rapidly. Of the 144 Air Tractor Model AT–802 and AT–802A airplanes that have this STC, 45 have been inspected, and 24 of those inspected had cracks found in at least one forward horizontal stabilizer spar. The cracking is in the forward horizontal stabilizer spar bend radius located at the STC finlet mounting locations. 

 

This AD, effective August 9, 2023, requires inspecting both forward horizontal stabilizer spars for cracks, replacing any which are found to be cracked, and reporting the inspection results to the FAA. Wipaire, Inc. Service Letter 253, Revision B, dated July 27, 2023 specifies inspection procedures and compliance windows. Depending on STC configuration installed, compliance may be required within 3-15 days or 24 hours time-in-service (TIS), whichever occurs later. Re-inspections are required every 200 hours TIS.  

 

The FAA implemented immediate adoption of this AD because cracks in the forward horizontal stabilizer spars could lead to structural failure of the horizontal tail with consequent loss of control of the airplane. Airplanes with the affected STC installed are used in fire-fighting missions and put frequent high repetitive fatigue loads in this area at a high utilization rate. View the AD here.