Air Tractor AT-802 SAIB: CE-09-28

FAA Aircraft Certification Service
SPECIAL AIRWORTHINESS INFORMATION BULLETIN

SUBJ: Fuselage Main, Longeron/Stringer: Float Equipped Air Tractor AT-802 SAIB: CE-09-28
and AT-802A Airplanes - Periodic Inspection and Repair for Aft Fuselage Diagonal Tubes

Date: May 12, 2009
This is information only. Recommendations aren’t mandatory.

Introduction
This Special Airworthiness Information Bulletin (SAIB) informs you, a registered owner or operator, of a Air Tractor Model AT-802 and AT-802A airplane. The SAIB specifically informs you that the aft fuselage diagonal tube, part number 11029-10, may crack on airplanes prior to serial number - 0259 when equipped with floats. The FAA has received reports of cracked diagonal tubes only on float equipped airplanes.
At this time, this airworthiness concern is not considered an unsafe condition that would warrant an airworthiness directive (AD) action under Title 14 of the Code of Federal Regulations (14 CFR part 39).

Background
In August 2007, Air Tractor issued Snow Engineering Co. Service Letter #266 to address cracks in AT-802 and AT-802A aft fuselage diagonal tubes, part number 11029-10. The Service Letter
provides for one-time inspection for cracks, recurring inspection of the tube for float equipped
airplanes, a reporting requirement to the factory for any cracks found, and a procedure to install a stronger tube as corrective action to cracked tubes and termination of the inspections. The Service Letter applies to AT-802 and AT-802A airplanes prior to serial number -0259.
Since that time, Air Tractor has received further service information supporting that the problem is isolated to float equipped AT-802 and AT-802A airplanes only. No cracks were reported for nonfloat equipped airplanes. To date, 40 affected AT-802 and AT-802A airplanes have been modified with floats for operating on water. Air Tractor reports that 10 of those 40 airplanes have been found with the aft fuselage diagonal tube cracked.
Air Tractor believes the cracks develop as a result of the high power requirements associated with operating float equipped airplanes, and from operation in rough waters. The factory installed stronger diagonal tubes in production airplanes starting at serial number -0259 to address this problem. The original tube material was 7/8” outside diameter (OD) x .035” wall thickness (WT); the replacement tube is 7/8” OD x .058” WT. Note that the part number was not changed. Operators will need to confirm which tubes are installed by aircraft serial number effectivity and review of the aircraft logbook for whether the tube has already been replaced.

Recommendations
The FAA recommends that you inspect your float equipped AT-802 and AT-802A airplanes prior to serial number -0259 that still have the original .035” WT part number 11029-10 diagonal tube. You should perform the initial inspection within the next 25 flight hours in accordance with Snow Engineering Co. Service Letter #266, dated 8/22/07. If you have the .035 WT tube installed, we also recommend that you repeat the inspection at every 100 flight hours and during the annual inspection until the stronger .058” WT replacement tube is installed.
Replace any cracked diagonal tube prior to continued flight with the thicker .058” part number
11029-10 replacement tube. We also recommend, if not already done, that you replace the original .035” WT tube with the .058” WT tube by the next major maintenance interval to eliminate the probability of cracking and need for further inspections. Failure to detect and replace a cracked diagonal tube can result in a reduction in structural safety margins.

For Further Information Contact
Andrew McAnaul, Aerospace Engineer, 10100 Reunion Place, Ste. 650, San Antonio, TX 78216;
phone: (210) 308-3365; fax: (210) 308-3370; e-mail: Andrew.Mcanaul@faa.gov.

For Related Service Information Contact
Air Tractor, Inc., P.O. Box 485, Olney, TX 76374; phone: (940) 564-5616; fax: (940) 564-5612.