Airworthiness Directive · Amendment 39-18114 · Fuselage main, longeron/stringer
Bell Helicopter Textron Canada Helicopters
This AD applies to Bell Helicopter Textron Canada (BHTC) Model 407 helicopters, with a serial number 53000 through 53900, 53911 through 54061, and 54300, with an upper left longeron assembly (longeron assembly), part number (P/N) 206-031-314-037, 206-031-314-177, or 206-031-314-219B, installed, certificated in any category.
We are adopting a new airworthiness directive (AD) for Bell Helicopter Textron Canada (BHTC) Model 407 helicopters. This AD requires inspecting the aft fuselage upper skin (upper skin) for a crack and the upper left longeron assembly (longeron assembly) for a crack, corrosion, or defect. This AD requires replacing or repairing a part or section, depending on the inspection's outcome. This AD was prompted by reports of cracks in the upper left-hand longeron. This AD's actions are intended to prevent failure of the longeron assembly or the upper skin, which could lead to a structural failure and loss of helicopter control.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
Within 50 hours time-in-service (TIS), or prior to reaching 1,250 hours TIS since new, whichever occurs later, visually inspect the helicopter's aft fuselage upper skin (upper skin) for a crack using a 10X or higher power magnifying glass.
(1) If there is a crack in the upper skin, before further flight, remove the skin and inspect the longeron assembly, paying attention to the upper flange, for a crack, corrosion, or other damage using a 10X or higher power magnifying glass.
(i) If there are no cracks, corrosion, or other damage in the longeron assembly, before further flight, replace the upper skin with an airworthy upper skin. Repeat the inspection of the longeron assembly at intervals not to exceed 50 hours TIS.
(ii) If there is a crack, corrosion, or other damage in the longeron assembly, before further flight:
(A) Repair the longeron assembly or replace it with an airworthy longeron assembly, part number (P/N) 206-031-314-237B, and reinstall the upper skin or replace it with an airworthy upper skin.
(B) Install three external strap doublers in accordance with Part III, paragraphs 5 through10 of Bell Helicopter Alert Service Bulletin 407-11-95, Revision C, dated April 20, 2012 (ASB).
(C) Repeat the inspection of the longeron assembly at intervals not to exceed 50 hours TIS.
(2) If there is no crack in the upper skin, within 10 hours TIS, visually inspect the longeron assembly using a 10X or higher power magnifying glass for a crack, corrosion, or other damage.
(i) If there is a crack, corrosion, or other damage in the longeron assembly, before further flight:
(A) Repair the longeron assembly or replace it with an airworthy longeron assembly, P/N 206-031-314-237B.
(B) Install three external strap doublers in accordance with Part III, paragraphs 5 through 10 of the ASB.
(C) Repeat the inspection of the upper skin and longeron assembly at intervals not to exceed 50 hours TIS.
(ii) If there are no cracks, corrosion, or other damage in the longeron assembly, repeat the inspection of the upper skin and longeron assembly at intervals not to exceed 50 hours TIS.
(3) Replacing the longeron assembly with longeron assembly, P/N 206-031-314-237B, and installing three external strap doublers constitutes terminating action for this AD.
(4) If there is no crack in the upper skin and there is no crack, corrosion, or other damage in the longeron assembly, you may install three external strap doublers in accordance with Part III, paragraphs 5 through 10 of the ASB. This option extends the recurring 50 hours TIS inspection interval to 150 hours TIS.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
