Airworthiness Directive · Amendment 39-22408 · Stabilizers
De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes
This AD applies to De Havilland Aircraft of Canada Limited Model DHC-8-401 and -402 airplanes, certificated in any category, having serial numbers 4001 and 4003 through 4549 inclusive.
The FAA is adopting a new airworthiness directive (AD) for certain De Havilland Aircraft of Canada Limited Model DHC-8-401 and - 402 airplanes. This AD was prompted by reports of corrosion on the horizontal stabilizer lower center skin panel, including a finding of corrosion where the skin thickness had been substantially reduced, which affected design margins. This AD requires inspecting the horizontal stabilizer lower center skin panel for corrosion, and reworking, repairing, or replacing the lower center skin panel if necessary. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within 8,000 flight hours or 48 months, whichever occurs first, after the effective date of this AD: Inspect the horizontal stabilizer lower center skin panel for corrosion in accordance with Section 3.B. Part A of the Accomplishment Instructions of De Havilland Aircraft of Canada Limited Service Bulletin 84-55-05 Revision C, dated August 19, 2021. If any corrosion is found, before further flight, do the applicable actions specified in paragraph (g)(2) or (3) of this AD.
(2) If the corrosion is within the allowable repair limits as specified in Figure 5 Detail C of De Havilland Aircraft of Canada Limited Service Bulletin 84-55-05 Revision C, dated August 19, 2021, perform the corrosion rework in accordance with Section 3.B. Part B of the Accomplishment Instructions of De Havilland Aircraft of Canada Limited Service Bulletin 84-55-05 Revision C, dated August 19, 2021.
(3) If the corrosion is beyond the allowable repair limits as specified in Figure 5 Detail C of De Havilland Aircraft of Canada Limited Service Bulletin 84-55-05 Revision C, dated August 19, 2021, accomplish the action specified in paragraph (g)(3)(i) or (ii) of this AD.
(i) Replace the existing horizontal stabilizer lower center skin panel in accordance with Section 3.B. Procedure of the Accomplishment Instructions of De Havilland Aircraft of Canada Limited Service Bulletin 84-55-11, dated February 16, 2021.
(ii) Obtain and follow repair instructions using a method approved by the Manager, New York ACO Branch, FAA; or Transport Canada; or De Havilland Aircraft of Canada Limited's Transport Canada Design Approval Organization (DAO). If approved by the DAO, the approval must include the DAO-authorized signature.
