AD 2020-26-13 Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

Models named: S-92A. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to Sikorsky Aircraft Corporation Model S-92A helicopters, certificated in any category, with the following installed: Horizontal stabilizer root fitting FWD (forward root fitting) part number (P/N) 92209-07111-101 or 92070-20125-101; or stabilizer strut fitting P/N 92209-07404-041, 92209-07403-041, or 92070-20117-041 installed on horizontal stabilizer assembly (stabilizer assembly) P/N 92070-20117-045, 92070-20117-046, 92070-20125-041, 92070-20125-042, 92070-20125-043, 92070-20125-044, 92205-07400-043, or 92205-07400-045.

Comply with this AD within the compliance times specified, unless already done.

(1) Within 50 hours time-in-service (TIS): (i) Determine the total hours TIS of the forward root fitting P/N 92209-07111-101 or 92070-20125-101. If the hours TIS of the forward root fitting is unknown, use the hours TIS of the stabilizer assembly instead. (A) If the forward root fitting has accumulated 7,900 or more total hours TIS, before further flight, remove the forward root fitting from service. (B) If the forward root fitting has accumulated less than 7,900 total hours TIS, before exceeding 7,900 hours TIS, remove the forward root fitting from service. (ii) Thereafter following paragraph (g)(1)(i) of this AD, remove the forward root fitting from service before accumulating 7,900 total hours TIS. (iii) For stabilizer assemblies with stabilizer strut fitting P/N 92070-20117-041 installed, perform the following actions: (A) Determine the total hours TIS of stabilizer strut fitting P/N 92070-20117-041. (B) If the stabilizer strut fitting has accumulated 19,100 or more total hours TIS, before further flight, remove the stabilizer strut fitting from service. (C) If the stabilizer strut fitting has accumulated less than 19,100 total hours TIS, before exceeding 19,100 total hours TIS, remove the stabilizer strut fitting from service. (iv) Thereafter following paragraph (g)(1)(iii) of this AD, remove the stabilizer strut fitting from service before accumulating 19,100 total hours TIS. (2) For helicopters with stabilizer strut fitting P/N 92209-07404-041 or 92209-07403-041 installed, within 50 hours TIS and thereafter at intervals not to exceed 50 hours TIS: (i) Remove the support strut and using a cheese cloth (or similar cloth) and isopropyl alcohol, clean the upper and lower support strut rod ends, horizontal stabilizer attachment fitting, and the tail rotor pylon attachment fitting. (ii) Using a 10X or higher power magnifying glass, a flashlight, and a mirror, visually inspect the hat bushing and both upper fittings and lower fittings for a crack, corrosion, fretting, deformation, and wear. If there is a crack, corrosion, fretting, deformation, or wear, before further flight, remove the hat bushing and both upper fittings and lower fittings from service. (iii) Using a 10X or higher power magnifying glass, a flashlight, and a mirror, visually inspect both upper and lower support strut rod ends, including lug and conical fitting, and both upper and lower attachment fittings on the stabilizer and pylon including the bushings for a crack, corrosion, fretting, deformation, and wear. If there is a crack, corrosion, fretting, deformation, or wear, before further flight, remove the upper and lower support strut rod ends, including lug and conical fitting, and both upper and lower attachment fittings on the stabilizer from service. (3) Within 250 hours TIS or one year, whichever occurs first, and thereafter at intervals not to exceed 250 hours TIS or one year, whichever occurs first: (i) Remove the stabilizer assembly and visually inspect each stabilizer attachment bolt and barrel nut set for corrosion, a crack, and damage to the threads. For the purposes of this inspection, damage may be indicated by uneven threads, missing threads, or cross-threading. (A) If there is corrosion within allowable limits, before further flight, treat for corrosion in accordance with FAA-approved procedures. (B) If there is corrosion that exceeds allowable limits, or a crack or damage to the threads, before further flight, remove the bolt and barrel nut set from service. (ii) Inspect the forward root fitting and the aft attachment fitting by: (A) Gaining access to the inside of the horizontal stabilizer. (B) Using Brulin Cleaner SD 1291 (or equivalent) and a low-lint cloth, remove all traces of sealing compound, oil, and dirt from the stabilizer mounting surfaces. (C) Using a 10X magnifying glass, inspect for any crack, wear, and corrosion. ( 1 ) If there is a crack, before further flight, remove the affected forward root fitting and the affected aft attachment fitting from service. ( 2 ) If there is wear or corrosion that exceeds allowable limits, before further flight, remove the affected forward root fitting and the affected aft attachment fitting from service. ( 3 ) If there is wear or corrosion within allowable limits, before further flight, treat for corrosion in accordance with FAA-approved procedures. (D) Visually inspect each attachment fitting bolt hole and fastener hole for a crack, wear, and corrosion. ( 1 ) If there is a crack, before further flight, remove the affected forward root fitting and the affected aft attachment fitting from service. ( 2 ) If there is wear or corrosion that exceeds allowable limits, before further flight, remove the affected forward root fitting and the affected aft attachment fitting from service. ( 3 ) If there is wear or corrosion within allowable limits, before further flight, treat for corrosion in accordance with FAA approved procedures. (E) Inspect for loose or working fasteners. If there is a loose or working fastener, before further flight, remove the fastener from service. (iii) As an alternative means to inspect for cracks in paragraphs (g)(3)(i) and (ii) of this AD, perform a florescent penetrate inspection (FPI). (iv) Visually inspect each forward and aft attachment fitting mating surface for wear of the abrasion-resistant Teflon coating and degradation. For the purposes of this inspection, degradation may be indicated by fretting. Refer to Figure 204, of S-92 Maintenance Manual, SA S92A-AMM-000, Temporary Revision 55-33, Task 55-11-01-210-004, dated March 24, 2020 (TR 55-33), for a depiction of the area to be inspected. For the purposes of this inspection, wear may be indicated by less than 100% coverage of the abrasion-resistant Teflon coating. If there is wear to the abrasion-resistant Teflon coating or degradation, before further flight: (A) Chemically strip the abrasion-resistant Teflon coating from the entire mounting pad in accordance with paragraph 7.A.(7)(a) of TR 55-33. (B) FPI or eddy current inspect for a crack. If there is a crack, before further flight, remove the stabilizer assembly from service. (C) If there is no crack, treat the affected area by applying alodine or equivalent. Apply abrasion-resistant Teflon coating in accordance with paragraphs 7.A.(7)(d) through (e) of TR 55-33. (4) Installing stabilizer strut fitting P/N 92070-20117-041 is a terminating action for the 50 hour TIS repetitive requirements in paragraph (g)(2) of this AD. (5) As of the effective date of this AD, do not install stabilizer assembly P/N 92205-07400-043, 92205-07400-045, or 92205-07400-047 on any helicopter.

This AD was prompted by incidents of fatigue cracks in a forward root fitting and life limit recalculations for forward root fitting P/N 92209-07111-101 and 92070-20125-101. The FAA is issuing this AD to prevent a forward root fitting from remaining in service beyond its life limit, detect fatigue cracking in a forward root fitting, and prevent increased load and stress cracking in the stabilizer root fitting aft. The unsafe condition, if not addressed, could result in failure of a stabilizer root fitting, separation of the stabilizer assembly from the helicopter, and subsequent loss of control of the helicopter.

None.