Airworthiness Directive · Amendment 39-17606 · Tail rotor blades
MD Helicopters, Inc., Helicopters
This AD applies to MD Helicopters, Inc. (MDHI), Model 369A, 369D, 369E, 369H, 369HE, 369HM, 369HS, 369F and 369FF helicopters with a tail rotor blade (blade) part number (P/N) 369D21640-501, 369D21640-503, 369D21641-501, 369D21641-503, 369D21642-501, 369D21642-503, 369D21643-501, or 369D21643-503 installed, or with a Helicopter Technology Company blade P/N 500P3100-101, 500P3100-301, 500P3300-501, or 500P3500-701 installed, certificated in any category.
We are superseding Airworthiness Directive (AD) 2003-08-51 for MD Helicopters, Inc. (MDHI), Model 369A, 369D, 369E, 369H, 369HE, 369HM, 369HS, 369F and 369FF helicopters with certain MDHI or Helicopter Technology Company (HTC) tail rotor blades installed. AD 2003-08-51 required reducing the retirement life of each tail rotor blade (blade), performing a one-time visual inspection of each blade's pitch horn (pitch horn) for a crack or corrosion, and replacing any cracked blade or any blade that has exceeded its retirement life with an airworthy blade. AD 2003-08-51 also required reporting information to the FAA within 24 hours following the one-time inspection. Since we issued AD 2003-08-51, an accident in England prompted an investigation that showed corrosion on the blade's pitch horn that had not been detected under the paint. This new AD retains some of the requirements of AD 2003-08-51 and also requires paint removal for all pitch horn inspections, inspecting for pitting and the shot peen surface's condition in addition to cracks and corrosion, and adds certain part- numbered blades to the applicability. These actions are intended to prevent a pitch horn from cracking, leading to vibration, loss of tail rotor pitch control, and subsequent loss of tail rotor and 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.
(1) Before further flight, for each applicable blade, revise the Airworthiness Limitations section of the maintenance manual to reflect that the blade has a retirement life of 400 hours time-in-service (TIS).
(2) For helicopters with an applicable blade installed that has 390 through 700 hours TIS, within 10 hours TIS, replace the blade with an airworthy blade.
(3) For all other applicable helicopters, within 60 days, and thereafter at intervals not to exceed one year, remove the paint from the blade pitch control arm in accordance with the Accomplishment Instructions, Section 2.A.(1) through 2.A.(3), of MDHI Service Bulletins SB369D-210, SB369E-105, SB369F-091, and SB369H-252, all dated November 21, 2011, as applicable to your model helicopter.
(i) Using a 10X or higher power magnifying glass, inspect all four sides and the pocket of the blade pitch control arm for a crack, pitting, or corrosion and for the condition of the dimpled shot peen surface by referring to Figure 1 of MDHI Service Bulletins SB369D-210, SB369E-105, SB369F-091, and SB369H-252, as applicable to your model helicopter, and by reviewing the rotorcraft maintenance records to determine whether rework was done in this area.
(ii) If there is pitting, corrosion, a crack, blending or removal of any of the dimpled shot peen surface, or any indication that the shot peen has not been done, replace the blade with an airworthy blade.
(iii) If there is no pitting, corrosion, cracks, or blending or removal of any of the dimpled shot peen surface, refinish the stripped pitch control arm in accordance with the Accomplishment Instructions, Section 2.A.(6) through 2.A.(7), of MDHI Service Bulletins SB369D-210, SB369E-105, SB369F-091, and SB369H-252, as applicable to your model helicopter.
