Airworthiness Directive · Amendment 39-17551 · Tail rotor head
Eurocopter Deutschland GmbH Helicopters
This AD applies to Model BO-105A, BO-105C, BO-105S, and BO-105LS A-1 helicopters, with a tail rotor control lever (lever), part number (P/N) 105-317231, 105-317365, 105-31736, 105-31767, 105-31728, or 1121-31730, with tail rotor balance weight (weight) P/N 117-31715.01, 117-31715.02, 105-31728.03, 105-31732.07, or 105-31732.08; Model BO-105LS A-3 helicopters, with lever P/N 105-31736 or 105-31767, with weight P/N 117-31715.01, 117-31715.02, B642M1011 201, or 105-317171.10; and Model MBB-BK 117 A-1, MBB-BK 117 A-3, MBB-BK 117 A-4, MBB-BK117 B-1, MBB-BK 117 B-2, and MBB-BK 117 C-1 helicopters, with lever P/N 117-31730, 117-317361, or 105-31736, with weight P/N 117-31714.07, 117-31715.01, 117-31720.01, or 117-31730.02, certificated in any category.
We are adopting a new airworthiness directive (AD) for Eurocopter Deutschland GmbH (ECD) Model BO-105A, BO-105C, BO-105S, BO- 105LS A-1, BO-105LS A-3, MBB-BK 117 A-1, MBB-BK 117 A-3, MBB-BK 117 A- 4, MBB-BK 117 B-1, MBB-BK-117 B-2, and MBB-BK 117 C-1 helicopters to require inspections for corrosion or thread damage to each tail rotor balance weight (weight) and each tail rotor control lever (lever). This AD was prompted by a European Aviation Safety Agency (EASA) AD and a Transport Canada Civil Aviation (TCCA) AD, both issued based on a report that corrosion was detected on a weight in the area of the attachment thread on a model BO-105 helicopter. The actions of this AD are intended to detect corrosion and thread damage in the threaded area of the weight and lever, and to prevent failure of a weight or lever, separation of tail rotor parts, severe vibration, and subsequent loss of control of the helicopter.
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 100 hours time-in-service (TIS) or 2 months, whichever occurs first, and thereafter at intervals not to exceed 600 hours TIS or 48 months, whichever occurs first:
(1) Remove the weights from the lever as depicted in Figure 1 of Eurocopter Alert Service Bulletin (ASB) No. ASB-MBB-BK117-30-113, dated September 23, 2008; ASB No. ASB BO105-30-116, dated September 23, 2008; or ASB No. ASB BO 105 LS 30-12, dated December 12, 2008; as applicable to your model helicopter. Apply marks to the weights before they are removed in order to be able to re-establish the correct assignment and the old installation position towards the lever when the weights are installed.
(2) Visually inspect each weight and lever for corrosion and damage in the threaded areas as depicted in Figure 2 of ASB No. ASB-MBB-BK117-30-113, dated September 23, 2008; ASB No. ASB BO105-30-116, dated September 23, 2008; or ASB No. ASB BO 105 LS 30-12, dated December 12, 2008; as applicable to your model helicopter.
(i) If there is no corrosion or thread damage on either the weight or lever, before further flight, reinstall the weight by following paragraph (e)(3) of this AD.
(ii) If there is corrosion or thread damage on the threaded portion of a weight:
(A) If the total area of corrosion or thread damage, or both, covers less than 25 percent of the length of the threaded area, the weight can be threaded (screwed) onto the lever, and the cylindrical mating surface has no damage, before further flight, remove the corrosion and reinstall the weight by following paragraph (e)(3) of this AD.
(B) If the total area of corrosion or thread damage, or both, covers 25 percent or more of the length of the threaded area, the weight cannot be threaded (screwed) onto the lever, or the cylindrical mating surface has damage, before further flight, replace the weight with an airworthy weight by following paragraph (e)(3) of this AD.
(iii) If there is corrosion or thread damage on the threaded portion of the lever, polish out the corrosion and thread damage using a polishing cloth 600 and:
(A) If the thread depth does not exceed 0.3 millimeter (mm) and the diameter of the lever in the area before the threaded area is not less than 9.95 mm after polish out, before further flight, install airworthy weights to the lever by following paragraph (e)(3) of this AD.
(B) If the thread depth is 0.3 mm or greater or the diameter of the lever in the area before the threaded area is less than 9.95 mm after polish out, before further flight, replace the lever with an airworthy lever.
(3) Apply corrosion preventive paste onto the thread of the lever and install weights to the lever as depicted in Figure 1 of ASB No. ASB-MBB-BK117-30-113, dated September 23, 2008; ASB No. ASB BO105-30-116, dated September 23, 2008; or ASB No. ASB BO 105 LS 30-12, dated December 12, 2008; as applicable to your model helicopter. Ensure during installation of the weights that the weights are correctly assigned and installed to the control lever in accordance with the applied marks.
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.
