Airworthiness Directive · Amendment 39-17171 · Main rotor head
Bell Helicopter Textron, Inc. (Bell) Helicopters
This AD applies to Model 204B, 205A, 205A-1, 205B, and 212 helicopters, with a main rotor yoke (yoke), part number (P/N) AAI-4011-102 (all dash numbers), ASI-4011-102 (all dash numbers), or 204-011-102 (all dash numbers), installed, certificated in any category.
We are superseding four airworthiness directives related to the main rotor yoke (yoke) on the Bell Model 204B, 205A, 205A-1, 205B, and 212 helicopters, to retain certain inspections and certain life limits, to require an increased inspection frequency for certain yokes, and to expand these inspections and retirement lives to other yokes. This airworthiness directive is prompted by past reports of cracks in the yoke, another recent report of a cracked yoke, and the decision that other yokes, approved based on identicality, need to be subject to the same inspection requirements and retirement lives. The actions are intended to detect a crack in a yoke to prevent failure of the yoke, 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.
(1) For helicopters with yoke, P/N AAI-4011-102 (all dash numbers) and ASI-4011-102 (all dash numbers), installed, within 100 hours time-in-service (TIS):
(i) Create a component history card or equivalent record for each yoke.
(ii) Determine the model for each helicopter on which the yoke has been installed from the time the yoke had zero hours TIS.
(iii) In accordance with the rate per hour categories shown in Table 1 to paragraph (f) of this AD, categorize the accumulated “Factored Hours TIS” on each yoke by determining the types of operation AND the rate per hour of external load lifts for each hour TIS accumulated on each yoke. One external load lift occurs each time the helicopter picks up an external load and drops it off. For determining the proper rate per hour category for external load operations, any external load lift in which the helicopter achieves a vertical altitude difference of greater than 200 feet indicated altitude between the pickup and drop-off point counts as two external load lifts.
| Helicopter model | Types of operation | Rate per hour of external load lifts and takeoffs | Unfactored hours TIS | Hours TIS factor | Factored hours TIS on yoke (unfactored hours TIS × hours TIS factor) |
|---|---|---|---|---|---|
| Yokes installed on any Model 204B, 205A, or 205A-1 helicopter | All Operations | All | 120 | 1 | 120 |
| Yokes installed on any Model 205B or 212 helicopter | External Load Operations | 1 to 5 | 105 | 1 | 105 |
| 5.1 to 8 | 1.5 | ||||
| 8.1 to 12 | 2 | ||||
| 12.1 to 18 | 3 | ||||
| 18.1 to 32 | 170 | 5 | 850 | ||
| 32.1 to 48 | 7 | ||||
| more than 48 | 9 | ||||
| Unknown | 50 | 7 | 350 | ||
| Internal Load Operations | All Takeoffs | 2,025 | 1 | 2,025 | |
| Total Factored Hours TIS on Yoke (Summation of the Factored Hours TIS) | 3,450 |
(iv) By reference to Table 1 to paragraph (f) of this AD, enter the “Unfactored Hours TIS” for each category as determined by paragraph (f)(1)(iii) of this AD. Calculate the “Factored Hours TIS” by multiplying the “Unfactored Hours TIS” by the “Hours TIS Factor.” Determine the accumulated “Total Factored Hours TIS” on each yoke by adding the factored hours TIS for each type of operation and helicopter model. Tracking the Total Factored Hours TIS is only for establishing a retirement life and not for tracking inspection intervals.
(v) Record the accumulated Total Factored Hours TIS on the component history card or equivalent record for each yoke.
(vi) Continue to factor the hours TIS for each yoke by following paragraph (f)(1)(ii) through (f)(1)(iv) of this AD, and record the additional factored hours TIS on the component history card or equivalent record.
(2) For helicopters with yoke, P/N 204-011-102 (all dash numbers), installed, before further flight:
(i) For hours TIS accumulated before the effective date of this AD, calculate and record the Total Factored Hours TIS as follows:
(A) For the Model 212 helicopters, 1 hour TIS in which passenger or internal cargo was carried equals 1 factored hour TIS; 1 hour TIS where more than 4 external load lifts occurred equals 5 factored hours TIS.
(B) For the Model 204 and 205 series helicopters, 1 hour TIS equals 1 factored hour TIS.
(ii) For hours TIS accumulated after the effective date of this AD, calculate and record the factored hours TIS on the yoke in accordance with the requirements of paragraphs (f)(1)(i) thorough (f)(1)(vi) of this AD.
(3) Revise the Airworthiness Limitations section of the applicable maintenance manuals or the Instructions for Continued Airworthiness (ICAs) by establishing a new retirement life of 3,600 Total Factored Hours TIS for each yoke, P/N AAI-4011-102 (all dash numbers), ASI-4011-102 (all dash numbers), or 204-011-102 (all dash numbers), by making pen and ink changes or inserting a copy of this AD into the Airworthiness Limitations section of the maintenance manual or ICAs.
(4) Record a life limit of 3,600 Total Factored Hours TIS for each yoke, P/N AAI-4011-102 (all dash numbers), ASI-4011-102 (all dash numbers), or 204-011-102 (all dash numbers), on the component history card or equivalent record.
(5) Within 100 hours TIS or 600 hours TIS since the last magnetic particle inspection (MPI) of the yoke, whichever occurs later, and thereafter at intervals not to exceed 600 hours TIS, for any yoke installed on any Model 205B or 212 helicopter:
(i) Remove the yoke from the main rotor hub assembly (hub). Using a 5-power or higher magnifying glass, visually inspect each pillow block bushing hole, spindle radius, and center section web for any corrosion or mechanical damage.
(ii) Perform an MPI of each yoke for a crack.
(6) Within 100 hours TIS or 2,400 hours TIS since the last MPI of the yoke, whichever occurs later, and thereafter at intervals not to exceed 2,400 hours TIS, for any yoke installed on any Model 204B, 205A, or 205A-1 helicopter:
(i) Remove the yoke from the hub. Using a 5-power or higher magnifying glass, visually inspect each pillow block bushing hole, spindle radius, and center section web for any corrosion or mechanical damage.
(ii) Perform an MPI of each yoke for a crack.
(7) Before further flight, replace each yoke with an airworthy yoke if:
(i) The yoke has 3,600 or more Total Factored Hours TIS; or
(ii) The Total Factored Hours TIS for the yoke is unknown and cannot be determined; or
(iii) The yoke has any corrosion or mechanical damage that exceeds any of the maximum repair damage limits; or
(iv) The yoke has a crack.
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.
