Airworthiness Directive · Amendment 39-22212 · Propeller hub section
Hoffmann GmbH & Co. KG Propellers
This AD applies to Hoffmann GmbH & Co. KG (Hoffmann) model HO-V 72 propellers.
The FAA is superseding Airworthiness Directive (AD) 2021-23-17 for all Hoffmann GmbH & Co. KG (Hoffmann) model HO-V 72 propellers. AD 2021-23-17 required amending the existing aircraft flight manual (AFM) by inserting abnormal propeller vibration instructions, visual inspection and non-destructive test (NDT) inspection of the propeller hub and, depending on the results of the inspections, replacement of the propeller hub with a part eligible for installation. Since the FAA issued AD 2021-23-17, further investigation by the manufacturer revealed that cracks found on propeller hubs likely resulted from propeller blade retention nuts that were not tightened using published service information during blade installation. This AD is prompted by reports of cracks at different positions on two affected propeller hubs. This AD retains the required actions of AD 2021-23-17. This AD also requires a maintenance records review and, depending on the results of the maintenance records review, tightening of each propeller blade retention nut to specific torque values. Depending on the results of the maintenance records review, this AD requires physically inspecting the propeller blade for shake. If any axial play is detected during the performance of the inspection, this AD requires the removal of the propeller from service and the performance of an NDT inspection of the propeller hub, and depending on the NDT inspection results, replacement of the propeller hub with a part eligible for installation. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Before the next flight after December 22, 2020 (the effective date of AD 2020-25-05, Amendment 39-21347 (85 FR 78702, December 7, 2020)), amend the emergency or abnormal procedures section of the existing aircraft flight manual by inserting this text: “Abnormal propeller vibrations: As applicable, reduce engine RPM.”
(2) Before the next flight after January 10, 2022 (the effective date of AD 2021-23-17), and thereafter, before the next flight after any flight where abnormal propeller vibrations have been experienced, visually inspect propeller hub HO-V 72 () ()-()-() for cracks using paragraph 2.1 of Hoffmann Propeller GmbH & Co. KG Service Bulletin SB E53, Rev. D, dated February 18, 2021 (Hoffmann Propeller SB E53 Rev. D).
(3) Within 20 flight hours (FHs) after January 10, 2022 (the effective date of AD 2021-23-17), perform a non-destructive test (NDT) inspection of propeller hub HO-V 72 () ()-()-() using paragraph 2.3 of Hoffmann Propeller SB E53 Rev. D.
(4) During each overhaul of propeller hub HO-V 72 () ()-()-() after January 10, 2022 (the effective date of AD 2021-23-17), perform an NDT inspection using paragraph 2.3 of Hoffmann Propeller SB E53 Rev. D.
(5) Within 30 days after the effective date of this AD, review the maintenance records to confirm the propeller blade retention nuts were tightened at the last in-shop maintenance visit to the torque values in paragraph 5 of Hoffmann Propeller Service Bulletin SB057 C, dated February 22, 2022 (Hoffmann Propeller SB057 C).
(6) If, during the records review required by paragraph (g)(5) of this AD, it is determined that the propeller blade retention nuts were not tightened to the torque values in paragraph 5 of Hoffmann Propeller SB057 C, or it cannot be confirmed if the propeller blade retention nuts were tightened to the torque values in paragraph 5 of Hoffmann Propeller SB057 C, perform the following actions:
(i) Within 90 FHs after the effective date of this AD, tighten each propeller blade retention nut to the torque values in paragraph 5 of Hoffmann Propeller SB057 C, using paragraphs 6 and 7 of Hoffmann Propeller Service Bulletin SB059 B, dated February 23, 2022.
(ii) Before the next flight after the effective date of this AD and, thereafter, before each flight until the propeller blade retention nut is tightened to the torque values in paragraph 5 of Hoffmann Propeller SB057 C, as required by paragraph (g)(6)(i) of this AD, confirm that there is no axial play in the blade retention system by inspecting the propeller blade for shake. If any axial play is detected, remove the propeller from service and perform an NDT inspection of the propeller hub using paragraph 2.3 of Hoffmann Propeller SB E53 Rev. D.
(7) If, during any inspection required by paragraph (g)(2), (3), (4) or (6)(ii) of this AD, any crack is detected, replace propeller hub HO-V 72 () ()-()-() with a part eligible for installation.
For the purpose of this AD, a “part eligible for installation” is a propeller hub HO-V 72 () ()-()-() with zero hours time since new, or a propeller hub HO-V 72 () ()-()-() that has passed an NDT inspection using paragraph 2.3 of Hoffmann Propeller SB E53 Rev. D.
(1) Sending the propeller to Hoffmann for investigation, as contained in paragraph 2.1 of Hoffmann Propeller SB E53 Rev. D, is not required by this AD.
(2) Reporting propeller hubs with cracks to Hoffmann, as contained in paragraph 2.3 of Hoffmann Propeller SB E53 Rev. D, is not required by this AD.
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.
Propellers
