Airworthiness Directive · Amendment 39-17800 · Landing gear
Bombardier, Inc. Airplanes
Superseded. A later AD replaced this one: AD 2018-17-09. Comply with the one in force.
This AD applies to Bombardier, Inc. Model DHC-8-400, -401, and -402 airplanes, certificated in any category, serial numbers 4001 and subsequent, equipped with a main landing gear (MLG) up-lock having part number 46500-7 or 46500-9.
We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400 series airplanes. This AD was prompted by reports of excessive wear on the lower latch surface of the main landing gear (MLG) up-lock hook. This AD requires revising the maintenance program. We are issuing this AD to detect and correct up- lock hooks worn beyond the wear limit, which could prevent the successful extension of the MLG using the primary landing gear extension system, which in combination with an alternate extension system failure could result in the inability to extend the MLG.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
Within 30 days after the effective date of this AD, revise the maintenance or inspection program, as applicable, to incorporate the information specified in Task Number 323100-202 of Bombardier Temporary Revision MRB-66, dated December 7, 2011, to Section 1-32, Systems/Powerplant Maintenance Program of MRB Report Part 1, Bombardier Q400 Dash 8 Maintenance Requirements Manual, PSM 1-84-7. The compliance time for the initial functional check is at the applicable time specified in paragraph (g)(1), (g)(2), or (g)(3) of this AD. The compliance time for the repetitive interval is at intervals not to exceed 6,000 flight hours or 60 months, whichever occurs first.
Note 1 to Paragraph (g) of this AD: The maintenance or inspection program revision required by paragraph (g) of this AD may be done by inserting a copy of Bombardier Temporary Revision MRB-66, dated December 7, 2011, to Section 1-32, Systems/Powerplant Maintenance Program of MRB Report Part 1, Bombardier Q400 Dash 8 Maintenance Requirements Manual, PSM 1-84-7. When this temporary revision has been included in general revisions of the PSM, the general revisions may be inserted in the PSM, provided the relevant information in the general revision is identical to that in TR MRB-66.
(1) For up-lock hook assemblies that have 15,000 total flight cycles or more as of the effective date of this AD: The compliance time for doing the initial functional check is within 600 flight cycles after the effective date of this AD.
(2) For up-lock hook assemblies that have 12,000 total flight cycles or more, but fewer than 15,000 total flight cycles, as of the effective date of this AD: The compliance time for doing the initial functional check is within 1,200 flight cycles after the effective date of this AD, but before the accumulation of 15,600 total flight cycles on the assembly.
(3) For up-lock hook assemblies with fewer than 12,000 total flight cycles as of the effective date of this AD: The compliance time for doing the initial functional check is within 6,000 flight cycles after the effective date of this AD, but before the accumulation of 13,200 total flight cycles on the assembly.
For any up-lock assembly outside the wear limit specified in the Inspection Notes of Bombardier Repair Drawing 8/4-32-0190, Issue 2, dated January 14, 2013; and on which the up-lock roller on the MLG shock strut is free to rotate and free of any damage or flat spots on the riding surface: In lieu of doing the initial functional check, as required by paragraph (g) of this AD, accomplishing the actions specified in paragraphs (h)(1) through (h)(4) of this AD in accordance with Bombardier Repair Drawing 8/4-32-0190, Issue 2, dated January 14, 2013, may be done. However, as of 36 months after the effective date of this AD, the initial functional check must be done in accordance with the requirements of paragraph (g) of this AD.
(1) Do a detailed inspection for deformation, corrosion, or broken springs of the up-lock assembly of the MLG. If deformation, corrosion, or broken springs are found, before further flight, replace the spring.
(2) Measure the groove depth of the lower latch working surface.
(i) If the groove depth is greater than or equal to 0.022 inch, before further flight, replace the up-lock assembly part number (P/N) 46500-7 or 46500-9 with a new assembly, or an assembly with a new or reworked hook installed.
(ii) If the groove depth is greater than 0.017 inch and less than or equal to 0.0215 inch: Within 600 flight cycles after accomplishing the measurement, do the up-lock inspection as specified in paragraphs (h)(1) and (h)(2) of this AD, and repeat the inspections thereafter at intervals not to exceed 600 flight cycles. Replacing the up-lock hook with a new or reworked hook, or installing a new up-lock assembly, terminates the repetitive inspections.
(iii) If the groove depth is between 0.0215 and 0.0220 inch: Within 300 flight cycles after the measurement, replace the up-lock hook with a new or reworked hook, or with a new up-lock assembly.
(3) Unless already accomplished, within 6,000 flight hours or 36 months after doing the initial inspection specified in paragraph (h)(1) of this AD: Replace the up-lock assembly with a new assembly, or a new or reworked hook installed.
(4) Inspect the up-lock roller on both main gear shock struts for freedom of movement.
(i) If the up-lock roller cannot be freely rotated by finger force, or any flat spots exceeding 0.060 inch (across the flats) are found, before further flight, replace the up-lock roller.
(ii) Repeat the inspections thereafter at intervals not to exceed 50 flight hours until the up-lock has been replaced with a new assembly, or a new or reworked up-lock hook has been installed. Replacing the up-lock with a new assembly, or installing a new or reworked up-lock hook, terminates the repetitive inspection requirements.
