Boeing 737's Horizontal Stabilizer Must Be Scrutinized

FAA: This AD is effective May 20, 2013.

We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of an incorrect procedure used to apply the wear and corrosion protective surface coating to attach pins of the horizontal stabilizer rear spar. This AD requires inspecting to determine the part number of the attach pins of the horizontal stabilizer rear spar, and replacing certain attach pins with new, improved attach pins. We are issuing this AD to prevent premature failure of the attach pins, which could cause reduced structural integrity of the horizontal stabilizer to fuselage attachment, resulting in loss of control of the airplane.

 

We estimate that this AD affects 1,050 airplanes of U.S. registry.

We estimate the following costs to comply with this AD:

Estimated Costs
Action	Labor cost	Parts cost	Cost per product	Cost on U.S. operators
Inspection and attach pin replacement	39 work-hours × $85 per hour = $3,315	Up to $6,312	$9,627	Up to $10,108,350.

According to the manufacturer, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected individuals. We do not control warranty coverage for affected individuals. As a result, we have included all costs in our cost estimate.

 Applicability

(1) This AD applies to all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes, certificated in any category.

(2) Installation of Supplemental Type Certificate (STC) ST00830SE (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/408E012E008616A7862578880060456C?OpenDocument&Highlight=st00830se) does not affect the ability to accomplish the actions required by this AD. Therefore, for airplanes on which STC ST00830SE is installed, a “change in product” alternative method of compliance (AMOC) approval request is not necessary to comply with the requirements of 14 CFR 39.17. For all other AMOC requests, the operator must request approval for an AMOC in accordance with the procedures specified in paragraph (k) of this AD.

 

Unsafe Condition

This AD was prompted by reports of an incorrect procedure used to apply the wear and corrosion protective surface coating to attach pins of the horizontal stabilizer rear spar. We are issuing this AD to prevent premature failure of the attach pins, which could cause reduced structural integrity of the horizontal stabilizer to fuselage attachment, resulting in loss of control of the airplane.

Part Number (P/N) Inspection

For airplanes having line numbers 1 through 3534 inclusive: Before the accumulation of 56,000 total flight cycles, or within 3,000 flight cycles after the effective date of this AD, whichever occurs later, inspect to determine the part number of the attach pins of the horizontal stabilizer rear spar. A review of airplane maintenance records is acceptable in lieu of this inspection if the part number of the attach pin can be conclusively determined from that review.

 

Replacement

If, during the inspection required by paragraph (g) of this AD, any horizontal stabilizer rear spar attach pin has P/N 180A1612-3 or 180A1612-4, prior to the accumulation of 56,000 total flight cycles on the pin, or within 3,000 flight cycles after the effective date of this AD, whichever occurs later, replace with a new attach pin having P/N 180A1612-7 or 180A1612-8, respectively, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-55-1093, dated April 9, 2012.