Airworthiness Directive · Amendment 39-11664 · Boeing Model 747-200B, -300, -400, -400D, and -400F Series Airplanes
Boeing Model 747-200B, -300, -400, -400D, and -400F Series Airplanes
Superseded. A later AD replaced this one: AD 2002-19-12. Comply with the one in force.
Model 747-200B, -300 series airplanes equipped with General Electric (GE) CF6-80C2 series engines, and Model 747-400, 747-400D, and 747-400F series airplanes equipped with General Electric (GE) CF6-80C2 series engines or Pratt & Whitney PW4000 series engines; line numbers (L/N) 679 through 1061 inclusive; certificated in any category.
Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-200B, -300, -400, -400D, and -400F series airplanes. This action requires repetitive inspections to detect cracking of fire extinguisher discharge tubes in certain engine struts, and corrective action, if necessary. For certain airplanes, this action also provides for a modification of the fire extinguisher discharge tubes, which constitutes terminating action for the repetitive inspections. This amendment is prompted by reports that cracked fire extinguisher discharge tubes have been found in the engine struts on certain airplanes. The actions specified in this AD are intended to detect and correct cracked fire extinguishing tubes in the engine struts. In the event of an engine fire, such cracked tubes could reduce the amount of fire extinguishing agent that can be delivered to the engine, and could result in a fire spreading from the engine to the wing of the airplane.
To detect and correct cracked fire extinguishing tubes in the engine struts, which, in the event of an engine fire, could reduce the amount of fire extinguishing agent that can be delivered to the engine, and result in a fire spreading from the engine to the wing of the airplane, accomplish the following:
(a) Within 30 days after the effective date of this AD, perform a detailed visual inspection to detect cracking of the fire extinguisher discharge tubes in the number 2 and number 3 engine struts, in accordance with Boeing Alert Service Bulletin 747-26A2266, dated March 3, 2000.
Note 2: For the purposes of this AD, a detailed visual inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”
(1) If no cracking is detected, repeat the inspection thereafter at intervals not to exceed 18 months.
(2) If any cracking is detected, prior to further flight, replace the cracked tube with a new or serviceable part, in accordance with Boeing Alert Service Bulletin 747-26A2266, dated March 3, 2000. Repeat the inspection required by paragraph (a) of this AD within 18 months after the replacement and thereafter at intervals not to exceed 18 months.
(b) For Model 747-400 series airplanes, L/N 696 through 1061 inclusive, equipped with Pratt & Whitney PW4000 series engines: Modification of the fire extinguisher discharge tubes in the number 2 and number 3 struts, in accordance with Boeing Service Bulletin 747-26-2233, dated May 11, 1995, constitutes terminating action for the repetitive inspection requirements of this AD.
