Airworthiness Directive · Amendment 39-17159 · Nacelles/pylons
The Boeing Company Airplanes
This AD applies to all The Boeing Company Model 707-100 long body, -200, -100B long body, and -100B short body series airplanes; Model 707-300, -300B, -300C, and -400 series airplanes; and Model 720 and 720B series airplanes; certificated in any category.
We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 707 airplanes, and Model 720 and 720B series airplanes. This AD was prompted by reports of cracking of the midspar fittings, and of the engine and nacelle strut separating from the airplane. This AD requires performing a detailed inspection of the midspar fittings of the nacelle strut to confirm that the correct part number is installed, and installing the correct part number if necessary; performing repetitive high frequency eddy current (HFEC) inspections of the midspar fittings of the nacelle strut for cracks, and repair if necessary; and performing repetitive general visual inspections of the nacelle struts to verify that the nacelle strut has not drooped below its normal position, applying the droop stripe to the nacelle strut and sailboat fairing if necessary, and performing repair if necessary. We are issuing this AD to detect and correct cracking of the midspar fitting, which could result in separation of the nacelle strut and engine from the airplane while in flight, and consequent loss of controllability of the airplane.
Within 120 days after the effective date of this AD: Do a detailed inspection of the midspar fittings of engine numbers 2 and 3 nacelle struts to confirm that the correct part number is installed, in accordance with the Accomplishment Instructions of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012 (which is not incorporated by reference in this AD). If any incorrect part number is found: Before further flight, install the correct part number, in accordance with the Accomplishment Instructions of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012.
Note 1 to paragraph (g) of this AD: Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012, refers to Boeing 707/720 Service Bulletin 3183, Revision 5, dated September 16, 1993 (which is not incorporated by reference in this AD), as an additional source of guidance for high frequency eddy current (HFEC) inspections of the midspar fittings of engine numbers 2 and 3 nacelle struts for cracks.
At the applicable times specified in paragraph 1.E., “Compliance,” of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012, except as provided in paragraph (j) of this AD: Do an HFEC inspection of the midspar fittings of engine numbers 2 and 3 nacelle struts for cracks, in accordance with the Accomplishment Instructions of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012, except as provided by paragraph (k) of this AD. If any crack is found, before further flight, repair using a method approved in accordance with the procedures specified in paragraph (m) of this AD. Thereafter, repeat the inspection at the applicable intervals specified in paragraph 1.E., “Compliance,” of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012.
At the applicable times specified in paragraph 1.E., “Compliance,” of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012, except as provided in paragraph (j) of this AD: Do a general visual inspection of the nacelle struts of engine numbers 1, 2, 3, and 4 to verify that the nacelle strut has not drooped below its normal position, in accordance with the Accomplishment Instructions of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012. Thereafter, repeat the inspection at the applicable intervals specified in paragraph 1.E., “Compliance,” of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012.
(1) If any nacelle strut has drooped below its normal position: Before further flight, repair using a method approved in accordance with the procedures specified in paragraph (m) of this AD.
(2) If any nacelle strut has not drooped below its normal position, and no droop stripe specified in Boeing 707/720 Service Bulletin 3377, dated November 21, 1979 (which is not incorporated by reference in this AD) has been applied: At the applicable times in paragraph 1.E., “Compliance,” of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012, except as provided in paragraph (j) of this AD: Apply the droop stripe to the nacelle strut and sailboat fairing, on each side of engine numbers 1, 2, 3, and 4 nacelle struts, in accordance with the Accomplishment Instructions of Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012.
Where Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012, specifies a compliance time based on “the original issue date of this service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.
Where Boeing 707 Alert Service Bulletin A3537, dated January 30, 2012, refers to “Manual 707, 720 NDT Part 6, 51-00-00 Figure 24 as an accepted procedure” for the HFEC inspection, this AD requires that the inspection be done in accordance with Figure 24, Steel Part Surface Inspection (Impedance Plane Display), Subject 51-00-00, Structural-General, of Part 6, Eddy Current, of the Boeing 707/720 Nondestructive Test Manual, Document D6-48023, Revision 120, dated March 15, 2012.
