AD 73-26-04

73-26-04 MCDONNELL DOUGLAS: Amdt. 39-1760. Applies to Model DC-10-10, DC-10-30, and DC-10-30F airplanes certificated in all categories.

Compliance required within the next 10 hours' of flight for Model DC-10-10 airplanes and 50 hours' of flight for Model DC-10-30 and DC-10-30F airplanes after the effective date of this AD, unless already accomplished.

To determine that the correct nose cowl attach bolts are installed and to assure the proper installation of the bolts, conduct a one-time inspection of the wing mounted engine nose cowl attach bolts and take corrective action in accordance with the following:

(a) Remove bolts P/N 71658-6 (identified by 71658-6 stamped on the bolt head), if installed, and replace with P/N EWB 22-6-14 bolts, or FAA Western Region approved equivalent bolts (see paragraph (f)), in accordance with the instructions in paragraph (b).

(b) Install bolts P/N EWB 22-6-14, identified by HI PSI EWB 22-6 stamped on the bolt head, or FAA WesternRegion approved equivalent. Bolts must protrude through the nut by .030 to .180 inch. Bolts protruding more than .180 inch must have washers P/N MS 20002-6, P/N WPL 22-6, or FAA Western Region approved equivalent washers added between the existing countersunk washer P/N WCL22-6 and the nose cowl attach fitting to meet the .030 to .180 inch protrusion range. The grip length, -14, is not indicated on the bolt head and numbers stamped on the bolt head other than EWB 22-6 should be disregarded.

(c) Inspect all engine flange nutplates and replace any that are cracked or have attach rivets sheared off. As an alternative, accomplish either (1) or (2) below.

(1) Remove the nut from the nutplate by bending the tangs of the retainer and install a new nut from nutplate General Electric (G.E.) P/N 9698M80P01 and rebend the nutplate tangs to secure the nut.

(2) Remove the nutplate by chisel or grinding the rivets. Modify washer P/N MS20002-5 by drilling I.D. to .378/.388 inch. Reidentify the washer as G.E. P/N 9146M8-4P01 and install under nut G.E. P/N 9629-M48P06.

(d) Back all bolts out until clampup torque is removed and make a running torque check of nut retention. Nuts with less than 10-inch-pounds of locking torque must be replaced, or accomplish either (1) or (2) below.

(1) Thoroughly clean the nose cowl and mating engine flange holes, bolts and nut threads with a brush and 1, 1, 1 Trichloroethane (MIL-T-81533), Naptha, or MEK (FED TT-M-261). Allow to dry completely after cleaning. Apply primer MIL-S-22473, Grade T, Form R, to bolt threads and allow to dry completely. Apply locking sealant MIL-S-22473, Grade A or Grade AV, or Loctite 271 on the first three bolt threads. These instructions are per Douglas Process Standard (DPS) 3.51, except that Loctite is an acceptable material not covered by the DPS.

(2) After the bolts have been torqued in accordance with paragraph (e), below, clean the exposed threads and nut end per (d) (1), above, and puddle PR1422 class B sealant with accelerator to fill bolt end exposed threads. Cap bolt end with PR1422 sealant and extend the sealant partially over the nut (Reference DPS 2.50).

(e) Lubricate nuts, bolt threads, and washers with MIL-L-25681 per DPS 1.22, or with an FAA Western Region approved equivalent lubricant. If the (D) (1) procedure is used, lubricate bolt shank and washers under the bolt head only (no lubricant on the bolt or nut threads). Torque bolts to 28 to 32 foot pounds. Reference: McDonnell Douglas Maintenance Manual Chapter 71-11-00, page 206.

(f) Bolts P/N R21T5B1-6F14, P/N VS200-3F6-14, P/N EWB TM9-6-14, or P/N BAC B30MT6T14 are, for the purpose of complying with this AD, FAA Western Region approved equivalents for bolt P/N EWB 22-6-14. When bolt P/N BAC B30MT6T14 is installed, the bolt must protrude through the nut by .030 to .130 inch and have washers installed per paragraph (b) if the bolt protrudes more than .130 inch.

NOTE: McDonnell Douglaswires C1-SVC-DC10COM-167, C1-SVC-DC10COM-168, C1-SVC-DC10COM-170, C1-SVC-DC10COM-176 cover the procedures described above.

(g) Special flight permits may be issued under FARs 21.197 and 21.199 for the purpose of moving the aircraft to a base to accomplish maintenance to comply with this AD.

(h) Prior to installation of any quick engine change (QEC) unit, verify accomplishment of this AD.

This amendment is effective December 19, 1973, for all persons except those to whom it was made effective immediately by telegram dated November 7, 1973.