AD 82-24-05

82-24-05 DETROIT DIESEL ALLISON: Amendment 39-4498. Applies to all Detroit Diesel Allison (DDA) Model 250 series engines equipped with Bendix fuel control assemblies and power turbine governor assemblies containing or suspected of containing P/N 2526146 bushing assemblies with a nylon ball bearing separator. NOTE: Assemblies listed in the appendix to this AD have steel ball bearing separators. Compliance required, as indicated, unless already accomplished. To prevent possible engine power loss, autoacceleration, overspeeding, or power turbine governor instability/malfunctioning caused by failure of P/N 2526146 bushing assemblies with a nylon ball bearing separator installed in Bendix fuel control assemblies and power turbine governor assemblies, accomplish the following: (a) Before further flight, remove from service affected Bendix fuel control assembly and power turbine governor assembly that exhibit one or more of the following symptoms that cannot be corrected by following the maintenance procedures in the appropriate DDA Operations and Maintenance Manual and, where applicable, install assemblies that have steel ball bearing separators:

Fuel Control Assembly Symptoms N1 fluctuation Autoacceleration or overspeed Inability to obtain maximum power or N1 limiting Inability to adjust/set idle speed or excessive flight idle

Power Turbine Governor Symptoms Governor instability Excessive droop which cannot be cured by correct control system rigging

NOTE: Above symptoms manifested by fuel control assemblies or power turbine governor assemblies which incorporate steel ball bearing separators should be corrected using appropriate DDA Operations and Maintenance Manual procedures. (b) Inspect in accordance with Paragraph (c) affected Bendix fuel control assemblies and power turbine governor assemblies within the hours time in service specified in the following schedule or before October 16, 1983, whichever occurs first:

Time in Service (Hours) of Fuel Control or Power Turbine Governor Since New or Last Overhaul Inspect Within The Following Time (Hours) In Service Less than 300 100 300 or more and less than 600 50 600 or more and less than 900 150 900 or more and less than 1200 200 More than 1200 250

(c) Inspect in accordance with the applicable DDA Commercial Engine Alert Bulletin, or later FAA- approved revision, listed below to determine whether the P/N 2526146 bushing assembly with a nylon ball bearing separator is installed:

Engine Model Bulletin No., dated October 15, 1982 250-C18 CEB-A-229 250-C20, -C20B, -C20F, -C20J CEB-A-1206 250-B15G CEB-A-99 250-B17, -B17B, -B17C CEB-A-1166 250-C28B, -28C CEB-A-73-2026 250-C30, -C30P, -C30S CEB-A-73-3021

(d) If a bushing assembly containing a nylon ball bearing separator is identified during inspection required by Paragraph (c), replace the bushing assembly with a serviceable assembly having a steel ball bearing separator. Reidentify serviceable fuel control assemblies or power turbine governor assemblies, after inspection, in accordance with the applicable DDA service bulletin. (e) Special flight permits may be issued in accordance with FARs 21.197 and 21.199 to operate aircraft to a base where compliance with this AD can be accomplished. (f) Upon request of an operator, the Manager, Chicago Aircraft Certification Office, FAA, Central Region, may adjust the compliance time specified in this AD provided such requests are made through an FAA maintenance inspector, and the request contains substantiating data to justify the request for that operator. (g) Upon request of the operator, an equivalent means of compliance with the requirements of this AD may be approved by the Manager, Chicago Aircraft Certification Office, FAA, Central Region. This amendment becomes effective November 26, 1982.

AD 82-24-05 APPENDIX

All Bendix fuel control assemblies andpower turbine governor assemblies installed in DDA Model 250 series engines are suspected of containing nylon ball bearing separators, except the following assemblies all of which have steel ball bearing separators: 1. Units identified by the letter "K" marked on the fuel control assemblies or power turbine governor assemblies identification plate in the "less issues" (LI) block. 2. The following fuel control assemblies and power turbine governor assemblies which have acceptable New Hampshire Ball Bearing (NHBB) bushing assemblies and are NOT marked with letter "K."

Model Bendix Part No. DDA Part No. DDA Model Unit Serial No. Fuel Control Assemblies:

DP-N2 2524644-18 23001794 250-C20B/F/J 336103 and subsequent DP-P2 2524654-15 23001796 250-B17B/C 336036 and subsequent DP-T3 2524738-20 23001797 250-C28B/C 334078 and subsequent DP-V1 2524854-1 23004537 250-C30P 336051 and subsequent DP-V1 2524745-17 23001798 250-C30/S 334132 and subsequent Power Turbine Governor Assemblies:

AL-AA1 2524667-8 23005492 250-C20/B/F 29288 and subsequent AL-AA1 2524769-7 23005493 250-C20B/J 29367 and subsequent AL-AC1 2524677-6 23005494 250-C28B/C 27511 and subsequent AL-AD1 2524692-5 23006268 250-C30/P/S 28914 and subsequent

3. Fuel control assemblies and power turbine governor assemblies manufactured prior to November 7, 1979, provided that they have NOT been overhauled or have NOT had P/N 2526146 bushing assembly replaced since that date. The following listed fuel control assemblies and power turbine governor assemblies were manufactured prior to November 7, 1979:

Model Bendix Part No. Engine Model All Serial Numbers Including and Prior To Fuel Control Assemblies:

DP-D3 2524463 250-C18 323884 DP-D3 2524527 250-C18 326174 DP-M1 2524384 250-B15G 319258 DP-N1 2524552 250-C20 320894 DP-N2 2524644 250-C20B, C20F, C20J 327936 DP-P1 2524558 250-B17 319575 DP-P2 2524654 250-B17B 327892 DP-P2 2524661 250-B17B, B17C 317461 DP-T3 2524738 250-C28B, C28C 328100 DP-V1 2524745 250-C30, C30S 326387 Power Turbine Governor Assemblies:

AL-AA1 2524553 250-C20/B/F 18010 AL-AA1 2524667 250-C20/B/F 22797 AL-AA1 2524706 250-C20/B/J 20218 AL-AA1 2524769 250-C20/B/J 22921 AL-AC1 2524677 250-C28B, C28C 23097 AL-AD1 2524692 250-C30, C30P, C30S 21897