TM 55-2840-241-23g. Engine Starting CharacteristicsAdjustments. (Refer to fig. 5-6.1).There are two fuel control adjustmentswhich can be used to change the start-ing characteristics of the engine.These adjustments are a starting derich-ment adjustment in addition to a startacceleration adjustment, which is onsome engines. The conditions, which canbe improved by these adjustments, areindicated in Table 5-1.(1) Start-Derichment Adjustment. (Refer to fig.5-6.1). The start-derichment (derich) adjustmentcan be used to correct lean (slow) start or rich (hot)start conditions. This adjustment is effectivebelow 33% Nl speed. For slow starts at Nl speedsbetween 35% and 55% Nl speed, refer to Start/Ac-celeration Fuel Flow Adjustment, subparagraph(2). (Refer to table 5-l).NOTEThe start derichment adjustment on the latest modifiedfuel control has a wider angular range than earlier models(200° in Place of 100°). Neutral position for the latest con-trol is 7 dots/70O from the counterclockwise stop. Neu-tral on controls prior to this is a 4 dots/40°counterclockwise. The effective start derichment speedrange is between 20% and 33% N1. Also, turning the ad-justment to the clockwise stop closes the Py vent whichdeactivates the start derichment.NOTETo accurately determine the proper adjustment, condi-tions under which the adjustments are made should beconsistent, i.e., a fully charged aircraft battery, the sameresidual TOT and the same lightoff speed.(a) For low temperature with slow starts at 20-33% N1speed, adjust the start-derichment as follows:1 Remove lockwire securing adjustment locknut to Pcfilter-fitting.Do not disturb the pointer-to-shaft sealed wireat any time. This is an overhaul function only.2 Loosen the adjustment locknut.Figure 5-6.1. Start/Acceleration and StartDerichment Adjustments.During attempted start, TOT must be closelymonitored to prevent overtemperature opera-tion. Record overtemperature in the EngineLog.3 Make adjustment using an Allen wrench.Turn clockwise to enrich the starting fuel flow toimprove stagnated starts, cold weather starts, orhigh altitude ground starts. Make adjustment in10° maximum increments (dots are10° apart) andtighten locknut to 20-25 lb in. (2.3-2.8 Nm) aftereach setting. Check the starting peak TOT aftereach setting until satisfactory starts are made.4 When desired adjustment is obtained, secure lockoutto Pc filter-fitting with lockwire.Monitor TOT closely after start-derichment ad-justment to be sure overtemperature limits arenot exceeded.5-10.2 Change 11
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