M. 712 INTERSTAGE AIR-BLEED SPEED ADJUSTMENT

Following the Maximum Continuous Power Check

TM-1-1520-240-MTF Army Model CH-47D Heilcopter (EIC:RCD) Manual
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TM 1-1520-240-MTF 4-31 COMPLETE PROCEDURE Engine No. 1 Engine No. 2 Maximum PTIT allowed 806 899 Recorded PTIT (subtracted) -775 -872 TEMP MARGIN VALUE 31 27 PAC Number Margins 31 5=6.2 27 5=5.4 Rounded PAC Margin 6 5 DECU PAT switch value 26 28 PATN adj for FAT +14_C -1 -1 Adjusted PATN 25 27 Adjusted PATN 25 27 PAC Margins(subtracted) -6 -5 DECU PAT Trigger Values 19 22 Enter these values as the PAT Trigger Value on the PAT LOG. M. 712 INTERSTAGE AIR-BLEED SPEED ADJUST- MENT Reference: TM 55-1520-240-23 NOTE Unsatisfactory bleed band cycling or compressor stall may be encountered if bleed band closure is not within N1 speed range specified. If N1 speed for bleed band closure is above that specified, an increase in specified fuel consumption will result until bleed band closes. In an extreme case, where belled band does not close at all, or may be open again at high power, engine will suffer loss of maximum power. 1-38.

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