PROCEDURE 5: IN-FLIGHT CHECK OF ABSORBERS (Box Type)

PROCEDURE 4: TUNE FORWARD CABIN ABSORBER (Cantilever Spring Type)

Figure 18. UH-60 Box Frame Absorber Main Rotor 4/REV Vibration Check And Tuning Procedure

TM-1-6625-724-13P Aviation Vibration Analyzer Manual
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TM 1-6625-724-13&P 0069 00 0069 00-29 correct diagnostic actions (refer to figure 18 for main rotor 4/REV vibration check and tuning procedure and table 2 for tuning weight adjustments). NOTE The goal for pilot heel vertical level is between 0.3 ips and 0.6 ips, with 0.5 ips being the target. If the level drops below 0.3 ips, nose absorber may interfere with cabin absorber tuning and actually degrade cabin and cockpit 4/REV vibration. a. Turn on DAU. b. Turn on CADU. c. Press QUIT on the CADU until all selections are undefined. d. Use cursor keys to highlight Aircraft Type, and then press DO. e. Use cursor keys to highlight UH-60, and then press DO. f. Tail Number is highlighted. Press DO. g. Use cursor keys to highlight a tail number or enter a new tail number (up to seven digits), then press DO. h. Flight Plan is highlighted. Press DO. i. Use cursor keys to highlight BOXABS. Press DO. j. Enter the Measure mode by pressing F1. k. Stabilize the aircraft at 145 Kts, 98% Nr, and level flight. l. Use cursor keys to highlight 98%. Press DO twice. m. When the measurement is completed, the BOXABS display indicates: 98% done. NOTE 100.5% flight condition is achieved by using the increase/decrease switch to maximum without going into ECU lockout. The aircraft may be flown in Engine Control Unit (ECU) LOCKOUT only when ECU LOCKOUT procedures in TM 1-1520-237-MTF are followed n. Repeat steps k through m for 145 Kts, 99% Nr, 100% Nr, 100.5% Nr, 101% Nr and 102% Nr. o. After the measurement is completed, press DO on Finish, then press DO on Main Menu. p. Press F2 to select Display menu. q. Select the Summary Display option and press DO twice r. Using figure 18, Box Absorber Flowchart, determine whether cabin box frame absorber requires adjustment. s. If the cabin absorber requires adjustment, use table 2 to determine the weight adjustments for the absorber and perform adjustments according to TM 1-1520-237-23-2 (Chapter 2 airframe maintenance AVUM). t. Repeat task 7 procedure 5 steps (a) through (s) and perform adjustments until no further adjustments are required. u. Make appropriate logbook entry when all main rotor 4/REV work is done. v. Remove AVA test equipment and return the aircraft to a flight-ready condition.

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