50HOUR

TM-1-6625-724-13P Aviation Vibration Analyzer Manual
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TM 1-6625-724-13&P 0075 00 0075 00-3 The CH-47 Flight Plans are listed below with a brief description of their purpose. The selectable Flight Plans (see table 1) are listed in order of appearance in the menu of the CADU and not in the order in which they are to be performed. 50HOUR The CH-47 50-hour vibration survey is performed on the combining and aft transmission oil cooler fans, see task 5. This procedure measures vibration levels of the components only, and does not offer corrective actions for out of tolerance conditions. AFTVIB The aft vibration survey is performed whenever an unusual vibration is suspected in the aft part of the synchronizing drive shaft or cross shaft area, see task 5. This procedure measures vibration at hanger bearings 4, 5, 6, 7, cross shaft No. 1 and cross shaft No. 2. This procedure measures the vibration levels of the components only, and does not offer corrective action. FLIGHT This test, see task 4, is designed to reduce rotor system lateral and vertical vibration to specified levels, using pitch change links, tabs and tracking weights. It is to be used after GROUND and HOVER or for “tuning up” an aircraft that is already in service. FWDVIB The forward vibration survey is performed whenever an unusual vibration is suspected in the forward transmission or synchronizing drive shaft area, see task 5. This procedure measures vibration at the forward transmission oil cooler and at hanger bearings 1 through 3. This procedure measures the vibration levels of the components only, and does not offer corrective action. GROUND This Flight Plan is designed to track the rotors prior to hover balancing, using pitch change links only. It is the first step to be performed after any component change or major rework on the rotor. HOVER This Flight Plan is designed to be used after GROUND has been completed. It is designed to reduce the rotor system’s lateral vibrations to specified levels, using pitch change links and spanwise balance weights. PROBES This Flight Plan is designed to use data from up to 8 accelerometers to assist in isolating irregular or unusual vibrations. It will measure data one channel at a time on DAU ACC1 through ACC4 and the multi-channel cable connected to the track and balance accelerometer blocks. All accelerometers will measure a 0 to 500 Hz spectrum (0 to 30,000 RPM).

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