0071 00 TM 1-6625-724-13&P 0071 00-40 TASK 5 – ISOLATE IRREGULAR VIBRATIONS Table 3. AH-64 Frequency Data AH-64A 100% Nr Frequency (Hz) AH-64D 101% Nr Frequency (Hz) Source 4.8 4.87 Main rotor 1/REV 9.6 9.74 Main rotor 2/REV 14.4 14.61 Main rotor 3/REV 18.7 18.87 MGB G3 shaft 19.3 19.48 Main rotor 4/REV 23.4 23.62 Tail rotor 1/REV 38.4 38.96 Main rotor 8/REV 46.8 47.25 Tail rotor 2/REV 57.6 58.44 Main rotor 12/REV 60.6 61.21 Tail rotor vertical drive shaft 73.2 73.91 MGB G1 shaft 79.8 80.07 MGB G2 shaft 80.2 81.02 AGB Idler shaft 80.3 81.06 Tail rotor drive shaft 82.2 83.00 AGB Idler 93.6 94.49 Tail rotor 4/REV 127.1 128.33 ECS compressor (2) 137.5 138.89 APU shaft 164.0 165.66 Nose gearbox shaft 189.8 191.67 ECS condenser fan (4) 204.2 206.24 AC Generator 210.6 212.68 Hydraulic pump 349.2 352.69 Engine shaft 379.5 383.33 APS Blower 384.5 388.33 ECS Fan (4) 384.5 388.33 Crew station fan 408.4 412.47 AC Generator 2/REV 665.3 672.03 SUN gear clash, MGB 1330.6 1344.06 2x SUN gear clash, MGB 1333.1 1346.53 Tail rotor gearbox clash 1895.0 1914.13 Hydraulic pump 9/REV 2634.1 2660.73 G1/G3 clash, MGB 2969.1 2999.10 Intermediate gearbox clash 4756.1 4804.09 MGB clash 6499.6 6565.59 GB/TR drive shaft clash 6737.7 6805.80 ACC gearbox clash 10824.1 10933.45 Nose gearbox clash