Honeywell has introduced new N2 monopoles with internal enhancements that improve N2 monopole durability. Service Bulletin (SB) 77-3023 covers all TFE731-2/3/4/5 engine models and replaces N2 monopole P/N 3070722-3 with P/N 3070722-10.
The above SB does not apply to the TFE731-5BR-1H engine (Hawker 800XP). Instead, this engine utilizes SB 77-3022 which replaces N2 monopole P/N 3070722-3 with P/N 3070722-9. The Hawker 800XP application also requires a specific engine harness when upgrading to the improved N2 monopole. Engine harness P/N verification is necessary. If the improper harness is used, the N2 monopole will not fit correctly and could result in intermittent N2 signal loss. SB 72-3731 covers installation of the proper engine harness.
When troubleshooting N2 signal issues, verify the P/N of N2 monopole installed. Resistance values have changed and the LMM does not reflect the correct resistance values for improved N2 monopole. Always refer to Service Bulletins for correct resistance values.
TFE731-20/40/50/60 engines also have an improved N2 monopole introduced through a Spare Parts Bulletin. N2 monopole P/N 3070722-8 replaces P/N 3070722-7. Also, when troubleshooting N2 signal issues, always verify the P/N of N2 monopole installed. The resistance values are different than listed in the LMM. Refer to Service Information Letter D200808000038 for the correct values.
Please contact a Duncan Aviation Turbine Engine Tech Rep for more information.
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