TFE731 Winter 2002

• Fan Rotor Disc Replacement Per Service Bulletin TFE731-A72-3668
• Acoustic Surveys

Fan Rotor Disc Replacement Per Service Bulletin TFE731-A72-3668

— Mike Healzer

Operators have only 11 months to replace the “old style” fan discs in TFE731-2/2C/3/3A/3B/3C/3D/4 engines (P/N 3072162-All, 3073539-All, 3073436-All, 3074529-All and 3072816-All). The details of this replacement are found in Service Bulletin TFE731- A72-3668. Also note that an FAA Airworthiness Directive, No. AD2001-23-09, regarding the fan disc issue has been released.

Honeywell has an adequate supply of replacement fan discs. But, the concern is that many operators will wait until the very end to schedule this work and Honeywell's Authorized Service Center Network will not have the capacity to replace large amounts of these discs prior to the December 31, 2002 deadline.

For this reason, Honeywell is encouraging operators to coordinate the replacement of their fan discs with service centers as quickly as possible to minimize delays and inconveniences.

The operators decision to replace these discs should be based on several factors:

• If the fan disc will exhaust its cycle life prior to December 31, 2002, replace the disc at or before the expiration of the disc’s cycle life limit. No overrun tolerance for cycle life components is allowed.
• If the engine is due for a MPI or MPI/CZI prior to December 31, 2002, and the cycle life limit of the disc won’t be exhausted prior to the MPI or MPI/CZI, defer the replacement of the fan disc until the scheduled MPI or MPI/CZI.
• If neither of the above conditions apply to your discs/engines, schedule the replacement of the disc to coincide with another downtime event anytime prior to December 31, 2002. To prevent scheduling problems, replace the disc(s) prior to the fourth quarter of 2002.

An extended warranty program (available only through the Honeywell Authorized Service Center Network) has been developed to cover the fan disc replacement. This program calls for replacement part pro-rate pricing to maintain the $/cycle operating cost of the new fan disc consistent with the old one.

If you have any questions regarding this program, please do not hesitate to contact Jon Dodson, Mike Healzer or Doug Alleman at 800.228.4277.

Acoustic Surveys

— Doug Alleman

When unusual noises are heard in an aircraft cabin they should be investigated. However, not all such noises are indicative of an engine problem.

Honeywell engineers have determined that low frequncy sounds such as rumbling or growling sounds often heard at normal operational N1 speeds (while on the ground or occasionally in descent) can be due to accessories (generator bearings and cooling fans etc.) or fluid lines and fittings rubbing on the nacelle cowlings or bulkheads. These noises can be amplified by an aircraft’s structural resonance and are not caused by engine problems.

Acoustic surveys are performed using a laptop computer with a condenser microphone. The recorded data is played back to compare the frequency and amplitude of the sounds to identify sources of noise complaint. Engine N1 and N2 speeds are documented at the same time the data recordings are made.

Although though these noises may be normal, Honeywell encourages careful examination to determine their cause.

Duncan Aviation has technicians trained in acoustic technology to help determine the source of unusual noises or vibrations in your aircraft.

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