Gulfstream Winter 2008

• Time is Running Out for Ultrasonic Inspection of Tay Engine Fan Blades
• Gulfstream GIV Rudder Trim Variance

Time is Running Out for Ultrasonic Inspection of Tay Engine Fan Blades

— James Overheul

On January 22, 2007, the Federal Aviation Administration (FAA) issued AD 2007-03-02 Rolls-Royce Deutschland Ltd & Co KG (RRD). This AD applies to the Tay 611-8 engines with LP compressor module Part Number (PN) M01100AA or PN M01100AB installed. AD 2007-03-02 mandates operators to perform Ultrasonic Inspection (UI) of the LP compressor fan blades for cracks, using Part 2 of RRD Service Bulletin (SB) Number TAY-72-1442, Revision 3. The AD mandates that the SB initial UI at the next shop visit for engine mid-life inspection or overhaul, but no later than 12 months after the effective date of this AD (March 5, 2007), whichever occurs first. Repetitive UIs before reaching every 8,000 flight hours but no later than every 10 years since-last-fan-blade UI, whichever occurs first. Operators who are not yet in compliance with this AD should schedule this inspection immediately in order to meet the March 5, 2008 deadline. For more details, please contact Doug Donahue at 269.969.8400.

Gulfstream GIV Rudder Trim Variance

— James Overheul

Gulfstream GIV rudder trim variance (rudder kick) is one of those nuisance occurrences that most GIV operators have experienced or will experience in the future. It should be approached as being more than nuisance occurrence. Rudder kick can be a sign that an aircraft system or systems may not be functioning as designed. This may be the first and only indication to the pilot of a problem and beyond that, there may be other systems that are not performing properly. For example, if the 12th Stage valve is the root cause, then it is possible that it may not ensure that adequate pressure and or temperature is supplied to the pneumatic systems at all times, including the anti-ice system.

Several recent failed Bleed Air System-Operational Tests have initiated conversation with the crew and had validated they have been experiencing rudder kick. After repair and satisfactory compliance of the Bleed Air System-Operational Test procedure the crew has reported that not only the rudder kick but sometimes several other system abnormalities are gone as well – cabin temperature fluctuations and bleed air pressure split to name a few. We recommend that any sign of rudder kick or other abnormality with the bleed air system should be investigated and repaired.

As the result of a rudder kick squawk, we have diagnosed several component failures ranging from precooler outlet temperature sensor to bleed air temperature anticipator sensors. We have also noted improperly installed servo air filters. When servicing the servo air filter it is very important to ensure the filter is properly aligned and seated to avoid damage as noted in the installation procedure in the Gulfstream GIV Maintenance Manual. On several occasions we noted a filter damaged to the point where it was blocking the inlet pressure or allowing unfiltered air to be delivered to the precooler servo air pressure regulator and torque motor assembly. We have also noted several occasions a precooler temperature control anticipator sensor that checked good (temperature-versus-resistance) at ambient but has failed at temperature extremes due to expansion of internal connecting leads.

If there are any questions on this topic or any other topic please contact me at 269.969.8477.

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