Gulfstream Spring 2007

• Maintaining Flight Control Balance
• GV Emergency Exit Cabin Windows Fail-Leak Check

Maintaining Flight Control Balance

— Jim Overheul

Several recent inspections have identified some flight control balance issues worth noting.

First, a GIII was recently in for a technical appraisal and during the vertical stabilizer/rudder exterior inspection the rudder appeared to have heavy sanding marks in the primer under the surface of the topcoat. A paint thickness check was performed and the rudder was found to be out of Gulfstream GAMPS 4000 limitations. The rudder was removed and found to be out of static balance. The rudder was stripped of the existing paint and painted following Gulfstream GAMPS 4000. The rudder was again checked for static balance and found to be within limits.

Second, a recent 24 Month Honeycomb Inspection /Bond Test on a GIV identified an elevator trim tab delaminated out of maintenance manual limitations. A new trim tab was ordered and found to be 10 ounces heavier than the defective trim tab. The new trim tab was temporarily installed and the elevator was checked for static balance and found to be out of limits. The rest of the elevator was inspected per the maintenance manual to verify no other condition existed that would affect static balance. The elevator was noted with the light weight tuning strips installed. The light weight tuning strips were removed and replaced with the max amount of heavy tuning strips and found to still be out of static balance. The new trim tab was removed and a loaner trim tab was installed until a repaired trim tab could be installed. The elevator was checked for static balance and found to be in the center of the tolerance, which meant the elevator was close to being out of balance before the heavy tuning strips were installed. The loaner trim tab weighed the same as the removed trim tab. This highlights the importance of balancing the flight control to the center of the tolerance if possible.

GV Emergency Exit Cabin Windows Fail-Leak Check

— Jim Overheul

Recently a GV was in for a maintenance visit and during that visit all four emergency exit cabin windows were leak checked using the Gulfstream GV maintenance manual procedure. All four emergency exit cabin windows failed leak check. The cabin window leak check maintenance manual procedure states that if a leak occurs comply with the following:

(a) Do not adjust setscrews of lock tabs or cam links.
(b) Perform cabin emergency exit/fixed window gasket repair.

All four emergency exit windows were removed and the form-in-place gasket was inspected. A few small voids in the gasket were identified but nothing that would cause the leakage. The voids were repaired and the emergency exits were reinstalled. After allowing cure time, the windows were leak checked again and noted to be leaking in the same area. After further diagnostics it was found that all four emergency exit windows were leaking between the cabin window frame and the seal outer panel, cabin window. All four windows were removed and resealed. The windows were reinstalled and they passed the leak check. A below emergency exit inspection was complied with to verify no damage was caused by the water intrusion. The fixed cabin windows are the same design and can leak in the same area. However, a leak here is less likely because they are not removed and reinstalled as often. We advise that before replacing the form-in-place gasket identify exactly were the leak is coming from.

For more information on these issues or any other Gulfstream issue, please contact me by phone at 800.525.2376 ext. 847.

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