ATA 29

Hydraulic Line Integrity
We have learned that there have been events where hydraulic lines are cracking. On a recent incident, the left main hydraulic annunciator came on about 30 minutes after takeoff, followed by the right hydraulic annunciator. The crew returned to home base, blew the landing gear down, and landing uneventfully. It was found that the pressure line into the lift dump valve was cracked near a B-nut. The hydraulic pumps ran dry for an indeterminate time. As you go about your routine area inspections, please pay attention for hydraulic fluid staining and fluidleaks. As the fleet continues to mature, we want to ensure we are aware of areas that may become fleet symptoms. Advisory Circular 43-4A identifies problem areas for corrosion, and one of them is around B-nuts and line marking tapes. Corrosion will weaken the line sufficiently to cause failure. If you have recently experienced a similar situation, please let us know via e-mail to westwind@worthingtonav.com

ATA 53

Fuselage Skin Corrosion
On April 3, 2007 a Westwind operator reported a cabin decompression due to a fuselage skin panel failing, the cause was severe corrosion. It was corroded in multiple places in the chemically milled areas hidden under the Insulation/Noise/Vibration Damping Pads.

A thorough inspection of adjacent fuselage skin panels and bulkheads was completed noting that the corrosion was contained to only the one panel which is located at the top aft portion of the fuselage between Fuselage Station 219.05 and Fuselage Station 269.87.

Please refer to the FAA AC 43-4A “Corrosion Control for Aircraft” document for details related to corrosion prevention.

A follow up investigation of the event is underway and if any fleet action is required it will be communicated accordingly

ATA 78

During routine inspections, we have been finding several lower thrust reverser (T/R) doors with internal corrosion. This shows up on the outer skin as a rippling around the rivet heads. If the internal structure is inspected with a boroscope, corrosion is evident between the skin and ribs. Some of the doors have been so severe that they had to be replaced.

ATA 32

Landing Gear Axle Corrosion
Most Westwind 1124 / 1124A operators are aware that the main landing gear axles are susceptible to internal corrosion. Moisture is the main contributor to this condition, as it becomes trapped in the bore of the axle. It can enter from the anti-skid transducer conduit or from the end plug of the axle itself. Corrosion within the limits set forth in the Westwind Maintenance Manual Chapter 32-10-01 can be removed. Unfortunately, pitting beyond the maintenance manual limits is cause for axle rejection. Be sure your maintenance facility properly coats the axle bore with DC4 and seals the axle cap and top of the anti-skid transducer conduit with sealer. Attention to this detail may prevent axle replacement.