ATA 30

Wing De-ice
We recently had a problem with the wing boots failing to fully inflate on a Westwind II. We looked at the distributor valve, all the aft equipment bay plumbing, and the boots themselves for excessive pinholes. All the pressures were within the system limits. We discovered that the wing lines run under the lav floor area, up each side of the fuselage to the wing root bulkhead fittings, and then to the boots. Because the lines under the floor are the lowest point in the system, moisture had collected in them over the years and turned the bottom of the tubes into Swiss cheese. We made new lines, and the system worked perfectly. Next time you are in the area for maintenance, take a good look at the lines, or even put a little pressure in them and do a leak check. It might disclose a similar problem.

ATA 30

Surface De-ice Boot Care and Maintenance
Things that could help Westwind operators identify problem areas with the de-ice boots.
Electrical Bonding:
The number one problem I have attributed to premature de-ice boot removal and installation is not neglect – that would be number two on the list – but the lack of electrical bonding. As the Westwind flies very fast through the atmosphere, the de-ice boots will generate static electricity. If the de-ice boot cannot dissipate this static electricity to the airframe, the charge will build up and finally blow out of the de-ice boot leading edge, leaving small cuts in the shape of half circles. Sometimes the damage will be a whole circle if the static electricity is heavy enough. How can this be prevented? First of all, make sure the static dischargers are within limits per the Aircraft Maintenance Manual (AMM) Chapter 23-60-00. The next thing to inspect would be the “DEICER CONDUCTIVE CEMENT” at the trailing edge of the de-ice boots. Without conductive cement, the de-ice boot has no way of discharging static electricity to the airframe. The conductive cement should overlap the de-ice boot and the painted surface. On many occasions I have seen black paint used instead of conductive cement and, of course, the de-ice boots showed severe wear from static discharge.
• Neglect:
“Application of AGEMASTER No. 1 should be made every 150 flight hours” according to AMM Chapter 30-10-00. I prefer Jet Stream PBS Boot Sealant, as it protects against ultraviolet (UV) damage, and it is much easier to remove the old sealant with PBS Prep in order to recondition the de-ice boots. Failure to condition the de-ice boots will cause UV damage and impact erosion, which leaves small pits and holes of irregular shapes along the leading edge. Plus it doesn’t look very pretty. In either case, the de-ice boots will get holes in them and if bad enough, they will not inflate properly, causing a safety-of-flight problem.

ATA 56

Checking the Windshield Rain Seal
Reports of moisture between the inner and outer windshields of a Westwind 1124/1124A are common among owners/operators. Generally, this is caused by water getting past the outer windshield rain seal. Check the condition of the rain seal. Cracked or missing sealer could let water in, leading to this condition.

Desiccant that turns white quickly (indicating that it has absorbed moisture) or other visible signs such as water spots could also indicate the seal is bad. While your aircraft is in for maintenance, have the windshields purged with low-pressure nitrogen. Follow the Maintenance Manual procedures very closely if you do this yourself. Too much pressure will damage the windshield. As the system is purged, it can be quickly checked for external leaks.

If not repaired, an accumulation of water can cause corrosion to form on the windshield heat probes and surrounding structure, as well as causing improper windshield heat operation. Simply removing the old rain seal and applying fresh sealer will often keep the water out. Removing the outer windshield, cleaning and reinstalling it would be a last resort. The windshield desiccants should last between inspections, but always keep them fresh.