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.