Pneumatic De-ice Boots
Inspection and maintenance tips
By Joe Escobar
It is that time of year again when the aircraft we work on will be subjected to icing conditions. In order to keep those aircraft flying safely, their de-icing systems need to be maintained at an efficient level. In this article, we will discuss some of the issues pertaining to pneumatic de-ice boot inspection and maintenance as well as some removal and installation tips.
De-ice boots prevent the accumulation of ice by breaking it up at the leading edge surfaces. A typical system uses air pressure that is generated from either an air pump driven by the engine, or by bleed air from the engine. From there, it goes through a pressure regulator and then a flow control valve, which is sequenced off of a timer. The timer can either be operated manually by the pilot or in automatic cycle where it will cycle every one to three minutes.
De-ice boots should be inspected routinely as per the manufacturer’s recommendations. Regular cleaning of the boots is helpful not only for appearance sake, but for enabling the detection of defects in the boot. General condition of the boots should be evaluated and any damaged areas repaired as required.
Cuts in the de-ice boots should be repaired as soon as possible, which will prevent the cut from enlarging during operation and will also prevent water from entering the boot. If water enters the de-ice boot, it can freeze and prevent the boot from operating properly.
Boots should also be inspected for blow holes. This defect looks like numerous pin holes on the boot. Richard Rauckhorst, Director of Engineering for Ice Shield De-Icing Systems, a product of B/E Aerospace, explains the phenomena. "The conductive edge sealer (bordering the de-ice boot) allows a path for static dissipation, and that is critical to the de-icer’s life. If you are flying in cold, dry air, you’ll build up a very large static discharge in that surface. And, you’ll actually get what we call ’blow holes’ in the surface of the part where you build up so much static, it has to dissipate. It’s just like a lightning bolt, a mini-lightning bolt. It will actually blow a hole in the surface of the part. So, that’s one of those repairs that you want to prevent. But to prevent it, you need to have a good conductive path."
As Rauckhorst mentions, maintaining a good conductive path is essential to de-ice boot life. The conductive edge sealer provides this path for static dissipation. Itis important to use only those products approved by the manufacturer. Substitution of an alternate sealer may seem harmless, but it may not provide the needed conduction forthe static to dissipate. Also, ensure that static dissipators like static wicks are maintained.
Patching the de-ice boot is a fairly simple procedure and typically involves using a template over the area and scuffing up the boot. It is then thoroughly cleaned with a solvent, and the repair patch is installed.
Patches are now available that have a pressure-sensitive adhesive on the back. The old process of having to apply glue layers to the boot and the patch are not necessary. After the area is scuffed and cleaned, the backing is taken off the patch and it is applied to the boot. Boot replacement should be considered in cases of excessive damage.
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