Field of the Invention According to one application the invention relates to a method of protecting external surfaces of an aircraft component such as a de-icing boots. These are typically affixed to the wings and tail of an aircraft in order to provide a method of removing build up of ice.

Typically ice builds up on wings, tails, fins etc. during flight through moisture laden air with a temperature range of 0° to-10°C. The ice build up can interrupt the airflow over the airfoil section to such a degree that it alters the flight characteristics of an air foil section/aircraft. In addition the build up of ice also adds weight to an aircraft causing a centre of gravity change and gross weight change. If icing is not controlled the flight characteristics of the plane can be altered to such an extent that normal operational control of the plane can be lost leading to catastrophic results.

De-ice boots operate by having an air inlet which enables low pressure air to be pumped into the de-ice boot usually at around 15 to 20psi. Air is forced through a regulator into longitudinal air sacks which lie just below a protective layer of rubber/neoprene. As the individual sacks inflate, humps appear along the length of the boot as corrugations causing any ice attached to break off and eject into the air flow. The de-ice boots are operated cyclically by the air crew if icing is noted. The cycle of inflation is only for a few seconds at a time.

Following inflation the boot returns to normal contour and is ready for the next cycle.

The de-ice boots have no material effect on the operation of the aircraft.

Unfortunately, de-ice boots fitted to aircraft are very expensive to purchase and are labour intensive.

A normal boot fit can take around 30 to 40 person hours and can tie an aircraft up in maintenance for two days.

The surface of the de-ice boot exposed to the elements requires constant maintenance to ensure serviceability. When in use boots can become damaged due to mechanical abrasion, atmospheric damage and aging.

Therefore the life of boots is dependent upon the care they receive whilst fitted to the aircraft and prompt repair of any damage. If a de-ice boot is not maintained for a period of upto two years experience indicates that the de-ice boot will invariably need to be replaced.

The present invention aims at providing a method for protecting an external aircraft component and/or aerodynamic surface or component therefore.

It is preferred that the method is directed at providing protection for a de-ice boot.

Summary of the Invention According to the present invention there is provided a method of protecting an external aerodynamic surface comprising the steps of providing a flexible sheet of plastics material, attaching the sheet over a predetermined surface of the external aerodynamic surface using an attachment means whereby the sheet can be removed without damaging the surface to which it is attached.

Preferably the attachment means comprises an adhesive.

It is preferred that the attachment means comprises a tape such as contact adhesive tape.

Preferably the attachment means comprises a sealing strip.

The method preferably includes fixing a base member to the surface and attaching the flexible sheet to the base member.

The attachment means may connect the flexible sheet to the base member.

The base member may be permanently fixed to the surface of a de-ice boot.

The attachment means may comprise a frangible connecting member such as a frangible strip that when broken away enables the flexible member to be replaced.

The flexible sheet may be attached to a surface surrounding the predetermined surface.

The predetermined surface is preferably an aircraft de-ice boot.

The flexible surface may have a sufficient elasticity to enable unhindered operation of the de-ice boot.

It is preferred that the flexible sheet is able to be expanded to at least the same extent as the de-ice boot.

Preferably the flexible sheet comprises neoprene.

The adhesive may comprise 3M laminating adhesive 9672SLE.

Alternatively the adhesive is a Scotch-Grip Spray 80 neoprene contact adhesive of 1300L adhesive.

It is preferred that the flexible sheet once attached to the de-ice boot is able to be peeled off without damaging the upper surface of the de-ice boot.

It is preferred that the flexible sheet conforms to the contours of the upper surface of the de-ice boot.

Preferably the flexible sheet has characteristics of smoothness, flexibility, resilience, strength and abrasive resistance.

According to another embodiment of the present invention the de-ice boot may be in the form of a device with an external surface having a series of strips of flexible material attached thereto.

It is preferred that each of the elongate strips is removably attached to a respective one of the ribs of the external surface of the de-ice boot device.

Preferably the flexible sheet includes a portion which allows a person to grip the flexible sheet and strip it away from the external surface of the de-ice boot.

According to another embodiment the method

includes having an intermediate member between the flexible sheet and the de-ice boot external surface, which intermediate member facilitates easy attachment and removal of the flexible sheet from the external surface of the de-ice boot.

According to another embodiment the method includes providing edging portions to cover the edges of the flexible sheet when attached to the external surface of the predetermined surface.

It is preferred that the edging portions comprise sealing strips.

The sealing strips may be removed to allow easy removal of the flexible sheet.

The method may include providing tear portions to allow easy removal of the flexible sheet.

According to one embodiment the flexible sheet has a plurality of layers with the outermost layer having greatest abrasive resistance.

According to one embodiment the flexible sheet is preconfigured to the external shape of the de-ice.

Plastics material is intended to cover elastic or plastic or other synthetic resilient materials.

Brief Description of the Drawing A preferred embodiment of the present invention will now be described by way of example only with reference to Figure 1 of the accompanying drawing.

Detailed Description of the Drawing Preferably the flexible sheet has a backing strip which when removed reveals the adhesive layer which is adapted to be placed on top of the predetermined surface.

As shown in Figure 1 a de-ice boot 10 is provided with longitudinal air sacks 11 which are inflated through an air inlet 12.

A protective layer 13 is placed over the de-ice boot 10 and is provided in accordance with the following steps: i. Cut the neoprene sheet so that it matches

the boot to be covered. Weigh the pieces of sheet. ii. Seal any leakages in the de-ice boot with approved patches. iii. Thoroughly clean the boot surfaces using isopropyl alcohol using clean gloved hands, breath and eye protection. Wipe the boot dry using industrial tissues until the tissues come up clean. If the boot surface is showing signs of oxidation or perishing. it may be lightly abraded with light emery paper. Similarly clean the bond surface of the neoprene sheet. iv. The aircraft must be moved into a hangar before any bonding work commences and ambient temperature should be between 21 and 38°C. During all adhesive application wear clean gloves and provide breath and eye protection. v. When using 9672LE adhesive, first cut the laminating tape to size then apply the cut tape to the bond surface of the neoprene sheet. vi. Very lightly down the boot surface with primer 3M94 and allow to dry. vii. Apply the neoprene sheet (with adhesive tape) to the boot surface, initially attaching along the top edge and progressively rolling around the leading edge of the wing to the bottom edge of the boot. In pushing the neoprene sheet down onto the boot, moderate pressure should be used and progressively applied over the whole surface. This may be achieved by rolling backwards and forwards with a paint roller. viii. Allow 3 hours for setting of the adhesive in the hangar. The bond strength after this time may be further improved by heating the neoprene surface with a hot air gun, but not over 100°C. ix. When using Spray 80 adhesive first mask off the area to be sprayed then shake the aerosol can vigorously for 5 to 10 seconds before use. x. Holding the can 12 to 18cm away from the surface, apply at least 2 uniform and overlaying coats of

adhesive to both bonding surfaces. When spraying, push the nozzle of the can all the way down to avoid spluttering and to produce a uniform pattern. Make sure the nozzle is always pointed away from people. xi. The spray nozzle must be kept clean and free of accumulated adhesive. Should adhesive build up or nozzle blocking occur, the nozzle may be cleaned with Scotch-Grip Solvent No. 2. xii. Excess adhesive may be removed using Scotch-Grip Solvent No. 2. xiii. Allowing 10 minutes for the adhesive to cure, apply the neoprene sheet to the boot, starting along the top edge and progressively rolling around the leading edge and finishing at the boot bottom edge. Roll the surfaces together such as to preclude air bubbles. xiv. Allow 3 hours curing in the hangar before pushing the aircraft out into the sun for further curing. xv. Fillet along the neoprene sheet edges using PR 1442 filleting compound. xvi. Adjust aircraft weight and balance for sheet weight applied.

In its preferred form the protective layer consists of neoprene rubber which covers the entire de-ice boot surface, in a similar fashion to a second skin. The neoprene sheeting is thin and supple enough to encourage complete inflation of the air sacs and thus does not deteriorate the functionality of the boot from its intended function. The neoprene sheet therefore becomes a sacrificial surface to the elements and any mechanical damage thus protecting the integrity of the de-ice boot below it. The sheeting is secured to the substrate surface by either a contact adhesive in the method previously described or by a contact adhesive tape.

It is preferred that the neoprene rubber used is . 8mm in thickness.

Once the protective layer has been used continuously and is degraded to such an extent it needs to

be replaced, it is merely peeled off and replaced by another covering sheet in the same manner as previously described.

It is preferred that the top surface of the covering sheet is smooth.

It is preferred that edge sealing is provided to the flexible sheet and that this edge sealing and/or the flexible sheet is attached to the de-ice boot by a conductive sealant. This is to ensure that there is no static electricity build up.

The edge sealing may be provided by an edge sealing strip which does not have to have the same flexibility or resilience as the flexible sheet.

It is desirable that the flexible sheet is made from the same material as the de-ice boot.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word"comprise"or variations such as "comprises"or"comprising"is used in an inclusive sense, i. e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or in any other country.