AN AIRCRAFT DE-ICING SYSTEM

Abstract: The invention relates to an aircraft de-icing system comprising an aircraft-washing hardstanding (1) onto which an aircraft can be moved, and means (3) for spraying process liquor onto the aircraft, and means (11,15,16) for collec­ ting and carrying away the liquor. In order to enable the liquor to be removed from the hardstanding quickly and reliably, the hardstanding is con­ structed so as to comprise a substantially planar surface layer (12) of so-called drainage asphalt, and an impervious layer (11) which is located beneath the planar surface layer and which slopes steeply down towards drainage pipes (15), so as to collect and carry away the process liquor passing down through the surface layer (12). The system also prefer­ ably includes a pump (7) arranged to draw air down through the surface layer so as to entrain therewith any water vapor formed and thus prevent the formation of vapor clouds liab­ le to rise from the hardstanding (1).

Description: The present invention relates to an aircraft de-­ icing system of the kind which comprises an aircraft-wash­ ing hardstanding which presents an aircraft carriageway; means for swilling the aircraft with process liquor; and means for collecting and carrying away the process liquor. In de-icing systems of this kind, for example the system illustrated and described in Swedish Patent Specifi­ cation 7713619-0, the hardstanding exhibiting the carriage­ way must be constructed so as to be able to withstand the heavy load exerted by an aircraft, and so as to enable an aircraft to be moved safely into position in the absence of any disturbing irregularities which might cause the wing-­ tips of the aircraft to swing and be damaged by contact with, for example, washing or swilling devices and the like located in the vicinity of the various aircraft parts. At the same time, the arrangements used to collect and carry away the large quantities of process liquor which run down from the aircraft onto the hardstanding area must be highly effective, without presenting too much of an obstacle to smooth forward movement of the aircraft. In addition, it is found that in the majority of weather conditions heavy mists are formed if the used process liquor is not removed and dispensed with quickly enough, such mists being also troublesome to those parts of the airfield loca­ ted in the vicinity of the de-icing station. The object of the present invention is to provide a system in which the aforesaid disadvantages are avoided substantially completely, in a simple and inexpensive fashion. This object has been achieved in accordance with the invention with the aid of an aircraft-washing hardstanding which comprises a substantially planar surface layer of liquid-permeable road-surfacing material, and an impervious layer which is intended for collecting and carrying away the process liquor and which slopes down towards drainage pipes. In the case of an hardstanding so constructed the process liquor running down onto the surface layer will pass directly through said surface layer, which can conse­ quently be of planar configuration, since the arrangements and devices for collecting and carrying away the process liquor are located beneath the surface layer. A hardstanding of this construction also affords the important advantage of enabling the drainage pipes to be connected to a pump arranged to remove water vapor from the liquid-permeable surface layer by suction. In this way water vapor is prevented, to a large extent, from rising up from the aircraft-washing hardstanding and sweeping into the aircraft in the form of a vapor cloud, which is of considerable benefit with respect to process performance and with respect to the general visibility in busy and crowded airfields. The surface layer also serves as a coarse filter, in which leaves, twigs etc. can fasten. The suction pump is therefore suitably adapted for switching to a mode in which air is temporarily blown through the drainage pipes and up through the outer surface, so that any foreign ob­ jects present can be blown free from the channels and passageways of the surface layer. Preferably, cold ambient air, or optionally chilled air is blown through said passa­ geways for a suitable length of time immediately prior to commencing a de-icing process, which normally takes about three minutes to complete. This affords the advantage of cooling the surface layer and the drainage and discharge pipes to an extent sufficient to cool the water vapor sucked down through the surface layer over the whole of the de-icing process, so that the water contained in the water vapor condenses prior to the water vapor reaching the pump in the machine room. The invention will now be described in more detail with reference to the accompanying drawing, which illustra­ tes in perspective an embodiment of a de-icing system according to the invention, partly in section. The drawing illustrates an elongated rectangular air­ craft-washing hardstanding 1 which is situated on an air­ field, suitably for direct access from the aircraft approach path leading from the airfield buildings to the aircraft runways. The hardstanding 1, has a breadth which is slight­ ly larger than the wing span of the largest aircraft which can be expected for treatment, and extending across the hardstanding is a portal 2 provided with pipes and nozzles 3 so positioned that an aircraft 4 rolling onto the hard­ standing 1 is able to pass through the portal with the nozzles located at a pre-determined distance from the various parts of the aircraft, particularly from the upper and lower surfaces of the wings of the aircraft. Located on one side of the portal 2 is a supervising cabin 5. Located adjacent the cabin 5 is a partially submerged machine room 6, to which the pipes 3 provided with the aforesaid spray nozzles extend. The hardstanding 1 is constructed of three mutually different layers, namely a bottom supporting layer 10, an impervious layer 11 which is located above the support layer 10 and comprises a liquid-impermeable material, such as concrete, and which slopes steeply from both sides of the centre line of the hardstanding 1, and finally a top surface layer 12 which comprises a liquid-permeable mate­ rial, such as a road surfacing material, for example drainage asphalt, and which has a substantially planar top surface. The liquid-permeable material is suitably a hot-mixed (150-170°C) asphalt concrete having cavities of 15-20 % and about about 60 % ballast material of largest ballast frac­ tion, and a fibre addition which increases the compression strength of the material and its length of useful life. Drainage pipes 15 are embedded in the longitudinal edges of the impervious layer 11 around the hardstanding 1, so that all liquid penetrating down through the surface layer 12 and running down along the impervious layer is collected in the drainage pipes 15. The drainage pipes 15 are connected to the machine room 6 by means of discharge pipes 16. The machine room 5 houses an arrangement of pumps, tanks, filters, valves etc. for pumping under high pressure a water-glycol-mixture of varying concentration to the pipes 3 and the nozzles as the aircraft is slowly moved through the portal 2. All surfaces of the aircraft are contacted by the liquid jets in accordance with a pre-determined program, whereupon ice and snow are loosened and washed from the aircraft and fall onto the hardstanding 1 together with the washing liquor, wherewith the liquor and the molten snow and ice quickly pass through the surface layer 12 onto the imper­ vious layer 11 and from there through the drainage pipes 15 and the discharge pipes 16 to the machine room 6, where the liquor is reconditioned and strengthened to the desired concentration for renewed pumping to the pipes 3 and nozzles of the portal 2. The machine room 6 also houses a large-capacity vacuum pump which is connected to the discharge pipes 16, this vacuum pump being effected to draw a flow of air down­ wardly through the surface layer 12. Those clouds of water vapor which would otherwise rise up from the hardstanding 1 and which derive from the relatively warm washing liquor in cold weather will therewith be drawn through the drai­ nage and discharge pipes 15,16 instead, which is an impor­ tant sequel of the invention. The portal 2 need not be an immovable structure, but may be arranged for movement in the longitudinal direction of the hardstanding 1, in which case the aircraft can be allowed to remain stationary during the de-icing process.

Claims: 1. An aircraft de-icing system comprising an aircraft-­ washing hardstanding (1) incorporating a carriageway for an aircraft (4), means (3) for washing the aircraft with pro­ cess liquor, and means (15,16) for collecting and carrying away the process liquor, characterized in that the hard­ standing (1) comprises a substantially planar surface layer (12) constructed from a liquid-permeable road-surfacing material, such as so-called drainage asphalt, and an imper­ vious layer (11) which slopes away towards drainage pipes (15), for collecting and carrying away the process liquor. 2. A de-icing system according to Claim 1, characteri­ zed in that the drainage pipes (15) are connected to a pump for removing water vapor from the liquid permeable surface layer (12) by suction. 3. A de-icing system according to Claim 2, characteri­ zed in that the pump (7) can be switched to a mode in which it temporarily blows air, preferably cold air, through the drainage pipes (15) and up through the surface layer (12).

Inventors: MAGNUSSON, KJELL-ERIC
Applicants: DE-ICING SYSTEM KB
Application year: 1985
Main classification: B64F5
IPC codes: B64F5