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Tiedown Sense
Part 3
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The following practices are designed for day-in- day-out use regardless of the inconvenience they might entail. These practices are principally for protection of light and medium weight aircraft and result from experiences with the storms of the past. Adoption of the following recommendations should materially reduce aircraft damage from windstorms. Partially disassembled aircraft which are outdoors, particularly light aircraft with engines removed, should be hangared as soon as storm warnings are received. Loose wings should never be tied against a fuselage; they should be stored inside a hangar. Wherever possible, fly aircraft out of anticipated storm danger zones. If possible, hangar the aircraft in a stormproof hangar. The minimum recommended tiedown rope is one which will resist a pull of approximately 3,000 pounds. (Many users of plastic tiedown rape, yellow polypropylene, 1/2-inch and larger, reported little or no rope failure because of its elasticity. In some instances, nylon and hemp rope failed. In others, steel cables were snapped while hemp lines, due to their elasticity, held. In many cases, both hemp and steel cable tiedowns failed due to chafing. |
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A single row of properly secured sandbags or 2x2's (spoiler boards ) on the top of a wing's leading edge will serve as an effective spoiler and reduce the lifting tendency of the wings. Do not overload the wings with sandbags. If the anticipated winds will exceed the lift-off speed of the aircraft wings, then the makeshift spoilers should run the entire length of the wings. The 2x2 homemade spoiler is very easily constructed and may be used for all types of light aircraft. Drill a number of 3 /8-inch holes across the length of the 2x2. Cement a strip of 1-inch foam rubber to the entire length of the 2x2. This will prevent damaging the wing's surface. Avoid nailing the foam rubber to the spoiler since the nailheads may damage the wing's skin.
To prevent the spoiler from shifting position due to the wind, it is suggested that knots be tied in the rope on either side: of the drilled holes. The spoiler should then be tied onto an aircraft's wings at the 25 percent chord point. To prevent damaging the wing's leading and trailing edges, it is suggested that a piece of foam rubber, or carpet, or even rags be placed under the nylon rope before tying. Some people may like to substitute bungee (elastic) cords for the long lengths of nylon rope.
Follow the manufacturer's tiedown instructions for each make and model aircraft. Another alternative means for tying down aircraft of various types and sizes is by utilizing continuous lengths of parallel wire ropes passed through U-bolt anchors and fastened at the ends of the line with wire rope clips. Tiedown chains are attached to the wire rope with roundpin galvanized anchor shackles. This allows the tiedown chains to "float" along the wire rope and gives a variable distance between anchor points so that a variety of large, medium, and small aircraft can use a vertical tiedown without loss of space. The vertical anchor significantly reduces impact loads that may occur during gusty wind conditions.
Still another means of securing an aircraft is with tiedown cables, one at each wing and the third at the tail section. One end of a tiedown cable is secured with a snaphook to the tiedown anchor eye protruding above ground; the other end is hooked through the tiedown rings installed on the aircraft. Cable slack is taken up with an adjustable locking device.
Multiengine aircraft will obviously require stronger tiedown facilities because of the additional weight of these aircraft. The anchors should be capable of a holding power of 4,000 pounds each for the lighter executive twin engine aircraft. Much higher load capacity would be required for the heavier transport type aircraft. Do not depend on the multiengine aircraft's weight to protect it from damage by windstorms. It is quite possible for a sudden, severe windstorm to move, damage, or even overturn such aircraft.
Multiengine aircraft should, therefore, always be tied down and chocked when they are to be left unattended for any length of time. Gust locks should be used to protect control surfaces. Be sure that gust locks are foolproof: a takeoff with gust locks on is not only embarrassing but could prove to be disastrous. If the landing gear makes use of the down lock safety pins, then these pins should be inserted when the aircraft is being secured.
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