Tie-Down Procedures

by

Terry Lankford & Bill Komanetsky
Photography by Terry Lankford

Introduction

"Securing the airplane", the last item on any aircraft checklist, may seem trivial, but considering the pilot is responsible for securing up to several hundred thousand dollars worth of aviation equipment, makes it not so trivial after all.

As an example, at Terry Lankford’s Air Force Aero Club in England, an airplane was lost in a 62 knot gust as a result of improper tie-down.  Expense and trouble resulted for both the aircraft owner and the flight club members when only two minutes of effort by the pilot could have avoided the loss.

The San Francisco Bay area is not known for severe surface winds.  This can cause pilots to become complacent when it comes to proper tie-down procedures. In the northern portion of the state, the intermountain region, the surface winds can often reach hurricane intensities especially during the winter season. In California's Mojave Desert for instance, it is said that the wind never blows less than 30 knots! Because of these types of hazards, developing proper tie-down savvy on the ground is just as important as any pilot-in-command responsibility is while flying an aircraft.

The How's

Chains or ropes should be taught, but not so taught to put a strain on the airplane. In the illustration shown, the airplane's right wing tie-down has proper tension which is not too tight, not too loose; as apposed to the inset in the lower right of the illustration. In this example, the airplane is "leashed" NOT "tied down" — certainly unsatisfactory!

Which is stronger:  the "S" hook or a chain "link?"  It is the link which is the stronger of the two. In this illustration the upper left picture shows a typical tie-down; and under average conditions is satisfactory. The upper center picture shows an even better tie down method. Here the "S" hook would have to be sucked through the tie-down ring before the wind could take the aircraft on an unexpected trip. The upper right picture is the best method for tying down an aircraft. The weakest part of the system, the "S" hook, prevents a link (the strongest part of the system) from sliding out. Any force placed on the airplane is countered by the full strength of the links.

     Even with these precautions, the tie down is limited by yet another factor – the strength of the connection between the chain (or rope) and the ground.  During tie ground operations, the pilot should not just attach the chain to the tie-down ring on the aircraft, but should also inspect to make sure the chain is attached to the ground in such a manner that it will not come loose during high winds.  The pilot can simply pull up on the chain to make sure it is securely attached to the ground before attaching the chain to the aircraft tie-down-ring.  This will also help to test the chain itself where a visual inspection could help to identify links that may be rusted or even damaged.

     Another aspect of ‘Tie Down’ which can help to protect the aircraft from Wind Damage is the use of the Gust lock.  Every aircraft has one, a metal rod, a control stick secured arm, or even a seat belt and harness can be used to assure control surfaces are not damaged during high wind situation.  Under extreme circumstances, the violent movement of any control surface can lead to the ‘bending’ of the surface and surface control arms or even metal damage to the control surface itself if a gust lock is not used.  Normally, gust locks do not prevent an aircraft from being moved by external tow bars or such, so their use should become a habit in every circumstance when securing an aircraft.

     Ahart Aviation Services policies dictate the use of both tie-down chains and gust-locks when securing an aircraft.  It is also common sense to use such devices to avoid damage to an aircraft in the event of bad weather.  Bad weather or not, using both tie-down chains (or ropes) and gust locks whenever an aircraft is secured (and not just during bad weather) will assist all of us in assuring a solid, safe aircraft fleet.

Fly Safe!

Both on and off the ground