Chapter 11. Safety, Ground Operations, & Servicing

Tiedown Procedures for Seaplanes

Seaplanes can be moored to a buoy, weather permitting, or tied to a dock. Weather causes wave action, and waves cause the seaplane to bob and roll. This bobbing and rolling while tied to a dock can cause damage.

When warning of an impending storm is received and it is not possible to fly the aircraft out of the storm area, some compartments of the seaplane can be flooded, partially sinking the aircraft. In addition, the aircraft should be tied down securely to anchors. Seaplanes tied down on land have been saved from high-wind damage by filling the floats with water in addition to tying the aircraft down in the usual manner.

During heavy weather, if possible, remove the seaplane from the water and tie down in the same manner as a land plane. If this is not possible, the seaplane could be anchored in a sheltered area away from wind and waves.

Tiedown Procedures for Ski Planes

Ski planes are tied down, if the securing means are available, in the same manner as land planes.

Ski-equipped airplanes can be secured on ice or in snow by using a device called a dead-man. A dead-man is any item at hand (such as a piece of pipe, log, and so forth) that a rope is attached to and buried in a snow or ice trench. Using caution to keep the free end of the rope dry and unfrozen, snow is packed in the trench. If available, pour water into the trench; when it is frozen, tie down the aircraft with the free end of the rope.

Operators of ski-equipped aircraft sometimes pack soft snow around the skis, pour water on the snow, and permit the skis to freeze to the ice. This, in addition to the usual tiedown procedures, aids in preventing damage from windstorms. Caution must be used when moving an aircraft that has been secured in this manner to ensure that a ski is not still frozen to the ground. Otherwise, damage to the aircraft or skis can occur.

Tiedown Procedures for Helicopters

Helicopters, like other aircraft are secured to prevent structural damage, which can occur from high-velocity surface winds.

Helicopters should be secured in hangars, when possible. If not, they should be tied down securely. Helicopters that are tied down can usually sustain winds up to approximately 65 mph. If at all possible, helicopters should be evacuated to a safe area if tornadoes or hurricanes are anticipated.

For added protection, helicopters should be moved to a clear area so that they will not be damaged by flying objects or falling limbs from surrounding trees.

If high winds are anticipated with the helicopter parked in the open, the main rotor blades should be tied down. Detailed instructions for securing and mooring each type of helicopter can be found in the applicable maintenance manual. [Figure 11-13] Methods of securing helicopters vary with weather conditions, the length of time the aircraft is expected to remain on the ground, and location and characteristics of the aircraft. Wheel chocks, control locks, rope tiedowns, mooring covers, tip socks, tiedown assemblies, parking brakes, and rotor brakes are used to secure helicopters.

Typical mooring procedures are as follows:

  • Face the helicopter in the direction from which the highest forecast wind or gusts are anticipated.
  • Spot the helicopter slightly more than one rotorspan distance from other aircraft.
  • Place wheel chocks ahead of and behind all wheels (where applicable). On helicopters equipped with skids, retract the ground handling wheels, lower the helicopter to rest on the skids, and install wheel position lockpins or remove the ground handling wheels. Ground handling wheels should be secured inside the aircraft or inside the hangar or storage buildings. Do not leave them unsecured on the flight line.
  • Align the blades and install tiedown assemblies as prescribed by the helicopter manufacturer. [Figure 11-14] Tie straps snugly without strain, and during wet weather, provide some slack to avoid the possibility of the straps shrinking, causing undue stresses on the aircraft and/or its rotor system(s).
  • Fasten the tiedown ropes or cables to the forward and aft landing gear cross tubes and secure to ground stakes or tiedown rings.

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