|CHAPTER 9—Float and Ski Equipped Helicopters
The preflight inspection consists of the standard aircraft inspection with a few additional items associated with the floats. When performing a preflight inspection, follow the manufacturer’s recommendations. A typical inspection of the floats includes:
A helicopter on a hard surface has the friction of the skids or floats to counter the torque produced when the rotor is engaged. Therefore, you have more control over the helicopter if you can engage the rotors while it is sitting on a hard surface. On water, little or no antitorque control is present until the rotor system has accelerated to approximately 50 percent of its normal operating r.p.m. A heavily loaded helicopter’s floats sit deeper in the water and create more resistance to the turning force than a lightly loaded helicopter. Thus a helicopter turns less when heavily loaded and more when lightly loaded.
To overcome the spinning and to prevent drifting, tie the helicopter securely to a dock or to the shore using the fore and aft cross tubes if not otherwise indicated in the POH or RFM. If help is not available for casting off, it may be necessary to paddle to a clear location well away from the shoreline for a safe start. Wind and water currents may cause the helicopter to turn or drift a considerable distance before control is obtained. To compensate, use a starting position upwind and upcurrent of a clear area.
Illusions of movement or non-movement can make it difficult to maintain a fixed position during rotor engagement and runup. Techniques to overcome these illusions are discussed later.
TAXIING AND HOVERING
Where possible, it is usually more convenient and safer to hover taxi to the destination. However, due to power limits, local restrictions, noise, water spray, or creating a hazard to other vessels or people, it may be necessary to water taxi the helicopter. To taxi in water, maintain full rotor r.p.m. and use sufficient up collective to provide responsive cyclic control to move the helicopter. Never bottom the collective pitch while the helicopter is in motion to avoid momentarily sinking the floats or capsizing the helicopter. Float equipped helicopters should be taxied with the nose in the direction of movement. Maximum taxi speed is attained when the bow wave around the nose of the floats rises slightly above the normal waterline. Beyond this speed, the bow wave flows over the front portion of the floats, and this severe drag may capsize the helicopter. When the helicopter is heavily loaded, it is restricted to a slower taxiing speed than when lightly loaded.When taxiing in small waves, point the helicopter into or at a slight angle to the waves. Never allow the helicopter to roll in the trough. In some instances, increasing collective can produce enough downwash to create a slight smoothing effect on windproduced waves.
Aground swell can be dangerous to the tail rotor while the helicopter is riding up and pitching over the swell.
Approach the swell at a 30º to 45º angle and use collective pitch to minimize bobbing. If it becomes obvious that continued water taxi could lead to a serious problem, lift the helicopter off and reassess the situation. It might be possible to land in an area that does not contain the same conditions.
When hovering over or taxiing on water, movement of the helicopter may be difficult to judge. The rippling effect of the water from the downwash makes it appear as if the helicopter is moving in one direction when it is in fact stationary or even moving in the opposite direction. To maintain a fixed position or maintain a straight course while taxiing and hovering, use a fixed reference such as the bank or a stationary object in the water. When reference points are not available, judge movement by swirls, burbles, or slicks seen around the floats.
Hovering a helicopter over open water can create deceptive sensations. Without a reference point, extensive or rapid helicopter movements may go unnoticed. Very smooth and very rough water aggravate this situation. The most desirable water conditions are moderate ripples from a light breeze. An odd sensation, similar to vertigo, is sometimes produced by the concentric outward ripples resulting from the rotorwash, and pilots must keep their eyes moving and avoid staring at any particular spot. The inexperienced pilot may choose to initiate a slight forward movement when taking off into or landing from a hover. This guards against undesirable backward or sideward drift during takeoff or landing. With smooth water conditions, the usual tendency is to hover too high because the outward-flowing ripples from the rotorwash gives the pilot the sensation of being in a bowl and descending.
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