Helicopter on Floats
by
Ironsides

[with contribution from Patrick Jacobs]

Warning

Don't try flying a helicopter over water until you have some rotor time under your belt. Those who fly fixed wing aircraft off water have some protection. That is, the expensive parts like the radio and servos are inside the fuselage and are basically waterproof. Not so the helicopter, all the parts are hanging out in the breeze and if you go into the water, everything will get soaked, including your wallet. Additionally, fixed wing aircraft construction is such that there are floatation pockets all over the place. Not so with helicopters made of steel and plastic parts - they have no buoyancy at all.

Helicopter Floats

Heli floats come in four basic types. You can buy inflatables off-the-shelf, plastic floats that are intended for fixed wing but that work for helis, kid's beach "flotation noodles" that can be adapted, and foam cores that you build yourself.
 
Inflatables
Plastics

 
 
 
 
Noodles
Foam/Balsa/Fibreglass

Pendulum Effect

Adding relatively heavy floats to the bottom of a heli increases the stability of the aircraft. However, should that heavy weight start swinging too much, a pendulum effect can set up. Stay ahead of the heli and damp out any swings.

Tail Rotor Strike

On land the inflatables have a tendency to be a bit soft and to allow the heli to rock fore and aft. Watch the tail rotor as there is more possibility that it will hit the ground than with normal fixed gear.

When landing on the water, ease on gently and keep a little forward pressure to make sure the craft does not settle back on its haunches.

Taxiing

In light breezes, when on the water you can taxi by tilting the rotor disk in the desired direction of travel. Be careful, if you drive the rotor over too hard, you will submerge a float and do damage.

Aerobatics

If you choose the light inflatables, aerobatics are still very achievable.

Crash Considerations

When a fixed wing model crashes into the water, it is better to have the floats rip off like a ski binding if too much force is encountered. Both the floats and the fixed wing wreckage will float 99.9% of the time.

However, when a heli augurs into the water, the last thing you want is for the life jacket to tear away. It is the only chance you have of the wreckage staying afloat long enough for you to recover it.

First rule: Make sure the floats stay on.

Flying Scenarios

You can take off from the beach and fly over water and then land back on terra firma. More advanced pilots can start the engine on land, put the model on the water, then take off and land on water. It is strongly suggested that you try the land-to-land profile until you get the feel of the effects that floats have on your heli.

Simulator

If you have a simulator, it is strongly suggested that you use it. Add some weight to your model set up and watch the sensitivity to collective change. Throw in some wind and turbulence to find out how the model reacts. Unfortunately, the simulator will not tell you much about the manner in which the increased drag of your floats will affect fast forward flight.

Wind

For all heli fliers, wind at the beach is a major factor. At the flying field, you can determine the wind and put the model down so that the canopy faces into wind. At the beach, if you have anything but an on-shore breeze, it is hard to do a tail-in take-off and landing.

If you try to do a water take-off with anything other than an on-shore breeze, your heli will immediately weather vane into the prevailing wind and start moving downwind. You might be good enough to perform a nose-in take-off, but most of us are not in that league. For those who don't know, in a nose-in hover the yaw, pitch and roll axes are reversed. The pilot has to turn his brain inside out and backwards. That's why heli pilots look weird!

Second Rule: You first attempts should be made on a very calm day.

Spool Up Torque

When you take off from land, the ground has enough friction to absorb the torque as the main rotor spools up for take-off. On water, as soon as you increase the throttle, the whole machine wants to rotate like an earth augur. It takes a fair amount of practice to balance the rudder input to that of the rotor torque.
 
 

You can add fixed water rudders to the backs of the floats (except inflatables) to minimize float rotation.

Third Rule: Watch out for spool up torque when taking off from water.

Rotor Negative Incidence

It is nice to have some negative incidence on the rotor at low throttle. When the engine dies, you can dump the collective, keep up the rotor speed and perform a graceful auto-rotation.

Taking off from water, negative incidence can sink your heli. If you increase the rotor speed and inadvertently dump the collective, tremendous downward pressure will be exerted on the floats. On land, the ground will press back and not much will happen. On water, a float will submerge and the rotor disk will hit the water. You don't want to know what happens when a rotor hits the water.

Fourth Rule: Have zero degrees incidence in the collective at the bottom until you know what you are doing.

Training Aid and Comments from Pat Jacobs
 
Quote:

I had been using a hula hoop to practise on land and found that it worked quite well. Not wanting to spend a whole lot more money on purchasing floats, the idea of using a pool noodle and wrapping it around the hula hoop came to me. 

I attached the noodle to the hula hoop with plastic ties and used a plastic pop bottle (cut off at both ends) and inserted the 2 ends of the noodle into it. It was a fairly snug fit, so nothing further was needed.

As I was still fairly new to helicopter flight, I at this point could hover the helicopter quite successfully, nose out. I had not been able to perfect hovering nose in or sideways. Given this, I can say from experience that I should not have proceeded any further or higher until I was more experienced at doing the above. The present condition of my helicopter is evidence of this. Nonetheless, I took my helicopter up to the lake and was quite anxious to try it on water.

Having only spoken to a couple of people regarding flying over water, and only having had experience flying off land, I was not sure what I was in for. On doing the normal checks and setting the helicopter on the water and getting ready to lift it off the water, I was not prepared for what happened next. Due to the fact that the noodle faced little resistance on the water, it immediately started to rotate and drift towards the dock. I had visions of pressure-treated wood all over the place. After the initial shock, I countered with more tail rotor and successfully hovered off the water.

I would have to repeat to anyone that's considering helicopter flying that unless they perfect nose in/nose out left and right flight 12 inches above the ground they should not attempt to go any further. This, by the way, was repeated in information that I read and people I spoke to. But overconfidence got the better of me and that is why today the helicopter is resting in pieces. I am on the lookout for a used Nexus 30.

Unquote

Fast Forward Flight

The addition of such a large surface to the bottom of the heli induces a huge amount of drag. This drag has quite a moment arm. There is the tendency for the aircraft to "trip" due to this extra drag.

Move forward slowly on your first flights until you find out how severe this condition might be.

Search and Rescue
 

In light wind, a heli can be used to great effect to blow back a deadstick fixed wing to shore.

In the photo, heli pilot Jim Moss aids Jack Mothersill's Beaver.

The photo was taken at Darlington Provincial Park during the Oshawa Club's Wednesday evening float flying.

[Revision 4 dated 13 Feb 2001]
 


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