The Cessna 150 Floatplane
Our training airplane is a 1967 model 150G, originally powered by an O-200 Continental 4 cylinder engine producing 100 horsepower. It was upgraded to a 150 horsepower Lycoming O-320 engine to give it the extra power needed to make a really excellent float plane. This plane was prepared at the factory to become a float plane.
All the aluminum surfaces inside and out are coated with green zinc chromate paint to resist corrosion, and many reinforcements were added to beef up the airframe for the rigors of float flying.
You will also note that there are four lifting rings on top of the fuselage and a dorsal fin under the tail. The hooks are for lifting the plane to do float maintenance and repair. The dorsal fin restores positive yaw stability to the airplane making up for the large amount of float area forward of the center of lift.
The last feature common to floatplanes is a longer and flatter pitch prop. This yields increased low end thrust and better acceleration and climb capability.
The floats are EDO 1650-88. This means that each float can float up to 1650lbs. To be legally certified, each float must displace or float at least 85% of the max gross weight of the airplane which gives a good degree of safety in case one or both floats are damaged.
Each float contains five water tight bulkheads, each with its own pump-out port. This again adds a degree of safety in case of damage, but primarily it keeps any water in the floats from shifting fore or aft in flight, which could easily throw the plane out of C.G. limits.
The floats are constructed of aluminum and thousands of rivets, and should be mostly watertight while not in motion; the pounding of landing and waves will force some water through the seams. The keel of the float is actually very strong and provides much of the rigidity of the float system.
The float to airframe connection is extremely rigid. All forces are transferred from the floats to the airplane. This is the reason for the extra bracing and beefiness in the airframe.