Skimmer & Lake Aircraft Operations (III)

Lake Amphibian operation, Part 3

Rather than go into details of checklists and run-up procedures, we will skip over to taxiing and takeoff. Since the nose gear is castering, steering is done with differential braking and one must be moving before the Lake can be turned. It helps to have the nose wheel pointed in the right direction before moving, especially in a tight spot. A healthy push on the side of the nose will usually do the trick. Using enough power to move forward, apply brake and rudder in the direction of the turn, and the opposite for changing direction. A little extra taxi speed helps maintain direction. Do not “ride” the brakes. A bit of practice in an open space will soon have you comfortable. There is a damper to stop nosewheel “shimmy” located just above the nose wheel fork. Too tight makes for difficult steering and too loose results in a “shimmy” at faster speeds.

There are springs attached to the pilot’s control yoke to enhance “feel” and the normal position is slightly nose down elevator, so for takeoff we want the elevator held slightly up. The trim tabs should be set in the top of the green arc, or visually about 40 degrees up. Bear in mind that there is considerable nose down thrust from the engine at full power. Flaps should be in the down position for every takeoff and landing, land or water. Increase the throttle smoothly forward for takeoff. Stay off the brakes since you will have immediate rudder control. A bit more back pressure should have you flying at about 60 mph. Assume a positive climb angle, maintain 65 mph and retract the gear, and climb at 65 to 70 mph. The flaps are the slotted type, or slow speed, high lift variety. If you try to climb with very little angle of attack, the climb rate is poor. However, by increasing the angle and climbing at the above speed you should see a respectable climb. After reaching about 500 feet of altitude, lower the nose to increase the airspeed, raise the flaps, trim down immediately, and climb at 85 or 90 mph. The main reason for not retracting the flaps until 500 feet of altitude is attained is to give the pilot time to select flaps down in the event of a forced landing after takeoff.
Control direction, thrust and “P” factor with the rudder only. When the desired cruise altitude is reached, lower the nose to level, allow the airspeed to increase to cruise, trimming nose down as speed increases. Finally, reduce the power setting to cruise power. If you should reduce the power before the proper attitude and cruise speed is reached you will be half-way to your destination before proper cruise airspeed is attained.

Landing gear, flaps and trim are hydraulically operated and reasonably trouble-free with a little preventive maintenance. Pressure is maintained by an electric pump operated by a pressure switch set to turn on at about 700 psi and off at about 1100 psi. There is a hand-operated auxiliary hydraulic pump in the event that the electric pump fails. An accumulator in the system assists in rapid gear retraction and extension. Preventive maintenance generally consists of occasional “O” ring replacement and periodic replacement of flexible hoses.

The Lake is a “rudder” airplane and one of the best aircraft to demonstrate adverse yaw with. If one attempts to turn with aileron alone, the nose immediately slews in the wrong direction and stays that way throughout the turn. Almost perfectly coordinated turns can be made with the rudder alone, and due to the dihedral of the wings will remain in a turn when properly trimmed with no input from the pilot.

Content and pictures courtesy and copyright of John Staber, Owner of Colonial Skimmer SN #1; John has flown and worked on Colonial Skimmers since 1964. In 2011 he published a book on the restoration of N6595K which can be purchased on his website: http://jstaber.com/books/skimmer/ If you are interested to learn about Skimmers and Lake Amphibian Aircraft, come visit and chat with John on www.seaplaneforum.com

Skimmer & Lake Aircraft Operations (II)

Lake Amphibian operation, Part 2

Here is where a few minutes should be spent talking about the configuration of the Lake Amphibian. The pylon mounted, pusher engine is unique and a lot can be said about it. It is very safe structurally being stressed for over 20 Gs. It is also safe in the respect that one cannot walk into the propellor and sand and gravel do not get picked up. It is susceptible to debris going through the propellor from the engine compartment, as mentioned in Part 1.Water erosion is at a minimum and only during transition from displacement to the step attitude.

This can be minimized by certain techniques and observing the proper weight and balance. One must remember that nose down thrust with power application will do just the opposite of a “tractor” mounted engine. Nose down with power application, nose up with power reduction. This works to our advantage in several situations. However, one cannot “hang it on the prop”, as done with the tractor engine. One must have forward speed and sufficient lift in order to takeoff or climb. It is also important to make sure that the nose oleo and tire are inflated properly to prevent flattening the tire and fully compressing the oleo upon power application.

The engine is easy to work on unless you don’t like being 6 feet up in the air. A simple platform made of 3/4 inch plywood and a couple of ladders, helps. A “gofer” on the ground is a plus, in case you drop something, or need a wrench that you left below. Just don’t step back to admire your work.

Engine placement, fuel supply, baggage compartment, and main landing gear are all on or near the MAC or mean aerodynamic chord which results in the CG moving forward with addition of passengers…more fuel brings it aft. An empty Lake is a pleasure to move on the ground. Simply lift the nose almost to the balance point on the main gear and move it around with abandon. If you need help, have the pushers inboard near the cockpit to avoid “asymmetric thrust” making you work harder to steer.

The aforementioned nose down and up thrust is not a problem, nor dangerous…just different. Therefore, for every power change, there should be a pitch change and a trim change. Power off, pitch down, trim down; power on, pitch up, trim up. If you don’t do anything and let it fly hands off, it will behave quite normally. Power off, the nose will come up and as the airspeed bleeds off, the nose will come down and a glide will commence. Power on will momentarily push the nose down, but as the speed builds up it will return to a more normal cruise attitude. A little bit of practice on the first flight will show you what to expect. Because of this tendency, the general rule is never add full power abruptly when close to the water or runway. Add half power, stabilize the attitude, then full power. If conditions are right it will almost land itself and will take off from water from dead stop, hands off!

Content and pictures courtesy and copyright of John Staber, Owner of Colonial Skimmer SN #1; John has flown and worked on Colonial Skimmers since 1964. In 2011 he published a book on the restoration of N6595K which can be purchased on his website: http://jstaber.com/books/skimmer/ If you are interested to learn about Skimmers and Lake Amphibian Aircraft, come visit and chat with John on www.seaplaneforum.com

Skimmer & Lake Aircraft Operations (I)

Lake Amphibian operation, Part 1

This is part one of a series of ten articles made available by John Staber, Owner of Skimmer One.

It is not the intention of these pages to teach one how to fly the Lake Amphibian, but to give an overall view of the operation of Lakes. It is written by a person who has owned 16 Lakes and Skimmers since 1964, and instructed in them since 1967 and accumulated over 5000 hours in all makes and models. It is highly recommended by Lake instructors and Lake pilots alike, that one get training from a Lake qualified instructor for both land and water operations. The Lake is not a difficult aircraft to fly (in fact, flown properly, it is quite forgiving), but is different enough so that both the high time and low time novice in the Lake can make unfortunate mistakes.

Preflights: yes, two of them. One for the aircraft and one for the boat. The aircraft preflight is similar to any other except one must climb up on the cabin roof to examine the engine and its related items. Always step on the rivet lines where it is stronger, even though the first leading edge skin on the wings is of heavier aluminum just for this purpose (also diving from). One should never install wing-walk material on Lake wings. Take extra care to ensure that all screws and bolts are tight, since if they decide to leave the plane, they are going to get help from the pusher propellor. Should there be any oil leaks, it becomes quite obvious as compared to the standard “tractor” engine where the oil is on the belly of the plane. The Lycoming 0-360 and I0-360 have an 8 quart oil capacity. It is recommended that they be filled to 7 and kept up to 6 quarts because of the slight downward angle of mounting. The control surfaces are all operated by push-rod tubes except from the wing root to the control wheel and should be checked for full travel since water flying calls for their full deflection at certain times. Landing gear should be checked for hydraulic leaks at the actuators and flexible lines and the shimmy damper checked for proper tightness and cleanliness. The trim actuator in the vertical fin should be checked, likewise. The flap actuator is in the fuselage under the propellor on the left side. Should the battery be mounted under the floorboards or in the baggage compartment, the vent and tightness of the terminals should be checked regularly to avoid sparking in the closed confines of the hull.

The boat preflight is just as important. Since the hull is watertight (or supposed to be) it will hold water or whatever else that can get in. It will take on water in a rain storm. If there is a fuel leak or hydraulic leak it will remain in the hull. There are plugs in the lowest part of each watertight compartment; one in each float, one on each side of the nose gear, one at the step, and two in the rear-most compartment behind the wings. Seven in all. They should be kept lubricated to prevent seizing and be snug, not super tight. The most aft plug should be drained when the tail is the lowest point of the Lake, as when nosed up on a steep beach. It is most important that they all be in place before a water landing is made. Check the operation of the water rudder at this time. There has been much concern lately about transporting biological growth from one body of water to another. Now is the time to remove any growth or weeds clinging to the hull, water rudder or landing gear!

Content and pictures courtesy and copyright of John Staber, Owner of Colonial Skimmer SN #1; John has flown and worked on Colonial Skimmers since 1964. In 2011 he published a book on the restoration of N6595K which can be purchased on his website: http://jstaber.com/books/skimmer/ If you are interested to learn about Skimmers and Lake Amphibian Aircraft, come visit and chat with John on www.seaplaneforum.com