Lake Amphibian Operational Tips – Part 2 of 10
Guest Editorial Series by John Staber – 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! Read Part 3 of 10, next Wednesday on Seaplanemagazine.com
Text and pictures courtesy and copyright of John Staber, Owner of Colonial Skimmer SN #1; John has flown and worked on Colonial Skimmers since 1964 and has accumulated more than 5000 hours in all different makes and models. In 2011 he published a book on the restoration of N6595K which can be purchased on his website. If you are interested to learn more about Skimmers and Lake Amphibian Aircraft, there will be one new article per week, dealing with a new topic.