Turbine Moose: The Ultimate Amphib

The relationship between sailboats and airplanes is a strong one. Anyone who has ever hauled in the mainsheet on a sailboat knows the feeling of immense power the moment that big vertical wing achieves its critical angle of attack and begins to develop lift. The boat heels (rolls) downwind, and begins to accelerate forward. The tension on the mainsheet increases exponentially. Man has experienced that feeling for thousands of years, and it is a small wonder that we did not achieve flight hundreds, if not thousands, of years sooner.

Sailors are sprinkled liberally among the pilot population and vice versa. Rick Orchard, a sailboat racer, was introduced to flying when two pilot members of his racing crew convinced him to try it. Orchard bought a Bonanza, but was still drawn to the water. A trip to the Jack Brown seaplane base for a float rating, and he was hooked. That was 11 years ago. I met Orchard this spring at Sun n Fun, under the wing of his turbine Moose on amphibs, N24GR, an airplane that embodies his deep affection for float flying and his ability to get a grand-scale project done in record time to a high level of craftsmanship.

What’s With All the Teeth?

Orchard was wearing a cap that said “Grin Racing.” That is the reason for the Gulf Romeo in the N-number, and its the name of his sailboat racing team. The source of the team name seems logical: Orchard sports a mischievous grin that betrays his effort to look calm and relaxed. His mission-oriented approach to everything was obvious early, and as the story of the turbine Moose unfolded, it was confirmed.

On December 20, 2006, a Murphy Moose kit bearing the serial number 302 arrived outside Atlanta, Georgia. Eleven months later, to the day, November 20, 2007, the airplane flew off the land on its amphibious floats and made its second landing-on the water. You read that right: 11 months. How did they do it?

Orchard teamed up with veteran builder Doug Ripley, and together they worked full time to complete the airplane. Orchard had retired from a career in the cell phone communications industry. Much of his work was in project management, and those skills were useful and tested in the quick completion of the airplane. His original goal was to have the airplane ready for AirVenture. Ripleys standard response was, “What year?”

Project management in corporate America involves strict timelines with accountability in accordance with delivery schedules. Orchard surmised that, “The suppliers in the homebuilt industry have problems with dates.” That aspect proved frustrating for a highly motivated former corporate executive working on deadline.

Why a Moose?

Orchards previous seaplane was a BushHawk on Aerocet 3400A amphibs. Its a certified airplane built in Canada. Flying into the outback of British Columbia with his floatplane buddies, Orchard and his BushHawk, because of its size, hauled the gear. Orchards friends in their Super Cubs would drop into little lakes where the bigger and heavier BushHawk couldn’t get out. “I lusted for a turbine Beaver, the dream airplane for a bush guy,” Orchard said. “When you research the market, there isn’t much else out there to build (in that class) except the CompAir, and I wanted to build a metal airplane.”

So the next question might be: Why a turbine? “The simple operations, the reliability, and a floatplane with reverse has lots of applications,” Orchard said. Then he grinned and added, “Besides that, turbines sound cool.” The decision was made: a turbine Moose on amphibs. It had been done before, but that airplane was destroyed in an accident. The Moose kit was ordered, delivered, and the race to fly began.

Orchard enjoyed the building process. “What is cool about it is, its metal work, fiberglass work, electrical and plumbing work,” he said. “Just when you get sick of one thing, its done and you move on to the next.” To build a big airplane like this in 11 months, there was little time to get sick of anything.

“There is a wide variety in the documentation of kits. The Moose kit is just a bunch of big parts. Its pretty much up to the builder to decide how to put them together,” Orchard said. He and Ripley relied heavily on the support of other builders. “They all shared their experiences. Its not an exotic airplane, so we looked at the Cessna 185 and Caravan [for possible solutions].”

Even though the airplane is straightforward, adding a turbine engine and amphib floats complicates the process. Neither Orchard nor Ripley had any previous turbine building or operating experience, and that showed up in the starter switchology-more on that later.

Floating the Idea

They used the Aerocet 3400A floats from Orchards BushHawk. One of the challenges about floating an airplane for the first time is getting the floats center of buoyancy and the airplanes center of gravity in the right place so that the airplane flies and floats well. They gave their weight and c.g. estimates to Keith Kinden of Montana Floats, who designed and built the rigging. It all fit perfectly on the first try.

The turbine engine package came from Aerotek Aviation of Quebec City, Quebec. The firewall-forward started life on a C-12, a military version of a Beechcraft King Air 90. The engine is a Pratt & Whitney PT6A-20, an early version of the venerable PT6A. Later King Air 90s were upgraded to the -21, which would develop its 550 horsepower at higher altitudes and in hotter weather. The Moose is so overpowered that even on the hottest days, on the highest lakes, power should not be a problem.

Orchard and Ripley did a great job of making the engine look like it was meant for the Moose. Turbine conversions always involve moving the engine forward to compensate for the lighter weight of the engine, and sometimes these airplanes take on a Pinocchio appearance. This setup passes the TLAR test, “That looks about right.” The King Air forward cowl transitions nicely into the custom boot cowl. The exhaust stacks were extended to prevent soot buildup on the fuselage. The King Air engine mount was modified to attach to the firewall mounting points of the Russian Vedeneyev M-14P radial engine originally intended for the Moose. An additional attach point was built that connects the engine mount to the windshield bracing, which carries up to the front spar attach points.

One of the biggest challenges was heating and ventilation. The turbine has plenty of bleed air for heat, but it has to be cooled and controlled. That involved valves and intercoolers. Fresh air is also a challenge. Bringing in air from under the airplane brings water along; on the side of the fuselage there is exhaust, and on the top there is rain. The solution was found by bringing air in from the NACA ducts under the engine.

Extended wingtips add 20 inches of span, making room for 20-gallon auxiliary fuel tanks for a total capacity of 160 gallons, and together with a huge cabin create an airplane that could easily be overloaded despite the turbine installation, which itself makes the airplane roughly 60 pounds lighter than it would be with a comparable radial engine.

Upping the Gross

The Moose kit has a gross weight specification of 3500 pounds. The Aerocet 3400A floats weigh 650 pounds and are designed for aircraft up to 3775 pounds. The aerodynamics of the floats carry some of their weight. Considering all this, Orchard chose to set the maximum gross weight at 4000 pounds. At that weight, the finished airplane is slightly underfloated.

The Moose weighs 2795 empty, and with 120 gallons of main fuel, that brings it up above 3600 pounds before anything goes in the cabin. However, fuel can be traded for payload. Fuel for 2 hours of flight can leave more than 700 pounds of payload. Orchard understands that the combination of added gross weight, wingspan, fuel capacity and horsepower requires that the pilot be careful of turbulence, rough water or high indicated airspeeds. He tries to keep the airplane light, but there’s no getting around the inherent limitations of amphibious flying, which is costly in terms of weight.

Around the Lake with Popeye

I, too, am a sailor, and while I have the rating, flying seaplanes is a special treat I seldom get to enjoy. We pulled the Moose out of parking by hand to avoid blowing over the nearby tents. It is so tall and looks so large that pushing it on the grass seemed like a daunting task, but it rolled easily.

It is a long way up to the cockpit-the Moose sits higher than the King Air that donated the engine. The cockpit is roomy and neatly equipped with two Chelton EFISes, and an Electronics International EMS. The electrical switches were a combination of a simple single combined with the necessities of a turbine.

Something I noted to Orchard was one of the few miscues in the build. Piston-powered airplanes always use momentary switches for starters, and that was the case here. But turbine starters need to be turned on and left on until the start sequence is complete. Inadvertently taking a finger off the starter button at the wrong time could lead to a hot start that could melt a very expensive engine. Changing a push button to a rocker switch is an easy fix, however, and it may already be done. The rest of the airplanes systems and instrumentation were simple and intuitive. The EMS was a nice interface with the turbine, and soon we were taxiing to the active.

Some people say amphibs taxi like great big shopping carts. Because the mainwheels are set back and the nose tires caster, the arm on the rudder is short, and the brakes get a workout on a long taxi, but there is no alternative.

I fly my share of high-performance airplanes, and I know what to expect when turning 550 horses loose on an airplane that weighs around 3600 pounds. Even with that expectation, the result was a treat. The airplane accelerates quickly, and soon we were ready to rotate.

Everyone in Step, Please

Everything in aviation is a compromise. Floatplanes require more compromises, and amphibious floats add a third dimension to the bargain. There is a place on a float called the step, where the body and the tail of the float meet. It is on this step that the airplane rotates when it comes out of the water. The land plane equivalent of this point would be the axle on a tricycle airplane. It is not possible to locate the tire at the same point as the step, so it must be moved back into the tail. This results in the c.g. of the airplane being farther than optimum from the axle, and it takes a good tug on the elevator to pull the nose up.

On a normal amphib this would result in the initial pitch being too high to sustain. But the power of the PT6A just pulls the airplane wherever it is pointed, and it will climb at ridiculously high angles that preclude all forward visibility. Climb rates in excess of 2000 fpm are possible. Let the nose down to a more reasonable pitch attitude, and the airplane accelerates quickly. The result was predictable-a big grin.

Level off and pull the power back to 60% torque, and the airplane indicates 135 knots on 34 gph-climb to 8000 feet and that should yield 157 knots/180 mph true. But it gets better: This PT6A variant can maintain 60% power to 18,000 feet, where 135 KIAS equals a true airspeed of 180 knots. You just don’t think like that around amphibs.

Another thing about floatplanes is the side area on the nose of the floats reduces yaw stability. Couple this with the extended nose from the turbine installation, plus the internal friction in the water-rudder system, and the result is neutral yaw stability. If you push the nose left with the rudder, it stays there. If you push it right, it stays there, too. This may sound problematic, but it isnt. The airplane doesn’t sway; it just stays where its put. Anyone with the slightest amount of rudder awareness would have no problem flying it smoothly.

The ailerons seem a little sloppy at first, but looking at them while in flight, I could see the cause is lost motion in the control system. The ailerons droop with the flaps and reflex when the flaps are up. Ripley said they worked hard to resolve the issue, but could not do it. It is not objectionable, and in a few minutes I had forgotten about it.

We made the short flight up to Lake Agnes at the Fantasy of Flight Museum, which served as the seaplane base for Sun n Fun. There was a light chop on the water, and I slowed to 75 knots on final, checked the gear up for water, and put the flaps down. The airplane went on the water as smooth as silk, with just a touch of power. The composite floats absorb vibration and noise, and the ride on the water is smooth. I was apprehensive about pulling the power back abruptly on the step, concerned that flat prop pitch might blank out the tail. My fears were unfounded. The airplane settled easily into the water, and we idle-taxied to the ramp.

The turbine pulled up to the ramp easily, to the oohs and aahs of the assembled crowd. I tried to back into a parking space in the cow pasture turned amphibious parking ramp. The cows were gone, but evidence of their recent occupation warranted looking before each step. After a short visit, we fired up and taxied down the ramp for a water takeoff. Putting the gear up on an airplane not in flight is unnatural, but thats the drill. Taxiing downwind at idle was just fast enough that the floats were taking water over their bows. The choice was to reduce the prop pitch into beta range, or add power and step taxi. Step taxiing is a better choice, so we powered across the lake and turned into the wind.

A few lakes over, at Jack Brown, they teach the CARS checklist: carb heat, area, rudders, stick. There is no carb heat, but I cleared the area, retracted the water rudders, pulled the stick full aft and added power. The typical water takeoff involves coming out of the hole onto the step, lowering the nose, accelerating and lifting off. The turbine Moose takeoff is simplicity itself: Add power, pull back. The airplane stands on its tail, and as the nose is coming down onto the step, the airplane breaks free of the water and flies, again, at a ridiculously high angle unless you relax the back pressure. Another grin.

Pretty Pictures

The photo work is not usually part of an article like this, but it warrants discussion. A great way to find out how an airplane flies is to snuggle up close to another. If the airplane has bad handling habits, this will highlight them quickly. By the time we began shooting, I was one with the airplane. It responded to my commands without effort.

The photo platform was a Beech Bonanza A-36 with the rear doors removed; its owned and flown by well-known aviation photographer Scott Slocum, who graciously agreed to carry his competitor, Richard VanderMeulen, who shot the art that adorns these pages. The elements of a photo shoot are the photo platform, the subject plane, the pilots, the shooter, the background and the light. Thats a chain with seven links in it, and its seldom that all of the elements come together without one or two weak links. We had the chain hooked up, and the magic that you see on these pages is the result.

After several touch-and-goes on the water, in formation with the Bonanza, it was time to return to the pavement. Remember I mentioned how high the airplane sits off the ground? It must have slipped my mind, because on final for the concrete, just as I was beginning to flare, the tires touched, the trailing link gear absorbed the down force, and the result was a landing much better than I deserved. Call it the end grin.

It’s Bigger than the Package

A turbine Moose is not for everyone. Like any airplane that stretches the envelope, its an airplane that, if not properly respected, could lead to trouble. Its simplicity and pleasant personality conceal those traits, and I didn’t go looking in the corners for them.

Rick Orchard is a sailor. He knows the feeling of power in a boat when the mainsail is transformed from a parachute to a wing. Pushing the power lever on the turbine Moose gives him that feeling and makes him grin. He seems to have gotten some kicks from building the turbine Moose as well. He is already started on his next project, an even bigger turbine amphib called the Grizzly, based on a Lockheed AL-60 engine. Maybe he will register it as N24BG, Bigger Grins.

For more information on the Murphy Moose, call 607-792-5855, or visit http://ww.murphyair.com/. Contact Aerotek Aviation at 418-802-5278 or visit http://www.aerotekaviation.ca.