MIKE SATREN — During his pre-first-flight briefing Monday, Burt Rutan said the most fun one can have at an airport is to watch the first flight of a totally new airplane design.
According to that definition, a couple dozen people had their best day at Coeur d’Alene Airport (KCOE) watching Rutan’s amphibious SkiGull successfully take to the air.
In immediate attendance at the briefing were Rutan and his wife, Tonya, SkiGull systems engineer/builder and communications chief (CAPCOM) Brent Regan, SkiGull engineer/builder Dale Martin of Lewiston, SkiGull engineer/builder Joa Harrison, Certified Flight Instructor/FAA Designated Examiner and author Mike Kincaid of Mountain Lakes Seaplanes, test pilot Glenn Smith, Aerocet CEO Tom Hamilton of Priest River and KCOE Airport Manager Greg Delavan.
With snow in the forecast Monday evening and with high-speed taxi tests completed on Sunday, Rutan chose to go with the first flight of his 47th unique manned aircraft design flown by Smith. As with his previous designs, Rutan prepared a flight test regimen intended to answer questions about handling, three-axis stability, high airspeed and low airspeed numbers, plus its behavior when the ski landing gear and the single center flap are cycled up and down, each alone and both together. Specific stall testing was purposely left for a subsequent flight test.
The complete flight test card designed by Rutan did not include any maneuvers that would put Smith in any needless danger. All tests were conducted at an altitude and within a glide-capable, engine-out cone above the approach end (west end) of Runway 6 at KCOE. Rutan’s plan was to let Smith get comfortable with SkiGull and, after the required tests, to just have some fun with her.
During the test flight, Kincaid flew his Super Cub on floats with Rutan in the back seat as Chase Plane One and Hamilton flew his Cessna 182 with CAPCOM Regan, recording engineer Harrison and videographer Scott B of Antenna Films in Agoura, Calif., as Chase Plane Two.
Land taxi testing a couple weeks previous had destroyed several of the main landing gear ski’s plastic wheels. While the nylon-sleeved bearings were intact, the plastic wheels had overheated and melted from the compression pulsing of the weight of the aircraft. These had been replaced with aluminum wheels with ball bearings for Sunday’s final high-speed taxi tests. After the successful taxi tests, I drove Rutan and Regan behind Smith as he taxied SkiGull when Rutan remarked how well everything had gone.
Immediately, Regan said, “Don’t say that, it’ll jinx it.”
Sure enough only 200 yards from Rutan’s hangar, smoke appeared from the only remaining plastic wheel, the tail wheel. After alerting Smith by radio to stop, Regan jumped out with a fire extinguisher but the smoke had already dissipated. SkiGull was pushed the rest of the way to the hangar with Regan carrying the tail on his shoulder.
Rummaging through Rutan’s collection of wheels, Regan chose an aluminum ball-bearing wheel that was a little too wide and a little too large in diameter. He immediately headed for home and by 8 p.m. had texted Rutan that he had machined the aluminum to the proper width and the hard rubber outer tire to the correct diameter. Monday morning Regan installed the new tail wheel before the pre-first-flight briefing.
With everyone in his or her assigned places, Smith started SkiGull’s Rotax 912iS engine and immediately began to taxi. SkiGull has no brakes except for a maple center keel that brakes against the hard ground surface when the ski gear is fully retracted.
With both chase planes trailing, SkiGull applied power and was almost immediately airborne; its glider-like wings jumped at the chance to fly. Smith kept the climb gradual with the skis extended as he felt SkiGull’s controls and monitored the Rotax engine’s performance. Finally he made a left turn to the north while Chase Plane One and Chase Plane Two took off and loosely formed up.
SkiGull was in the air for a total of 1.8 hours as Smith worked his way through the test card, then it was time for Chase Plane Two to get in close for video and photographs.
The first flight tests proved SkiGull to be dynamically, positively stable in each axis. When the skis were cycled down and up and the center flap on the back of the wing was cycled down and up, SkiGull’s attitude (nose up or nose down) changed very little when each of these was cycled independently. The combination of both being lowered and/or raised together canceled any changes in attitude.
Because of its thin, laminar-flow wing, Rutan was not surprised by SkiGull’s lack of pre-stall buffeting. Most aircraft signal an impending wing stall with some buffeting. SkiGull will need some changes to give its pilot that early-warning of an impending stall but Rutan has at least a half-dozen ways to accomplish that and none of them are that difficult.
As Smith brought SkiGull in for its first landing, he kept the wings level and gently touched the skis on Runway 6. Then first the left wing dipped, then the right wing. A snap was heard and then a scraping sound as SkiGull listed to the right.
Smith kept everything under control and taxied off Runway 6 at Intersection G, only a couple hundred yards from its initial touchdown spot.
The right ski had partially delaminated in the same place where it first delaminated in late June just prior the EAA’s AirVenture in Oshkosh where Rutan had intended to present SkiGull to the world. After viewing photographs and video, Rutan ventured that the left wing had stalled as the weight was settling on the gear, which dropped the left wing and with that the left ski built up a degree of asymmetrical spring strength. That in turn pushed up the left wing and simultaneously dropped the right wing, which proved too much for the repaired right ski as sudden loads were placed on it.
Rutan plans to build new, stronger skis using an autoclave (pressure) process, which will greatly increase the ski’s integrity. He also plans to add two more wheels to each ski, centered between the current wheels to prevent any surface abrasion when the ski bends under a load.
Hamilton, who has pioneered many aircraft himself (Stoddard-Hamilton’s Glasair and Quest’s Kodiak), called the flight test of SkiGull eminently successful. Rutan shared his enthusiasm as SkiGull’s crew and friends gathered in Rutan’s hangar for the informal debriefing and celebratory toasts.
Over the winter Rutan will address the wing-stall buffeting, the new landing gear skis, plus repositioning the pitot tube (airspeed indicator sensor) from the front fuselage to somewhere on the wing.
He also has plans to address the nose-low water taxi tendencies.
Rutan pledged to keep working on SkiGull to achieve his intended goal to make it the first seaplane capable of landing and taking off in ocean swells and to be able to beach through ocean surf.
Nobody said it would be easy and Rutan himself said, “If 50 percent of people don’t think it’s impossible, it’s not research — it’s just development.”
Text and photos courtesy of Mike Satren