The Intruder Takes Off in Bex

As a model maker for 35 years, designing a scale model of an airplane based on a blueprint of the real aircraft is a way to put all my knowledge and experience into practice. It is also what fuels a modeler’s passion and serves as a personal challenge. Today, many models are purchased ready-to-fly, and an interesting aspect of model building is disappearing. When designing a model, all areas of aviation are addressed: wing profile, center of gravity, material strength, engine power, electric and pneumatic systems, painting...

I’m not afraid of hard work. I’ve taken on a jet that isn’t available as a kit on the market: the Grumman A-6 Intruder, the famous American fighter-bomber deployed on

aircraft carriers. I like this jet not only for its unique shape but also for its wing layout, which lends itself well to scale modeling. A wingspan of 2.90 m strikes a good balance between flight performance and portability.

First fantastic flight!

The author "Chapi" and his new masterpiece.

Manufacturing molds from a “master.”

The target final weight is 25 kg. Based on my experience with the 3.20-meter de Havilland Venom (for which I sell kits*), I’ve stuck with an Airex sandwich-core fuselage and polystyrene-core wings. I built the fuselage “master” to produce the molds needed for the model. The landing gear is the work of an American craftsman. Its kinematics are superb: two pneumatic cylinders per leg that drive the retraction, plus a quarter-turn rotation during the final quarter of the stroke. Since the Intruder is a twin-engine jet, several options are available: two engines faithful to the original, one engine with a Y-duct, or a discreet exhaust outlet beneath the fuselage. I chose the latter solution. It caused me some problems when I first started the turbine, because the hot exhaust gases were burning the fuselage. After adding insulation, sheet metal, and some advice from friends, it gets less hot and everything is under control! The whole thing weighs 25 kg without fuel. Since the 5 liters of fuel weigh 4 kg, I’m just under 30 kg. Initial taxiing tests showed good acceleration, and the brakes help with ground control. For me, part of the challenge is already accomplished; the ultimate goal remains to fly at the Bex airfield for added safety.

After waiting all afternoon for a favorable wind, my Intruder is finally ready for its maiden flight. The 100-meter concrete runway should be enough for takeoff, and the 800 meters of the grass runway give me peace of mind. Full throttle! ... It accelerates well, but I’m already at the end of the runway. I pull back, and it takes off: it flies really well! It’s fantastic—no problems at all. I gain altitude and make a few circuits. Everything’s OK! I don’t need to adjust the trims, and even retracting the landing gear—which is quite heavy—toward the front happens

without any pitch correction. After six minutes of flight, I extend the flaps. The plane is still stable. I fly an approach pattern with all flaps extended. On the final approach, it descends at a steep angle. It keeps slowing down. I increase power for the final flare. I set it down gently. I apply the brakes: what a satisfaction! This first flight was a fantastic moment—especially with this plane, which I built from a blueprint and a scale model. We celebrated the occasion as it should be—with a fine bottle of wine—along with my “First Flight Dream Team”: Klaus Schillumeit, Yves Rossi, Pascal Ballet, and Pierre-Alain Vermot. I thank them all for their support!

*Laurent Chaperon*

*\*see <http://www.gamaigle.ch/bourse.html>*

Follow the construction steps:
http://www.gamaigle.ch/Projet_Intruder/intruder.html