# Build & Fly Part of the Aviation Merit Badge Digital Resource Guide: [Introduction & Overview](https://merit-badge.university/merit-badges/aviation/guide/index.md) *2. Principles of Flight* > **2.** Do ONE of the following: This is where you take everything you have learned about lift, drag, thrust, and weight and put it to the test with your own hands. You will pick **one** of the three options below, build (or obtain) a flying machine, and fly it. Each option teaches a different set of skills. ### Option A: Build an FPG-9 Glider > **2a.** Build a model FPG-9. Get others in your troop or patrol to make their own model, then organize a competition to test the precision of flight and landing of the models. An **FPG-9** (Foam Plate Glider — 9 inch) is a simple, elegant glider made from a foam plate. It has no engine — you launch it by hand, and it glides on lift and momentum alone. The beauty of the FPG-9 is that small adjustments to the wing shape, tail angle, or center of gravity can dramatically change how it flies. **What you will need:** - A 9-inch foam plate (the kind used for picnics) - Scissors - A ruler - A pen or marker for tracing the template **Tips for a great FPG-9:** - Keep the cuts clean and symmetrical. Even a small unevenness can cause the glider to veer off course. - Adjust the **elevon** (the small tab at the back) up or down to control whether the glider climbs, dives, or flies level. - Move a small piece of clay or tape to the nose to adjust the center of gravity. A nose-heavy glider dives; a tail-heavy glider stalls. **Running the competition:** Set up a target landing zone (a hula hoop or a taped circle works great) and have each Scout launch from the same spot. Score based on how close each glider lands to the target. This tests precision and consistency, not just distance. > **Tip** > > The FPG-9 is a perfect way to see the four forces in action. When you adjust the elevon, you are changing lift. When you add nose weight, you are changing the balance of weight. Every tweak is a mini-lesson in aerodynamics. ### Option B: Build a Rubber-Band Airplane > **2b.** Build a rubber-band driven balsa wood airplane. Fly the plane for 25 feet in a straight line, with a smooth landing. A **rubber-band powered balsa wood airplane** uses a wound-up rubber band to spin a propeller, providing thrust. As the rubber band unwinds, the propeller pulls the airplane forward through the air, and the wings generate lift — just like a real piston-powered airplane. **What you will need:** - A balsa wood airplane kit (available at hobby shops and online) or individual balsa wood sheets, sticks, and a propeller kit - Rubber bands (the long, thin kind designed for model aircraft) - A small propeller and hook assembly - Glue, sandpaper, and a craft knife **Tips for straight-line flight:** - Make sure the wing is mounted perfectly level and centered on the fuselage. A crooked wing makes the airplane turn. - Adjust the **thrust line** — the direction the propeller pulls. If the airplane curves left, angle the propeller slightly to the right, and vice versa. - Add a tiny amount of "up thrust" (angling the propeller slightly upward) to prevent the airplane from diving when power is on. - Wind the rubber band consistently. More winds = more thrust, but too many can break the band. **Achieving 25 feet in a straight line:** This takes patience and many test flights. Launch gently — do not throw the airplane. Let the propeller do the work. Adjust after every flight until the airplane tracks straight. ![A Scout at a workbench assembling a balsa wood rubber-band airplane, with the fuselage partially built and the propeller and rubber band visible alongside building tools](https://ik.imagekit.io/doulacoop/tr:w-800/mbu-assets/merit-badges/aviation/guide/balsa-wood-airplane-build?v=55c0fea3) ### Option C: Fly a Powered Model or Drone > **2c.** Build (or obtain) a fuel-driven or battery-powered electric model aircraft or drone. Obtain The Recreational UAS Safety Test (TRUST) certification, and fly the aircraft with a successful take-off and landing. This option puts you in the pilot's seat of a powered model airplane or a drone. Before you fly, though, there is an important legal requirement: you must pass **The Recreational UAS Safety Test (TRUST)**. **What is TRUST?** TRUST stands for The Recreational UAS Safety Test. It is a free, online knowledge test required by the FAA for all recreational drone and model aircraft pilots in the United States. The test covers airspace rules, safety guidelines, and FAA regulations. It typically takes 20–30 minutes to complete. > **Safety First!** > > Flying a powered model aircraft or drone is real aviation, and the FAA treats it that way. You must: > > - Pass the TRUST certification before your first flight. > - Keep the aircraft within visual line of sight at all times. > - Stay below 400 feet above ground level. > - Never fly near airports, stadiums, or emergency response scenes. > - Never fly over people who are not part of your flight operation. > - Yield the right of way to manned aircraft — always. **Getting your TRUST certification:** The FAA has approved several free test providers. Visit the FAA's TRUST page for a list of approved providers. The test is free and you receive a completion certificate immediately. **Tips for a successful flight:** - Read the manual for your specific aircraft or drone before powering it on. - Find an open area free of obstacles, people, and overhead wires. - Start with a hover (for drones) or a low-altitude pass (for airplanes) before attempting a full takeoff-and-landing cycle. - Check wind conditions — gusty winds are challenging for beginners. - Always perform a pre-flight check: battery charge, propeller condition, control response. [FAA — The Recreational UAS Safety Test (TRUST)](https://www.faa.gov/uas/recreational_flyers/knowledge_test_updates): Official FAA page with links to free, approved TRUST test providers. Complete the test and download your certificate. [Academy of Model Aeronautics (AMA)](https://www.modelaircraft.org/): The national community for model aviation enthusiasts, with clubs, events, and safety resources for building and flying model aircraft. > **Be Prepared! What If Your Model Crashes?** > > Crashes are a normal part of learning to fly model aircraft. Here is what to do: > > - **Stay calm.** Retrieve the aircraft only after all moving parts have stopped. > - **Check for damage.** Look at the propeller, wings, and electronics. A cracked propeller must be replaced — never fly with a damaged prop. > - **Analyze what happened.** Was it wind? A control input error? A mechanical failure? Each crash teaches you something. > - **Repair and try again.** Most model aircraft crashes are fixable with glue, tape, or replacement parts. --- - Previous: [Flight Instruments](https://merit-badge.university/merit-badges/aviation/guide/req1h/index.md) - Next: [Flight Operations](https://merit-badge.university/merit-badges/aviation/guide/req3/index.md)