I Built It Straight – Why Doesn’t It Fly Straight?

1. See "Hints for Setting Up Your New Airplane". When you are sure that your airplane is REALLY straight, go to the field and prepare for flight.

2. Takeoff woes: a) Airplane won’t taxi straight. Adjust nose wheel tracking (if trike gear); adjust tail wheel (tail dragger); adjust main gear toe-in. b) Engine sags. DO NOT TRY TO TAKE OFF! Richen needle, hold airplane in vertical position with engine wide open for ~10 seconds to check for sagging. c) Excessive elevator needed to break ground. DO NOT TAKE OFF. C.G. too far forward; not enough power; wing incidence wrong; design wrong (wing blanketing tail surfaces).

3. Straight and Level flight: Climb to safe altitude, hold back/turn pressure to maintain S/L flight. Use elevator trim to remove back pressure. Use aileron trim to remove turn pressure. If aircraft yaws, use rudder trim to correct, and adjust aileron trim accordingly. Check this both upwind and downwind until your airplane can fly at a constant altitude and heading for at least 4-5 seconds without banking, climbing or diving. Land.

3A. Ailerons: If trimmed left or right, check for the following: a) Warped wing. b) Alignment of wing WRT elevators—a high wing will cause a bank. c) Elevator halves not straight. d) Engine torque (ailerons trimmed for right bank). Change to a lower pitch prop; if less trim needed, you probably need more right thrust.

3B. Elevators: If trimmed up or down, check the following: a) C.G. (again!). b) Wing incidence. c) Engine down thrust. If you have down elevator trim for S/L flight, this is the most likely cause (but see 8. below).

4. Flying a Bank: Checks for dynamic C.G. Put your airplane into a steep bank (left or right), with the wing nearly vertical to the ground, and observe the attitude. If the nose drops, the aircraft is nose heavy; if the tail drops, it’s tail heavy. The aircraft will go down; what you’re looking for is the attitude as it falls.

5. Vertical (or nearly so) Climb: Checks for a heavy wing. From S/L flight into the wind, pull nearly vertical, and observe the aircraft. Do this a number of times to minimize anomalous flying conditions (wind gusts, wings not level at entry, etc.). If plane veers off consistently to the same side, check for a heavy wing on that side. Can use loops to accomplish this, also.

6. Wing Incidence: Aircraft zooms out of a dive; zooms after full throttle (too positive). Climbing turns (positive). Diving through the entire flight (negative).

7. Center of Gravity: See 4. above. Also, inverted flight requires excessive down elevator to maintain altitude (nose heavy). Airplane seems excessively ‘twitchy’ with elevator (tail heavy).

8. Engine Thrust: Airplane balloons up when engine power is cut suddenly (excessive down thrust). Too much right aileron (not enough right thrust).

9. Dihedral: Application of rudder gives good indication of dihedral. Airplane rolls in direction of applied rudder (too much). Airplane yaws or skids (just right). Airplane rolls out (too little). Dihedral affects roll rate, axial rolls, knife edge flight, banking turns, wing overs, tracking ability, and even S/L flight. It’s important!

10. Document what you do!