Eric Robb RC Eric Robb RC RC Builds · Custom Parts · Backyard Engineering
Quick Answer · Troubleshooting

Why Won't My RC Airplane Fly?

Nine times out of ten it's one of six things: reversed controls, a tail-heavy CG, a backwards prop, too much weight for the wing, oversized control throws, or a weak power system — and every one is fixable on the bench, usually for free. After a lot of crashed foam board, I can tell you the symptom points straight at the cause. Tap what your plane is doing below and you'll get the reason and the fix.

Symptom Picker

What is your plane doing?

Pick the closest symptom — each answer is the pattern I see most, with the bench fix.

Symptom not here, or the fix didn't take? The Flight Doctor is the interactive version — describe your plane in your own words and it works out the actual cause.

The Full Tool

Get a real diagnosis, not a list

This page covers the six classics. The Flight Doctor asks about your specific plane — what it did, when, and after what change — and walks you to the exact cause, with the fix and the tools to prevent it.

Open the Flight Doctor → All tools

Worked example: diagnosing a tail-heavy zoom-stall

A reader's 30-inch plane with an 8-inch chord kept zooming up, stalling, and flopping over — classic tail-heavy behavior. The numbers: a safe CG on an 8″ chord is 25–33%, so 2.0″ to 2.6″ behind the leading edge. His plane balanced at 3.5″ — that's 44% of the chord, deep in dart territory. The fix cost nothing: slide the battery as far forward as the bay allows and re-balance on the marks. If it still won't come forward enough, glue coins to the inside of the nose. Tail-heavy is the one balance error that no pilot skill can fly around, which is why I check it before every maiden.

The most common mistake: launching again without changing anything

The plane crashes, it gets picked up, and it gets thrown again — same settings, same balance, same result, one more broken prop. A crash is data: something was wrong, and it's still wrong. Before the next toss, run the 30-second check from behind the plane — stick back raises the elevator, stick right raises the right aileron, CG on the marks with the flight battery in, prop numbers facing forward. And if the plane has crashed before, flex-test the wings: foam board hides creases that cut a wing's strength in half, which is exactly how my slow flyer folded a wing mid-air days after a "minor" crash. Brand new to the hobby? The Start Here path builds these checks in from day one.

Common Questions

Grounded planes, answered

Three suspects: a reversed or mistrimmed aileron, a warped wing, or unequal dihedral. Stand behind the plane and confirm stick-right raises the right aileron; sight down the wing from the tip for twist; and measure that both wingtips sit the same height above the bench. A wing that looks straight can hide a twist that no amount of trim fully fixes.
Pitch oscillation almost always means too much elevator throw, a slightly tail-heavy balance point, or both. Reduce the elevator travel, add 20–30% expo so small stick movements stay small, and nudge the CG forward toward 25–28% of the chord. Most first scratch builds are massively over-controlled.
If it lifts off and mushes back down, the wing is overloaded. Weigh the plane and check wing loading — weight divided by wing area — in the RC Calculators. A beginner foam plane wants light loading, under about 8 oz/ft². The fast fix is a lighter battery; the right fix is a bigger wing.
Lots of noise with weak thrust means the prop is on backwards — the raised size numbers must face forward. Thrust that fades and returns after a few seconds is the ESC's low-voltage cutoff protecting a tired or under-spec battery: land and check the pack. A plane that goes dead until you unplug and replug the battery had a brownout — hunt for a loose connector or an overloaded BEC.
Check for hidden crash damage first: foam board hides creases that cut a wing's strength in half. Also re-balance with the battery you're flying today — a different pack moves the CG — and flex-test the wings before trusting it again.
Next in the Eric Robb Builder System

Next: document the fix

Found it and fixed it? Save the plane's numbers — CG, throws, battery, trim — on a one-page spec sheet so the next maiden starts from what works.

Open the Spec Sheet Maker → All tools