If your RC glider keeps pitching up and down repeatedly during flight, you’re experiencing a problem known as porpoising. This oscillating motion is common for beginners and can make a glider feel unstable or difficult to control.
The good news? Porpoising is almost always caused by setup issues — not pilot skill — and is easy to fix once you know what to look for.
What Is Porpoising?
Porpoising is a rhythmic up-and-down pitching motion where the glider:
- Climbs
- Loses speed
- Dives
- Repeats the cycle
Left unchecked, it can lead to stalls or hard landings.
The Most Common Causes
1️⃣ Center of Gravity (CG) Is Too Far Back
This is by far the most common cause.
When the CG is too rearward:
- The glider becomes overly pitch-sensitive
- Small elevator inputs cause large reactions
✅ Fix:
Move the battery or add nose weight slightly forward.
👉 A slightly nose-heavy glider is safer for beginners.
2️⃣ Too Much Elevator Throw
Excessive elevator movement makes the glider overreact.
Symptoms:
- Sudden climbs after small stick inputs
- Difficulty flying smoothly
✅ Fix:
- Reduce elevator travel
- Add exponential (expo)
3️⃣ Flying Too Slowly
Gliders flown below their efficient airspeed will repeatedly stall and recover.
Common causes:
- Excessive up trim
- Aggressive thermal camber
- Trying to fly too slow too early
✅ Fix:
- Add a small amount of down trim
- Increase airspeed slightly
4️⃣ Improper Trim
Trimming in launch or thermal mode instead of cruise mode can cause oscillation.
✅ Fix:
Always trim your glider in Cruise mode at a comfortable speed.
How to Fix Porpoising Step-by-Step
- Check CG first
- Reduce elevator throws
- Add expo (20–30%)
- Trim in calm air
- Increase airspeed slightly
👉 Fix one thing at a time.
Final Thoughts
Porpoising feels scary, but it’s one of the easiest RC glider problems to solve. Once your CG and elevator setup are correct, your glider should fly smoothly and predictably.