Two ground hazards that can flip or shake a helicopter apart.
By the end of this lesson you can:
Explain dynamic rollover: a pivot point, a rolling moment, and a critical rollover angle.
State the primary recovery (smoothly lower collective).
Describe ground resonance and the basic response (per POH).
Identify the situations (slopes, hung skid, lateral drift) that set up these hazards.
1 · Dynamic rollover
Dynamic rollover happens when the helicopter pivots about a fixed point — a skid caught on the ground, a slope, or a hung skid — and rotor thrust rolls it past a critical angle beyond which cyclic can no longer stop the roll. It develops fast at low altitude during takeoff/landing and on slopes. The decisive recovery is to smoothly lower the collective to reduce the rolling thrust; keep the aircraft level and drift-free to prevent it in the first place.
2 · Ground resonance
Ground resonance is a destructive vibration that can build when the rotor system's lead-lag balance is disturbed in contact with the ground (often a hard or one-skid landing), and the oscillation couples with the landing gear. It can damage or destroy the aircraft quickly. The response depends on the situation and the POH — generally, if RPM is in range you may lift off to break the resonance, or if shutting down, reduce RPM/close throttle per the POH. Smooth, level touchdowns prevent it.
3 · Watch
Curated reference clip — “Dynamic Rollover in Helicopters — Part 2,” Helicopter Lessons In 10 Minutes or Less (YouTube). Embedded with the creator's player; we don't host or alter it.
Your aircraft: confirm the R44 response to ground resonance and any critical-angle guidance in your Robinson R44 POH (Sections 3 & 4). The specific recovery for ground resonance is aircraft-dependent — verify it there.
✍️ Fill in for the aircraft you fly (N-________)
Value / limit:
R44 POH section & page:
Leave blank until you look it up in your R44 POH (see the reference above) and confirm it with your CFI. Aircraft-specific numbers vary with weight & conditions — don’t guess.
Risk management (the “Consider”): both hazards live at the ground interface during takeoff and landing. Dynamic rollover starts as a pivot about a skid — prevent it by staying level and drift-free, never forcing a hung skid, and lowering collective at the first sign of an uncommanded roll. Ground resonance starts with a hard or uneven touchdown — prevent it with smooth, level landings and immediate action per the POH if it begins.