ACS Alignment

FAA-S-ACS-16 — Commercial Pilot, Rotorcraft–Helicopter · Area of Operation VIII. Emergency Operations · Task: G–J — Antitorque Failure, Dynamic Rollover, Ground Resonance & Low-G

CH.VIII.G.K1 — antitorque/tail-rotor failure & LTE CH.VIII.H.K1 — dynamic rollover & the critical angle CH.VIII.I.K1 — ground resonance recognition & response CH.VIII.J.K1 — low-G recognition & recovery (Robinson)

⚑ FLAG (Walter): combines the largely knowledge/oral Tasks G–J of Area VIII — confirm codes; note several are evaluated by oral discussion, and the low-G item is Robinson-critical.

Antitorque Failure, Dynamic Rollover, Ground Resonance & Low-G

Four ways a helicopter bites near the ground or with abrupt control — recognize each and respond correctly.

By the end of this lesson you can:

Describe antitorque (tail-rotor) failures and loss of tail-rotor effectiveness (LTE) and the responses.
Explain dynamic rollover and why collective — not opposite cyclic — is the recovery.
Recognize ground resonance and the correct response.
State the Robinson low-G hazard and the correct recovery (aft cyclic first).

1 · Antitorque failure & LTE

A tail-rotor drive or control failure removes or fixes your antitorque, causing yaw that depends on power. General responses vary by failure type and may include reducing power and entering an autorotation or flying to a running landing — follow the POH. Loss of tail-rotor effectiveness (LTE) is an uncommanded yaw (often right, in US-rotation helicopters) at low airspeed/high power in certain wind azimuths; recover by applying pedal, lowering collective if able, and gaining airspeed.

2 · Dynamic rollover & ground resonance

Dynamic rollover: with a skid/wheel in contact, the helicopter can pivot past a critical angle beyond which rotor thrust completes the roll — recovery is smoothly lowering the collective, not opposite cyclic. Ground resonance is a destructive vibration that can build on the ground (associated with articulated rotors and landing-gear oscillation); the response is to lift off if rotor RPM is in the normal range, or if not, to close the throttle and lower collective to stop it — follow the POH.

3 · Low-G (SFAR No. 73)

Per 14 CFR Part 61, SFAR No. 73 (the Robinson R22/R44 special awareness training), an abrupt forward-cyclic input or a pushover can produce a low-G (near-weightless) condition. In the two-blade teetering rotor, low-G lets the tail-rotor thrust roll the aircraft to the right; applying left cyclic against the unloaded disc will not stop the roll and can drive the rotor into the mast (mast bumping), which is usually catastrophic. The SFAR 73 recovery is to immediately apply gentle aft cyclic to restore main-rotor (positive G) loading before applying any lateral cyclic to correct the roll. Prevention is primary — never make abrupt forward-cyclic inputs or pushovers in a Robinson.

4 · Watch

Curated reference clip — “HELICOPTER DYNAMIC ROLLOVER : Understanding this dangerous phenomenon.,” Fly High with Caro The Pilot (YouTube), verified via oEmbed. Embedded with the creator's player; we don't host or alter it.

5 · Reference sources

Use the authoritative references

📄 Helicopter Flying Handbook (FAA-H-8083-21) — Hazards (rollover, resonance, LTE) 📄 14 CFR Part 61, SFAR No. 73 — Robinson R22/R44 Awareness Training 📄 Robinson R44 POH & Safety Notices — Low-G / Mast Bumping

Your aircraft: the low-G, dynamic-rollover, ground-resonance, and antitorque-failure responses are aircraft-specific — note the R44 POH Emergency Procedures and the relevant Robinson Safety Notices (low-G/mast bumping).

✍️ Fill in for the aircraft you fly the R44 low-G recovery wording, the dynamic-rollover and ground-resonance responses, and the antitorque-failure procedure — look these up in the R44 POH/Safety Notices and confirm with your CFI.

⚑ FLAG (Walter): the R44 is a VFR-certificated piston helicopter; confirm the aircraft/figures the student actually flies and that all numbers come from the current R44 POH.

Risk management (the “Consider”): the Robinson-critical killer here is low-G mast bumping from an abrupt forward push followed by left cyclic. Per SFAR No. 73, never make abrupt forward-cyclic inputs or pushovers, and if low-G is sensed, immediately apply gentle aft cyclic to restore positive G before any lateral cyclic. For dynamic rollover, the answer is collective down, not opposite cyclic; confirm every response against the R44 POH and SFAR 73 awareness training.