WorksheetsRecap : Helicopter Ground Resonance
Total questions: 12
Worksheet time: 6mins
A helicopter lands hard and, while the rotor is still turning at low RPM, the airframe begins to oscillate side to side. Which immediate action should the pilot take?
Immediately increase collective to climb away
Apply forward cyclic input to counter the motion
Shutdown the engines to stop the oscillations
Maintain the current RPM and monitor the vibration
During a pre‑flight walk‑around, the pilot discovers that the landing‑gear oleo struts are under‑inflated and the damping shock absorbers show excessive wear. Which safety risk does this condition most directly increase?
Ground resonance during take‑off or after a hard landing
Engine overheating due to reduced airflow
Fuel starvation caused by clogged fuel filters
Tail‑rotor blade stall while hovering
Which of the following actions is not an effective method for preventing ground resonance in helicopters with fully articulated rotor systems?
Maintain proper tire pressure on the landing gear.
Perform a high-RPM takeoff immediately after detecting a hard landing.
Avoid hard landings by using smooth collective inputs.
Conduct regular inspections of the landing-gear damping components.
A helicopter on the ground develops rapidly increasing vibrations while the rotor is at about 95% of normal cruise RPM. What is the most effective immediate action for the pilot?
Reduce collective to lower the rotor speed
Maintain current RPM and wait for the vibration to subside
Immediately attempt a takeoff
Shut down the engines
Which of the following is NOT a primary cause of ground resonance in a helicopter with a fully articulated rotor system?
Excessive fuel imbalance in the aircraft's fuel tanks
Improperly maintained landing-gear damping system
Hard ground contact during a landing or take-off
Asymmetrical mass distribution of the rotor blades
A helicopter is on the ground after a hard landing, the rotor is turning at about 70% of normal cruise RPM, and the pilot notices the first signs of side-to-side oscillation indicative of ground resonance. What is the most appropriate immediate action?
Attempt an immediate takeoff at the current RPM
Increase collective to raise blade pitch
Shut down the engines immediately
Reduce the rotor speed further
Which rotor-system configuration is most susceptible to ground resonance?
Rigid rotor system
Fully articulated rotor system
Coaxial twin-rotor system
Semi-rigid rotor system
Which of the following best describes ground resonance in helicopters?
An aerodynamic flutter of the main rotor blades that only appears during high-speed forward flight.
A self-excited vibration that occurs when the rotor system and airframe interact with the ground, causing rapid side-to-side oscillations.
A pilot-induced oscillation that results from excessive cyclic input while hovering at altitude.
A structural resonance caused by engine torsional vibrations transmitted through the drivetrain in flight.
A helicopter on the ground develops severe side-to-side vibrations while the rotor is at high RPM (≈80% cruise). The pilot initiates an immediate takeoff. Why is this the most effective action for stopping ground resonance?
It lowers the rotor speed, moving the excitation frequency away from the resonant condition.
It cuts engine power, removing the source of vibration.
It frees the airframe from ground constraints, allowing the rotor’s balance to be restored by aerodynamic forces.
It activates the flight-control autopilot, which damps the oscillations.
To prevent ground resonance caused by asymmetrical mass distribution, which maintenance action is most effective?
Practicing smooth lift-off techniques during takeoff
Regular inspection of landing-gear damping components
Maintaining correct tire pressure on the landing gear
Proper blade tracking and dynamic balancing of the main rotor
During a ground run-up, the pilot applies excessive collective while the helicopter is still touching the ground. Which effect most directly raises the risk of ground resonance?
The rotor speed spikes, creating a shaft imbalance
The collective lock aligns all blade pitch angles, preventing vibration
Asymmetrical ground contact causes blade flexing and shifts the rotor’s center of mass
The landing-gear damping system becomes overloaded and loses effectiveness
During a pre‑flight walk‑around, the pilot discovers the main-gear tires are inflated to 150 psi, exceeding the POH-specified 120 psi. Which outcome is most likely if the helicopter is flown without correcting the tire pressure?
Reduced fuel consumption during cruise
Increased risk of ground resonance due to reduced landing-gear damping
Significant reduction in main-rotor RPM during hover
Enhanced ground-handling stability and smoother landings
