# HI.XI.J — Ground Resonance — Flight Instructor Rotorcraft ACS

> HI.XI.J from FAA-S-ACS-29, including the official objective, references, notes, and 11 exact knowledge, risk-management, and skill descriptions.

Canonical HTML: [https://www.check-ride.ai/acs/rotorcraft/flight-instructor/hi-xi-j](https://www.check-ride.ai/acs/rotorcraft/flight-instructor/hi-xi-j)

Site reference: [https://www.check-ride.ai/llms.txt](https://www.check-ride.ai/llms.txt)

## Official Task context

- FAA document: Flight Instructor for Rotorcraft Category Helicopter Rating Airman Certification Standards
- Identifier: FAA-S-ACS-29
- Published source date: November 2023
- Aircraft category: Rotorcraft
- Certificate or rating: Flight Instructor
- Area of Operation: Area of Operation XI. Emergency Operations
- Task: Task J. Ground Resonance
- Task code prefix: HI.XI.J
- Official references: FAA-H-8083-2, FAA-H-8083-4, FAA-H-8083-9, FAA-H-8083-21, FAA-H-8083-25; POH/RFM
- FAA source library: https://www.faa.gov/training_testing/testing/acs

## Official Task objective

To determine the applicant understands ground resonance, can apply that knowledge, manage associated risks, demonstrate appropriate skills, and provide effective instruction.

## Knowledge elements

- **HI.XI.J.K1** — Exhibits knowledge of the elements related to ground resonance by describing:
- **HI.XI.J.K1a** — a. Conditions that contribute to ground resonance
- **HI.XI.J.K1b** — b. Preventive flight technique during takeoffs and landings
- **HI.XI.J.K1c** — c. Landing surface
- **HI.XI.J.K2** — Inspection of items that may contribute to ground resonance.
- **HI.XI.J.K3** — Corrective actions during low and normal rotor rpm speeds.
- **HI.XI.J.K4** — Common errors related to this Task.

## Risk management elements

- **HI.XI.J.R1** — Factors that may contribute to the onset of ground resonance.
- **HI.XI.J.R2** — Recognition of the onset of ground resonance.
- **HI.XI.J.R3** — Recovery procedure selection.

## Skills elements

- **HI.XI.J.S1** — [Intentionally left blank].

## Difficulty methodology

Difficulty calibration is ongoing for this Task. Observed difficulty is a privacy-thresholded check-ride.ai mock-oral practice proxy, not an FAA practical-test pass or fail rate. Underlying sample sizes and the private reporting threshold are not published.

## Official Task notes

- Evaluator assesses this Task orally only.

## Use in practice

A mock examiner can ask a pilot to explain the published elements, apply them to the configured aircraft and airport context, identify risks, and defend a decision. Practice prompts are not represented as actual FAA examiner scripts or predictions of the questions a candidate will receive.