# HI.II.D — Principles of Flight — Flight Instructor Rotorcraft ACS

> HI.II.D from FAA-S-ACS-29, including the official objective, references, notes, and 15 exact knowledge, risk-management, and skill descriptions.

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

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 II. Technical Subject Areas
- Task: Task D. Principles of Flight
- Task code prefix: HI.II.D
- 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 aerodynamics appropriate to the desired instructor certificate, can apply that knowledge, manage associated risks, demonstrate appropriate skills, and provide effective instruction.

## Knowledge elements

- **HI.II.D.K1** — Lift, weight, thrust, and drag.
- **HI.II.D.K2** — Airfoils, including terminology, definitions, and types.
- **HI.II.D.K3** — Torque effect and translating tendency.
- **HI.II.D.K4** — Gyroscopic precession.
- **HI.II.D.K5** — Blade flapping and coning.
- **HI.II.D.K6** — Coriolis effect.
- **HI.II.D.K7** — Pendular action.
- **HI.II.D.K8** — Dissymmetry of lift.
- **HI.II.D.K9** — Retreating blade stall.
- **HI.II.D.K10** — Translational lift, including effective translational lift (ETL).
- **HI.II.D.K11** — Transverse flow effect.
- **HI.II.D.K12** — Aerodynamics of autorotative flight.
- **HI.II.D.K13** — Rotor system characteristics.

## Risk management elements

- **HI.II.D.R1** — The basic aerodynamic principles of flight.

## Skills elements

- **HI.II.D.S1** — Deliver instruction on principles of flight, including at least three of the elements listed K1 through K13.

## 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.

## 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.