ACS Alignment

FAA-S-ACS-8 — Instrument Rating–Airplane & Helicopter · Area of Operation II. Preflight Procedures · Task: B. Aircraft Flight Instruments & Navigation Equipment

IR.II.B.K1 — pitot-static instruments & errors ⚑ IR.II.B.K2 — gyroscopic/AHRS & magnetic compass ⚑ IR.II.B.R1 — risk: instrument failure recognition ⚑ IR.II.B.S1 — verify instruments/avionics for IFR ⚑

⚑ FLAG (Walter): code letters/numbers are best-fit to FAA-S-ACS-8C Area II, Task B — confirm exact K/R/S identifiers against the current ACS.

Flight Instruments & IFR Systems

Knowing what each instrument senses, how it can lie, and what powers it.

By the end of this lesson you can:

Explain how the pitot-static instruments (altimeter, airspeed, VSI) work and their common errors.
Describe gyroscopic / AHRS attitude and heading sources and the magnetic compass errors.
Identify what powers each instrument and the failure signature of a lost source.
Confirm the aircraft's installed IFR instruments and avionics are working before flight.

1 · The pitot-static system

The altimeter, airspeed indicator, and vertical speed indicator are driven by the pitot-static system — the airspeed compares ram (pitot) pressure to static; the altimeter and VSI use static only. A blocked static port makes the altimeter freeze, the VSI read zero, and the airspeed read inaccurately; the AIM and IFH describe using the alternate static source and the resulting indication shifts. Set the altimeter to the current setting and know your field elevation as a cross-check.

2 · Attitude, heading & the compass

Instrument	Senses	Typical power / source
Attitude indicator (or AHRS)	Pitch & bank	Vacuum/electric gyro or solid-state AHRS
Heading indicator / HSI	Heading (slaved to magnetometer)	Vacuum/electric or AHRS/magnetometer
Magnetic compass	Magnetic heading	Self-contained (no power) — the backup

The magnetic compass is independent but has turning and acceleration errors (remember ONUS: Overshoot North, Undershoot South; and ANDS: Accelerate-North, Decelerate-South). Know which instruments fail together when a single power source (e.g., the AHRS or a bus) is lost — that pattern is how you'll catch a partial-panel situation early.

3 · Watch

Curated reference clip — “The Pitot Static System Explained (for IFR Pilots)” · Free Pilot Training (YouTube), verified via oEmbed. Embedded with the creator’s player; we don’t host or alter it.

4 · Reference sources

Use the authoritative references

📄 Instrument Flying Handbook (FAA-H-8083-15B) — Flight Instruments 📄 AIM — Instrument systems & errors

Your aircraft: the R44 POH avionics/instrument section lists the installed instruments, their power sources, and the alternate static source (if equipped). Confirm what's installed on the specific airframe.

QA flag: confirm IR ACS codes (FAA-S-ACS-8C) and re-verify instrument power sources and compass-error mnemonics against the current IFH before publishing.

✍️ Fill in for the aircraft you fly Attitude/heading source (AHRS vs. gyro), and what an AHRS/bus failure takes out: Look it up in the R44 POH (avionics/instrument section) and confirm with your CFI.

Risk management (the "Consider"): instrument failures rarely announce themselves — a slowly-failing AHRS or a creeping static blockage can lead you somewhere bad before you notice. Cross-check constantly (attitude against airspeed/altimeter/VSI trends), know which instruments share a source, and the moment two disagree, suspect the instrument, not the aircraft.