VOR, CDI & HSI
Read radials, the CDI and the TO/FROM flag — and see why reverse sensing happens.
Practice IR procedures until they’re reflex.
Real instruments — CDI, HSI, RMI — with rule-based feedback, not guesswork. Without the cost or pressure of a real flight.
9 modules · Runs in your browser · Built by a pilot
How it works
Four steps, the same every session. The third one is the point — the rule you missed, not a score — and the fourth is why it sticks.
01
Pick a module
From VOR radials to DME arc — each module builds on the one before it, in the same order you actually learn them in ground school.
02
Practice on the real instrument
Watch the CDI needle move, don’t read about how it should move. Every exercise is generated deterministically — replay the exact same situation until you’ve mastered it.
03
Get rule-based feedback
Not just “wrong” with no explanation — the exact rule you broke, like an instructor looking over your shoulder.
04
Repeat until it’s automatic
Every scenario is reproducible — run the same setup until the response stops being a calculation and starts being a reflex.
Try it right now
A question on the real HSI — no account, no sign-up and a new one whenever you want another.
The flag reads FROM with CRS 000 set and you're on heading 176. Are you getting further from the station?
Nine modules, one foundation: VOR and NDB
Nine modules, built in the order you actually learn them.
Instruments
VOR & radials
Read CDI deflection, TO/FROM and understand why reverse sensing isn't a bug — it's geometry.
NDB & RMI
Same logic, a different instrument — the RMI needle points straight at the station, no sector ambiguity.
Procedures (built on top of the instruments)
03 · Procedure
VOR intercepts
Calculate the intercept angle and lead the turn before the needle swings through center.
04 · ProcedureNDB intercepts
Same procedure, on an instrument that doesn't forgive a late turn.
05 · ProcedureVOR holding
The flagship exercise: direct, parallel, or teardrop entry — pick the right one from the start.
06 · ProcedureNDB holding
Holding, but with wind and drift that are harder to feel without a reference radial.
07 · ProcedureWind correction
WCA calculated and applied live — you feel the drift before you see it on the map.
08 · ProcedureProcedure turns
VOR and NDB in a single module — the exact sequence before the final approach.
09 · ProcedureDME arc
The synthesis: constant distance, continuous correction, without losing the radial.
Theory
The minimum you need before you fly it, and the reasoning behind it.
Instruments
Procedures
Intercepts
Read where you are, pick the intercept angle from the difference and lead the turn.
Holdings
Pick the direct, teardrop or parallel entry, then fly the racetrack by the clock.
Procedure turns
45°/180°, 80°/260° and the base turn: where you time and which way you turn.
DME arc
Join the arc with the right turn and lead, hold the distance, and leave it on time.
Technique
Wind correction
Work out the correction angle and the groundspeed in your head, before the drift shows.