DCT flies a direct leg from where you are now. Or enter an inbound course in °TRUE (e.g. 275) to fly a fixed line into the airport, like an OBS course.
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One download refreshes the airport list, the approach data (runway thresholds and elevations, ILS/LOC/glideslope) that the ILS picker, GS/GP and IAF heights are computed from, and every downloaded airspace country. All are then stored on this device for offline use. Once every 28-day AIRAC cycle, when online, the app checks (a few KB) whether the server has newer data and downloads only what changed; if you are flying an approach it waits and shows an Update banner instead. This covers all nav data (airports, approaches incl. ILS frequencies, airspace) but not terrain: terrain tiles load on demand and stay in their own cache.
GS/GP needles need the GPS to report ±20 ft or better vertically. Otherwise the PFD shows GS UNRELIABLE and only lateral guidance remains.
With TERR on, ground within 1000 ft below your GPS height turns from its height colour to amber, and red within 100 ft below or above you. The flight path is projected 60 s ahead along track at the current ground and vertical speed: TERRAIN (amber, “Caution, terrain”) when it would pass less than 500 ft above the ground, and PULL UP (red, “Terrain, terrain, pull up”, repeating) when within 30 s it would come within 100 ft. The required clearance tapers off within 5 NM of the destination runways so a normal approach doesn't alert; there are no alerts below 40 kt. Uses GPS height and the same terrain tiles as TERR (so alerts need TERR on). On iPhone, sound works after your first tap, at media volume. Advisory only — not a certified TAWS.
No airspace downloaded yet.
Height rule: an airspace is shown while your height is inside its vertical limits. A higher shelf only appears once you are within 200 ft below its floor (GPS height ≥ floor − 200 ft); airspace whose ceiling is below you is hidden. Use the slider under the map to preview another height; GPS goes back to following your GPS height. Flight levels are treated as altitude (no QNH correction); AGL limits use the destination elevation when within 30 NM, else terrain if downloaded.
Frequencies are shown only when the openAIP data has one for that airspace — none are invented. Countries are downloaded only near you and your destination (about 0.1–5 MB each) and kept for offline use; the data update below refreshes them. Airspace data © openAIP contributors, CC BY-NC 4.0. Not for navigation — always check the current AIP / chart and NOTAMs.
AH And DI App v. Not an approved instrument — situational awareness only. Courses are TRUE. Speed is GPS ground speed; height is GPS altitude, not barometric.
ILS / GPS GP (advisory only): the ILS softkey picks the approach at the active airport. AUTO prefers the most headwind from the METAR (cached offline), otherwise the runway best aligned with your GPS track. ILS and LOC use published localiser course, glideslope angle and antenna positions (FAA NASR for the US, public domain; elsewhere Robin A. Peel nav.dat 2013.10, GPL v2, so it may be out of date). They show green. Runways with no published ILS get a magenta GPS GP: a 3.0° geometric path crossing the threshold at 50 ft (OurAirports runway data), never labelled ILS. Needles are computed from phone GPS position and GPS altitude, not from a radio receiver. LOC full scale is the ±350 ft course width at the threshold (1–3°); GS/GP full scale (2 dots) is ±0.7°, and "ON GS/GP" shows within ±0.12°. The display arms inside 15 NM and ±35° of the course, captures within 12 NM and ±3°, and shows the vertical needle inside 10 NM. Never use for an actual approach.
Wind on the DI: surface wind at the active airport from its latest METAR (filled arrow on the compass rim, at the bearing the wind is coming from, pointing in toward the centre). A dashed arrow shows the TAF forecast wind. Directions are °TRUE, speeds in knots. Weather refreshes every 10 minutes while online, and the last report is kept for offline use with its age shown. Data from NOAA via metars.eu (fallback datamask.org). Not for operational briefing; always get an official weather brief.
This page isn't on HTTPS, so iOS will block motion and location. Open it over HTTPS (see the README).
Motion: close the app fully and reopen it. If it still won't ask, go to Settings → Apps → Safari → Advanced → Website Data, delete this site, then reopen. (On older iOS: Settings → Safari → Motion & Orientation Access.)
Location / Precise Location: Settings → Privacy & Security → Location Services → turn on, then Safari Websites → While Using the App and switch Precise Location on. Then close and reopen AH & DI.
Not certified for navigation. Phone attitude is gravity-referenced and can read wings-level in a sustained coordinated turn. Always fly by your aircraft's primary instruments.