Have a question or found a bug? Browse our FAQ or reach out directly — we respond within 24–48 hours.
Density Altitude Warning matches FAA E6B standards to within ±200 ft under standard atmospheric conditions. We use the pressure altitude and temperature-based formula consistent with FAA advisory circulars.
For personal verification, compare our reading against your own E6B or manual calculation using the same temperature and altimeter setting.
We use the standard FAA two-step formula:
Where ISA temperature = 15°C − (2°C × altitude in thousands of feet). This is the same method used in FAA written test questions and standard E6B calculations.
Yes — high humidity reduces air density and increases effective density altitude, though this effect is smaller than temperature. The FAA's standard DA formula does not include humidity (it uses dry air assumptions).
Our current calculation follows the FAA standard (dry air). We are evaluating adding a humidity correction factor in a future update. In the meantime, note that humid summer days may result in slightly higher effective DA than displayed.
Density Altitude Warning supports Apple Watch Series 4 and later running watchOS 7.0 or higher. The companion iPhone app requires iOS 16.0 or later.
For the best experience and largest alert text readability, we recommend Apple Watch Series 7 or later with the larger display.
The app uses GPS-based geofencing to detect when you enter the boundary of a known airport. When you arrive within approximately 1.5 nautical miles of an airport, the app automatically wakes, identifies the field, fetches the latest METAR, and begins monitoring.
You do not need to search, type an ICAO code, or manually launch the app. Airport detection happens silently in the background.
Go to Settings → Aircraft Profiles → Add Aircraft. Enter your aircraft make, model, registration (optional), maximum density altitude (from your POH), and minimum climb rate. You can save multiple aircraft profiles and switch between them.
If you didn't receive an alert, check the following in order:
If conditions were within safe margins for your aircraft profile, no alert is generated by design. Check the main app screen to confirm the DA reading.
Yes — fully functional offline. Density Altitude Warning is designed specifically for backcountry and remote operations where LTE is unavailable.
We use NOAA Aviation Weather Center as our primary METAR source — the same official government data used by ForeFlight, Garmin Pilot, and aviation weather services worldwide.
CheckWX API serves as our fallback source if NOAA is temporarily unavailable. METAR data is refreshed every 30 minutes at stations that report half-hourly, and every 60 minutes at standard stations.
The app displays the age of the current METAR observation. As a general guideline:
On hot summer afternoons, temperatures can rise several degrees per hour. A METAR that is 2 hours old on a high-DA day may significantly underestimate current conditions.
No. Density Altitude Warning is a safety supplement — not a replacement for official preflight planning.
Think of Density Altitude Warning as your always-on safety monitor — it catches the performance threat that pilots most commonly overlook, but your official preflight process must still be complete.
No. Density Altitude Warning is a general aviation safety tool for informational use — it is not FAA-certified avionics and does not hold TSO authorization. It is in the same category as other pilot tools and apps used for preflight planning.
The app is not intended for use as primary avionics in flight. Its intended use is on the ground during preflight to assess performance risk before departure.
Trust the numbers, not the sky. Density altitude is invisible — a clear, calm, beautiful day at a high-elevation strip in summer is exactly when DA kills pilots.
The app supports any piston-engine single or twin, turboprop, and experimental aircraft for which you have POH performance data. This includes:
Jet aircraft are outside our primary use case but the DA calculation remains valid for any aircraft type.
Your aircraft's performance limits related to density altitude are found in POH Section 5 (Performance). Key figures to note:
Enter the DA at which your aircraft's takeoff distance exceeds your typical runway, or where climb rate drops below your minimum comfort margin. This becomes your personal warning threshold.
Yes — completely. We never store, transmit, or share your GPS location, flight history, or airport visit records. Location data is used in real-time for the density altitude calculation and immediately discarded.
We do not build profiles of your flying habits, route history, or frequently visited airports. The only data that ever leaves your device is the airport ICAO code when fetching a METAR — nothing else.
See our full Privacy Policy →
Never. Your email address will never be sold, rented, traded, or shared with any third party for any commercial purpose. Period.
We use your email only to send you beta access invitations, product updates, and aviation safety content related to Density Altitude Warning. You can unsubscribe at any time from any email we send.
There is no account system — all app data lives locally on your device.
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