Cosmic Radiation Exposure Calculation

Approach

FL3XX uses its own simplified estimation model. It does not use CARI (any version) or another external radiation model. The model is deliberately conservative: wherever an input is uncertain, it assumes the worst case. Calculated doses will therefore usually be higher than the dose actually received.

Typical business aviation crews stay well below regulatory limits, so this conservative estimate does not restrict operations. If you need regulatory-grade dosimetry, for example values that account for solar activity and the exact route flown, use a dedicated provider such as our ACD integration.

Which flights are included

• Every flight a crew member is assigned to, in any position, within the selected date range.
• Only flights with both an actual take-off and an actual landing time. Flights without these times are left out.
• Simulator sessions and ground duties are not included.

Inputs

For each flight, the calculation uses three inputs.

Flight time (T). The airborne time in minutes, from actual take-off to actual landing. Block time is not used.

Flight level (FL). The flight level recorded on the flight. If no flight level is recorded, FL3XX uses the aircraft's optimum flight level for that flight duration, as set in the aircraft settings. If none is set, FL400 is assumed.

Latitude (lat). The higher absolute latitude of the departure and arrival airports. The whole flight is treated as if it took place at that latitude, because exposure increases towards the poles.

Dose table

The calculation is based on a reference table that gives the number of flight hours needed to accumulate 1 mSv at each altitude, at 60° latitude and at the equator.

The flight level is always rounded up to the next row in the table. For example, FL320 uses the FL330 row and FL410 uses the FL420 row. Flights above FL450 use the FL480 row.

Calculation step by step

Step 1: Select the table row. Round the flight level up to the next row and read H60 and Heq.

Step 2: Adjust for latitude. Interpolate linearly between the equator and 60°:

H(lat) = Heq + (lat ÷ 60) × (H60 − Heq)

Above 60°, the same trend is extended, which gives a higher (more conservative) dose.

Step 3: Convert to a dose rate.

Dose rate (µSv/h) = 1000 ÷ H(lat)

Step 4: Account for climb and descent. FL3XX assumes 12 minutes of climb and 12 minutes of descent, at half the cruise dose rate. The rest of the flight is at cruise level. This is the same as calculating the full cruise rate over the flight time minus 12 minutes:

Dose (µSv) = Dose rate × (T − 12) ÷ 60

For flights shorter than 24 minutes, climb and descent are each taken as half the flight time, with no cruise.

The report shows climb, cruise and descent minutes and the route dose for each flight, plus totals for the selected period.

Worked example

A flight from London (EGLL, 51.5°N) to Madrid (LEMD, 40.5°N) at FL410, with 2 h 05 min (125 min) between actual take-off and landing.

1. Row: FL410 rounds up to FL420, so H60 = 160 and Heq = 420.
2. Latitude: the higher latitude is 51.5°. H(51.5) = 420 + (51.5 ÷ 60) × (160 − 420) = 196.8 hours per mSv.
3. Dose rate: 1000 ÷ 196.8 = 5.08 µSv/h.
4. Dose: 5.08 × (125 − 12) ÷ 60 = 9.57 µSv.

The report shows climb 12 min, cruise 101 min, descent 12 min and a route dose of 9.568 µSv.

Limitations

Because this is a simplified model, it does not take into account:

• The actual route flown, or latitudes between departure and arrival
• Solar activity (the solar cycle) or changing geomagnetic conditions
• The actual climb and descent profile, or changes of cruise level

Related articles

• ACD integration for cosmic radiation dosimetry