Aviation law and authorities

Example 1 Checking three missions against the general conditions

Fah Sai Survey has three missions. All are commercial, so the 50 m separation applies. Write the check as a program so every mission is checked the same way (hypothetical mission data).

MAX_HEIGHT_M = 90          # Art. 5, MOT announcement B.E. 2558
AIRPORT_KM = 9
SEP_PEOPLE_M = 50          # registered operators: from uninvolved people, vehicles, buildings
INSURANCE_MIN = 1_000_000  # baht per occurrence

def check(m):
    issues = []
    if m["height_m"] > MAX_HEIGHT_M:
        issues.append(f"height {m['height_m']} m > {MAX_HEIGHT_M} m")
    if m["airport_km"] < AIRPORT_KM:
        issues.append(f"{m['airport_km']} km from airport < {AIRPORT_KM} km")
    if m["min_sep_m"] < SEP_PEOPLE_M:
        issues.append(f"separation {m['min_sep_m']} m < {SEP_PEOPLE_M} m")
    if not m["daylight"]:
        issues.append("not between sunrise and sunset")
    if not m["vlos"]:
        issues.append("beyond visual line of sight")
    if m["insurance_thb"] < INSURANCE_MIN:
        issues.append("insurance below 1,000,000 THB")
    return issues

missions = {
    "survey A": dict(height_m=80, airport_km=15, min_sep_m=60, daylight=True, vlos=True, insurance_thb=1_000_000),
    "survey B": dict(height_m=120, airport_km=7.5, min_sep_m=60, daylight=True, vlos=True, insurance_thb=2_000_000),
    "night C":  dict(height_m=60, airport_km=20, min_sep_m=40, daylight=False, vlos=True, insurance_thb=500_000),
}
for name, m in missions.items():
    issues = check(m)
    print(f"{name}: " + ("within general conditions" if not issues
                        else "needs specific permission or change -> " + "; ".join(issues)))

survey A: within general conditions
survey B: needs specific permission or change -> height 120 m > 90 m; 7.5 km from airport < 9 km
night C: needs specific permission or change -> separation 40 m < 50 m; not between sunrise and sunset; insurance below 1,000,000 THB

Mission A is within the general conditions. Mission B is too high and too close to an airport, so it must be replanned or specifically permitted. Mission C has three problems, including insurance below the minimum, which no permission can fix; the insurance must be completed first. The program ensures nothing is forgotten, but it does not replace reading the latest announcement, and some conditions, such as flying over a community, cannot be checked with numbers.

Example 2 Changing the antenna to fly farther

The team wants more range on its 2.4 GHz video link, so it tries a new antenna and an amplifier. The 100 mW limit in this example is an assumed value for practice; learners must check the real value in the current NBTC notice before use.

import math

limit_mw = 100.0        # assumed e.i.r.p. limit for practice; check the current NBTC notice
limit_dbm = 10 * math.log10(limit_mw)

setups = {              # (transmit power dBm, antenna gain dBi, cable loss dB)
    "stock antenna": (17.0, 2.0, 0.5),
    "8 dBi patch": (17.0, 8.0, 0.5),
    "patch + amplifier": (27.0, 8.0, 1.0),
}
print(f"limit {limit_mw:.0f} mW = {limit_dbm:.1f} dBm")
for name, (pt, g, loss) in setups.items():
    eirp = pt + g - loss
    mw = 10 ** (eirp / 10)
    verdict = "OK" if eirp <= limit_dbm else f"over by {eirp - limit_dbm:.1f} dB"
    print(f"{name:18s} EIRP {eirp:5.1f} dBm = {mw:6.0f} mW  {verdict}")

limit 100 mW = 20.0 dBm
stock antenna      EIRP  18.5 dBm =     71 mW  OK
8 dBi patch        EIRP  24.5 dBm =    282 mW  over by 4.5 dB
patch + amplifier  EIRP  34.0 dBm =   2512 mW  over by 14.0 dB

The 8 dBi patch antenna adds 6 dB, about four times the original EIRP, and adding the amplifier exceeds the limit by more than twenty times. The right way to fix link range is to place the ground station where it can see the drone, use a better receiving antenna on the ground side within what is permitted, or change the flight plan, not to raise transmit power beyond the rules.