1. character: Aircraft type
A = Amphibian
G = Gyrocopter
H = Helicopter
L = Landplane
S = Seaplane
T = Tilt-wing aircraft
2. character: Number of engines
3. character: Engine type
E = Electric
J = Jet
P = Piston
T = Turboprop
4. character: Wake Turbulence Category (WTC)
H = Heavy: > 300.000 lb ( > 136 tons)
M = Medium: 15.500 − 300.000 lb (7 - 136 tons)
L = Light: < 15.500 lb ( < 7 tons)