speed letter

supersonic speed (exceeds speed of sound / Mach 1)

variable-speed with speed control

instantaneous vertical speed indicator / instantaneous vertical-speed indicator (IVSI)

Nr gauge (Nr = speed of rotation) / rotor speed sensor

Motor PWM speed separated from PID speed

dead letter-box

letter bomb (parcel bomb, mail bomb, postal bomb etc)

letter of instruction

letter order

letter of agreement

letter of commendation

action letter

immediate action letter

call letter

recruitment letter

command letter

circumstantial letter

commendatory letter

Mike (letter M in the phonetic alphabet)

Air Force letter

personnel news letter

letter of censure

apparent speed

average speed

blade speed

convoy speed

critical speed

cross-country speed

endurance speed

exhaust speed

full speed (naut.)

gear speed decreaser