c4aa4c14____Legal_Information_Institute_Flight_Profile_Distances_Meaning
[Distance] ALr [Unit] Feet [Meaning] 
Reference Takeoff Noise Path. The distance from station A to the reference helicopter position Lr.
14 CFR Part 36, Appendix H to Part 36 - Noise Requirements For Helicopters Under Subpart H | US Law | LII / Legal Information Institute
Meaning