A 3.3% gradient is the nominal climb gradient required to keep you away from the minimal 1:40 (2.5%) Obstacle Obstruction Surface (OIS), even during a diverse departure, and is equal to 200’/NM [200’ / (6076’/NM) * 100% = 3.29%]. This is mentioned in Sec 5-2-5 of the AIM, in chapter 2 of the Instrument Procedures Handbook, and in the TERPS.
My question is where are you guys getting guys getting 1.6% from? I don’t even see it in FAR 23 or 25. Unless I missed something, these are the minimum requirements for twin engine airplanes:
FAR 23NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES
23.65; Normal climb: 8.3%
23.66; Takeoff climb, one engine inop: as spec’d by the manufacture
23.67; Final climb, one engine inop: 1.5%
FAR 25 TRANSPORT CATEGORY AIRPLANES
25.119; Normal climb: 8.3%
25.121.b; 2nd segment climb, one engine inop: 2.4%
25.121.c; 3rd segment climb, one engine inop: 1.2%
Would someone explain where does the 1.6% comes from? It would only equate to a 100’/NM gradient and certainly would not give any obstruction clearance. This is the first time I have heard of it and it doesn’t seem to make much sense.
Thanks,
VVJM265