“ATC climb of 310′ per NM to 4000ft” in takeoff minimums?

2 Answers

1. 
   

   
   

   jeff on Aug 04, 2017

   for departure procedures, the standard climb gradient of 200′ per NM is assummed unless specified otherwise, either on the departure procedure itself or in the AFD for the airport under the non standard take off minimum ( denoted by a T in a black triangle on the approach plate)

   In your example, the departure procedure is telling you, you must maintain a climb gradient of 310′ per NM all the way up to 4000′. Keep in mind, that you must be able to make this gradient if you take off and loss an engine. 310′ per nm translates into a climb gradient of 310/6000 = .526, which is 5.2%. If you want to extrapolate to vertical speed in fpm, just multiply by your ground speed. For example, at 200kts ground speed, a 5.2% gradient is 1040fpm.

   Thes non standard climb gradients are usually because of obstructions in the take off path. So failure to meet the climb requirements could be deadly, especially if you are IFR and in IMC where you cant steer around obstructions.

   Hooe this example help.

   Jeff

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2. 
   

   
   

   John D Collins on Aug 04, 2017

   The note ATC climb means that ATC has a need for you to be able to climb at 310 feet per NM until 4000 feet, obstacles or terrain require you to climb at 280 feet per NM to 2500. This means that you could conceivably negotiate a climb gradient with ATC below 310 feet per NM down to 280 feet per NM to 2500 feet and you will not hit something hard, but if you don’t get an ATC dispensation, you need to climb using the higher gradient to 4000 feet. ATC can’t waive the 280 feet per NM climb gradient, only a bulldozer can do that.

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