A definição de visibilidade mínima padrão para partida é encontrada em CFR §91.175 Decolagem e pouso sob IFR.
f) Civil airport takeoff minimums. This paragraph applies to persons operating an aircraft under part 121, 125, 129, or 135 of this chapter.
(1) Unless otherwise authorized by the FAA, no pilot may takeoff from a civil airport under IFR unless the weather conditions at time of takeoff are at or above the weather minimums for IFR takeoff prescribed for that airport under part 97 of this chapter.
(2) If takeoff weather minimums are not prescribed under part 97 of this chapter for a particular airport, the following weather minimums apply to takeoffs under IFR:
(i) For aircraft, other than helicopters, having two engines or less—1 statute mile visibility.
(ii) For aircraft having more than two engines— 1⁄2 statute mile visibility.
(iii) For helicopters— 1⁄2 statute mile visibility.
O AIM 5−2−8 confirma sua intuição sobre gradientes de subida.
b. What criteria is used to provide obstruction clearance during departure?
- Unless specified otherwise, required obstacle clearance for all departures, including diverse, is based on the pilot crossing the departure end of the runway at least 35 feet above the departure end of runway elevation, climbing to 400 feet above the departure end of runway elevation before making the initial turn, and maintaining a minimum climb gradient of 200 feet per nautical mile (FPNM), unless required to level off by a crossing restriction, until the minimum IFR altitude. A greater climb gradient may be specified in the DP to clear obstacles or to achieve an ATC crossing restriction.
Observe que os mínimos de visibilidade não se aplicam às aeronaves da Parte 91. Observe também que os mínimos padrões de decolagem não têm um teto mínimo, enquanto os procedimentos de saída publicados quase sempre têm um teto mínimo ou um gradiente de subida - e geralmente têm ambos.