A norma da Parte 121, que rege as decolagens de baixa visibilidade, está especificada em 14 CFR 121.651. Ele faz referência às empresas OpSpecs e 91.175 e Parte 97:
Mínimos de decolagem "padrão" são especificados em 14 CFR 91.175 e seriam os mais altos:
- Mínimos de descolagem não padrão especificados nas cartas do aeroporto (FAR 97)
- Para aeronaves, que não sejam helicópteros, com dois motores ou menos - 1 milha de visibilidade.
- Para aeronaves com mais de dois motores - 1⁄2 de visibilidade em milhas oficiais.
- Para helicópteros - visibilidade de 1 a 2 milhas por hora.
O OpSpec C056 é emitido para todas as 121 operadoras e, basicamente, explicita os mínimos de decolagem "padrão" listados acima e especifica que o RVR deve ser usado se estiver disponível na pista.
O OpSpec C078 é normalmente emitido e permite decolar com visibilidade abaixo do padrão, desde que o aeroporto ainda não tenha publicado acima do mínimo padrão de decolagem. Este é um OpSpec bastante envolvido com vários parágrafos opcionais, e os operadores podem ser aprovados para operações de decolagem até e incluindo 300 RVR. Para aqueles que não estão familiarizados com o termo, RVR (Runway Visual Range) é a distância que um piloto pode ver pela pista, medida por equipamento automático, e é medida em pés nos EUA.
Oferece aprovações para as seguintes visibilidades:
- 1/4 SM / RVR 1600:
- RVR da zona de aterrissagem (ou RVR médio se a zona de touchdown estiver inop) está controlando:
- Requer que "as marcações da pista ou a iluminação da pista forneçam aos pilotos uma referência visual adequada para identificar continuamente a superfície de decolagem e manter o controle direcional durante a decolagem". (Basicamente, desde que o piloto se sinta confortável, mas especificamente menciona o HIRL, CL e RCLM como bem).
- RVR 1000 (opcional)
- RVR da zona de aterrissagem e RVR de rollout (Um relatório de RVR médio pode ser substituído, se estiverem inoperantes, mas ainda assim devem ter dois sistemas) controlando
- Requer luzes da linha central da pista (CL)
- RVR 500 (opcional)
- RVR da zona de aterragem, RVR médio e RVR de lançamento estão todos a controlar (um pode ser inop)
- Requer luzes da linha central operativa da pista (CL)
- Requer marcações da linha central da pista (RCLM)
- RVR 300 (opcional)
- Requer um sistema de orientação de decolagem
- Requer luzes de pista de alta intensidade operativa (HIRL)
- Requer luzes centrais da pista operativa (CL)
- Requer marcações de linha de centro de pista reparáveis (RCLM)
- Orientação do curso frontal do localizador (se aplicável ao sistema usado)
- Crosswind menos de 10 nós
- RVR da zona de aterragem, RVR médio e RVR de lançamento estão todos a controlar (um pode ser inop)
- Requer requisitos de treinamento especiais para o PIC e o SIC
- Taxiways com iluminação de linha central operativa de taxiway devem estar disponíveis
Regulamentos / Amostra de OpSpecs
§121.651 Takeoff and landing weather minimums: IFR: All certificate holders.
(a) Notwithstanding any clearance from ATC, no pilot may begin a takeoff in an airplane under IFR when the weather conditions reported by the U.S. National Weather Service, a source approved by that Service, or a source approved by the Administrator, are less than those specified in—
(1) The certificate holder's operations specifications; or
(2) Parts 91 and 97 of this chapter, if the certificate holder's operations specifications do not specify takeoff minimums for the airport.
§91.175 Takeoff and landing under 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.
C056, IFR Takeoff Minimums, Part 121 Airplane Operations - All Airports.
a. Standard takeoff minimums are defined as 1 statute mile visibility or RVR 5000 for airplanes having 2 engines or less and ½ statute mile visibility or RVR 2400 for airplanes having more than 2 engines.
b. RVR reports, when available for a particular runway, shall be used for all takeoff operations on that runway. All takeoff operations, based on RVR, must use RVR reports from the locations along the runway specified in this paragraph.
c. When a takeoff minimum is not published, the certificate holder may use the applicable standard takeoff minimum and any lower than standard takeoff minimums authorized by these operations specifications. When standard takeoff minimums or greater are used, the Touchdown Zone RVR report, if available, is controlling.
d. When a published takeoff minimum is greater than the applicable standard takeoff minimum and an alternate procedure (such as a minimum climb gradient compatible with aircraft capabilities) is not prescribed, the certificate holder shall not use a takeoff minimum lower than the published minimum. The Touchdown Zone RVR report, if available, is controlling.
C078, IFR Lower Than Standard Takeoff Minimums, 14 CFR Part 121 Airplane Operations - All Airports.
Standard takeoff minimums are authorized in operations specification paragraph C056. The certificate holder is authorized to use lower than standard takeoff minimums in accordance with the limitations and provisions of this operations specification as follows.
a. Runway visual range (RVR) reports, when available for a particular runway, shall be used for all takeoff operations on that runway. All takeoff operations, based on RVR, must use RVR reports from the locations along the runway specified in this paragraph.
b. When takeoff minimums are equal to or less than the applicable standard takeoff minimum, the certificate holder is authorized to use the lower than standard takeoff minimums described below:
(1) Visibility or runway visual value (RVV) ¼ statute mile or touchdown zone RVR 1600, provided at least one of the following visual aids is available. The touchdown zone RVR report, if available, is controlling. The mid RVR report may be substituted for the touchdown zone RVR report if the touchdown zone RVR report is not available.
(a) Operative high intensity runway lights (HIRL).
(b) Operative runway centerline lights (CL).
(c) Serviceable runway centerline marking (RCLM).
(d) In circumstances when none of the above visual aids are available, visibility or RVV ¼ statute mile may still be used, provided other runway markings or runway lighting provide pilots with adequate visual reference to continuously identify the takeoff surface and maintain directional control throughout the takeoff run.
[NOTE: If an operator is not authorized RVR 1000 the POI will not select RVR 1000 in the OPSS. If the OPSS is not available the POI should delete subparagraph b(2), b(3), & b(4) from the word boilerplate.]
(2) Touchdown zone RVR 1000 (beginning of takeoff run) and rollout RVR 1000, provided all of the following visual aids and RVR equipment are available.
(a) Operative runway centerline lights (CL).
(b) Two operative RVR reporting systems serving the runway to be used, both of which are required and controlling. A mid-RVR report may be substituted for either a touchdown zone RVR report if a touchdown zone report is not available or a rollout RVR report if a rollout RVR report is not available.
[NOTE: If an operator is not authorized RVR 500 the POI will not select RVR 500 in the OPSS. If the OPSS is not available the POI should delete subparagraph b(3), & b(4) from the word boilerplate.]
(3) Touchdown zone RVR 500 (beginning of takeoff run), mid RVR 500, and rollout RVR 500, provided all of the following visual aids and RVR equipment are available.
(a) Operative runway centerline lights (CL).
(b) Runway centerline markings (RCLM).
(c) Operative touchdown zone and rollout RVR reporting systems serving the runway to be used, both of which are controlling, or three RVR reporting systems serving the runway to be used, all of which are controlling. However, if one of the three RVR reporting systems has failed, a takeoff is authorized, provided the remaining two RVR values are at or above the appropriate takeoff minimum as listed in this subparagraph.
(4) At foreign airports which have runway lighting systems equivalent to U.S. standards, takeoff is authorized with a reported touchdown zone RVR of 150 meters, mid RVR of 150 meters, and rollout RVR of 150 meters. At those airports where it has been determined that the runway lighting system is not equivalent to U.S. standards, the minimums in subparagraphs a(1) or (2), as appropriate, apply.
c. Takeoff Guidance System, If Applicable. If the certificate holder is authorized to use takeoff minimums based upon the use of takeoff guidance systems, the minimums will be specified for the aircraft listed in the Table 1 below. The certificate holder shall conduct no other takeoffs using these takeoff minimums. If subparagraph c is not authorized, N/A will be annotated in each of the columns in the table.
(1) Special provisions and limitations.
(a) Operative high intensity runway lights (HIRL).
(b) Operative runway centerline lights (CL).
(c) Serviceable runway centerline markings (RCLM).
(d) Front course guidance from the localizer must be available and used (if applicable to guidance systems used).
(e) The reported crosswind component shall not exceed 10 knots.
(f) Operative touchdown zone, and rollout RVR reporting systems serving the runway to be used, both of which are controlling, or three RVR reporting systems serving the runway to be used, all of which are controlling. However, if one of the three RVR reporting systems has failed, a takeoff is authorized, provided the remaining two RVR values are at or above the appropriate takeoff minimum as listed in this subparagraph.
(g) The pilot-in-command and the second-in-command have completed the certificate holders approved training program for these operations.
(h) All operations using these minimums shall be conducted to runways which provide direct access to taxi routings which are equipped with operative taxiway centerline lighting which meets U.S. or ICAO criteria for CAT III operations; or other taxiway guidance systems approved for these operations.
(2) The certificate holder is authorized to use the following takeoff minimums for the airplanes listed below.
Table 1 (N/A = Not Authorized) Airplane M/M/S Lowest Authorized RVR Required Takeoff Guidance System
[NOTE: If an operator is not authorized pilot assessment the POI will not select this statement in the OPSS. If the OPSS is not available the POI should delete subparagraph d in its entirety from the word boilerplate.]
d. Pilot Assessment of RVR for Takeoff (if applicable). In circumstances when the touchdown zone RVR reporting system has failed, is inaccurate, or is not available, the certificate holder is authorized to substitute pilot assessment of equivalent RVR for any touchdown zone RVR report required by this operations specification paragraph provided that:
(1) The pilot has completed the FAA-approved training program for visibility assessment in lieu of RVR, and
(2) Runway markings or runway lighting is available to provide adequate visual reference for the assessment.