Takeoff weather requirements

[MooseTrax]

FAR part 91.175 says wx mins for takeoff need to be 1sm vis for two engines or less. This just doesn't make sense since they can land at 1/2sm vis on a Cat I ILS. Basically you could have a situation where all the jets could get in, but none get out? In the military, the standard for big airplanes is 1600 RVR. For some of the smaller jets it approach mins. It seems like I have been on airplanes taking off in less than a mile vis while traveling commercial before. I am specifically looking for how part 121 operators use this. Part 121 tyalks about a departure alternate, but it makes no reference to minimum weather required.

 

[Wiggums]

Quick Answer

Basically, for Part 91 operations no takeoff minima apply. For part 121 operations you need to check the airport diagram for the airport you are departing from. If there are no minimums published there then you go to the 1 mile or 1/2 mile perscribed in 91.175.

 

[The FNG]

I concur, 91.175 states the standard TO mins.

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(f) Civil airport takeoff minimums. Unless otherwise authorized by the Administrator, no pilot operating an aircraft under [parts 121, 125, 129, or 135 of this chapter] may take off from a civil airport under IFR unless weather conditions are at or above the weather minimum for IFR takeoff
prescribed for that airport under part 97 of this chapter. If takeoff minimums are not prescribed under part 97 of this chapter for a particular airport, the following minimums apply to takeoffs under IFR for aircraft operating under those parts:
(1) For aircraft, other than helicopters, having two engines or less--1 statute mile visibility.
(2) For aircraft having more than two engines-- ½ statute mile visibility.
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Alternate TO mins are on the back of Jepp chart 10-9 or 11-1 and can also be company specific (ie., CYYZ). Alternate TO mins can be as low as 500RVR but a company limit could apply (such as mine at 600RVR).

121.617 basically states alternate WX must meet the requirements of the OPSPECS. That's where you get into the 1 navaid/2 navaid rule. 1 navaid add 400/1, 2 navaids add 200/ 1/2. Check out Jepps introduction pages 127-130 for details.

Furthermore if WX is less than landing mins a TO alternate must be listed.

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Sec. 121.617

Alternate airport for departure.

(a) If the weather conditions at the airport of takeoff are below the landing minimums in the certificate holder's operations specifications for that airport, no person may dispatch or release an aircraft from that airport unless the dispatch or flight release specifies an alternate airport located within the following distances from the airport of takeoff:
(1) Aircraft having two engines. Not more than one hour from the departure airport at normal cruising speed in still air with one engine inoperative.
(2) Aircraft having three or more engines. Not more than two hours from the departure airport at normal cruising speed in still air with one engine inoperative.
(b) For the purpose of paragraph (a) of this section, the alternate airport weather conditions must meet the requirements of the certificate holder's operations specifications.
(c) No person may dispatch or release an aircraft from an airport unless he lists each required alternate airport in the dispatch or flight release.
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Also, the Army allows TO in 0/0 but I considered it insane without centerline lighting.

 

[bigsky]

121:651(a) (1)
basically reverts back to op specs of company.
These may change slightly depending on equipment such as cat 3 or use of H.U.D.
In general>>>
A) 1/4 mile or 1600 rvr (touchdown rvr contolling although if inop mid may substitute)need various ry markings or lighting or at least have adequate visual reference to maintain dir control throughout T.O. roll(paraprased)
B) 1000 touchdown and 1000 rollout RVR(mid could be a substitute.) Requires centerline lighting( This may be useful rather than example c which requires centerline markings in event of snow on RY!
C)500, 500 , 500 all 3 rvr required unless one inop again requires CL marking/lights

B/C will require T.O alternate within 1hr(2 hr-if 3 engine or more) of dept airport at normal cruise speed in still air with 1 engine inop