There are typically no IFR takeoff minimums for Part 91 operators. For Part 121 and 135 operators (and sometimes for Part 91), visibility depends on the aircraft.
The standard takeoff minimum for twin-engine aircraft is 1 mile of visibility – the same as it is for single-engine aircraft too.
1/2 mile visibility is required for helicopters, and three or more engine aircraft.
While there might not be any legal IFR takeoff minimums for many people reading this article, far too many pilots have been involved in avoidable accidents because of this.
Don’t let this happen to you.
Knowing what judgment calls you should make to takeoff safely is a must.
Part 91 IFR Takeoff Minimums
A pilot flying under Part 91 does not have to legally adhere to any takeoff minimums, unless published takeoff minimums are assigned and accepted.
An example of this is if ATC issues a Standard Instrument Departure (SID) procedure. You can reference FAR 91.175 if the SID requires “standard” minimums otherwise follow what’s published on the procedure.
While it may be true that you are under no obligation to accept these minimums, you are obligated to decline departure if you are unable to meet the performance requirements. These minimums are found in the Takeoff Minimums and (Obstacle) Departure Procedures
As being assigned and accepting published takeoff minimums are the exception rather than the rule, it is a very good idea to set your own personal minimums.
A good rule of thumb is that for every 60 knots you are flying, you want 1 mile of visibility. Circling minimums is another good idea to be on the safe side.
Also, ask yourself if you really need to go? The smartest and safest choice is sometimes to not takeoff at all. You don’t have to search for long to find many instances of tragic accidents involving pilots who were determined to takeoff with little or no visibility.
Part 121 and Part 135 IFR Takeoff Minimums
Part 121 and Part 135 operators must comply with the standard takeoff minimums as mentioned at the start.
So, that’s 1-mile visibility for single and twin-engine aircraft; and 1/2 mile visibility for three or more engine aircraft.
However, lower takeoff minimums can be used if published in the Operating Specifications (OpSpecs). Authorization for lower takeoff minimums can be found in OpSpec C078 for Part 121, and OpSpec C079 for Part 135.
Alternate IFR Takeoff Minimums
There is no requirement for aircraft operating under Part 91 to have a takeoff alternate.
But having a takeoff alternate that has better weather that you can safely reach in the event of an emergency would always be a wise thing to do.
Part 121 and Part 135 operators must follow alternate minimums, which can be found in FAR 125.217. The relevant text is as follows:
“No person may takeoff an aircraft under IFR from an airport where weather conditions are at or above takeoff minimums but are below authorized IFR landing minimums unless there is an alternate airport within 1 hour’s flying time.”