Non-Standard Takeoff Minimums

5 Answers

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   Jeff on Feb 12, 2013

   As I understand it, alternate takeoff minimums do not apply to part 91, period. That being said, I think it would be foolish to disregard them. As the saying goes, “if the Boeings ain’t going…”

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   Dave Sandidge on Feb 12, 2013

   Yes, I haven’t found anything other than 91.175 which pretty much says that part 91 operators can go no matter what as long as the airport (controlled) is officially open. Class G airports are another matter; you’re on your own anyway…. However, like you I, too, think it would be very unwise to launch in such low conditions – especially in a single engine or light twin aircraft. The question is: What’s the best way to instill in your instrument students – who may have a little more macho than you’re comfortable with – a healthy respect for those higher takeoff minimums?

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   Lee Mckay on Feb 13, 2013

   @Dave Sandidge
   What is the best way to instill…

   My instrument training focused more on emergencies than anything else. The flying and procedures were pretty easy for me. Anyways, what was taught to me, and what I will bring forward to my future students (when I get there) will be “what are you going to do if you take off below those higher standards and something crazy happens and you need to turn around. Are you going to be able descend below approach minimums?”

   That’s what I was taught, and that’s what I’ll teach. That saying about Boeing going is good, too. I like that. It doesn’t apply to me (helicopters) but it’ll make you second guess your go decision for sure…

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   Brian on Feb 13, 2013

   Regardless of the question I was taught similar to Lee. And I’ll teach the same:

   There is no sense in leaving the ground in our little puddle jumpers if an approach doesn’t exist that can get you back on the ground safely. You could argue a near by airport could suffice if you’re leaving an airport with no approach. I’d by that, but the point is if something goes wrong (engine failures aside) you can deal with it by safely returning to earth with little delay.

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   John D. Collins on Feb 13, 2013

   I personally prefer not to depart unless the weather is at or above the airport landing minimums for the reason stated by others, it gives me an option to return to the airport and execute an approach if something comes up. It won’t do me any good if I have an engine failure, other than there might be a short period where I will be visual prior to the forced landing. In most cases, this is well above the standard minimums for takeoff, even if they don’t apply to my single engine, part 91 flight. It is all a matter or risk tolerance.

   That having been said, I am willing to overfly extended areas of low IFR where the conditions would not permit an approach to nearby airports. I am more willing to do this after departure and established in cruise, as any condition that occurred immediately after departure, I could have returned to the departure airport. In some ways it is similar to overflying the Atlantic ocean to the Bahamas or Lake Michigan on the way to Oshkosh.

   Some pilots are willing to accept more risk and will depart when conditions are at or below the non part 91 minimums. For a single engine aircraft, the standard minimum is 1 mile visibility. At airports located in class G airspace (typically 700 AGL and below), conditions are VFR. Jeppesen provides guidance on its Airport page that specify the departure minimums and they will often include data for below minimum departures with a section called “Adequate Visibility Reference” which they defined as “Runway markings or runway lighting that provides the pilot with adequate visual reference to continuously identify the take-off surface and maintain directional control through out the take off run.” At my airport, KUZA it is 1/4 mile while the minimums are the standard 1 mile.

   Although I have practiced zero-zero takeoffs and find they can be used in a training environment, bullets would have to be being fired at me to use the technique in real life, and even in that case, taxiing down the runway, leaving the airplane, and slipping off into the fog might be a better solution.

   If one is not familiar with the airport, then a DP or ODP provide the pilot with “a way” to safely depart a runway and climb to a enroute altitude. Often, it is not the only way, but this takes local knowledge by the pilot to know what alternatives are safe. The standard climb requirements are a relatively anemic 200 feet per NM. Even a C172 can easily obtain 600 FPM at 80 Kts near sea level which is 450 ft/NM. If one flies out of an airport day in and day out, they may not even be aware of obstacles that penetrate the 200 foot/NM plane which result in a DP being published and climbing on course to 400 feet before turning on course is completely safe, for them. I would never want to try this without local knowledge, but my point is that not flying a DP can be completely safe. Also remember that DP and ODP are only published for airports with an approach, so the pilot departing at an airport that doesn’t have approaches has to work out an acceptable plan to keep them out of the rocks.

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