GFA tool for 1-2-3 rule and minimums at alternate

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Walboy

Pre-takeoff checklist
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Walboy
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Surprise! There is no regulation or publication that answers every question. In this situation use common sense and all of the information you can find, and apply it conservatively.

Bob
 
91.169 (a) requires than an alternate airport be filed unless excepted by paragraph (b)

The following in an excerpt of paragraph (b). Note that there is no specific weather report mentioned in the regulation, it merely uses the terminology "Appropriate weather reports or weather forecasts, or a combination of them, indicate the following". So when Area Forecasts were published, they would be appropriate and now that they have been replace by the GFA, it would be appropriate.

(b) Paragraph (a)(2) of this section does not apply if :
(1) Part 97 of this chapter prescribes a standard instrument approach procedure to, or a special instrument approach procedure has been issued by the Administrator to the operator for, the first airport of intended landing; and
(2) Appropriate weather reports or weather forecasts, or a combination of them, indicate the following:
(i) For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the estimated time of arrival, the ceiling will be at least 2,000 feet above the airport elevation and the visibility will be at least 3 statute miles.
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Generally, I'll just use the nearest TAFs and extrapolate from there.
 
When in doubt, file an alternate. What’s the harm?
 
Walboy said:
Thanks! Exactly what I was looking for. I should pay better attention to the wording in the FARs.
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Good luck. Lawyers write these things, and get paid bonus money for making a reg as unreadable and open to interpretation as possible.
 
scottd said:
Be very careful when it comes to an automated tool vs a forecast issued by a highly trained meteorologist. The FA had amendment criteria and the GFA does not. I can show you dozens of forecasts where the GFA was so far off it was worthless if not dangerous. No the FA wasn’t perfect but you had a forecaster keeping an eye on it to make adjustments as necessary. I do believe the NWS made a huge mistake by taking the human out of the loop. The regulations need to be followed, but look beyond the regulatory requirements to create a plan that is based on more than just the GFA. G-AIRMETs and CWAs are still issued by forecasters, so they tend to be much more consistent than the GFA.
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Really good info.

On the local level I am getting kinda tired of the Boulder NWS forecasters doing what I call “talking to themselves” in official forecast text though.

“I’ve looked at fifty gazillion models and models 2,7,8, and 10 say this, and models 1,4, and 6 say that and blah blah blah blah.”

I don’t want to see it. Pick a forecast and go with it. I already know computers suck compared to humans with experience. I see that every freaking day in IT when people let computers make decisions. I don’t need to hear about all your broken computer models. LOL.
 
denverpilot said:
Really good info.

On the local level I am getting kinda tired of the Boulder NWS forecasters doing what I call “talking to themselves” in official forecast text though.

“I’ve looked at fifty gazillion models and models 2,7,8, and 10 say this, and models 1,4, and 6 say that and blah blah blah blah.”

I don’t want to see it. Pick a forecast and go with it. I already know computers suck compared to humans with experience. I see that every freaking day in IT when people let computers make decisions. I don’t need to hear about all your broken computer models. LOL.
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Contrarian view: the fact that models disagree has a bearing on forecaster confidence. The main reason I read the discussions is not so much to understand the technical reasons for which forecast they went with, but to get an idea of their confidence level in that forecast. Was it a slam dunk, a judgment call based on preponderance of evidence, or a wild guess? How much stock I put in the forecast is highly dependent on the answer to that question.

Of course, regardless of their confidence level, ALWAYS leave yourself an out...
 
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