Part 91 Alternates Question

[Rabble]

Ok. Dumb question of the day.

So if we know we need 2000 and 3 from 1 hour before to 1 hour after the ETA otherwise we need an alternate.

We also know that we need 600/2 or 800/2 forecast at the filed alternate dependant upon the type of approach.

So what if the main body of the forecast meets those criteria, but there is a TEMPO or OCNL line which would indicate weather below those minima?

I/e The main body indiciates 5 miles and clear TEMPO 2 miles and 1500 over?

Do we need an alternate?

If so, What if the airport we select for an alternate reports 5 miles and clear in the main body but OCNL 500 over and 1 mile in rain. Can you still use it as a legal alternate?

Thanks

 

[unreal]

91.169(b)(2) doesn't make any distinction between the type of report, be it an OCNL or TEMPO. Following the letter of the law, yes, you would need an alternate in your first example. Using the same line of thinking in your second example, no, you couldn't legally use that alternate.

 

[AC560]

There is an article in AOPA this month about fuel reserves in relation to alternates as well which I haven't fully digested yet. There apparently was an interpretation made by counsel which defines the 45 min fuel reserves that it must be to original airport, 1 approach there, and then alternate and then 45 mins or something to that effect.

Not entirely relevant to the conversation but involves alternate requirements.

 

[Amish RakeFight]

If any part of the TAF indicates less than 1-2-3 for destination you need an alternate. Same goes for the alternate itself. If it's an acceptable alternate (meaning it indeed can be used as one), then you must compy with published alternate minimums. If there aren't any then go with 800/2 or 600/2. Weather at ETA for the alternate must be at least this, otherwise anything indicating the potential of less will necessitate a different alternate which complies.

 

[aviator1978]

Quick Place to find legal alternate?

Don't want to hijack, but I've been looking for a website that would list the legal alternates nearest your destination (and even better....the weather at those alternates). So far, I use duats and fltplan.com, but either of these requires that I do a few more clicks to find out the weather and if it is legal.

 

[Amish RakeFight]

There is an article in AOPA this month about fuel reserves in relation to alternates as well which I haven't fully digested yet. There apparently was an interpretation made by counsel which defines the 45 min fuel reserves that it must be to original airport, 1 approach there, and then alternate and then 45 mins or something to that effect.

Not entirely relevant to the conversation but involves alternate requirements.

Read it earlier today.

It basically does say that when determining fuel reserves, for an alternate one must plan for normal cruise to destination, one approach which includes the missed approach fuel burn, time to alternate, one approach at alternate and 45 minutes left after this based upon the normal cruise speed and configuration.