121 Alternate Airport Minimums?
 

Hi. I'm studying about 121 alternate airport minimums : When an alternate needs to be filed and the minimums required for the alternate. This will be applied for a regional carrier (ie Eagle or Colgan).

From what I've found, if it is a domestic 121 flight, the standard 1,2,3 rule works to determine if an alternate is needed. Does this apply for regional airlines like Colgan or Eagle? I read some items about 1500 feet above circling mins.

And for the alternate, should the "Add 400 and 1 SM Vis if 1 Nav aid" or "Add 200 and 1/2 SM Vis if 2 Navs" be used?

Anyone have any real world experience?

Regional Airline Alternate Minimums?
 

Hi. I'm studying about 121 alternate airport minimums : When an alternate needs to be filed and the minimums required for the alternate. This will be applied for a regional carrier (ie Eagle or Colgan).

From what I've found, if it is a domestic 121 flight, the standard 1,2,3 rule works to determine if an alternate is needed. Does this apply for regional airlines like Colgan or Eagle? I read some items about 1500 feet above circling mins.

And for the alternate, should the "Add 400 and 1 SM Vis if 1 Nav aid" or "Add 200 and 1/2 SM Vis if 2 Navs" be used?

Anyone have any real world experience?

The 123 rule applies. After that it get's complicated because each carrier has different OPSPECS and may have modified rules from the plain-vanilla 121 rules.

Derived alternate mins are normally used, the rules are a little more complicated than just 400 and 1 or 200 and 1/2. You have to know what types of navaids are involved and whether or not they actually count as different navaids (the ILS 27 and the ILS 9 probably do not count as different navaids since they likely use the same transmitter).

Although 121 derived mins may be lower than published alternate mins on the 10-9, you cannot use an airport as a 121 alt if the the 10-9 says "N/A" for alt mins.

Yes.

You're thinking of derived minimums...just wait until you start looking at Exemption 3585; that's a whole 'nother ball of wax...

A lot of what you said is correct. The airlines I have been at do not use standard alternate minimums of 600/2 or 800/2. Instead, we use Derived Alternate Minimums.

Basically, if you have one straight-in instrument approach available at your alternate, you have to add 400/1 to the minimums on the approach.

If you have 2 different straight-in approaches, using 2 different navaids, to 2 different and suitable (consider wind, braking action, slope, length, etc) runways then you can take the approach with the higher min's and add 200 & ½ to those min's.

Derived alternate minimums are not used for driftdown alternates.

This is how it is spelled out in my company's Operations Specifications and other 121 companies may vary.

There are also exemptions to these rules, such as with exemption 3585 but I'm feeling too lazy to explain it right now.

I'm assuming you fly primarily part 91 at this time, forgive me if I'm wrong. 1,2,3 applies to every one;1500 and 2 has to do with 121 and 135. Here's what I will say to you, if I were interviewing you(IMO) I can't expect you to know anything more than the current rules for which you fly under. Its nice to know 1500 and 2 and 400 & 1 and 200 & 1/2 but if you can't apply them in practicality memorizing them is not going to help. Study your Current regs and skim over the 121 stuff if you so please. Know of the rules of 121 but don't try to interpret them thats what ground school instructors are for!

Study RVR and whats the purpous of RVR reporting and what it can do for you if you must study any 121.

Definitely agree with this. You have had no exposure to deriving alternate minimums so there would be no reason for you to know this in an interview. Plus, like I said, this is specific to an airline's Ops Specs. Chances are everybody does it the same way, but I can't guarantee that. Just know everything you can about the flying you've been doing if you're interviewing. Read the FAR's and AIM. Don't get all hung up on things you'll learn once you get into ground school and I wouldn't bring any 121 stuff up in an interview because if you do, you've opened up a line of questioning that could get you burned.

All three FOM's I've worked under used this method, also referred to as OP SPEC number C55. None of the FOM's mentioned (that I remember anyway) anything about using a circling minimum to get a derived alternate minimum.

Also, the books I've worked under classified Canada/Mexico as "foreign", but we're allowed to operate in there under domestic DX rules, or something like that.

As well as when the term "marginal weather" is thrown about. Two of said FOM's had one definition of "marginal weather", my current one is different.

It's always best that when you're DX'd under 3583, or simply have 2, 3, or 4 alternates to get out the FOM and go through it with a fine tooth comb to make sure DX didn't goof up. I've had it happen to where the second alternate would have been good, except a NOTAM dealing with an inop navaid made it not. The DX'er missed it when it was used. Not slamming a DX'er here, as they can easily get overloaded in this situation, as well as being charged with dealing with 50-60+ releases per hour.

[QUOTE=ismertr;763104]Hi. I'm studying about 121 alternate airport minimums : When an alternate needs to be filed and the minimums required for the alternate. This will be applied for a regional carrier (ie Eagle or Colgan).

From what I've found, if it is a domestic 121 flight, the standard 1,2,3 rule works to determine if an alternate is needed. Does this apply for regional airlines like Colgan or Eagle? I read some items about 1500 feet above circling mins.


If you are talking for an interview, know the 123 and 6/2 and 8/2 rules.

If you are talking about actual requirements, it depends on the opspecs and the regs.

Under my 121 rules, 123 applies to the need for an alternate.

Under my previous 135 jobs, it is more complicated:
One hour before or after...
1000 above the lowest straight in min or 2000 which ever is greater
AND one mile more than the lowest vis or two miles whichever is greater

Standard alternate requirements are 6/2 or 8/2

Derived alternate mins were:
135
One suitable nav aid:
400 above the lowest CIRCLING min (or if circling is not authorized, straight in) , AND add 1 mile to the HIGHEST vis not less than 2
two independent navaids to suitable runways:
200 above the lowest CIRCLING min (or or if circling is not authorized, straight in) and add 1/2 to the HIGHEST vis not less than 1

121 is the same as 135 EXCEPT the additions are to the STRAIGHT IN mins and STRAIGHT IN vis and the NOT LESS thans do not apply

IN general, 135 rules require an alternate about 200 and1/4 ABOVE when 121 requires it. And the alternate will most of the time be based on CIRCLING mins rather than straight in.

So, just like duty/rest rules, 135 is more restrictive.

funny how that is........


In any event, your company's opspecs will set your specific limits

[QUOTE=FlyJSH;763281]Why do you think it's funny?

Who has more money, NBAA or ATA?