Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Destination Alternate weather mins

Tech Log The very best in practical technical discussion on the web

Destination Alternate weather mins


Old 16th Aug 2009, 10:37
  #1 (permalink)  
Thread Starter
Join Date: Aug 2004
Location: usa
Posts: 87
Destination Alternate weather mins


Trying to look for the exact rule (if any- FAA, JAR) regarding the destination alternate minimums once the flight has departed.Not the 1 Navaid/ 2 Navaid rule which applies for dispatching, but rather what happens when enroute the weather goes to actual landing minimums in the Alt airport.
Can still shoot an approach but below the alt. mins that existed during planning.Can I press on to my original destination leaving my alternate as is, or should I choose a different alternate?
Not considering ETOPS enroute alternates.

ranklein is offline  
Reply With Quote
Old 16th Aug 2009, 11:59
  #2 (permalink)  
Join Date: Oct 2004
Location: UK
Posts: 717
JAR ops 1

If you search the interwebthing for the above it will give you some info.

I know its now EA ops but the EA publications are near on impossible to find free of charge.

You can start an approach if your minimums are out of limits. If you do not have the minimums by reaching the outer marker/1000' or equivalent position, you must go around.

If you did have the minimums when starting the approach but went below the mimimums after passing the criteria stated above, you can still carry on to your MDA/DA.

In essence you have two trap doors.

I am not sure what your job is and what your responsibilities are so cannot answer your question about choosing the different alternate.

We would obviously take the whole weather picture into account (i.e widespread fog everywhere) and make an informer decision.

Hopefully though the above helps.
jamestkirk is offline  
Reply With Quote
Old 16th Aug 2009, 13:20
  #3 (permalink)  
Thread Starter
Join Date: Aug 2004
Location: usa
Posts: 87
Thanks jamestkirk ,

Getting down to a more detailed scenario:

Enroute to our destination, it's well above mins, another hour or two for arrival.The alternate weather gets to minimums.Can we still use it as an alternate or have to reissue a new one?
It's a matter of planning an alternate vs. using it as one while airborne (actual vs. planning).

ranklein is offline  
Reply With Quote
Old 16th Aug 2009, 15:19
  #4 (permalink)  
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,575
Whilst airbourne, the originally planned alternate can still be used, so long as it remains above your lowest landing minima, according to your ops specs...which vary by carrier.
However, it would be good practise to plan for another alternate, but you are not required to do so...whilst airbourne.
411A is offline  
Reply With Quote
Old 16th Aug 2009, 16:15
  #5 (permalink)  
Join Date: Jan 2008
Location: US
Posts: 251
Alternate minimums are planning minimums, used to determine fuel load for dispatch. Once en route you can plan to land at destination, filed alternate or any other suitable field, as long as the approach you intend to fly remains at or above published minimums. If the Wx at your filed alternate deteriorates below the planning minimums while en route there is no regulatory requirement to chose another alternate, though obviously it would make good sense to do so.

airbourne - is that a town in one of the shires?

Last edited by MU3001A; 17th Aug 2009 at 04:03.
MU3001A is offline  
Reply With Quote
Old 16th Aug 2009, 17:05
  #6 (permalink)  
Join Date: Oct 2006
Location: It wasn't me, I wasn't there, wrong country ;-)
Age: 73
Posts: 1,757
Min nbr of DEST alts

You should always plan a min of 2 DEST alts, with the furthest yr fuel alt. FPL should show yr fuel alt as #1, 2nd as #2 yr pref cmcl alt. Thus all bases are covered
merlinxx is offline  
Reply With Quote
Old 16th Aug 2009, 17:16
  #7 (permalink)  
Join Date: Aug 2008
Location: North America
Age: 58
Posts: 364
There are two different parts to your question. One has to do with the paperwork requirements between the PIC and the dispatcher assigned to the flight prior to commencing the flight. This part of the question ends when the aircraft gets airborne from the departure airport. The required weather minimums at the destination alternate are spelled out in the FARs and may be amended by your companies Operations Specifications. These are preflight dispatching requirements only. They will be affected by runway options, navaid availability, possibly MELs, aircraft and crew limitations and probably several other things I have not mentioned. The main point is that they apply before the aircraft takes off.

Once you take off now you are in a completely different realm. As long as you have approach minimums you can fly to your alternate and fly the published instrument approach. If the weather goes below approach minimums you can still declare an emergency and fly the approach down to 0-0 and land if you need to. As others have mentioned you should be paying attention to your destination and alternate weather trends and if they deteriorate prepare a different plan long before you get to the point of declaring an emergency and landing at 0-0.

Once airborne your published approach minimums amended by aircraft/flight crew specific limitations apply at both your destination and alternate(s). There are no separate “alternate weather requirements” you need to meet once you are in the air.

For example: two flights from the same company are departing airport A for airport B within 3 hours of each other, the planned alternate is listed as airport C. The required alternate weather minimums at airport C are 2 miles visibility and 600’ ceiling (for example)(has a 1/2 mile 200' ILS). At the time of departure for the first flight the forecasted weather at airport C is 3 miles visibility and 1,000’. The first flight is dispatched from airport A to airport B listing airport C as the alternate.

An hour and half later a new forecast comes out for airport C calling for ¾ mile visibility 400’ ceiling. The first flight is airborne the change has no effect. The first flight can plan on using airport C as its alternate as it was legal when they departed. The second flight from airport A to airport B (still in the flight planning phase) will have to come up with a different alternate prior to departure as airport C no longer meets the preflight alternate weather minimums requirement.


Northbeach is offline  
Reply With Quote
Old 16th Aug 2009, 17:41
  #8 (permalink)  
Join Date: Mar 2005
Location: Uh... Where was I?
Posts: 1,342

In EU OPS you can dispatch with no alternate, provided certain conditions prevail, such as VMC at destination, less than 6 hour flight, two runways with independent approach procedures... Most MOs make mandatory to name an alternate anyway, but some airlines make use of that rule and take off with no alternate fuel reserve.
Normally you will name one alternate, except if the destination airport is below minima or you don't have destination WX forecast for ETA +-1 hour. In these cases you have to name two alternates, and the alternate fuel reserve is the greater of both.
Microburst2002 is offline  
Reply With Quote
Old 16th Aug 2009, 22:12
  #9 (permalink)  
Join Date: Aug 2007
Location: N1035.5W06700.1
Posts: 66
Standard alternate minimums requirement is based on the forecast conditions +-1 hour of the ETA at the airport. Visibility at least 2 miles and ceiling 600' (For precision approach). Visibility at least 2 miles and 800' ceiling (For non-precision approach). However, every airport may differ from the standard requirements and you have to make sure before departure
ClimbSequence is offline  
Reply With Quote
Old 17th Aug 2009, 21:36
  #10 (permalink)  
Thread Starter
Join Date: Aug 2004
Location: usa
Posts: 87
Thanks guys!!

Great answers, helped a lot!

ranklein is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service