IFR Question: Alternate Weather Minima

[gnieto]

Hello Captains, I'm omy way to write the INRAT exam, and I cam up with one question, and I'm not being able to find the answer.

This is the question:

"The latest weather at Baker Lake is below landing minima and Rankin Inlet is reporting 1SM -RA SCT002 OVC005.Can Rankin Ilet still be used as legal alternate?" Rankin Ilet is filed as alternate

A)No as this weather is below the Rankin Inket Akternate minima of 800-2
B) No as there is a cloud below the landing minimums at Rankin Inlet
C)Yes, The overcast layer is above landing minimums at Rankin Inket. the Akternate minima are for flight planning purposes only.
D) Yes, but you must find another alternate as the Rankin Inlet weather is below alternate minima.

Taking a look to the provided chart own the Aeorcourse manual for this section VOR/DME RWY 13 TRUE.The VOR/DME minima is a ceiling of 400ft ASL (312 AGL) and 1 SM visibility.

The weather requirement for a Non Precision Only Available is 800-2* or 300-1 above the lowest usable HAT and visibility, whichever is greater, In this specific case the standard minima of 800-2 is greater and applying the sliding scale we can have a minimum of 900-2 or 1000-1.

So, my answer was B ,but the correct answer according to the book is C

When does the landing minima supersedes the alternate minima? I very confused on this. Can I file an alternate even if the weather is lower than the Alternate weather minima, but is above the landing minimum for the approach? And then fly this approach? Why is the alternate minima only for flight planning procedures?

I hope someone can give me a nice explanation. Thanks for reading.

[looproll]

Well here's my explanation for what it's worth:

The key is in the statement "the Alternate minima are for flight planning purposes only". They are basically throwing landing minimum in there to confuse you. "C" is the best answer. Alternate minima are based on FORECAST conditions, not reported conditions, so with no other info, C is correct. The only time LANDING minimums come into play with regards to filing a legal alternate on a flight plan is when there is a PROB period that is below the alternate minima, but above LANDING minimums for a useable approach.

Filing an alternate happens in the flight planning process, when you are filing before a flight. So the rules say it's based on FORECAST conditions in a TAF or GFA, not reported conditions of a METAR. They want the weather to be decent at your alternate at the time you are expected to arrive there.

[costermonger]

The whole concept of the alternate minima process is to allow for some deterioration in the actual conditions and still allow you to land at the alternate, if needed. The 300-1 you add to the landing minima is a buffer; the forecast has to be better than the landing minima - in this case, standard non-precision alternate minima (800-2, 900-1 1/2, 1000-1). If that's what the forecast says for your ETA when you file, that's a legal alternate.

Once you're off the ground, if it gets a little worse - as it has in this scenario - then that's what the buffer was for. As long as it still meets the landing minima when you get there, you're still able to land.

[gnieto]

Thank you both aviators! Now i understand the concept and why is the alternate used in the flight planning stage

[rapid602]

It is used 1) because some idoits would actually take off and have nowhere to go if you let them.
2) If you have a com failure after take off and you are in IFR weather Air Traffic Control will know where you are going, and you know where you can go to get yourself and your aircraft and any passengers with you on the ground.

I think ???

[loopa]

The whole 800-2, 600-2 along with the sliding scales are for flight planning purposes. Once you're in the AIR you can legally fly where ever you want provided the weather is above landing minima and there are no conditions for an approach ban in effect. Obviously willful negligence is not legal under any circumstance.

Once you are in the AIR, there's absolutely nothing stopping you from going to an airport that is fogged in with no way to get in with exception to what? The approach bans (which also have a few exceptions to it).

Therefore the answer is C, even though the SCT002 is below the published AGL value of the landing minima (meaning you could still have obscurities to be able to safely conduct a visual transition from the approach to landing), it doesn't constitute a LAYER. OVC005 is your layer and therefore you are legal to conduct the approach and hence why it is a legal alternate.

Say the WX was however OVC002, now you are below landing minima and are therefore banned to conduct this approach (let alone fly to it as an alternate) as it would now be willful negligence.

Don't forget to review the hierarchy of visibility as well, as the same question could have a twist on it on the TC exam where they ask the same thing but with a vis that is below required fplanned alternate selection. Then what? Do you go off the advisory visibility on the CAP Chart or is there something else you have to take into account when considering an airport as an alternate that is below published advisory visibility. "Hint, read up on approach ban's and remember what the vis requirements are in order for an approach ban to be in effect. Are there any? Or are you simply restricted to ceiling?" Get comfortable with that stuff as I can almost promise you that you will have a play on words question like that on the exam. Mind you it's only a couple of marks...

For example:

You fly to CYVR, wx is reported below landing minima and you don't meet the requirements for a CAT2 approach. You are forced to divert to CYYJ, SPECI issued is OVC003 with 1/8SM vis with RVR A reported at 1400 feet. Say for this purpose CYYJ is equipped with ILS all around. Can you legally fly to CYYJ as your alternate, and if so, can you conduct the approach?

What if you were sitting on the ground in CYXE flight planning CYYJ as an alternate, and in the arrival time for CYYJ, the TAF showed OVC008 2 1/2SM. Can you file this as a legal alternate?

Now for operational purposes you are the captain of a mid sized corporate jet with an approach speed of 142kts at the time of landing. Will this alter your flight planned as well as in air alternate requirements for the ILS approach in use?

Long Story Short:

For F/planning purposes, use the 800-2, 600-2, 400-1 along with the appropriate sliding scales (don't forget that in the case of a PROB you use landing minima for f/planning purposes)

For diversions, you need wx that is above landing minima and above approach ban requirements.

Good Luck on the exam!

[sakism]

Say the WX was however OVC002, now you are below landing minima and are therefore banned to conduct this approach (let alone fly to it as an alternate) as it would now be willful negligence.

Huh?

Banned from conducting an approach because the ceiling is below minimum?

As for flying to it as an alternate, negligence (or lack thereof) would be determined by what other options (if any) were available. Of course, if a flight departs with no viable alternate then negligence is obvious, but once in the air (especially in the north) sometimes you do the best with what you have.

Also to be considered is the amount of fuel onboard. There is certainly nothing preventing you, for example, from flying to Baker Lake, diverting to Rankin and missing, flying to Whale Cove and missing, flying to Arviat and missing and flying to Churchill - if one has enough fuel to do so.

[loopa]

Well I failed... I should really stop posting when I'm on these cold lay overs, or just all together.

No you are correct sakism, you are not banned from doing the approach, it just would be a moot point for an approach that levels you off quite a bit higher. Like you said if you have enough fuel nothing technically stops you from being a yo-yo going missed every where. But if you fly there and then run out of fuel, now you're just willfully being negligent.

The approach ban has more so to do with your Hierarchy of reported vis/rvr, not landing minima as you pointed out.

Thanks for catching my error

[Big Pistons Forever]

WARNING: Thread creep alert !

I think it is also important to note that anyone flying IFR should plan on having up to 4 different alternate airports.

1) The legal alternate: That is the one that meets all the legal requirements

2) The commercial alternate: That is where you want to go if you miss at your planned destination because it is the cheapest and/or most convenient place to end up

3) The gold plated alternate: This is reserved for those really crap days with wide spread bad weather and a not particularly warm fuzzy feeling about the weather forecasts and is some place you are confident that you can squeeze into when the weather really craters.

4) The enroute emergency alternate. This is the place (usually the nearest airport to your present position) where you are going to go "if the bad thing happens". This will obviously not be pre-planned but is a natural extension of good situational awareness.

No 1 and 2 are often different and are where the real world renders the pedantry of those "gotcha" alternate questions so favoured by TC and the flight schools, irrelevant.

No 3 can only be developed from hard won experience and local knowledge. Crap weather that is forecasted to improve is a good example. Yes it becomes a legal alternate if the weather at the end of the becoming period is above alternate mins, but by what mechanism is the weather going to get better ? Poor vis due to fog is a good example where the "getting better" time seems to mostly generated by the computer random number generator and wishful thinking on the part of the forecaster. This is the time I like to talk to the FSS guys in person (Oh how I miss real weathermen at the old airport weather stations ) and get a feel for what is making the weather and then deciding how far I am going to trust the TAF.

Anyway all of the above is of no use passing the INRAT...but I gave you fair warning at the top of this post