Alternate Minima/Contact Approach Questions

[Condorito]

Hey guys/girls, I have 3 questions (studying for the IR Exam)

1)When you are selecting Alternate Minima, let's say that an airport has only one published NON-PRECISION APPROACH to Runway 36 for example:

Then you do the 800-2 or 300-1 above the lowest usable HAT/HAA, whichever is greater.

My question is, if the wind is strong from the south (which means you would have to circle to land on 18) do you use the Circling HAA for the calculation or you simply cannot use that airport?

2) When the BECOMING portion of the TAF is forecast to improve, you are supposed to use the end of the becoming period and when the BECOMING portion of the forecast is forecast to deteriorate, you need to use the start of it. Does that mean that I can only apply this forecast condition if the beginning or end of that BECOMING PERIOD happens to be my ETA?

Let say my ETA to the alternate was 2000Z and the TAF said BECMG 1822 (improving weather), is this only valid at 2200Z because that is the end of the BECOMING PERIOD? What if the weather was deteriorating, how would that change?

3) I've been reading on some books that for a Contact Approach, there must be a reported 1 SM Ground Visibility. The AIM doesn't mention this. Just mentions the 1 NM FLIGHT VISIBILITY. Was this an old requirement or did they just leave that out?

Thanks in advance for the help, hope I'm not confusing anyone!

[BTD]

I'm on the iPad so cut and paste is a bit of a pain.

1. The lowest useable hat for the runway to be used. You can take credit for the circling minima if you apply the 300-1. Some airports may only have a vor A or something. You can still use them and all approaches there will be circling.

2. In your case of becoming 18-22. If weather is improving and you need that improvement for a legal alternate then you have to wait until 22. If it is deteriorating then you need to consider it no good at 1800. Think of the most conservative approach.

3. It should be just the flight visibility. Some study books are not always correct. The cars, cap gen, and aim are the best study material.

Bad

[Condorito]

Thank you!

[triplese7en]

My question is, if the wind is strong from the south (which means you would have to circle to land on 18) do you use the Circling HAA for the calculation or you simply cannot use that airport?

Alternate minima deals with "useable" approaches. The approach isn't useable as a straight in if you have to circle. You must use the circling HAA for the calculation. This is also hinted at when it says "above HAT/HAA" as HAA is only associated with circling approaches.

Let say my ETA to the alternate was 2000Z and the TAF said BECMG 1822 (improving weather), is this only valid at 2200Z because that is the end of the BECOMING PERIOD?

Yes. It's only valid at 2200Z and that's 2 hours after your ETA so you can't use it. If it was deteriorating weather then it would be considered valid at 1800z and you would have to consider it for your alternate weather minima.

I've been reading on some books that for a Contact Approach, there must be a reported 1 SM Ground Visibility. The AIM doesn't mention this. Just mentions the 1 NM FLIGHT VISIBILITY. Was this an old requirement or did they just leave that out?

There is no requirement for ground visibility for a contact approach. It is only 1NM flight visibility.

[acheo]

Hi,

I was visiting this webpage and read this: Credit for improving weather in a TEMPO can not be taken....Like a TEMPO, credit for improving weather in a PROB can not be taken.

url: http://www.tompaul.ca/understand-becmg- ... lternates/

Is this a new rule or what? CARs don't say much about improving weather and I don't recall having seen this in the GEN CAP neither.
CARs refs:
ref: http://www.tc.gc.ca/eng/civilaviation/p ... n4-819.htm

On one other website I have found this which is in line with what I have always used:
http://www.langleyflyingschool.com/Page ... neral.html

cheers

[kev994]

On one other website I have found this which is in line with what I have always used:
http://www.langleyflyingschool.com/Page ... neral.html

cheers

Basically with a tempo you have to go with the most conservative. That website you are using is waaay out of date, it says you can't use GPS only alternates... that changed years ago.

[acheo]

Do you have a refs in the CARs?

[kev994]

I see what you are getting at, CAP GEN doesn't specify. My best explanation is that a TEMPO does not alter the prevailing forecast; from NOAA:
The TEMPO group is used for any conditions in wind, visibility, weather, or sky condition which are expected to last for generally less than an hour at a time (occasional), and are expected to occur during less than half the time period. The TEMPO indicator is followed by a four-digit group giving the beginning hour and ending hour of the time period during which the temporary conditions are expected. Only the changing forecast meteorological conditions are included in TEMPO groups. The omitted conditions are carried over from the previous time group.

[acheo]

It does alter the prevailing forecast for determining alternate minima. Otherwise, none of us in the industry are doing the right things when times comes to pick an alternate.

Now, for the job I'm was being tasked with I need to know down to the regulation what is the proper way to determine an alternate with improving weather within a TEMPO or PROB? The following references do mention something about deteriorating weather but nothing about improving weather: http://www.tc.gc.ca/eng/civilaviation/p ... n4-819.htm

I did not want to wait until Monday to call TC as it will take weeks before I can get a proper answer.

acheo

[AOW]

What matters first is the prevailing wx. If it is forecast to be 200/1/4 with a tempo of skc, you have to assume that it's going to be 200&1/4 at any time that you might need it. So the opposite: a prevailing forecast of skc, with a tempo of 0/0 you have to assume the worst case scenario... When you need to shoot that approach, it's going to be "in the weeds". The nice thing with prob30 and prob40 is that all you have to meet are approach minima. So if your prevailing forecast is 600/2, with a prob40 that covers your ETA of 200/.5, as long as you've got a useable ILS with mins of 200/.5 you're golden. In the same scenario, but with a tempo 200/.5 instead of prob40, it wouldn't be useable, since you would need alternate minima (600/2 or 400/1) or sliding scale...

[triplese7en]

I'm not sure why everyone is making this so complicated.

TC CAR 602.123 states: "No pilot-in-command of an aircraft shall include an alternate aerodrome in an IFR flight plan or IFR flight itinerary unless available weather information indicates that the ceiling and visibility at the alternate aerodrome will, at the expected time of arrival, be at or above the alternate aerodrome weather minima specified in the Canada Air Pilot."

The key word has been bolded.

TEMPO conditions are defined by the TC AIM as: "“TEMPO” is only used when the modified forecast condition is expected to last less than one hour in each instance, and if expected to recur, the total period of the modified condition will not cover more than half of the total forecast period."

So TEMPO is a forecast condition that, according to the "available weather information" (referenced by CAR 602.123), will happen during the times indicated in the TAF.

And if that wasn't clear enough for you, the CAP specifically says, "the forecast TEMPO condition shall not be below the published alternate minima requirements for that aerodrome".

If you understand what TEMPO conditions are and you can read the CAP, there really is no discussion about it.

[spaner]

This interests me,

On the field Goffer inspection, but it IS a necessary consideration, BEFORE you GO...
You're getting some really good info here and, YES, you DO need to know/understand all of this.
BUT, you've taken "your-eye-off-the-ball", as I like to say.
The goffer in the hole, on the field, although interesting, holds NO real weight, for the hop.

The real question IS, "Do you want to GO, or NOT? The information matrix, or justification, can be used to support both the GO/NO-GO argument; when "splitting hairs", such as this. Understanding this, you make your decision, to GO, or NOT.
The paperwork "click" is only required "TO-FILE", then, you reference your personal "comfort level".

#1, Can you get to a back-up aerodrome with the fuel onboard? (including your 45 minutes?) [SKC]
#2, Are you comfortable with the situation?

Then, change the ETA to fit the requirement dictated by the regs and the information matrix as it stands. Now, you ARE legal. Now you CAN go. Now you CAN do whatever you want; including going in the opposite direction to the SKC aerodrome, and using your 45 minutes to get there.

Which, if your "comfort level" IS "in-tune", it all works out and you never have to use it; but it is there to be used. (plan-B)

You make the decision, you are legal, and it works.

The rest is BS, and designed to confuse the laymen in the pursuit to "get-the-job-done".



OR maybe, you just want to take the night off...

[triplese7en]

#1, Can you get to a back-up aerodrome with the fuel onboard? (including your 45 minutes?) [SKC]

I want to add something to this.

You should always make sure you have enough fuel to make it to a back-up aerodrome, even VMC/VFR. I had a training captain tell me of an experience where he flew to an airport at night and couldn't land because the runway lights weren't working. He told me he couldn't land even if he wanted to as it was completely pitch black with no lights and no moon. Luckily he did have fuel to get to another airport.

Legal doesn't always mean safe. Sometimes you have to go above the legal requirements. That's where airmanship and pilot decision making come in.

[Tip of the Arrow]

I'm not sure why everyone is making this so complicated.

TC CAR 602.123 states: "No pilot-in-command of an aircraft shall include an alternate aerodrome in an IFR flight plan or IFR flight itinerary unless available weather information indicates that the ceiling and visibility at the alternate aerodrome will, at the expected time of arrival, be at or above the alternate aerodrome weather minima specified in the Canada Air Pilot."

The key word has been bolded.

TEMPO conditions are defined by the TC AIM as: "“TEMPO” is only used when the modified forecast condition is expected to last less than one hour in each instance, and if expected to recur, the total period of the modified condition will not cover more than half of the total forecast period."

So TEMPO is a forecast condition that, according to the "available weather information" (referenced by CAR 602.123), will happen during the times indicated in the TAF.

And if that wasn't clear enough for you, the CAP specifically says, "the forecast TEMPO condition shall not be below the published alternate minima requirements for that aerodrome".

If you understand what TEMPO conditions are and you can read the CAP, there really is no discussion about it.

Since it's so clearly quoted above:
Here's an eg. - CYWG 150618Z 18010KT 1SM BR VV001 TEMPO 0812Z P6SM OVC010.
If required you would land at your ILS alternate at 10Z. Using you're logic above it would appear this is a good alternate, no?

[triplese7en]

Haha nope. Where did I say that you only need to look at TEMPO to determine the minima? The CAR and CAP that I mentioned clearly states what is required.

Where would you get the idea that the main forecast conditions could be ignored when determining what weather would be present at a particular time?!

[Tip of the Arrow]

I'm simply quoting your condescending post. You're saying TEMPO will happen. So VFR will happen at your alternate at the appropriate time.
I know that this doesn't work for an alternate but your quotes leave incomplete information which appears to support the idea that it could if the TEMPO was for improving conditions rather than deteriorating conditions.
So it's all good.

Cheers.

[triplese7en]

You're saying TEMPO will happen. So VFR will happen at your alternate at the appropriate time.

That's not what I'm saying.

CYWG 150618Z 18010KT 1SM BR VV001 TEMPO 0812Z P6SM OVC010

Let's say the alternate ETA is 10z. If I asked what the available weather information said for 10z, what would you tell me? You should say that the weather is forecast to be 1SM in BR with a ceiling of 100', and a TEMPO of P6SM and a ceiling of 1000'. That is what the forecast weather is at the alternate ETA.

your quotes leave incomplete information

My quote was specifically about TEMPO conditions and alternate minima—I didn't feel like regurgitating exactly what the CAP GEN says.

TEMPO was for improving conditions rather than deteriorating conditions.

This is probably exactly what is screwing people up with this. TEMPO doesn't involve different rules for improving versus deteriorating conditions. TEMPO must be considered regardless of what the TEMPO conditions are.

It is BECMG that has different rules for improving versus deteriorating. Discussing TEMPO in terms of how the conditions are changing is pointless and adds to confusion.