IFR Alternate question

[neilharris360]

on the alternate chart it says

If there is one usable precision approach the weather requirements are 600 - 2 or 300 - 1 above the lowest usable HAT and visibility, whichever is greater.

Why are there two sets of numbers "600 - 2 or 300 - 1"

Thanks for the help


Heres a link to the AIM that shows the chart... its RAC 3.14.1
http://www.tc.gc.ca/CivilAviation/publi ... 0.htm#3-14

[meflypretty]

Add 300 and 1 to the lowest usable minimums. If it is greater than 600 and 2, you have to operate to the higher minima.

[Bushav8er]

Answer is right there -

above the lowest usable HAT and visibility, whichever is greater.

Add each as mentioned, use the greater. Sometimes the 300-1 adds up to more than the 600-2.

[turbo-prop]

Lets say for example you are going to an airport like Churchill I believe minimums are 250AGL and 1/2 mile if you addthe 300 and 1 to this approach you would have 550 AGL and 1 1/2mile vis but because 600agl and 2 miles is higher you have to use 600agl and 2 miles. Now if your minimums were 400 and 1 and 1/2 miles when you add 300 and 1 to it your mins are now 700 and 2 and 1/2 miles.

You always have to use the higher of the 2. One more example is mins of 200 and vis of 2 miles your new minimums would be 600 agl (cause if you add 300 to the 200 you get 500 so 600 is the higher) and your vis would be 3 miles ( cause if you add 2 miles and 1 mle you get 3) which is the higher one.

Hope that hleps.

[Beechball]

Turbo Props' explanation is most accurate. You wont encounter this in the big city but it's very prevalent in the Rockies and the Arctic mountainous regions where you commonly have 400, 500, & 600 foot minimums published.

[airdude]

Here's a good example for you:

Quesnel BC (CYQZ)
Non-Precision Only available so:
It should be 800 - 2 or 300-1 above lowest HAA/HAT
Lowest HAA is 1011-3 (don't forget we are talking about Height and not altitude, so use the (Number).

Which one will I choose (800-2 or 300-1)?

1011, 3 miles + 300, 1 mile = 1311', 4 miles

This minimum (1311-4) is higher than 800-2 so you have to use it for alternate planing purpose...

Hope this helps!

Airdude

[sakism]

1011, 3 miles + 300, 1 mile = 1311', 4 miles

This minimum (1311-4) is higher than 800-2 so you have to use it for alternate planing purpose...

Just note that you never need more than 3 miles visibility to use as an alternate.

[SAR_YQQ]

What if you are an E-cat aircraft?

[sakism]

Doesn't matter - CAP GEN states: Calculated visibilities shall not exceed 3 miles.

[AuxBatOn]

I think it's a trick question. CAT-E minima are only published in military pubs (GPH200). We do not use civilian stuff, in Canada and the States anyways. By our rules, we have to apply whatever visibility we get (if it's 4 NM, then so it is).

[Dagwood]

1011, 3 miles + 300, 1 mile = 1311', 4 miles

Calculated visibilities shall not exceed 3 miles.

Only Transport would tell you that 3 + 1 = 3.

btw, Sakism has it right.

[Big Pistons Forever]

Only Transport would tell you that 3 + 1 = 3.

Actually TC's official position is 3+1 = 3 except for the times 3+1= 4 , or some other value the Minister has deemed applicable, refer to the CARS for further details.

[GoinNowhereFast]

Also, 3+1 = 2 if authorized in your air operator's certificate and deemed does not consitute a significant aviation hazard.

[Ref Plus 10]

1011, 3 miles + 300, 1 mile = 1311', 4 miles

This minimum (1311-4) is higher than 800-2 so you have to use it for alternate planing purpose...

Just note that you never need more than 3 miles visibility to use as an alternate.

Also note that the altitude should be rounded according to the CAP GEN as well, so the above example would then be 1300-3, or if it was 1321, it would then be 1400-3

Ref