IFR Question ?

PA31 Driver · Post by **PA31 Driver** » Tue Feb 22, 2005 10:13 am

Ok here's the scenario....................

Altn. airport min............non-procession approach gives you ;

800-2 or 300-1

the H.A.T. is 358 feet and 1 1/4
you end up with ;

800-2 or 700 2 1/4

which one do you use ??

TopperHarley · Post by **TopperHarley** » Tue Feb 22, 2005 10:22 am

In the chart in RAC 3.14.1, it says " 800-2 or 300-1 above the lowest useable HAT and vizibility, whichever is greater."

In the above example, I'd say you use 800-2 1/4. In this case, however, 900-1.5 or 1000-1 also apply.

PA31 Driver · Post by **PA31 Driver** » Tue Feb 22, 2005 10:29 am

Ok C-HRIS

so your saying you use the higher of "BOTH" and because you used the 800' ceiling you can still slide it ?

pistonbroke · Post by **pistonbroke** » Tue Feb 22, 2005 10:30 am

You always use 800-2,unless the 300-1 above the lowest usable HAT is greater than 800-2. Always use the more restrictive.

KAG · Post by **KAG** » Tue Feb 22, 2005 10:44 am

Actually you can only slide "Standart Alt Min" meaning 600 -2 or 800-2. if your alt mins work out to be 800-2 1/4 you cannot slide it. It has to be exactly 600 - 2, or 800 - 2.

PA 31 driver, in your example your alt mins are 800' and 2 1/4 therefore you cannot slide it.
in figuring out ALT mins, think of the ceiling and vis as 2 sperate things that you have to calculate, taking the worst case of both.

Cheers.

Tango01 · Post by **Tango01** » Tue Feb 22, 2005 1:06 pm

If it's 2 1/4 you use 2. You can round off, but never exceed 3.

KAG · Post by **KAG** » Tue Feb 22, 2005 1:12 pm

tango, that was the old rules, you no longer round at all when it comes to VIS.

Beechball · Post by **Beechball** » Tue Feb 22, 2005 1:24 pm

I'm aware that you can't round down anymore and I don't. Ex: with the 300 & 1 scenario you end up with a vis of 2 1/4. It stays at 2 1/4, period. I have an old T/C Instrument Training Manual where it's clearly marked as to the old "round up" "round down" vis rule being applicable. Now, we can't do that anymore but can anybody post a concrete reference where it says that the "old" rule no longer applies, or the text that changed it or negated it.

rigpiggy · Post by **rigpiggy** » Tue Feb 22, 2005 4:22 pm

wrt the alternate minima the reson behind, 300-1 was for the rock's look at ylw or yxc. minimum's are 1700 or something like that . big difference from 800-2

paq · Post by **paq** » Tue Feb 22, 2005 5:37 pm

800 2 1/4 can't slide it!

PAQ

KAG · Post by **KAG** » Tue Feb 22, 2005 6:09 pm

S&J, your right because the TAF goesn't give 1/4 miles, but technically as per the letter of the law (which is a moot point in this case) you dont round up or down. So when asked during a ride I answer 2 1/4, in reality You have to look for the next whole mile up.

Cheers.

centerstored · Post by **centerstored** » Tue Feb 22, 2005 8:22 pm

KAG, close, but you would actually be able to use 2 1/2 sm. But you are correct in saying that you require 2 1/4 sm on your ride. TAF's report in 8ths below 1sm and 1/2's above 1sm to 3sm, and then whole numbers.

centerstored · Post by **centerstored** » Tue Feb 22, 2005 9:14 pm

Juice, see post above yours. 2.5, not 3.

KAG · Post by **KAG** » Tue Feb 22, 2005 10:05 pm

This is actually a really good review. as I dust off the old AIP....now if only it was up to date...

zaac · Post by **zaac** » Tue Feb 22, 2005 10:09 pm

It's online for you now KAG.

PA31 Driver · Post by **PA31 Driver** » Wed Feb 23, 2005 8:26 pm

i ask the local DFTE that question and I was told in my scenario you would use the 800-2.........use the higher ceiling.......

PA31 Driver · Post by **PA31 Driver** » Wed Feb 23, 2005 8:27 pm

Tango01 wrote:If it's 2 1/4 you use 2. You can round off, but never exceed 3.

the only reason you would never exceed 3, would be at 3 miles it would be VRF....

KAG · Post by **KAG** » Wed Feb 23, 2005 8:40 pm

If your refering to weather it's 2 1/4 or 2 , it's 2 1/4, you no longer round VIS.

Beechball · Post by **Beechball** » Thu Feb 24, 2005 7:40 am

I'm aware that you can't round down anymore and I don't. Ex: with the 300 & 1 scenario you end up with a vis of 2 1/4. It stays at 2 1/4, period. I have an old T/C Instrument Training Manual where it's clearly marked as to the old "round up" "round down" vis rule being applicable. Now, we can't do that anymore but can anybody post a concrete reference where it says that the "old" rule no longer applies, or the text that changed it or negated it.[/quote]

Did anybody come up with something in writing yet?

Whiskey Fox Charlie · Post by **Whiskey Fox Charlie** » Thu Feb 24, 2005 2:00 pm

King Air Guy, Beechball, et al:
Since when can you not round the visibilities? Where would I find hard evidence to support this? I've asked around at work and no one here knows anything about not rounding. The latest TC instrument procedures manual still says that 2 1/4 rounds down to 2.
Please help me here.

zaac · Post by **zaac** » Thu Feb 24, 2005 7:19 pm

Whiskey Fox Charlie wrote: The latest TC instrument procedures manual still says that 2 1/4 rounds down to 2.
Please help me here.

Read the copyright and warning in that book. It's not the IFR Bible.

The CAP GEN shows us how to round the HAT/HAA.

Why doesn't it show us how to round the vis too?

Take a look at this pulication from Nav Canada. It lists all the IFR alternate limits for ceiling and vis. There's no vis rounding.

Hope this helps.

http://www.msc-smc.ec.gc.ca/msb/manuals ... pp_c_e.pdf

Beechball · Post by **Beechball** » Thu Feb 24, 2005 8:58 pm

W.F.C. I'm asking for the same help! Urban ledgend in the East has it that you can no longer round down... The problem is... CAP GEN, and AIP etc have never been amended (on the vis issue only...)regarding this issue since before and after the round down changes.

It just doesn't seem to be on paper anywhere. Like TC has instituted a particular policy that varies from office to office. Where I am, we used to round up visibilities of lets say... 21/2 up to 3 and 21/4 down to 2. Now we don't do it anymore... The only answers I receive are " That's the way it is now..." HELLO???

Axial Flow · Post by **Axial Flow** » Thu Feb 24, 2005 9:18 pm

Capt S&J,

In regards to rounding it up to 3 miles because they do not issue TAF's with 1/4's after 1....Personally I just round up as it is a back up plan and the likely hood of it actually getting forecasted to be 2 1/4 miles is odd but I have seen it forecasted in Rankin during some semi blizzard conditions.

As per Environment Canada's MANAIR they forecast in 1/4's up to 2 1/2 miles....here is the reference.

Visibility values allowed are the followings:

0 to 3/4SM (in increments of 1/8 statute mile);
3/4SM to 21/2SM (in increments of ¼ statute mile);
3SM to 6SM (in increments of 1 statute mile); and
P6SM (for visibility greater than 6SM).
(Source Enviro Canada)
http://www.msc-smc.ec.gc.ca/msb/manuals ... p_2_e.html

Long story short I guess if you want to take the rules to the limit then 2 1/4 would be all right.

Cheers,
AF

zaac · Post by **zaac** » Thu Feb 24, 2005 9:56 pm

Beechball:

You have probably read this already but if you read CAR 602.123 it refers you to the Canada Air Pilot for alternate minimums. What this tells me is that the CAP GEN has the final say on this. Nowhere does it say in the CAP GEN you can round down the vis (at least I couldn't find it). So why do you think that you can? I don't care what the Instrument Procedures Manual says. It's outdated. I don't know if mine is the latest revision but its 1997. Fairly old.

I have my share of trouble finding what I want in the CARs to. Sometimes you have to read between the lines and find what is not written for your answers. If it wasn't like that they would probably be 5 times longer than they already are. I'm not sure if that would be better!

KAG · Post by **KAG** » Thu Feb 24, 2005 11:13 pm

Beachball, urban legend has it across canada. Im going with thte fact the the rounding of VIS is no longer found - anywhere, that it no longer applies.

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