Making the safe decision (AKA "I hate AIRMET ZULU")

"Gary Drescher" wrote in message
. ..
That's a handy web site. Here's a link to the cite's guides to the meaning

Er, site's, not cite's.

: : "MVFR means Minimum or Marginal Visual Flight Rules. MVFR criteria means
: a
: : ceiling between 1,000 and 3,000 feet and/or 3 to 5 miles visibility."
:
: : http://www.weather.gov/glossary/glossary.php?letter=m
:
: I stand corrected. The little blue dots on aviationweather.gov always
: seemed
: to go away at 1500'.

: That's a handy web site. Here's a link to the cite's guides to the meaning
: of its symbols and acronyms:
: http://aviationweather.gov/static/info/

As far as the regs go, is "MVFR" even defined? I kinda doubt it... it's
either below minimums (as prescribed by the overly complicated VFR cloud
clearance/visibility rules), or it's not.

In any event, except for mountainous terrain, I wouldn't think twice about
launching VFR into 2700 AGL.

-Cory


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

On 10/27/2005 13:55, wrote:

: : "MVFR means Minimum or Marginal Visual Flight Rules. MVFR criteria means
: a
: : ceiling between 1,000 and 3,000 feet and/or 3 to 5 miles visibility."
:
: : http://www.weather.gov/glossary/glossary.php?letter=m
:
: I stand corrected. The little blue dots on aviationweather.gov always
: seemed
: to go away at 1500'.

: That's a handy web site. Here's a link to the cite's guides to the meaning
: of its symbols and acronyms:
: http://aviationweather.gov/static/info/

As far as the regs go, is "MVFR" even defined? I kinda doubt it... it's
either below minimums (as prescribed by the overly complicated VFR cloud
clearance/visibility rules), or it's not.

Well, it's defined (at least) in the Handbook of Aeronautical Knowledge
(FAA-H-8083-25) and used throughout that document.

From page 10-15, in the section describing the Weather Depiction Chart:

"Areas of IFR conditions (ceilings less than 1,000 feet and
visibility less than 3 miles) are shown by a hatched area
outlined by a smooth line. MVFR regions (ceilings 1,000 to
3,000 feet, visibility 3 to 5 miles) are shown by a non-hatched
area outlined by a smooth line. Areas of VFR (no ceiling or
ceiling greater than 3,000 feet and visibility greater than
5 miles) are not outlined."

It is also defined in Aviation Weather Services, AC-00-45E:

IFR - Ceiling less than 1,000 feet and/or visibility less
than 3 miles; hatched area outlined by a smooth line.

MVFR (Marginal VFR) - Ceiling 1,000 to 3,000 feet inclusive
and/or visibility 3 to 5 miles inclusive; non-hatched area outlined
by a smooth line.

VFR - No ceiling or ceiling greater than 3,000 feet and visibility
greater than 5 miles; not outlined.




In any event, except for mountainous terrain, I wouldn't think twice about
launching VFR into 2700 AGL.

-Cory




--
Mark Hansen, PP-ASEL, Instrument Airplane
Sacramento, CA

wrote in message
...
: That's a handy web site. Here's a link to the site's guides to the
meaning
: of its symbols and acronyms:
: http://aviationweather.gov/static/info/

As far as the regs go, is "MVFR" even defined? I kinda doubt it... it's
either below minimums (as prescribed by the overly complicated VFR cloud
clearance/visibility rules), or it's not.

True, being MVFR has no particular regulatory significance. But neither do
most of the other terms and symbols that appear in the government's aviation
weather products. Still, they have explicit definitions that are useful to
be familiar with in order to correctly interpret the meteorological
information that's offered.

--Gary

wrote:

: Yes, I'd call that MVFR. I believe the cutoff for east/west altitude
: rules is 3000 AGL, but that wasn't my point. The point is that the
: original suggestion was illegal in most airspace.

I haven't re-read the entire situation, but a 2700' ceiling is not really
MVFR. There's 1200' before it's not "legal VFR" anymore. Flying anywhere east of the
Mississippi will pretty much put you at most 10 minutes from any airport you could
land at if things turn to crap in a hurry.

I believe it does fit the definition of MVFR, but it isn't worth it to
me to take the time to look up a reference to prove it to you. :-)
Again, my comment was about the suggestion to, as I recall anyway
without going back to the first post in this thread, fly at an altitude
that was only 200' below the clouds. 500' below is the minimum in
virtually all airspace. That was the legality I was talking about.


: I'd rather fly IFR at a safe altitude and get around the ice, than scud
: run in mountainous terrain just below the cloud bases and wonder when
: the mountains and the bases will become one.

IF there is IFR at a safe altitute without icing, I'll agree. For me,
freezing level below MEA is almost without exception a no-go if I cannot go VFR. If
SCT or BKN, or a very thin layer with well-known clear above (forecasts + pireps), may
go IFR to VFR-on-top. Dodging icing in layered and unknown density is *legally* not
an option in any non-deiced single, and *practically* REALLY not an option in my
little Cherokee.

I pretty much agree. I wouldn't have flown last Sunday without a pirep
from a recently departed flight that was flying almost the identical
route as I planned to fly. However, I will typically go up and take a
look if I have reasonable outs. I understand the recent interpretations
of "known" icing to mean "forecast" icing, but that is really BS in my
opinion. If you adhere to that in the strictest sense, then you are
virtually grounded in the northeast for a very large part of the year as
icing is forecast on every cloudy day from virtually the ground up.


My opinions on this may be jaded by the fact that if I'm going somewhere, I
tend to fly northwest towards Chicago out of southwest Virginia... immediately into
6000' MEAs over the mountains of west virginia. "Getting around" the relatively high
MEAs isn't really an option unless I'm willing to fly to PA first.

: I flew in an area of icing potential just last weekend and had little
: problem finding an ice-free altitude. I had to change altitude several
: times to stay between layers, but in weather like that, there is very
: little traffic below 10,000 feet, even in the northeast. I found new
: altitudes to take less than 30 seconds toget, and it took that long only
: because the controller volunteered to talk to a few other aircraft to
: find the most promising altitude for me. I've found the controllers to
: be extremely helpful on days like that. Just ask for their help BEFORE
: you get in trouble, don't do something stupid and then drop the problem
: in their lap.

If MEA is below the freezing level, I'll concur. In fact, I've stayed at
altitude going IMC overflying west virginia at 8-9000' at the freezing level to see if
I *would* pick up ice. When I did, I asked for lower, got it without delay, decended
a thousand or two and ice cleared up... no problem.


To each their own... I'm a lot more comfortable if I can see outside.

Me too. If the windows are too dirty to see through to at last the
wingtips, I won't fly! :-)


Matt

: I believe it does fit the definition of MVFR, but it isn't worth it to
: me to take the time to look up a reference to prove it to you. :-)

No problem. Plenty of other folks to look it up to correct me...

: Again, my comment was about the suggestion to, as I recall anyway
: without going back to the first post in this thread, fly at an altitude
: that was only 200' below the clouds. 500' below is the minimum in
: virtually all airspace. That was the legality I was talking about.

True. IIRC, where it gets sticky in a regulatory sense is 1200/700' AGL
uncontrolled airspace just about everywhere. Avoiding "controlled all the
way to the ground" areas like airports, scud-running at 1000' AGL with an 1100'
ceiling is still legal.

: : I'd rather fly IFR at a safe altitude and get around the ice, than scud
: : run in mountainous terrain just below the cloud bases and wonder when
: : the mountains and the bases will become one.
:
: IF there is IFR at a safe altitute without icing, I'll agree. For me,
: freezing level below MEA is almost without exception a no-go if I cannot go VFR. If
: SCT or BKN, or a very thin layer with well-known clear above (forecasts + pireps), may
: go IFR to VFR-on-top. Dodging icing in layered and unknown density is *legally* not
: an option in any non-deiced single, and *practically* REALLY not an option in my
: little Cherokee.

: I pretty much agree. I wouldn't have flown last Sunday without a pirep
: from a recently departed flight that was flying almost the identical
: route as I planned to fly. However, I will typically go up and take a
: look if I have reasonable outs.

I don't remember the particulars of what you said. Finding layers or clear
above? MEA above freezing level? I'm being lazy and not looking at the previous
posts too.

I understand the recent interpretations
: of "known" icing to mean "forecast" icing, but that is really BS in my
: opinion. If you adhere to that in the strictest sense, then you are
: virtually grounded in the northeast for a very large part of the year as
: icing is forecast on every cloudy day from virtually the ground up.

My take on it is that I fly for fun and transportation. I respect the laws of
people, but I will NOT try to violate the laws of physics. As far as legalities go,
what's safe isn't necessarily legal and what's legal isn't necessarily safe. If you
practice good judgement (i.e. you don't have an incident), the forecast vs. known
issue won't be a problem.

Actually, I believe that my '69 PA-28 is legal to fly in icing conditions
because it's old enough to have a POH that doesn't specifically forbid it. Of course
there's always the "careless and reckless" clause.

: If MEA is below the freezing level, I'll concur. In fact, I've stayed at
: altitude going IMC overflying west virginia at 8-9000' at the freezing level to see if
: I *would* pick up ice. When I did, I asked for lower, got it without delay, decended
: a thousand or two and ice cleared up... no problem.
:
:
: To each their own... I'm a lot more comfortable if I can see outside.

: Me too. If the windows are too dirty to see through to at last the
: wingtips, I won't fly! :-)

"Ba-dump bump... *ting* "

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************