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Descending through a thin icing layer



 
 
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  #1  
Old December 18th 03, 05:29 AM
Wyatt Emmerich
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Default Descending through a thin icing layer

Let's say you take off on a long cross country with no forecast of icing. By
the time you arrive at your destination, a 2,000-foot layer exist below you
with temps of 30 F. You are getting low on fuel. Is it legal to descend
through the thin layer even if you are in an airplane without known icing?


  #2  
Old December 18th 03, 05:38 AM
Steven P. McNicoll
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"Wyatt Emmerich" wrote in message
...

Let's say you take off on a long cross country with no forecast of icing.

By
the time you arrive at your destination, a 2,000-foot layer exist below

you
with temps of 30 F. You are getting low on fuel. Is it legal to descend
through the thin layer even if you are in an airplane without known icing?


Who knows? Better play it safe and run out of fuel above the clouds.


  #3  
Old December 18th 03, 12:56 PM
Bonanza Man
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icing is a safety issue....flying w/o fuel is also a safety issue.

if you know you're about to run out of fuel (you should have .5
hr reserve if you're a stickler), and if you attempt to fly w/o
knowing how far you'll have to go to get vfr descent...you're
taking a major chance.

also, going thru a cloud layer or rain is not automatic an
automatic fall to the ground like stone situation. in MOST cases
one gets into trouble because of flying quite a while in icing
conditions...ice layer builds up...drag increases...airspeed
decreases...and eventuall stalls.

in your scenario...if you've above the airport AND you're running
short on fuel...setting yourself on the downwind to the active and
descending should be ok. land w/o extending the flaps.

others might disagree...but my point is weighing the two situations -
icing when you're over the airfield w/ running out of fuel.

bman.

p.s. com'n lets build up this newsgroup!!!


"Wyatt Emmerich" wrote in message
...
Let's say you take off on a long cross country with no forecast of icing.

By
the time you arrive at your destination, a 2,000-foot layer exist below

you
with temps of 30 F. You are getting low on fuel. Is it legal to descend
through the thin layer even if you are in an airplane without known icing?




  #4  
Old December 18th 03, 01:28 PM
Matthew S. Whiting
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Wyatt Emmerich wrote:
Let's say you take off on a long cross country with no forecast of icing. By
the time you arrive at your destination, a 2,000-foot layer exist below you
with temps of 30 F. You are getting low on fuel. Is it legal to descend
through the thin layer even if you are in an airplane without known icing?


If there is no forecast for icing conditions, then it appears you are
legal according to the FAA. However, if you are low on fuel, then
declare and emergency and you shouldn't have a problem with legality at
that point ... assuming you really do have the grounds for the declaration.


Matt

  #5  
Old December 18th 03, 01:57 PM
Gary Drescher
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"Wyatt Emmerich" wrote in message
...
Let's say you take off on a long cross country with no forecast of icing.

By
the time you arrive at your destination, a 2,000-foot layer exist below

you
with temps of 30 F. You are getting low on fuel. Is it legal to descend
through the thin layer even if you are in an airplane without known icing?


If you have a safe alternative, then descent through known icing-conditions
would be illegal in that scenario. But if it's the only way you can land
without risking fuel exhaustion, then you use your emergency authority to
override the regulations.


  #6  
Old December 18th 03, 05:04 PM
SFM
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"Bonanza Man" wrote in message
...
icing is a safety issue....flying w/o fuel is also a safety issue.

if you know you're about to run out of fuel (you should have .5
hr reserve if you're a stickler),


You mean .75 hours unless you are a helicopter, I guess I am a stickler!

Sec. 91.167 - Fuel requirements for flight in IFR conditions.
(a) No person may operate a civil aircraft in IFR conditions unless it
carries enough fuel (considering weather reports and forecasts and weather
conditions) to --
(1) Complete the flight to the first airport of intended landing;
(2) Except as provided in paragraph (b) of this section, fly from that
airport to the alternate airport; and
(3) Fly after that for 45 minutes at normal cruising speed or, for
helicopters, fly after that for 30 minutes at normal cruising speed.


  #7  
Old December 18th 03, 05:20 PM
Michael
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"Wyatt Emmerich" wrote
Let's say you take off on a long cross country with no forecast of icing. By
the time you arrive at your destination, a 2,000-foot layer exist below you
with temps of 30 F. You are getting low on fuel. Is it legal to descend
through the thin layer even if you are in an airplane without known icing?


No, it's not legal.

However, since you are low on fuel and above an icing layer, you are
in an emergency situation. You can thus ignore the prohibition on
operating in known icing conditions (assuming your airplane has one)
and descend anyway, since that's what's required to meet the
emergency.

Your condition is EXACTLY the same as that of a VFR pilot who relied
on a forecast of clear skies over his destination, went over the top,
had the forecast go bust, and is now trapped above a solid layer. The
only difference is that he's more likely to come out of this unscathed
than you.

Michael
  #8  
Old December 18th 03, 05:28 PM
Michael 182
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Not sure I agree with this - assuming the 2000 foot layer is not too low
AGL, you can bomb down through it in a little over a minute. Although it is
possible to accumulate enough ice in a minute to affect flight, it is pretty
unlikely. The key is not to hang out in the ice. For example, if the ice is
at the same level as the IAF you may want to modify the approach and make it
significantly steeper or shallower, depending on the surrounding terrain and
altitudes. This happened to me in San Marcos once. I just got below the ice
and flew a low visual approach. ATC was very cooperative.

Michael


"Michael" wrote in message
om...
Your condition is EXACTLY the same as that of a VFR pilot who relied
on a forecast of clear skies over his destination, went over the top,
had the forecast go bust, and is now trapped above a solid layer. The
only difference is that he's more likely to come out of this unscathed
than you.

Michael



  #9  
Old December 18th 03, 06:10 PM
Roy Smith
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"Wyatt Emmerich" wrote:
Let's say you take off on a long cross country with no forecast of icing. By
the time you arrive at your destination, a 2,000-foot layer exist below you
with temps of 30 F. You are getting low on fuel. Is it legal to descend
through the thin layer even if you are in an airplane without known icing?


The basic thread of legality is that the FARs say you cannot do anything
with the POH says is prohibited, and modern POH's for planes which are
not approved for icing have a statement along the lines of "flight in
known icing conditions is not approved". There's nothing in there which
differentiates between conditions which were forecast to exist at the
time you did your pre-flight planning and conditions which unexpectedly
popped up during the flight.

That being said, section 91.3(b) allows you great leeway in dealing with
emergencies:

"In an in-flight emergency requiring immediate action, the pilot in
command may deviate from any rule of this part to the extent required to
meet that emergency."

Notice the "to the extent required", however. You can do anything you
HAVE to, not anything you WANT to.

So, is this an emergency? Yeah, stuck above a 2000 foot icing layer
while low on fuel in a no-ice airplane sounds like an emergency to me.
I assuse by "low on fuel" you mean you don't have enough to get to
someplace else.

If I was stuck in such a situation, I would declare an emergency to make
sure ATC knew my predicament. I would get them to solicit pireps from
people in the air right now to make sure I knew where the floor of the
clouds were. Then I would get a clearance to descend, pilots
discretion, to an altitude known to be below the clouds.

Then I would get down though the layer as fast as I possibly could.
Pitot heat on, carb heat on, enough engine power to keep the carb warm,
and push the nose down. In smooth air, I'd let the airspeed climb well
into the yellow arc. Gear down in a retract will help get you down
faster. You should be able to get 1500 fpm down with no trouble. It's
hard to imagine anything could happen to you in the time it takes to
puch through a 2000 foot layer at that descent rate.

A slip or steep turn will add drag too, but I'm not sure I'd advise
either of those in a high-speed IMC descent.

I'm sure some people will poo-poo the idea of declaring an emergency.
Well, there's two reasons for doing so. One is that it gets you the
legal authority to violate the POH. The other (more important in my
mind) is that it makes sure ATC knows what's up. If you were to just
say "request 4000", and ATC gave it to you, you would be in a pickle if
in the middle of your descent, the controller came back with, "ammend
altitude, maintain 6000 for now, I'll have lower for you in 5 miles".

But, the biggest piece of advice is to NOT get into such a situation to
begin with.

Make sure you've got enough fuel to get to an alternate, whether it's
legally required or not. And make it a real alternate, not a paper one.
An alternate 5 minutes away from your destination is a stupid alternate
because whatever weather is happening at one is likely to be happening
at the other at the same time.

Also, keep up with the weather during the flight. On a long X/C with
any significant weather at all, I'm talking to flight watch once an hour
to get weather updates. Getting a weather update is usually the first
item on my agenda once I'm settled into cruise. If the forecast goes
bad, the sooner you know about it, the sooner you can do something about
it.
  #10  
Old December 18th 03, 08:07 PM
Matthew S. Whiting
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Roy Smith wrote:
"Wyatt Emmerich" wrote:

Let's say you take off on a long cross country with no forecast of icing. By
the time you arrive at your destination, a 2,000-foot layer exist below you
with temps of 30 F. You are getting low on fuel. Is it legal to descend
through the thin layer even if you are in an airplane without known icing?



The basic thread of legality is that the FARs say you cannot do anything
with the POH says is prohibited, and modern POH's for planes which are
not approved for icing have a statement along the lines of "flight in
known icing conditions is not approved". There's nothing in there which
differentiates between conditions which were forecast to exist at the
time you did your pre-flight planning and conditions which unexpectedly
popped up during the flight.

That being said, section 91.3(b) allows you great leeway in dealing with
emergencies:

"In an in-flight emergency requiring immediate action, the pilot in
command may deviate from any rule of this part to the extent required to
meet that emergency."

Notice the "to the extent required", however. You can do anything you
HAVE to, not anything you WANT to.

So, is this an emergency? Yeah, stuck above a 2000 foot icing layer
while low on fuel in a no-ice airplane sounds like an emergency to me.
I assuse by "low on fuel" you mean you don't have enough to get to
someplace else.


Assuming that you got low on fuel through ATC delays, a fuel leak or
something else largely out of your control. To me, getting low on fuel
in deteriorating weather is preventable and doesn't thus constitute a
bona fide emergency. It constitutes stupidity. I wonder if the FAA
would really buy the emergency authorization argument for a pilot who
had flown past airports that had fuel. I have to admit, if I was the
FAA or an NTSB administrative judge, I don't think I'd buy it.


Matt

 




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