VFR Flight into IMC

Weather

by

Dustin Harbage

Meteorologist

• USAF … 17 years– Weather Officer for A-37,

B-52, KC-135, KC-10, NORAD, US Space Command and SAC.

• National Weather Service– 21 years– Currently:

Senior Meteorologist for the NWS at Jackson, KY

Pilot

• ATP– 8000+ hours– 2000+ hr USAF H/C-

141– 2500+ hr and type

rating B-727– 1000+ hr MD-80 and

DC-9– 2000+ hr light twin

piston– 150+ hr light single

piston

What can happen to me if I’m flying VFR and enter IMC

Weather?

•Vertigo•Flight into terrain•Airborne collision

VFR Flight into IMC Weather

Why? Is it because…• We got to get there.• We believe it will get better.• We believe we can remain VFR and squeak

through.• We can still see the ground as we follow the

highway with a hand held GPS.

Seneca + handheld GPS

Freeway + IMC

Road curves

Mountain

2 Dead

=

Deadly Math

+

Why VFR into IMC• If we can see through the cloud is it IFR?• If we can climb or descend through the “sucker

hole” is it OK? • Does 1000 feet above, 500 feet below, and 2000

feet horizontal, apply to me?

Why VFR into IMC

• How can we tell that the inflight visibility is less than 3 miles?– Is this taught in pilot training?

• How do we measure 2,000 feet horizontal cloud clearance, or 500 feet below cloud clearance?

• We probably guess.

VFR into IMC

• How long does it take to make a 180 if you go IMC?– Forever?– 1 minute? (which seems like forever)

• Do you practice 180 standard rate turns under the hood?– Can you do it without climbing or descending?

• Is a 180 turn done at 130 kts any quicker than one at 70 kts?– The faster you go the wider the turn.

Why VFR into IMC

Unable IFR because

• Not instrument rated

• Not instrument current

• Don’t like to talk to ATC

• Unable to get an ATC Clearance

• MEAs are too high(13,000 to 17,000 MEA in the West)

Weather Indicators to avoid VFR into IMC

Cloudbase

• If it lowers, and you’re forced to descend, think about turning around.

• The cloudbase may stay the same, but watch out if you’re flying into an area of rising terrain.

TRFs

• Beware of the many TRFs if you fly in or near mountains.

Hey, don’t you mean TFRs? (Temporary Flight Restrictions)

• No, I mean Terrain

Rises Fast (TRF)

Weather Indicators to avoid VFR into IMC

Cloud Coloring

• Sun shining through clouds is usually good.

• Lack of sunlight through clouds and darkening skies can indicate deteriorating conditions ahead.

Weather Indicators to avoid VFR into IMC

Cloud Type. • Various types of clouds can

indicate deteriorating weather conditions.

• Which of these are bad?

a. Cirrus

b. Cumulonimbus

c. Cumulo-Granite

Weather Indicators to avoid VFR into IMC

Visibility• A reduction in visibility is one of the most important

indicators of deteriorating weather conditions. • Think about going back to that airport you just

passed.

Weather Tools for VFR Flight Decision

• Cloud Bases and Surface Visibility:– Area Forecast (FA) and AIRMETs– TAFs and Metars– Weather Depiction Chart– 12 hour Low Level Sig Weather Prog– Pireps

• Cloud tops, layers, and Inflight Visibility:– Pireps

How to get a weather update inflight.

• Flight Watch (122.0)

• Flight Service (AFSS)

• AWOS and ASOS

• ARTCC

• Weather to the cockpit via satellite, such as Nexrad, Metars, TAFs (eg. XM radio connection to a GPS)– Know your TAF & Metar codes!

Cloud height is important, especially in the mountains.

– METARs and TAFs report the height of clouds “above the ground” (AGL), not MSL.

– OVC040 = Overcast at 4,000 feet above the airport. If airport is 1,000 ft, cloud bases are then at 5,000 feet MSL.

– Valleys may be VFR but mountains may be obscured by clouds.

If you do become IFR:

– Have a Sectional handy.– Mountain MEAs are listed. – If you get into trouble, and you have to go below MEA,

you should know what’s below you! – Its better to drop down into a valley than onto a

mountain.– Don’t get trapped flying into rising terrain and lowering

ceilings with no room to turn around.– Call ATC and get an IFR clearance to a safe landing.

Weather Indicators to avoid VFR into IMC

• A change in the wind direction may indicate a change in the weather.

• If you note a change in crab angle or a change in Ground Speed, and

• The clouds are increasing in density, coverage or height…

• Think about a 180 or landing short of your destination and the weather.

Weather Radar Limitations

• Some Weather Radars are located on mountain tops.– Thus, low level weather may be missed.

• Weather Radar beam does not follow curvature of Earth.– Thus, the radar beam will overshoot some

distant weather.

Thunderstorms

• Severe turbulence in and near. • They like to form in and around the

mountains. • Probably the worst hazard for VFR flights

is Microbursts. • Lightning can strike as much as 20 miles

away from a storm.• Hail can be thrown several miles ahead of

a storm.

Microburst

Microbursts

• Look for ‘Virga’ under cloud.– Virga is rain that evaporates before reaching

the ground..

• Rain evaporates (cools the air)…– Cool air is more dense (dense air sinks)…– Dense air races towards the ground…– Then spreads outwards in all directions.

Microbursts

• Hazards– Winds

• 50 to 100 knots.• Dangerous Wind Shear • Unexpected severe cross winds

– Blowing dust (expanding ring)– Severe downdrafts under showers / virga

• You feel helpless as you watch your VSI go past 2,000 fpm.

Questions ?

TheEnd

Thank You forYour Time