CHAPTER 12 COMMON IFR PRODUCERS

St. Elmo’s Fire

AOPA VFR into IMC

 http://flash.aopa.org/asf/acs_vfrimc/

Scud running

http://www.youtube.com/watch?v=0g WEi_TNKoI

IFR PROCEDURES

 Low ceilings and non-instrument rated pilots don’t mix.

 Attempting to fly visually under low cloud decks can be tricky.  Entering clouds or losing the horizon can cause your senses to deceive even the most experience instrument pilot; causing you to lose your sense of direction and lose control

IFR PROCEDURES

 Usually it takes a good scare to really appreciate the illusions of IFR flight before you change your thinking on IFR weather.

 Calgary-Regina-Grand Forks Trip  Continued VFR into adverse weather is the cause of about 25% of all fatal general aviation accidents.

VFR/MVFR/IFR

 What is VFR weather?

 Weather better than 1000 ft Ceiling; Visibility better than 3 S.M.

 What is MVFR?

 From 1000 ft. - 3000 ft ceiling; Visibility 3-5 S.M.

 What is IFR  1000 ft ceiling or below, vis 3 S.M. or below

CEILING

 Ceiling = the maximum height from which a pilot can maintain VFR in reference to the ground  Ceiling = as the lowest broken (5/8-7/8) or overcast layer (8/8) aloft or vertical visibility (VV) into a surface-based obstruction.

IFR PRODUCERS

 Fog, low clouds, haze, smoke, blowing obstructions to vision, and precipitation.

 Fog and low stratus restrict navigation by visual reference more often than all other weather parameters.

FOG

 Temp/Dew Point Temp spread is 2ºC (4 ºF) and narrowing condensation/ fog/low clouds should be expected. Your book says (5 ºF)  Water vapor must condense for fog to form. If there are no condensation nuclei present then even with 100% relative humidity, fog will not form.

 Salt, dust combustion by products, smoke are all classified as condensation nuclei

FOG

 Fog is a surface based cloud composed of either water droplets or ice crystals.

 With the right conditions fog can form very quickly (few minutes) VFR-IFR.

 http://www.youtube.com/watch?v=6EqQ9V1e5x Q  Be very cautious flying when the temp/ D.P.T. spread is close and getting closer.

FOG FORMATION

 Fog or a cloud may form by:  #1. cooling air to its dew point,  #2. by adding moisture to the air or condensation nuclei.

FOG

 Radiation Fog = Fog that forms on a clear calm night or day break when the surface of the earth is cooled by radiation until the temperature of the air near the the surface is below its initial dew point temp. Restricted to land because water surfaces cool little from nighttime radiation. Usually burns off rapidly after sunrise.

 wind of 5 kts or less mix the air and deepen the fog

FOG



Radiation Fog

=most conducive to form on warm, moist air over low, flatland areas on clear, calm nights

ADVECTION FOG

 Moist air moves over colder ground or water  common along the coastal areas  deepens with winds up to 15 kts depends on the wind to exist  More than 15 kts tends to lift it into low stratus  Moves in rapidly with the wind day or night and more persistent

FOG

 Advection Fog = forms when moist air moves over colder ground or water . Common along coastal areas. At sea it is called sea fog.

UPSLOPE FOG

 Moist stable air cooled adiabatically as it moves up sloping terrain  depends on wind to exist  very dense and can exist at high altitudes along the upsloping terrain

PRECIPITATION INDUCED FOG

 Warm rain or drizzle falling through cool air  evaporation from the precip saturates the cool air and “poof” fog  associated with warm fronts mostly  may also form along cold fronts and stationary fronts  little or no wind

FRONTAL INDUCED FOG

 Usually a result of saturation due to evaporation or precipitation  Either adding the moisture or cooling the air to saturation

ICE FOG

 occurs when temp is below freezing and the vapor sublimates directly into ice crystals  conditions are similar for formation of radiation fog  -25º F or colder so usually found in arctic region or colder winter spots

STEAM FOG

 Air is blown from a cold surface over warmer water  Low stratus clouds  hard to predict bases  scud running not advisable

FOG

 Fog on a METAR is used to indicate visibility of less than 5/8 of a SM

FOG

HAZE AND SMOKE

 Haze - salt or dry particles not classified as dust or something else  occurs in stable air  Smoke forest fires, industrial areas  Both can be bad under a temp inversion  Can cause visual illusions

HAZE AND SMOKE

 Usually only a few thousand feet thick, but sometimes may extend as high as 15,000 feet.  Usually have well defined tops with visibility above great.

 Downward visibility from a haze layer is usually very poor, especially at a slant. Worse if faced into the sun

HAZE AND SMOKE

 Smoke concentrations form primarily in industrial areas when air is stable. It is most prevalent at night or early morning under a temperature inversion but can persist throughout the day.

 Clears a lot slower than fog  Must be dispersed by air movement.

HAZE AND SMOKE

 Needs to be blown away or  Convection which allows mixing and spreading out of the smoke or haze to a higher altitude.

BLOWING PHENOMENA

 Dust, sand  Precip- drizzle, rain , snow  White out conditions  Very common to have 0, 0 weather

BLOWING PHENOMENA

 Can blow particles as high as 15,000 feet.  Visibility is restricted at the surface and aloft.

 Once dust becomes airborne may take several hours for visibilities to improve

BLOWING PHENOMENA

PRECIPITATION

 Drizzle and snow restrict visibility to a greater degree than rain.

 Drizzle falls in stable air and is usually associated with fog (poor vis)  Heavy snow and rain associated with a severe thunderstorm can result in 0 vis.

 With heavy rain visibilities seldom below a mile and usually for a short period of time.

PRECIPITATION

 Freezing precipitation - freezing to the windshield lowers visibility to a few inches.

OBSCURATION



surface based

phenomena  classified in 10ths  VV  ceiling may be noted but once below it horizontal vis may be severely restricted

OBSCURATION

 An obscured ceiling differs from a cloud ceiling. With a cloud ceiling you normally can see the ground and runway onced you descend below the cloud base. With an obscured ceiling, it restricts visibility between your altitude and the ground

OBSCURATION

VISIBILITY

 Ground level, air-to-ground and air-to air visibilities are all important when flying.

 Ground Level - done by weather observer uses a prominent object viewed against the horizon for estimating daytime visibility.

VISIBILITY

 Prevailing Visibility - is provided for aviation by the weather service. It is the maximum visibility common to sectors comprising one half or more of the horizon circle as viewed from the observing site at eye level. It is provided in statute miles.

RVR RUNWAY VISUAL RANGE  For landing and take-off under instrument flight conditions, the prevailing visibility is not of as much importance as the visibility within the runway environment itself.  Requirements is that of the runway lights rather than ground feature.

 Measured by an instrument called a transmissometer

RVR RUNWAY VISUAL RANGE  RVR is measured in feet in North America.

 Values are measured by transmissometer mounted on 14 foot towers along the runway 250 feet apart typically.

 1,600=1/4  2,400=1/2  3,200= 5/8 5,000=1mile

RVR RUNWAY VISUAL RANGE  Air to ground visibility - prevailing and rvr are horizontal visibilities near the surface.

 Air to ground is forward visibility, typically lower then the above two  SVR slant visual range - slant visual distance used for the choice to continue to land or not.

ILLUSIONS IN FLIGHT

 AIM 8-1-5  The leans - An abrupt correction of a banked attitude, which has been entered too slowly to stimulate the motion sensing system in the inner ear, can create the illusion of banking in the opposite direction. The disoriented pilot will roll the aircraft back into its original dangerous attitude, or if level flight is maintained, will feel compelled to lean in the perceived vertical plane until this illusion subsides



ILLUSIONS IN FLIGHT

AIM 8-1-5  Coriolis illusion - An abrupt head movement in a prolonged constant-rate turn that has ceased stimulating the motion sensing system can create the illusion of rotation or movement in an entirely different axis. The disoriented pilot will maneuver the aircraft into a dangerous attitude in an attempt to stop rotation. This most overwhelming of all illusions may be prevented by not making sudden, extreme head movements (especially while turning)

ILLUSIONS IN FLIGHT

 False Horizon - Sloping cloud formations, an obscured horizon, a dark scene spread with ground lights and stars, and certain geometric patterns of ground light can create illusions of not being aligned correctly with the actual horizon. The disoriented pilot will place the aircraft in a dangerous attitude

ILLUSIONS IN FLIGHT

 Graveyard spin - A proper recover from a spin that has ceased stimulating the motion sensing system can create the illusion of spinning in the opposite direction. The disoriented pilot will return the aircraft to the original spin.

 Graveyard spiral - Constant rate turn descending can cease to stimulate your senses, so that you believe your wings are level. Pulling back on the controls tightens the spiral even more

ILLUSIONS IN FLIGHT

 Atmospheric illusions - Rain on the windscreen can create the illusion of greater height, and atmospheric haze the illusion of being at a greater distance fro mthe runway. The pilot who does not recognize these illusions will fly a lower approach. Penetration of fog can create the illusion of pitching up. The pilot who does not recognize this illusion will steepen the approach, often quite abruptly.

ILLUSIONS IN FLIGHT

 TRUST YOUR INSTRUMENT  READ 8-1-5 IN YOU AIM IF YOU GET A CHANCE

IFR

 If you can go IFR, get a clearance before you lose your horizon or enter clouds.

 If VFR make a 180. Any pilot knows how to make a 180; a good pilot knows when!!!!!

 Don’t get “get to your destination itis”  Wait until the weather is good for VFR

QUESTIONS

 Where can you encounter wind shear?

 Any altitude, can be both in the horizontal and vertical direction.

QUESTIONS

 When is it more likely to have radiation fog form?

 Over land clear calm nights

QUESTIONS

 When is it more likely to have advection fog form?

 Along coastal areas

QUESTIONS

 When is it more likely to have steam fog form?

 Over a water surface

QUESTIONS

 What types of fog depend on wind in order to exist?

 Advection fog and upslope fog

QUESTIONS

 In industrial areas low clouds and fog are common why?

 Increase in cloud condensation nuclei.

FMH-1 CHAPTER 12

 METAR KMWH 092052Z 22003KT 10SM SCT009 02/M02 A2981 RMK AO2 SLP105 6//// T00171022 55000 PNO $  6=3 and 6 hour precip amount  ////=indeterminable amount of precip  If 2.17 inches of precip occurred would be coded 60217

 METAR KMWH 092052Z 22003KT 10SM SCT009 02/M02 A2981 RMK AO2 SLP105 6//// T00171022 55000 PNO $  5=3 hour pressure tendency  Next digit need to reference table 5 on the table = atmospheric pressure now lower than 3 hours ago decreasing then increasing  000 = amount of pressure change in tens of hectopascals  52032 = steady increase of 3.2 hectopascals in the past three hours

 METAR KMWH 092052Z 22003KT 10SM SCT009 02/M02 A2981 RMK AO2 SLP105 6//// T00171022 55000 PNO $  PNO = when automatic stations are equipped with a tipping bucket rain gauge and that sensor is not operating PNO shall be coded  $ = maintenance is needed on the system