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Weather Flying Decisions
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Flying in Weather; ...Weather Training; ...VFR Weather; ...Effects of Density Altitude; ...SVFR; ...Visibility; ...Haze; ...Go-No Go Decision; ...VFR into IFR; ...Weather Planning; ...Low Visibility Effects; ...En route Decisions; ….PIREP; ..Turbulence; ...Avoiding Convection; …What to Do in Convection; …Summer Thunderstorms; …Turbulence Flying; …IFR Weather; …Weather Items; …Fog; ...There Is Fog in Your Future; …About Severe Weather; …Tornado Safety; …Avoiding a Thunderstorm; …Riding a Thunderstorm; …Flying in Convection; …Opinion; ... Written Test Weather; …Weather on Items; Cold Weather Preparation and Knowledge; …Frost; …Flying in the Weather; ...Events related to VFR flight into Sierras: ...
Flying in weather
Preflight must include pre-heating the engine and oil, fingertip examination of flying surfaces, and free movement of controls is essential. Don't hand prop to start on a slippery surface. Deicing is best done inside a hangar. Some deicing fluids may adhere to the flying surfaces and act just as ice would in destroying lift. Some aircraft are powerful enough to takeoff with out tires rolling. Check tires for their ability to roll.
It is a practical understanding of weather that keeps aviators safe. Any trip of 750 miles is sure to encounter below VFR weather. Anytime the weather gives you doubtful feelings it is best to exercise the judgmental skill that cancels the flight. By knowing the weather you can know what you would do before the need to make a change in plans. Safety lies in knowing how to deal with the weather within the operating limitations of your aircraft. It is not a "failure" to cut your potential losses by turning back. On the other hand, you will fly in weather if the utility of flying is important.
Pilots and passengers die every year from exposure to the weather elements. Usually, death is a result of failure to anticipate the possible weather and dressing accordingly. Hypothermia is the culprit and it takes only wind, not cold to bring death. Wind plus being wet accelerates the onset and ultimate result.
The most dangerous weather is that of which you are unaware. The signs of adverse weather are always available if we look for them. Wind shear is never inadvertent. There is a ratio between safety and aircraft utility. This ratio varies with every flight. By taking the time to study the probabilities, keeping the final briefing inside the hour of departure, and (ideally) getting a look at the radar depiction you will not be surprised.
Begin your cross-country flight planning four or five days before the day of the flight. Continue your planning right up to the day of the flight. You make adjustments, including cancellation, based upon any information that will not fit into your model of what it takes to make a safe flight. In the Nino year past experience must be set aside and forecasts as well as plans will be flexible even to the last moment.
You are looking at the jet stream locations, frontal movements, and airflow around pressure centers. You are looking to atmospheric instability that will cause weather you do not want to encounter. You don't want rising air and condensation. A good pilot must apply what he has learned to what he sees happening. The good pilot will insist on at least one standard briefing before the flight. Inform the briefer of your total planned flight as well as any options you can think of. VFR you don't need an alternate but you should have an alternate plan anyway. Follow up with abbreviated briefings just before departure and stay in contact with Flight Watch. Accept VFR flight not recommended (VNR) and any mention of icing as sufficient reason to re-think making the flight at all.
Daylight Savings Time changes the way we fly. We do not fly as frequently so the accident frequency declines and the influence of weather on the occurrence of accidents increases. This is a time of more night when those accidents that do occur tend to be more serious. Accident rates at night tend to occur more often the less experience at night the pilot has. Night flying difficulty is directly related to what VFR pilots see outside and what IFR pilots see inside. Aircraft and ATC system failures are more critical at night. The transition from instrument to visual by the single IFR pilot is a killer.
There is no FAR that requires a pilot to make in-flight weather checks but thanks to Flight Watch this is easy to do from 6 a.m. to 10 p. m. local time any where in the United States. There is only one nationwide frequency of 122.0 that is available almost anywhere above 5000' AGL. For situations where 122.0 won't work consider the high-level frequencies of 135.7 or 134.52 frequencies usually reserved for high altitudes. The process of contacting Flight Watch only requires that you include the name of the closest VOR along with your identification. You will know you have a weather problem when you experience turbulence and cumulus clouds.
So called Judgment errors cause most aviation accidents. Terrain is a frequent corollary for judgment errors, actually nearly 30 percent. Another 70 percent are related to VFR weather into IFR weather, fuel complexities, exceeding aircraft capabilities and social pressures.
1996 weather related accidents was 68.2% with 58.9% being VFR into IMC. It is my opinion that proper exposure to weather conditions in familiar areas will enable a pilot to maintain situational awareness and make sensible avoidance decisions. To teach this requires that we fly into weather. Never fly into deteriorating weather and always fly into improving conditions.
Gradual exposure into the conditions along with the limitations of VOR navigation and radio communications is important. I feel that only exposure to these conditions in an instructional situation can overcome the emotional and intellectual paralysis that accompanies a virgin entry into such conditions. I have so exposed every student I have ever taught and have empirical evident that it is the way to go.
Every lesson is a weather lesson. We look at the windsock, the clouds, and the winds before getting the plane. After solo I deliberately plan a SVFR flight back and fourth between neighboring airports. Living on the West Coast makes finding this situation relatively easy. These are airports that we have flown to before but under better weather conditions.
It is only by actually experiencing such a flight can a pilot can fully understand just what is meant by remaining within 700' or 1200' AGL while remaining clear of clouds. Counting 5000' runways for each mile visibility can be difficult. It helps if you are so familiar with the airport checkpoints that you can give an exact building, bridge, intersection or common visual checkpoint when ATC asks for a position report. This kind of flying is not recommended in unfamiliar territory. The advent of El Nino has made for some strange weather but when traditional patterns return it becomes possible to make more realistic projections micro weather areas.
Determined by visibility, cloud clearance, and ceiling
Standards for VFR below 10,000' and night:
Visibility of three miles
500 below, 1000 above, 2000 lateral of clouds
Ceilings 1000' AGL
(Night exception 1/2 mile of runway below 1200')
Class G Airspace Operations;(700/1200 AGL)
Visibility 1 mile daytime
Clear of clouds
Effects of Density Altitude
Heated molecules increase in speed and need for a greater space. The distance between them increases and the density decreases since for every unit of space there are fewer molecules. Lifting surfaces rely on the weight of passing air molecules to produce lift. Altitude density varies from sea level to space. A wing produces the most lift at sea level because of the density (closeness together) of the molecules. In space a wing does not produce lift since there are no molecules.
In the atmosphere, the air molecules near the surface of the earth are held closer together through molecular attraction and gravity than those molecules higher up in the atmosphere. The higher up you go in the atmosphere, the fewer the molecules. Density decreases as you go up in altitude.
Factors are altitude, temperature, humidity and low barometric pressure. Effects are wings lose lift, propellers lose efficiency, and nonturbo engines lose power. Results are that higher true airspeeds are necessary taking longer runs before reaching rotation speed. The climb will be more shallow even at higher true airspeeds.
A 2000' altitude above sea level will result in about 25% reduction in takeoff and climb performance. A sea level rotation of 70 knots ground speed will be 80 knots ground speed at 8000'. Even turbo performance only helps engine power without any effect on propeller efficiency or wing lift. You should double all book(POH) numbers because there are complicating factors such as the following.
True airspeed is only varied by about 5% by leaning. Speeds will be faster the cooler it is. This extra speed is reduced somewhat by the drag of denser air.
--The time of day that you fly makes a great difference.
--The lighter you fly the better your performance. you may be well advised to make two flights with half load instead of one flight that doesn't get you where you are going. A 20% reduction in load gives a 36% performance increase.
--Learn to manage the mixture. Lean for altitude, takeoff and climb. Without an EGT lean for peak rpm. You can lean at less that 75% power even for takeoff. With an EGT you can use the EGT setting of a cruise altitude as a takeoff reference setting. Except for full power rich mixtures are unnecessary. Keep the mixture leaned during descent to keep the engine warmer.
--The best way to learn flying at density altitude conditions is to fly with an experienced pilot several time into different conditions. This will relieve anxieties you probably have that only knowledge can overcome. Personally I flew across the Sierras three times with an instructor before attempting the flight by myself. I have never regretted the time, cost or experience in doing those flights.
--Headwinds require the use of more power to mitigate the percentage effect adverse winds have on ground speed. Fly faster into headwinds. The slower you go the more important it is to use fuel planning.
When you are flying VFR in Classes C, D and E airspace and in radio contact when weather conditions become below VFR minimums you can request get a SVFR clearance.
Requires clearance at airport
1 mile flight visibility
Clear of clouds
Night: IFR airplane and pilot
Even under the new METAR system visibility is usually given in the U.S. as statute miles. Ground visibility is reported at airports as distance over at least 50% of the horizon. The pilot is bound by the reported ground visibility and must have the required visibility to operate in Classes B, C, D, or E airspace. See FAR 91.155(d) However, the pilot will be using flight visibility while flying. Flight visibility is the distance you can see in the direction you are flying. When visibility is not reported you can fly using flight visibility. See FAR 91.155(a). Touchdown zone visibility is measured by a transmissometer and is given as visual range in feet or fractions of miles.
Haze can be a serious problem where spatial disorientation can follow lack of situational awareness. You can out-fly your visibility and checkpoints. Haze is caused when the air contains relatively high amounts of water vapor and dust particles to the point that visibility is diminished. An airport at less than five miles may be reported by you to be up to fifteen miles away because it is so hard to see. You can see down but the slant range visibility is an illusion and deceptive. The position of the sun low on the horizon either morning or evening that requires you to look into it is particularly hazardous. In this case my recommendation is to over fly the airport and come in with the sun behind you. The difference in visibility is dramatic.
Go-No Go Decision:
--VFR flight into IFR has only 10% of the accidents but 82% of the fatalities.
--The most difficult forecast is ceiling and visibility.
--Any flight into marginal conditions is more likely to be in error. Error either way that is.
--The greatest errors occur in time. The weather will happen but betting on when is a crap shoot. Don't bet on improving
weather at the time forecast.
1. Reduced visibility and haze may require instrument flight.
2. Morning flights are smoother.
3. Approach ridges at 45-degree angle
4. Fill tanks on landing to avoid night condensation.
5. Always carry water and have it available.
Learn to watch trends. A rising altimeter setting indicates improving weather. If the temperature/dewpoint spread is getting wider then things are improving. If in the air, don't fly over an undercast unless you know you can reach VFR. Don't fly under a ceiling that is forcing you ever lower. Winds that are different than forecast are advanced warnings that other parts of the forecast are going to be wrong.
1. NoGo if known icing
2. NoGo if ice forecast at flight altitude
3. NoGo if forecast conditions may be worse. Don't fly into deteriorating weather conditions.
VFR into IFR
Unintentional VFR into VMC can happen to anyone. The ability to forecast just when a weather change is going to occur is still for the future. Even the most careful pilot cannot always accurately time his weather avoidance.
I live and fly on the West Coast and never cease to be surprised with the way weather seems to evade accurate prediction. I try to be selective in my weather flying by taking my students into marginal but improving conditions. Improvement seems to progress more slowly than deterioration. I have had fog close my home field from full VFR to zero-zero during the time of preflight. We get both avection and radiation fog often in consecutive days depending on conditions. Many of the S.F. Bay valleys have micro-climates that defy prediction.
I do believe that a 'California' instrument rating is a very valuable flying asset but extremely difficult to keep current. I believe that both the private and instrument ratings are best acquired during the late fall and early spring since it gives the trainee exposure to the entire weather gamut available over a period of four or five months. Woe is to the pilot who learns during the summer because they are doomed to remain on the ground for many months before summer comes again. A pilot needs exposure to the vagaries of coastal weather that cycles from sea to central valley and back again every eight days. It has taken me many years of study and observation to evade the mistakes of the weather forecasters.
California coastal weather is always changing. Often the status of good or bad is contradictory depending on the desires and intentions of the pilot. I have lately cancelled a number of flights because the weather has not been IFR enough for what I wanted to teach. At the same time I have been unable to do a number of SVFR lessons because the weather improved too rapidly.
The field of weather prediction has still to accurately time the arrival of weather consistently. The coast has a lack of
airports and a corresponding lack of PIREPS. A PIREP is real-time weather for a specific place and time. This is weather you can believe. Be cautious in reliance on ASOS and AWOS. My home field has had one for nearly two years and it is yet to be certified for use.
The weather patterns are a changing worldwide. When people from all over the world come to San Francisco they must be prepared to unusual weather. July can be quite cold; last December was the third warmest on record. Once a year thunderstorms are now occurring monthly. Storms line up on the jet-stream and march through with only two-day breaks. Occasionally, a storm will pause and drop rain for three days before moving on.
You can avoid weather problems by staying on the ground. You can fly in certain 'bad' weather conditions if you always have a backdoor escape route and know exactly where you are. Getting on the ground is always a desirable option. Get down and settled before dusk. Any weather will be worse at night. Be ready to change any preconceived plans. Be prepared to wait-out the weather.
Visibility is the most obvious weather factor likely to abort a flight.
Most weather factors can be flown under, over, or around. Not so easily with low visibility.
Low Visibility Effects:
--Avoidance of embedded weather is difficult.
--Reliance on pilotage and VOR navigation becomes uncertain.
--Disorientation is a real possibility. Use GPS if possible.
--CFIT (controlled flight into terrain) becomes a hazard.
--Avoid being caught on top.
--Don't try to out climb a rising cloud. You can't.
--Live with rain. When it exists avoidance except for improved visibility is unlikely.
--Don't fly under dark clouds that may be the base of an embedded thunderstorm.
--Avoid turbulence. Don't fly into forecast turbulence or ice.
--Note how winds affect your adherence to route and planned speed.
En route Decisions
Know where the severe weather is.
Know where to go to avoid problems.
Check the weather often on 122.0.
PIREPS are your best friends.
Don't expect to influence the weather.
You won't go wrong making the safe decision
Begin by just calling up and the name of the nearest VOR and relationship to a prominent checkpoint if possible. You can help the system of giving the PIREP work better by giving the information in the correct order. Use navaids for location not local checkpoints. Give your aircraft identification, type, altitude, flight type, departure point, destination, and route.
Sequence of PIREP FXormat:
UA or UAA Urgency of information
TP Type aircraft
SK Sky cover and altitude
WX visibility, precipitation
TA Temperatrue in C
WV Magnetic wind and velocity
UA(A), OV, TM., FL, TP, SK, WX, TA, WV, TB, IC, RM
Design a ten word sentence:memory aid.
Unless Old Timers Fly The Skies weather takes wing
Over Time Flying Types the skies weather tempers; the bumps I see remain.
PIREPS are retained for only one hour.
1. Secure cockpit
2. Light touch
3. Fly attitude not altitude enroute
4. Bumpy clouds are bumpy top and bottom.
5. Never enter a cloud without knowing what's inside.
6. Slow down before entering a potential turbulent area.
7. On approach go to smooth air alternate.
8. Turbulence is distracting...use your checklists.
9. LLWAS Low Level Wind-shear Alert System at airports
Proximity to the ground allows little time to recognize and respond to turbulence-induced control difficulties. Accident cause is usually, "The pilot's failure to maintain control of the aircraft." Turbulence accidents usually occur in high drag configuration and low speeds. Knowledge is the only known antidote for overcoming concerns related to turbulence. Knowing what causes it will allow you to avoid it. Science is working on a turbulence detection system but 90% of effort is to devise a method that pilots can trust.
Where you have great changes in air velocity you will have turbulence. This can occur as a ventrui effect in a mountain pass or over an obstacle. Air is much more affected than water because it is light and has little viscosity.
Fly early in the day before sun causes thermals or late afternoon when sun's effect is lower. Carry extra speed on any approach experiencing turbulence, diversion to another airport is a good option. If turbulence affects your ability to remain on the approach heading and altitudes, execute the missed.
Watch the weather for a few days before a flight. Get the area forecast (FA)(TAF) which will give state by state hazardous weather. Radar reports (rareps) and severe weather outlooks (AC) will give real-time updates of storms, intensity, and movement. TAFs exclude temperature, turbulence and icing forecasts.
ACs show storm area by intensity and area of coverage. ACs come out at 12Z and are accurate and reliable indicators of things to come. Rareps tell what is now. Rareps can be over three-hour old. Text type convective sigmets tell about level-four or greater storms of over four-tenths coverage. Since briefers often fail to cover these, be sure to ask for any convective sigmets.
If the forecast indicates convection problems, leave early in the morning, get on the ground before 11 A. M., stay visual with flight following. File IFR but request vectors around convective activity. Don't let yourself be forced low in mountains. Use Flight Watch. If in doubt, do a 180 and land. Avoid all storms by 10 miles or more. Don't fly so that the storm blinds any radar coverage. Wind velocity changes of 15 knots and vertical velocity of 500-fpm or greater are hazardous. Vertical velocities of over 4000 fpm and wind speed changes over 90 knots have been recorded. Every downdraft that reaches the ground sends out horizontal winds in all directions just as spilled water does.
It is easier to get ATC help in convection (thunderstorm) avoidance once you are away from terminal areas. It is harder for ATC to give you an altitude change than a course change because of the coordination required with other sectors. ATC radar can only detect two levels of precipitation. Light rain is shown with ////slashes and heavy rain with HHHHs. ATC cannot see thunderstorms.
ATC can give departures more help than arrivals because departures tend to be more spread out. Make a decision to divert early. It is easier to change airports before the IAF than being committed and having to do it
from the missed approach. The more time you give ATC the better they can help you.
Basic truth is that updrafts are not rising so much as being displaced below by cold air. The movement of cold air causes the warmer air to be displaced upward.
--Flight Watch updates
--Virga presence is warning
--Thunderstorms within 20 miles
--Get on the ground
--Extra airspeed on approach
What to Do in Convection:
1. Tighten everything
2. Pitot heat
3. Slow down, drop gear
4. Interior lights on high
5. Use only instruments
6. Don't turn
--Thunderstorms, cumulus or virga in area
--Temperature over 80o
--Temperature/Dew Point spread more than 30o
--Blowing dust, dust devils, gust fronts
--Extreme variations in wind direction/velocity
--Being downwind of virga or thunderstorms
2) Longest runway
Watch for sudden changes in airspeed/performance
Don't change configuration
First clue is increase in airspeed followed by stagnation and loss of altitude.
Apply maximum power
Accept low airspeeds
Don't lower nose-best pitch climb attitude
Hang on, the greatest danger is in over-control by the pilot
1. Fly at least 7000' above terrain if equipment (oxygen) allows.
2. Fly early and be on the ground by noon
3. Slow down and stay out of the yellow airspeed arc
4. tay above 1.5 stall speed else a bump may cause a stall
5. Set your power for turbulence before you get into it.
6. Lower landing gear
7. Ride with what ever altitude you get. Advise ATC of the problem and get a block altitude which lets you ride up and down between altitudes.
Cows face into the wind ???True??
Sheep face away from the wind
Windmills face into the wind
Major highways have frequent straight sections
Towers come in bunches but never right over the road.
1. Avoid cells by 20 miles and more if the cells are moving faster than 20 knots.
2. Cells at the south end of a line are worse.
3. Strong T-storm indicators are (1) surface dew point above 50 F with over 30 degree spread to temperature.
4. Check AC convective outlook. Warning area is very dangerous.
5. Winds at 18000 that are from the southwest are T-storm indicators.
6. Flying in the a.m. is best.
7. Don't depart with T-storms within 20 miles.
What if the weather had deteriorated? I was unfamiliar with the airport and severe weather would have required me to do the following.
1. I would keep the wings level, reduce speed to Va for my lighter weight
2. Would request vector to nearest or 180 as applicable
3. Would ask about minimum altitudes and ask for a block altitude referenced to it.
4. Would double check freezing level and try to stay under it.
5. It could be that flying to the 'light' does not always work in cumulus clouds but does in stratus clouds.
What do you do if your personal minimums don't go down to 500 and one? Any approach or takeoff with this weather demands that the pilot have some skill and experience operating in this level. Even then being familiar with the airport layout, terrain and obstructions gives some additional comfort. It would be nice if you have 'home field' advantage.
Take all of these things away your survival option is to head for an alternate. Don't even 'take a look'. The pilot who takes off from a runway and airport to which a legal return approach cannot be made has no right to take others with him. Even by yourself you should have a takeoff alternate.
One dot off the localizer is 300' at the outer marker. At the middle marker one dot is 100 feet. The one dot at the outer marker for the glide slope is 50 feet. The glide slope at the middle marker has only 8' for one dot variation. The glide slope never reaches the runway. It flares at 50' for a ways and then rises. This could be a problem for an autopilot-coupled approach. Exact values will vary.
Low IFR conditions are right at the line where the MDAs of non-precision approaches exist. Even at home, you will be better off going for an ILS somewhere else. My part of California has periods of large areas of low IFR conditions that mean a C-172 would have a hard time getting to an alternate. However there is usually a VFR escape on local mountaintop airports. It behooves the pilot to know where these airports are. The more options you have the safer the flight.
Ceiling is reported as AGL when give locally.
Area ceilings are given as MSL unless prefixed with C or CIG
Cloud tops are given as MSL
The average total time of pilots involved in icing accidents is over 3000 hours.
Icing accidents of experienced pilots occur at airports and are usually survived.
Icing accidents of inexperienced pilots are usually off-airport and fatal.
It is the vertical air currents inside the storm that creates turbulence and lightning.
--Being on the west side of the low and hoping to land on the east side.
Worst weather is always on the East side. Problem was to fly to the right or
left around the low.
When planning a flight we research weather and become focused upon areas of concern. This focus may cause us to miss side issues that await nearby. An emphasis upon weather fronts may miss freezing levels or fog potential. Unlike thunderstorms, fog is created when temperatures and dew points merge but are not lifted.
It is the existence of condensation nuclei in a minimum density of over 75,000 per square inch that makes fog possible. Below that level the water vapor will attach to the nuclei but it takes
hygroscopic nuclei to cling to the moisture in sufficient numbers and droplet size before the moisture becomes visible and able to reflect light. The point of visible moisutre is critical and slight changes in wind or heat will make it appear and disappear. When the relative humidity is about 60% it is called haze. At 100% humidity we have fog.
Radiation fog is predictable and occurs close to the groun in calm stable air conditions. The cooler air and layers of fog are closer to the ground. This reversal of hot and cold air is called an inversion. Waterside airports are often subject to radiaton fog that may stay all day. An aircraft over head may be able to see the airport but an airplane on approach may be unable to find the airport due to slant range visibility. The more moisture on the ground the longer will the fog persist. Radiation fog will only disappear when the moisture evaporates from the nuclei and the relative humidity reaches about 50%.
Advection fog arrives as a layer and expands into a layer several hundred feet thick which can cover entire regions. Advection fog may be initially very close to the ground but as the day progresses the base will rise to a thousand feet before it thins and disappears. Advection fog will lift and gradually dissipate as the sun rises.
There Is Fog in Your
---Clouds and fog are the same except for the way they form
---Cloud formation involves turbulence, while fog does not.
---There are six types of fog, three of which are on the West Coast
---Worst and rarest is stratus between 1,000 and 1,500 feet, but occasionally on the ground
--Fog is has been and continues to be a major flight hazard.
--We fully understand the meteorology of fog, it is forecasting arrival or dissipation that is the problem
--We have improved estimation of fog probabilities but accuracy is still lacking.
--It is up to the pilot to be able to recognize and plan around the temperature/dew point parameters of fog
---Radiation fog is a shallow fog from radiation cooling of the earth on calm, cloudless nights.
---The earth cools the humid air it, causing condensation.
--Forms on clear cool nights in light winds with less than 7 degrees of dew point temperature spread.
--Heat rises from ground, this cools the ground and the air next to the ground.
--Any moisture on the ground condenses and forms fog usually no thicker than 300 feet.
--Radiation fog that is 20 feet thick is called ground fog.
--Valley fog is a type of radiation fog that flows downhill into bottom of closed valleys.
--Radiation fog usually tends to burn off as the sun rises and warms the air, but…
--The heat from the sun may burn through the fog to moisture on the ground and cause fog to reform again.
---Usually it is advection fog forming off the Pacific coast when moist air passes over the cold Ocean.
--Advection fog in CA forms at sea and is blown or sucked inland by hot inland temperatures
--- This is the fog and low clouds that run the eight day summer cycle air conditioning of the Bay Area.
--Advection fog may reoccur over a period of days and nights to move further inland each successive day
--Advection fog is formed when air moves over cold ground and is cooled to the dew point.
--Advection fog may maintain a level of several hundred feet above the ground as it moves inland.
--The fog may have a base from two to 600 feet and a top of 900 to 1500 feet.
--The fog thickness decreases each day as it cycles its movement inland and back out to see in CA.
--The inland temperature changes determine the inward movement and retreat of the advection leading edge
--Since there is little uniformity in the coastal inlets and valleys of CA, each will have its own climate.
--Living it a specific area often allows you to become knowledgeable as to how advection fogs will progress
---Elsewhere it is the upslope fog is common as moist air masses are blown and lifted by mountains
--Air that is blown uphill will expand and cool so that at the dew point it will condense and form fog.
--Depending on the geography all three of the fog types may occur in conjunction
---Precipitation fog exists where warm rain falls on cooler air, raising the humidity giving fog
---Precip fog derives where warm fronts exist but can occur with other types of fronts when moving slowly.
--Rain falling through air that is near its dew point will condense into smaller drops and make fog
--Rain fog is sometimes called frontal fog since it occurs on arrival of a warm front
--Reduced visibility is a major flight difficulty
--On cool days fog will rise from surface water when cool air moves over warmer water.
--Can be formed from any of the above fogs when the air temperature is below freezing.
--When the fog droplets are super cooled they form a layer of ice capable of preventing flight.
---Ice fog is a type of radiation fog in cold conditions where the fog is formed as ice crystals.
About Severe Weather
The U.S. experiences more severe storms and flooding than any other country. We have 10,000 thunderstorms every year along with 1000 tornadoes and several hurricanes. Two out of five hurricanes will be severe. 45 million U.S. Citizens now live in hurricane country.
Storm probability are forecast four times a day. Probability is given as a percent that the center of the storm will pass within 65 miles of some 44 selected points from Brownsville, TX to Eastport, Maine. Places between two points have a probability of their average.
--62% of U.S. tornadoes are classified as weak.
--Weak tornadoes have winds below 100 mph but kill 3% of the people killed.
--1/3 of the tornadoes have winds of 200 mph, are 200 yards wide travel about nine miles and are 'strong'.
--30% of the nations tornado deaths are caused by 'strong tornadoes.
--2% of the tornadoes are 'violent'. Winds exceed 300mph, can be a mile wide, and travel over 25 miles.
--Violent tornadoes cause 70% of the deaths.
--Tornadoes travel 30 mph.
--A thunderstorm near large hail occurs with a tornado.
--Most tornado deaths are caused by flying debris
--The higher the tornado, the stronger the winds.
--A tornado sounds like a passing train or large aircraft.
--Most tornadoes occur in the afternoon and early evening.
--Most tornadoes occur between March and July
Avoiding a Thunderstorm
…VFR and 20 miles clear of T-storms
…Don't fly through gaps
…Don't fly over
…Don't fly under
…Get good briefing on weather
…Turn back and land when cells lie ahead.
Riding a Thunderstorm
As soon as you read or hear the word instability in your weather briefing you should realize that staying on the ground may be your best option. Stable air and unstable air differ in terms of temperature and humidity. The gusty winds and turbulence that exists in mildly unstable air takes very little change in temperature and humidity to become the thunderstorm heat engine.
The driving force is the lapse rate which comes in two forms. First is the environmental lapse rate. It is the rate at which the temperature usually decreases with altitude in stable air. This environmental lapse rate is the one than changes usually for every thousand feet 3.5 F and 2.0 C degrees. At one time only 700 balloons were used twice a day to get this information. Today, every airliner transmits the data to the world satellite system.
The other lapse rate is called the adiabatic lapse rate. This rate is used for air that is moving up and down. The word adiabatic means that the air is heated or cooled without any outside forces other than the vertical movement of the air. Adiabatic air expands as it rises, as would a bubble. The pressure drops and the expansion of the bubble requires heat. The heat comes from the air molecules inside the bubble. This cools the bubble. The standard adiabatic lapse rate is 5.5 Fahrenheit or 3 degrees Celsius for every 1000 feet of rise. This rise requires that no condensation take place. At some point the rising air temperature will reach the dew point and condensation will occur. Condensation releases all the latent heat. Now the bubble is cooling at the moist adiabatic rate, which averages 3.3F, or 1.8 C per thousand feet.
It is these two lapse rates in conjunction that determines the stability of the air. Air that tends to return from whence it came is stable. Air that stays warm and confutes to rise is unstable. When condensation occurs inside the bubble the temperature difference increases the rate of upward movement. As this rise occurs the outer cool air descends. This process is called convection. While stable air gives poor visibility by allowing pollution to exist, convection clears the air. These two conditions can exist at the same time. At times the stable air exists above the insatiable in a situation called an inversion. The warm air rests as a layer above the cooler air.
Flying in Convection
--Hold as near level attitude as you can.
--Slow to Va
--Extend gear but not flaps
--Activate all anti-ice
--Tighten belts and turn up lights
--Maintain only hading; ignore altitude and avid turning
--get block altitude from ATC
When you talk about an "unstable" air mass and the "adiabatic lapse rate" you are talking about the effect of heating a patch of air near the surface, such as over a blacktop parking lot.
When such a chunk of air is warmed a bit it is rather like a "hot air" balloon without a fixed envelope. Since it is warmer than the surrounding air, it will be a bit less dense, and will rise.
The stability question is, once started rising, will it continue to rise indefinitely, or will it damp out and stop after a little bit? The adiabatic lapse rate is the rate of heat loss due to expansion that the bubble of air will experience as it rises. If it cools itself down by expansion faster than the surrounding air cools off (stable air) it will soon reach the same temperature and therefore density, as the surrounding air and it must then stop rising.
If the surrounding air cools at the same rate, or faster, the rising bubble will remain warmer, and therefore less dense, than the surrounding atmosphere and will therefore continue to rise. In some cases it can rise all the way to the stratosphere.
The stratosphere is the part of the atmosphere where the air temperature rises as altitude increases. This is "ultrastable" air, and clouds and thermals can never penetrate into the stratosphere. We try to fly our
airliners up in those regions for that reason.
When the air temperature in the rising bubble drops to the "dew point" of the original air bubble, the moisture in the air in the bubble will begin to condense. It then becomes visible, creating a cloud. It also releases
540 calories per gram of moisture into the air bubble, injecting considerable heat into the bubble and giving it a renewed upward impetus. That is the reason cumulus clouds are relatively flat on the bottom, determined by
the dew point altitude, and bulgy on top as the bubble of moist air surges up above that level.
When air rises high enough that the moisture starts to freeze, it releases another blast of heat, 90 calories per gram. The heat goes into the air bubble and the resulting vertical development, along with the "static electricity" effect of these moving particles of ice rubbing against each other, can easily cause the original bubble of warmer air to become a thunderstorm!
A thunderstorm can rise all the way to the stratosphere. At that level, it can't rise any higher, and the top blows away downwind creating the familiar "anvil top" of the fully developed thunderstorm. Sometimes the ice chunks, carried up through the center of the storm by the updrafts, will get thrown up into the anvil and blown away down wind where they fall as hail. Hail can fall several miles downwind of the storm that produced it.
If you detour around scattered thunderstorms, my enduring recommendation is to do so on the UP-wind side of the storm! :-)
--Know the way the test maker uses words to fool you.
--It is not just finding the correct answer as it is finding the most correct answer.
--Weather questions come from the 'Aviation Weather' AC, often straight from it.
--Study guides usually list the source for each question.
--You can usually eliminate one or more of the choices because of key words or phrases.
--Know what occurs when moisture changes into its various forms.
--You must know the exact definitions of each variation of moisture
--The obvious answer may be correct.
--The obvious answer may be correct but only in one instance whereas another is always correct.
--Some times it is necessary to rephrase a question or answer to clarify the meaning.
--The better your vocabulary the better you should do. Learn synonyms and antonyms.
--Before the final decision you must decisively eliminate the others.
--The better you understand the concepts and theory the better you will make answer selection.
--The questions are not testing what pilots need to know.
Weather on Items
--The mother source of all weather is the sun.
--The unevenness of the spin and orbit of the earth causes weather variation, wind and barometric differences.
--Differences between the tropics and polar regions cause pressure differences resulting in storms.
--The physical changes in earth sun relationships cause rise and fall of storms, high and low pressure regions.
--Moisture is key element of atmosphere that in its various forms makes the major weather differences.
--Air contains moisture, which has three basic forms of vapor, water and ice.
--Pilots must know the changes back and forth of the three-moisture forms cause, effect and identification.
--Terminology related to moisture is essential to understanding and identification.
--Water vapor is always in the air but seldom below 10-percent humidity. At 100-percent it is visible.
--Depending on temperature and wind condensed moisture can exist in many forms.
--When dew point and temperature are equal, humidity is 100-percent and moisture is visible.
--Visible evidence of condensation occurs when dew point/temperature spread is about five due to air particles.
--Water vapor can skip a normal step in the change process by sublimation and go directly to an ice form.
--Water vapor can even form water that is 'supercooled' to below freezing.
--The naming of a cold or warm front is determined only by the preceding front and NOT its temperature.
--A cold front may have a warm temperature and a warm front can be quite cold.
--Coriolis force from the spinning earth causes winds to follow a curved route.
--The sun is the source of almost all of the energy causing weather.
--A temperature inversion may take precipitation from snow to rain and forms of ice on reaching the surface.
--Ice pellets are pencil lead pieces of ice that fall only in the storms of winter and are often called sleet.
--Ice formed into balls of various sizes and falling from the thunderstorms of summer are hail.
--Ice pellets form from melting snow crystals falling from the high clouds of winter storms only to refreeze.
--A raindrop falling through sub-zero temperatures will become super cooled and turn to ice on impact.
-- A raindrop falling far enough through sub-zero temperatures is super cooled before turning into an ice pellet.
--Super-cooled rain is the most dangerous flight condition possible. Don't takeoff if ice pellets hit the ground.
--In unstable conditions any air once rising will continue to rise.
--Warmer air above colder air is an inversion with stable characteristics.
--The two ways high humidity gives instability are 1. The air is lighter; 2. Lighter air rises.
--The less humid the air the less likely it is to rise.
--Rising air cools until condensing into droplets that release heat that increases the rising tendency.
--A microburst is a wet or dry strong downdraft form of windshear of relatively small diameter and life.
--Other forms of wind shear occur at all altitudes horizontally or vertically at all speeds.
Preparation and Knowledge
--The cold weather section of the POH is your bible specific to the aircraft.
--Learn about the need for a winterization kit, cold weather oil and fuel.
--A low battery will freeze
--Don't charge an aircraft battery with an automotive charger. 3-4 amp charge rate required.
--Tire pressures and control cables need to be prepared for cold weather operations.
--Wax the exterior of your aircraft before ice forms.
--Contact the manufacturer or type club for winter information
--Check the carbon monoxide reading of the aircraft heater before first winter use and thereafter.
--Any water in the fuel will freeze when cold enough. Testing for water will not work if the water is frozen.
--Don't fly into cold conditions without being prepared to walk part way.
--Weather decision making is a critical skill in cold weather.
--The preflight should not be shorter because it is cold. If anything, the preflight should be longer.
--A normal preflight cannot detect an iced pitot tube. Apply pitot heat during preflight and prior to takeoff.
--Make your flight visibility decisions early if it appears to be slowly deteriorating.
--CFIT accidents mostly occur in cold weather conditions.
--Water's three forms are vapor, liquid and solid
--When more molecules are leaving a liquid surface than are arriving you have evaporation.
--When more molecules are arriving to a liquid surface than are leaving you have condensation.
--Saturation depends more on temperature of the cloud droplets than on the temperature of the near by air.
---I'm firmly in the camp that there is no way, no how any IFR pilot who really flys IFR on a regular bases can go through his entire career without hitting ice where its not suppose to be. The skill is in keeping yourself in a position to get out of it.
The best rule is never to takeoff with frost on the aircraft. However, if the pilot is convinced it is not a hazard the takeoff may be legal. The legality is determined by the success of the takeoff. (FAR91.209. "No pilot may take off an airplane that has…any frost adhering to the wings, or stabilizing or control surfaces, unless that frost has been polished to make it smooth." l…prohibits flight with frost on a propeller, windshield, power plant and certain instrument systems. Thus, legality depends on FAA interpretations.
--.8mm of smooth ice on a wing reduces lift 25% just imagine what a frosted surface does.
Flying in the Weather
---Use your windows
---Fly where it looks best
---Don’t fly at all.
---Get all available radar information
---Have an escape route.
---The most conservative decision is seldom wrong.
Weather Survival 101
Avoid bad weather, or you must believe your instruments, maintain your airspeed and practice making a 180-degree instrument turn using just instruments under the hood.
Events related to VFR
flight into Sierras
Plan is to file VFR to Truckee with intention to make return to CCR when student becomes uncomfortable with situation.
Weather forecast was for 25 knot winds and turbulence. Kept most aircraft out of route.
Determining cloud levels from local ATIS, AWOS. ASOS and aircraft base reports.
Giving Base reports to ATC en route. Low clouds overcast to broken. No rain.
Option of climbing through large holes to on top above 10,000. Freezing
level at 14,000.
On top requires ability to descend at destination. Have FSS phone to get destination weather.
ifr (I Follow roads) route
Lost radar contact but keeping radio contact.
Below clouds requires you remain at least 500’ below unless within 1200’ of surface
Staying to right side of freeway when flying ifr route.
Actual weather low ceilings but no turbulence and good visibility. Maintaining VFR
Why not land at Blue Canyon? High velocity crosswinds.
Next time make low approach.
Make 180 at Blue Canyon and contact Reno Radio to amend flight plan of early return to CCR.
At Auburn we get back on flight following. Cancel flight plan to CCR
Uncertainty as to flight plan actually modified.
Make a diversion to refuel on less expensive gas
Presence of Jets climbing and descending in vicinity of Sacramento.
Maintaining elevation in rising terrain below cloud bases
Locating airports along route
Not locating smaller airports along route
Sizes of airports, altitude of airports
VFR locations of places along I-80
Emergency landing options
Closing Flight plan
Diversion to Kingdom (Lodi) for fuel
No receipt and faulty grounding wire.
Finding altitude to get CCR ATIS
VFR LDA into CCR
Problem of winds changing in direction and velocity on approach is common
Short final changing runways. Sidestep.
Taxiing to hangar shortest way
Return to whittsflying
Continued on 5.539 Cold Weather Flying