PART 61KSNSGROUND SCHOOL
North Aero NORTH AERO

Phase 4 · Module 4-3

Checkride Week 3: Task C

Task C of the checkride is Weather Information, in Area of Operation I, Preflight Preparation. It is the largest Task in that Area. The four knowledge elements cover four subjects, and the evaluator takes them in order:

The objective names what the evaluator measures: "To determine the applicant exhibits satisfactory knowledge, risk management, and skills associated with weather information for a flight under VFR" . Two Notes apply to the evaluator. "If K2 is selected, the evaluator must assess the applicant's knowledge of at least three sub-elements." The second Note says the same about K3.

The sub-elements set the size of Task C. K2 lists seven weather products. K3 lists twelve meteorological conditions. R1 and R2 each have three sub-elements. PA.I.C.S2 tells the applicant to "Analyze the implications of at least three of the conditions listed in K3a through K3l, using actual weather or weather conditions provided by the evaluator" .

Task C lists these references :

The Aviation Weather Handbook is the source for most Task C answers. It replaced five advisory circulars in 2022, and it now contains the observation formats, the forecast formats, and the meteorology in one document.

Three skill elements complete the Task. PA.I.C.S1 is obtaining an adequate briefing from available resources. PA.I.C.S2 is analyzing three of the twelve K3 conditions. PA.I.C.S3 is correlating the weather information into a go/no-go decision. The evaluator gives the scenario for S2 and S3.

Two official sources give weather to a pilot. The Aviation Weather Center at aviationweather.gov publishes the products. Flight Service at 1800wxbrief.com, or 1-800-WX-BRIEF by telephone, delivers briefings . The AIM names both as FAA weather services .

The AIM describes the Flight Service program as the one that "serves the weather needs of pilots through its flight service stations (FSS)", reached at www.1800wxbrief.com or at 1-800-WX-BRIEF . It also says where the observations come from. "Airport observations (METAR and SPECI) in the U.S. are provided by automated observing systems", with human oversight and augmentation at select larger airports.

The division of labor is a K1 answer the evaluator listens for:

A self-briefing from official sources complies with the regulation. The AIM states it plainly: "Pilots can receive a regulatory compliant briefing without contacting Flight Service" . A telephone call to a briefer is one way to meet the requirement. It is not the only way, and the evaluator accepts a documented self-briefing as an answer to K1.

14 CFR 91.103 is the regulation for the whole Task. It says the pilot in command "shall, before beginning a flight, become familiar with all available information concerning that flight" . Paragraph (a) names weather reports and forecasts for a flight not in the vicinity of an airport. Reports and forecasts are both required, and the word between them is "and". A PIC who read the METAR and skipped the TAF read half of what 91.103(a) names.

A standard briefing is the complete weather summary for a flight. The AIM tells the pilot to request one "any time you are planning a flight and you have not received a previous briefing or have not received preliminary information through online resources" . It applies to any flight, and the pilot requests it closest to departure time.

An abbreviated briefing serves the pilot who needs "information to supplement mass disseminated data, update a previous briefing, or when you need only one or two specific items" . It supplements a standard briefing and never replaces one. The pilot who asks for an abbreviated briefing gives the briefer the time and the source of the earlier information. The briefer then knows what to update.

An outlook briefing applies when departure is six or more hours away. The AIM restricts its use to "planning purposes only" . AC 91-92 says the same and gives the reason. A forecast at that range is too uncertain for a departure decision .

An outlook briefing is never a departure briefing. The pilot who takes an outlook briefing the night before gets a standard briefing near departure time the next day. Weather changes overnight, and the outlook briefing does not record the change.

A briefing needs seven inputs from the pilot :

The adverse conditions element comes first in a briefing. The AIM names what belongs in it. It is the "significant meteorological and/or aeronautical information that might influence the pilot to alter or cancel the proposed flight", and the AIM tells pilots to be "especially alert for current or forecast weather that could reduce flight minimums below VFR or IFR conditions" . It adds a second alert, for "any reported or forecast icing if the aircraft is not certified for operating in icing conditions".

A time limit applies to the current conditions element in a standard briefing. The AIM says it "will be omitted if the proposed time of departure is beyond 2 hours, unless the information is specifically requested by the pilot" . A pilot who calls three hours early and does not ask gets no current conditions.

A briefing is weather plus aeronautical information. NOTAMs and temporary flight restrictions are part of it . A cloudless day is still a no-go when the destination runway is closed or a temporary flight restriction covers the route. The evaluator can ask what makes a flight illegal on a clear day, and the answer is in the aeronautical information.

The self-brief follows a fixed order, and AC 91-92 sets it :

The pilot then compares the briefing to personal minimums, decides, and records the decision.

The briefing covers stations along the whole route. Two endpoint METARs describe two airports and say nothing about the 80 miles between them. No terminal product forecasts the weather in the en route segment.

Three inflight weather sources exist today. Flight Service answers on 122.2 and on published remote frequencies. Flight Information Service-Broadcast sends products to the flight deck over the 978 MHz universal access transceiver . Air route traffic control centers broadcast hazardous weather advisories on their own frequencies.

The center broadcast contains an alert and not the text. The AIM says centers broadcast "a Convective SIGMET, SIGMET, AIRMET (except in the contiguous U.S.), Urgent Pilot Report, or CWA alert once on all frequencies", and that the broadcasts advise pilots "to contact the nearest flight service facility for additional details" . The controller tells the pilot an advisory exists. The pilot asks for the content.

Flight Watch and the Hazardous Inflight Weather Advisory Service no longer exist. Neither appears in the current AIM. Study material that still teaches a call to Flight Watch on 122.0 is out of date. An applicant who names 122.0 to an evaluator names a withdrawn frequency.

Nothing available in flight replaces the preflight briefing. FIS-B updates the weather information the pilot obtained on the ground. It does not provide a preflight briefing.

The AIM states the limit twice. Flight Information Services are "not intended to replace traditional pilot and controller/flight service specialist/aircraft dispatcher preflight briefings or inflight voice communications", and the AIM adds that FIS "should never be used in lieu of an individual preflight weather and flight planning briefing" .

A METAR is an observation of the conditions at a station. The Aviation Handbook calls METARs "hourly" reports "since they are routinely produced near the top of the hour" . A METAR reports past conditions, and it forecasts nothing. It contains these elements:

A SPECI is an unscheduled report. The handbook defines it as a report "taken when any of the criteria given in Table 24-2 are observed during the period between hourly reports" . A SPECI contains the same elements a METAR contains. Its existence is itself information, because a station issues one when a condition changes quickly.

The wind group has five digits and the letters KT. The direction is the first three digits, coded "in tens of degrees relative to true north" . The speed follows in two digits. A G and two more digits mark gusts, so 27020G35KT is a west wind at 20 knots gusting to 35. VRB replaces the direction when the wind is light and variable. The code for a calm wind is 00000KT.

METAR visibility is in statute miles. The handbook codes a visibility of one and a half miles as "1 1/2SM", with a space between the whole number and the fraction . The group ends with SM, which names the unit.

Present weather has an intensity, then a descriptor, then a type. The three intensities are light, moderate, and heavy . A minus sign codes light, no sign codes moderate, and a plus sign codes heavy. The letter pairs are:

The intensity attaches to the precipitation and not to the thunderstorm. +TSRA is a thunderstorm with heavy rain, and -RA is light rain.

Sky condition reports cloud cover in eighths. FEW covers one to two eighths, SCT three to four, BKN five to seven, and OVC eight. The height follows in three digits and the handbook records it "in feet AGL" . BKN012 is a broken layer at 1,200 feet above the ground.

The ceiling is "the lowest layer aloft reported as broken or overcast" . Scattered is not a ceiling. A sky reported FEW008 SCT015 BKN040 has a ceiling of 4,000 feet, and the two lower layers do not change that number. Where the sky is totally obscured, vertical visibility becomes the ceiling, and the handbook calls it an "indefinite ceiling".

Temperature and dewpoint are "coded as two digits rounded to the nearest whole degree Celsius" . An M prefix marks a value below zero, so 04/M02 is four degrees with a dewpoint of minus two.

A spread that closes across successive METARs predicts fog. Three hourly observations on a clear, calm evening show the trend. A spread of six degrees, then four, then two, shows air that approaches saturation at the surface. The fog that forms before dawn is predictable from that sequence.

The altimeter group starts with an A and gives inches of mercury without the decimal point, so A2992 is 29.92 inHg . The pilot sets it before flight, and a correctly set altimeter then reads field elevation on the ground.

Remarks include the automation code. The handbook says "AO1 or AO2 is coded in all METARs/SPECIs from automated stations", and that a station with a precipitation discriminator is AO2 while one without is AO1 . AO2 distinguishes rain from snow. Neither station detects a thunderstorm on the far side of the field. A human observer does, and an automated report describes one point.

A PIREP is the only direct observation of conditions aloft. The other products in Task C describe the air above the ground by inference, by model, or by radar return. A PIREP describes it because a pilot flew through it. The two message types are Urgent, coded UUA, and Routine, coded UA .

The decode uses slash codes:

Each report of ice or turbulence includes the aircraft type. The handbook requires it: "Icing and turbulence reports always include aircraft type" . Moderate turbulence in a Boeing 737 and moderate turbulence in a Warrior describe different conditions. The type lets the reader distinguish them.

The AIM requires air traffic facilities to ask for reports in these conditions :

A controller who asks for a ride report works from that list.

Pilots also volunteer reports. The handbook says a pilot "can report any observation, good or bad", including the case where "conditions were forecasted to occur but not encountered" . The AIM adds what the National Weather Service does with them, which is to "verify or amend conditions contained in aviation forecast and advisories" . A negative report improves the next forecast as much as a positive one.

A Terminal Aerodrome Forecast covers the area within five statute miles of the airport. It is a terminal product, and it says nothing about the en route segment. A pilot who reads two TAFs for a 150 mile flight has forecasts for the first five miles and the last five.

Scheduled TAFs issue four times a day on the six-hour cycle, at 0000, 0600, 1200, and 1800 UTC. The standard valid period is 24 hours, and some airports have 30 hours.

The groups read as day and hour in Zulu time. The header gives the issuance time and then the validity window as ddhh/ddhh. A TAF reading 121120Z 1212/1312 was issued on the 12th at 1120 Zulu. It is valid from 1200 Zulu on the 12th to 1200 Zulu on the 13th.

The handbook spells the header out digit by digit. "The first two digits (Y1Y1) are the day of the month for the start of the TAF. The next two digits (G1G1) are the starting hour (UTC). Y2Y2 is the day of the month for the end of the TAF, and the last two digits (G2G2) are the ending hour" .

An evaluator can hand over a TAF and ask for the valid period before asking for anything else. The answer is two dates and two times, and it comes from the header rather than from the body.

The body reads in the same order each time. The order is wind, visibility, present weather, and sky condition. Each change group restates the changed elements. The TAF names one cloud type. The handbook says "the only cloud type included in the TAF is CB", and CB follows the cloud height without a space "whenever thunderstorms are included in the significant weather group", including forecast thunderstorms in the vicinity . A CB in the arrival window forecasts a thunderstorm, and the word thunderstorm does not appear.

Three change indicators appear in an NWS TAF. The handbook names them: "The forecast change indicators FM, TEMPO, and PROB are used when a change in any or all of the forecast elements is expected" .

BECMG marks a gradual change spread across the stated window, and it does not appear in the NWS format. It appears in the TAFs for joint-use civilian and military airports, which differ from the NWS format in several ways . A pilot reading a TAF for a joint-use field meets it there.

FM starts a new forecast line. Everything after it replaces everything before it until the next change group. TEMPO does not replace the prevailing condition, and the prevailing condition returns between the fluctuations.

PROB30 states a low probability of a real condition. A PROB30 thunderstorm group in the arrival window is not a reason to cancel by itself. It is a reason to carry more fuel and to name an alternate.

The handbook gives probabilities for two of the three. TEMPO covers fluctuations that "have a high percentage (greater than 50 percent) probability of occurrence", last "one hour or less in each instance", and "in the aggregate, cover less than half of the period" . PROB30 marks "a low-probability occurrence (30 percent chance) of a thunderstorm or precipitation event".

An amended TAF supersedes and cancels the one before it the moment it issues . The handbook gives the trigger: TAFs "are amended whenever they become, in the forecaster's judgment, unrepresentative of existing or expected conditions" . Planning never continues on the superseded forecast. A pilot who read a TAF two hours ago and did not check for TAF AMD plans on a withdrawn forecast.

The Surface Analysis Chart displays the surface observations. The handbook calls it "an analyzed chart of surface weather observations", showing sea level pressure as isobars along with "the positions of highs, lows, ridges, and troughs, and the location and character of fronts" . The Weather Prediction Center issues it eight times a day, valid at 00, 03, 06, 09, 12, 15, 18, and 21 UTC.

The Surface Analysis Chart is an analysis and not a forecast. It shows where the front is now.

The Short-Range Surface Prog Charts show where the front will be. They depict "surface pressure systems, fronts, and precipitation for a multiday period", divided into forecast valid time periods, and each chart shows the elements expected at its valid time . The two charts together show the movement, and the go/no-go decision depends on movement.

The Graphical Forecasts for Aviation tool replaced the text Area Forecast over the contiguous United States. It is "a set of web-based displays intended to provide the necessary aviation weather information to give users a complete picture of the weather that may impact their flight operations" . The pilot selects the valid time and the field, and reads ceiling, visibility, clouds, precipitation, winds, and icing off the map.

The handbook states one caution about the GFA tool. Users "can turn on and turn off certain functions", and the handbook warns that turning an overlay off "can lead to hidden areas of hazardous weather for a given flightpath" . A GFA with the SIGMET overlay switched off shows a cleaner map and the same weather.

The FB forecast gives wind direction in tens of degrees true, wind speed in knots, and temperature in Celsius . A group reading 2420-04 forecasts a wind from 240 degrees true at 20 knots with a temperature of minus four.

Two blanks in the table follow issuance rules. The handbook states them as issuance limits: "Wind forecasts are not issued for altitudes within 1,500 ft of a location's elevation. Temperature forecasts are not issued for altitudes within 2,500 ft of a location's elevation" . The table gives no 6,000 foot wind and no 6,000 foot temperature for a station at 4,500 feet.

The code 9900 means light and variable. The handbook defines it as "light and variable wind or wind speeds of less than 5 kt" .

Two more encodings appear at altitudes a trainer does not reach, and an evaluator can still ask. For forecast speeds of 100 through 199 knots, the code adds 50 to the direction digits and subtracts 100 from the speed. A wind of 250 degrees at 145 knots encodes as 7545 . The handbook also notes that "amendments are not issued to the forecasts", so an FB table does not update between its four daily issuances.

Winds aloft have two uses, a navigation log and a shear warning. The briefing provides them "in knots and tens of degrees and referenced to true north", interpolated to the planned altitude, and heights are MSL . A forecast of 35 knots at 3,000 feet over a calm surface describes a large change across a small vertical distance. The climb and the descent cross that change, and the airplane encounters shear and turbulence there.

The Storm Prediction Center grades convective risk in six steps. The handbook names five risk areas, "marginal risk (MRGL), slight risk (SLGT), enhanced risk (ENH), moderate risk (MDT), or high risk (HIGH) of severe weather based on a percentage probability", and adds that the day one through day three outlooks "also depict areas of general thunderstorms (TSTM)" . TSTM is the outlook's non-severe category, and the Storm Prediction Center defines it as an area where "a 10% or greater probability of thunderstorms is forecast during the valid period" .

A private pilot in a Warrior treats TSTM as a real forecast. The severe categories grade the risk to property and to life on the ground. TSTM already describes air the airplane cannot fly through.

An AIRMET is "a concise description of the occurrence or expected occurrence of specified en route weather phenomena which may affect the safety of aircraft operations" . The handbook names the audience directly. AIRMETs "are intended to inform all pilots, especially VFR pilots and operators of sensitive aircraft".

Three AIRMET categories exist, and each has its own name :

AIRMETs issue four times a day in the contiguous United States and three times a day in Alaska.

The graphical form is the one a pilot actually reads. AIRMETs over the contiguous United States appear as graphics on aviationweather.gov and 1800wxbrief.com and on equipment receiving FIS-B, and they "provide a higher forecast resolution than AIRMETs issued in text format" . They are valid at discrete times no more than three hours apart, out to 12 hours, with the 00-hour forecast representing the initial conditions. The forecasts valid at 00 through 06 hours correspond to the text bulletin.

A SIGMET warns of conditions severe for each airplane. The handbook lists these criteria :

A SIGMET is unscheduled, and it issues when the criteria occur or are expected within a four-hour period. Its valid period cannot exceed four hours.

A separate product covers thunderstorms. The handbook says "Convective SIGMETs are issued for the CONUS instead of SIGMETs for thunderstorms" . The criteria are three, and any one of them triggers the product:

The Convective SIGMET's shape matters as much as its text. The handbook calls the polygon "a 'snapshot' that outlines the area (or line) of thunderstorms at the issuance time of 55 minutes past each hour" . The storms move after the issuance time, so the polygon is a position report and not a boundary.

A center weather advisory is the fourth product of this type, and it applies where the others do not. The handbook describes it as "a concise description of the occurrence or expected occurrence of specified weather phenomena that meet or approach in-flight advisory" criteria, issued "when there is no existing in-flight advisory" from the Aviation Weather Center . A CWA is valid for up to two hours. The Malbis briefing included one for the northern half of the route.

A Convective SIGMET implies three hazards it does not name. "Any Convective SIGMET implies severe or greater turbulence, severe icing, and LLWS" . The bulletin does not need to say turbulence for turbulence to be forecast. A Convective SIGMET on the route forecasts severe turbulence, severe icing, and low-level wind shear by its own existence. A Warrior is certified for none of the three.

On July 28, 2020, a 64-year-old private pilot flew his wife from Gulf Shores, Alabama, toward Muscle Shoals. He had 946 hours and no instrument rating. Sixteen minutes after takeoff the airplane entered a decreasing radius left turn at 5,800 feet, descended to 1,275 feet, and struck trees. Both died. Two hours and thirty minutes before takeoff, a Flight Service briefer told him twice that VFR flight was not recommended .

The destination was 267 nautical miles away. The pilot had a business meeting near Muscle Shoals the next day. The airplane was a 1974 Beech F33A with an electronic primary flight display, and the display included a synthetic vision function.

At 1615 the pilot called Flight Service and asked about two departure times, that afternoon and the following day. For the following day the briefer said "it doesn't look good", naming thunderstorms, rain showers, low ceilings, and reduced visibility. For that afternoon the briefer said "That's not looking so good right now". A convective SIGMET covered the southern portion of the route. A center weather advisory covered the northern portion for developing thunderstorms. The briefer said VFR flight was not recommended .

The pilot answered with the surface observations. "It looks like my best shot is, I'm gonna probably go this afternoon because its going to be worse tomorrow…what I'm seeing… reported… online anyway is that everything is VFR as we speak … are you seeing anything… between here and Muscle Shoals that's not VFR?"

The briefer answered the question the pilot asked and then answered the one he did not. He reported clouds "between 1,200 and 2,000 feet" in multiple layers. Nobody reported instrument conditions. He then added a qualifier: "You get into the areas where the precipitation is, and it could be IFR."

The pilot restated his decision rule. "If I'm going VFR I'm going this afternoon, unless I got clouds that are getting low enough that I can't fly… and I haven't heard anything to tell me that."

The briefer then read him an observation from Mobile, Alabama, 25 miles west of the route. Visibility there was 1.5 miles in heavy rain and mist. The briefer said areas along the route with rain showers or thunderstorms could drop to instrument conditions, as Mobile had. The two discussed where the precipitation was and where the convective SIGMETs covered, and the call ended.

The pilot and his wife reached the fixed base operator between 1630 and 1700 and stayed about an hour. He kept checking weather in the flight planning room and on a lobby monitor showing FlightAware radar. About 1800 he telephoned a family member, said he was unsure about departing, and discussed coming back to the house for dinner. Fifteen to twenty minutes later he called again and said "they had a window and were leaving after all".

The airplane departed at 1845 and turned north. The pilot contacted Pensacola approach control, asked for VFR flight following, and gave 3,000 feet as his altitude. At 1854 he turned left about 90 degrees to the west and descended from 3,200 feet to 2,500 feet. A witness half a mile from that turn heard an engine sound like the one "when crop dusters dive". She looked for the airplane and could not find it, because the "cloud cover was just too thick" and the "vertical visibility was very low".

At 1854:17 a controller asked, "Do you need any help on that that cell off to your north there? Looks like you took uh pretty harsh westbound turn." The pilot did not answer. Thirty seconds later the controller said ten miles westbound would put him "clear of all that weather". The pilot did not answer.

A second controller took the handoff as the airplane turned back north and asked the pilot his intentions. The pilot answered, "right now I'm trying to get through [unintelligible] clouds here." The controller offered five or six miles west to "get you in to less precip". The pilot acknowledged and continued north. At 1856:25 the controller reported an area of "heavy to extreme precipitation" ten miles across, five miles north of him. The pilot did not answer.

The airplane climbed to about 5,200 feet and flew about five miles north. Then it began a decreasing radius 360 degree left turn, climbing from 5,000 to 5,800 feet and returning to 5,000. Over the next two minutes the track became erratic. The altitude fell from 5,000 feet to 1,275 feet and the groundspeed varied between 150 and 34 knots. At 1900:23 the pilot transmitted a partial callsign and said nothing more.

At 1855, five minutes before the accident, an airport 18 nautical miles southwest of the crash site reported its observation. The overcast was at 1,200 feet and the visibility one half statute mile in heavy rain. The temperature was 23 degrees Celsius over a dewpoint of 22, and the wind was calm .

The examination found flight control continuity and no engine anomaly except a left magneto that produced no spark on test. The probable cause reads: "The noninstrument-rated pilot's decision to depart in deteriorating weather conditions, which led to restricted visibility and the pilot's loss of airplane control due to spatial disorientation." The report adds a contributing factor: "Contributing to the pilot's poor decision-making was self-induced pressure" .

Each product the pilot needed existed before he took off, and the report lists them. A convective SIGMET valid at 1900 covered the route and warned of instrument conditions, heavy precipitation, and severe turbulence. The Graphical Forecasts for Aviation forecast VFR surface visibilities along the route. The same GFA forecast a 30 to 60 percent chance of rain showers over most of the route. It forecast a 30 to 50 percent chance of thunderstorms there .

Those two GFA statements are both true, and they describe different things. Surface visibility describes the air at the field. Convective probability describes the air the airplane flies through. The pilot read the first and made his decision on it.

The upper air sounding for the time and place showed clouds from 1,500 to 14,000 feet. It showed low-level wind shear from the surface to 1,500 feet. Infrared satellite data showed cloud tops near 41,000 feet. Tops at 41,000 feet describe a deep unstable atmosphere with enough moisture and enough lift to build a mature thunderstorm.

The pilot's sentence to the briefer states a decision rule, and the rule is the error. "If I'm going VFR I'm going this afternoon, unless I got clouds that are getting low enough that I can't fly." The rule tests ceiling and nothing else. It does not test visibility, convection, turbulence, the trend, or the difference between a report and a forecast. The weather that killed him was visibility inside heavy rain, and his rule had no term for it.

Five actions would each have broken the chain:

The last of those five actions came 5 minutes 45 seconds before the last radio call. The airplane had fuel, control, and an engine. The pilot did not change the plan.

Self-induced pressure is in the probable cause because the pilot had a meeting the next morning. The pressure did not come from the weather, the airplane, or the passenger. The pilot supplied it himself, and he acted against the briefer, the controller, and the Mobile observation.

Air pressure comes from molecules striking a surface. The handbook describes atoms and molecules "always moving in random directions" that "exert pressure" when they strike, and adds that "as the density of the air increases, the number of strikes per unit of time and area also increases" . The number of strikes sets the pressure, and density sets the number of strikes.

Three properties set the density of a parcel. The handbook names them as mass, pressure, and temperature, and names water vapor as the third practical factor for a pilot . Pressure, temperature, and humidity are the three an evaluator asks for.

Warm air is less dense than cool air. The handbook states the relation directly: "an air parcel with a higher temperature is less dense than an air parcel with a lower temperature", "because the warmer air occupies a large volume" .

Humid air is less dense than dry air. The handbook gives the reason: "dry air molecules have a larger mass (weight) than water vapor molecules, and density is directly related to mass" . Each water molecule that enters a parcel displaces a heavier nitrogen or oxygen molecule.

Any one of high, hot, or humid raises density altitude. All three are not required, and the evaluator listens for that answer. A cold day at a high field still has air of low density. A hot humid day at sea level can produce a density altitude thousands of feet above the field.

The atmosphere is about 78 percent nitrogen and 21 percent oxygen . The remaining 1 percent is argon, carbon dioxide, and other gases, and the amount of water vapor varies. Almost all weather happens in the troposphere, the lowest layer, which the handbook puts at "about 11 kilometers (km) (36,000 ft) high" .

Temperature normally falls with height. The standard rate is 6.5 degrees Celsius per kilometer, which the handbook also gives as 3.57 degrees Fahrenheit per 1,000 feet . In the units a pilot uses, that rate is about 2 degrees Celsius per 1,000 feet. The handbook adds that the value "is an average, the exact value seldom exists", and that temperature in the troposphere "sometimes remains constant or even increases with height".

Rising air cools without losing heat to anything. The handbook explains the mechanism: a rising parcel "moves into an area of lower pressure", so "the parcel expands", and expansion "takes heat away from the parcel, so the air cools as it rises" . No heat leaves the parcel. The cooling comes from the work of expanding. That process forms each cloud.

Sinking air reverses the process. Compression warms the parcel, the temperature rises away from the dewpoint, and the relative humidity falls. Descending air becomes drier, and clouds in descending air evaporate.

The dry adiabatic lapse rate is "approximately 3°C per 1,000 ft" for a rising unsaturated parcel . The moist adiabatic lapse rate is smaller, and the handbook gives the range as "approximately 1.2°C per 1,000 ft (4°C per km) for very warm saturated parcels to 3°C per 1,000 ft (9.8°C per km) for very cold saturated parcels" . A saturated parcel cools more slowly because condensation releases latent heat inside it.

The environmental lapse rate is a different quantity from both rates. A sounding measures the temperature of the actual air at each height . The adiabatic rates describe what a parcel does. The environmental rate describes the air around the parcel. Stability is the comparison between the two quantities.

Stability is the atmosphere's resistance to vertical motion. The handbook defines it as "the property of the ambient air that either enhances or suppresses vertical motion of air parcels", and adds that it "determines which type of clouds and precipitation a pilot will encounter" . Stability is not a measure of how rough the air is. It is a measure of whether air that starts rising keeps rising.

The parcel test decides stability, and the handbook states all three outcomes :

An inversion is "a layer in which the temperature increases with altitude" . It marks strongly stable air, and the handbook says so: "The principal characteristic of an inversion layer is its marked stability". A surface-based inversion forms over land on clear nights with light wind, because the ground radiates heat away faster than the air above it.

Haze, smoke, and dust cannot rise through a stable layer, so they collect beneath the base of an inversion. The air below an inversion is smooth, and the visibility in it is poor.

A pilot identifies stability from the flight conditions and the cloud forms. Stable air gives smooth flight, stratiform cloud, steady precipitation, and poor visibility. Unstable air gives turbulence, cumuliform cloud, showery precipitation, and good visibility. Smooth air and good visibility do not occur in the same air mass.

A stagnant high-pressure system can produce poor visibility for days. Sinking air under a high forms an inversion, and the inversion traps the haze. A large high on the surface chart can therefore cover an area with visibility too low for VFR flight.

Uneven heating of the Earth's surface causes all weather. The sun heats the equator more than the poles, land more than water, and dark ground more than light ground. Each pressure difference, each wind, and each front results from that unequal heating.

Land heats and cools faster than water. Water has a high heat capacity and it mixes, so a lake changes temperature slowly while the field beside it changes in an hour.

The sea breeze blows during the day. Land heats faster, the air above it rises, and cooler air flows inland off the water to replace it . The sea breeze front is a convergence line, and cumulus cloud often forms along it.

The land breeze blows at night in the opposite direction. Land cools faster, the water stays warmer, air rises over the water, and the surface flow runs from the land out to sea .

The handbook says minimum surface air temperature "usually occurs shortly after sunrise", and that temperature variation "is maximized over land, at low latitudes, with a clear sky, dry air, and light wind" . The variation is smallest over water, under a cloudy sky, in moist air, and with strong wind.

Clear, calm nights produce two conditions at once. The ground radiates heat to space with no cloud to return it, which forms a surface-based inversion . The same cooling lowers the surface temperature toward the dewpoint. A clear, calm, moist night produces radiation fog by dawn, and the METAR sequence the evening before shows the spread closing.

Wind is air moving from high pressure toward low pressure. The handbook names the cause: "Wind is driven by pressure differences, which create a force called the PGF", and that force "makes the wind blow in an attempt to equalize pressure differences" . With no other force acting, air would flow straight down the gradient.

Coriolis force turns the moving air. In the Northern Hemisphere it deflects moving air to the right of its path . It acts only on air already in motion, and its strength increases with speed.

Above the friction layer the two forces balance. The result is wind blowing roughly parallel to the isobars rather than across them . Near the surface, friction slows the air, which weakens Coriolis force, and the wind then angles across the isobars toward the low .

The surface wind and the wind at 3,000 feet come from different directions. The surface wind is the slower of the two winds, and it crosses the isobars at a larger angle.

Circulation follows from the same two forces. Air turns clockwise and outward around a high in the Northern Hemisphere, and counterclockwise and inward around a low. Outflow at the surface of a high requires air to sink into it from above, and that sinking air warms and dries. Inflow at the surface of a low requires air to rise out of it, and that rising air cools and condenses. A high therefore produces fair weather, and a low produces cloud.

Isobar spacing measures the gradient. Closely spaced isobars mean a steep pressure gradient and strong wind, and widely spaced isobars mean light wind. A pilot therefore estimates the wind speed from the Surface Analysis Chart before opening any wind product.

Mountain waves form when strong wind crosses a ridge into stable air. The handbook describes the conditions as wind of sufficient speed with a component across the ridge, and a stable layer above ridge height . The handbook states that "if the wind is sufficiently strong and the surrounding atmosphere is stable, a wave will develop" .

The handbook says a rotor zone commonly develops "near or below ridge level on the downwind side of the mountain, under a wave crest and associated lenticular cloud", and calls it "an area of potentially severe-to-extreme wind shear and turbulence" . That altitude is the traffic pattern altitude at a mountain airport.

A mountain wave has a visual marker, and the marker is not always present. The handbook describes "sharp-edged, lens-shaped (or almond-shaped) lenticular clouds" as the most distinctive sign, and adds that "extremely severe wind events can occur with little or no visual warning of their presence" . A dry mountain wave produces no cloud.

Wind shear can occur at any altitude and in any direction. The handbook defines it as "the sudden, drastic change in wind speed and/or direction over a small area, from one level or point to another, usually in the vertical", and states that it "can affect any flight at any altitude" . Thunderstorms are one source among several, and an applicant who names only thunderstorms gives an incomplete answer to K3b.

Four common sources produce low-level shear:

A shear that removes the headwind on final approach reduces the indicated airspeed immediately. The airplane holds its groundspeed for a moment while the air around it slows, so the indicated airspeed falls. The airplane is low, slow, and configured to land when that loss occurs.

Dewpoint is a temperature. The handbook defines it as "the temperature an air parcel must be cooled at constant pressure and constant water vapor pressure to allow the water vapor in the parcel to condense into water" . Dewpoint reports "the actual quantity of water vapor in the parcel".

The spread is the difference between the two temperatures the METAR gives. The handbook names it the dewpoint depression and says that "as the spread decreases, relative humidity increases", and that at zero spread "relative humidity is 100 percent, and the air parcel is saturated" . The spread predicts fog at the surface, cloud bases aloft, and the altitudes where structural ice becomes possible.

Relative humidity changes when temperature changes even if the moisture does not. A parcel at 30 degrees Celsius holding 8 grams of water vapor is at 30 percent relative humidity. The same parcel at 20 degrees has a relative humidity of 53 percent with no water added . Dewpoint, not relative humidity, is the quantity a pilot plans with.

Warmer air can contain more water vapor. The handbook states the relation as capacity: "An air parcel's capacity to hold water vapor (at a constant pressure) is directly related to its temperature" .

Condensation releases latent heat, and the release is the energy source of a thunderstorm. The handbook puts an average hurricane at 52 million trillion joules per day, released "as water vapor condenses into clouds and precipitation" . That heat keeps the parcel warmer than its surroundings, which keeps the parcel rising.

Freezing rain at your altitude means warmer air above you. Freezing rain "requires a temperature inversion, which can occur when a warmer air mass overlies a colder air mass", and "normally there is warm air (above 0 °C (32 °F)) above" . A pilot leaves freezing rain by climbing into the warmer air above it. A Warrior that climbs at 500 feet per minute collects ice throughout the climb.

An air mass takes on the properties of the ground below it. The handbook says "the longer the air mass stays over its source region, the more likely it will acquire the properties of the surface below", and that air masses "are classified according to the temperature and moisture properties of their source regions" . Maritime tropical air is warm and wet because it formed over a warm ocean.

A front is a zone, not a line. The handbook calls it "a boundary or transition zone between two air masses" and adds that fronts "have a vertical structure in which the front slopes over the colder (denser) air mass" . The line on the Surface Analysis Chart marks where the sloping surface meets the ground.

Frontal passage produces three changes :

The cold front is steep and fast. The handbook describes dense cold air that "stays close to the ground and acts like a snowplow, sliding under the warmer air and forcing the less dense air aloft", producing "a narrow band of showers and thunderstorms along, or just ahead of, the front if the warm rising air is unstable" . Behind it "the skies usually clear rapidly", leaving gusty wind and colder air.

A squall line can form along or ahead of a fast cold front. The handbook calls it "a continuous line of thunderstorms" and warns that "squall lines present a serious hazard to pilots as squall-type thunderstorms are intense and move quickly" . A light airplane at 110 knots cannot fly around a squall line ahead of a front.

The warm front moves slowly, at "10 to 25 mph", and its gentle slope favors "widespread layered or stratiform cloudiness and precipitation along, and ahead of, the front" . Its weather arrives hundreds of miles before the front reaches the airport.

Clouds lower and thicken in sequence ahead of a warm front. High cirriform cloud arrives first, then middle altostratus, then low stratus and fog at the boundary. The handbook says that before a warm front passes, "cirriform or stratiform clouds, along with fog, can be expected to form along the frontal boundary", with "light to moderate precipitation" "accentuated by poor visibility" . A high thin overcast that lowers through an afternoon marks the arrival of a warm front.

Winter warm fronts produce freezing rain. Rain forms in the warm air that overruns the cold air, falls through the subfreezing layer below, and becomes supercooled . The same gentle slope that produces the layered cloud produces the winter hazard.

A stationary front forms "when the forces of two air masses are relatively equal", and it "influences the local weather for days" . Its weather is "typically a mixture that can be found in both warm and cold fronts". A stationary front across the route is a planning problem for days, not for hours.

An occluded front forms when a faster cold front catches a warm front. The handbook describes the result: "the cold air undercuts the retreating cooler air mass associated with the warm front, further lifting the already rising warm air", and clouds and precipitation occur "along, ahead of, and behind the surface position of an occluded front" . An occluded front has weather on both sides of the line, and neither a cold front nor a warm front does.

The spread predicts the height of a cumulus base. A rising unsaturated parcel cools 3 degrees Celsius per 1,000 feet while its dewpoint falls about 0.5 degrees per 1,000 feet . The spread therefore closes at about 2.5 degrees per 1,000 feet, and the parcel saturates at the lifted condensation level, where "the temperature-dewpoint spread is zero" . A surface spread of 10 degrees puts the cumulus base near 4,000 feet above the field.

Cloud droplets need a surface to form on. Water vapor condenses onto microscopic particles in cooling air, and the handbook identifies the process as triggered "by the presence of microscopic" nuclei . Clean air can cool past saturation without producing cloud.

Nimbus means rain. The handbook gives the root directly: "Nimbus comes from the Latin word meaning 'rain'", and the clouds carrying the name "bring steady precipitation" . A name containing nimbo or nimbus describes a cloud that produces precipitation.

Cumulus forms indicate instability, and stratus forms indicate stability. A cumulus cloud shows "the vertical motion or thermal uplift of air taking place in the atmosphere", and its flat base marks "the level at which condensation and cloud formation begins" . A layered stratus deck shows air that rose gently and then stopped.

Towering cumulus indicates strong convective turbulence. The Pilot's Handbook states: "Towering cumulus clouds indicate areas of instability in the atmosphere, and the air around and inside them is turbulent" . Towering cumulus is also the first named stage of a thunderstorm cell, so a thunderstorm can follow it.

Turbulence has three causes in the handbook and four names in the cockpit. The handbook says turbulence "is caused by convective currents (called convective turbulence), obstructions in the wind flow (called mechanical turbulence), and wind shear" . Frontal turbulence is a wind shear case, because the wind changes across the frontal boundary. The four names a pilot hears are convective, mechanical, frontal, and shear.

Each cause has a visible or forecastable marker:

The four intensities are defined terms, not impressions. Light "causes slight, erratic changes in altitude and/or attitude". Moderate is "similar to Light but of greater intensity", and the airplane "remains in positive control at all times". Severe "causes large, abrupt changes in altitude and/or attitude" and the airplane "may be momentarily out of control" .

Extreme is the fourth term. The airplane "is violently tossed about and is practically impossible to control", and it "may cause structural damage" .

Severe means momentarily out of control. A pilot who reports severe turbulence reports that the airplane was momentarily uncontrolled. An evaluator asks for the definition of severe because pilots overreport it.

No cloud marks clear air turbulence. The handbook defines it as "sudden severe turbulence occurring in cloudless regions that causes violent buffeting of aircraft", found "normally above 15,000 ft" and "particularly between the core of a jet stream and the surrounding air" . Clear air turbulence occurs above the altitudes a Warrior flies. The handbook adds that CAT "is often encountered unexpectedly and frequently without visual clues to warn pilots of the hazard".

A thunderstorm needs three ingredients. The handbook names them: "sufficient water vapor, unstable air, and a lifting mechanism" . A storm does not form without all three. The lifting mechanisms include:

The life cycle has three stages, and the handbook names them "towering cumulus, mature, and dissipating", with a total life cycle of "typically about 30 minutes" . The towering cumulus stage is the updraft stage. The mature stage begins when precipitation reaches the surface, and the updraft and the downdraft then exist together.

The mature stage is the most violent, and surface precipitation marks its start. A storm that produces rain at the ground is in that stage.

The handbook gives the avoidance rules, and an evaluator can ask for any of them :

A microburst is "a small-scale, intense downdraft" that spreads outward in all directions when it reaches the surface, and the handbook calls it "the most severe type of wind shear" . Its horizontal diameter is under 2.5 miles and it lasts 5 to 15 minutes.

A microburst produces "downdrafts of up to 6,000 fpm" and "headwind losses of 30-90 kt" . A Warrior cannot climb against a downdraft of that speed. Virga at the cloud base or a ring of blowing dust is sometimes the only visible warning.

Structural icing needs two conditions at once. Supercooled liquid water must be present, and the airplane surface must be at or below freezing. The advisory circular states the first condition: "Nearly all aircraft icing occurs in supercooled clouds", where "liquid drops are present at outside air temperatures (OAT) below 0 °C (32 °F)" . Clear air at minus 10 degrees produces no structural ice, because the water is already frozen or absent.

Most icing occurs in a narrow temperature range. The handbook reports that "almost all icing tends to occur in the temperature interval between 0°C and -20°C, with about half of all reports occurring between -8°C and -12°C" . The peak altitude of occurrence is near 10,000 feet.

Clear ice forms from the slow freezing of large drops. The advisory circular describes it as "a glossy, transparent ice formed by the relatively slow freezing of supercooled water", which is "denser, harder, and sometimes more transparent than rime ice" and can form horns . Its transparency is the hazard, because the pilot does not always see it accumulate.

Rime ice forms from the instant freezing of small drops. It is "a rough, milky, opaque ice formed by the instantaneous or very rapid freezing of supercooled drops as they strike the aircraft", and trapped air pockets make it "porous and brittle" . Rime is the most frequently reported icing type, and it builds forward into the airstream off the leading edges .

Freezing rain accumulates ice faster than any other condition. The drops are larger than 200 microns, and the handbook notes that large drops "flow along the airfoil for some distance prior to" freezing . Ice then forms far aft of the protected surfaces .

Carburetor ice is a warm-weather hazard. The Pilot's Handbook says it "is most likely to occur when temperatures are below 70 degrees Fahrenheit (°F) or 21 degrees Celsius (°C) and the relative humidity is above 80 percent", and that "icing can occur even in outside air temperatures as high as" 100 degrees Fahrenheit . A humid summer afternoon at 75 degrees can produce carburetor ice. A dry winter morning at 20 degrees usually does not.

Fog is a cloud at the surface. The handbook defines it as "a visible aggregate of minute water droplets that are based at the Earth's surface", reducing horizontal visibility "to less than 5/8 SM (1 km)" . The handbook states the difference: "Fog differs from a cloud only in that its base must be at the Earth's surface, while clouds are above the surface." The same suspension with visibility between five eighths of a mile and 7 statute miles is mist .

The handbook gives the threshold as a number: "Fog seldom forms when the temperature-dewpoint spread is greater than 2°C (4°F)" . The temperature and dewpoint in each hourly METAR therefore predict fog.

Radiation fog forms over land when radiational cooling reduces the air temperature to or below its dewpoint . The handbook lists three factors that favor it:

Wind speed changes the depth of radiation fog. The handbook says radiation fog "is shallow when wind is calm", that winds up to about 5 knots "tend to deepen the fog by spreading the cooling through a deeper layer", and that stronger winds disperse it or lift it into stratus . It is a nighttime occurrence and it "often does not dissipate until after sunrise".

Advection fog forms "when moist air moves over a colder surface and the subsequent cooling of that air to below its dewpoint" . It is most common along coastal areas and it often moves deep inland. It deepens as wind speed increases up to about 15 knots, and wind stronger than 15 knots lifts it into low stratus or stratocumulus.

Advection fog "is usually more extensive and much more persistent than radiation fog", and it "can move in rapidly regardless of the time of day or night" . It can remain over the water for weeks, and it advances over the land at night and retreats the next morning. A coastal airport that reports clear at 1800 can report a quarter mile at 2200.

Upslope fog forms when moist stable air moves up sloping terrain and cools adiabatically . It needs wind, like advection fog, and it persists while the flow persists.

Precipitation-induced fog forms under a front. Rain from the warm air above falls into the colder air below, evaporates, and saturates it . It is common ahead of a warm front, and it arrives with the steady rain rather than after it.

Frost forms by deposition. The handbook defines the process as "the phase transition by which vapor (a gas) is changed into a solid without passing through the liquid phase" . Frost forms on clear, cold nights when the surface temperature falls below both freezing and the dewpoint. Clear, calm, dry nights over land cool the most, because the handbook puts maximum diurnal temperature variation "over land, at low latitudes, with a clear sky, dry air, and light wind" .

All frost, snow, and ice come off the airplane before flight. The advisory circular gives the instruction and the reason. Remove "all frost, snow, and ice from the aircraft surfaces because even very small amounts may adversely affect the aerodynamic properties of a wing" . Frost does not change the shape of the wing. It roughens the surface, which disrupts the airflow and reduces lift while it increases drag. A thin, even coat of frost has that effect.

Obstructions to visibility are worst in stable air. The handbook says "haze occurs in stable air", that a layer is "usually only a few thousand feet thick but may extend upwards to 15,000 ft", and that a haze layer "has a definite ceiling above which in-flight (air-to-air) visibility is unrestricted" .

At or below the haze top, "the slant range (air-to-ground) visibility is poor", and visibility in haze "varies greatly, depending on whether the pilot is facing into or away from the Sun" . A pilot in clear air above the layer can lose sight of the airport during a descent into it, flying toward the sun.

Haze and smoke also last longer than fog. The handbook states: "Fog evaporates, but haze and smoke must be dispersed by the movement of air" . Fog evaporates in the sun. Haze and smoke disperse only when the air moves.

The handbook states that "Flying into a volcanic ash cloud can be hazardous", and names the material, "silica (glass)" . Piston airplanes are "less likely to lose power" than jets, and the handbook adds that "severe engine damage is likely after an encounter with a volcanic ash cloud that is only a few hours old". Particles hitting the windshield "sandblast the surface into a frosted finish that obscures the pilot's view". A pilot in a Warrior avoids the forecast ash area entirely.

Weather radar detects precipitation. The handbook describes radar images as "graphical displays of precipitation and non-precipitation targets detected by weather radars" . A radar picture with no returns is not proof of visual conditions. Cloud without precipitation produces no return, so an airplane can enter instrument conditions with a clear display on the panel.

Visible and infrared imagery show cloud rather than precipitation, and the handbook notes that "visible imagery is only useful during daylight hours" while infrared and water vapor imagery are "useful day or night" . Radar shows precipitation, and satellite shows cloud. Neither product substitutes for the other.

Datalink radar is always older than its time stamp. The advisory circular states the minimum: "pilots must assume that data link weather information will always be a minimum of 7 to 8 minutes older than shown on the time stamp" . The NTSB found the gap can be larger still, and that "in extreme latency and mosaic-creation scenarios, the actual age of the oldest NEXRAD data in the mosaic can EXCEED the age indication in the cockpit by 15 to 20 minutes" .

The use rule follows from the latency. The advisory circular limits datalink radar to "broad strategic avoidance of adverse weather" . Strategic means a decision an hour ahead to fly around a system. Tactical means a flight between two cells 5 miles apart, and the display is too old for that use. A storm that moves at 40 knots travels more than 5 miles in 8 minutes.

Flight Information Service-Broadcast is free on the 978 MHz universal access transceiver network. It carries METARs, TAFs, NEXRAD mosaics, AIRMETs, SIGMETs, NOTAMs, and more . A pilot needs ADS-B In equipment on 978 MHz to receive it and pays no subscription.

FIS-B does not replace a briefing. The advisory circular gives the reason: the broadcast "may not include all the weather products or NOTAMs that a preflight briefing includes", so the information "may not be relied on for a thorough preflight briefing" .

"VFR flight not recommended" is the strongest advisory a briefer can give, and it is still advisory. A briefer uses it when conditions "would make flight under VFR doubtful". The AIM states the boundary: "This recommendation is advisory in nature. The final decision as to whether the flight can be conducted safely rests solely with the pilot" .

The AIM gives the pilot's next action. "Upon receiving a 'VFR flight not recommended' statement, the non-IFR rated pilot will need to make a 'go or no go' decision", weighing "the current and forecast weather conditions against the pilot's experience and ratings", and the airplane's "equipment, capabilities and limitations" . The decision is the pilot's because nobody else has those three facts.

The AIM defines four flight categories :

Each definition uses the word "and/or". Either the ceiling or the visibility can put a field in a category by itself.

MVFR conditions require a decision. The legal VFR minimums fall inside the MVFR range, and personal minimums usually fall above it. A student pilot on a solo cross-country and a 1,500 hour pilot can read the same MVFR forecast and reach different answers.

The adverse conditions section lists the no-go triggers. AC 91-92 tells pilots not to "plan flights in or near current or forecast convective activity" and warns about areas en route that "may be below VFR minimums, even though reporting stations are at or near VFR minimums" . Known or forecast icing, turbulence aloft, or convection is a no-go for a trainer with no deicing equipment.

Personal minimums are written numbers. AC 91-92 lists establishing them first among its do items: "Establish personal minimums that reflect your level of proficiency" . Ceiling, visibility, wind, and crosswind each get a number. Each number sits above the legal minimum, and the pilot writes it before the trip.

The comparison is mechanical. A pilot compares the forecast conditions against the written number and follows the number. A number that the pilot changes on the ramp provides nothing, because the pressure to go is highest at the moment of departure. AC 91-92 lists the failure directly in its do not items: do not "plan flights that exceed your personal minimums or level of proficiency" .

A pilot sets the continue or divert decision point before launch. A named place, and named conditions at that place, convert a judgment under stress into a comparison. PA.I.C.R1a asks for "circumstances that would make diversion prudent" , and an applicant with a named point and a named trigger answers it in one sentence.

Weather worse than briefed and trending below personal minimums is that circumstance. AC 91-92 gives the action: do not "continue VFR into IMC", and instead "wait it out or turn around if you find en route weather lowering below your personal limits" . Recognizing the condition is Task C work. Flying the diversion is a navigation skill the checkride tests separately.

An applicant states the go/no-go as a conclusion, and the evaluator listens for the reasoning behind it. The reasoning has four steps:

An applicant who says the weather looks fine has given an impression. An applicant who names the ceiling, the visibility, the convective forecast, the personal minimum for each, and the result has answered PA.I.C.S3.

Each product has an age. The AIM directs a pilot to check "the currency of the product (that is, product issue and valid times)" along with its type and relevance . A METAR is minutes to an hour old. A TAF becomes less accurate through its period. An FB forecast issued at 0000 Zulu describes a wind that changes before 1400.

A clean current METAR does not override a worsening TAF. The report describes the past hour at one point. The forecast describes the next several hours across the terminal area. A pilot who compares them uses the trend, because the flight happens in the future.

Four inputs show the trend:

AC 91-92 gives a number for the spread. Be "especially cautious when the temperature and dewpoint spread is 3 °C or less: fog may form" .

A valid time without an issue time hides the age of the product. An issue time without a valid time hides the period the product covers. An evaluator can hand over any Task C product and ask for both times before asking what it says. The answer comes from the header.

Sources for this module

You are not asked to read these end to end. Have them, and know where in them this module lives. On the checkride you may open the handbook and you may not open this site. Each one links to where you get it. Reading a full chapter is worth it, and it is not required to pass this module.

Your study guide and quiz

The facts to remember are:

Study guide — Module 4-3 (PDF)

Task C covers where the weather comes from, what the products say, why the air behaves as it does, and what the decision is. The Malbis Beech had each product before takeoff. The pilot read the surface observations, which showed VFR conditions, and not the convective SIGMET, which implied severe turbulence, severe icing, and low-level wind shear.