Aircraft Performance Weather Weather Reports and Forecasts Weather Reports and Forecasts Emergencies FAR/AIM, NTSB 830, PTS, and Logbooks

Factors Affecting Performance Takeoff Data Card Airplane Weight and Balance Basic Performance Charts Headwind/Crosswind Calculations

Additional weight Wind Runway surface and condition Runway gradient Density altitude and humidity Pilot technique

Higher takeoff speed Longer takeoff roll Reduced rate and angle of climb Higher landing speed Longer landing roll

HeadwindDecreased takeoff/landing distance

TailwindIncreased takeoff/ landing distance

CrosswindIncreased tak

Friction – more friction means longer takeoff roll shorter landing roll

Upslope increased takeoff roll Decreased landing roll

DownslopeDecreased takeoff rollIncreased landing roll

Takeoff downhill / land uphill

Air expands with heat and humidity and becomes less dense

The less dense the air, the less performance from the aircraft

Engine produces less power Propeller is less efficient Wing is less efficient

Calculated based onAir pressure (barometric)Air temperature

High density altitude◦Low density of the air (high altitude)Low density altitude◦High density of the air (low altitued)

Failure to compute and appropriate weight and balance could cause injury or death

14 CFR 91.103(b)(2) “…other reliable information appropriate to the aircraft, relating to aircraft performance under expected values of airport elevation and runway slope, aircraft gross weight, and wind and temperature

Higher takeoff speed Longer takeoff roll Reduced rate & angle of climb Lower maximum altitude Shorter range (used more fuel) Lower cruise speed Less maneuverability Higher stall speed Longer landing roll Additional stress on landing gear & structure

Gross weight – aircraft may not flyAngle of attack may not be able to create

enough lift to fly the aircraft Aft

Better cruise performance, less stability, difficulty recovering from stalls

Forward / aft GCForward – degraded cruise & climb performance

and more difficult to rotate and flare due to larger taildown force requirement

Arm – horizontal distance from datum CG – the point at which aircraft would balance Datum – reference line for arm measurement Moment – weight x arm Station – location designated by arm Useful load – weight carrying capability Empty weight – aircraft w/ equip, ballast,

hydraulic fluid, undrainable oil, unuseable fuel Basic empty weight – full oil Max gross weight - max weight at any time Maximum takeoff - max weight for takeoff Maximum landing – max weight for landing

Need to determine the angle between the runway & wind directionIf wind direction is variable use the largest anglePrinted wind direction are true direction& runway

orientation is magnetic• Add or subtract variation

Variable winds – speed is variable

Ways to do it

The Atmosphere Pressure Wind Moisture Humidity Stability Clouds Air Masses Fronts Frontal Weather Thunderstorms Other Hazards Weather Conditions

Earth is surrounded by a thin layer of air

Air is composed of oxygen, nitrogen, carbon dioxide, and elements of other gases

Air also contains evaporated water

Water vapor is directly involved in all weather phenomena

50% of Earth’s atmosphere is contained below 18,000

Every physical process of weather is accompanied by, or is the result of heat exchanges

Unequal heating of the Earth’s surface causes differences in pressure

Wind is the flow of air from high pressure to low pressure areas

Tendency of the atmosphere is to flow from the poles to the equator, heat up, rise and flow back to the poles

Coriolis force deflects wind to the right in the (northern hemisphere)

Surface friction influences wind flow

Force caused by spinning of the earth Varies in strength with latitude Zero at the equator Strongest at poles Responsible for changing north-south

tendency of atmosphere into west-east pattern in the mid latitudes

Heating and cooling of air causes it to change pressureHot air rises and expands, causing lower surface

pressureCold air descends and contracts, causing higher

surface pressure

Wind is created as air moves from areas of high pressure to areas of low pressure

Coriolis force causes air flowing into or out of a pressure system to rotateRotates clockwise around a highRotates counterclockwise around a low

Air flows counterclockwise, up, and into a low

Air flows clockwise , down, and out of a high

Earth’s atmosphere contains 1%-4% water vaporWater vapor interacting with the heat exchange, is

responsible for all weather Moisture also slows down the standard lapse rate

Standard lapse rate = 2 degrees C per 1000ftMoist-air lapse rate = 1degree C per 1000ft

Moisture influences “dew point”Dew point = temperature to which air must be cooled

to become saturated by water vapor already present in the air

Low temperature dew point spread = high humidity

Water vapor content of the air May be expressed as:

Relative humidity – the ratio of the existing amount of water vapor in the air at a given temperature to the maximum amount that could exist at that temperature; usually expressed as a percent

Mixing ratio – the ration by weight of the amount of water vapor in a volume of air to the amount of dry air; usually expressed as grams/kilograms

Specific humidity – the ration by weight of water vapor in a sample of air to the combined weight of water vapor and dry air

Stability is the tendency of the atmosphere to resist upward movement

Instability - (upward movement ) causesHeating from below – convective current (heat

rises)Low pressure – because of its lifting tendencyCold air aloft – greater than normal lapse rate• When air rises, it cools at a rate of 2 degrees C per

1000ft• Greater differential between hot and cold air

Humidity – due to its slower lapse rate

Characteristics of stable airSmooth airPoor visibilityContinuous precipitation (if any)Stratus clouds

Characteristics of unstable areTurbulence Good visibilityShowery precipitation (if any)Cumulus clouds

A temperature inversion is an increase in temperature as altitude increases

Air beneath inversion is very stable Low visibility “Capping” effect on pollution Develop near the ground on cool, clear

nights

Four families – based on heightHigh- cirrusMiddle – altoLow – (no prefix)Extensive vertical development-

towering cumulus (turbulent) Grouped according to appearance

Cumulus=ragged or puffy; good indication of instability

Stratus = smooth and even; good indication of stability

Combined description examplesCirrostratus – high stratusAltostratus – medium stratusStratus – low stratus

Towering cumulus have extensive vertical developmentCan quickly develop into thunderstormsVisual indicator of heavy turbulence

Rain cloudsRain clouds denoted by “nimbus”Thunderstorms are called cumulonimbus and

contain the greatest turbulence

Large areas of air that are formed over specific Earth regionsPolar regionsTropical regionsThe oceans

Air masses are constantly changingHeating or cooling from belowLifting or subsidingAbsorbing or losing moisture

Its temperature is measured in relation to the temperature of the surface over

which it is passing

A cold air mass has a colder temperature than the surface

Warmed from below, convection currents will be set up, causing turbulence

Improved visibility Unstable Types of clouds-

cumulus and cumulus nimbus Ceilings – generally unlimited Precipitation –occasional local thunderstorms or

showers

A warm air mass has a warmer temperature than the surface

No tendency for convection currents to form, resulting in smooth air

Poor visibility Stable Types of clouds – stratus and stratus

cumulus Ceilings –generally low Types of precipitation – drizzle

Dissimilar air massed don’t readily mix and set up boundaries called frontal zonesThe colder air mass project under the warmer air

massThe warmer air rises over the colder air mass

4 types of fronts Warm front Cold front Occluded front Stationary front

Warmer air is overtaking and replacing the colder air

Cold air is more dense (heavier) than warm air-the cold air hugs the groundThe warm air slides up and over the cold airThe cold air is slow to retreat in advance of the

warm air This slowness of air to retreat produced a

more gradual frontal slope than the one in the cold air frontThus, a warm front, at the surface, is seldom as

well marked as cold frontsThe move about half as fast

The cold air is overtaking and replacing the warmer air

They move at about the speed of the wind component perpendicular to the front just above the frictional layer

Occluded front - when a cold front catches up with a warm front the two collide- where they collide is called an occluded front

Warm air trapped between the two air masses, is forced aloft

The weather is a combination of both the warm and the colds frontsWarm - lowered ceilings, lowered visibility,

precipitationCold – squalls, turbulence, thunderstorms

Stationary front - when neither air mass is replacing the other, the front is stationary

The opposing forces of the two air masses nullify one another and very little motion occursThe surface winds tend to blow parallel to the

frontal zoneThe slope of the stationary front is shallow

600 miles prior – bright skies, unlimited visibility and ceilings 400 miles prior – rapidly decreasing visibilities and ceilings. Rain begins shortly. 200 miles prior – ceiling too low for VFR flight and visibilities lowered to almost zero. As the front is approached there is a

gradual temperature increase and an increase in dew point, and atmospheric pressure would lessen

Beginning the flight in the warm air mass, sky likely overcast, stratocumulus clouds, smooth air, and relatively low ceilings and visibilities until the flight was approaching the front

If flight continues into the frontal area, a few altostratus clouds and a dark layer of nimbostratus (rain clouds) would likely be seen

Gusty wind and wind shifts Possibility of squalls and cumulonimbus clouds

Too high to fly over, unsafe below them, and nearly impossible to fly through them

The worst weather for a pilotA combination of the warm front and cold front

conditions As it approaches , the warm front conditions

are prevalentLowering ceilings, lowering visibilities, and

precipitation Followed almost immediately by cold front

conditionsSqualls, turbulence, and thunderstorms

The cumulonimbus cloud – thunderheadProduce strong updrafts, large raindrops, hail,

lightning, thunder, downdrafts, and strong turbulence

May exceed 50,000 ft in height

3 stages Cumulus stage

Updrafts and growth Mature stage

Up and downdrafts produce gusty surface windsPrecipitation begins

Dissipating stageDowndrafts

Air mass thunderstormsOften result from surface heatingTend to self-destruct (downdrafts with rain)20-90 min. life cycle

Steady state thunderstormsAssociated with a weather system but may be intensified

by afternoon heatingTend to growCan last for hoursPhysically, in its mature stage, the top of the cloud begins

to flatten to an anvil shape and point in the direction the cloud is moving• strong updrafts at the leading edge of the cloud• Within and directly beneath are updrafts and

downdrafts• The rear generates strong downdrafts

Freezing rainSupercooled water droplets adhere rapidly on the

surface of the aircraft and the windshieldCan obscure vision – reverse flight path

Icing (other than freezing rain) only occurs in the cloudsThere is no reason for the VFR pilot to be in this

situation Ground fog

can form rapidly with the right conditions – especially dangerous for takeoff and landing

Fog can formBy cooling air to its dew point• Beware when the temperature/dew point spread is

within 3 degrees of each other – as night approachesAdding moisture to the air near the ground

Frost on the wings can cause the aircraft to stall at a higher speed than normal Frost can disrupt the smooth flow of air over the

wing’s surface – do not fly with frost on lifting surfaces

Clear air turbulence occurs outside of cloudsJet streamLarge thunderstorms – cumulonimbus cloudsMountain waves

Surface Analysis Charts Weather Depiction Charts Low-Level Prognostic Charts Area Forecasts (FA) TAFs METARs Wind and Temperature Aloft (FB) Pilot Reports Obtaining a Weather Briefing FSS/DUAT Standard/Abbreviated/Outlook Briefings AWOS/ASOS/AWSS reports

Zulu time Greenwich mean time 24hr clock A standard reference to eliminate time-zone

confusionStandard time to UTC

Eastern + 5 hr = UTCCentral + 6 hr = UTCMountain + 7 hr = UTCPacific + 8 hr = UTCAlaskan + 9 hr = UTCHawaii + 10 hr = UTC

SLCC FA 14105SYNOPSIS AND VFR CLDS/WXSYNOPSIS VALID UNTIL 150500CLDS/WX VALID UNTIL 142300…OTLK VALID 142300-150500ID MT NV UT WY CO AZ NM

SEE AIRMET SEIRRA FOR IFR CONDS AND MTN OBSCN.TSTMS IMPLY PSBL SVR OR GTR TURBC SVR ICG LLWS IFR

CONDS.NON MSL HGTS ARE DENOTED BY AGL OR CIG.

SYNOPSIS…HIGH PRES OVR NERN MT CONTG EWD GRDLY. LOW PRES OVR AZ NM AND WRN TX RMNG GENLY STNRY. ALF…TROF EXTENDS FROM WRN MT INTO SRN AZ RMNG STNRY.

Terminal aerodrome forecast Weather forecast for selected airports

TAF – routine forecastTAF AMD – amended forecast

Issued four times dailyIssued at 0000,0600,1200, 1800 (UTC)Valid for 24 or 30 hours, depending on stationThere is some overlap between forecasts

TAF AMD YSBK 241854Z 2008 VRB03KT CAVOK FM23 02010KT 9999 SCT040 BKN100 PROB30 2023 2000 MIST INTER 0608 7000 LIGHT SHOWERS OF RAIN BKN020 T 17 21 19 15 Q 1016 1014 1013 1013

ExampleMETAR YSBK 0230Z 31008KT //// 19/04 Q1015 RMK RF00.1/012.0 CLD:SCT025 VIS:9999

Aviation routine weather reportUse abbreviations similar to TAF’s

Report of condition at time of observationMETAR = regular hourly reportSPECI = special report necessitated by rapidly

changing weather conditions

DATA BASED ON 010000ZVALID 010600Z FOR USE 0500-0900Z TEMP NEG

ABOVE 24000FT 3000 6000 9000MKC 2426 2726-09 2826-14ABQ 1912+15

Winds aloft are forecast for specific locations in the US

Four-digit group used to represent wind direction and speed2525 = from 250 at 25kts0315 = from 030 at 15kts

Six-digit group is wind and temperature aloft353515 = 350degrees at 35kts, temp = 15c

Wind speed over 100kts, forecaster adds 50 to direction and subtracts 100 from the speed7302-49 = 230 at106kts, temp -49c

Winds less than 5kts is coded as 9900

Report given to FSS by pilots in flightCan be a source of real-time information

DrawbacksNot everyone reports everythingIn really bad weather, no one else has been a

trailblazerAge of report can be a factorApplicability depends of aircraft type

PIREPS are encouraged if unexpected weather is encountered

UA/OV KMRB-KPIT/TM 1600/FL100/TP BE55/SK BKN024-TOP032/BKN-OVC043-TOPUNKN/TA M12/IC LGT-MOD RIME 055-080

Call 1-800 WX-BRIEFWhen calling make sure the briefer knows you are a pilot (student pilot) Intended route (or “local”) Departure/destination airports VFR/IFR Type of aircraft Departure time (UTC) and time enroute

Standard is given in following orderIs there any bad weather happeningWhat’s the big pictureWhere are the highs, lows, and frontWhat are the current conditionsWhat’s forecast for the near futureAny needed data re: airport closures

Outlook briefing – more than 6 hours Abbreviated briefing

Supplement available infoUpdate a previous briefingFind out specific info

Self briefing sources DUATS – direct user access terminal

◦ www.duats.com or www.duat.com◦ Free service supported by FAA◦ Official weather briefings via computer◦ Account available to anyone with valid medical or

pilot certificate Computer briefing services

◦ DTN, WSI, etc. Web based briefings

◦ http://aviation weather.gov◦ www.weather. ComCaution: computer based sources other than DUATS

may not be considered an official briefing

Weather reporting systems which may be used for the creation of a METAR or

recorded audio report of existing weather Automated weather observing system

(AWOS) Automated surface observation system

(ASOS) Automated weather sensor system (AWSS)

Radar Wx Reports Severe Wx Reoperts and Forecasts AIRMETs SIGMETs / Convective SIGMETs NOTAMs Wind Shear Reports Wind Shear Recognition and Avoidance Weather Related Aeronautical Decision

Making and Judgment

AWOS-A reports altimeter setting AWOS-1 reports altimeter, wind, temperature,

dew point, and density altitude AWOS-2 provides info from AWOS-1 + visibility AWOS-3 provides info from AWOS-2

+cloud/ceiling data ASOS provides the info of at least AWOS-3 AWSS is a follow-on program that provides

identical data as ASOS

Radar weather report (SD)Text report regarding areas of precipitation

appearing on radarIndicates the type, intensity, location, movement,

and height of the echo topAll heights are reported above sea levelAlso referred to as RAREPs

Radar summary chartsCharts displaying a collection on radar reportsShows tops of clouds, direction of movementIntensity indicated by contoursReport combines 6 levels to produce 3 contours

Convective outlook (AC) National forecast of thunderstorms Flight planning tool to avoid thunderstorms Three forecasts:

Day 1 convective outlook (first 24hrs) issues at 0600z,1300z,1630z,2000z, an 0100z

Day 2 convective outlook (next 24hrs) issued at 0830z (ST)/0730z (DT) update at 1730z

Day 3 convective outlook (next 24hrs) issued from day 3 at 1200z to day 4 at 1200z

Define areas of risk for severe and general (non-severe) thunderstorms

Winds equal to or greater than 50kts at the surface

Hail equal to or greater than ¾ inch in diameter

tornadoes

Severe weather watch bulletin (WW) Define areas of possible severe

thunderstorm or tornado activityA severe watch describes areas where the threat

of tornadoes existsUnscheduled and issued as required

Preliminary notification of a watch called the alert weather watch bulletin (AWW) is sent before the WW to alert necessary personnel

Airmen’s meteorological information Issued to warn of weather hazards to small

aircraft Moderate icing Moderate turbulence IFR conditions Sustained surface winds of more than 30kts Extensive mountain obscuration

Significant meteorological conditionsIssued for weather to ALL aircraft Severe turbulenceSevere icingDust storms, sand storms, or volcanic ashVolcanic eruption

Convective SIGMETs Tornadoes Lines of thunderstorms Severe turbulence Severe icing Embedded thunderstorms

NOTAM (D) – distance NOTAMsAffect cross-country pilots and local airport users

Closed airportsNavigation aids off the airGrass cutting operationsTaxiways closed

NOTAM (FDC) – Flight data centerChanges in regulations or chartsEmergency flight restrictionsNational airspace closure information (911)Wide-spread traffic delays or closures

Pointer NOTAMs – highlight another NOTAMAssist users in cross-referencing important

information that may not be found under an airport or NAVAID identifier

Wind shear is a change in wind speed and/or direction in a short distance resulting in a tearing or shearing effect

Report the loss or gain of airspeed and the altitude at which it was encountered

Pilots should promptly volunteer report to controllers of wind shear conditions encountered

A Controller may issue a wind shear alert based upon information derived from equipment in the control tower

Wind shear can exist in a horizontal or vertical direction and occasionally in both

Shows up as a momentary change in airspeed or altitude (or rate of altitude change) Can be very dangerous at low altitudes

Avoidance Recognize the problem and consider going

elsewhere Understand conditions conducive to

developmentConvective storms (thunderstorms, rain/snow

showers)FrontsStrong surface windsUnstable (turbulent) airStrong winds on top of a temperature inversion

Listen for reports from other pilots or ATC Watch for confliction wind indications

The best place to make weather related decisions is on the ground

Responsibility Early - instructorLater – student

Develop alternative plans for unforecast weather before a decision becomes critical

Don’t delay using your alternate plan When in doubt err on the conservative side

Emergency proceduresAviate Navigate Communicate

Fly the aircraft Review and follow the checklist Stabilize the problem to the extent possible Land as required

14 CFR Part 1 14 CFR Part 61 Recreational/Student Limitations 14 CFR 61 Private/Students Limitations 14 CFR Part 67 14 CFR Part 91 14 CFR Part 141 NTSB 830 AIM Pilot Logbooks Aircraft Logbooks Practical Test Standards FAA Advisory Circulars Aeronautical Decision Making and Judgment