Aviation Weather

Air Temperature and Pressure Affecting Aircraft

Hot air is thin, less dense, and rises.

Cold air is thick, heavy, and sinks

The energy of crickets is directly proportional to the outside temperature. Count the number of times a cricket chirps in 15 seconds then add 37 to that number and you’ll have the correct temperature in degrees Fahrenheit.

Temperature inversion, warm air above cooler air, therefore,the cool air does not rise, being heavier than warm air, itstays near the ground.

Warmer air

Cooler Air

Smoke willnot rise inheavy, coolerair.

45 degrees

28 degrees

Cloud produces rain because the cloud exists in a warmer area abovethe freezing level.

But the rain is falling into colder air below the freezing level.

The airplane’s skin is also below freezing, and the cold rain will freezeto the plane as clear ice!

Temperature inversion

If aircraft course is between 0 and 179 degrees, fly odd thousand,5000, 7000, 9000,11,000, etc.

If airplane course is between 180 and 359 degrees, fly even thousand,4000, 6000, 8000, 10,000, etc .

ALWAYS set your altimeter to the local barometric pressure within 100 miles of your location.

IF YOU DON’T…

Air rises in low pressure areasand the wind is counterclockwise.

Air sinks in a high pressure area andthe wind is clockwise.

Shear ZoneWind

WindShear Zone

Lots of turbulence in a shear zone!

Counterclockwise-cloud rotation in the rising air around a low pressure area.

Weather Charts

Icing

Aircraft Performance

TEMP = 98

PA = 4750’

DA = 8000’DA = 3000’

PA = 4750’

TEMP = -8 FTEMP = +18 C

Outside air temperature 20 C

PA = 6000’

Rate of climb = 375 fpmOutside air temperature -20 C

PA = 6000’

Rate of climb = 580 fpm

PA =1000’

ROC = 650 fpm

Take Off Distance ChartVerify that you match the conditions in the landing chart

Find the row and column for the temperature and pressure altitude.

Read the ground roll and distance to clear a 50 foot object. Interpolate for intermediate values as necessary.

Apply necessarycorrection factors:WindGrass runway

Microburst / Windshear

Windshear is any rapid change in wind direction or velocity. Severe windshear is a rapid change in wind direction or velocity causing airspeed changes greater than 15 knots(~17mph) or vertical speed changes greater than 500 feet per minute (around 5-6 mph in the vertical direction that is a lot).

The life span of a Microburst is around 15-20 minutes.

Wind variations at low altitude have long been recognized as a serious hazard to airplanes during takeoff and approach.

So you can see that a sudden change of wind speed can change theairspeed and therefore, change the amount of lift keeping the airplane in the air. If the airplane is going slow, like on take off or landing, this can be very dangerous.

This is not a cloud;it is dust and dirt pickedup by a GIANT microburst!!!

Here comes someone stupid!!

http://www.usatoday.com/weather/tg/wmcrbrst/wmcrbrst.htm

AIRSPEED = GROUND SPEED + or - WIND SPEED

Wingtip Vortices

http://www.eng.vt.edu/fluids/msc/gallery/vortex/iat032b.htm

http://www.eng.vt.edu/fluids/msc/gallery/vortex/f16_4bg.htm