The Effects of Weather on Aircraft Part 1 of 2

Lesson Overview How ice impacts flight How a microburst can induce wind shear on an aircraft How sandstorms can be hazardous to air flight How wake turbulence affects air flight

How Ice Impacts Flight 13 January 1982 Air Florida Flight 90 took off from Washington DC Reagan-National Snow was falling fast Plane was de-iced twice Plane waited on runway 59 minutes It crashed into 14th St bridge less than 2 miles north of runway

How Ice Impacts Flight 74 passengers and 5 crew were on aboard The plane’s tail hit the bridge, breaking off The nose pitched down, crossed the bridge and plunged into the icy Potomac River A flight attendant and 4 other passengers survived 4 motorists on the bridge were also killed

Air Florida Flight 90 -- What Happened? Engine anti-ice system was not turned on System runs hot air over engine parts and keeps probes that monitor engine performance free of ice Engine thrust probe was iced over Probe told pilots thrust was greater than it really was As a result, crew pitched nose up 30-40 degrees even as they were losing altitude just before hitting the bridge Crew took off even though snow and ice covered the airfoils (wings) Crew had little experience flying in snowy weather

Ice Hazards Ice affects lift, weight and drag Ice can also make hard to see out windshield Lift Thrust Drag Weight

Lift, Weight and Drag As ice builds up, lift is decreased while weight and drag are increased Increasing angle of attack will cause boundary layer of airflow to separate quicker leading to a stall condition earlier than normal Therefore, pilot must increase thrust to maintain lift

Causes of Icing When supercooled water hits the airfoil, windshield, propeller, and other surfaces, part of the droplet freezes instantaneously How the remaining water droplet freezes determines the type of ice formation Clear Rime Mixed Ice builds quickly as an airplane flies through the super-cooled rain droplets or cloud condensation Video Clip 5:25 – 9:20

Icing Cloud Types of Concern Stratus

Icing Cloud Types of Concern Stratocumulus

Icing Cloud Types of Concern Cumulus

Forms of Ice Clear -- hard, smooth, solid glossy, see-through Rime -- brittle, frostlike, white, rough; easier to remove than clear ice Mixed -- mixture of clear and rime; mushroom buildup on leading edge

Icing – Preflight Actions Check with weather forecasters Review and file your flight plan Storing aircraft in bad weather De-Icing Solution Rule of Thumb – The only safe aircraft is a clean aircraft Video Clip (14:30 – 16:10)

Icing – In-Flight Actions Anti-Icing Equipment Pilot Heat Windshield Heat Prop Heat Inflatable “boots” for wings Once icing is observed, the rate of accumulation and how long you stay in those conditions become critical You must act => Climb, Descend, Divert You must first contact the ATC!! Rule of Thumb – There is no such thing as a “little” ice Video Clip (19:15 – 21:12)

Icing – Scenario You are flying at 5,000 feet through thick stratocumulus You are halfway into a 4-hour flight You notice ice forming on your wings Your engine is slowly losing power and running a little rougher than normal What do you do? What if the ATC does not allow you to climb due to another aircraft coming your way? What if the ATC does not respond? Video Clip (21:12 – 22:54)

Activity 1: Icing Research Tunnel   Watch the video “NASA at 50: Icing Research Tunnel Designated as Historic Landmark” Answer the analysis questions Chapter 2, Lesson 5