How Airlines Deal with Severe Weather

Air Travel, Severe Storms, and Tornadoes

Just how do airlines deal with severe weather?  We’ve had an unusually high number of significant severe weather outbreaks here in the United States over the past couple months, including the March 2nd tornado outbreak, in which massive tornadoes leveled towns and caused fatalities in Indiana, Kentucky, and other parts of the southeast United States.

The March 2nd outbreak was only a couple days after the February 29th outbreak where extreme storms hit the southeastern United States.  We’ve noticed this has been frequently searched for and appears to be a topic of interest for many.

To begin with, lets first look at the monster tornado which pushed through St. Louis Lambert Airport (STL) last year.  Passengers were on-board American Airlines aircraft on the tarmac while the flight crew had no knowledge of the tornado warning.  The winds from the tornado moved these two aircraft causing significant damage to the planes.

When the tornado hit St. Louis Lambert Field (STL) no one was prepared or aware.  The American Airlines concourse was severely damaged as the tornado hit the airport.  A Delta pilot was conducting a pre-flight check at the time, also not aware of the warning, let alone the tornado.

Even the TSA security employees ran for their lives when the tornado hit.  As TSA screeners are there for your security and part of the Department of Homeland Security, you’d think they would at least have a heads up on the tornado.  A simple NOAA radio would have provided the TSA and airport employees with the required information.

Looking back at St. Louis, no one was aware of the Tornado Warning, let alone the fact a large tornado was on the ground headed towards the airport.  The St. Louis tornado was known to be on the ground and there was no question about it with Doppler Radar providing returns from the flying debris field; it takes a large tornado to pick up the debris field with Doppler Radar.

Why Did Saint Louis not Know?

 

The National Weather Service (NWS) products created for aviation use do not address tornado watches or warnings.  Typically it takes the actual spotting of a funnel cloud or a tornado on ground for it to be reported – by this time its too late and the control tower is evacuated.  The terminal area forecast (TAF) will use the abbreviation FC meaning funnel cloud spotted and FC+ meaning tornado on ground in weather reports.  At this point, it is often too late after an aircraft has fully boarded or for planes which already pushed back to wait out the storm.

Commercial Airliners will not depart or arrive when a severe storm is over the field, but the knowledge of a Tornado Watch or a Tornado Warning would be helpful.  On March 2nd, there were many diversions to alternate airports as the storm moved over airports experiencing severe weather including Indianapolis (IND), Louisville (SDF), Cincinnati/Northern Kentucky (CVG), and Nashville (BNA).

After the St. Louis Airport tornado, airports are doing a better job at obtaining Tornado Warning information and moving passengers into shelter areas – this is exactly what happened at Cincinnati Northern Kentucky International Airport on March 2nd.  While the airport did not take a direct hit, flying debris landed on the runways which required the airport to temporarily close for debris removal, given engine intake of debris is not only dangerous, but can be quite expensive.

From personal experience, I once landed at MSP in a Boeing 757-300 ahead of a large thunderstorm.  It was obvious there was a storm to our north during our initial decent and landing, which required the flight crew to detour around some of the cumulonimbus build-up.  However, the flight crew was not aware of a tornado warning for Hennepin County, where Minneapolis St/Paul International Airport (MSP) is located, until the aircraft landed.  As soon as we touched down, the Tornado Sirens could be heard, even with the noise of the reverse thrust.  We touched down just prior to the storm and were one of the last aircraft to land; the storm had not started, but it was just north of the airport and moving south quickly.

While most warnings do not result in extreme tornadoes, change is needed when it comes to NWS aviation products.

Severe Weather Avoidance

 

During severe weather events, pilots adjust flight plans to avoid flying into the tops of thunderstorms.  For a New York to Los Angeles flight, this could mean a 500 mile detour to the north or south to get around a line of storms in the Midwest.

When storms top-out between 30,000 to 50,000 feet, you don’t want to mess with them, and neither do pilots.

Pilots will do what its necessary to avoid flying through the tops of the storms, even if it means a significant detour.  On a recent flight from Minneapolis (MSP) to Louisville (SDF), a line of severe thunderstorms was in place forming a sold line from Iowa, across all of Illinois, and much of Michigan.  In good weather, the flight is normally about 600 miles and 90 minutes; this particular night we detoured around the storms.

The detour included flying north out of the Twin Cities to northern Minnesota where we then turned to an east heading towards Green Bay, Wisconsin; from Green Bay, we flew across the Great Lakes to the Detroit area, where there was a break in the line of storms – from there the flight path took us towards Cincinnati and into Louisville.   That night we covered nearly 1500 miles to detour around the weather, which added an additional hour flight time.

Such zig-zag routes are common to avoid flying through dangerous cumulonimbus convection – but it can also backup air traffic looking to fly through the gaps in the weather.

Windshear Avoidance

 

Delta Air Lines L1011 - Lockheed TriStar | FlyersPulse Airline News
Delta L1011 Lockheed TriStar | Airline News

Windshear is a significant problem when flying in and out of airports during severe weather.  If we look back to August 2, 1985, Delta Air Lines flight 191, a Lockheed TriStar L1011, was making its final approach into Dallas Ft/Worth International (DFW).  A Thunderstorm had developed over DFW, but the pilots continued landing.  At 800 feet above ground level, a micro-burst hit, causing the plane’s airspeed to increase significantly.

The aircraft was supposed to land at a speed of 149 knots, but the micro-burst caused their airspeed to increase to 173 knots; as fast as the airspeed increased, the speed dropped to a mere 119 knots as a downdraft pushed the aircraft down.  The flight crew attempted to recover by applying full throttle to initiate a go around, but it was too late.  The aircraft impacted the ground short of the runway; only 29 of the 152 passengers on-board survived.

Today, windshear detection technology has improved greatly.  When severe storms where windshear is likely, aircraft circle and wait for conditions to improve.   Airports now have high-end windshear detection equipment and a lot has changed since Delta 191.

When weather does get bad, sometimes too many flights enter a holding pattern waiting for the storm to clear at a particular airport, which sometimes results in diversions to other airports – often for a gas and go.  Unfortunately things don’t always work as planned, which is why rules are now in place to avoid excessive tarmac waits.

FAA Flow Control and Ground Stops

 

The FAA has a flow control program which prevents too many aircraft taking off for a destination where a weather problem exists and too many aircraft are already inbound or in a holding pattern waiting to land.  No sense in having new aircraft depart for a destination, causing an even larger backup, when those already airborne are in holding patterns, burning fuel, while being sequenced for landing.

There is what is known as a “Ground Stop” and a “Delay Program” — during a ground stop, aircraft are stopped on the ground and not allowed to take-off to the destination airport until weather conditions improve at the destination.

An airport specific “Delay Program” will slow departures to the destination airport where the weather problems exist.  Sometimes it is necessary to cancel some flights, but those that go are provided with take-off times to avoid too many arrivals at once.

Ground-Stops and Delay Programs not only cover severe storms, they cover everything from low ceilings to winds – pretty much anything that can cause air traffic to back-up.  Air Traffic Backup’s are common in the New York City area with three major airports located closely together.  Sometimes something as simple as a crosswind can cause backups at JFK, LaGuardia, and Newark.

When it comes to canceling flights, airlines will typically look to their smaller, regional jet flights first, while international flights and other long-haul services using larger aircraft are given priority.

A good resource when traveling is using the FAA’s National Airspace System Status.  Their website contains the latest information about ground stops, delays, airport closures, and other departure and arrival delay information.

On a final note, flying is the safest mode of transportation.  Severe storms are avoided and air travel is safer than ever today.

While this doesn’t cover everything, any questions, just make a comment and ask.

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2 Responses

03.17.12

We flew from Chicago to Louisville and flew over Michigan towards Detroit and then south to get around a line of severe thunderstorms. Incredible to see the t-storms light up the sky at night, especially when there is a big line of em!

03.17.12

In reference to Flight 191, wasn’t it JetBlue 191 where the pilot flipped out and went into a psychotic state?

Seems Flight 191 isn’t a very good number.

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