Posted on Aug 23, 2018
Image Credit: © Dreamstime.com
Posted on Aug 23, 2018
The landing of Asiana Airlines flight 214 should have been routine in ever since with perfect visibility on a clear day in San Francisco. However, due to pilot error, the plane crashed resulting in the deaths of 3 passengers. This tragedy stands as a stark reminder that all landings are not created equal. Many conditions exist that can make landing a large commercial airline is anything but simple. Pilots may be required to approach at a steep angle or deal with strong crosswinds blowing across the runway. Here's a list of some more difficult types of landings commercial pilots deal with.
Some speculated that the pilots of Asiana flight 214 were attempting a slam dunk–style landing when the plane crashed. The term “Slam Dunk” refers to approaching the airport at a higher altitude and then descending quickly to achieve a stable position before landing.
According to former airline captain and assistant professor at Embry-Riddle Aeronautical University Greg Zahornacky, ”It largely depends on what airport you're going into and what the airspace is looking like, but sometimes [air traffic control] will ask you to do a higher or short approach, It's a higher descent rate from a higher altitude."
“The procedures followed during a slam dunk are the same as any other approach,” says Zahornacky. “Pilots select a good rate of descent that allows them time to deploy landing gear and flaps, and be stable at around 1000 feet of altitude.” Most pilots don’t consider this to be dangerous, but it is a bit more difficult than a standard landing.
Patrick Smith, a veteran pilot of more than 20 years says,” ideally, if it were up to you, it would be a more gradual descent, So it's tricky in the sense that you've got to manage the plane's momentum during descent to make sure you can get down per [air traffic control's] instructions and be stabilized at the bottom of the descent to go ahead and finish the approach."
Regardless of landing type, pilots monitor the same flight instruments to guarantee a safe landing.
Landing during strong crosswinds, or winds not aligned with the runway, make any approach a little more difficult. There are certain airports that are notorious among pilots for their crosswinds. Some include Keflavik International Airport in Iceland, LAX in Los Angeles, and Logan in Boston.
Using a higher speed during the approach helps mitigate the negative effects of the wind. In order to determine the additional speed needed, pilots refer to what's called a crosswind component chart. "We use a formula for how much speed we have to add to the approach," Says Smith. Commercial aircraft generally use an approach speed of 130 to 150 knots. According to Smith, they might increase that by 10 to 15 knots for very windy conditions. Pilots may also adjust the plane's thrust up or down to maintain pace as wind speeds change.
Because crosswinds push the plane away from the center of a runway, pilots may steer into the crosswind to offset the drift. Pilots manipulate the ailerons, normally on the wings' trailing edges, to control the plane's roll, in addition to the rudder, which controls the yaw. Because of these factors, a plane might not be perfectly level when it touches down when landing in a gusty crosswind.
"You put one set of landing gears down first—you're landing crooked," Smith notes. "People might feel the plane hitting on one side before the other and think it's a mistake, but it's not." Smith says the technique itself is "a little tricky to master, but you get used to it." Windy conditions can also produce turbulence which makes the experience very bumpy for everyone involved.
Drastic changes in wind speed over a small area, known as wind shear or microbursts, used to be quite a problem for airplanes. These issues were implicated in disasters like the crashing of Eastern Airlines Flight 66, which crashed during landing at John F. Kennedy International Airport in 1975. Technological advancements and detection systems at airports and onboard aircrafts have greatly reduced the difficulties in dealing with wind shear. "Those kinds of accidents for the most part have disappeared," Smith says. "Wind shear can be seen and predicted, and crews warned accordingly."
Another landing situation that requires additional pilot awareness is a short runway. "You do tend to concentrate a little more on short runway approaches," states Smith. "There's less margin for error." The runways are only 7000 feet long at LaGuardia airport in New York due to it’s location. Ronald Reagan Washington National Airport's longest is 6869 feet. Runways typically run a few thousand feet longer at other airports.
To deal with less runway real estate, pilots try to land at the slowest possible speed. As with all aspects of landing an aircraft, these speeds are not determined randomly but are based on variables such as the aircraft's weight, flap-setting options, etc. Ultimately, an approach plan will guarantee that a plane has enough stopping distance even on a shorter runway. Pilots also brake the plane harder and rely on reverse thrusting more when runways are short.
In rare cases an aircraft may need to execute a sharp turn as part of entering the approach and landing phase of the flight.
Smith sights the expressway visual approach to runway 31 at LaGuardia as a famous example. Pilots follow the Long Island Expressway heading East until they reach the New York Mets' baseball stadium, Citi Field, at which point the pilot banks the aircraft to the left about 90 degrees to align with the runway.
"It's not typical to be making that big of a turn that close to the ground," Smith says, "but you're still at 1000 feet or so, which is plenty of altitude."
Pilots often brag about getting a bird's-eye view of the game when completing this maneuver. Passengers, however, may have slightly different reactions. "In the minds of some people, it seems like the wing is scraping the ground, that you're doing this steep bank," Smith says. "But those turns are never as steep as people think they are." Even when making a large left or right turn, commercial jetliners rarely bank beyond 25 degrees of wing angle.
Flying remains one of the safest ways to travel from a statistical standpoint even though some approaches and landings keep pilots on their toes. "There's no such thing as an unsafe commercial airport. If there were, no airline would fly there," Smith says. "By extension, there's no such thing as an unsafe landing."
For more information on proper flight training, please contact Elevate Aviation here in Salt Lake City, Utah.