Truly Madly Deeply

Northwest 255 had just taken off from Detroit on Aug. 16, 1987, when it began rocking side to side. The plane clipped a building and caught fire before sliding under a railroad embankment and two highway overpasses (right). The crash, which killed all 154 onboard and two bystanders, occurred because the MD-82's pilots did not extend slats on the leading edge and flaps on the trailing edge of the wings to generate extra lift. The manufacturer recommended that airlines modify their MD-80 cockpit checklists; U.S. carriers did so, but not all foreign carriers. In 2008 a Spanair MD-82 crashed in Madrid because of a similar mistake, killing 154—showing that failure to modify procedures in response to crashes, close calls and government advisories can cost lives. Here are other changes in the cockpit that reduce chance of pilot error. —Mark Huber 

1. Make Two-Person Altitude Calls

To prevent planes from dropping below assigned altitudes—which increases the risk of midair collisions—the co-pilot sets the altitude, called "pointing," and the pilot confirms that it is correct. 

2. Retract Speed Brakes

Failing to retract speed brakes—panels that increase wing-surface area—in an aborted landing means an aircraft can't climb quickly. Many airlines require co-pilots to verify speed-brake status if the plane misses a landing. 

3. Know Speed Limits

Flaps, which are extended to allow airplanes to remain aloft at slower speeds during takeoff and landing, can suffer motor damage if they are deployed while the airplane is traveling too fast. In addition to memorizing these speed limits, co-pilots at some airlines are required to call them out as the airplane prepares to land. 

4. Confirm Spoiler Deployment

Like speed brakes, spoilers are wing surfaces that diminish lift and are needed during landing, when an airplane must quickly shed speed. It is the co-pilot's job to confirm that spoilers have been deployed during a landing to prevent the plane from overshooting the runway. 


Passengers usually feel relief when their plane touches down. But those peering out the windows of Colgan 3268 this May were horrified to see a wheel rolling away from their airplane during an otherwise routine landing. The end of an axle in a wheel bearing snapped as the Q400 Bombardier screeched across the runway—and as a passenger shot a cellphone video (left) of the chilling event. The airplane safely landed on its remaining tires. Investigators found that the wheel bearing failed after it overheated during the landing. Wheel bearings are just a few of thousands of parts that endure the stress of repeated takeoffs, flights and landings. Maintainers and designers constantly adopt new materials and inspection devices to prevent heavily stressed parts of planes from failing during flights. 


 

1. Wheel Bearings

Wheel bearings support the entire weight of the aircraft on a surface area of a few square inches, and during a landing they accelerate from 0 to 2000 rpm in less than 1 second. Ball bearings made from new ceramic formulas can better resist the temperature changes and physical stresses of these conditions. 

2. Wing Spars

Stress on the wing is borne by the spars. Boeing's 787 Dreamliner is the first civilian airplane to use carbon composites to form spars, but designers added extra metal fasteners to stiffen the wings after tests showed they couldn't handle the FAA's maximum aerodynamic load limits. As with other composite parts, crews use ultrasound to seek early signs of failure. Resin-filled nano- structures embedded in the material could patch cracks as soon as they form. 

2. Wing Skin

Wings endure high pressures while generating lift; stress on the wings' metal skin tends to peak in areas where the wing connects to the fuselage. Wing skin is installed in panels held together with fasteners. Every hole or deformation that interrupts the skin makes it more susceptible to cracking, so maintenance crews inspect areas around the fasteners with ultrasound equipment for signs of weakness. Researchers at Sandia National Laboratories are designing paper-thin pressure sensors that continually monitor for cracks. 

4. Fuselage Skin

Aluminum fuselages are built to handle changes caused by cabin pressurization—which inflates and deflates the body of an airliner as much as a quarter of an inch—but tension stress still spreads across the entire fuselage. Windows, doors and rivet holes magnify this stress. Engineers understand metal fatigue, but new materials like carbon composites pose unique safety issues. Maintenance workers use ultrasound and other non invasive scanners to find deformations and fractures inside composite materials. 

Building a Safer Airport

(Illustrations by Dogo)

Doomed flight 4590 lifts off moments before crashing in Paris, July 2000. (Photograph by Associated Press)

At 2:42 pm on July 25, 2000, Air France 4590 roared down runway 26R at Charles de Gaulle International Airport in Paris, bound for New York with 109 passengers and crew onboard. As the supersonic jet accelerated for takeoff, it ran over a 17-inch-long strip of titanium that had fallen off the thrust reverser of a recently departed DC-10. The metal shredded one of the Concorde's tires, and the flying pieces ruptured and ignited a fuel tank. The plane crashed 2 minutes later, killing all onboard and four people on the ground. Investigators found the runway was unchecked for 12 hours before the crash. The accident highlighted a paradox: Some of the worst threats to aviation, including debris, vehicles and other aircraft, are located on the ground. 

1. Broadcast Tower

The FAA's Airport Surface Detection Equipment-X integrates data from an inbound plane's GPS unit and the transponder signals from ground vehicles and other planes in the air to generate a continuously updated map of all airport traffic. Remote towers capture and relay information from airplanes in flight. ASDE-X, which alerts air traffic controllers to an impending conflict, is already in use at 20 U.S. airports; the FAA plans to install it in 15 more by 2011. 

2. Cockpit Digital Maps

Paper maps keep pilots out of trouble, but they need to be updated regularly. Digital maps of airports and the surrounding areas are more easily amended to include new obstacles and infrastructure. Pilots carry laptop-size computers called Electronic Flight Bags that plug into the cockpit navigation system. New EFBs alert users to update maps using Wi-Fi. 

3. High-Frequency Radar

Detectors use sensitive radar with wavelengths as tight as a millimeter to spot debris as small as a bolt that could cause crashes; some systems have cameras that compare images to a database of common objects, distinguishing grass or paper from more dangerous obstacles. 

4. Runway Status Lights

Modern versions of runway lights—which guide pilots, particularly at night or in bad weather—act like traffic lights: Red means a runway is in use; green means a runway is clear for takeoff, landing or crossing.