The first generation of jet airliners revolutionized air travel with their speed and comfort when they entered service in the late 1950s. But their takeoff and landing speeds limited them to large airports with long runways, and with four fuel thirsty jet engines their operating costs and efficiency were far from ideal.
The Boeing 727 inaugurated the second generation of American jet transports. Powered by three turbofan engines, it offered the potential for cost-effective jet service to a much wider range of cities with smaller airports that could only handle propeller aircraft up to that time. To achieve this, the 727 relied on an advanced wing design incorporating a sophisticated triple-slotted flap system which effectively increased the wing area by 25 per cent for landings, allowing lower landing speeds as well as the high cruising speeds the public expected with jet travel.
First flown in 1963, the 727 was ordered by the major U.S. airlines and began scheduled airline service in early 1964. It quickly became popular with air travelers by bringing jet service to many more cities, with the airlines for its economy and efficiency, and with pilots for its good performance and handling qualities. Then a series of fatal accidents changed that bright picture.
On August 16, 1965 United Air Lines Flight 389 plunged into Lake Michigan while descending for landing at O’Hare. On November 8, 1965, American Airlines Flight 383, crashed during its approach to Greater Cincinnati airport, killing 62 of 66 passengers and crew on board. Three days later, United Air Lines Flight 227 crashed on landing at Salt Lake City International Airport, killing 43 of 91 aboard. And on February 4, 1966, an All Nippon Airways 727 crashed into the sea on approach to Haneda Airport at Tokyo.
The reaction was swift and dramatic. Travel agencies requested the airlines to cancel 727 bookings. Some major corporations ordered their employees to avoid 727 flights. Congressional claims erupted that the design was unsafe, and demands followed that all 727s should be grounded. In response, the Civil Aeronautics Board (the CAB, which was responsible for investigating air accidents and making safety recommendations at that time) undertook a review of the 727’s airworthiness, aerodynamics and flight characteristics. It also requested the National Aeronautics and Space Administration to review the 727 design data. And the Federal Aviation Agency (FAA) convened a meeting of 727 operators to review their operating procedures and training.
The result of these reviews was a conclusion that the 727 was airworthy and properly certificated. However, the CAB found that pilots were making unstabilized, high descent rate approaches more often in 727s than in any other jet transport—a practice that was facilitated by the 727’s sophisticated flap system, which allowed excessive sink rates to develop if approaches were not carefully monitored.
While these reviews were in progress the CAB issued its report on the Cincinnati accident. It found the probable cause to be failure of the crew to properly monitor the altimeters during a visual approach in deteriorating weather conditions. The flight data recorder showed a high airspeed and a decent rate of more than 2,000 feet per minute in the final stages of the approach, far in excess of the permitted maximum. Similarly, the CAB found that the probable cause of the Salt Lake City crash was the captain’s failure to take timely action to arrest an excessive rate of descent during the landing approach.
In response, the FAA required the airlines to make changes to their training procedures and their flight manuals to stress the importance of stabilized approaches.
The landing accidents ended. The 727 went on to compile an admirable operational and safety record, and remained in production for over 20 years until superseded by the Boeing 757 in the 1980s. The first 727 produced was flown to the Museum of Flight in Seattle and put on display in March, 2016. The history of the Boeing 727 is a reminder of the importance of avoiding a rush to judgment in the wake of air accidents.