American Airlines Flight 1400

American Airlines Flight 1400

Aircraft involved after the accident.
Accident
Date	September 28, 2007 (2007-09-28)
Summary	American Airlines personnel used an unapproved method to start the left engine, subsequently resulting in an engine fire
Site	St. Louis Lambert International Airport, United States 38°44′50″N 90°21′41″W
Aircraft
Aircraft type	MD-82
Operator	American Airlines
Registration	N454AA
Flight origin	St. Louis Lambert International Airport
Destination	O'Hare International Airport
Occupants	143
Passengers	138
Crew	5
Fatalities	0
Injuries	0

American Airlines Flight 1400 was a regularly scheduled flight from St. Louis Lambert International Airport to O'Hare International Airport. On September 28, 2007, the McDonnell Douglas MD-82 operating the flight experienced an engine fire following their departure from the ground, as well as a partial hydraulic and electrical failure.

No injuries were reported among the 138 passengers and crew, but the aircraft was significantly damaged. During the investigation, it was revealed that the captain and ground crew had started the engine using an unapproved method.

Aircraft and crew

The aircraft was a McDonnell Douglas MD-82, registration number N454AA, manufacturer's serial number 49559. The aircraft was manufactured at Long Beach on February 28, 1988 and was owned and operated by American Airlines. The aircraft was equipped with two Pratt & Whitney JT8D turbofan engines. At the time of the accident, it had accumulated 57,744 total flight hours and 30,254 total flight cycles.^a The aircraft had previously experienced a landing gear failure at John F. Kennedy International Airport on September 2, 2003.

The captain of the flight, age 59, was hired by American Airlines on August 6, 1990. He held a multiengine airline transport pilot certificate, issued July 5, 2001, with type ratings in Boeing 707, 757, 767, 777, and DC-9 airplanes.^b The captain held a first-class Federal Aviation Administration (FAA) airman medical certificate, dated March 5, 2007, with the limitation that he "must wear corrective lenses; possess glasses for near/intermediate vision." The captain had accumulated about 14,000 total flight hours, including 831 hours as a captain in MD-80 airplanes.

The first officer of the flight, age 43, was hired by American Airlines in January 1999. He held a multiengine commercial pilot certificate, issued November 28, 2005, with no type ratings. He had DC-9 second-in-command privileges. The first officer held a first-class FAA medical certificate, dated March 19, 2007, with no limitations. He had accumulated about 7,000 total flight hours, including 3,000 hours as a first officer in MD-80 aircraft.

Accident

At 1:13 CDT, the aircraft experienced a in-flight left engine fire during departure climb from St. Louis-Lambert International Airport. During its return, the nose landing gear failed to extend, and the flight crew executed a go-around, during which the crew extended the nose gear using the emergency procedure. The flight crew conducted an emergency landing at 1:32 with the "left engine still slightly on fire and main landing gear doors hanging open." The 2 flight crewmembers, 3 flight attendants, and 138 passengers deplaned on the runway.

Investigation

Schematic of the engine start system for the MD-82.

The NTSB initiated an investigation of the accident and issued its final report on April 7, 2009. The MD-82 was equipped with a Pratt & Whitney JT8D engine ignition system, which utilizes a pneumatic air turbine starter to transform compressed air into rotational energy adequate to initiate engine acceleration. At the moment of the incident, the set inspection period for the ASTV was insufficient.

The MD-82's system features an ATSV that is outfitted with an air filter, a switch for starting the engine, and a pneumatic line). The ATSV was a butterfly-type valve operated pneumatically and controlled electrically. In the event that the electric start fails, onboard technicians can use a lever arm that includes a manual override button. The ATSV filter consists of an inner screen made of a coarse stainless steel filter and an outer screen made of a finer stainless steel mesh. The ATSV filter consists of an inner screen made of a coarse stainless steel filter and an outer screen made of a finer stainless steel mesh.

Schematic of the ATSV of the MD-82.

The components of the ATSV air filter assembly were taken out from the charred engine and inspected by the NTSB. The filter element was discovered broken close to the fitting brazing joint, and a large portion of its material was absent.

The leftover material was discovered stuck to the inner side of the filter housing. Inspection of the manual override button and ball valve housing showed that the override button was bent into an S-shape at the pin end nearest the ball valve, and the pin end was distorted with a concave dent, indicating that someone may have attempted to use a pry bar on it.

At that time, the airline’s MD-80 Maintenance Procedures Manual included a single approved engine-start method, indicating that maintenance staff needed to utilize an authorized, specialized wrench to turn the wrenching flats on the top of the butterfly valve shaft and ask the flight crew to engage the engine-start switch. In interviews after the accident, mechanics expressed that the authorized procedure was “extremely time-consuming” and might take approximately 20 to 40 minutes to complete since the necessary wrench was not included in the standard toolkit. Thus, they often opted to employ a “prying tool” to access, press, and maintain pressure on the ATSV’s manual override button, found through a small panel situated on the front lower cowl door.

Investigators concluded that the ASTV filter component broke apart, causing the end cap to loosen, which obstructed air flow and led to the engine's failure to start. Harm to the override button due to a pry bar led to the ATSV opening unexpectedly during the high-power engine phase at the start of the takeoff roll, which caused the air turbine starter to freewheel until it experienced a catastrophic internal failure. The open ATSV and the consequent malfunctioning air turbine starter enabled a hotter than usual airstream to enter the engine nacelle region and probably served as the ignition source for the in-flight fire.

Notes

^a An airplane cycle is one complete takeoff and landing sequence.

^b The MD-80 aircraft is a version of the DC-9, thereby allowing him to pilot both.