TACA Flight 110

TACA Flight 110 was an international scheduled airline flight operated by TACA Airlines, traveling from Belize to New Orleans. On May 24, 1988, the flight lost power in both engines but its pilots made a successful deadstick landing on a grass levee, with no one aboard sustaining more than minor injuries.

Aircraft history
The aircraft, a Boeing 737-3T0 (tail number N75356, serial number 23838), had first flown on 26 January 1988, and had been in service with TACA for about two months. On this day, the flight proceeded normally, taking off from Belize City's Philip S. W. Goldson International Airport and flying over the Gulf of Mexico toward the Louisiana coast.

This airliner was the 1,505th Boeing 737 manufactured, and was owned by a previous operator before TACA acquired it in May 1988. The airframe is currently operated by Southwest Airlines, and has been operated by six airlines (including TACA):

Accident
Investigation by the National Transportation Safety Board (NTSB) revealed that during descent from FL 350 (35,000 feet / 11,000 metres) in preparation for their impending arrival at New Orleans' Moisant Field, the pilots noticed areas of light to moderate precipitation in their path, depicted as green and yellow areas on their weather radar, as well as "some isolated red cells" indicative of heavy precipitation to both sides of their intended flight path.

The flight entered clouds at FL 300 ((30,000 feet / 9,100 metres), the crew selecting "continuous ignition" and turning on engine anti-ice to protect their turbofan engines from the effects of precipitation and icing, either of which is capable of causing a flameout, where the engines lose all power. Despite flying a route between the two areas of heavy precipitation shown on radar, they encountered heavy rain, hail, and turbulence. Passing through 16,500 feet (5,000 m), both engines flamed out, leaving the jet gliding with neither engine thrust nor electrical power. The auxiliary power unit (APU) was started as the plane descended through 10,500 feet (3,200 m), restoring electrical power. While attempts to "windmill start" the engines using the airflow generated by the plane's descent were unsuccessful, the pilots were later able to start them using the engine starters which were powered by the APU. However, neither engine would accelerate to normal idle speed, much less to a point where it was producing meaningful thrust. Attempts to advance the throttles only resulted in overheating of the engines, so they were once more shut down to avoid catastrophic failure. The pilots landed the airliner on a narrow grass levee at NASA's Michoud Assembly Facility in the Michoud area of eastern New Orleans, bringing the airplane to a safe stop.

Investigation and recommendations
NTSB investigators determined that the aircraft had inadvertently flown into a level 4 thunderstorm and that water ingestion had caused both engines to flame out despite their being certified as meeting Federal Aviation Administration (FAA) standards for water ingestion. The aircraft suffered mild hail damage, and its right-side (number 2) engine was damaged from overheating.

Initially, it was planned to remove the wings and transport the airplane to a repair facility by barge, but Boeing engineers and test pilots decided to perform an engine change on site and to take off from the adjacent paved access road. The 737 was flown to the Moisant Field where further maintenance work was performed. The plane was then returned to service.

The investigation concluded that the engines had failed "as a result of an inflight encounter with an area of very heavy rain and hail. A contributing cause of the incident was the inadequate design of the engines and that the FAA's water ingestion certification standards did not reflect the waterfall rates that can be expected in moderate or higher intensity thunderstorms."