The National Transportation Safety Board (NTSB) provided an update regarding the continuing investigation into the mid-air rupture of the fuselage skin on Southwest Airlines flight 812 that occurred on Friday, April 1st. The aircraft made an emergency landing in Yuma, Arizona.
Today, mechanics from Southwest Airlines, under the supervision of NTSB investigators, removed a section of the ruptured fuselage skin from Friday’s accident. The segment will be transported to NTSB headquarters in Washington, D.C. for in-depth analysis.
In addition, NTSB investigators conducted additional inspections of other portions of the lap joint along the fuselage of the accident airplane and found evidence of additional cracks.
The past few days, Southwest Airlines has been conducting additional non destructive testing inspections on several of their 737 airplanes. We have been informed that additional crack indications in the lap joints have been identified on 3 airplanes they have inspected.
The NTSB, along with the other investigative parties – FAA, Boeing, and Southwest Airlines – has been working to determine what actions might be necessary to inspect any similar airplanes.
As a result of the findings from our investigation to date and the results of the Southwest Airlines inspections, Boeing has indicated that they will be drafting a Service Bulletin to describe the inspection techniques that they would recommend be accomplished on similar airplanes.
While the specifics of the Service Bulletin are being developed, the focus is to require inspection of the left and right lap joints on all similar 737 airplanes that have comparable cycles (takeoffs and landings) as the accident airplane. Once the Service Bulletin is released by Boeing, the FAA will make a determination whether to make it mandatory for all similar 737 airplanes.
Today the National Transportation Safety Board adopted a study that concluded that general aviation (GA) airplanes equipped with airbags provide additional protection to occupants in accidents involving survivable forward impacts.
Airbags are designed to mitigate head and upper body injuries and are installed in the lap belt or shoulder harness portions of the restraint system. They were first approved for use in the pilot and co-pilot seats in GA aircraft in 2003. Currently, there are nearly 18,000 airbag-equipped seats in over 7,000 of the 224,000 GA aircraft in the United States.
“Although airbags have been mandated in automobiles for over a decade, the aviation industry has no such requirement for small aircraft,” said NTSB Chairman Deborah A.P. Hersman. “The good news is that over 30 manufacturers have stepped up to the plate and offer airbags as standard or optional equipment.”
The study, which examined 88 accidents involving airbag-equipped airplanes that occurred between 2006 and 2009, found no instances where the airbag caused harm in properly restrained occupants. In addition, the study found 10 survivable accidents in which the crash forces were severe enough to cause injury and/or to deploy the airbag.
Within the group of 10 accidents, 12 occupants experienced airbag deployments, and the study found that the airbag likely mitigated injuries for two of the occupants.
The study also noted that there were no negative consequences as a result of airbag deployments. For instance, there were no cases in which the airbags were expected to deploy but did not. Nor were there any cases that involved airbags deploying under unexpected circumstances, hindering egress, fueling post-crash fires or interfering with rescue attempts. Yet investigators did uncover some safety issues with restraint systems.
One such issue involved the incorrect usage or adjustment of seat belts. In certain aircraft types, the seat belts in the left and right seats can become reversed, which could result in the wrong airbag being activated if only one of the seats is occupied.
There were also concerns with optimal airbag protection for occupants whose body mass indexes (BMI) classified them as either overweight or obese (BMIs of 25 or higher). The NTSB questions whether the airbag-equipped restraints were designed and tested with the high-BMI population in mind.
An additional finding of this study was the strong affirmation that correctly installed shoulder harness/lap belt combinations provide significantly greater protection in GA accidents than that offered by a lap belt alone. Based on an analysis of over 37,000 GA accidents, the Board concluded that the risk of fatal or serious injury was 50 percent higher when an occupant was only restrained by a lap belt as compared to the combination lap belt and shoulder harness.
“The simplest and cheapest improvement to the safety of general aviation aircraft occupants is the mandatory installation of shoulder harnesses,” said Hersman.
The five-Member Board voted to adopt six safety recommendations, all directed to the Federal Aviation Administration:
Require manufacturers to modify restraint systems vulnerable to being used incorrectly in newly built GA airplanes and to modify restraints in existing airplanes.
Revise the guidance and certification standards for restraint systems to reduce the likelihood of misuse. Modify the guidance to GA airbag manufacturers as to how they should demonstrate that an airbag design provides adequate protection for a greater range of body sizes, including very small and very large individuals.
Require the retrofitting of shoulder harnesses on all general aviation airplanes that are not currently equipped with such restraints.
Evaluate the feasibility of requiring airbag-equipped aircraft to capture and record crash dynamics data to determine whether the system performed as designed.
Develop a system to track safety equipment, such as restraint systems, airbags, and aircraft parachutes, designed to improve crash outcomes.
The complete safety study will be available on the NTSB website in several weeks.
Midair Collision Over Hudson River NTSB Sunshine Meeting
Washington, DC – The National Transportation Safety Board today determined that the probable cause of last year’s midair collision over the Hudson River that resulted in the deaths of all nine persons aboard the two aircraft were the inherent limitations of “see-and-avoid” concept and a Teterboro Airport air traffic controller’s nonpertinent telephone conversation at the time of the collision. The see-and-avoid technique of averting mid-air collisions was not effective because of the difficulty the airplane pilot had in seeing the helicopter until the final seconds before the collision. In addition, the Teterboro Airport local controller engaged in a personal telephone conversation, which distracted him from his air traffic control duties, including the timely transfer of communications for the accident airplane to the Newark Liberty International Airport (EWR) tower and correcting the airplane pilot’s incorrect read-back of the EWR tower frequency.
The Safety Board met today in a five-hour public meeting to determine the probable cause of the accident and issued five recommendations to the Federal Aviation Administration for improving the safety of the national airspace, and in particular, the airspace over the Hudson River near New York City. The Safety Board noted that contributing to the cause of the accident were the ineffective use by both pilots of their aircrafts’ electronic advisory system to maintain awareness of other air traffic, FAA’s procedures for transfer of communications among air traffic facilities near the Hudson River, and FAA regulations that did not provide for adequate vertical separation of aircraft operating over the Hudson River.
On August 8, 2009, a Piper PA-32R-300 airplane, N71MC, and a Eurocopter AS350BA helicopter, N401LH, operated by Liberty Helicopters, collided over the Hudson River near Hoboken, New Jersey. The airplane flight was operating under the provisions of 14 Code of Federal Regulations (CFR) Part 91, with a pilot and two passengers. The helicopter flight, which carried a pilot and five passengers, was conducting an air tour of the area under the provisions of 14 CFR Parts 135 and 136. No flight plans were filed or were required for either flight, and visual meteorological conditions prevailed at the time of the accident.
“This collision could have been prevented,” NTSB Chairman Deborah A.P. Hersman said. “While traffic alerts go a long way in helping pilots “see and avoid” other aircraft, these technologies are not, in and of themselves, enough to keep us safe. Strong operating procedures, professionalism, and commitment to the task at hand — these are all essential to safety.”
As a result of the accident investigation, the NTSB made recommendations to the FAA regarding changes within the special flight rules area (SFRA) surrounding the Hudson River corridor; vertical separation among aircraft operating in the Hudson River SFRA; see-and-avoid guidance; and helicopter electronic traffic advisory systems.
A synopsis of the Board’s report, including the probable cause, conclusions, and recommendations, is available on the NTSB’s website, at http://ntsb.gov/Publictn/2010/AAR1005.html. The Board’s full report will be available on the website in several weeks.
