- Avianca Airlines B707 Flight 52 at Long Island, NY
- Accident Overview
- Accident Board Findings
- Accident Board Recommendations
- Relevant Regulations / Policy / Background
- Prevailing Cultural / Organizational Factors
- Key Safety Issue(s)
- Safety Assumptions
- Resulting Safety Initiatives
- Airworthiness Directives (ADs) Issued
- Common Themes
- Related Accidents / Incidents
- Lessons Learned
- Avianca Airlines B707 Flight 52 at Long Island, NY
Resulting Safety Initiatives
This accident was a landmark for the international adoption of English as the standard language of aviation. The FAA worked with ICAO to start an English language initiative and eventual requirement for all flight crews to be proficient in the English language to a minimum ICAO standard. The English language standard is detailed in AC 60-28 which references the ICAO requirement. The FAA regulation that drives the requirement is 14 CFR 91.703.
This accident was also the impetus for the creation of FAA International Safety Audits. The audits are reviews of Civil Aviation Authorities (CAA) capabilities (International equivalent of the FAA for each country) vs. eight key criteria. The DAAC was the first CAA to be audited and was found deficient in several areas which were fixed subsequently.
The FAA ATC incorporated into air route traffic control centers equipment to provide a recorded broadcast of traffic management information that can be monitored by all aircraft within each center's boundaries to provide pilots with early indications of potential delays en route.
FAA ATC management of all air traffic control facilities formally briefed all air traffic controllers on the circumstances of the accident, and emphasized the need to request from flightcrews clarification of unclear or ambiguous transmissions that convey a possible emergency situation or need for additional ATC assistance.
This accident highlighted the value of the new 14 CFR 25.562 dynamic seat rule which was released in 1986. The rule required newly designed transports to use seat installations certified to the new 16g dynamic load standard. The accident airplane had only 9g static seat installations certified to the previous 14 CFR 25.561 emergency load conditions.
Avianca Airlines mandated CRM training for all crews.
Illustration of early seat design
Wicker passenger seats on a 1929 Hamilton Metalplane
Photo copyright Philip Makanna and H.S. Wright III - used with permission
History of Seat Standards
From 1956 until 1988 Transport category airplane seats were designed to meet the standards contained in 14 CFR 25.785 (seats, berths, safety belts, and harnesses), in14 CFR 25.561 (Emergency landing conditions), and in Technical Standards Order (TSO) C39b (Seats). 14 CFR 25.785(a) requires that each seat (including a crewmember seat as well as a passenger seat), berth, safety belt, harness, and adjacent part of the airplane be designed such that the occupant who experiences the inertial forces specified in 14 CFR 25.561 will not suffer serious injury in an emergency landing. The inertial forces in 14 CFR 25.561(b) are specified as ultimate forces experienced by the occupant and are treated as statically applied loads. The seats produced these standards are known as 9g seats.
Airplane Structure vs. Seat Strength Research
An evaluation of the crash dynamic characteristics of transport category airplanes indicates that the present Part 25 requirements, with a few exceptions, provide adequate protection for the occupants. A review of existing accident data has shown that, for survivable accident scenarios, the airplane structure remains substantially intact and provides a livable volume for the occupants throughout the impact sequence. This finding was confirmed by the results of the FAA/NASA controlled impact demonstration (CID) involving a remotely controlled, fully instrumented transport category airplane.
Video - FAA/NASA CID montage
Video - FAA/NASA CID test outside
Photo of FAA/NASA CID full scale remotely piloted crash test of B707 transport airplane
Photo of FAA William J. Hughes Technical Center Vertical Drop Test facility
Pretest setup photo of a transport aircraft fuselage section with several rows of seats at Transportation Research Center of Ohio
Fuselage section drop tests
The FAA’s Dynamic Vertical Drop Test Facility, is located at the FAA William J. Hughes Technical Center, in Atlantic City, New Jersey. It is used to obtain test data needed to set crashworthiness standards. It has been used to conduct vertical impact tests on a series of transport category airplane fuselage sections of airplanes such as the Boeing 737. The tests are conducted to determine the impact response characteristics of items including seats/occupants to assess the adequacy of their design standards and regulatory requirements.
Video - fuselage drop test real time
Video - fuselage drop test slow motion
Longitudinal Impact Testing
Longitudinal impact tests of a fuselage section with several seat rows were conducted at the Transportation Research Center of Ohio. The goals accomplished were:
- Measured the response of the seats and airframe structure to simulated crash loads.
- Evaluated the 16g forward test method.
- Found that the airplane structure could successfully take the loading from several seats in a dynamic test even though airplane is designed for 9 static loading.
Studies of Accident Data
From preliminary review of accident data, it was found that incidents of undesirable seat performance were usually related to cabin floor displacement and excessive lateral inertial loads. From those studies, it became evident that the identified seat deficiencies could be eliminated by establishing dynamic test standards providing the same level of impact injury protection and structural performance as that provided by the airplane structure itself. In this regard, dynamic test standards representative of two distinct survivable impact scenarios were developed. These standards, which are defined in the form of cabin floor pulses and respective performance standards, provide a means of demonstrating the occupant impact protection feature of seats and ensure that the level of safety provided by the seats is consistent with that provided by the airplane structure.
16g Dynamic Seat Rule
Photo of 14g structural plus lumbar load test setup
Example 16g structural test setup showing pretest simulated floor deformation
Rulemaking upgraded the static load factors defined in 14 CFR 25.561 in the upward, downward, and sideward directions, and to add an aft direction requirement. Rule 14 CFR 25.562 added dynamic test standards for seats. The standards would require the demonstration of both occupant response and seat/restraint system structural performance. They provide a more representative evaluation of the interaction of the occupant, the seat, and the restraint system and yield data for impact injury analyses.
Two Dynamic Test Conditions Added: 16g Forward and 14g Down
Two dynamic test conditions were selected based on impact scenarios developed from analyses of survivable ground impact data. One test condition combines vertical and longitudinal loads to simulate ground impact following a high-rate vertical descent. This test condition emphasizes occupant vertical loading and evaluates the means provided to reduce spinal injury under the loads typically resulting from an impact of this nature.
The second test, with a predominantly longitudinal component, simulates horizontal impact with a ground-level obstruction. This test condition provides an assessment of the occupant restraint system and seat structural performance. The selection of these two dynamic test conditions is consistent with the results of the crash scenario studies. These dynamic test standards are considered appropriate for all transport category airplanes, regardless of size.
Video – Example 16g forward structural test on business class seat. Notice that the seat attachment fixture applies simulated floor deformation to the seat. In this way the seat is proven to stay attached even when the floor under it is deformed during a crash.
Video - Top view of 16g forward structural test on business class seat . Notice that the seat is yawed vs. the direction of travel to account for airplane yaw during the impact sequence.
Injury Criteria Tests Added
An important part of any test procedure is the pass or fail criteria. The rule established such criteria by defining standards that directly relate selected parameters measured during a dynamic test to injury criteria based on human impact injury limits. The performance criteria are used to evaluate the occupant/seat protection system potential for preventing or minimizing serious injuries from both primary and secondary impacts. Of major concern are secondary head impacts which can inflict debilitating injuries and result in concussion and unconsciousness. The measure of potential head injury proposed in the notice is the Head Injury Criteria (HIC) used in Federal Motor Vehicle Safety Standard No. 208 (49 CFR 571.208). The HIC is applied where the results of the seat dynamic tests show that structure or other items of equipment are within the occupant's head strike envelope. The head acceleration time history is measured during the dynamic test and evaluated with the HIC when secondary impact can occur.
The two videos below feature a comparison of an inflatable lap belt (airbag) equipped seat place vs. one without. Inflatable lap belts that deploy an airbag to protect passengers from head injury are a relatively new development.
The left foreground shows an example of post accident deformed floor. The 16g seat rule requires that the seats and seat floor attachments accommodate this type of deformation without breaking loose during the 16g test. Photo from accident investigation.
Video monitor is an example of a seat item of mass that must be retained (not break loose) during a 16g test
Spinal injuries also occur in airplane crashes. Additional testing with transport category airplane seats with a lap belt restraint system indicated that the pelvic load peaks while the anthropomorphic dummy is still seated in a predominantly upright position. These tests confirm that the spinal load injury criteria can be used in assessing the dynamic performance of transport category airplane seats. Pelvic loads can be used in assessing the probability of spinal injury, and they are straight forward, easily measured, and require no additional analysis or interpretation. A maximum pelvic load of 1500 pounds would assure a low probability of spinal injury.
Video – Example 14g structural plus lumbar load seat test
Leg injuries also occur in airplane crashes. While leg injuries alone may not be fatal, passengers may be temporarily incapacitated to the extent rapid evacuation of the airplane is not possible. An injured passenger, in an effort to escape, may block the escape route for several other passengers. Femur loads should therefore be measured during the dynamic tests where leg injuries may result from contact with seats or other structure. A measured axial load of 2250 pounds along each femur should not be exceeded during these tests. This is the same as the maximum allowed by Federal Motor Vehicle Safety Standard No. 208. This procedure provides an easily measured quantity that would require no additional analysis or interpretation.
In both videos note the heavy knee impact which loads the femurs.
Crash investigations have shown that localized cabin floor deformation can occur in survivable crashes. This has been confirmed by the controlled impact demonstration and drop test involving transport category airplanes. The inability of some seats to accommodate such deformations, remain in place and restrain the occupants can contribute significantly to the degree of injury during a crash. The simulated floor deformation used in the dynamic tests, while not intended to be a measure of floor strength or deformation capability, will demonstrate the tolerance of the seat and its attachments to deformations that could occur in an actual crash.
The static strength requirements of 14 CFR 25.561(b)(3) were increased to provide a level of safety for seats and fixed items of mass consistent with dynamic tests standards and accepted industry practice. It is expected that increased static strength requirements will assure a more uniform level of safety in the cabin floor structure, seat tracks, fittings, fixed items of mass, and in the seats. The increased lateral static strength and the added rearward static strength requirements would also improve the conditions for rapid evacuation during an emergency landing by limiting the obstruction of aisle space.
Section 25.561(d) and a corresponding provision in 14 CFR 25.562 was added to clarify that the rapid evacuation of occupants following impact must not be impeded by structural deformation.
In summary, this amendment increases the capability of the occupant seat and restraint system of transport category airplanes to absorb a crash impact and to provide occupant protection from items of mass that may become loose on impact.
These seat safety standards apply to all transport category airplanes for which an application for type certificate is made on or after the effective date, regardless of whether the airplanes are used in air carrier service as if 1988. It is also applicable to newly manufactured airplanes as of October 27, 2009.
Screen shot from simulation video
Research on crash dynamics continues. Here are figures and video showing an example of state of the art modeling of an entire transport airplane including seats and passengers in a survivable crash event. This model has been validated extensively using test, analysis, and recorded results from a similar crash event. (Provided courtesy of Gerardo Olivares, Ph.D., National Institute for Aviation Research (NIAR), R & D Crashworthiness Group.
Here is a video simulation of a crash event using the model.
Screen shot from crash simulation