National Transportation Safety Board

This publication presents the record of aviation accidents involving revenue operations of U.S. Air Carriers including Commuter Air Carriers and on Demand Air Taxis for calendar year 1991.

The report is divided into three major sections according to the federal regulations under which the flight was conducted - 14 CFR 121, 125, 127. Scheduled 14 CFR 135, or Nonscheduled 14 CFR 135. In each section of the report tables are presented to describe the losses and characteristics of 1991 accidents to enable comparison with prior years.

Richard L. Smith

The purpose of this report is to describe the National Institute of Standards and Technology’s work to date relating to the general methodology being developed for the project Risk Analysis for the Fire Safety of Airline Passengers and the software being used to facilitate this methodology. The approach selected involved the use of influence diagrams. Therefore, a brief discussion of influence diagrams is given. The status of their application to the water mist system for passenger planes is given and the overall approach to carrying out the project is described. An example is included hat shows how the process works, but the case is fictional, not intended to be realistic.

Dung Do, Joseph Wright, Lawrence Hampton

Tests of the burn characteristics of a phenolic foam, under evaluation as a runway brake arrestor material, were conducted by the Fire Safety Branch of the Federal Aviation Administration (FAA) Technical Center.

The purpose of these tests was to assess the fire propagation properties of phenolic foam when exposed to a free burning Jet A fuel fire and to determine the fire control time of phenolic foam immersed in a jet fuel fire when extinguished using 3-percent Aqueous Film Forming Foam (AFFF).

Three pool fire tests were conducted as follows: In the first and second tests, a 12-foot-square bed of phenolic foam. material was placed adjacent to a 35-foot-diameter jet fuel fire. This configuration resulted in ignition and flame propagation across to adjacent foam material, resulting in charring of over 30 percent of the exposed surface of the phenolic foam.

In the third test, the phenolic foam material was immersed in the jet fuel fire to determine ease of extinguishment using conventional AFFF agent. The fire control time was three times longer than when the phenolic foam material was absent. The extinguishing time was an order of magnitude higher than that without the foam.

In addition, the phenolic foam material was evaluated on the basis of FAA fire test requirements for cabin materials. These small-scale tests measured burn length, weight loss, and heat release rates of the foam material in accordance with Federal Aviation Regulation (FAR) 25.853. These results showed the foam material passed the burn test requirements.

Timothy Marker

Twelve full-scale tests were conducted in a modified Metroliner fuselage to study the impact of using improved fire retardant materials and a cabin water spray system on postcrash fire survivability. Currently, computer category aircraft as defined in Part 23 are exempt from meeting the stringent Federal Aviation Regulations (FAR’s ) requiring seat cushion fire blocking layers and low heat/smoke release panels in large transport aircraft.

A zoned cabin water spray system switch allowed for the individual activation of spray zones depending on cabin temperature was designed and installed in the fuselage. The system consisted of four 100 inch long zones, each system containing 6 nozzles. Of the twelve tests, five were run with the water spray system and a different combination of cabin materials. These five tests were repeated without the water spray system in order to establish baseline data for each material combination.

Two additional tests were conducted to investigate the impact of a partially obstructed forward exit and also to evaluate the effect that the channel-type floor geometry used in the Metroliner aircraft has on flame propagation during a cabin fire. Temperature, smoke levels, and gas concentrations were continuously monitored at a forward cabin location and each test was recorded on video.

Thomas L. Reynolds, Kent Porter

The concept of utilizing a cabin water spray system (CWSS) as a means of increasing passenger evacuation and survival time following an accident has received considerable publicity and has been subject to testing by the regulatory agencies in both the United States and Europe.

A test program, initiated by the CAA in 1987, involved the regulatory bodies in both Europe and North America in a collaborative research effort to determine the benefits and “disbenefits” (disadvantages) of a CWSS.

In order to obtain a balanced opinion of an onboard CWSS, NASA, and FAA requested the Boeing Commercial Airplane Group to investigate the potential “disbenefits” of the proposed system from the perspective of the manufacturer and an operator. This report is the result of a yearlong, cost-sharing contact study between the Boeing Commercial Airplane Group, NAAA and FAA.

Delta Air Lines participated as a subcontract study team member and investigated the “return to service” costs for an aircraft that would experience an uncommanded operation of a CWSS without the presence of fire. Disbenefits identified in the report include potential delays in evacuation, introduction of “common cause failure” in redundant safety of flight systems, physiological problems for passengers, high cost of refurbishment for inadvertent discharge, and potential to negatively effect other safety systems.