David Blake

The purpose of this project was to evaluate how smoke detection times are affected when the same quantity of smoke is released in either an empty or fully loaded cargo compartment. It also evaluated the effect on smoke detection times from active cargo containers that produce additional airflow patterns. Active containers are equipped with climate control systems that maintain the container’s temperature and humidity for the duration of the flight. Tests were conducted in the main deck cargo compartment of a Boeing 727 and in the aft, below-floor cargo compartment of a B-747SP.

Although there was some variability in the test results, in general, the smoke detectors alarmed quicker in loaded compartments than in empty compartments. In addition, the operation of the active cargo containers did not have a consistent influence on smoke detection times for the airflow conditions tested.

Dhaval D. Dadia

An investigation into the fire safety of a wing fuel tank has been performed to aid in the effort to eliminate or reduce the possibility of a wing fuel tank explosion in a commercial aircraft. A computational model is built to predict the generation of flammable mixtures in the ullage of wing fuel tanks. The model predicts the flammability evolution within the tank based on in-flight conditions of a wing fuel tank. The model is validated through supporting experiments performed in an altitude chamber, the wind tunnel facility as well as data obtained from flight tests. The results from the experiments are compared to the computational results. Computational results from the altitude chamber follow the general trend of the experimental results, but produce them at a different flash point. This is due to the replenishment of species with lower flash point at the surface of the fuel which emulates the flash point of the entire fuel to be lower. Experimental results for the aluminum wing tests from the wind tunnel experiments are in good agreement with the computational results as well.

A simpler model is developed from a program that calculates fuel air ratio within the ullage of fuel tanks in order to reduce the required number of inputs to the model. This model is applied to the data sets for the experiments performed in the altitude chamber and wind tunnel. For the tests conducted in the altitude chamber, the correlation estimates the hydrocarbon concentrations extremely well during ascent and descent. During the on-ground condition the estimation is good, but not as accurate as the ascent or descent conditions. For the tests conducted in the wind tunnel, the computational values follow the general trend of the experimental values, but the computational values estimates the total hydrocarbon concentration approximately 10% lower than the experimental value consistently.

Flammability studies are also performed in order to track the effects of temperature, pressure, and oxygen concentration on the upper and lower flammability limits. For the temperature and pressure profiles considered in this work, it is found that the temperature and pressure effects on the flammability limits are minimal. In contrast, the oxygen concentration has a significant effect on the flammability limits of the vapor; the flammable region narrows with a decrease in oxygen concentration.

Robert Ian Ochs

This study has been performed to aid in the effort to minimize the possibility of a fuel tank explosion in a commercial aircraft. An understanding of the mechanisms behind fuel vaporization processes in an aircraft fuel tank is essential to developing accident prevention techniques. An experiment was designed to measure the conditions existing within a heated aluminum fuel tank, partially filled with JP-8 jet fuel, under varying ambient conditions similar to those encountered by an in-flight aircraft. Comprehensive fuel tank data, including all temperatures, pressure, and ullage hydrocarbon concentration, was obtained during testing, and is available for use to validate heat and mass transfer calculations. An existing model was employed in this work to calculate ullage temperature and ullage fuel vapor concentration in the tank and compare with measured values, to explain the transport processes occurring in the tank during testing, and to estimate the flammability of the ullage vapors existing within the tank. The calculations made by the model were in good agreement with the measured data. The model also gave a good indication of the temporal mass transport processes occurring in the tank and gave a reasonable assessment of the ullage vapor flammability in the tank.

Louise C. Speitel and Richard E. Lyon

A kinetic scheme was used to model the human blood concentration history of halocarbon extinguishing agents as a function of agent discharge amount, compartment size, ventilation rate, cabin pressure, and altitude of aircraft. This methodology recommends discharge limits of halon replacement extinguishing agents that produce maximum blood concentrations safely below the adverse effect level. This report provides the technical basis for an update of guidance on the use of hand-held fire extinguishers on aircraft contained in Federal Aviation Administration Advisory Circular 20-42C. Safe-use limits are established for halon replacement extinguishing agents by using an instantaneous blood concentration of halocarbon as a criterion for adverse effect instead of a critical dose (concentration-time product).

Stanislav I. Stoliarov, Sean Crowley, and Richard E. Lyon

This study provides a thorough examination of whether a numerical pyrolysis model, which describes transient energy transport and chemical reactions taking place in a one-dimensional object, can be used as a practical tool for prediction and/or extrapolation of the results of fire calorimetry tests. The focus is on noncharring polymers, in particular—poly(methylmethacrylate), high-impact polystyrene, and high-density polyethylene. First, relevant properties of these materials were measured and/or obtained from the literature. Subsequently, the values of these properties were used to simulate gasification and cone calorimetry experiments, which were performed under a broad range of conditions. A comparison with the experimental results indicates that the model gives reasonably good predictions of the mass loss and heat release histories. It also predicts the evolution of temperature inside the material samples.