Vulnerability Assessment of Aircraft: A Review of the Department of Defense Live Fire Test and Evaluation Program (1993)

Preliminary Recommendations from the Fuel System Working Panel of the 1991 JTCG/AS P_k/h Workshop:

• Develop the Ullage Explosion Model to calculate ullage vulnerability to explosions from API, HE, and fragment impacts.

• Reexamine the BRL Void Space Fire data to determine that the probabilities for fire due to fragments and 23-millimeter HE projectiles are consistent with other data.

• Modify the COVART model to handle the simultaneous analysis of thermal and mechanical damage to components.

• Determine how the BRL void space fire probabilities need to be modified for JP-5 and JP-8 fuel.

• Determine how the BRL void space fire probabilities will change from open to closed void spaces.

• Determine the probability of fire initiation due to “mixed functioning” of the incendiaries.

• Develop a methodology to determine the probability of fires due to secondary ignition sources.

• Develop data curves for the vulnerability of fuel system hardware components.

• Determine how the BRL void space fire probabilities will change if the “striker plate” consists of composite materials.

• Perform a test program to determine the probability of fire initiation due to a “mixed functioning” of the incendiaries.

• Determine if the burn characteristics of composite materials are sufficiently different to warrant a change in the BRL void space probability numbers.

• Determine how the altitude will affect the probability of fire initiation, the probability that fires will sustain, and the damage that might result from sustained fires.

• Determine and quantify the vulnerability of fuel system components due to directed energy weapons.

The following findings of the eight working panels are taken from a preliminary copy of a briefing being prepared to be given to the JTCG/AS Central Office and to OSD. This briefing material was furnished by Gerald Bennett, ASD/XRM, WPAFB.

• Empirically based fuel/fire/explosion P_k/h data exist that are

  1. more than 15 years old,

  2. for metallic structures only,

  3. for sea level only.

• No traceable fuel system hardware P_k/h data exist.

• Actuators

  1. Analyses are only on older (1950s) designs.

  2. Sparse test data do not match actuators analyzed.

  3. New designs and technologies have no analyses or tests.

• Hydraulic fluid reservoirs, and accumulators

  1. One set of experimentally validated fluid P_k/h data exists.

  2. Other components have no documented test data or analyses.

• Cables, bellcranks, and mechanical components

  1. Analytic models and some P_k/h data exist.

  2. Selective tests needed to validate analyses.

• Traceable crew P_k/h data are available for fragments and projectiles (toxic gases, overpressure, and burns not considered).

• JLF crew station tests will provide test data support.

• Ejection seat pyrotechnic P_k/h data are not available.

• Cockpit controls and displays P_k/h data are not available.

• Liquid oxygen (LOX) converter P_k/h estimates are of low confidence.

• Windscreen/canopy P_k/h data developed.

• For the on-board oxygen generating system (OBOGS), on-board inert gas generating system (OBIGGS), flat panel displays, there are no P_k/h or test data.

• P_k/h data have kept pace with new designs.

• Test data form important P_k/h input.

• Large analysis data base exists on obsolete and current designs.

• Confidence level is high for older/current designs (exceptions: large engines, fan sections, and small unguided-aerial-vehicle engines).

• Fuel ingestion analytical technique is available.

• Bombs and missile warheads

  1. Results are design and threat specific.

  2. Analyses predict burn and prompt reaction thresholds.

  3. Intermediate zone requires added tests.

• Propellant and rocket motors

  1. Results are design and threat specific.

  2. Analyses predict burn and prompt reaction thresholds.

  3. Complex propellants require added tests.

• Flares, ammunition drums, and ammunition boxes: limited test data and P_k/h estimates

• Most work (test and analysis) dates from 1983 or before.

• Component design technologies date from the 1950s and 1960s.

• A large test base exists, but for ballistic resistance (V₅₀) development.

• More than 90% of the tests/analyses are for fragments.

• No P_k/h estimates exist for many common components.

• Techniques are adequate for penetration related kill criteria.

• P_k/h for some lethal mechanisms are only obtainable from tests.

• Avionics and electronics are flight critical for many new aircraft designs.

• Structure

  1. Analysis/data are not easily mapped into vulnerability analyses.

  2. Models are largely for skin panels and simple structure.

• Landing gear

  1. Few test/analysis data exist (not flight critical).

  2. Some data are available for Army truck tires.

• Armor

  1. Data are experimentally derived, so confidence levels are high.

  2. Most data are for projectiles and current materials.

• Analysis techniques are valid for metal rotor blades.

• Component P_k/h data are mostly for fragments and armor-piercing projectiles.

• Flight controls can use aircraft techniques and data.

• Tail boom structural analysis capability is poor.

• Little recent test/analysis has been done for P_k/h development.

• Extensive tests are needed for failure at specified conditions.