AIRCRAFT ENGINE FRAGMENT BARRIERS

Because fragments from in-flight engine failures can damage critical aircraft components and produce catastrophic consequences, the Federal Aviation Administration is sponsoring research to mitigate the effects of uncontained engine bursts. SRI International is evaluating the ballistic effectiveness of fabric structures made from advanced polymers and developing a computational ability to design fragment barriers.

FUSELAGE TEST SETUP

SRI performed full-scale fabric barrier tests on an aircraft fuselage at the Navy Air Warfare Center in China Lake, CA. The tests examined the effects of polymer material, number of plies, location of the fabric within the fuselage wall, and gripping arrangements.

FUSELAGE IMPACT TEST

The results were very encouraging. For example, three plies of Zylon (PBO) woven fabric glued to the outboard side of the insulation packet and weighing only 0.05 g/cm2 (0.1 lb/ft2), prevented a 166-g (0.37-lb) sharp-edged fan blade fragment impacting edge-on at 230 m/s (756 ft/s) from penetrating into the cabin. The absorbed energy of 4400 joules (3250 ft-lb) is nearly an order of magnitude greater than that absorbed by the unfortified fuselage wall.

To get the same improvement in ballistic protection by adding aluminum would require more than doubling the thickness of the fuselage wall - an increase in weight of more than 12 times that of the fabric barrier. These results confirm that high-strength polymer fabrics offer an extremely effective, low-weight solution for mitigating the effects of uncontained turbine engine fragments on commercial aircraft.