A Probabilistic Methodology for Evaluating the Birdstrike Threat to Aircraft
SYNOPSIS
Eight to 10 F-111 aircraft were lost between 1967 and 1969 due to
structural failures. In 1967 through 1972 an additional 4 F-111’s
and 2 trainer (low altitude operations) aircraft were lost to
birdstrikes. The program was in serious difficulty. In 1975 the F-16
program was initiated and adopted a requirement for low-level
supersonic dash of Mach 1.2, a requirement similar to the F-111’s.
By 1976 the F-111’s had experienced 39 canopy birdstrikes
involving 23 major penetrations and 6 loses. During this period the
FAA/NASA proposed a 4-pound bird impacting at 350 KTAS birdstrike
criterion.
The
F-16 proposed a bubble shaped canopy without structural reinforcement
to improve air-to-air combat performance – a high-risk strategy
given the F-111 experience. This report describes the technical
solution to the birdstrike challenge encountered in the F-16 and
F-111 programs. The result was the abandonment of the deterministic
FAA criterion, the adaptation of a probabilistic design criterion and
the incorporation of the methodology into the formal Joint Services Specification Guidance, JSSG 2006. Since the 1970’s DoD airframes
have implemented this approach and expanded its application to other
classes of discreet source impact threats. A similar technology
evolution for the Damage Tolerance characteristics of the airframe
occurred in the same time frame and was also formalized in the DoD
JSSG 2006 airframe requirements. Damage Tolerance concepts have been
integrated into the appropriate CIVIL requirements. A similar
integration of the MIL and CIVIL discreet source birdstrike impact
requirements and has not occurred.
No comments:
Post a Comment