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Optical Evaluation of F-FB-111 Field Service Test Windshields

This report describes the principal effort by the USAF School of 
Aerospace Medicine (USAFSAM) in support of the F/FB—III bird—impact— 
resistant windshield field—service- test program (Air Force Flight 
Dynamics Laboratory Project 1426- 75—01 and Tactical Air Command 
Project 75c-126W) . 
The F/FB—III windshield design is rather atypical for flight 
craft in that it consists of tvo windshields forming a 
cone section installed at 68 degrees from vertical and viewed through 
an oblique angle by the aircrew (Fig. l) .

A more serious windshield concern arose In the form of destructive 
birdstrlkes. Because of Its high—speed, low—level mission require— 
ments, the F/FB—III has a high probability In encountering birdstrikes 
of enormous Impact force. When a number of strikes occurred on the 
0.85—cm (0.33—in) thick, 3—p1y, chemically tempered glass windshields, 
catastrophic vindshleld failure occurred vlth bird penetration; and 
aircraft loss resulted In some Instances. Concerned about this loss 
potential, the U.S. Alr Force requested the development of a wind— 
shield that vould survive a birdstrike at mission profile 
and velocity (TAC "Required for Operational Capability" (ROC) "26—71) . 
Pittsburgh Plate Glass (PPG) Industries, under contract award, developed 
a windshield, approximately 2.54 cm (l In) thick, Of a 10—p1y design 
composed of acrylic, polycarbonate, and proprietary Innerlayers. The 
structural properties of this windshield vill defeat penetration in a 
high—speed bird Impact. The Alr Force Flight Dynælcs Laboratory (AFFDL) 
development program manager vas directed to field—test ten shipsets 
of the PPG windshields for approximately I year before receending 
full—fleet retrofit. The purpose of the field test vas to evalv•te 
the envirormental effects upon the unproved plastic materials an. to 
moni tor aircrev acceptance of potential optical—error characteristics 
imparted In the manufacturing process.