Aircraft Case Studies

Predator and Gray Eagle

High Compression Strength of Hy-Bor Allowed Retro-fit of Aircraft to Increase Payload Capacity

 
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The Challenge

•DOD needed Predator to carry munitions

•Increased mass put additional compression load on wings

•Modification could not change outer mold line of aircraft

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The Approach

•Adding additional thickness to graphite epoxy spars was impossible due to cracking & exotherms

•Specialty Materials & Mitsubishi worked with General Atomics to evaluate and test 4 mil boron/MR40/NCT 301 product which increased compression strength by 122% achieving mission requirements

The Result

•First Predator Mission with Hellfire Missile flew in February of 2001

•Air Force fleet in 2001 was 16 vehicles for reconnaissance & they only planned to buy 48 additional vehicles by end of 2003

•By 2014 Air Force has over 303 vehicles in use with over 2 million flight hours

•Resulted in an unprecedented change in war fighting

References:

https://www.airspacemag.com/flight-today/hellfire-meets-predator-180953940

https://www.af.mil/News/Article-Display/Article/1445531/sunsetting-the-mq-1-predator-a-history-of-innovation

Aircraft Structures

First Use of High Performance Composites in Primary Structure

 
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The Challenge

•Lower mass aircraft are identified as one of the key enablers to winning the cold war

•Project Forecast initiates work on boron and carbon fiber composites

•Needed analytical methods to predict advanced composite response to structural loads

•Four United States suppliers of boron fiber by 1967

•Carbon fiber still had high degree of variability but was had potential to be lower cost

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The Approach

•Boron Fiber Reinforced Plastics (BFRP) due to the large fiber size was ideally suited for micromechanics analysis development

•Macromechanics development facilitated by the neat layer distinction of BFRP laminates

•BFRP traded with titanium due to 3000F temperature requirement, boron/epoxy selected due to weight saving

•Boron/5505 selected due to it high compression strength at 3750F

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The Result

•F-14 used boron composites for horizontal stabilizers and saved 19% of the structure weight (182 lbs per aircraft, 2.5 times the required fatigue life)

•F-15 used boron composites for vertical stabilizer, horizontal stabilizer and rudders resulting in 22% weight savings. Verticals and rudders are replaced due to fatigue limitations on titanium frames and in-service damage. Boron skins of vertical are net molded to titanium frames