Linden S. Blue is an aviation pioneer. He and his brother Neal were dubbed “the Flying Blue brothers” and depicted on the April 8, 1957, cover of Life Magazine as members of the Yale Aerial Expedition to South America.

Sixty-five years later, Blue has compiled an impressive resume in the aerospace industry, including president and CEO of Beech Aircraft Corporation, a director of Raytheon Company, CEO of Lear Fan Limited, executive vice president and general manager of Gates Learjet Corporation and managing director of Spectrum Aeronautical. He continues to be energized by aeronautics, as well as advanced materials such as composites that allow for industry innovations.

“The physical properties of composites are compelling, there’s no question about that, compared to all the metals – aluminum, titanium, steel,” said Blue during a keynote address at ACMA’s Advanced Air Mobility Composites Technology Days in the spring. “And the tremendous advantage is getting away from fasteners. That’s where you get a lot of weight savings and labor savings.”

Blue, who currently is an owner and vice chairman of San Diego-based General Atomics, discussed the evolution of composites and much more in his keynote address, which is featured here in an abridged version with subheads, followed by a question-and-answer session with Tech Day moderators John Busel, vice president of ACMA’s Composites Growth Initiative, and Dan Coughlin, leader of industrial collaborations at Oak Ridge National Laboratory.

A ‘Better Way’ with Composites

“If you really want to learn to love composites, you ought to build airplanes out of aluminum and rivets for five years as I did at Learjet. We made some wonderful airplanes out of aluminum, but when you walked through the factory there was a cacophony of rivet guns. When you see the labor intensiveness of it, you’ve just got to say, ‘There must be a better way.’ Well, what served me in composites was thinking there must be a better way.

At one point, I visited the [Learjet] Aeronca factory in Ohio to learn about the thrust reversers for their jets. In the process, I saw they had made a composite flap track fairing for a 707 or 747. That part was very large – about the size of their jet fuselage. And in fact the shape was a lot like their jet fuselage.

It was quite a revelation to me to see how they were making composites, then go back to [my factory] and hear the rivet guns and see the difficulties of blowing holes in material and putting in rivets and all the quality control factors that go into that. At that time, as general manager of Learjet I was always looking at better ways of doing things.

It’s a matter of matching available technology to a need. In this case, Learjet needed a more economical version of its model 25 [high-speed business jet aircraft]. We ended up being the first people to apply winglets to our airplanes. The advantage for the Learjet is we were able to add wing area aspect ratio and get by with less thrust.”

Early Adoption of New Technologies

“When Lear Fan was embryonic, they recruited me. I was very willing to listen to their proposal because I had seen what composites could do. I ended up becoming CEO of Lear Fan. [The turboprop airplane] was first-generation composites. We essentially were trying to make metal parts out of composites. You could do it. In fact, prior to that we made a landing gear door out of composites. But the idea of doing a whole plane was a huge step beyond that.

In the first generation, when you try to make ‘black aluminum’ [CFRP] parts you end up with most of the disadvantages of aluminum and few of the advantages of composites. So, you hope to find a better solution.

Second generation was honeycomb sandwich panel, and that was a technology we used with the Starship program at Beech. I left Lear Fan and became the CEO of Beech Aircraft. The idea was to bring Beech into the modern era with the best possible materials. Honeycomb sandwich panels were good, but we didn’t get the weight savings and there were other issues. Sandwich panels are wonderful in many respects, but they have a lot of limitations as well.The third generation is [representative of what] the 787 did and dramatically improved technology over honeycomb sandwich panels. Honeycomb sandwich panels had been used in vertical stabilizers for some of the big airplanes before the 787’s effort to make the entire airframe out of composites.

The 787 is simply a better airplane. One of its major advantages, in addition to composites, is reduction in the number of fasteners by a factor of 100 compared to a similarly sized 777. When you reduce the things that put airplanes together by a factor of 100 that’s a tremendous opportunity for saving time and avoiding all the problems you get into when you drill a hole in a material.”

Next-Generation Composite Materials

“In the fourth generation, there is the potential for reducing fasteners by another factor of 10, which would give you 1,000 times fewer fasteners than conventional aluminum. That’s what we have done with the Spectrum business jet. It’s not finished or certified, but it has a great deal of promise. And instead of fasteners it relies primarily on co-curing – making large parts that go together homogeneously in the curing process.

Perhaps the fifth generation will start to make greater use of thermoplastics. Thermoplastics have the advantage of lower knock-down factors and the ability to weld structures together at very high temperatures. That gives you an integrity in the combining of parts much better than either co-curing or bonding. I can’t say that thermoplastics are ready to vie in all respects, but there is a great deal of promise there.

I feel very privileged to have been involved in all 4 [developmental] stages that exist today, and I’m hoping to be involved in the fifth stage as well.”

The Role of AI and Unmanned Aircraft