Mastery of the Air: Personal Reflections on 35 years of Watching Tiltrotors Take Flight

My engineering journey into vertical flight started as a graduate student at the Alfred Gessow Rotorcraft Center at University of Maryland in 1988. Perhaps more accurately, it began with the first class in VSTOL Aerodynamics from Prof. Barnes McCormick at Penn State in 1987. Or maybe it’s when I saw my brother’s motorized plastic scale model of a UH-1 Huey spin up with a home-installed electric motor many years before that!

Whatever the moment was, I have remained in and “leaned into” the inspiring and captivating vertical flight engineering community for many years-hopefully with many more exciting years ahead.

In my professional role, I have had the opportunity to give many presentations and briefings to a wide audience. From pre-schoolers to college students to industry practitioners, from pilots to flag officers and elected officials, I start many of my briefings with the phrase:

“Vertical flight mobility REQUIRES design, operation, and maintenance of THE MOST COMPLEX machine human beings have ever created…but the payoff is in the capability.”

While there are comparable complex vehicle systems, such as nuclear submarines and space launch vehicles, the small packaging and number of moving parts per cubic foot makes the modern rotorcraft a unique challenge – and an engineering marvel to be proud of.

It’s been nearly 75 years since the early flights of the Bell XV-3. The development and systematic maturation of the tiltrotor aircraft represents one of the pinnacle achievements of the aerospace engineering community. Progress has been substantial, but our work is far from over.

My first “hands-on experience” with the V-22 Osprey was simply building a model at my kitchen table kit back in 1988 (that model, along with many others, still sits in my office). The model was white, representing a developmental test version that was flying at that time.

My graduate research from 1988-1992 was focused on specialized composite rotor blades for helicopter and tiltrotor applications. Via extensive reading, software development, and validation efforts, I developed even more appreciation for the vehicle.

I also read, with great interest, an article in Vertiflite magazine describing Sikorsky Aircraft’s research and development into Variable Diameter Tiltrotor (VDTR) aircraft. That article, written by one of Sikorsky’s most respected vehicle designers, Evan Fradenburgh, was particularly inspiring.

After arriving back at Penn State as a faculty member, I was committed to furthering tiltrotor research and development efforts. One of my first research grants was to work with students and sponsors to explore tailored composite tiltrotor blades and wings for the U.S. Army and U.S. Navy.

Motivated by the challenges of conventional helicopter operations on windy ship decks, we also developed analyses of startup and shutdown of tiltrotors in such conditions.

Around that same time, we were travelling with student field trips to Boeing in Ridley Park, PA, to see the high-tech manufacturing lines for the all-composite Osprey fuselages.

We even saw a V-22 test aircraft come in for a landing and hover taxi in the Boeing flight test facility in Wilmington, DE. What an unexpected and thrilling moment for our entire group.  The sights, sounds, and even smells of that event formed a complete sensory experience to behold.  We were (even more) hooked.

When I received a V-22 rotor blade cross-section slice for our growing collection on campus, it became one of our prized possessions and educational teaching items. It has been completed by Model 609 civil tiltrotor sections, and many more examples of rotor blade components.

More field trips to NAS Patuxent River over the years enabled us to see the first round of operational test aircraft in the hangars, including “8 Ball”, one of the first loads survey and maintenance development aircraft. The Osprey at that time was taking flight with the Marine Corps.

When Penn State decided to expand our rotorcraft faculty base in 2001, we hired Dr. Joe Horn from Sikorsky. Joe’s award-winning doctoral research at Georgia Tech was on load-limiting flight-control laws for tiltrotors. He joined our faculty and made a major impact on rotorcraft flight simulation and control for more than 20 years.

Among his major accomplishments has been the development of two manned flight simulation facilities. Both were enabled by financial support from the Office of Naval Research and invaluable hardware (actual aircraft cabins) from Bell in Ft. Worth, TX. The XV-15 cabin and the 609 cabin were delivered to campus and have formed the basis for our work for more than 20 years.

Speaking of the 609, civil tiltrotors are just around the corner. I had the opportunity to explore inside the first 609 fuselage in Ft. Worth over 15 years ago. I have followed the development of this revolutionary vehicle for many years. Indeed, Leonardo Helicopters in Philadelphia is now close to completion of the long process of certification for the first fly-by-wire commercial tiltrotor, and subsequent delivery into commercial service.

In the years since that trip to Bell’s prototype fabrication facility, European OEMs (e.g., the Leonardo 609 vehicle development, the future ERICA program) and numerous eVTOL companies and venture capital organizations have aggressively pursued development of several different civil tiltrotor configurations (e.g., Joby Aviation, ARCHER, and Overair Butterfly) for the commercial market.

The unique combination of higher speed, higher range, and higher altitude (all driving productivity gains) with efficient hover capability and runway independence has truly been a game changer in vertical flight aviation product development.

A steady stream of university, industry, and government sector research work has focused on expanding the flight capabilities, reducing the cost, and improving the readiness, safety, and refining the training tools for tiltrotor aircraft.

Aeromechanics simulation, active and passive vibration control methods, advanced flight control development, tailored composite rotor and wing structures, advanced drive systems, nacelle and engine improvements, icing protection systems, and even unmanned-tiltrotor systems have all seen substantial progress in the past 30 years.

Thanks to continued private and government investment, tiltrotor technological progress is indeed accelerating at an exciting pace.

Led by the vision and perseverance of the USMC aviation community, U.S. government, and a bevy of extraordinary aerospace industry engineers and manufacturers, the V-22 is now in operational service with the USAF, USN and even the storied HMX-1 squadron (which I have had the honor of touring on multipole occasions).

The U.S. Army has recently selected the V-280 Valor as the platform for the Future Long Range Assault Aircraft (FLRAA). This advanced-generation tiltrotor aircraft has transformative potential across multi-mission functions.

Military operations have always pushed the envelope of aviation technology.   From the first powered flight vehicles of the early 20th century to the first rotary-wing vertical flight aircraft decades later to the power and productivity of the jet age to spaceflight, stealth aircraft, and drones, hard lessons have been learned through extraordinary bravery and tragic sacrifice.  Aviation involves the careful, innovative, and efficient management of high kinetic and potential energy to accomplish amazing things.

Of course, tiltrotor technology is fundamentally engineered on many levels to be safe. That is certainly true of all aviation products. Without mentioning specifics, sometimes inaccurate and often sensationalized media coverage of mishaps along the path have challenged the progress and at times resulted in costly setbacks – however, the sound engineering and steadfast dedication of thousands of aerospace professionals around the world has resulted in a new generation of flying machine.

My colleagues and I here at Penn State VLRCOE remain committed to training the next generation of vertical flight engineers and supporting enabling technologies to continue the trajectory of success. The payoff is truly in the unique capability!

The author is Distinguished Professor of Aerospace Engineering and Director, Penn State Vertical Lift Research Center (VLRCOE), Penn State University, University Park, PA.

The featured photo is of the author visiting the HMX-1 hangar.