Field Trip # 3: National Museum of the United States Air Force – Investigating “The Advancement of Dynamics and Controls In Aerospace Engineering”

Hosts: Dr. Kelly Cohen, Faculty Mentor and Professor, Professor, School of Aerospace Systems and Mr. Wei Wei, Graduate Student in Aerospace Engineering, University of Cincinnati

Date: July 16, 2012 Time: 12:00-5:30 PM

Venue: National Museum of the United States Air Force, Dayton, OH

Prepared by:Participants for Project 2: Optimizing Operations in Complex Semiconductor Manufacturing Processes

Owen Macmann, University of Cincinnati, Aerospace EngineeringDevon Riddle, University of Cincinnati, Aerospace Engineering

Mahogany Williams, Wilberforce University, Computer EngineeringJuly 16, 2012

Despite the advancements that have been made in the aerospace field since the Wright brother’s first flight, problems with dynamics and controls still persist today. Developing controls for aircrafts can be a monumental task considering in part the complexity of the underlining mathematical principles of flight. Generally speaking, given that a complete discrete numerical model of an aircraft is difficult to create, we can settle on a partial ideal model as an approximation. Using such models generally control theories are developed. Since the early 1900s, aircrafts have drastically evolved in the fields of stability and controls. This advancement notwithstanding; the field remains cutting edge and new challenges crop up daily for the aspiring control designer.

On July 12, 2012, the CEAS half of the REU program of the University of Cincinnati took a tour of the Wright Patterson Air Force Museum. This tour was to be an examination of the development of dynamics and controls since the beginning of the era of powered flight. Upon entering the museum, the tour started off in the Early Years gallery that featured aircrafts primarily from the time of the Wright Brothers’ and the 1910’s. Different models of these aircrafts were displayed throughout the gallery, with the displays gradually featuring more advanced aircrafts as the exhibits went on. At the end of the Early Years gallery, a shift was made into the time of the Interwar period. Opposing the half that was the Early Years exhibit, the other half of the first hangar was dedicated to the aircrafts of World War 2. The World War 2 display was similar to the Early Years Age in keeping to the strict timeline from beginning to end. At the end of the World War 2 Age, a hallway was connected to a separate hangar that was in a similar style to the first. On one side of the hangar the aircraft vehicles that were displayed were dedicated to the Korean War while on the other half the displayed aircrafts were the ones used during the Vietnam War. Both displays were separated to give a tourist an option before heading through an opposing hallway into a third hangar that was completely dedicated to the Cold War. The Cold War gallery was the largest display of all considering it took up the space of a hangar to itself. Another room beyond this hangar was dedicated to a few space rockets and vehicles. This was where the tour ended.

One of the first aircrafts that was displayed was the Wright Flyer. This aircraft was displayed in the Early Years gallery and was developed in 1904 (see Figure 1). It featured rudimentary control

surfaces (at the time referred to as “wing warping” given the wing’s tendency to contort its shape) and a rudder that both gave the pilot a baseline ability to steer the aircraft once in flight. It’s worth noting that the Wright flyer, ultimately, did not prevail for years after the initial flight due to the Wright brothers’ design decisions; they insisted on building slightly unstable aircraft that offered the pilot the ability to take an active role in flight. However, competitors opted for more stable aircraft with more moderate learning curves for the pilots. Ultimately, this point of view won out.

Figure 1: Wright Flyer, 1904

A unique aircraft that was first developed in the 1910’s was the autogiro (see Figure 2). It is an aircraft that is similar to a helicopter in that it has a rotor, but the rotor spins due to the forward motion of the craft rather than due to the mechanical rotation of the gyro. This unique configuration gave the autogiro the quality of being able to fly at lower speeds than contemporary aircrafts while remaining stable.

(Image from http://www.youngeagles.org/photos/gallery/)Figure 2: Pitcairn PCA-2 Autogiro, 1931

During World War 1 and the Interwar period, biplanes were the typical design. They included aircrafts that extended from the SPAD 7 to the Standard J1. The SPAD 7 (see Figure 3) was one of the first biplanes designed for World War 1. Although it was made partially of metal, it was also constructed from wooden and fabric parts. As a biplane designed for combat, the SPAD 7 introduced more capable

ailerons, rudders, and elevators over the comparatively rudimentary design of the Wright Flyer. These advancements introduced a complete capacity for rolling, yawing, and pitching.

Figure 3: SPAD S.VII, 1916

Biplanes reigned throughout the 1910’s and early 1920’s as common wisdom held that thinner wings reduced drag. Thus, the biplane approach, featuring two thin wings connected by exposed cables and struts, was the order of the day. In time, however, engineers found that this approach with the exposed cables and struts generated more drag than a single thick wing, and so a gradual shift towards single-wing planes took place. Over the next several decades, these wings would come to be so thick that they could hold within them a variety of additional instruments and necessities; such as engines and fuel tanks. The single thick wing design was called the monoplane.

Monoplanes were the major advancement during World War 2; especially metal monoplanes. The all metal construction of monoplanes and the tough cantilevered wing constructions enabled for stronger aileron construction. These stronger ailerons turned out to be a boon when the general design of dive bombers was introduced. Dive bombing aircrafts were made of metal and featured wings that tended to have a dramatic dihedral. The wing was situated lower on the body and the large landing gears were not retractable. An example of one of the earlier designs for a dive bomber was the P26A Peashooter (see Figure 4). The particularities of the dive bomber design were perfect for making steep dives. They were robust enough to survive pulling out of those dives after having dropped their payload – owing in part to the strong ailerons and their sturdy design.

Figure 4: Boeing P-26 Peashooter, 1932

Another design example that was used during World War 2 was the B-29 Superfortress (pictured below is the infamous “Bockscar,” the B-29 (see Figure 5)that dropped an atomic bomb on Nagasaki in the Empire of Japan). An advanced bomber for its period, it featured a pressurized cabin, an electronic fire-control system, remote controlled machine gun turrets, and it had a high service ceiling. It was an enormous aircraft and one of the most iconic strategic bombers of World War 2. Its use of high technology laid the groundwork for more sophisticated controls in aircraft designs to come.

Figure 5: “Bockscar” B-29 Superfortress, 1942

By the end of World War 2, it was clear that the future of aircraft lay in the construction of jet aircraft. Propeller aircrafts would remain in use for some time to come, but were gradually phased out in favor of jet aircrafts. In addition, the mastery of the helicopter’s complicated dynamics permitted their subsequent use in the Vietnam War. A revolution in aerospace engineering; the helicopter (see Figure 6) is an example of how difficult modeling and simulation problems, once solved, can yield promise.

(Image from http://www.history.com/photos/vietnam-war/photo1)Figure 6: A Navy helicopter used during the Vietnam War

The image in Figure 7 is that of a metal monoplane that was still in use during the Korean War. It is one of many propeller aircrafts that was still used during the war despite the advancements in jet technology.

Figure 7: T-6D Mosquito, 1935

The Vietnam War gallery had many particularly interesting aircrafts on display. The F-4 Phantom II (see Figure 8), a type of aircraft often referred to as a “Wild Weasel,” was a particularly novel jet that fulfilled the roles of interceptor fighter as well as fighter bomber on occasion. The “Wild Weasel” nickname came from a project title with same name that was centered on the development of aircraft that could detect and suppress enemy ground-based anti-air. These aircrafts made ample use of radar technology to bait enemy radar installations into targeting it, whereupon counter triangulation of the detecting radar allowed the Wild Weasel to hone in on its target. As a significant innovation in the use of radar and communications technology, its reliance on radar is similar to modern day UAVs that rely on wireless communications to stay operational.

Figure 8: McDonnell Douglas F-4 Phantom II, 1958

While the Cold War had the largest display out of all of the galleries, there were a few specific aircrafts that stuck out. Pictured in Figure 9 is a Lockheed AC-130A Spectre Gunship. Still in use today, it is an invaluable ground attack aircraft and an example of ground support at its finest. From observing its design and its copious use of peripheral weaponry; similarities to the Superfortress abound. Most importantly, the aircraft demonstrated the debut of a maneuver known as the pylon turn. This was

enabled by significant advances in the categories of control systems. The pylon turn maneuver consisted of an aircraft banking in a circular turn in a way to enable an imaginary line projecting directly out of the side of the aircraft to remain fixed on a point on the ground. The advanced controls and the specific design of the aircraft that permitted this maneuver gave the Spectre terrific loitering capability. This allowed it to focus its fire on one point on the ground for extended periods of time.

Figure 9: Lockheed AC-130A Spectre Gunship “Azrael,” 1966

Later in the gallery was an exhibit featuring the most remarkable and modern strategic bomber of all; the Northrop Grumman B-2 Spirit (see Figure 10). This aircraft stood out as an exceptional case of mastery over aerodynamics and controls. The flying wing design – conducive as it was to the bomber’s stealth quality – made it complicated enough that to fly the Grumman without the aid of a computer would be dangerous. By synchronizing superior aerodynamic designs with the enhanced controls capability of an on board computer; one of the worlds’ most advanced aircrafts to date was designed and built. With a range of almost 7000 miles, the ability to hold up to 50,000 lbs of ordnance, and stealth capability that enabled it to evade radar detection; it was truly a monumental feat of aerospace engineering.

(Image from http://en.wikipedia.org/wiki/B-2)Figure 10: Northrop Grumman B-2 Spirit, 1989

By the end of the tour, the REU participants had acquired a stable working knowledge of the advancements of dynamics and controls across the years. A question that remains unanswered; however, is what can be expected from the future? It is believed that the future of aerospace engineering lies in the hands of unmanned aerial vehicles (UAV’s), both operating alone and when swarming. Swarming is a term used to reference multiple UAVs working together in concert which relates to the current project that REU Project 1 is working on. REU Project 2, meanwhile, is looking into the controls and dynamics of small UAVs, with the ideal goal of being able to construct an autopilot using experimentally derived mathematical models. As the REU participants saw on this field trip to the National Museum of the Air Force, it is through small steps one can progress. However, when one considers the difference between that titan of the sky, the Northrop Grumman B-2 Spirit, and the indefatigably modest Wright Flyer; it is hard not to be optimistic about the future.