During and after World War II, aircraft designers were faced with the problem of increasing the range of strategic bombers. Dr. Richard Vogt, a German immigrant to the United States, proposed that floating wing panels carrying fuel tanks could be attached to the wing tips of an airplane with hinges to extend its range. The floating wing panels would support their own weight, without increasing the load on the airplane's wings. The Air Force initiated a project to simulate floating wing panels with a piloted light plane that coupled to a larger airplane in flight. Soon the scope of the project expanded to explore the possibility of towing fighters coupled to the wing tips of bombers.

Project FICON (Fighter conveyer): In the early 1950s, the Air Force conducted a series of experiments to establish the feasibility of carrying, launching, and retrieving jet reconnaissance airplanes from giant Convair RB-36 bombers. It was hoped that the bombers would carry the reconnaissance jets to the perimeter of the Soviet Union and then release them to penetrate the air defenses. Tests of the concept were conducted in 1952 and 1953 with a Republic F-84E Thunderjet and the YF-84F Thunderstreak prototype. Twenty-six Republic RF-84F Thunderflashes and ten Convair GRB-36D carriers were modified for the project. In 1955, a squadron of carriers was established at Fairchild Air Force Base, Washington. A squadron of parasites was established at nearby Larson Air Force Base. Training operations began in December 1955, but the composite aircraft system faced competition from the Boeing RB-52B, Lockheed U-2, and the development of aerial refueling.

The P-85 Goblin was the only airplane that ever flew which was designed from scratch to be operated entirely from another airplane. The development of the B-36 by the Consolidated Vultee Aircraft Corporation of Fort Worth, Texas resulted in a requirement for fighter protection for the bomber at distances from any friendly base that far exceeded the range of currently available escort fighter airplanes. Due to the inability of contemporary fighters to escort B-36 bombers all the way to their targets, the Army Air Corps initiated Project MX-472, Unconventional Fighter Design Studies, on December 3, 1942. The primary objective of the project was the development of a suitable method of protecting the B-36 on long-range bombing missions. The McDonnell Aircraft Corporation designed the P-85 Goblin to fit entirely within the confines of the bomb bay of the B-36. The little fighter was just fifteen feet long with a wing sapn of twenty-one feet.

While successful developments in aviation receive considerable attention, the projects that failed or otherwise did not live up to expectations receive far less, if any, scrutiny. Typically, unsuccessful efforts are briefer in duration and have a less visible paper trail. Thus, while the literature is rich in success stories, we tend to “forget” or simply bury our failures. And, as one observer has suggested, “that there were failures, mistakes, and wrong turns reminds us that progress is not inevitable, that acknowledged error can be as instructive as success, and that roads not taken impose a price all their own.” Here, author Kenneth P. Werrell tells of a race to overcome obstacles—politics, resources, competing technologies, timing—in the quest to deliver quality, if not war-winning machinery. The focus of Air Force Disappointments, Mistakes, and Failures: 1940–1990 is on aircraft (e.g., bombers, fighters, transports) and missiles (e.g., cruise missiles, standoff missiles, ballistic missiles, surface-to-air missiles, air-to-air missiles). An intelligence system is also evaluated. These case studies give the context and details of the development, testing, and, as appropriate, operational service. Highlighting the problems and criticisms of these systems then provides an opportunity to determine what went wrong. The reasons for the failures of these systems vary from the obvious (money, delays, technical problems) to more complex reasons, such as the foe’s reaction, politics, new technologies, and timing. The tale of these disappointments is a heretofore untold story. These projects, in which the US Air Force stumbled, are outliers within the overall success of the service, and, fortunately, its successes outnumber the failures.

Aircraft operating as so-called High Altitude Platform Systems (HAPS) have been considered as a complementary technology to satellites since several years. These aircraft can be used for similar communication and monitoring tasks while operating at a fraction of the cost. Such concepts have been successfully tested. Those include the AeroVironment Helios and the Airbus Zephyr, with an endurance of nearly 624 hours (26 days). All these HAPS aircraft have a high-aspect-ratio wing using lightweight construction. In gusty atmosphere, this results in high bending moments and high structural loads, which can lead to overloads. Aircraft crashes, for example from Google’s Solara 50 or Facebook’s Aquila give proof of that fact. Especially in the troposphere, where the active weather takes place, gust loads occur, which can lead to the destruction of the structure. The Airbus Zephyr, the only HAPS aircraft without flight accidents, provides only a very small payload. Thus it does not fully comply with the requirements for future HAPS aircraft. To overcome the shortcomings of such single-wing aircraft, so-called multibody aircraft are considered to be an alternative. The concept assumes multiple aircraft connected to each other at their wingtips. It goes back to the German engineer Dr. Vogt. In the United States, shortly after the end of World War II, he experimented with the coupling of manned aircraft. This resulted in a high-aspect-ratio wing for the aircraft formation. The range of the formation could be increased correspondingly. The engineer Geoffrey S. Sommer took up Vogt’s idea and patented an aircraft configuration consisting of several unmanned aerial vehicles coupled at their wingtips. However, the patent does not provide any insight into the flight performance, the flight mechanical modeling or the control of such an aircraft. Single publications exist that deal with the performance of coupled aircraft. A profound, complete analysis, however, is missing so far. This is where the present work starts. For the first time, a flying vehicle based on the concept of the multibody aircraft will be analyzed in terms of flight mechanics and flight control. In a performance analysis, the aircraft concept is analyzed in detail and the benefits in terms of bending moments and flight performance are clearly highlighted. Limits for operation in flight are shown considering aerodynamic optimal points. The joints at the wingtips allow a roll and pitch motion of the individual aircraft. This results in additional degrees of freedom for the design through the implementation of different relative pitch and bank angles. For example, using individual pitch angles for individual aircraft further decreases the induced drag and increases flight performance. Because the lift is distributed symmetrically, but not homogenously along the wingspan, a lateral trim of the individual aircraft in formation flight becomes necessary. The thesis presents a new method to implement this trim by moving the battery mass along half the wingspan, which avoids additional parasite drag. Further, a complete flight dynamics model is provided and analyzed for aircraft that are mechanically connected at their wingtips. To study this model in detail, a hypothetical torsional and bending spring between the aircraft is introduced. If the spring constants are very high, the flight dynamics model has properties similar to those of an elastic aircraft. Rigid-body and formation eigenmotions can be clearly distinguished. If the spring constants are reduced towards zero, which represents the case of the multibody aircraft, classical flight mechanics eigenmotions and modes resulting from the additional degrees of freedom are coupled. This affects the eigenstructure of the aircraft. Hence, normal motions with respect to the inertial space as known from a rigid aircraft cannot be observed anymore. The plant also reveals unstable behavior. Using the non-linear flight dynamics model, flight controllers are designed to stabilize the plant and provide the aircraft with an eigenstructure similar to conventional aircraft. Different controller design methods are used. The flight controller shall further maintain a determined shape of the flight formation, it shall control flight, bank and pitch angles, and it shall suppress disturbances. Flight control theories in the time domain (Eigenstructure assignment) and in the frequency domain (H-infinity loop-shaping) are considered. The resulting inner-control loops yield a multibody aircraft behavior that is similar to the one of a rigid aircraft. For the outer-control loops, classical autopilot concepts are applied. Overall, the flight trajectory of the multibody aircraft above ground is controlled and, thus, an actual operation as HAPS is possible. In the last step, the flight controller is successfully validated in non-linear simulations with complete flight dynamics. Flugzeuge in der Form von sogenannten Höhenplattformen (engl. High-Altitude Platform Systems, HAPS) werden seit einigen Jahren als kostengünstige Ergänzung zu teuren Satelliten betrachtet. Diese Flugzeuge können für ähnliche Kommunikations- und überwachungsaufgaben eingesetzt werden. Zu den gegenwärtigen Konzepten solcher Fluggeräte, die bereits erfolgreich im Flugversuch eingesetzt wurden, zählen der Helios von AeroVironment und der Airbus Zephyr, der eine Flugdauer von fast 624 Stunden (26 Tagen) erreicht hat. Alle diese HAPS-Flugzeuge besitzen einen Flügel langer Streckung, der in Leichtbauweise konstruiert ist. Hieraus resultieren in böiger Atmosphäre hohe Biegemomente und starke strukturelle Belastungen, die zu überbelastungen führen können. Flugunfälle beispielsweise von Googles Solara 50 oder Facebooks Aquila belegen dies. Insbesondere in der Troposphäre, in der das aktive Wetter stattfindet, treten Böenlasten auf, die die Struktur zerstören können. Der Airbus Zephyr, der bisher als einziges HAPS-Flugzeug frei von Flugunfällen ist, besitzt nur eine sehr geringe Nutzlast. Daher kann er die Anforderungen an zukünftige HAPS-Flugzeuge nicht vollständig erfüllen. Um die Schwachstellen solcher Ein-Flügel-Konzepte zu überwinden, wird in dieser Arbeit ein alternatives Flugzeugkonzept betrachtet, das als Mehrkörperflugzeug bezeichnet wird. Das Konzept geht von mehreren, an den Flügelspitzen miteinander verbundenen Flugzeugen aus und beruht auf Ideen des deutschen Ingenieurs Dr. Vogt. Dieser hatte in den USA kurz nach Ende des Zweiten Weltkrieges bemannte Flugzeuge aneinanderkoppeln lassen. Hierdurch ergab sich ein Flugzeugverbund mit einem Flügel langer Streckung. Damit konnte die Reichweite des Verbundes gesteigert werden. Geoffrey S. Sommer griff die Idee von Vogt auf und lies sich eine Flugzeugkonfiguration patentieren, die aus mehreren, unbemannten Flugzeugen besteht, die an den Enden der Tragflächen miteinander gekoppelt sind. Die Patentschrift gibt jedoch keinen Einblick in die Flugleistungen, die flugmechanische Modellierung oder die Regelung eines solchen Fluggerätes. Vereinzelt existieren Veröffentlichungen, die sich mit den Flugleistungen von gekoppelten Luftfahrzeugen beschäftigen. Eine tiefgreifende, vollständige flugmechanische Analyse fehlt jedoch bisher. Hier setzt die vorliegende Arbeit an. Ein Fluggerät basierend auf dem Konzept des Mehrkörperflug-zeugs wird erstmalig hinsichtlich der Flugmechanik und Flugregelung untersucht. In einer Flugleistungsbetrachtung wird das Flugzeugkonzept genau analysiert und die Vorteile hinsichtlich der Biegemomente und der Flugleistungen klar herausgestellt. Die Grenzen des Einsatzes im Flugbetrieb werden mithilfe aerodynamischer Optimalpunkte aufgezeigt. über die Lager an den Flügelspitzen, die eine relative Roll- und Nickbewegung der Flugzeuge untereinander ermöglichen, ergeben sich durch die Einstellung unterschiedlicher Längslage- und Hängewinkel zusätzliche Freiheitsgerade im Entwurf. Die Verwendung unterschiedlicher Nicklagewinkel der einzelnen Flugzeuge reduziert beispielsweise den induzierten Widerstand weiter und steigert die Flugleistung. Durch die symmetrische, entlang der Spannweite jedoch nicht homogene Auftriebsverteilung ist auch eine laterale Trimmung der einzelnen Flugzeuge in der Formation notwendig. Hier stellt die Arbeit eine neuartige Möglichkeit vor, um diese Trimmung ohne zusätzlichen parasitären Widerstand mittels Verschiebung der Batteriemasse entlang der Halbspannweite umzusetzen. Weiterhin wird ein vollständiges flugdynamisches Modell für über mechanische Lager verbundene Luftfahrzeuge aufgestellt und analysiert. Für diese Analyse wird eine hypothetische Torsions- und Biegefeder zwischen den Flugzeugen modelliert. Sind die Federsteifigkeiten hinreichend hoch, besitzt das flugdynamische Modell Eigenschaften, die einem elastischen Flugzeug entsprechen. Starrkörper- und elastische Eigenbewegungsformen sind in diesem Fall klar separiert. Bei immer weiterer Reduzierung, bis auf eine Federsteifigkeit von Null, kommt es zu Kopplungen zwischen den klassischen, flugmechanischen Eigenbewegungsformen und den Moden aus den zusätzlichen Freiheitsgraden. Dies stellt den Auslegungsfall für das Mehrkörperflugzeug dar. Hierbei verändert sich die Eigenstruktur (engl. eigenstructure) des Flugzeugs und normale, bei einem starren Flugzeug beobachtbare Bewegungen gegenüber dem inertialen Raum sind nicht mehr erkennbar. Zusätzlich zeigt die Strecke instabiles Verhalten. Basierend auf dem nichtlinearen, flugdynamischen Modell werden mit verschiedenen Methoden Regler entworfen, die die Regelstrecke stabilisieren und dem Flugzeug eine Streckenstruktur zuweisen, die derjenigen klassischer Flugzeuge ähnelt. Zudem soll durch die Regler eine vorgegebene Form des Flugzeugverbundes beibehalten werden, die Fahrt, der Längs- und Rolllagewinkel sollen geregelt und Störungen unterdrückt werden. Als Auslegungsverfahren werden Theorien der Zustandsregelungen im Zeitbereich (Eigenstrukturvorgabe) und Frequenzbereich (H-infinity loop-shaping) verwendet. Hierdurch wird durch die inneren Regelschleifen ein Verhalten des Mehrkörperflugzeugs erzielt, das dem eines starren Flugzeugs entspricht. Für die äußeren Regelschleifen werden anschließend klassische Konzepte von Autopiloten verwendet. Im Ergebnis ist eine Regelung des Flugweges über Grund des Mehrkörperflugzeugs und somit ein tatsächlicher Betrieb als HAPS möglich. Die Funktionalität des Reglers wird abschließend in nichtlinearen Simulationen mit vollständiger Flugdynamik verifiziert.

This document tracks the changes to the appearance of the two Boeing B-52 Stratofortresses that were modified to carry and launch the North American X-15 rocket planes. The two NB-52s went on to launch the X-15A-2, Northrop HL-10, Northrop M2-F2, and Martin-Marietta X-24A. The NB-52A retired in October 1969, but the NB-52B soldiered on until November 2004, launching a wide variety of unmanned research vehicles and parachute test devices. The appearance of the NB-52s changed many times over the years. These changes are illustrated in this document. There are fourten sets of illustrations for the NB-52A and eighteen sets of illustrations for the NB-52B. The Stratofortress motherships are popular subjects for modelers. Their special missions capture the imagination. The liberal application of DayGlo orange, DayGlo red, and yellow makes them a couple of the most colorful B-52s. This document will help modelers to reproduce the correct appearance of either Stratofortress for any particular mission.

The General Electric Air Research Laboratory at the Schenectady, New York Airport hosted an open house on June 22, 1946, less than one year after V-J Day. It was an overcast day with intermittent rain. The event featured a variety of prototype airplanes and helicopters and some modified testbed airplanes. Many of the airplanes were pinnacles of piston-powered aircraft technology. Examples of early jet fighters foreshadowed the coming transition to jet power. The first jet air mail service was carried by a pair of Lockheed P-80 Shooting Stars that departed from the open house.Richard Lockett, a General Electric employee, photographed the aircraft participating at the open house. He documented the evolving technology of the day. He also captured the behavior and fashions of the people attending the show.