F-8 Digital Fly-By-Wire Aircraft

The Digital Fly-By-Wire (DFBW) concept uses an electronic flight-control system coupled with a digital computer to replace conventional mechanical flight controls.

F-8 DFBW in flight

The first test of a DFBW system in an aircraft was in l972 on a modified F-8 Crusader at the Flight Research Center, Edwards, Calif. (now Dryden Flight Research Center). It was the forerunner of the fly-by-wire flight control systems now used on the space shuttles and on today’s military and civil aircraft to make them safer, more maneuverable and more efficient. It was safer because of its redundancies and because, for military aircraft, wires were less vulnerable to battle damage than the hydraulic lines they replaced. It was more maneuverable because computers could command more frequent adjustments than a human pilot and designers could do away with features that made the plane more stable and thus harder to maneuver. For airliners, computerized flight control could also ensure a smoother ride than a human pilot alone could provide. Finally, digital fly-by-wire was more efficient because it was lighter and took up less volume than hydraulic controls and thus either reduced the fuel required to fly with the extra weight and/or permitted carrying more passengers or cargo. It also required less maintenance than older systems.

Background

In the first few decades of flight, pilots controlled aircraft through direct force – moving control sticks and rudder pedals linked to cables and pushrods that pivoted control surfaces on the wings and tails.

As engine power and speeds increased, more force was needed and hydraulically boosted controls emerged. Soon, all high performance and large aircraft had hydraulic-mechanical flight-control systems. These conventional flight-control systems restricted designers in the configuration and design of aircraft because of the need for flight stability.

As the electronic era evolved in the 1960s, so did the idea of aircraft with electronic flight-control systems. Wires replacing cables and pushrods would give designers greater flexibility in configuration and in the size and placement of components such as tail surfaces and wings. A fly-by-wire system also would be smaller, more reliable, and in military aircraft, much less vulnerable to battle damage. A fly-by-wire aircraft would also be much more responsive to pilot control inputs. The result would be more efficient, safer aircraft with improved performance and design.

The Aircraft

By the late 1960s, engineers at Dryden began discussing how to modify an aircraft and create a digital fly-by-wire testbed.

Support for the concept at NASA Headquarters came from Neil Armstrong, former research pilot at Dryden. He served in the Office of Advanced Research and Technology following his historic Apollo 11 lunar landing and knew electronic control systems from his days training in and operating the lunar module. Armstrong supported the proposed Dryden project and backed the transfer of an F-8C Crusader from the U.S. Navy to NASA to become the Digital Fly-By-Wire (DFBW) research aircraft. It was given the tail number « NASA 802. »

Wires from the control stick in the cockpit to the control surfaces on the wings and tail surfaces replaced the entire mechanical flight-control system in the F-8. The heart of the system was an off-the-shelf backup Apollo digital flight-control computer and inertial sensing unit which transmitted pilot inputs to the actuators on the control surfaces.

Pilot Gary Krier in front of F-8 DFBW

On May 25, 1972, the highly modified F-8 became the first aircraft to fly completely dependent upon an electronic flight-control system. The pilot was Gary Krier.

The first phase of the DFBW program validated the fly-by-wire concept and quickly showed that a refined system – especially in large aircraft – would greatly enhance flying qualities by sensing motion changes and applying pilot inputs instantaneously.

The Phase 1 system had a backup fly-by-wire system in the event of a failure in the Apollo computer unit, but it was never necessary to use the system in flight.

In a joint program carried out with the Langley Research Center in the second phase of research, the original Apollo system was replaced with a triple redundant digital system. It would provide backup computer capabilities if a failure occurred.

The DFBW program lasted 13 years. The final flight – the 210th of the program – was made April 2, 1985, with Dryden Research Pilot Ed Schneider at the controls.

Research Benefits

The F-8 DFBW validated the principal concepts of the all-electric flight control systems now used on nearly all modern high performance aircraft and on military and civilian transports. A DFBW flight-control system also is used on the space shuttles.

NASA 802 was the testbed for the sidestick-controller used in the F-16 fighter, the first U.S. high-performance aircraft with a DFBW system.

Among other electronic devices flown on the DFBW F-8 were an angle-of-attack limiter and maneuver leading- and trailing-edge flaps, features commonly used on today’s new generation of aircraft.

F-8 DFBW Apollo computer interface box

In addition to pioneering the Space Shuttle’s fly-by-wire flight-control system, NASA 802 was the testbed that explored pilot induced oscillations (PIO) and validated methods to suppress them. PIOs occur when a pilot over-controls an aircraft and a sustained oscillation results. On the last of five free flights of the prototype Space Shuttle Enterprise during approach and landing tests in 1977, a PIO developed as the vehicle settled onto the runway. The problem was duplicated with the F-8 DFBW and a PIO suppression filter was developed and tested on the aircraft for the Shuttle program office.

The aircraft was used to develop a concept called Analytic Redundancy Management, in which dynamic and kinematic relations between various dissimilar sensors and measurements are used to detect and isolate sensor failures.

In another series of successful tests, a software back-up system (Resident Backup System) was demonstrated as a means to survive common software faults that could cause all three channels to fail. This system has been subsequently used on many experimental and production aircraft systems.

The Dryden project also worked with the British Royal Aircraft Establishment using the DFBW F-8 to produce ground-based software to use when researchers are investigating flight controls in high-risk flight environments. During contingencies, pilots can disengage the ground control software and switch to backup on-board controls. DFBW research carried out with NASA 802 at Dryden is now considered one of the most significant and successful aeronautical programs in NASA history.

Digital fly-by-wire is now used in a variety of airplanes ranging from the F/A-18 to the Boeing 777 and the space shuttles.

Specifications

The F-8 aircraft was originally built by LTV Aerospace, Dallas, Texas, for the U.S. Navy, which made it available to Dryden as a test vehicle.

F-8 DFBW 3-view drawing

  • NASA 802: Navy Bureau #145546
  • Powerplant: Pratt and Whitney J57 turbojet
  • Wingspan: 35 feet 2 inches (350 square feet)
  • Overall length: 54 feet 6 inches and height is 15 feet 9 inches
  • Flown as the DFBW testbed by NASA from 1972 to 1985.
  • Fleet F-8s were the first carried based planes with speeds in excess of 1,000 mph. LTV won the Collier Trophy for its design and development. Total production was 1,261.

NASA courtesy (www.nasa.gov)

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Charles « Chuck » YEAGER – 65 years ago !

THE RIGHT STUFF  / L’ETOFFE des HEROS

Supersonic aircraft X-1 in flight
Photo: NASA

Captain Charles « Chuck » YEAGER broke the sound barrier with the help of his friend Jack RIDLEY on a 14th of October 1947 – He did it 61 years ago!

Brigadier General Charles Chuck Yeager next to his X-1 aircraft

(U. S. Air Force illustration/Mike Carabajal)

Supersonic aircraft X-1
Photo: NASA

Supersonic aircraft X-1 pre-flight inspection

Photo: U.S.Air Force Link

XLR-11 ROCKET POWERED AIRCRAFT

Birth of Manned Rocket Research Airplanes: 1946 to 1975

The first reliable, effective rocket engine that would provide boost for experimental research aircraft was produced by four members of the American Rocket Society (ARS) who combined forces to form Reaction Motors Incorporated (RMI) (Rockaway, New Jersey) for developing the Experimental Liquid Rocket (XLR-11) rocket motor. The XLR-11 engine had four separate rocket chambers. Each chamber provided 1500 lb of rated thrust and could be operated independently as a means of throttling thrust in quarters, up to 6000 pounds. The XLR-11 possessed remarkable longevity, powering an impressive fleet of rocket aircraft for more than a quarter of a century (1946 to 1975). This fleet of vehicles were the first rocket aircraft devoted solely to high performance experimental flight research. They were not constrained by military or commercial demands and ranged from being the first to break the sound barrier (XS-1), to the first to reach Mach 2.0 (D-558-II [fig. 5]), to the first to exceed the X-2 Mach 3.2 record (X-15 with two XLR-11 engines).

D-558-II airplane on Rogers lakebed

Figure 5. The D-558-II airplane on Rogers lakebed.

The X-1E – Early Development of Energy Management

Design efforts to extend aircraft performance produced increased wing loadings, W/S, and decreased lift-to-drag ratios, L/D. These design changes were beneficial in reducing drag to achieve supersonic and hypersonic speeds, but were also detrimental in that they reduced the area of the maneuvering footprint and presented difficulties in the approach and landing.

As L/D values decreased, the glide slope angle and the rate of descent increased, making it more difficult for pilots to estimate distances and times required for acceptable landings. The X-1E (fig. 6) was modified with a low-aspect-ratio wing having a thickness-to-chord ratio of four percent – the only aircraft of the X-1/D-558 series to have sufficiently low L/D values to require unique energy management techniques. This X-1E was the first to experiment with approach patterns designed to give
the pilot more time in the traffic pattern to manage energy.

The landing pattern was approached in a conventional manner except that altitudes and speeds were somewhat higher than for
powered aircraft. The initial reference point was established at 12,000 ft (mean sea level) on a downwind heading (180 deg remaining to turn). The downwind leg was offset some four miles from the centerline of the landing runway. On downwind, abeam the touchdown point, landing gear and partial flaps were deployed at a speed of 240 knots. Full flaps were usually deployed on the final approach. At the initial reference point the pilot had almost three minutes until touchdown – additional time for handling increased speeds and sink rates.7,8

X-1 supersonic aircraft on Lakebed

Figure 6. The X-1E airplane on Rogers lakebed.

X-1E supersonic aircraft under B-29 Mothership

Secret declassified USAF pilot Charles Chuck Yeager after breaking the sound barrier on X-1

Report from www.archives.gov

X-1 supersonic aircraft instrument panel

(Text from the NASA at: http://www.nasa.gov/centers/dryden/home/index.html)

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YVES Fusionman ROSSY, the FIRST Aviation History PIONEER of the 21st CENTURY

Yves Fusion Man Rossy smiling portrait

A few days after he succeeded in crossing the Channel, I thought it was time to show who and what gave Yves Rossy the incentive to perform such breathtaking feats. Let’s have a look at this hero’s career.

When he was a child, he said « When I am older, I will be pilots » – with an S ! This became his motto from the day he got unable to go down from a tree by himself. The child has now become « Fusionman ». In order to understand what motivated this pilot, watch and listen to Yves Rossy’s comments (in French) on the video below:

As he explained, Yves Rossy has always admired the first pioneers. Every attempt used to end by death or breakthrough. Yves Rossy has now become « Fusionman », the first man flushed in a jet-engine-propelled wing, flying as if he were Icarus.

Yves Rossy was born on the 27th of August 1959 in Neufchatel – Switzerland. Both gazing skywards, and having his feet firmly planted on the ground, he was taught technical education and passed a mechanics baccalauréat. Natural-born sportsman, he has practised everything that glides, slides, or flies – surfing, waterskiing, wakeboarding, skysurfing, parachuting, aerobatics, motorcycling, rafting, hang-gliding, etc. Flying with a jet-powered wing is the crowning of a 30-year career and numerous stunts, feats, and premieres.

FIGHTER PILOT

Certainly one of the most intense periods in his career. Yves Rossy flew the supersonic Mirage III for 15 years. During this period, he flew some historical aircraft such as the Hunter or the Venom, one of the first English jet-engine fighters. He got the idea of going round Switzerland throughout several activities within a day. He carried out this feat on the 3rd of July 1991. During his trip, he flew a DC-9, went motorcycling, skiing, snowboarding, mountaineering, paragliding, mountain-biking, bungee-jumping, he flew a helicopter, went skydiving, rafting, hydrospeeding, canoeing, drove a sportscar, went hang-gliding, horse-riding, barefooting, waterskiing, wakeboarding, and finally speedboating – that’s enough… 25 vehicles were used this day along 1,000 km for 15 hours and a half! Yves Rossy is a Swiss Air Force retiree, and keeps flying the two-seater Hunter belonging to the association Amici del Hunter. He works as a captain at Swiss Airlines, and his spare-time is dedicated to his passion. He has been supported since February 2007 by Jean-Claude BIVER, HUBLOT watches’ CEO.

HE FANCIES DOING WHAT NEVER HAPPENED BEFORE

Yves Rossy is used to venturing off the beaten tracks. He devotes all his hobbies to flight in all its forms. He multiplies the tests on contrivances that change with the passing experiments. An inflatable wing made him get over the 12-kilometer distance between the two shores of Lake Geneva. Many stunts were reported such as hang-gliding over the huge Geneva spray to surf on top of it, then land on the lake to grab a waterskiing handle, and get to the shore without getting wet! Another feat – he skydived on a disk over the Matterhorn. As Yves Rossy whished to get beyond his feats and dreams, he wanted to fly with as little instrumentation as possible – like a bird with the ability to move and steer into space, he got the idea of adding scale model jet engines under a wing.

JET-POWERED WING

The first attempt occurred in March, 2003. The German Jet-Cat company supplied the engines which were added under an inflatable wing, but this trial was a failure for lacking of rigidity. He developed a rigid spreadable carbon wing built-up at ACT Composites’ in 2004. It made an indifferent start. He spun and had to drop his wing at Al-Ain airshow. The wing parachute tore, and the device was damaged. From that time, the pilot worked hard to improve the spreading of the wing and aerodynamics at the wing tips in order to provide more stability. He achieved two flights with a two-jet-engine-propelled wing in 2005. He had a narrow shave a month later: an uncontrollable sway led him to drop his wing which crashed. After a long year and two extra jet engines added, the wing became more secure. As a matter of fact, the 5’40 » over Bex – Switzerland – came up as an awaken dream for this pioneer. Since then, Yves Rossy has relentlessly been training to optimize his wing. Yves was compelled again to drop his prototype wing while in a new test flight in April 2007. The wing was seriously damaged and took a few months to be repaired. In the aftermath of this failure, Yves Rossy decided to build up a new, more reliable, higher-performance wing. Since early 2008, his wings have become more and more sophisticated.

Finally, Yves « Fusionman » « Rocketman » « Jetman » Rossy found his place in Aviation History on the 26th of September 2008, having joined Calais – France – to Dover – England. Congratulations to Yves Rossy and thanks to MEDIA IMPACT and its staff which supplied me with materials and information to write a post about Yves Rossy.

Please visit their website at: http://www.jetman.com/

Pilot Yves Rossy flying his wing


WING SPECIFICATION SHEET

  • Wingspan: 2.50 m.
  • Central part span: 1.80 m.
  • Length of a spreadable part: 35 cm.
  • Spreading device: by gas-spring completed in half a second.
  • Weight with fuel and smoke-emission device: 55 kg.
  • Dry weight: 30 kg.
  • 4 self-started Jet-Cat P200 jet-engines (thrust: 22 kg each) – stabilized in slow-running in 25 seconds.
  • Fuel: mixed with kerosene and 5% turbine oil for lubrication
  • Rating speed: 200 km/h
  • Climb-out speed: 180 km/h (330 m/min)
  • Sink rate: 300 km/h
  • Flight endurance: 10 minutes
  • Parachute: « Parachutes de France – Legend R »
  • Canopy: PD Spectra 230
  • Harness: dropped with an automatic engine-shut-off system and, an automatic parachute opening system for proper recovery.
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Why not fly NUCLEAR AIRCRAFT ?

I was reading a gripping blog in French called “Objets du ciel » (broken link) when I bumped into an amazing article written by Carl Conrad. I first thought that this post was unbelievable. I daresay that all the articles he writes are amazing. I am going to report hereafter what I have read about this topic – nuclear-powered aircraft – from different sources, but Carl Conrad’s article is the one that inspired me most.

Convair NB-36H X-6

© Photo: National museum of the USAF

As a major oil crisis is looming, airlines are cancelling some less financially viable air links of theirs. The future of aviation as we currently know it, seems to be in jeopardy. Nothing seems to be used as a substitute for any current kind of energy, not even electricity. What about nuclear-powered engines?

Nowadays, nobody would bear any nuclear-powered test flights. However those tests did occur within a USAF-carried-out weapons system (WS 125-A) nuclear-powered bomber aircraft programme. Those tests were performed with a 1,000-kilowatt-nuclear jet engine airborne on a Convair NB-36H. This aircraft named « The Crusader », took-off 47 times during the 50s. The engine was not used for propelling. It only worked at an altitude which was deemed sensible. Those tests allowed to assess the nuclear engine drive performance. Every flight would involve troops deployment in the area to prevent as soon as possible from any accident fallout spreading. The aircraft was modified in order to enhance the five crew member’s safety. The USAF considered the concept not realistic and gave the programme up in late 1956.

However, this technology might be coming back to fly some drones for long-lasting flights. People might be relunctant to see nuclear-powered drones taking-off and flying past over their heads. Who knows? Maybe some day.

Another project to mention: Project Orion should have become a 4,000-ton, long-range spacecraft powered by controlled nuclear pulses, or explosions. For this purpose, a small test vehicle was built. It was dubbed « Hot Rod », and was conventional-explosive-powered craft. Finally, Orion was cancelled in 1965 because it would not have been politically correct and because of technical challenges.

I have not found a piece of information about nuclear-powered craft after the year 2004. By the way, if someone knows further information about nuclear-powered aircraft, they will be welcome if they want to add some comments.

SPECIFICATIONS:
Span: 230 ft. 0 in.
Length: 162 ft. 1 in. (as B-36H, the NB-36H was slightly shorter)
Height: 46 ft. 8 in.
Weight: 357,500 lbs. (max. gross weight)
Armament: None
Engines: Six Pratt & Whitney R-4360-53 radials of 3,800 hp each (takeoff power) and four General Electric J47-GE-19 turbojets of 5,200 lbs. thrust each
Crew: Five ( pilot, copilot, flight engineer and two nuclear engineers)

PERFORMANCE:
Maximum speed: Approx. 420 mph at 47,000 ft.
Cruising speed: 235 mph
Service ceiling: Approx. 47,000 ft.

Sources:
http://www.nationalmuseum.af.mil/

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NASA OBLIQUE WING CONCEPT

NASA Dryden flight

A program conducted between 1979 and 1982 at the NASA Dryden Flight Research Center, Edwards, Calif., successfully demonstrated an aircraft wing that could be pivoted obliquely from zero to 60 degrees during flight. The unique wing was demonstrated on a small, subsonic jet-powered research aircraft called the AD-1 (Ames Dryden -1). The aircraft was flown 79 times during the research program, which evaluated the basic pivot-wing concept and gathered information on handling qualities and aerodynamics at various speeds and degrees of pivot.

The oblique wing concept originated with Robert T. Jones, an aeronautical

engineer at NASA’s Ames Research Center, Moffett Field, Calif.

Analytical and wind tunnel studies Jones initiated at Ames indicated that a transport-size oblique-wing aircraft, flying at speeds up to Mach 1.4 (1.4 times the speed of sound), would have substantially better aerodynamic performance than aircraft with more conventional wings. At high speeds, both subsonic and supersonic, the wing would be pivoted at up to 60 degrees to the aircraft’s fuselage for better high-speed performance. The studies showed these angles would decrease aerodynamic drag, permitting increased speed and longer range with the same fuel expenditure. At lower speeds, during takeoffs and landings, the wing would be perpendicular to the fuselage like a conventional wing to provide maximum lift and control qualities. As the aircraft gained speed, the wing would be pivoted to increase the oblique angle, thereby reducing the drag and decreasing fuel consumption. The wing could only be swept in one direction, with the right wingtip moving forward.

The AD-1 aircraft was delivered to Dryden in February 1979. The Ames Industrial Co., Bohemia, N.Y., constructed it, under a $240,000 fixed-price contract. NASA specified the overall vehicle design using a geometric configuration studied by the Boeing Commercial Airplane Company, Seattle, Wash. The Rutan Aircraft Factory, Mojave, Calif., provided the detailed design and load analysis for the intentionally low-speed, low-cost airplane. The low speed and cost of course limited the complexity of the vehicle and the scope of its technical objectives.

NASA AD-1 X-plane

Piloting the aircraft on its first flight Dec. 21, 1979, was NASA research pilot Thomas C. McMurtry, who was also the pilot on the final flight Aug. 7, 1982. Powered by two small turbojet engines, each producing 220 pounds of static thrust at sea level, the aircraft was limited for reasons of safety to a speed of about 170 mph. The AD-1 was 38.8 feet in length and had a wingspan of 32.3 feet unswept. It was constructed of plastic reinforced with fiberglass, in a sandwich with the skin separated by a rigid foam core. It had a gross weight of 2,145 pounds, and an empty weight of 1,450 pounds. A fixed tricycle landing gear, mounted close to the fuselage to lessen aerodynamic drag, gave the aircraft a very « squatty » appearance on the ground. It was only 6.75 feet high. The wing was pivoted by an electrically driven gear mechanism located inside the fuselage, just forward of the engines.

Read full article on the NASA (www.nasa.gov) website: NASA Dryden Past Projects: AD-1 Oblique Wing – updated August 12, 2009

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