Backpack helicopter

Artist's depiction of a helibackpack with counter-rotating twin rotors

A backpack helicopter is a helicopter motor and rotor and controls assembly that can be strapped to a person's back, so that he can walk about on the ground wearing it, and can use it to fly. Its harness, like a parachute harness, should have a strap between the legs, so that the pilot does not fall out of the harness during flight.

Some designs may use ducted fan design to increase upward thrust.

Related are devices like a backpack helicopter which also include a seat and leg supports and are actually very small open-topped ordinary helicopters.

Several inventors have tried to make backpack helicopters, with mixed results.

In theory, a helicopter would be more efficient than a rocket/jet pack, possessing a greater specific impulse, and being more suited to hovering due to the smaller velocities of the propelled gases.

Backpack helicopters in popular culture

Backpack helicopters occur sometimes in fiction. All real backpack helicopters are flown with its pilot's body vertical, but there are some in fiction (for example, inDan Dare comics and the video game H.E.R.O.) which are flown with its pilot's body horizontal.

Inspector Gadget used the "Gadget 'Copter" which opened a helicopter from his hat.

Backpack helicopters are considered to be relatively popular gadget. The Martin Jetpack (which is not a jetpack, despite its name) has appeared in spy films such as the 2003 film Agent Cody Banks.

An unmanned aerial vehicle (UAV)

A RQ-2 Pioneer, a reconnaissance UAV of theRomanian Air Force during the Gulfand Iraq Wars.

Although most UAVs are fixed-wing aircraft, rotorcraft designs such as this MQ-8B Fire Scout also exist.

A MQ-9 Reaper, a hunter-killersurveillance UAV used by the United States Armed Forces andBritish Armed Forces, especially inIraq and Afghanistan.

An unmanned aerial vehicle (UAV), commonly referred to as a drone^[1] is a remotely piloted aircraft. UAVs come in two varieties: some are controlled from a remote location, and others fly autonomously based on pre-programmed flight plans using more complex dynamic automation systems. Currently, UAVs perform reconnaissance as well as attack missions. Drone attacks often kill civilians.^[1][2]

UAVs are also used in a small but growing number of civil applications, such as firefighting. UAVs are often preferred for missions that are too "dull, dirty, or dangerous" for manned aircraft.

There is a wide variety of UAV shapes, sizes, configurations, and characteristics. For the purposes of this article and to distinguish UAVs from missiles, a UAV is defined as capable of controlled, sustained, level flight and powered by a jet orreciprocating engine. Cruise missiles are not classed as UAVs, because, like many other guided missiles, the vehicle itself is a weapon that is not reused, even though it is also unmanned and in some cases remotely guided.

The abbreviation UAV has been expanded in some cases to UAVS (unmanned-aircraft vehicle system). The Federal Aviation Administration has adopted the generic class unmanned aircraft system (UAS) originally introduced by the U.S. Navy to reflect the fact that these are not just aircraft, but systems, including ground stations and other elements.

Main article: History of unmanned aerial vehicles

The earliest UAV was A. M. Low's "Aerial Target" of 1916.^[3] A number of remote-controlled airplane advances followed, including the Hewitt-Sperry Automatic Airplane, during and after World War I, including the first scale RPV (Remote Piloted Vehicle), developed by the film star and model airplane enthusiast Reginald Denny in 1935.^[3] More were made in the technology rush during the Second World War; these were used both to train antiaircraft gunners and to fly attack missions. Jet engines were applied after WW2, in such types as the Teledyne Ryan Firebee I of 1951, while companies like Beechcraft also got in the game with their Model 1001 for the United States Navy in 1955.^[3] Nevertheless, they were little more than remote-controlled airplanes until the Vietnam Era.

Front view of a MQ-1 Predator(Reno Air Show)

With the maturing and miniaturization of applicable technologies as seen in the 1980s and 1990s, interest in UAVs grew within the higher echelons of the US military. UAVs were seen to offer the possibility of cheaper, more capable fighting machines that can be used without risk to aircrews. Initial generations were primarily surveillance aircraft, but some were fitted with weaponry (such as the MQ-1 Predator, which utilized AGM-114 Hellfire air-to-ground missiles). An armed UAV is known as an unmanned combat air vehicle (UCAV).

The near future will likely see unmanned aircraft employed, offensively, for bombing and ground attack. As a tool for search and rescue, UAVs can help find humans lost in the wilderness, trapped in collapsed buildings, or adrift at sea. While air-to-air combat will likely remain the last domain of the human pilot, when unmanned fighter jets do come about, they will enjoy the advantage of almost unlimited immunity to G-force effects.

In the future, UAVs will be able to take full advantage of scramjet technology. Today's scramjets, while unmanned, see use only for testing purposes (e.g., NASA X-43A, NASA's Hyper-X scramjet program), but have the potential when developed for combat to out-maneuver even the most experienced pilots.

Radio Controlled helicopters

Nitro-powered Thunder Tiger Raptor 60

Electric-powered Venom Air Corps Ocean Rescue

Electric-powered Align T-rex 450SE

This Heli-Max Axe Micro CX model helicopter is an example of a micro-sized coaxial model. Note the size comparison with the cellular telephone at right.

Radio Controlled helicopters (also RC helicopters) are model aircraft which are distinct from RC airplanes because of the differences in construction, aerodynamics, and flight training. Several basic designs of RC helicopters exist, of which some (such as those with collective pitch) are more maneuverable than others. The more maneuverable designs are often harder to fly, but benefit from greater aerobatic capabilities.

Flight controls allow pilots to control the collective and throttle (usually linked together), the cyclic controls (pitch and roll), and the tail rotor (yaw). Controlling these in unison enables the helicopter to perform most of the manoeuvres a full-sized helicopters can do, such as hovering and backwards flight, and many that full-sized helicopters cannot.

The various helicopter controls are affected by means of small servo motors, commonly known as servos. A piezoelectric gyroscope is typically used on the tail rotor (yaw) control to counter wind- and torque-reaction-induced tail movement. This "gyro" does not apply a mechanical force, but rather, electronically adjusts the control signal to the tail rotor servo.

The engines used to typically be methanol-powered two-stroke motors, but electric brushless motors combined with a high-performance lithium polymer battery are now more common, as improved performance and decreasing prices bringing these within reach of more people. Gasoline and jet turbine engines are also used.

UAV functions

UAV functions

UAVs perform a wide variety of functions. The majority of these functions are some form of remote sensing; this is central to the reconnaissance role most UAVs fulfill. Less common UAV functions include interaction and transport.

Remote sensing

A Bell Eagle Eye, used by the US Coast Guard

The RQ-7 Shadow is capable of delivering a 20-lb. "Quick-MEDS" canister to front-line troops.

Malazgirt VTOL Mini Unmanned System operated by Turkish Armed Forces

UAV remote sensing functions include electromagnetic spectrum sensors, biological sensors, and chemical sensors. A UAV's electromagnetic sensors typically include visual spectrum, infrared, or near infrared cameras as well as radar systems. Other electromagnetic wave detectors such as microwave and ultraviolet spectrum sensors may also be used, but are uncommon. Biological sensors are sensors capable of detecting the airborne presence of various microorganisms and other biological factors. Chemical sensors use laser spectroscopy to analyze the concentrations of each element in the air.

Transport

UAVs can transport goods using various means based on the configuration of the UAV itself. Most payloads are stored in an internal payload bay somewhere in the airframe. For many helicopter configurations, external payloads can be tethered to the bottom of the airframe. With fixed wing UAVs, payloads can also be attached to the airframe, but aerodynamics of the aircraft with the payload must be assessed. For such situations, payloads are often enclosed in aerodynamic pods for transport.

Scientific research

Unmanned aircraft are uniquely capable of penetrating areas which may be too dangerous for piloted craft. The National Oceanic and Atmospheric Administration (NOAA) began utilizing the Aerosonde unmanned aircraft system in 2006 as a hurricane hunter. AAI Corporation subsidiary Aerosonde Pty Ltd. of Victoria (Australia), designs and manufactures the 35-pound system, which can fly into a hurricane and communicate near-real-time data directly to the National Hurricane Center in Florida. Beyond the standard barometric pressure and temperature data typically culled from manned hurricane hunters, the Aerosonde system provides measurements far closer to the water’s surface than previously captured. Further applications for unmanned aircraft can be explored once solutions have been developed for their accommodation within national airspace, an issue currently under discussion by the Federal Aviation Administration.

Precision strikes

See also: Unmanned Combat Aerial Vehicle

Rear view of a MQ-1 Predator(Reno Air Show)

MQ-1 Predator UAVs armed with Hellfire missiles are now used as platforms for hitting ground targets in sensitive areas. Armed Predators were first used in late 2001 from bases in Pakistan and Uzbekistan, mostly for targeted assassinations inside Afghanistan. Since then, there were several reported cases of such assassinations taking place in Pakistan, this time from Afghan-based Predators. The advantage of using an unmanned vehicle, rather than a manned aircraft in such cases, is to avoid a diplomatic embarrassment should the aircraft be shot down and the pilots captured, since the bombings took place in countries deemed friendly and without the official permission of those countries.^{[10][11][12][13]}

A Predator, based in a neighboring Arab country, was used to kill suspected al-Qa'ida terrorists in Yemen on November 3, 2002. This marked the first use of an armed Predator as an attack aircraft outside of a theater of war such as Afghanistan.^[14]

Search and rescue

UAVs will likely play an increased role in search and rescue in the United States. This was demonstrated by the successful use of UAVs during the 2008 hurricanes that struck Louisiana and Texas.

For example, Predators, operating between 18,000-29,000 feet above sea level, performed search and rescue and damage assessment. Payloads carried were an optical sensor, (which is a daytime and infra red camera), and a synthetic aperture radar. The Predator's SAR is a sophisticated all-weather sensor capable of providing photographic-like images through clouds, rain or fog, and in daytime or nighttime conditions; all in real-time. A concept of coherent change detection in SAR images allows for exceptional search and rescue ability: photos taken before and after the storm hits are compared and a computer highlights areas of damage

Endurance

RQ-4 Global Hawk, a high-altitude reconnaissance UAV capable of 36 hours continuous flight time

Because UAVs are not burdened with the physiological limitations of human pilots, they can be designed for maximized on-station times. The maximum flight duration of unmanned, aerial vehicles varies widely. Internal-combustion-engine aircraft endurance depends strongly on the percentage of fuel burned as a fraction of total weight (the Breguet endurance equation), and so is largely independent of aircraft size. Solar-electric UAVs hold potential for unlimited flight, a concept originally championed by the Aerovironment Helios Prototype, which was destroyed in a 2003 crash. One of the major problems with UAVs is no capability for inflight refuelling. Currently the US Air Force is promoting research that should end in an inflight UAV refueling capability, which should be available by 2010.

The Defense Advanced Research Projects Agency (DARPA) is to sign a contract on building an UAV which should have an enormous endurance capability of about 5 years. The project is entitled "Vulture". The developers are certain neither on the design of the UAV nor on what fuel it should run to be able to stay in air without any maintenance for such a long period of time.

Notable high endurance flights

UAV	Flight time	Date	Notes
QinetiQ Zephyr Solar Electric	82 hours 37 minutes	28-31 July 2008	QinetiQ press release
Boeing Condor	58 hours, 11 minutes	?	The aircraft is currently in the Hiller Aviation Museum, CA. Hiller Aviation Museum reference to the flight
QinetiQ Zephyr Solar Electric	54 hours	September 2007	QinetiQ press release New Scientist article
IAI Heron	52 hours	?	NOVA PBS TV program reference IAI reference
AC Propulsion Solar Electric	48 hours, 11 minutes	June 3, 2005	AC Propulsion release describing the flight
MQ-1 Predator	40 hours, 5 minutes	?	UAV Forum reference Federation of American Scientists reference
GNAT-750	40 hours	1992	Directory of US Military Rockets and Missiles reference to the flight UAV Endurance Prehistory reference
TAM-5	38 hours, 52 minutes	August 11, 2003	Smallest UAV to cross the Atlantic TAM Homepage TAM-5 FAQ page
Aerosonde	38 hours, 48 minutes	May 3, 2006	Aerosonde release on the flight
I-GNAT	38 hours, landed with 10-hour reserve	?	General Atomics reference to the flight
RQ-4 Global Hawk	36 hours	?	Space Daily story on the flight RAND Corporation report
Aerosonde "Laima"	26 hours, 45 minutes	August 21, 1998	First UAV to cross the Atlantic Aerosonde Laima page Seattle Museum of Flight
Vulture(UAV)	Has not flown. Potential endurance 5 years	?	A DARPA project - Vulture - The Unmanned Aircraft Able to Stay in the Air for 5 Years