A powered parachute , often abbreviated PPC , and also called a motorized parachute or paraplane , is a type of aircraft that consists of a parafoil with a motor and wheels.
107-430: The FAA defines a powered parachute as a powered aircraft comprised of a flexible or semi-rigid wing connected to a fuselage so that the wing is not in position for flight until the aircraft is in motion. The fuselage of a powered parachute contains the aircraft engine, a seat for each occupant and is attached to the aircraft's landing gear. While in flight, and due to the design of the parafoil, PPCs effectively travel at
214-470: A 0 {\displaystyle a_{0}} are consistent with the ISA i.e. the conditions under which airspeed indicators are calibrated. The true airspeed ( TAS ; also KTAS , for knots true airspeed ) of an aircraft is the speed of the aircraft relative to the air in which it is flying. The true airspeed and heading of an aircraft constitute its velocity relative to the atmosphere. The true airspeed
321-403: A private pilot with a PPC rating. Powered parachutes have operated in an observation platform role by police departments, and have assisted with suspect captures, river rescues, critical infrastructure over-flights, crime scene photos, narcotics enforcement and crime suppression, at a small fraction of the cost of a police helicopter . In one case, this low-cost aviation asset was procured from
428-417: A stall is a reduction in the lift coefficient generated by a foil as angle of attack exceeds its critical value . The critical angle of attack is typically about 15°, but it may vary significantly depending on the fluid , foil – including its shape, size, and finish – and Reynolds number . Stalls in fixed-wing aircraft are often experienced as a sudden reduction in lift. It may be caused either by
535-523: A PPC are associated with wind and obstacles. Flight should not be attempted in winds exceeding 10–15 mph or in gusty conditions. Wind hazards include terrain-induced air disturbances called rotors (it is advisable to stay upwind of trees, mountains, and other obstacles that disturb the flow of the wind). Wake turbulence created by the passage of other aircraft (referred to as "wingtip vortices"), especially aircraft that are heavy, aerodynamically "dirty", and slow, pose another significant hazard. Also, since
642-425: A PPC: increasing or decreasing engine power (which controls the vertical rate of climb) and deflecting the right or left trailing edge of the parafoil—by moving the steering bars with the feet—which turns the aircraft right or left. Flaring is generally used to make fine adjustments in altitude when flying close to the ground and, in particular, when landing. In a powered parachute, flaring refers to pushing on both of
749-477: A TAS scale, which is set by entering outside air temperature and pressure altitude. Alternatively, TAS can be calculated using an E6B flight calculator or equivalent, given inputs of CAS, outside air temperature (OAT) and pressure altitude. Equivalent airspeed (EAS) is defined as the airspeed at sea level in the International Standard Atmosphere at which the (incompressible) dynamic pressure
856-507: A deep stall. Two Velocity aircraft crashed due to locked-in deep stalls. Testing revealed that the addition of leading-edge cuffs to the outboard wing prevented the aircraft from getting into a deep stall. The Piper Advanced Technologies PAT-1, N15PT, another canard-configured aircraft, also crashed in an accident attributed to a deep stall. Wind-tunnel testing of the design at the NASA Langley Research Center showed that it
963-448: A dive. In these cases, the wings are already operating at a higher angle of attack to create the necessary force (derived from lift) to accelerate in the desired direction. Increasing the g-loading still further, by pulling back on the controls, can cause the stalling angle to be exceeded, even though the aircraft is flying at a high speed. These "high-speed stalls" produce the same buffeting characteristics as 1g stalls and can also initiate
1070-596: A fixed airspeed , typically about 25–35 mph (40–56 km/h). PPCs operate safely at heights ranging from a few feet off the ground (e.g., skimming, fly-bys) to altitudes as high as 10,000+ ft (3+ km), but typical operating heights are between 500 and 1,500 feet (150 and 460 meters) above ground level ( AGL ). Equipped with a 5-15 gallon fuel tank (depending on the engine and weight limitations), PPCs can typically be flown for about three hours before requiring refueling. They have very short take-off and landing rolls, sometimes less than 100 ft (30 m). PPCs are among
1177-477: A helicopter blade may incur flow that reverses (compared to the direction of blade movement), and thus includes rapidly changing angles of attack. Oscillating (flapping) wings, such as those of insects like the bumblebee —may rely almost entirely on dynamic stall for lift production, provided the oscillations are fast compared to the speed of flight, and the angle of the wing changes rapidly compared to airflow direction. Stall delay can occur on airfoils subject to
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#17330852265621284-408: A high angle of attack and a three-dimensional flow. When the angle of attack on an airfoil is increasing rapidly, the flow will remain substantially attached to the airfoil to a significantly higher angle of attack than can be achieved in steady-state conditions. As a result, the stall is delayed momentarily and a lift coefficient significantly higher than the steady-state maximum is achieved. The effect
1391-422: A landing (and especially an engine-out landing) within the last few feet off the ground. The power-off glide ratio of a PPC ranges from 3:1 to 6:1. Glide ratio varies depending on the chute size and shape. Engine-off landings are generally safe, provided that the aircraft is within glide range of a suitable landing zone and the pilot is properly trained in the use of proper flaring technique. Although possible, it
1498-409: A lower speed. A fixed-wing aircraft can be made to stall in any pitch attitude or bank angle or at any airspeed but deliberate stalling is commonly practiced by reducing the speed to the unaccelerated stall speed, at a safe altitude. Unaccelerated (1g) stall speed varies on different fixed-wing aircraft and is represented by colour codes on the airspeed indicator . As the plane flies at this speed,
1605-476: A machinist were critical to building the cockpit frame that was completed in March 1981. Daniel Thompson, an ultralight-aircraft designer and small-engine mechanic, was brought onto the project three months later to identify a power plant for the aircraft. He fitted the aircraft with two small Chrysler engines, resulting in the first prototype P-1 aircraft. On the first day of test flight, attempts were made to simply get
1712-458: A more animal-friendly and cost-effective alternative. In 1930, a cover article in Modern Mechanix , October issue, described the project of Buddy Bushmeyer for a powered parachute . the concept of a "powered parachute" was born, and is a contributing reason why the sport is called powered parachuting, despite the fact that it actually uses a parafoil. After World War II, sport jumping became
1819-417: A multi-engine non-centreline thrust aircraft), or from less likely sources such as severe turbulence. The net effect is that one wing is stalled before the other and the aircraft descends rapidly while rotating, and some aircraft cannot recover from this condition without correct pilot control inputs (which must stop yaw) and loading. A new solution to the problem of difficult (or impossible) stall-spin recovery
1926-432: A range of weights and flap positions, but the stalling angle of attack is not published. As speed reduces, angle of attack has to increase to keep lift constant until the critical angle is reached. The airspeed at which this angle is reached is the (1g, unaccelerated) stalling speed of the aircraft in that particular configuration. Deploying flaps /slats decreases the stall speed to allow the aircraft to take off and land at
2033-462: A recreational activity, and started with the round parachutes available at that time, ranging in size from 20 to 30 feet in diameter. On October 1, 1964, Domina Jalbert applied for a patent for his new "Multi-Cell Wing" he named a " parafoil " (also known as a "ram-air" wing), which was a new parachute design. His ideas were registered as U.S. patent 3,285,546 on November 15, 1966. The possibilities of Jalbert's design quickly became apparent: because
2140-482: A risk of accelerated stalls. When an aircraft such as an Mitsubishi MU-2 is flying close to its stall speed, the sudden application of full power may cause it to roll, creating the same aerodynamic conditions that induce an accelerated stall in turning flight even if the pilot did not deliberately initiate a turn. Pilots of such aircraft are trained to avoid sudden and drastic increases in power at low altitude and low airspeed, as an accelerated stall under these conditions
2247-455: A single probe, a pitot-static tube . The static pressure measurement is subject to error due to inability to place the static ports at positions where the pressure is true static pressure at all airspeeds and attitudes. The correction for this error is the position error correction (PEC) and varies for different aircraft and airspeeds. Further errors of 10% or more are common if the airplane is flown in "uncoordinated" flight. Indicated airspeed
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#17330852265622354-493: A small loss in altitude (20–30 m/66–98 ft). It is taught and practised in order for pilots to recognize, avoid, and recover from stalling the aircraft. A pilot is required to demonstrate competency in controlling an aircraft during and after a stall for certification in the United States, and it is a routine maneuver for pilots when getting to know the handling of an unfamiliar aircraft type. The only dangerous aspect of
2461-523: A spin if there is also any yawing. Different aircraft types have different stalling characteristics but they only have to be good enough to satisfy their particular Airworthiness authority. For example, the Short Belfast heavy freighter had a marginal nose drop which was acceptable to the Royal Air Force . When the aircraft were sold to a civil operator they had to be fitted with a stick pusher to meet
2568-401: A stall is a lack of altitude for recovery. A special form of asymmetric stall in which the aircraft also rotates about its yaw axis is called a spin . A spin can occur if an aircraft is stalled and there is an asymmetric yawing moment applied to it. This yawing moment can be aerodynamic (sideslip angle, rudder, adverse yaw from the ailerons), thrust related (p-factor, one engine inoperative on
2675-413: A woman weighing 110 lbs., which allowed for better performance of the test flights. Many revisions were made during those test flights, including the addition of a vertical stabilizer, flaps, ailerons, and optimization of the parafoil trim. Ram air parafoils of the day had a flat profile and offered limited control. As a result, a more anhedral (downward curve) design was applied and ribs were added to
2782-418: Is 19% higher than V s . According to Federal Aviation Administration (FAA) terminology, the above example illustrates a so-called turning flight stall , while the term accelerated is used to indicate an accelerated turning stall only, that is, a turning flight stall where the airspeed decreases at a given rate. The tendency of powerful propeller aircraft to roll in reaction to engine torque creates
2889-410: Is a better measure of power required and lift available than true airspeed. Therefore, IAS is used for controlling the aircraft during taxiing, takeoff, climb, descent, approach or landing. Target speeds for best rate of climb, best range, and best endurance are given in terms of indicated speed. The airspeed structural limit, beyond which the forces on panels may become too high or wing flutter may occur,
2996-438: Is a condition in aerodynamics and aviation such that if the angle of attack on an aircraft increases beyond a certain point, then lift begins to decrease. The angle at which this occurs is called the critical angle of attack . If the angle of attack increases beyond the critical value, the lift decreases and the aircraft descends, further increasing the angle of attack and causing further loss of lift. The critical angle of attack
3103-443: Is a differential pressure gauge with the pressure reading expressed in units of speed, rather than pressure. The airspeed is derived from the difference between the ram air pressure from the pitot tube, or stagnation pressure , and the static pressure . The pitot tube is mounted facing forward; the static pressure is frequently detected at static ports on one or both sides of the aircraft. Sometimes both pressure sources are combined in
3210-404: Is a measure of airspeed that is a function of incompressible dynamic pressure. Structural analysis is often in terms of incompressible dynamic pressure, so equivalent airspeed is a useful speed for structural testing. The significance of equivalent airspeed is that, at Mach numbers below the onset of wave drag, all of the aerodynamic forces and moments on an aircraft are proportional to the square of
3317-478: Is based on the form of Bernoulli's equation applicable to isentropic compressible flow. CAS is the same as true air speed at sea level standard conditions, but becomes smaller relative to true airspeed as we climb into lower pressure and cooler air. Nevertheless, it remains a good measure of the forces acting on the airplane, meaning stall speeds can be called out on the airspeed indicator. The values for p 0 {\displaystyle p_{0}} and
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3424-429: Is caused by flow separation which, in turn, is caused by the air flowing against a rising pressure. Whitford describes three types of stall: trailing-edge, leading-edge and thin-aerofoil, each with distinctive Cl~alpha features. For the trailing-edge stall, separation begins at small angles of attack near the trailing edge of the wing while the rest of the flow over the wing remains attached. As angle of attack increases,
3531-611: Is commonly given in knots (kn). Since 2010, the International Civil Aviation Organization (ICAO) recommends using kilometers per hour (km/h) for airspeed (and meters per second for wind speed on runways), but allows using the de facto standard of knots, and has no set date on when to stop. Depending on the country of manufacture or which era in aviation history, airspeed indicators on aircraft instrument panels have been configured to read in knots, kilometers per hour, miles per hour. In high altitude flight,
3638-567: Is defined as M = V a {\displaystyle M={\frac {V}{a}}} where Both the Mach number and the speed of sound can be computed using measurements of impact pressure , static pressure and outside air temperature . For aircraft that fly close to, but below the speed of sound (i.e. most civil jets) the compressibility speed limit is given in terms of Mach number. Beyond this speed, Mach buffet or stall or tuck may occur. Stall (flight) In fluid dynamics ,
3745-417: Is dependent upon the airfoil section or profile of the wing, its planform , its aspect ratio , and other factors, but is typically in the range of 8 to 20 degrees relative to the incoming wind ( relative wind ) for most subsonic airfoils. The critical angle of attack is the angle of attack on the lift coefficient versus angle-of-attack (Cl~alpha) curve at which the maximum lift coefficient occurs. Stalling
3852-421: Is difficult to cause the aircraft to get into a dangerous attitude, stall , or chute collapse by means of pilot control inputs. Chute collapse is considered by many pilots to be virtually impossible with square wings. The wing is more likely to collapse with the more maneuverable, but inherently less stable, elliptical wing, but such collapses are normally followed by an immediate reflation and often go unnoticed by
3959-402: Is important information for accurate navigation of an aircraft. To maintain a desired ground track whilst flying in a moving airmass, the pilot of an aircraft must use knowledge of wind speed, wind direction, and true air speed to determine the required heading. See wind triangle . TAS is the appropriate speed to use when calculating the range of an airplane. It is the speed normally listed on
4066-480: Is increased when the wing surfaces are contaminated with ice or frost creating a rougher surface, and heavier airframe due to ice accumulation. Stalls occur not only at slow airspeed, but at any speed when the wings exceed their critical angle of attack. Attempting to increase the angle of attack at 1g by moving the control column back normally causes the aircraft to climb. However, aircraft often experience higher g-forces, such as when turning steeply or pulling out of
4173-421: Is increased. Early speculation on reasons for the crash of Air France Flight 447 blamed an unrecoverable deep stall, since it descended in an almost flat attitude (15°) at an angle of attack of 35° or more. However, it was held in a stalled glide by the pilots, who held the nose up amid all the confusion of what was actually happening to the aircraft. Canard-configured aircraft are also at risk of getting into
4280-896: Is often given in terms of IAS. Calibrated airspeed (CAS) is indicated airspeed corrected for instrument errors, position error (due to incorrect pressure at the static port) and installation errors. Calibrated airspeed values less than the speed of sound at standard sea level (661.4788 knots) are calculated as follows: V c = a 0 ( 2 γ − 1 ) [ ( q c p 0 + 1 ) γ − 1 γ − 1 ] {\displaystyle V_{c}=a_{0}{\sqrt {{\bigg (}{\frac {2}{\gamma -1}}{\bigg )}{\Bigg [}{\bigg (}{\frac {q_{c}}{p_{0}}}+1{\bigg )}^{\frac {\gamma -1}{\gamma }}-1{\Bigg ]}}}} minus position and installation error correction. This expression
4387-411: Is ordinarily accomplished on board an aircraft by an airspeed indicator (ASI) connected to a pitot-static system . The pitot-static system comprises one or more pitot probes (or tubes) facing the on-coming air flow to measure pitot pressure (also called stagnation , total or ram pressure) and one or more static ports to measure the static pressure in the air flow. These two pressures are compared by
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4494-447: Is provided by the ballistic parachute recovery system. The most common stall-spin scenarios occur on takeoff ( departure stall) and during landing (base to final turn) because of insufficient airspeed during these maneuvers. Stalls also occur during a go-around manoeuvre if the pilot does not properly respond to the out-of-trim situation resulting from the transition from low power setting to high power setting at low speed. Stall speed
4601-433: Is reduced by the wing and nacelle wakes. He also gives a definition that relates deep stall to a locked-in condition where recovery is impossible. This is a single value of α {\textstyle \alpha } , for a given aircraft configuration, where there is no pitching moment, i.e. a trim point. Typical values both for the range of deep stall, as defined above, and the locked-in trim point are given for
4708-468: Is the speed of an aircraft relative to the air it is flying through (which itself is usually moving relative to the ground due to wind). It is difficult to measure the exact airspeed of the aircraft (true airspeed), but other measures of airspeed, such as indicated airspeed and Mach number give useful information about the capabilities and limitations of airplane performance. The common measures of airspeed are: The measurement and indication of airspeed
4815-428: Is the same as the dynamic pressure at the true airspeed (TAS) and altitude at which the aircraft is flying. That is, it is defined by the equation 1 2 ρ 0 V e 2 = 1 2 ρ V 2 {\displaystyle {\frac {1}{2}}\rho _{0}{V_{e}}^{2}={\frac {1}{2}}\rho V^{2}} where Stated differently, where EAS
4922-452: Is used to maintain altitude or controlled flight with wings stalled by replacing lost wing lift with engine or propeller thrust , thereby giving rise to post-stall technology. Because stalls are most commonly discussed in connection with aviation , this article discusses stalls as they relate mainly to aircraft, in particular fixed-wing aircraft. The principles of stall discussed here translate to foils in other fluids as well. A stall
5029-423: Is very difficult to safely recover from. A notable example of an air accident involving a low-altitude turning flight stall is the 1994 Fairchild Air Force Base B-52 crash . Dynamic stall is a non-linear unsteady aerodynamic effect that occurs when airfoils rapidly change the angle of attack. The rapid change can cause a strong vortex to be shed from the leading edge of the aerofoil, and travel backwards above
5136-550: The Douglas DC-9 Series ;10 by Schaufele. These values are from wind-tunnel tests for an early design. The final design had no locked-in trim point, so recovery from the deep stall region was possible, as required to meet certification rules. Normal stall beginning at the "g break" (sudden decrease of the vertical load factor ) was at α = 18 ∘ {\textstyle \alpha =18^{\circ }} , deep stall started at about 30°, and
5243-511: The Mach number is sometimes used for reporting airspeed. Indicated airspeed (IAS) is the airspeed indicator reading (ASIR) uncorrected for instrument, position, and other errors. From current EASA definitions: Indicated airspeed means the speed of an aircraft as shown on its pitot static airspeed indicator calibrated to reflect standard atmosphere adiabatic compressible flow at sea level uncorrected for airspeed system errors. An airspeed indicator
5350-477: The critical (stall) angle of attack . This speed is called the "stall speed". An aircraft flying at its stall speed cannot climb, and an aircraft flying below its stall speed cannot stop descending. Any attempt to do so by increasing angle of attack, without first increasing airspeed, will result in a stall. The actual stall speed will vary depending on the airplane's weight, altitude, configuration, and vertical and lateral acceleration. Propeller slipstream reduces
5457-425: The weight of the aircraft plus extra lift to provide the centripetal force necessary to perform the turn: where: To achieve the extra lift, the lift coefficient , and so the angle of attack, will have to be higher than it would be in straight and level flight at the same speed. Therefore, given that the stall always occurs at the same critical angle of attack, by increasing the load factor (e.g. by tightening
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#17330852265625564-489: The ASI to give an IAS reading. Airspeed indicators are designed to give true airspeed at sea level pressure and standard temperature . As the aircraft climbs into less dense air, its true airspeed is greater than the airspeed indicated on the ASI. Calibrated airspeed is typically within a few knots of indicated airspeed, while equivalent airspeed decreases slightly from CAS as aircraft altitude increases or at high speeds. Airspeed
5671-480: The PPC off the ground. Snyder, at 150 lbs., finally tried easing the power away from full throttle at take-off, and managed to fly the craft to a height of 40 to 50 feet. Snyder had a difficult time controlling the aircraft because of the torque produced by both engines' propellers spinning in the same direction. The total flight time was 30–35 seconds at a speed of 20 to 25 mph. The P-1 flew more than 10 times, once by
5778-629: The U.S. Department of Justice, Aviation Technology Program. The I-Fly Maverick was a street-legal experimental certified aircraft designed to provide emergency medical services to the Huaorani indigenous people in the Amazon rainforest in Ecuador . It is generally illegal in the U.S. to actually hunt/shoot from any aircraft, except in very limited certain circumstances. However, a PPC is considered an ideal aircraft for initially scouting animal and herd locations in
5885-459: The United States, Part 103 ultralight PPCs (like other classes of ultralight aircraft) are not allowed to fly at night, and not over densely populated areas. However, the FAA implemented the sport pilot rule in 2004, which expanded the areas over and airspace in which light sport aircraft (LSA) PPCs can legally fly. In fact, a properly equipped PPC may even be flown at night or over metropolitan areas by
5992-517: The United States, many of the smallest single-seat PPCs are flown under 14 C.F.R. § 103 of the Federal Aviation Regulations and are classified as ultralight aircraft , which allows them to be flown without a license or flight instruction. Flight instruction is, however, highly recommended, and an average student can learn to fly a PPC safely with 5 to 10 hours of flight instruction. Two-seat PPCs are classified as light sport aircraft in
6099-506: The United States, which means the pilot must have at least a sport pilot certificate issued by the FAA to fly them. A minimum of 12 hours of flight instruction, including 2 hours of solo as a student pilot, are required to obtain this certificate. Powered parachuting is not to be confused with powered paragliding . There is often confusion about the differences between powered parachutes (PPC) and powered paragliders (PPG), both terminologically and even sometimes visually. For example, from
6206-404: The V S values above, always refers to straight and level flight, where the load factor is equal to 1g. However, if the aircraft is turning or pulling up from a dive, additional lift is required to provide the vertical or lateral acceleration, and so the stall speed is higher. An accelerated stall is a stall that occurs under such conditions. In a banked turn , the lift required is equal to
6313-475: The aircraft (as established by-design in the FAA PPC Flying Handbook). PPGs, on the other hand, almost exclusively steer using the hands to pull on the steering lines. When paragliding, an airframe is considered purely a higher end option; in fact, since a PPG wing is always to be attached to the harness, if the airframe used in a PPG failed in any way, the wing would continue to support the weight of
6420-597: The aircraft from recovering from the stall. Aircraft with rear-mounted nacelles may also exhibit a loss of thrust . T-tail propeller aircraft are generally resistant to deep stalls, because the prop wash increases airflow over the wing root, but may be fitted with a precautionary vertical tail booster during flight testing , as happened with the A400M . Trubshaw gives a broad definition of deep stall as penetrating to such angles of attack α {\textstyle \alpha } that pitch control effectiveness
6527-425: The angle of attack exceeds the critical angle, the lift produced by the airfoil decreases. The information in a graph of this kind is gathered using a model of the airfoil in a wind tunnel . Because aircraft models are normally used, rather than full-size machines, special care is needed to make sure that data is taken in the same Reynolds number regime (or scale speed) as in free flight. The separation of flow from
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#17330852265626634-438: The angle of attack must be increased to prevent any loss of altitude or gain in airspeed (which corresponds to the stall angle described above). The pilot will notice the flight controls have become less responsive and may also notice some buffeting, a result of the turbulent air separated from the wing hitting the tail of the aircraft. In most light aircraft , as the stall is reached, the aircraft will start to descend (because
6741-575: The civil requirements. Some aircraft may naturally have very good behaviour well beyond what is required. For example, first generation jet transports have been described as having an immaculate nose drop at the stall. Loss of lift on one wing is acceptable as long as the roll, including during stall recovery, doesn't exceed about 20 degrees, or in turning flight the roll shall not exceed 90 degrees bank. If pre-stall warning followed by nose drop and limited wing drop are naturally not present or are deemed to be unacceptably marginal by an Airworthiness authority
6848-417: The crash of the prototype BAC 1-11 G-ASHG on 22 October 1963, which killed its crew. This led to changes to the aircraft, including the installation of a stick shaker (see below) to clearly warn the pilot of an impending stall. Stick shakers are now a standard part of commercial airliners. Nevertheless, the problem continues to cause accidents; on 3 June 1966, a Hawker Siddeley Trident (G-ARPY),
6955-479: The critical angle of attack is reached (which in early-20th century aviation was called the "burble point"). This angle is 17.5 degrees in this case, but it varies from airfoil to airfoil. In particular, for aerodynamically thick airfoils (thickness to chord ratios of around 10%), the critical angle is higher than with a thin airfoil of the same camber . Symmetric airfoils have lower critical angles (but also work efficiently in inverted flight). The graph shows that, as
7062-560: The days or weeks prior to a hunting season, due to its naturally slower flight characteristics. During hunting season, most U.S. states have strict rules about mandatory waiting periods between the time a hunter uses an aircraft and can actually hunt, and virtually all have restrictions and serious penalties for the use of any aircraft to hunt in real-time (e.g., air-to-ground collaboration/communications). With outright bans by many states disallowing UAV use in any situation related to hunting and wildlife harassment, PPCs are considered by some to be
7169-404: The deep stall after deploying the anti-spin parachute but crashed after being unable to jettison the chute or relight the engines. One of the test pilots was unable to escape from the aircraft in time and was killed. On 26 July 1993, a Canadair CRJ-100 was lost in flight testing due to a deep stall. It has been reported that a Boeing 727 entered a deep stall in a flight test, but the pilot
7276-444: The downwash pattern associated with swept/tapered wings. To delay tip stall the outboard wing is given washout to reduce its angle of attack. The root can also be modified with a suitable leading-edge and airfoil section to make sure it stalls before the tip. However, when taken beyond stalling incidence the tips may still become fully stalled before the inner wing despite initial separation occurring inboard. This causes pitch-up after
7383-528: The equivalent airspeed. Thus, the handling and 'feel' of an aircraft, and the aerodynamic loads upon it, at a given equivalent airspeed, are very nearly constant and equal to those at standard sea level irrespective of the actual flight conditions. At standard sea level pressure, CAS and EAS are equal. Up to about 200 knots CAS and 10,000 ft (3,000 m) the difference is negligible, but at higher speeds and altitudes CAS diverges from EAS due to compressibility. Mach number M {\displaystyle M}
7490-613: The fact that some aircraft and kit builders market ultralight-class rolling airframes that can be configured with either PPG-style hand steering or PPC-style foot steering (along with wider canopy attachment points), with the later sold as a 14 C.F.R. § 103 'powered parachute'. The net result is nearly identical aircraft, albeit with different steering systems and potentially different canopy types. PPCs are considered by some to be safer than normal fixed-wing aircraft because of their inherent stability, limited response to control inputs, and stall resistance. There are two primary means to control
7597-710: The flight plan, also used in flight planning , before considering the effects of wind. True airspeed is calculated from calibrated airspeed as follows V = V c θ ( 1 + q c / p ) ( γ − 1 ) / γ − 1 ( 1 + q c / p 0 ) ( γ − 1 ) / γ − 1 {\displaystyle V=V_{c}{\sqrt {\theta {\frac {(1+q_{c}/p)^{(\gamma -1)/\gamma }-1}{(1+q_{c}/p_{0})^{(\gamma -1)/\gamma }-1}}}}} where Some airspeed indicators include
7704-446: The ground, it can be difficult for the casual observer to distinguish between the two types of aircraft in instances where the PPG is using a rolling airframe (also called a cart, trike, or quad, depending on the configuration). In simple terms, PPCs are always controlled using steering bars pushed on by the feet to operate the steering controls, and the airframe is an integral component of
7811-400: The least expensive aerial vehicles, and are considered a cost-effective way to become an aviator. A new single-seat PPC may cost as little as $ 10,000, while a two-seat PPC starts around $ 20,000. Top end two-seat PPCs may cost $ 35,000 or more, depending on options. The empty weight of a PPC can range from 200–500 lb (91–227 kg) and payload can be upwards of 500 pounds (230 kg). In
7918-432: The lift to fall from its peak value. Piston-engined and early jet transports had very good stall behaviour with pre-stall buffet warning and, if ignored, a straight nose-drop for a natural recovery. Wing developments that came with the introduction of turbo-prop engines introduced unacceptable stall behaviour. Leading-edge developments on high-lift wings, and the introduction of rear-mounted engines and high-set tailplanes on
8025-413: The locked-in unrecoverable trim point was at 47°. The very high α {\textstyle \alpha } for a deep stall locked-in condition occurs well beyond the normal stall but can be attained very rapidly, as the aircraft is unstable beyond the normal stall and requires immediate action to arrest it. The loss of lift causes high sink rates, which, together with the low forward speed at
8132-409: The mean angle of attack of the wings is beyond the stall a spin , which is an autorotation of a stalled wing, may develop. A spin follows departures in roll, yaw and pitch from balanced flight. For example, a roll is naturally damped with an unstalled wing, but with wings stalled the damping moment is replaced with a propelling moment. The graph shows that the greatest amount of lift is produced as
8239-434: The next generation of jet transports, also introduced unacceptable stall behaviour. The probability of achieving the stall speed inadvertently, a potentially hazardous event, had been calculated, in 1965, at about once in every 100,000 flights, often enough to justify the cost of development of warning devices, such as stick shakers, and devices to automatically provide an adequate nose-down pitch, such as stick pushers. When
8346-430: The normal stall, give a high α {\textstyle \alpha } with little or no rotation of the aircraft. BAC 1-11 G-ASHG, during stall flight tests before the type was modified to prevent a locked-in deep-stall condition, descended at over 10,000 feet per minute (50 m/s) and struck the ground in a flat attitude moving only 70 feet (20 m) forward after initial impact. Sketches showing how
8453-407: The occupants and motor through the harness. In addition, because PPGs use smaller low-power engines to stay within 14 C.F.R. § 103 regulations, they frequently use a higher performance parafoil that visually appears thinner and more elliptical to compensate. Any other distinctions are less clear. In the United States, all paragliding equipment must fall within 14 C.F.R. § 103, and pilot licensing (in
8560-404: The parafoil formed a wing shape upon inflation, increased glide ratios were possible and the distance traveled could likely be extended, assuming the person or payload suspended under the chute had some thrust added. With even more power, the angle of attack could be shifted, and the wing could fly level or even climb. In 1968, Lowell Farrand attempted just this, and flew a motorized version called
8667-434: The parafoil, ultimately giving the aircraft more stability and pressurization and solving the control issue. As the parafoil design and control solutions were being worked out, Thompson developed an improved airframe design, including Snyder's idea of folding landing gear for portability. The problem of torque was resolved by having the propellers counter-rotating, thus canceling out each other's torque effect. The P-2 aircraft
8774-449: The pilot has actually stalled the aircraft. This graph shows the stall angle, yet in practice most pilot operating handbooks (POH) or generic flight manuals describe stalling in terms of airspeed . This is because all aircraft are equipped with an airspeed indicator , but fewer aircraft have an angle of attack indicator. An aircraft's stalling speed is published by the manufacturer (and is required for certification by flight testing) for
8881-428: The pilot increasing the wing's angle of attack or by a decrease in the critical angle of attack. The latter may be due to slowing down (below stall speed ) or the accretion of ice on the wings (especially if the ice is rough). A stall does not mean that the engine(s) have stopped working, or that the aircraft has stopped moving—the effect is the same even in an unpowered glider aircraft . Vectored thrust in aircraft
8988-433: The pilot. In the rare circumstances where an elliptical wing collapses, the collapse is caused either by some extreme adverse meteorological condition or by pilot error. The FAA reports that over 80 percent of all aviation accidents are due to pilot error. Inflatable ram-air elliptical wings can have upward of 30 individual cells whereas square wings typically have fewer than 13 cells. The main hazards one faces while flying
9095-409: The proceeding years, additional tow-based prototypes were developed and flown. Unfortunately, heavy engines, as well as limitations in the availability of strong and light parafoil and frame materials, contributed to making the concept difficult to execute. The later development of the first mass-produced powered parachute took approximately two and one-half years. Aeronautical engineer Steve Snyder
9202-473: The real life counterparts often tend to overestimate the aerodynamic stall angle of attack. High-pressure wind tunnels are one solution to this problem. In general, steady operation of an aircraft at an angle of attack above the critical angle is not possible because, after exceeding the critical angle, the loss of lift from the wing causes the nose of the aircraft to fall, reducing the angle of attack again. This nose drop, independent of control inputs, indicates
9309-422: The separated regions on the top of the wing increase in size as the flow separation moves forward, and this hinders the ability of the wing to create lift. This is shown by the reduction in lift-slope on a Cl~alpha curve as the lift nears its maximum value. The separated flow usually causes buffeting. Beyond the critical angle of attack, separated flow is so dominant that additional increases in angle of attack cause
9416-591: The slow-moving PPC, like a helicopter, is particularly well equipped to fly safely near the ground, special care must be taken to avoid power lines, trees, and other low-level terrain obstacles. PPC pilots typically enjoy flying low and slow, and the PPC is an excellent platform for sightseeing and photography . PPCs are also used in agriculture , and occasionally by law enforcement agencies and flight search organizations. PPCs do not need an airport to take off and land. Many pilots choose and prefer to fly from back yard strips, small airports, and mowed hay fields. In
9523-458: The stall and entry to a super-stall on those aircraft with super-stall characteristics. Span-wise flow of the boundary layer is also present on swept wings and causes tip stall. The amount of boundary layer air flowing outboard can be reduced by generating vortices with a leading-edge device such as a fence, notch, saw tooth or a set of vortex generators behind the leading edge. Fixed-wing aircraft can be equipped with devices to prevent or postpone
9630-502: The stall speed by energizing the flow over the wings. Speed definitions vary and include: An airspeed indicator, for the purpose of flight-testing, may have the following markings: the bottom of the white arc indicates V S0 at maximum weight, while the bottom of the green arc indicates V S1 at maximum weight. While an aircraft's V S speed is computed by design, its V S0 and V S1 speeds must be demonstrated empirically by flight testing. The normal stall speed, specified by
9737-437: The stalling behaviour has to be made good enough with airframe modifications or devices such as a stick shaker and pusher. These are described in "Warning and safety devices". Stalls depend only on angle of attack, not airspeed . However, the slower an aircraft flies, the greater the angle of attack it needs to produce lift equal to the aircraft's weight. As the speed decreases further, at some point this angle will be equal to
9844-402: The steering bars simultaneously, which causes the left and right trailing edges of the canopy to be pulled downwards at the same time. The result of this is that the airframe moves forward of the wing (on the transverse axis), airspeed is reduced, the angle of attack increases, and the aircraft temporarily gains additional lift. Done properly, the primary benefit of this maneuver is that it softens
9951-598: The strict legal sense) is not applicable, which is not much different from ultralight PPCs. Other lines are blurred further. For example, some people previously argued that two-seat flying is only allowed using a PPC, but "tandem" (two-seat) paragliding is readily doable in many countries throughout the world, and limited types of tandem paragliding are legally authorized in the U.S. as a result of an FAA exemption for flight training only (since 2018, with subsequent extensions). With advances in lightweight material design, another contributing reason for confusion nowadays comes from
10058-423: The turn) the critical angle will be reached at a higher airspeed: where: The table that follows gives some examples of the relation between the angle of bank and the square root of the load factor. It derives from the trigonometric relation ( secant ) between L {\displaystyle L} and W {\displaystyle W} . For example, in a turn with bank angle of 45°, V st
10165-505: The upper wing surface at high angles of attack is quite different at low Reynolds number from that at the high Reynolds numbers of real aircraft. In particular at high Reynolds numbers the flow tends to stay attached to the airfoil for longer because the inertial forces are dominant with respect to the viscous forces which are responsible for the flow separation ultimately leading to the aerodynamic stall. For this reason wind tunnel results carried out at lower speeds and on smaller scale models of
10272-412: The wing is no longer producing enough lift to support the aircraft's weight) and the nose will pitch down. Recovery from the stall involves lowering the aircraft nose, to decrease the angle of attack and increase the air speed, until smooth air-flow over the wing is restored. Normal flight can be resumed once recovery is complete. The maneuver is normally quite safe, and, if correctly handled, leads to only
10379-411: The wing tip, well aft of the c.g. If the tip stalls first the balance of the aircraft is upset causing dangerous nose pitch up . Swept wings have to incorporate features which prevent pitch-up caused by premature tip stall. A swept wing has a higher lift coefficient on its outer panels than on the inner wing, causing them to reach their maximum lift capability first and to stall first. This is caused by
10486-434: The wing wake blankets the tail may be misleading if they imply that deep stall requires a high body angle. Taylor and Ray show how the aircraft attitude in the deep stall is relatively flat, even less than during the normal stall, with very high negative flight-path angles. Effects similar to deep stall had been known to occur on some aircraft designs before the term was coined. A prototype Gloster Javelin ( serial WD808 )
10593-415: The wing. The vortex, containing high-velocity airflows, briefly increases the lift produced by the wing. As soon as it passes behind the trailing edge, however, the lift reduces dramatically, and the wing is in normal stall. Dynamic stall is an effect most associated with helicopters and flapping wings, though also occurs in wind turbines, and due to gusting airflow. During forward flight, some regions of
10700-422: The “Irish Flyer I”, developed by Dr. John Nicolaides at Notre Dame University. It was a modified standard Benson gyrocopter, with the rotor removed and replaced by a 6-foot cross-member to which the parafoil was attached. The propeller was shrouded in order to avoid entanglement with the parafoil lines. Irish Flyer I was tested in the summer of 1968 by towing it aloft and releasing it for extended powered glides. Over
10807-618: Was lost to deep stall ; deep stall is suspected to be cause of another Trident (the British European Airways Flight 548 G-ARPI ) crash – known as the "Staines Disaster" – on 18 June 1972, when the crew failed to notice the conditions and had disabled the stall-recovery system. On 3 April 1980, a prototype of the Canadair Challenger business jet crashed after initially entering a deep stall from 17,000 ft and having both engines flame-out. It recovered from
10914-404: Was able to rock the airplane to increasingly higher bank angles until the nose finally fell through and normal control response was recovered. The crash of West Caribbean Airways Flight 708 in 2005 was also attributed to a deep stall. Deep stalls can occur at apparently normal pitch attitudes, if the aircraft is descending quickly enough. The airflow is coming from below, so the angle of attack
11021-751: Was completed in January 1983. Design and construction of the P-3 started on February 26, 1983. Three months later the prototype made its debut at the Sun & Fun Airshow in Florida. Response was overwhelming, and the ParaPlane Corporation was formed to produce the first commercially viable P-3 powered parachute. Since that time, many innovations and improvements have developed. There are also radio-controlled models of powered parachutes. Airspeed In aviation , airspeed
11128-420: Was first noticed on propellers . A deep stall (or super-stall ) is a dangerous type of stall that affects certain aircraft designs, notably jet aircraft with a T-tail configuration and rear-mounted engines. In these designs, the turbulent wake of a stalled main wing, nacelle-pylon wakes and the wake from the fuselage "blanket" the horizontal stabilizer, rendering the elevators ineffective and preventing
11235-513: Was implementing and perfecting the use of the square ram-air parafoils, and decided to pursue the idea and objective of creating a safe and simple aircraft that even amateurs could launch and fly easily. The first powered parachute that could take off under its own power flew in 1981 when Steve Snyder, Dan Thompson, and Adrian Vandenburg combined their talents and inspiration. It was Snyder's idea to take skydiving's newest parafoil designs and add newer (and lighter) engines, while Vandenburg's skills as
11342-578: Was lost in a crash on 11 June 1953 to a "locked-in" stall. However, Waterton states that the trimming tailplane was found to be the wrong way for recovery. Low-speed handling tests were being done to assess a new wing. Handley Page Victor XL159 was lost to a "stable stall" on 23 March 1962. It had been clearing the fixed droop leading edge with the test being stall approach, landing configuration, C of G aft. The brake parachute had not been streamed, as it may have hindered rear crew escape. The name "deep stall" first came into widespread use after
11449-402: Was vulnerable to a deep stall. In the early 1980s, a Schweizer SGS 1-36 sailplane was modified for NASA 's controlled deep-stall flight program. Wing sweep and taper cause stalling at the tip of a wing before the root. The position of a swept wing along the fuselage has to be such that the lift from the wing root, well forward of the aircraft center of gravity (c.g.), must be balanced by
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