The Mooney M20 is a family of piston-powered, four-seat, propeller-driven, general aviation aircraft, all featuring low wings and tricycle gear, manufactured by the Mooney International Corporation. The M20 was the 20th design from Al Mooney, his most successful; the series has been produced in many variations over the last 60 years, from the wooden-wing M20 and M20A models of 1955, to the M20V Acclaim Ultra that debuted in 2016. More than 11,000 aircraft in total have been produced. In November 2008, the company announced that it was halting all production as a result of the late-2000s recession, but would still provide parts and support for the existing fleet. With the injection of Chinese capital after the company's purchase, production of the M20 resumed in February 2014. Since the company has released two more M20 models. Al Mooney had been developing preliminary designs for the four-seater M20 for some time, while the single-seat M-18 Mite was in production in the late 1940s and early 1950s.
When in early 1953 the company moved from Wichita, Kansas, to Kerrville and when it became clear that the Mite was nearing the end of its production, development of the M20 accelerated. The first M20 flight took place on September 3, 1953, it was certified on August 24, 1955. During 1955, the company sold 10 of the M20 airplanes. Due to start-up costs, they lost about $3000 on each airplane. In 1956, they delivered 51 airplanes, in 1957 the total was 105; the airplane gained attention because it was able to achieve speeds up to 170 miles per hour with a 150 hp Lycoming O-320 engine. The combination of speed and efficiency was noteworthy. In 1958 the M20A joined the lineup with a larger 180 hp Lycoming O-360-A1A engine, by 1959, this was the only model offered, with a total sales that year of 231 units; this was the first year. The M20A continued production into 1960; these were the last of the Mooneys to have wooden structures in tail. Early in the model's history, several incidents of wooden tails breaking up in flight occurred due to water damage and the resulting rot.
Most tails have now been replaced with all-metal copies, as required by Mooney Service Bulletin M20-170A and the FAA Airworthiness Directive 86-19-10. Without the possibility of metal fatigue, the wooden wing has an indefinite life expectancy and is considered by some pilots to provide a smoother ride in turbulence. In January 1960, the Mooney company convinced Ralph Harmon to leave McDonnell Aircraft in St. Louis and take over management of the engineering efforts, he insisted on replacing the wood in the M20 with aluminum, the all-metal M20B was completed by the end of 1960, less than a year after his arrival. In 1961, the company sold 222 M20B airplanes; the following year, the M20C was introduced and 336 were sold that year. Known as the Mark 21 and the Ranger, the M20C had several improvements over the M20B, including greater deflection on control surfaces, reduced cowl flap openings for better engine cooling, improved exhaust scavenging with a Hanlon and Wilson exhaust system, new battery access door, more powerful landing light, lightweight floor, an increased gross weight of 2,575 pounds, lighter empty weight, new instrument panel layout, a higher maximum flap angle of 33 degrees.
In 1963, the M20D was introduced an M20C with fixed landing gear and a fixed-pitch propeller. This had a lower price than the M20C and was intended as a basic or trainer model which would have lower insurance costs and which would compete with the Piper Cherokee 180, it could be upgraded with retractable landing gear, in fact, most of them were upgraded over the years. The M20D was produced from 1963 to 1966 with a total production of 161 units. In 1964 the M20E Super 21 was introduced, it was based on the M20C but with a more powerful 200 hp Lycoming fuel-injected engine. The company sold 366 M20E units that year. In 1965, a new feature was introduced to the M20, it was a single-axis autopilot produced by Brittain Industries. It maintained the wings of the airplane in a level position unless a button on the control wheel was depressed for turns and banks, it was a controversial feature, disliked by others. Production and sales of the M20 continued to increase. In 1966, a total of 760 units was delivered, including 280 of the M20C Mark 21 planes and 473 of the M20E Super 21s.
A new model, the M20F Executive 21, offered more legroom due to a 10-inch increase in cabin length which allowed for a third fuselage side window. It had 64 US gallons of fuel capacity compared to 52 US gallons in earlier models, grossed an additional 165 pounds; this year, the company exceeded $1,000,000 in profits. The M20G Statesman, a version of the M20F with less-powerful 180 horsepower engine, was released in 1968, it had a larger airframe than the M20C, but the same engine, as a result was slower. It was not as successful as the M20F and was only produced for three years, from 1968 to 1970, with a total production run of 189 units. Despite strong sales, Mooney was short of cash; the company went into chapter 7 bankruptcy in early 1969, was acquired by American Electronics Laboratories and Butler Aviation International. Sales that year were less than half of the previous year's figures, although a new version of the M20E Chaparral was released with electrically operated flaps and landing gear.
Butler Aviation acquired the troubled Aerostar company and combined it with Mooney in an attempt to save both. The Mooney name was dropped in 1970. Butler Aviation closed the Mooney
Mooney International Corporation
The Mooney International Corporation is a Chinese-owned aircraft manufacturer, founded in 1929 by Albert Mooney and his brother Arthur. The company is based in Kerrville, United States, manufactures single-engined piston-powered general aviation aircraft. Mooney International is owned by the Meijing Group and markets the M20V Acclaim Ultra and M20U Ovation Ultra. Deliveries of the M20V Acclaim Ultra began in July 2017. Among Mooney's achievements are the first pressurized single-engined, piston-powered aircraft, the M22 Mustang. Many Mooney aircraft have the signature vertical stabilizer with its vertical leading edge and swept trailing edge that gives the illusion of being forward-swept. Albert Mooney had his first job in aviation at the age of 19 in 1925 when he worked for Alexander Aircraft Company in Denver, Colorado, he worked for the Marshall/Montague Monoplane Company in Marshall, Missouri in 1926, but the company had financial difficulties, Al soon returned to Alexander, where he designed the Alexander Bullet.
He was joined by his brother Arthur, known as Art. Early in 1929 Al was invited to meet with some financial backers in Wichita and the Mooney Aircraft Corporation was established with financial backing from the Bridgeport Machine Company; the company owned some buildings which could be used to design and build aircraft. Seven months Albert's M-5 airplane was test-flown. Due to the Great Depression, the Mooney Aircraft Corporation went bankrupt in 1930; the Mooney brothers worked for other aircraft companies, including the Culver Aircraft Company, from through World War II. On June 18, 1948, Albert started Mooney Aircraft Incorporated in Wichita, along with Charles Yankey, Art Mooney and W. L. McMahon; the first aircraft produced by the new Mooney company was the small single-seat Mooney Mite M-18. It was designed to appeal to the thousands of fighter pilots leaving military service; some thought the Mooney Mite looked so much like the Messerschmitt Bf 109 that they called it the "Texas Messerschmitt".
The Mite was produced into the early 1950s and established some of the design concepts still used by Mooney today. Al Mooney had been developing the designs for a four-seater plane for some time while the Mite was in production. In early 1953, the company moved to Kerrville and when it became clear that the Mite was nearing the end of its production, the development of the new plane was accelerated; the first M20 flight took place on September 3, 1953. Charles Yankey had been the primary financial backer since he helped Al establish the company in 1948, when he visited Kerrville for a ride in the new airplane, he was pleased with the project and began to develop the financial plans necessary to put the plane into production; that year, before Yankey transferred the funds from Wichita to Kerrville, he suffered a severe stroke, he died in December 1953. None of Yankey's heirs had any interest in the aviation business, although he had left his company stock to the two Mooney brothers, that stock had little value without further investment.
The company was on the point of declaring bankruptcy when two investors, Hal Rachal and Norm Hoffman of Midland, decided to step in and save the company. The M20 was certified in September 1955. Shortly thereafter, Albert Mooney left the company for unknown reasons and went to work for the Lockheed Aircraft Corporation in Marietta, Georgia, his brother Art joined him there, both remained with Lockheed until retirement. During 1955, Mooney sold 10 of the M20 airplanes. Due to start-up costs, they lost US$3000 on each airplane. Production increased, they delivered 51 airplanes in 1956 and 105 airplanes in 1957; the M20 gained attention because it was able to achieve speeds of up to 170 miles per hour with a 150 hp Lycoming O-320 engine. The combination of speed and efficiency was noteworthy. In 1958 the M20A joined the lineup with a larger 180 hp Lycoming O-360-A1A engine, by 1959 this was the only model offered, with a total sales that year of 231 units; this was the first year. The M20A continued production into 1960.
These were the last of the Mooneys to have wooden structures in tail. Since Al Mooney's departure, John W. Taylor had been the chief engineer. In January 1960, the Mooney company convinced Ralph Harmon to leave McDonnell Aircraft and take over management of the engineering efforts, he had worked for Beech Aircraft where he headed the design of the Beechcraft Model 35, one of the first all-metal general aviation monoplanes. He worked on the larger Cessna 620 and McDonnell Model C119, but his interests lay with small aircraft, he accepted Mooney's offer, he insisted on replacing the wood in the M20 with aluminum, the all-metal M20B was completed by the end of 1960, less than a year after his arrival. In 1961 the company sold 222 M20Bs; the following year a refined version of the M20B, was introduced. Rachal and Harmon were not experienced at running an aircraft factory, but saw the need to expand the product line and add dealers, pushed ahead. In 1963 they introduced the M20D an M20C with fixed landing gear and a fixed-pitch propeller.
This had a lower price than the M20C and was intended as a basic or trainer model which would have lower insuranc
Piper PA-28 Cherokee
The Piper PA-28 Cherokee is a family of two- or four-seat light aircraft built by Piper Aircraft and designed for flight training, air taxi and personal use. The PA-28 family of aircraft comprises all-metal, single-engined, piston-powered airplanes with low-mounted wings and tricycle landing gear, they have a single door on the copilot side, entered by stepping on the wing. The first PA-28 received its type certificate from the Federal Aviation Administration in 1960 and the series remains in production to this day. Current models are the Warrior and the Archer TX and LX; the Archer was discontinued in 2009, but with investment from new company ownership, the model was put back into production in 2010. The PA-28 series competes with the high-winged Cessna 172 and the low-winged Grumman American AA-5 series and Beechcraft Musketeer designs. Piper has created variations within the Cherokee family by installing engines ranging from 140 to 300 hp, offering turbocharging, retractable landing gear, constant-speed propeller and stretching the fuselage to accommodate six people.
The Piper PA-32 is a larger, six-seat variant of the PA-28. The PA-32R Saratoga variant was in production until 2009. At the time of the Cherokee's introduction, Piper's primary single-engined, all-metal aircraft was the Piper PA-24 Comanche, a larger, faster aircraft with retractable landing gear and a constant-speed propeller. Karl Bergey, Fred Weick and John Thorp designed the Cherokee as a less expensive alternative to the Comanche, with lower manufacturing and parts costs to compete with the Cessna 172, although some Cherokees featured retractable gear and constant-speed propellers; the Cherokee and Comanche lines continued in parallel production, serving different market segments for over a decade, until Comanche production was ended in 1972, to be replaced by the Piper PA-32R family. The original Cherokees were the Cherokee 150 and Cherokee 160, which started production in 1961. In 1962, Piper added the Cherokee 180 powered by a 180-horsepower Lycoming O-360 engine; the extra power made it practical to fly with all four seats filled and the model remains popular on the used-airplane market.
In 1968, the cockpit was modified to replace the "push-pull"-style engine throttle controls with quadrant levers. In addition, a third window was added to each side, giving the fuselage the more modern look seen in current production. Piper continued to expand the line rapidly. In 1963, the company introduced the more powerful Cherokee 235, which competed favorably with the Cessna 182 Skylane for load-carrying capability; the Cherokee 235 featured a Lycoming O-540 engine derated to 235 horsepower and a longer wing which would be used for the Cherokee Six. It included tip tanks of 17-gallon capacity each, bringing the total fuel capacity of the Cherokee 235 to 84 gallons; the aircraft had its fuselage stretched in 1973. The stabilator area was increased, as well. In 1973, the marketing name was changed from "235" to "Charger". In 1974, it was changed again to "Pathfinder". Production of the Pathfinder continued until 1977. No 1978 models were built. In 1979, the aircraft was given the Piper tapered wing and the name was changed again, this time to Dakota.
In 1964, the company filled in the bottom end of the line with the Cherokee 140, designed for training and shipped with only two seats. The PA-28-140 engine was modified shortly after its introduction to produce 150 horsepower, but kept the -140 name. In 1967, Piper introduced the PA-28R-180 Cherokee Arrow; this aircraft featured a constant-speed propeller and retractable landing gear and was powered by a 180-horsepower Lycoming IO-360-B1E engine. A 200-hp version powered by a Lycoming IO-360-C1C was offered as an option beginning in 1969 and designated the PA-28R-200. At the time the Arrow was introduced, Piper removed the Cherokee 150 and Cherokee 160 from production; the Arrow II came out in 1972, featuring a five-inch fuselage stretch to increase legroom for the rear-seat passengers. In 1977, Piper introduced the Arrow III, which featured a semitapered wing and longer stabilator, a design feature, introduced on the PA-28-181 and provided better low-speed handling, it featured larger fuel tanks, increasing capacity from 50 to 77 gallons.
The first turbocharged model, the PA-28R-201T, was offered in 1977, powered by a six-cylinder Continental TSIO-360-F engine equipped with a Rajay turbocharger. A three-bladed propeller was optional. In 1979, the Arrow was restyled again as the PA-28RT-201 Arrow IV, featuring a "T" tail that resembled the other aircraft in the Piper line at the time. In 1971, Piper released a Cherokee 140 variant called the Cherokee Cruiser 2+2. Although the plane kept the 140 designation, it was, in fact, a 150-hp plane and was shipped as a four-seat version. In 1973, the Cherokee 180 was named the Cherokee Challenger and had its fuselage lengthened and its wings widened and the Cherokee 235 was named the Charger with similar airframe modifications. In 1974, Piper changed the marketing names of some of the Cherokee models again, renaming the Cruiser 2+2 the Cruiser, the Challenger to the Archer and the Charger to Pathfinder. Piper reintroduced the Cherokee 150 in 1974, renaming it the Cherokee Warrior and giving it the Archer's stretched body and a new, semitapered wing.
In 1977, Piper stopped produ
Continuous track called tank tread or caterpillar track, is a system of vehicle propulsion in which a continuous band of treads or track plates is driven by two or more wheels. This band is made of modular steel plates in the case of military vehicles and heavy equipment, or synthetic rubber reinforced with steel wires in the case of lighter agricultural or construction vehicles; the large surface area of the tracks distributes the weight of the vehicle better than steel or rubber tyres on an equivalent vehicle, enabling a continuous tracked vehicle to traverse soft ground with less likelihood of becoming stuck due to sinking. The prominent treads of the metal plates are both hard-wearing and damage resistant in comparison to rubber tyres; the aggressive treads of the tracks provide good traction in soft surfaces but can damage paved surfaces, so some metal tracks can have rubber pads installed for use on paved surfaces. Continuous tracks can be traced back as far as 1770 and today are used on a variety of vehicles, including bulldozers, excavators and tractors.
Polish mathematician and inventor Józef Maria Hoene-Wroński conceived of the idea in the 1830s. The British polymath Sir George Cayley patented a continuous track, which he called a "universal railway". In 1837, a Russian inventor Dmitry Zagryazhsky designed a "carriage with mobile tracks" which he patented the same year, but due to a lack of funds and interest from manufacturers he was unable to build a working prototype, his patent was voided in 1839. Although not a continuous track in the form encountered today, a dreadnaught wheel or "endless railway wheel" was patented by the British Engineer James Boydell in 1846. In Boydell's design, a series of flat feet are attached to the periphery of the wheel, spreading the weight. A number of horse-drawn wagons and gun carriages were deployed in the Crimean War, waged between October 1853 and February 1856, the Royal Arsenal at Woolwich manufacturing dreadnaught wheels. A letter of recommendation was signed by Sir William Codrington, the General commanding the troops at Sebastopol.
Boydell patented improvements to his wheel in 1854 – the year his dreadnaught wheel was first applied to a steam engine – and 1858, the latter an impracticable palliative measure involving the lifting one or other of the driving wheels to facilitate turning. A number of manufacturers including Richard Bach, Richard Garrett & Sons, Charles Burrell & Sons and Clayton & Shuttleworth applied the Boydell patent under licence; the British military were interested in Boydell's invention from an early date. One of the objectives was to transport Mallet's Mortar, a giant 36 in weapon, under development, but, by the end of the Crimean war, the mortar was not ready for service. A detailed report of the tests on steam traction, carried out by a select Committee of the Board of Ordnance, was published in June 1856, by which date the Crimean War was over the mortar and its transportation became irrelevant. In those tests, a Garrett engine was put through its paces on Plumstead Common; the Garrett engine featured in the Lord Mayor's show in London, in the following month that engine was shipped to Australia.
A steam tractor employing dreadnaught wheels was built at Bach's Birmingham works, was used between 1856 and 1858 for ploughing in Thetford. Between late 1856 and 1862 Burrell manufactured not less than a score of engines fitted with dreadnaught wheels. In April 1858, "The Engineer" gave a brief description of a Clayton & Shuttleworth engine fitted with dreadnaught wheels, supplied not to the Western Allies, but to the Russian government for heavy artillery haulage in the Crimea, in the post-war period. Steam tractors fitted with dreadnaught wheels had a number of shortcomings and, notwithstanding the creations of the late 1850s, were never used extensively. In August 1858, more than two years after the end of the Crimean War, John Fowler filed British Patent No. 1948 on another form of "Endless Railway". In his illustration of the invention, Fowler used a pair of wheels of equal diameter on each side of his vehicle, around which pair of toothed wheels ran a'track' of eight jointed segments, with a smaller jockey/drive wheel between each pair of wheels, to support the'track'.
Comprising only eight sections, the'track' sections are essentially'longitudinal', as in Boydell's initial design. Fowler's arrangement is a precursor to the multi-section caterpillar track in which a large number of short'transverse' treads are used, as proposed by Sir George Caley in 1825, rather than a small number of long'longitudinal' treads. Further to Fowler's patent of 1858, in 1877, a Russian, Fyodor Blinov, created a tracked vehicle called "wagon moved on endless rails", it was pulled by horses. Blinov received a patent for his "wagon" in 1878. From 1881 to 1888 he developed a steam-powered caterpillar-tractor; this self-propelled crawler was tested and featured at a farmers' exhibition in 1896. Steam traction engines were used at the end of the 19th century in the Boer Wars, but neither dreadnaught wheels nor continuous tracks were used, rather "roll-out" wooden plank roads were thrown under the wheels as required. In short, whilst the development of the continuous track engaged the attention of a number of inventors in the 18th and 19th centuries, the general use and exploitation of the continuous track belonged to the 20th century.
A little-known American inventor, Henry T. Stith, developed a continuous track prototype which was, in multiple forms, patented in 1873, 1880, 1900; the last
General Aviation represents the'private transport' and recreational flying component of aviation. General aviation is the name or term given to all civil aviation aircraft operations with the exception of commercial air transport or aerial work, they are flight activities not involving commercial air transportation of passengers, cargo or mail for remuneration or hire, or an aerial work operation such as agriculture, photography, surveying and patrol, search and rescue, aerial advertisement, etc. It covers certain commercial and private flights that can be carried out under both visual flight and instrument flight rules, such as light aircraft and private jets or helicopters. General aviation thus represents the'private transport' component of aviation; the International Civil Aviation Organization defines civil aviation aircraft operations in three categories: General Aviation, Aerial Work and Commercial Air Transport. The International Council of Aircraft Owner and Pilot Associations includes the following definitions for General Aviation aircraft activities: Corporate Aviation: Company own-use flight operations Fractional Ownership Operations: aircraft operated by a specialized company on behalf of two or more co-owners Business Aviation: self-flown for business purposes Personal/Private Travel: travel for personal reasons/personal transport Air Tourism: self-flown incoming/outgoing tourism Recreational Flying: powered/powerless leisure flying activities Air Sports: Aerobatics, Air Races, Rallies etc.
In 2003 the European Aviation Safety Agency was established as the central EU regulator, taking over responsibility for legislating airworthiness and environmental regulation from the national authorities. Of the 21,000 civil aircraft registered in the UK, 96 percent are engaged in GA operations, annually the GA fleet accounts for between 1.25 and 1.35 million hours flown. There are 28,000 Private Pilot Licence holders, 10,000 certified glider pilots; some of the 19,000 pilots who hold professional licences are engaged in GA activities. GA operates from more than 1,800 airports and landing sites or aerodromes, ranging in size from large regional airports to farm strips. GA is regulated by the Civil Aviation Authority, although regulatory powers are being transferred to the European Aviation Safety Agency; the main focus is on standards of airworthiness and pilot licensing, the objective is to promote high standards of safety. General aviation is popular in North America, with over 6,300 airports available for public use by pilots of general aviation aircraft.
In comparison, scheduled flights operate from around 560 airports in the U. S. According to the U. S. Aircraft Owners and Pilots Association, general aviation provides more than one percent of the United States' GDP, accounting for 1.3 million jobs in professional services and manufacturing. Most countries have authorities that oversee all civil aviation, including general aviation, adhering to the standardized codes of the International Civil Aviation Organization. Examples include the Federal Aviation Administration in the United States, the Civil Aviation Authority in the United Kingdom, Civil Aviation Authority of Zimbabwe in Zimbabwe, the Luftfahrt-Bundesamt in Germany, the Bundesamt für Zivilluftfahrt in Switzerland, Transport Canada in Canada, the Civil Aviation Safety Authority in Australia, the Directorate General of Civil Aviation in India and Iran Civil Aviation Organization in Iran. Aviation accident rate statistics are estimates. According to the U. S. National Transportation Safety Board, in 2005 general aviation in the United States suffered 1.31 fatal accidents for every 100,000 hours of flying in that country, compared to 0.016 for scheduled airline flights.
In Canada, recreational flying accounted for 0.7 fatal accidents for every 1000 aircraft, while air taxi accounted for 1.1 fatal accidents for every 100,000 hours. More experienced GA pilots appear safer, although the relations between flight hours, accident frequency, accident rates are complex and difficult to assess. Environmental impact of aviation List of current production certified light aircraftAssociationsAircraft Owners and Pilots Association Canadian Owners and Pilots Association Experimental Aircraft Association General Aviation Manufacturers Association National Business Aviation Association International Aircraft Owners and Pilots Associations European General Aviation Safety Team "No Plane No Gain" website about business aviation Save-GA.org website concerned with General Aviation in the United States "GA price index". Flight International. 13 Oct 1979
In road vehicles, the parking brake called hand brake, emergency brake, or e-brake, is used to keep the vehicle stationary and in many cases perform an emergency stop. Parking brakes on older vehicles consist of a cable connected to two wheel brakes at one end and the other end to a pulling mechanism, operated with the driver's hand or foot; the mechanism may be a hand-operated lever, at floor level beside the driver, or a straight pull handle located near the steering column, or a pedal located beside the drivers leg. In most automobiles the parking brake operates only on the rear wheels, which have reduced traction while braking; some automobiles have the parking brake operate on the front wheels, for example most Citroens manufactured since the end of World War II, the early models of the Saab 900. The most common use for a parking brake is to keep a vehicle motionless; the parking brake has a ratchet or other locking mechanism that will keep it engaged until manually released. On vehicles with automatic transmissions, this is used in concert with a parking pawl in the transmission.
A recent variation is the electric parking brake. First installed in the 2001 BMW 7 Series, electric parking brakes have since appeared in a number of vehicles. Two variations are available: In the more-traditional "cable-pulling" type, an electric motor pulls the parking brake cable on the push or pull of a button rather than a mechanical pedal or handle in the cabin. A more complex unit uses a computer-controlled motor attached to each of the two rear brake calipers referred to as the Motor on Caliper system, it is expected. Jaguar, Land Rover, BMW, Subaru and VW have a system where the parking brake engages when the engine is stopped and is released when the gas pedal is pressed. An extension of this system, called the hill-hold function, prevents roll-back when stopping and starting on a hill; the OEM can turn off the system. Some electric parking brakes function similar to "park" on an automatic transmission and will not engage when the vehicle is in motion, there is no emergency brake in this case.
The emergency brake was intended for one particular emergency and, "no other way to stop", as was the case when the footbrake failed due to a loss of hydraulic pressure or other issue. Drivers had to respond when brakes failed, so they were expected to learn how to stop a speeding vehicle using the emergency brake alone. Safety regulations became universal by 1980, so modern brake systems are reliable, using dual-circuit hydraulics and more low-brake-fluid sensors; as modern brakes no longer cause emergencies in normal contexts, it is no longer necessary for the average driver to learn to use this brake for emergencies. Some drivers benefiting from the "park" function on their automatic transmissions do not use this brake at all. After a lack of recent braking emergencies, automakers stopped using the term and started referring it by its other use, the "parking brake" though the ability to function at a high speed was still there. On an increasing number of modern vehicles, the parking brake can only be engaged when the vehicle is at a stop, they no longer have an emergency brake.
The emergency brake in some cars is mechanical. In a car with a mechanical emergency brake, the driver would be able to apply the brake if there was a complete loss of hydraulic pressure and a stopped engine. Parking brakes do not stop well, as the stopping force provided is less than half the force of normal braking and takes much longer to stop a vehicle. Parking brakes provide much less braking than what a car with power braking would provide. For vehicles with manual transmissions, the mechanical parking brake is used to assist in "hill starts" as this frees both feet for use on the accelerator and clutch pedals. An unskilled motorist can get started without rolling backwards, it is inadvisable to use rear wheel parking brakes when the standard brakes are available, unless there is a problem with the front wheels such as a tire blowout or slippery conditions risking skidding and a loss of control. Using the parking brake while driving changes the traction balance between the front and rear of the vehicle, if over applied may lock the back wheels and skid the car into a handbrake turn.
Handbrake turns are intentionally used in street racing and offroad rally racing to initiate rear wheel drift. In conditions near freezing where it is both wet and icy, the parking brake mechanics may freeze and be impossible to release until thawed. If only using the "park" function on a transmission to hold the car parked, there is no freezing problem; the parking brake is used to keep a parked manual transmission car from unintentionally moving when it is parked on a hill. Though it is possible to keep a parked manual transmission car in place by putting it in gear in the opposite direction of the slope, the parking brake is still used, as if the engine were to lose compression, the car could roll forward; as a further precaution, some driving instructors tell students to point the wheels of hill-parked standard transmission ca