Aircraft Owners and Pilots Association
The Aircraft Owners and Pilots Association is a Frederick, Maryland-based American non-profit political organization that advocates for general aviation. The organization started at Wings Field in Pennsylvania. On 24 April 1932, The Philadelphia Aviation Country Club was founded at Wings Field; the country club was the location of meetings of members that founded AOPA. AOPA incorporated on May 15, 1939, with C. Towsend Ludington serving as the first president, AOPA's membership consists of general aviation pilots in the United States. AOPA exists to serve the interests of its members as aircraft owners and pilots, to promote the economy, safety and popularity of flight in general aviation aircraft. In 1971 the organization purchased Airport World Magazine, moving its operations to Bethesda, Maryland. With 384,915 members in 2012, AOPA is the largest aviation association in the world, although since 2010 it has decreased in membership from 414,224, a loss of 7% in two years. AOPA is affiliated with other similar organizations in other countries though membership in the International Council of Aircraft Owner and Pilot Associations.
In 2015, AOPA was inducted into the International Air & Space Hall of Fame at the San Diego Air & Space Museum. AOPA has several programs. AOPA Foundation, is AOPA’s 501 charitable organization; the foundation's four goals are to improve general aviation safety, grow pilot population and improve community airports, provide a positive image of general aviation. AOPA Political Action Committee, is just for AOPA members. Through lobbying, it represents the interests of general aviation to Congress, the Executive Branch, state and local governments; the AOPA PAC campaigns in favor of federal and local candidates that support their policies and oppose those who do not through advertising and membership grassroots campaigns. GA Serves America, was created to promote general aviation to the public. Legal Services Plan/Pilot Protection Services, provides AOPA members with legal defense against alleged FAA enforcement charges as well as assistance obtaining an FAA flight medical. Enrollment in Pilot Protection Services is only open to AOPA members and requires an additional payment above dues.
The Legal Services Plan was combined with the former medical program in May 2012 under the name Pilot Protection Services. The Legal Services Plan was created in June 1983. Air Safety Institute is a separate nonprofit, tax exempt organization promoting safety and pilot proficiency in general aviation through quality training, research and the dissemination of information. AOPA sponsors its own open house in Frederick Maryland; the yearly event started in 1991 with 125 aircraft. By 2001, the attendance grew to 760 aircraft; the event was cancelled for five years after the September 11th attacks, airspace changes, but resumed in 2006. Canadian Owners and Pilots Association – similar organization established in Canada in 1952 Experimental Aircraft Association – similar organization focused on homebuilt aircraft Official Website AOPA Air Safety Institute General Aviation Serves America AOPA USA's Let's Go Flying Records of the AOPA at the Hagley Museum and Library
The Flemish bend known as a figure eight bend, a double figure eight bend, a rewoven figure eight is a knot for joining two ropes of similar size. A loose figure-eight knot is tied in the end of one rope; the second rope is now threaded backwards parallel to the first rope. When properly dressed, the two strands do not cross each other. Although secure, it is susceptible to jamming. If tied and stressed properly it does not need "stopper" or "safety" knots; the Flemish bend called figure-eight bend, is given in knot monographs but is used. It is bulky and bothersome to tie, not to be preferred to the following knot, made in a similar manner. List of bend knots List of knots Flemish, or double figure eight, bend animated video by Marinews Grog. "Flemish, or figure eight, bend". Animated Knots
The two half-hitches is a type of knot a binding knot or hitch knot. It consists of an overhand knot tied around a post, followed by a half-hitch. Equivalently, it consists of a half-turn around a post followed by a clove hitch of the running end around the standing part; this knot is sometimes referred to as a clove hitch over itself, or double half-hitch. Two half hitches is the commonest of all hitches for mooring in particular and for general utility. Steel gives the name in 1794; the difference between two half hitches and the clove hitch is that the former, after a single turn around a spar, is made fast around its own standing part, while the latter is tied directly around the spar. The following three-step process for tying the two half-hitches is explained in the image gallery below. Click on the images for high-resolution versions. Begin by forming a clockwise loop around the pole, with the working end of the rope on top. Bring the working end through the loop. At this point, you have an overhand knot around the pole.
Bring the working end down and to the left. Loop it under the standing end. Pull the working end through the loop just formed and slide the knot along the standing end up to the post. A tied two half hitches resembles a clove hitch tied around the standing end of the line, not a cow hitch. To release the knot, pry apart the two hitches with a bending motion. However, it can be difficult to untie. To help avoid this problem, tie a slipped variation: in the second half-hitch, pass through a bight, as when tying your shoe, rather than the entire free end; the buntline hitch, when bent to a yard, makes a more secure knot than two half hitches, but is more liable to jam. It differs from two half hitches in that the second half hitch is inside instead of outside the first one. List of hitch knots List of knots Roper's Knots
STS-82 was the 22nd flight of the Space Shuttle Discovery and the 82nd mission of the Space Shuttle program. It was NASA's second mission to service the Hubble Space Telescope, during which Discovery's crew repaired and upgraded the telescope's scientific instruments, increasing its research capabilities and achieved the highest altitude attained by a STS Orbiter. Discovery launched from Kennedy Space Center, Florida, on 11 February 1997, returning to Earth on 21 February 1997 at Kennedy Space Center. EVA 1 Lee and Smith Start: 14 February 1997 – 04:34 UTC End: 14 February 1997 – 11:16 UTC Duration: 6 hours, 42 minutes EVA 2 Harbaugh and Tanner Start: 15 February 1997 – 03:25 UTC End: 15 February 1997 – 10:52 UTC Duration: 7 hours, 27 minutes EVA 3 Lee and Smith Start: 16 February 1997 – 02:53 UTC End: 16 February 1997 – 10:04 UTC Duration: 7 hours, 11 minutes EVA 4 Harbaugh and Tanner Start: 17 February 1997 – 03:45 UTC End: 17 February 1997 – 10:19 UTC Duration: 6 hours, 34 minutes EVA 5 Lee and Smith Start: 18 February 1997 – 13:15 UTC End: 18 February 1997 – 18:32 UTC Duration: 5 hours, 17 minutes The STS-82 mission was the second in a series of planned servicing missions to the orbiting Hubble Space Telescope, placed in orbit on 24 April 1990 by Discovery during STS-31.
The first servicing mission was done by Space Shuttle Endeavour on STS-61. Work performed by Discovery's crew upgraded the scientific capabilities of the HST and helped to keep the telescope functioning smoothly until the next scheduled servicing missions, which were STS-103 in 1999 and STS-109 in 2002. On the third day of the mission, Discovery's seven-member crew conducted the first of four spacewalks to remove two older instruments and install two new astronomy instruments, as well as perform other servicing tasks; the two older instruments being replaced were the Goddard High Resolution Spectrograph and the Faint Object Spectrograph, exchanged for the Space Telescope Imaging Spectrograph and the Near Infrared Camera and Multi-Object Spectrometer, respectively. In addition to installing the new instruments, astronauts replaced other existing hardware with upgrades and spares. Hubble received a refurbished Fine Guidance Sensor, an optical device used to provide pointing information for the telescope and as a scientific instrument for astrometric science.
The Solid State Recorder replaced one of HST's reel-to-reel tape recorders. The SSR provides much more flexibility than a reel-to-reel recorder and can store ten times more data. One of Hubble's four Reaction Wheel Assemblies -- part of the telescope's Pointing Control Subsystem—was replaced with a refurbished spare; the RWAs use angular momentum to maintain the telescope in a desired position. The wheel axes are oriented so that the telescope can provide science with only three wheels operating, if required. Study of the returned mechanism provided a rare opportunity to study equipment that had undergone long-term service in space for the effects of vacuum on lubricants which were found to be in'excellent condition'. STS-82 demonstrated anew the capability of the Space Shuttle to service orbiting spacecraft. Discovery's crew completed servicing and upgrading of the Hubble Space Telescope during four planned EVAs performing a fifth unscheduled space walk to repair insulation on the telescope.
HST deployed in April 1990 during STS-31. It was designed to undergo periodic servicing and upgrading over its 15-year lifespan, with first servicing performed during STS-61 in December 1993. Hawley, who deployed the telescope, operated the orbiter Remote Manipulator System arm on STS-82 to retrieve HST for second servicing at 3:34 am EST, 13 Feb. and positioned it above Discovery's payload bay less than half an hour later. Relying on more than 150 tools and crew aids and Smith performed EVAs 1, 3 and 5, with Harbaugh and Tanner performing EVAs 2 and 4. EVA 1 began at 11:34 pm EST, 13 February, lasted six hours, 42 minutes. One of Hubble's solar arrays was unexpectedly disturbed by a gust of air from Discovery's airlock when it was depressurized, but was not damaged. Lee and Smith removed two scientific instruments from Hubble, the Goddard High Resolution Spectrograph and Faint Object Spectrograph, replaced them with the Space Telescope Imaging Spectrograph and Near Infrared Camera and Multi-Object Spectrometer, respectively.
STIS expected to shed further light on supermassive black holes. NICMOS features more capable infrared detectors and gave astronomers their first clear view of the universe at near infrared wavelengths between 0.8 and 2.5 micrometers. EVA 2 began at 10:25 pm, 14 February, lasted seven hours, 27 minutes. Harbaugh and Tanner replaced a degraded Fine Guidance Sensor and a failed Engineering and Science Tape Recorder with new spares. Installed was a new unit called the Optical Control Electronics Enhancement Kit, which further increased the capability of the Fine Guidance Sensor. During this EVA astronauts noted cracking and wear on thermal insulation on the side of HST facing sun and in the direction of travel. EVA 3 began at 9:53 pm, 15 February, lasted seven hours, 11 minutes. Lee and Smith removed and replaced a Data Interface Unit on Hubble, as well as a reel-to-reel Engineering and Science Tape Recorder with a new digital Solid State Recorder that allowed simultaneous recording and playback of data.
Changed out was one of four Reaction Wheel Assembly units that use spin momentum to move telescope toward a target and maintain it in a stable position. After this EVA, mission managers decided to add EVA 5 to repair the thermal insulation on HST. EVA 4 began at 10:45 pm, 16 February, lasted six
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, the rotation of the Earth. Tide tables can be used for any given locale to find the predicted times and amplitude; the predictions are influenced by many factors including the alignment of the Sun and Moon, the phase and amplitude of the tide, the amphidromic systems of the oceans, the shape of the coastline and near-shore bathymetry. They are however only predictions, the actual time and height of the tide is affected by wind and atmospheric pressure. Many shorelines experience low tides each day. Other locations have a diurnal tide -- one low tide each day. A "mixed tide" – two uneven magnitude tides a day – is a third regular category. Tides vary on timescales ranging from hours to years due to a number of factors, which determine the lunitidal interval. To make accurate records, tide gauges at fixed stations measure water level over time. Gauges ignore; these data are compared to the reference level called mean sea level.
While tides are the largest source of short-term sea-level fluctuations, sea levels are subject to forces such as wind and barometric pressure changes, resulting in storm surges in shallow seas and near coasts. Tidal phenomena are not limited to the oceans, but can occur in other systems whenever a gravitational field that varies in time and space is present. For example, the shape of the solid part of the Earth is affected by Earth tide, though this is not as seen as the water tidal movements. Tide changes proceed via the following stages: Sea level rises over several hours, covering the intertidal zone; the water rises to its highest level. Sea level falls over several hours; the water stops reaching low tide. Oscillating currents produced by tides are known as tidal streams; the moment that the tidal current ceases is called slack tide. The tide reverses direction and is said to be turning. Slack water occurs near high water and low water, but there are locations where the moments of slack tide differ from those of high and low water.
Tides are semi-diurnal, or diurnal. The two high waters on a given day are not the same height; the two low waters each day are the higher low water and the lower low water. The daily inequality is not consistent and is small when the Moon is over the Equator. From the highest level to the lowest: Highest astronomical tide – The highest tide which can be predicted to occur. Note that meteorological conditions may add extra height to the HAT. Mean high water springs – The average of the two high tides on the days of spring tides. Mean high water neaps – The average of the two high tides on the days of neap tides. Mean sea level – This is the average sea level; the MSL is constant for any location over a long period. Mean low water neaps – The average of the two low tides on the days of neap tides. Mean low water springs – The average of the two low tides on the days of spring tides. Lowest astronomical tide and Chart Datum – The lowest tide which can be predicted to occur. Modern charts use this as the chart datum.
Note that under certain meteorological conditions the water may fall lower than this meaning that there is less water than shown on charts. Tidal constituents are the net result of multiple influences impacting tidal changes over certain periods of time. Primary constituents include the Earth's rotation, the position of the Moon and Sun relative to the Earth, the Moon's altitude above the Earth's Equator, bathymetry. Variations with periods of less than half a day are called harmonic constituents. Conversely, cycles of days, months, or years are referred to as long period constituents. Tidal forces affect the entire earth. In contrast, the atmosphere is much more fluid and compressible so its surface moves by kilometers, in the sense of the contour level of a particular low pressure in the outer atmosphere. In most locations, the largest constituent is the "principal lunar semi-diurnal" known as the M2 tidal constituent, its period is about 12 hours and 25.2 minutes half a tidal lunar day, the average time separating one lunar zenith from the next, thus is the time required for the Earth to rotate once relative to the Moon.
Simple tide clocks track this constituent. The lunar day is longer than the Earth day because the Moon orbits in the same direction the Earth spins; this is analogous to the minute hand on a watch crossing the hour hand at 12:00 and again at about 1:05½. The Moon orbits the Earth in the same direction as the Earth rotates on its axis, so it takes more than a day—about 24 hours and 50 minutes—for the Moon to return to the same location in the sky. During this time, it has passed overhead once and underfoot once, so in many places the period of strongest tidal forcing is the above-mentioned, about 12 hours and 25 minutes; the moment of highest tide is not when the Moon is nearest to zenith or nadir, but the period of the forcing still determines the time between high tides. Because the gravitational field created by the Moon weakens
The cow hitch is a hitch knot used to attach a rope to an object. The cow hitch comprises a pair of half-hitches tied in opposing directions, as compared to the clove hitch in which the half-hitches are tied in the same direction, it is known under a variety of names. It can be tied either with a bight. A simple and useful knotted structure, the cow hitch has been known since at least the first century when described by Greek physician Heraklas in a monograph on surgical knots and slings. Known under a variety of names, this knot has been used both at sea; the common alternate name lark's head is attributed to Tom Bowling in the 1866 work The Book of Knots, presumed to have been adapted from a French manuscript. The underlying cow hitch structure can be used in a variety of ways; these variations are differentiated by method used to form the knot and the way in which it is loaded. In particular, the knot can be formed with an end of the rope, in a closed loop or strap, or a combination of these two in which it is tied with the end and formed into a loop by securing the free end to the standing part.
Although certain names tend to be associated with a particular variations, real-world naming is not consistent between various users and applications. When tied using the end of a rope, such as when securing an animal's lead to a vertical post or stake, this knot was said to be more resistant to loosening than the clove hitch as the animal wanders around the post. In general, this single-ended form of the cow hitch is less stable compared to the variations in which both ends are loaded; this form is known as a strap hitch or girth hitch. The latter term being common among climbers, it is the method used to attach luggage tags which have a pre-tied loop of string or elastic. This form is often used to connect loop-ended lanyards to handheld electronic equipment, since it can be tied without access to the ends of the fastening loop; when tied by threading the end and the end is secured to the standing part, the knot is known as a bale sling hitch. The craft of tatting is composed of lark's head knots over carrier threads.
A lark's head is called a double stitch in tatting. In the context of friendship bracelets, the lark's head is called the reverse knot or the forward backward knot or the backward forward knot if the author is being directionally specific for instructional purposes. Another application for the cow hitch is in the handling of large electric power cable in surface mines. Known colloquially as a "Cableman's hitch", it is used to attach loops of cable to the back of a pick-up truck during a shovel move; as the cable can weigh upwards of 22 pounds per foot and 3–4 loops of cable can be attached to one length of rope, a clove hitch's shearing force would damage the cable jacket. The Cableman's hitch puts the strain onto the hitch crossing over the two running ends of the rope; the Nintendo Wiimote, for securing the strap to the Wiimote Some Mobile phones accessory use this knot to secure themselves to the phones Textile/Rubber Bands attached to the Zip Pullers is tied with Cow Hitch to reduce the size of the Puller.
Halter hitch Hoxton knot List of knots Ringbolt hitching