rapidly changing aviation technology and environment  through the regulatory process. Safety regulations  would be extremely complex and unwieldy if all possible  variations and situations were addressed by regulation.  Instead, the safety standards established by regulation  should usually have a broad application that allows varying  acceptable methods of compliance. The OpSpecs provide  an effective method for establishing safety standards that  address a wide range of variables. In addition, OpSpecs  can be adapted to a specific certificate holder or operator’s  class and size of aircraft and type and kinds of operations.  OpSpecs can be tailored to suit an individual certificate  holder or operator’s needs.  All takeoffs and departures have visibility minimums (some  may have minimum ceiling requirements) incorporated  into the procedure. There are a number of methods to  report visibility and a variety of ways to distribute these  reports, including automated weather observations. Flight  crews should always check the weather, including ceiling  and visibility information, prior to departure. Never launch  an IFR flight without obtaining current visibility information  immediately prior to departure. Further, when ceiling and  visibility minimums are specified for IFR departure, both  are applicable.  Part 121 and Part 135 certificate holders have the ability,  through the use of approved OpSpecs, to use lower-than­ standard takeoff minimums. Depending on the equipment  installed in a specific type of aircraft, the crew training, and  the type of equipment installed at a particular airport, these  operators can depart from appropriately equipped runways  with as little as 300 feet RVR. Additionally, OpSpecs outline  provisions for approach minimums, alternate airports, and  weather services in Volume 3 of FAA Order 8900.1, Flight  Standards Information Management System (FSIMS).  Weather reporting stations for specific airports across  the country can be located by reviewing the CS. Weather  sources along with their respective phone numbers and  frequencies are listed by airport. Frequencies for weather  sources, such as Automatic Terminal Information Service  (ATIS), Digital Automatic Terminal Information Service  (D-ATIS), Automated Weather Observing System (AWOS),  Automated Surface Observing System (ASOS), and FAA  Automated Flight Service Station (AFSS) are published on  approach charts as well. [Figure 1-9]  Visibility is the ability, as determined by atmospheric  conditions and expressed in units of distance, to see  and identify prominent unlighted objects by day and  prominent lighted objects by night. Visibility is reported  as statute miles, hundreds of feet, or meters.  Prevailing visibility is the greatest horizontal visibility  equaled or exceeded throughout at least half the horizon  circle, which need not necessarily be continuous. Prevailing  visibility is reported in statute miles or fractions of miles.  Runway visibility value is the visibility determined for a  particular runway by a transmissometer. A meter provides  1-10  29 JUL 2010 to 26 AUG 2010 NOT FOR NAVIGATION 2010 to 26 AUG 2010  SE-2, 29 JUL 2010 to 26 AUG 2010  Conversion  RVR (feet)  Visibility (sm) 1,600  1/4 2,400  1/2 3,200  5/8 4,000  3/4 4,500  7/8 5,000  1 6,000  11/4  Figure 1-10. RVR conversion table.  F igur 1-9. Examples of weather information of various fligh t  inf orma tion publications (FLIP).  Runway Visibility Value (RVV)  Prevailing Visibility  Visibility  Ceiling and Visibility Requirements 