an altitude number, hyphen, and a whole or fractional  number appear; for example, 530-1, which indicates “530  feet MSL” and 1 statute mile visibility. This is the descent  minimum for the approach. The RVR value is separated  from the minimum altitude with a slash, such as “1065/24,”  which indicates 1,065 feet MSL and an RVR of 2,400 feet.  If RVR is prescribed for the procedure, but not available, a  conversion table is used to provide the equivalent visibility  in this case, of ½ statute mile visibility.  [Figure 1-20]  The  conversion table is also available in the TPP. By knowing the layout of the airport and their particular  procedures, pilots are able to anticipate, understand, and  safely execute all ATC directives and procedures. A major  contributor to runway incursions is pilots not knowing  the airport layout and procedures. This lack of situational  awareness causes unnecessary accidents that can be avoided  by proper flight planning. The FAA believes that following  the aircraft’s progress on the airport diagram to be sure that  the instructions received from ATC are being followed is  one of the key procedures in reducing runway incursions. To  do this, pilots must take the time prior to the flight to study  all procedures so that they are not trying to learn about the  airport while they are receiving ATC instructions. The airport sketch, located on the bottom of the chart, includes  many helpful features. IAPs for some of the larger airports  devote an entire page to an airport diagram. Airport sketch  information concerning runway orientation, lighting, final  approach bearings, airport beacon, and obstacles all serve to  guide the pilot in the final phases of flight. See  Figure 1-21  for  a legend of airport diagram/airport sketch features (see also  Figure 1-10  for an example of an airport diagram). When an alternate airport is required, standard IFR alternate  minimums apply. For aircraft other than helicopters, precision  approach procedures require a 600-feet ceiling and 2 statute  miles visibility; nonprecision approaches require an 800-feet  ceiling and 2 statute miles visibility. Helicopter alternate  minimums are a ceiling that is 200 feet above the minimum  for the approach to be flown and visibility of at least 1  statute mile, but not less than the minimum visibility for the  approach to be flown. When a black triangle with a white “A”  appears in the notes section of the pilot briefing, it indicates  non-standard IFR alternate minimums exist for the airport.  If an “NA” appears after the “A” ( ), then alternate  minimums are not authorized. This information is found in  the beginning of the TPP. The airport elevation is indicated in a separate box at the  top left of the airport sketch. The touchdown zone elevation  (TDZE), which is the highest elevation within the first 3,000  feet of the runway, is designated at the approach end of the  procedure’s runway. In addition to the COPTER approaches, instrument- equipped helicopters may fly standard approach procedures.  The required visibility minimum may be reduced to one-half  the published visibility minimum for category A aircraft,  but in no case may it be reduced to less than ¼ mile or  1,200 feet RVR. Two terms are specific to helicopters. Height above landing  (HAL) means height above a designated helicopter landing  area used for helicopter IAPs. “Point in space approach”  refers to a helicopter IAP to a MAP more than 2,600 feet  from an associated helicopter landing area. Beneath the airport sketch is a time and speed table when  applicable. The table provides the distance and the amount  of time required to transit the distance from the FAF to the  MAP for selected groundspeeds. The approach lighting systems and the visual approach lights  are depicted on the airport sketch. White on black symbols  ( ) are used for identifying pilot-controlled lighting (PCL).  Runway lighting aids are also noted (e.g., REIL, HIRL), as is  the runway centerline lighting (RCL).  [Figure 1-22] The airport diagram shows the paved runway configuration  in solid black, while the taxiways and aprons are shaded  gray. Other runway environment features are shown, such  as the runway identification, dimensions, magnetic heading,  displaced threshold, arresting gear, usable length, and slope. Prior to all flights, pilots should take the time and study the  airport layout for all of the airports that they intend to land,  including those that may be used as an alternate. During  the flight planning phase, study the taxi procedures for the  departure airport and landing procedures for the arrival  airport. The expected taxi route should be checked against  the airport diagram or taxi chart, and special attention should  be given to the unique or complex intersections along the taxi  route. Pilots should identify critical times and locations on the  taxi route (e.g., transitioning through complex intersections,  crossing intervening runways, entering and lining up on the  runway for takeoff, and approaching and lining up on the  runway for landing). Certain procedures can be flown with inoperative components.  According to the Inoperative Components Table, for  example, an instrument landing system (ILS) approach  with a malfunctioning Medium Intensity Approach Lighting  System with Runway Alignment Indicator Lights (MALSR =  MALS with RAIL) can be flown if the minimum visibility is  Inoperative Components Airport Sketch /Airport Diagram 1-27