by Jonathan M. Stern
The airport sketch contains a simple diagram of the airport, the runway lengths and widths, the approach lighting systems available on the runways, and other information about the airport. The highest point along the first 3,000 feet of runway, the touchdown zone, is shown by the letters TDZE. Airport elevation, the highest point on any usable runway, is also shown.
The airport sketch also shows where the approach course lies relative to the primary runway. This is helpful, particularly on non-precision approaches, in visualizing how to complete the approach and land on the runway after obtaining visual contact with the airport.
Also contained in the airport sketch section of the IAP chart is a table of times corresponding to groundspeeds. For example, these times must be used on a non-terminal VOR approach where there is no DME capability. On other types of approaches, they provide a backup for other indications that the missed approach point has been reached.
For ILS approaches, the NOS publishes a rate of descent table that provides the requisite rate of descent for maintaining the glideslope with a given combination of glideslope angle and groundspeed. The glideslope angle is the angle formed by the glideslope and the runway surface and is most often 3.0 degrees. The glideslope angle can be taken from the profile view section of the chart.
To use either the time data in the airport sketch or the descent data in the rate of descent table, groundspeed on the final approach must be estimated.