Typical high altitude controlled descent (QGH/NDB) let down pattern for a combat aircraft
A point that lies at 83 degrees 42 minutes North and 14 degrees 30 minutes East may be expressed in lettered coordinates as TSMA 4230.
The procedure adopted commencing from the top of the descent at the end of cruising through the approach for landing. It does not include the terminal part of the final approach. The various types of letdown are the NDB (nondirection beacon) letdown, radar letdown, en route descent, pipeline descent, QGH, etc. The procedure for letdown is given in the instrument approach charts. The illustration indicates a high-altitude letdown procedure by combat aircraft using a radio compass or a direction finder. See also instrument approach chart