Generally, to achieve a smooth transition to the new altitude,  the rate of ascent should not exceed the distance to the new  altitude. For example, if the balloon pilot is 500 feet below  the desired new altitude, the rate of climb should not exceed  500 fpm. When the pilot is 300 feet below the desired altitude,  the rate of climb should not exceed 300 fpm. An ascent of  200 to 300 fpm is slow enough to detect wind changes at  different altitudes, which is helpful in maneuvering. Above  500 fpm, it is possible to fly through small, narrow wind  bands or wind with very small direction changes without  noticing. It is a good idea to launch and climb at a slow  speed (100 to 200 fpm) to make an early decision regarding  which direction to fly. into a descent. The balloon pilot must remember that each  manufacturer has a specific interval that the vent can be  opened while in flight. Should that interval be exceeded, it  can have a disastrous result. With practice and application,  the pilot can learn this skill without the use of the vent, not  only conserving fuel, but also flying a much more controlled  flight.  or 90,000 cubic foot envelope) at 5,000 feet, the pilot may be  required to make a standard burn every 15 to 20 seconds to  keep the balloon climbing at 500 feet per minute (fpm). At  sea level, the same rate may require burning only every 30  to 40 seconds. Burn rates cannot be predicted in advance, but  practice provides a basis to begin with and experimentation  finds the correct burn rate for a particular day’s ambient  temperature, altitude, envelope size, and balloon weight. Another skill to develop in ascents is knowing when to stop  burning so the balloon will slow and level at the chosen  altitude. The transition from a climbing mode to level flight  involves estimating the momentum and coasting up to the  desired or assigned altitude. One methodology is illustrated  in  Figure 7-4 . During this flight, the pilot has decided to  leave his current altitude (A) and climb to another (C). While  climbing, the pilot adjusts burn times to be at a 100 fpm rate  of climb by the time he or she is at a point 100 feet below the  desired altitude (B). Under most circumstances, the balloon  “coasts” the additional 100 feet and rounds out, or resumes  level flight, at the desired altitude. It may be necessary to  use the vent for a short time to stop the ascent with caution  not to vent excessively, thereby causing the balloon to go  A B C $_{Figure 7-4.}$  Ascent schematic. 7-5