INSTRUMENTS FLIGHT PLANNING
Next, check both the existing and forecast local weather for your estimated time of departure.
Check the bases and tops of cloud layers, freezing level, crosswind, and runway temperature or
pressure (density) altitude, when required. Do not neglect T/O weather in flight planning. If the
local weather dictates, plan for the measures that must be taken to prepare the aircraft for entry
into freezing clouds, such as pitot heat, engine inlet anti-ice, etc. On days when the weather is
below available approach minimums, discretion requires a plan for a suitable T/O alternate
airport where you can land safely should an emergency occur after T/O. A minute of planning
for this possibility may pay rich dividends later.
Check the winds along the route of flight through a considerable range of altitudes. This allows
the selection of the best altitude for aircraft performance, and gives you a feel for the change in
aircraft performance you can expect if you are given a change in altitude enroute. Look
specifically for the extent of clouds that may be present along the proposed route. Check the
altitude of the tops and bottoms of the clouds. When clouds are present and flight is conducted
on instruments along the route, keep in mind the location of the nearest area that is VFR for
letdown and landing in the event of complete radio failure or other emergency.
You must carefully ascertain the possibility of any hazards to flight along your proposed route.
Know the altitude of the freezing level and the likelihood of icing. Do not plan a flight for
extended periods in clouds with a temperature just below freezing for this is the level of
maximum icing. Check for the likelihood of thunderstorms and turbulence and avoid them
whenever possible. If avoidance is not possible, plan to minimize their effect. The presence of
fog, low ceiling, and low visibility areas along the route are additional hazards. Know the
location of these areas before leaving the weather office. A look at the Weather Depiction Chart
or the sequence reports discloses areas that are near or below IFR minimums.
You must know, in detail, the weather to be expected at your destination. If the weather is
forecast to be IFR, analyze it closely, then carefully choose the alternate(s). Look for ceiling and
visibility, precipitation; amount of snow, if present; RCR or equivalent runway braking action;
forecast wind and the likelihood of crosswinds to the runway; the effect of surrounding
topography on weather conditions at the field, etc. Check on the possibility of a delay in landing
due to the presence of heavy showers or squalls at the destination. Always try to choose an
alternate with better weather than the destination.
Before obtaining a flight clearance, you must receive a verbal weather briefing in person, by
telephone or by weather vision. Additionally, a DD 175-1 (Flight Weather Briefing Form) is
completed for all IFR flights. The verbal briefing contains a detailed analysis of present and
forecast weather in the immediate vicinity of the departure point, along the flight route, and at
the destination and alternate airfield(s). All potential hazards to flight are included.
IN-FLIGHT WEATHER ANALYSIS 7-3