King Air Rule of Thumb
For King Air 200 and larger:
The approximate flight level for cruise should be equal to 4 times the flight time in minutes, not to exceed FL310 for the King Air 200, or FL330 for the B200. Or FL350 for the B350 (depending on how heavy you are); FL250 for the B1900D.
Cruise FL = 4 x (Total Minutes of Flight)
The total minutes of flight should be based on an approximate cruise TAS of 260/270 knots with additions for estimated wind component and climb/descent/approach delays.
Examples:
• A 30 minute flight should be flown at about 12 – 13,000 feet above ground level. (30 minutes x 4 = FL120, 12,000 feet).
• FL180 is appropriate for a flight lasting 45 minutes. (45 minutes x 4 = 180).
• For any flight lasting over one hour and twenty minutes (80 minutes), you should climb to the highest realistic altitude available, based on airplane weight and OAT (probably 290 – 330). Of course, without RVSM approval, your highest altitude will be FL280.
For the smaller King Air 90-series, use the 3x figure due to their lower rates of climb and lower maximum Delta P.
Source: Tom Clements, King Air Academy
Last edited by avionimc; 30th Aug 2017 at 20:48.