THE 50/50 TAKE-OFF
 or
 50 knots I.A.S. at 50% of Available Strip Length

Suggested for pilots flying any single engine normal production built aircraft - departing or taking off on any airstrip or runway surface under any wind or gradient conditions at any height and at any temperature - where doubt may exist on accurate data on strip length and/or surface conditions including wind strength and direction

FIRST THING TO DO
 
 Find the "middle" of the airstrip, that is, pace out the airstrip and find half or 50% of the result
 
 Mark this position on the side of the airstrip and make sure it will be visible to the pilot during the take-off
 
 TAKE-OFF
 
 On take-off monitor the airspeed indicator and make sure it is reading 50 knots or above as this marked mid-way point is passed - IF NOT ABORT THE TAKE-OFF!

  • You need 50 knots indicated at the halfway point
It is far better to remove some weight from the aircraft - if you have aborted - before trying again
 
 Consider leaving a passenger at the airstrip to be picked up later after you have deposited some of your "weight" at a nearby longer runway - (a real life situation encountered a few times in over 40 years flying in single-engine light aircraft ..ed)


 RISK FACTOR
 
 THE 50/50 RULE - use at your own risk not to be substituted for official Flight Manual requirements

The above calculation¹ is based on the requirement that all FAR 23 certified S/E aircraft (i.e. ...production aircraft - not home built) must have a stall speed not above 60 knots and therefore the (recommended) take-off safety speed would be not more than 70 knots

¹ The calculation is based on the requirement to be at 70% of this "take-off safety speed" speed at 50% of the take-off distance as described in the publication by H H Hurt, Jr, "Aerodynamics for Naval Aviators" page 393 and issued (in the U.S.A. 1960) by the Office of the Chief of Navel Operations - Aviation Training Division


Published December 14 - 1998
EXIT