Page 35 - Volume 16 Number 10

the critical (usually left) engine producing no thrust and its propeller windmilling, and the “good” engine at maximum sea-level power. It’s a worst-case scenario condition. Any change from those conditions means VMC is lower. We don’t have the information in the POH to tell us by how much. Most of the time, however, VMC becomes lower than VSO for the airplane’s weight at the time.Certainly, when you reduce power for landing, and especially when you go to idle or near-idle for your flare, VMC ceases to be a concern. So, although many multiengine manufacturers recommend VMC+5 knots as an “over the fence” or “50- foot” target speed for landing, the red radial has no real consequence as an aerodynamic factor in the final seconds of your arrival.Do the MathAll of these speeds are published at the maximum gross weight of the aircraft. The speeds are really secondary indications of the airplane’s angle of attack. And optimal AoA will result in different indicated airspeeds at reduced airplane weight.The formula for calculating the change in speed is:Speed (current weight/maximum weight) = Square root (current weight/maximum weight)A quick in-your-head calculation within the weight and speed ranges of most of our airplanes is that the proper speed reduces about two knots for every 100 pounds the airplane currently is below maximum gross weight.Picking the SpeedSo, what is the correct speed for final approach in your airplane? The “most correct answer” is the speed tabulated for the airplane’s weight in the Landing Performance section of your Pilot’s Operating Handbook (POH) or Approved Flight Manual (AFM). The speedOCTOBER 2012TWIN & TURBINE • 33Experience CountsThirty five years of serving General AviationPhoto courtesy of Pilatus Business Aircraft LTD / Photo by Jon Youngblut Photography140 E. Town Street, Suite 1400 • Columbus, Ohio 43215-1400 (614) 221-5773 • Fax: (614) 221-2411email: scope@parknationalbank.com www.ScopeAircraftFinance.comMember ofNational Aircraft Finance Association National Business Aviation AssociationMAdE IN THE USA$1370 $1785Phone (954) 966-7329 FAX: (954) 966-3584 5614 SW 25 St., Hollywood, FL 33023 web: www.survivalproductsinc.comemail: sales@survivalproductsinc.com