Air Speed Limits
for Flaps and Landing Gear


  All Aircraft, large or small, necessarily have maximum airspeed limits for operating flaps and landing gear. Above these designated speeds, structural failure will occur due to excessive aerodynamic loads.  In the case of our radio controlled jets, knowing and adhering to these limits is especially important because of the potential for high speed.  One would think that a turbine qualified pilot would know about these restrictions, but, we have seen evidence that prompted this notice.
  Experienced R/C pilots can estimate flight speeds close enough that they will not overstress airframe components.  Staying within 20mph of a published limit is close enough for most model airplanes.  If one’s experience is insufficient, we are fortunate to now have a wide selection of Telemetry equipment to assist the R/C pilot.  Choose one that compliments your radio control system. 


  Some examples of structural failures that can result from excessive speed are:

·         Flaps – hinges broken loose from their mounting, servo gears stripped, servo arm splines stripped, linkages broken, and flap skin delamination.  This kind of damage to the flap system could cause a loss of control at approach speeds.

·         Extending the landing gear at excessive speed can damage gear doors that may interfere with the gear reaching its fully down and locked position.  Of course, excessive speed can prevent proper landing gear operation during both the “up” or “down” selection process.

  BVM publishes Vne (Velocity to never exceed) for each of our jet airframes.  These speeds are posted on the cover of each BVM instruction manual and are the result of Flight Test Evaluation by the BVM engineering and jet pilot staff.  In all cases, the 200 mph limit imposed by the A.M.A. “Turbine Waiver” rules is the controlling number.
  Since all BVM jets and most others of good design have stall speeds (Vs) in the 30-35 mph range, it is reasonable to say that safe flap and landing gear operating speeds will be very similar for most R/C Jets.
  Wing flaps serve to both increase lift and drag, but this paper is not intended to be a tutorial on the aerodynamics involved.  Rather, it is intended to caution inexperienced pilots about inflicting unnecessary stress on model jet airframes.

Suggested Flap and Gear
Operating Speeds

  Following take-off: Retract the landing gear as soon as comfortably airborne but below 100 mph.  The take-off Flap position is usually 15°-20° deflection, raise the flaps after reaching at least 70 mph but prior to 100 mph or after the first 180° turn.  Use throttle management or angle of climb to control the speed until the flaps are up.
  Prior to Landing: Slow the model to about 90 mph, then select the flaps to the 1st increment which will be the same 15°-20° used for take-off.  Extend the landing gear at 70-80 mph, and then select “Landing” flaps which will be 35°-45° of deflection.

Note: For high winds, use 30°-35° for landing.  Make this adjustment in your transmitter before flight.

  These suggested speeds will provide a safe stall margin and protect the airframe from excessive aerodynamic loads.  Certainly, we should all know that putting the gear and flaps out at 150+ mph will likely cause structural damage.

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