Speed Sense & Common Sense

by: Bob Violett
September 2015

  Safety concerns for operating high performance turbine powered model aircraft have been addressed multiple times on BVMJets.com/Safety Issues page dating back to the year 2000. 
  Recent observations by myself and other experienced jet pilots of a few  "close calls" prompts this reminder about the extra "personal responsibility" that turbine pilots are expected to exercise in the pursuit of their hobby. All of the important points have been addressed in the "Safety Page" of this website, but it may be timely to review a few of the most glaring violations in this missive.

Vne = Velocity to Never Exceed

  The AMA "Turbine Waiver" regulations states that all turbine power model aircraft operating under AMA jurisdiction shall have a maximum velocity of 200 mph. Single engine thrust shall not exceed 45 pounds, and multiple engine thrust should not exceed 50 pounds combined. There are also weight classes defined in this document AMA #110409. In many cases, this Vne is too high for some models and pilots. Responsible manufacturers publish the maximum safe (and tested) Vne for their jet models - usually it can be found on the front page of the assembly and operation manual of each airframe product.
  If the model you are flying does not have a published Vne, consult the manufacturer or one of their representatives to get an answer. Otherwise, it would be prudent to limit the vehicle to 150 mph if there are any concerns about the internal integrity of the airframe. This is even more important now because most airframes are highly prefabricated from the manufacturer and inspection of all internal glue joints is not possible.

Rated Engine Thrust

  Installing a larger, more powerful turbine engine than is recommended by the airframe manufacturer, has a few undesirable consequences. Sure, you can dial down the maximum thrust, but the increased idle thrust adds challenges on landing. The total weight of the model increases by the combination of the engine weight and extra fuel required, adding structural stress loads during high "G" maneuvering. And, unless the internal engineering is professionally accomplished, the heat inside the model can increase significantly. The temptation to use all of the available thrust could result in a structural failure. Operating a model jet at high altitude locations such as Mexico City (7,382' AMSL) would be a possible exception to this caution.


  Manned aircraft have strict time and number of cycles maintenance checks that must be performed to F.A.A. standards. Our in-the-shop hobby time can be partially dedicated to similar inspections and corrective actions. The BVM jets "Safety Issues" pages have numerous articles relating to "Glue Joints", operating in "Bumpy Air", "Speed Control Devices", "Wing Stress Cracks", "Servo Control Arms", "Things Still Come Loose", etc. etc. There is a lot of experience derived information there.

Flight Line Safety

  Low altitude passes should not occur over the runway, but rather an additional 60-70 feet beyond the far edge of the runway. In my opinion "Low Altitude" should be defined as nothing lower than 10 feet above the ground. This would prevent any possibility of bodily injury, if for any reason, a person might be on the field. We cannot rely on flight line communications, they are subject to human error.

Common Sense - A Final Word

  Please know that government regulatory agencies are observing our activity at events and model club facilities. It is sensible to error on the safe side. The future of our exciting, challenging, and most rewarding sport depends on every jet pilot's acceptance of this extra "Personal Responsibility".


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