RADIO CONTROL JETS
Jim Hiller, 6090 Downs Rd., Champion OH 44481
History of Turbine Rules
This is an interesting time in jet modeling. Last year the AMA requested that we review the turbine rules and work toward simplifying them. This was to have been the first complete cleansing of the turbine rules since their inception. A brief history of the rules will help you understand how we arrived where we are.
The AMA Safety Code had a rule that disallowed the operation of jet model aircraft. The initial turbine rules were implemented to allow development of turbine modeling in the United States with AMA's support by use of a pilot waiver. This waiver allowed the holder to operate a model aircraft in a prescribed manner.
AMA's leadership recognized jet modeling as a new direction our hobby was taking and established a process to support our turbine-modeling activity. This was a bold step.
Since that initial set of rules, the process of change has primarily been through the addition of new rules and documents as knowledge and needs progressed. This resulted in confusion, less-than-ideal rules for turbine modelers, and even a few difficult situations for AMA to administer. It became time to review the complete package: identify the necessary, useful items, and dispose of those no longer deemed necessary. This would make the rules understandable and consistent.
The latest Safety Code recognizes the waiver process and specifically refers to document 513: AMA Safety Regulations for Model Aircraft Gas Turbines. This document is the basis for what a modeler must do to obtain a turbine waiver and what is expected of him or her after attaining the waiver.
Rule Revision Process
Now the hard part: how do we rewrite the rules? A group of experienced turbine modelers from the Jet Pilot's Organization (JPO), our Special Interest Group, was brought together to review the rules and, based upon experiences gained from the operation of turbines in the past few years, submitted a revised set of rules to the AMA Safety Committee.
Keep in mind that active turbine modeling is not even a decade old in this country; we are still in a learning and growing stage. Amazingly, few members of the AMA leadership have had the opportunity to become involved firsthand in turbine modeling to understand the unique issues of this type of modeling and its safety implications. It was not expected that the rules suggested by this group would be adopted as submitted. They were to provide guidance to the Safety Committee for improving the turbine rules. Once accepted by the Safety Committee, the Executive Council would have the final vote on these rules.
I could get into specific rules and why they evolved, but pending further input from the modeling community and the business community, the final approval is on hold. A release date is set for 2004. I'll wait for final approval, and then I will discuss them in detail so all of us can understand them.
Perceptions and Safety
This experience has made me aware of a huge gap in beliefs between active turbine modelers and those who are not involved in turbine modeling—mainly as they relate to perceived safety issues. Turbine modelers spend a lot of time talking within the turbine modeling community about these issues, but seldom do we address people outside our group.
Jet models are fast compared to the typical sport-model aircraft. Are they faster than racing aircraft? Not really. A typical sport jet will have a top level-flight speed of roughly 120 to 160 mph. It is difficult to get an open-flow-path turbine up to level-flight speeds faster than 160 mph, regardless of how much power you put in it or how steep you dive it. Some clean airframes with larger turbines and full-flow ducting will fly faster, but most are typically not flown wide open except briefly during flight.
Propeller-driven racing-class aircraft typically possess similar speed potential, with some advanced-level race classes exceeding 200 mph. An aircraft with this speed potential, whether turbine-powered or piston-powered, when flown as a sport model can achieve greater speeds in a power dive. This means that higher speeds can be attained, but this is not common practice.
The perceived difference of opinion is that most turbine modelers feel this speed is not excessive, but they do recognize that it requires a different attitude about our responsibility in operating these aircraft. Outside the turbine modeling community it appears that people believe our models are regularly going faster than 200 mph and that the issue of speed and the energy of our aircraft is dangerous and cannot be dealt with.
What is my opinion? I fly turbine models with performance all the way up to and including some clean airframes that can approach the 200 mph mark, so I am biased. My bias is based on my experience and approach to operating our aircraft. What and who is right? All I can say is, "That's why we have an AMA Safety Committee."
Are there any magic products out there to limit speed? Maybe, but they are not yet in common use. Don't be surprised if that isn't the next technology that develops into mainstream use.
Operational Practices and Etiquette
The issue of aircraft speed was dealt with inside the turbine modeling community. At all of the jet meets I attended last year a common theme was in place. At the pilot briefings it was stated that no high-speed maneuvers that would place the model flying in the direction of the safety line were to be performed in front of the crowd. This means no high-speed circles or rolling circles in front of the crowd.
Violations of this rule were treated like a violation of the safety line: the first offense would be a warning along with a request to land, and the second offense meant you were done for the day. This etiquette is the standard in turbine modeling, and at no time did I see anyone violate this rule.
This rule is based on the belief that an aircraft tends to crash in the direction it is heading, so don't point the aircraft at people. This is the standard in the full-scale air-show community. For years it has worked successfully in the United States, and it has been adopted by the jet modeling community.
We didn't have such a practice in place until a few years ago. As new modelers came into the jet community, they brought their past modeling experience and with that some of the maneuvers they performed with their slower aircraft. Maneuvers such as the rolling circle and figure eight immediately became a concern when they started appearing at jet meets. Contest directors (CDs) and active turbine modelers informally talked, agreed that this practice was uncomfortable, and almost immediately instituted the new standard practice.
Safety Fence Requirement
Input from turbine CDs commonly related to the requirement of a safety fence the entire length of the flightline. It is expensive, but it works.
This requirement grew out of the unusual situation we have of high ground speeds on takeoff and landing because of a typical jet's wing loading combined with slow throttle response. A turbine-powered model's typical liftoff speed is roughly 40 mph. You have to be a good driver to fly jets—particularly in a crosswind and on pavement.
Is this fence issue unusual? Based on my experience, it is not. Every club I have belonged to in the past 20 years has had a similar safety fence in place at the local field to protect the pilots and pit area. This is merely an extension of the norm.
Eurofighter — A Sport Turbine Model
That is enough about rules and perceived turbine operational issues. I want to write about something fun!
I've had some good stick time on a variety of Eurofighters, and they are fun airplanes. As I am writing this, two companies supply Almost Ready-to-Fly (ARF) kits for Eurofighters: FiberClassics and Composite-ARF. Rumor has it that Mecca Models will have its Eurofighter in production by the time this column is published.
This model makes a great sport turbine model. The basic Eurofighter design has been around for a few years and has become popular as an intro-level turbine model. The Eurofighter has a huge delta wing, providing excellent low-speed stability and maneuverability.
All three manufacturers utilize advanced composite-construction techniques that keep this model light for its size, so low speed is the Eurofighter's forte. If you follow the balance and control setup instructions carefully, you can be assured that your model will display the same maneuverability and stability as the prototypes.
The latest version I flew was Paul Pigneri's Eurofighter, complete with a scale, flat-black paint job. Paul added gear doors, fiberglass inlet ducting, and a cockpit to complete his model. He powered it with one of his Artes Eagle turbines—28 pounds of thrust with a 31-pound empty weight.
The best part of flying Paul's Eurofighter is pulling on the stick. Nothing turns and rolls as aggressively as the Eurofighter. The only thing you need is plenty of power to overcome the huge drag of the delta wing at the high angles of attack you can attain with this model.
If you are looking for a nice pattern-flying aircraft, look elsewhere. Enjoy this one for its maneuverability. A large, light model such as this with a wing that allows you to comfortably pull on the elevator without fear of stalling makes for a sweet, slow-landing model.
Resources
- FiberClassics: www.fiberclassics.com
- Composite-ARF: www.composite-arf.com
- Mecca Models (distributed by Planes Plus): www.planesplus.com
Transcribed from original scans by AI. Minor OCR errors may remain.
