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Old Jan 06, 2010, 08:16 PM
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racer1's Avatar
United States, AZ, Tucson
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FYI BVM Makes a statement about 200mph limit for Turbines.

From BMV website

IN DEFENSE OF OUR SPORT

Question:

Why do we have a 200 mph limit on turbine powered model airplanes?

Answer:

Because it is recognized by knowledgeable and experienced people in the A.M.A. and JPO (Jet Pilots Organization) that the introduction of gas turbine engines into model aircraft facilitated speeds previously unobtainable.

The exhaust gas velocity of some model jet engines can exceed 1000 mph and the thrust to weight ratios can easily exceed 1:1.

NOTE: Other model airplane propulsion systems do not have the potential for excessive speed and therefore are not speed restricted.

For sure, some model jet airframes can exceed 200 mph and survive, and a specifically designed model aircraft could yield speeds in the 300 to 400 mph range, but common sense and experience tells us to operate within our A.M.A. Turbine Waiver limits.

The Jet Pilots Organization, along with the A.M.A. safety committee established the 200 mph limit for turbine model operation in 2000 for all of the reasons stated within this informational document. The physics and facts have not changed since then.

Recently, internet posts and jet event reports have surfaced confirming that a few individuals do not respect the A.M.A. regulations or are ignorant as to why they were adopted and in force today.

Additionally, these individuals do not possess the engineering background to fully comprehend the forces that the model is subjected to as the velocity and “G’s” increase. See ENCLOSURE І: TECHNICAL INFORMATION later in this document.

Perhaps these individuals don’t realize that we live in a post 9/11 era and that our sporting activity is under scrutiny by agencies of local, state, and federal governments. The turbine powered model airplane is of particular interest to the entities.

HOW TO DEFEND OUR SPORT

A model airplane is defined by the A.M.A. as a line of site, non-autonomous vehicle. In the case of a gas turbine powered model, its maximum velocity is restricted to 200 mph. We can best defend our sport by self policing and abiding by this definition and other restrictions defined in the A.M.A. Turbine Waiver document (see below). We must not give any indication or examples to agencies of higher authority that the model airplane crosses these lines.

Unfortunately, some individuals have already violated the definition of the model jet and have bragged about it on the internet. Some damage has been done because actions do have consequences. Is it fair that our sport should be put in jeopardy for the purpose of self promotion of a few individuals?

The model industry does not have, nor could we afford, a certifying bureaucracy such as the F.A.A. Should we attract further attention of this or similar governmental agencies, we are finished as a sporting entity.

If you enjoy this sport as much as I have since its inception, you might consider being more proactive in protecting it. This means, operating within our defined limits, encouraging your fellow jet pilots to do so as well, and avoid irresponsible, flaunting, internet posts.

I am sure there will be some critics of this plea to defend our sport, but I hope they will give sufficient thought before they inflict more damage via the internet. Please do not let opinions out speak the facts.

We have been a bit lucky with our good safety record and freedom of operation. Let us not rely on luck in the future.

Thank you for your consideration,

Bob Violett

POST SCRIPT:

After showing this document to a few other accomplished jet modelers, the question arose: Do these individuals still have their A.M.A. Turbine Waivers?

Reference:

Please read:

A.M.A. Turbine Waiver: www.modelaircraft.org/files/510-a.pdf

Technical Information Enclosure І

Speed Control Devices

ENCLOSURE І

TECHNICAL INFORMATION

FORCES ON AN AIRFRAME

The dynamic pressure on an airframe is defined as the maximum pressure force available in a flow field relative to the true airspeed. These forces are defined by the equation: q = 1/2 σ V ^2 with "σ" defined as air density on a vehicle and “V” as the velocity in ft/sec.

An example of force (pressure) acting on the forward facing surfaces of a typical model jet such as a BVM Ultra Bandit is:

25.2 lb/sq ft at 100 mph

56.7 lb/sq ft at 150 mph

100.8 lb/sq ft at 200 mph

157.5 lb/sq ft at 250 mph

226.8 lb/sq ft at 300 mph

308.8 lb/sq ft at 350 mph

The effect of speed and radius of the turn on “G” forces is:

F = (mv^2)/r where “F” is force, “r” is radius, “m” is mass and “v” is velocity

As the true airspeed of an aircraft doubles from 150 mph to 300 mph, it experiences four times the “G-loading” when performing a simple level turn of a similar radius. This means that even a large mile radius (1320 foot) turn requires a hefty 4.56g “pull” at 300 mph under standard, sea level conditions while it’s only 1.14g at 150 mph. Additionally, when this turn radius is halved to 1/8 mile, the load factor doubles to 9.12g! Thus it is easy to envision how more aggressive maneuvering required to keep a 300 mph aircraft in comfortable visual range or to set up for speed runs can easily impact huge aerodynamic loads on a structure.

Every control surface has a critical flutter speed dependant on its area, weight, hinge moment, and electro/mechanical control system.

Every flying surface has a deflection resistance to a control input that is velocity and “G” dependant.

Full scale aircraft are properly funded to afford professional engineering and wind tunnel testing. This data and flight testing establish the VNE (Velocity to Never Exceed) and maximum positive and negative “G” limits. These vehicles are then safe to operate as published.

Model jets are sporting vehicles that do not have these advantages nor are the assemblers, pilots, and maintenance crews similarly trained.

For a model company to be able to honestly publish a V.N.E. of 300+ mph, the product would not be affordable as a sporting device. Model airplane developers rely primarily on comparative and intuitive engineering; therefore, the end product is just a model airplane with corresponding performance limitations.

www.bmvjets.com

__________________________________________________ _____________________

Since high power EDFs are closing in on 200 mph how much does this apply to us as a group?

In the future will we be required to obtain a waiver to fly a High Power EDF?

Are we as safe as can be or do we believe it could not happen to us?

Just wondering since were are begining to fly Turbine aircraft with EDF power and most people do not know the difference.

Clay
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Old Jan 06, 2010, 08:31 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,229 Posts
Quote:
Originally Posted by racer1 View Post
Since high power EDFs are closing in on 200 mph how much does this apply to us as a group?

In the future will we be required to obtain a waiver to fly a High Power EDF?

Are we as safe as can be or do we believe it could not happen to us?

Just wondering since were are begining to fly Turbine aircraft with EDF power and most people do no know the difference.

Clay
I worry too, I think his fear is that there are some folks out there blatantly thumbing their finger @ the turbine limits, enough so that they may cause a crackdown on us all, and not from the AMA. Remember the times we live in, these "toys" unfortunately can be used for other purposes and if we wrankle the wrong agencies, the ones that really don't care what we think or use the will of the people as an indicator on how to conduct business, we may all end up with nothing. It's not that far fetched...

Jack
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Old Jan 06, 2010, 08:37 PM
John Green
USA, FL, St Petersburg
Joined Dec 2007
616 Posts
We've already had an instance in the last few months where our field was closed by the FAA because of 'government' aircraft due to be transiting the area. If they start watching us closer we will all have no place to play.
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Old Jan 06, 2010, 09:32 PM
Renegade Fun Forever!!
rvincent's Avatar
Fontana, California, United States
Joined Jul 2004
27,250 Posts
If you all think for even an instant that "speed limits" will stop the bad guys, you are sadly mistaken!

WAKE UP AMERICA!!!
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Last edited by rvincent; Jan 09, 2010 at 09:19 PM. Reason: Absolute BS!
Old Jan 06, 2010, 09:39 PM
Faster!
Joshua Wesley's Avatar
United States, NV, Sparks
Joined Oct 2004
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I would like to express my opinion on the matter, but do you think this should be in the Politics section? I'm trying to resist, as I believe in the separation of EDF and state....
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Old Jan 06, 2010, 09:46 PM
Faster!
Joshua Wesley's Avatar
United States, NV, Sparks
Joined Oct 2004
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Quote:
Originally Posted by racer1 View Post
From BMV website

Full scale aircraft are properly funded to afford professional engineering and wind tunnel testing. This data and flight testing establish the VNE (Velocity to Never Exceed) and maximum positive and negative G limits. These vehicles are then safe to operate as published.
Ever heard of the Expermintal Catigory of aircraft as outlined in the FARs. This has made aviation a reality for many that can not afford to own and maintain a certified aircraft.

-Joshua
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Old Jan 06, 2010, 09:48 PM
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racer1's Avatar
United States, AZ, Tucson
Joined Feb 2007
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My orgininal intent was the questions I posted at the end. There are general questions about the EDF group as a whole.

Clay

Questions are posted again.


Since high power EDFs are closing in on 200 mph how much does this apply to us as a group?

In the future will we be required to obtain a waiver to fly a High Power EDF?

Are we as safe as can be or do we believe it could not happen to us?

Just wondering since were are begining to fly Turbine aircraft with EDF power and most people do not know the difference.
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Last edited by racer1; Jan 07, 2010 at 10:44 PM.
Old Jan 06, 2010, 09:57 PM
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Fontana, California, United States
Joined Jul 2004
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I would like to believe that we all do our very best to be safe and use our best skills in preparation. We all know that things can fail unexpectedly and cause crashes. These are more of a rarity than real life practice. It is the guys that fly like they are tossing around a 6oz foamy that worry me and I feel it is our duty as other modelers to make them aware of dangerous situation they place us all in. If these pilots continue, then they need to have their field privledges revoked.. The problem with this course of action is we end up with guys flying 17+lb models capable of 150 mph or more flying from unapproved AMA locations and furthering their dangerous practices. How can you police the ones that are above "reproach" or meaningful suggestions for safety?
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Old Jan 06, 2010, 10:00 PM
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Eddie P's Avatar
United States, NV, Reno
Joined Mar 2000
7,069 Posts
What the Flip? Only terrorists will own model airplanes? Come on.

Back to reality. Bob V. may not be my personal buddy... I don't know him... but he makes a valid point, albeit a little over the top. I get he's trying to make a point, and a plea, so I understand.

The speed limit was an arbitrary, cheezy number a few bean counters picked. But it is what it is. And we do live in a brave new world, I don't care "who y'are". Besides, with an exponential increase in stress with speed, it's fair to say much over 250 and the numbers start to pile up quickly out of favor of normal building techniques and potential for aerodynamic issues.

EDF guys, expect another bean counter rule headed our way with much more of the speed contest stuff that ends up dragging down the forum anyhow. We can let sleeping dogs lie or go around making slogans and chasing windmills, waking the big dogs up. But Don Quixote would charge! By all means, do as you like.
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Old Jan 06, 2010, 10:10 PM
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rvincent's Avatar
Fontana, California, United States
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Not what I meant Eddie, and certainly not a statement about Bob Violet's writing. I agree there should be a respectable speed limit placed on model planes. BUT the fact will remain that if you place a speed limit on us for anything other than safety reasons it will fail. This is why model rocket builders can only buy up to "G" sized motors until they are "qualified" on larger motors. I think rather than an all out ban on speed it should be a "teired" program. Much like Top Fuel race car drivers have now. Of course even this will only work at AMA sanctioned events. What individuals do when flying solo or at a parking lot somewhere is beyond what we can control.
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Old Jan 06, 2010, 10:29 PM
Team White Llama!
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Joined Jan 2008
8,144 Posts
When EDF's go in, they don't burn.

The batteries might smoke a bit, but that's it.
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Old Jan 06, 2010, 10:39 PM
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Joined Mar 2000
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So I went off a little bit about the terrorist RC pilots. No offense intended... Anyhow, I think the big goal is to not get a speed limit slapped on us or requirement for some sort of watt per pound limit, etc. We certainly do NOT need any of that. Getting the smoke back into the bottle won't happen once the top comes off.
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Old Jan 06, 2010, 10:43 PM
Carbon fiber is our friend
Steve C's Avatar
United States, CA, Lodi
Joined Feb 2001
4,192 Posts
Lipos can burn from a crash. I've seen it.

You can argue safefy all day long, but I'd feel safer watching a 250 mph model being flown by Eddie than a 150 mph one by someone who should be flying a trainer.

Steve
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Old Jan 06, 2010, 11:00 PM
Watts is life...
rcjetpilot's Avatar
Bot's like to know where you live
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BV has a point on the speed issue, at 300+ mph, one has to wonder the length of time the aircraft is actually visible for rc piloting

Bob
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Old Jan 06, 2010, 11:45 PM
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lavochkin's Avatar
Mokena,Illinois -United States
Joined Oct 2006
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I had one go in and it went up like a flare thrown in a gasoline tanker. Edf's can be pretty flammable.Granted it was a foam jet on a 2500mah 4s brand new pack and it was into tarmac. Not like a 300mph flying napalm turbine, but plenty enough to start a wildfire or someones house on fire. Its all about being prepared. And common sense. I think everyone should need a fire extinguisher regardless if electric,glow,gas, etc....
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