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Need information on small turbine jets

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Need information on small turbine jets

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Old 04-19-2019, 06:30 AM
  #26  
rhklenke
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Originally Posted by BarracudaHockey View Post
I suspected that was the intent of the 12 pound limit, that and these rules were written when there were 2 or 3 options for sub 12 pound full house turbine planes.

I think there are many models available now that are sub 12 pounds dry, and they bring turbine flying to the average modeler that we (the AMA) need to find a way to accommodate them if that is what they want to fly, and that is what they can afford to fly.
About Turboprops. I see them quite a bit, but the guys currently flying them have jet waivers, either because thats what they also flew, or because that was the only route to a waiver at the time. TBH that's nice to provide that rating but I think thats a small sub-segment of a relatively small segment of the hobby. I think a lot more folks are or could be affected if the letter of the law is followed with the 12 pound limit than will ever be by the turbo prop waivers.

To be frank, I think my Avanti and Viper (both sub 12 pounds even wet) are more difficult to fly than my 25 pound 100n Havoc GTS will be. And both the Viper and Avanti are full house with flaps and retracts, neither are in the category of a P20 Funjet yet both fail to make the weight for a waiver flight.

Bob, how many JPO members are there right now?

One more set of musings. To me, knowledge of proper turbine operations, fire response, flight line safety, crash response, fuel handling etc are far more important to me as a turbine CD inspector (for lack of a better word) than how much the plane weighs.
Andy,

Currently, there are somewhere around 200 JPO members, that's out of 1800'ish waiver holders. As you know, you don't have to be a member of the JPO to be a waiver holder. We wish our membership was larger, of course, but it is what it is.

On the other hand, the JPO represents *all* of the jet community, not just JPO members - hence my asking for this information and discussion. We are the primary liason between the AMA (who has to represent over 200,000 members), and the relatively small jet community. We have been asked by the AMA about the 12 lb issue and what we think should be done about it.

With respect to the knowledge issue (which I agree with), we're working with a group of folks, both JPO members and non-JPO members, on a "recommended training syllabus" for the turbine waiver, and along with that will come training materials that can be used to convey that knowledge.

Bob
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Old 04-19-2019, 07:42 AM
  #27  
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Default Small jet

I have a Jet Teng Viper. It weighs 9.5 lbs dry. It has a T-45 turbine installed and the wingspan is 54". It carries 1.1 liter of fuel.


Bob Neal
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Old 04-19-2019, 07:52 AM
  #28  
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Thanks for the info. Bob!
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Old 04-19-2019, 08:55 AM
  #29  
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Bob,
There could be some "accidental" wisdom in the 12 pound minimum. Seems strange it only applied to waiver flights?
It's conceivable to me someone could take a small light weight airplane air-frame, that might not really be safe and bolt almost any turbine on, thus creating a missile.
Seems that a better standard would be more of a power to weight ratio?

I don't feel this should be a pilot skill discussion since that seems next to impossible to quantify for a hobby activity.
For waiver flights, the most a CD can do is look for minimum ability for the airplane being flown. No way to go much past that.

But minimum air-frame weights could be some benefit for AMA purposes from a safety view-point. Seems too small with the wrong turbine could be as much a risk as too big (larger than 55, etc)
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Old 04-19-2019, 09:14 AM
  #30  
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After reviewing all the comments above I agree a 2 step waiver is desirable and listed my first thoughts, see below.


Primary Turbine Waiver:
1. Model Dry Weight 18lbs or less.
2. Wing Loading 40oz square ft or less
3. Power to Weight 1 to 1 or less.

Advanced Turbine Waiver
1. Model Dry Weight over 18lbs
2. Wing Loading over 40oz square ft
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Old 04-19-2019, 09:59 AM
  #31  
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Originally Posted by sidgates View Post
After reviewing all the comments above I agree a 2 step waiver is desirable and listed my first thoughts, see below.


Primary Turbine Waiver:
1. Model Dry Weight 18lbs or less.
2. Wing Loading 40oz square ft or less
3. Power to Weight 1 to 1 or less.

Advanced Turbine Waiver
1. Model Dry Weight over 18lbs
2. Wing Loading over 40oz square ft
So the 12lb model would still be the dividing line for the waiver flight? That's what I was thinking.
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Old 04-19-2019, 11:44 AM
  #32  
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Originally Posted by causeitflies View Post

So the 12lb model would still be the dividing line for the waiver flight? That's what I was thinking.
On the other thread in the other forum, it was suggested that K-60 powered models will be over 12lbs (dry) - thus likely over 16 lbs wet, and for it to be under 12 lbs (dry), its going to be powered by a K-45 or smaller?

So it sounds like the 12 lbs dry is actually a good dividing line...

The question then, is what to do about the less than 12 lbs dry models? Is there enough demand to warrant the creation of a Fixed-wing (small) waiver category i.e., are there enough guys who want to fly those models only that we need another waiver category?

Bob
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Old 04-19-2019, 11:46 AM
  #33  
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Originally Posted by rhklenke View Post
On the other thread in the other forum, it was suggested that K-60 powered models will be over 12lbs (dry) - thus likely over 16 lbs wet, and for it to be under 12 lbs (dry), its going to be powered by a K-45 or smaller?

So it sounds like the 12 lbs dry is actually a good dividing line...

The question then, is what to do about the less than 12 lbs dry models? Is there enough demand to warrant the creation of a Fixed-wing (small) waiver category i.e., are there enough guys who want to fly those models only that we need another waiver category?

Bob
I believe there is enough interest to warrant an under 12lb class.
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Old 04-19-2019, 02:17 PM
  #34  
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I emphatically believe there is.
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Old 04-19-2019, 06:03 PM
  #35  
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I have found the smaller jets are harder to fly then a larger one.... not to mention a scale heavy EDF is harder then any turbine I have flown. Yet they won’t help with a waiver to fly the easy big turbine stuff.
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Old 04-19-2019, 08:30 PM
  #36  
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Originally Posted by rhklenke View Post
On the other thread in the other forum, it was suggested that K-60 powered models will be over 12lbs (dry) - thus likely over 16 lbs wet, and for it to be under 12 lbs (dry), its going to be powered by a K-45 or smaller?

So it sounds like the 12 lbs dry is actually a good dividing line...

The question then, is what to do about the less than 12 lbs dry models? Is there enough demand to warrant the creation of a Fixed-wing (small) waiver category i.e., are there enough guys who want to fly those models only that we need another waiver category?

Bob
i don’t think it is really if there is enough interest by those wishing to fly smaller jets only. My suspicion is that many will end up getting a bigger jet. The issue is the entry point of the smaller jets. There needs to be a way for a guy to buy p20, T35, k30, k45 as a first jet and be able to get a waiver.
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Old 04-20-2019, 06:34 AM
  #37  
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Originally Posted by why_fly_high View Post
i don’t think it is really if there is enough interest by those wishing to fly smaller jets only. My suspicion is that many will end up getting a bigger jet. The issue is the entry point of the smaller jets. There needs to be a way for a guy to buy p20, T35, k30, k45 as a first jet and be able to get a waiver.
“..... My suspicion is that many will end up getting a bigger jet......”
My take on this?
Based on the overall experience with electric ducted fan segment of the hobby, there is little, if any, interest in “advancement” from the typical 70mm, 80mm, or 90mm foamy to bigger composite models in the 120mm class. Small turbine could be the same, especially with the increasing flood of sub 60 size foamy RTF turbines coming to the market via Asia. Seems to me that there needs to be an avenue to a turbine waiver for people that will NEVER venture into models bigger than a typical large-ish foamy.

The bedrock issues here are two:
1) safe (ie: insurable) operation of a turbine
2) safe, competent, & mature operation of a model aircraft in general (this is the real Gorilla in the room)

Learning safe operation of a turbine is not that complicated.
So it boils down to this: the AMA’s insurance carrier wants one to have what amounts to a Community Based Organization “pilots license” in order to operate a turbine model (in essence what the turbine waiver has been), the waiver holder will have demonstrated at least minimal ability to safely fly a kerosene powered model.
Now......is there a real need to define the boundaries for insurance coverage of said operation when it comes to “small” jets vs more traditional size? I guess that would be up to the AMA insurance underwriters based on their expected exposure to liability based on “weight”.

”Small jet” Waiver or a Turbine Waiver with necessary endorsement for over “x” weight/size may be the way to go.

- Mike

Last edited by speed is life; 04-20-2019 at 07:14 AM.
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Old 04-20-2019, 07:08 AM
  #38  
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Perhaps now is not the best time to ask the AMA to look into this issue?

They are quite busy with “drone legislation” and the FAA to address something (current waiver requirements and process) that does not appear to be broken

Just my 2 cents
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Old 04-20-2019, 11:33 AM
  #39  
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The AMA can multi-task. This is why he's asking, the AMA has enlisted the help of the JPO, their special interest group and the subject matter experts in the area of turbine jet operations
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Old 04-20-2019, 02:59 PM
  #40  
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I'm not a "waiver holder," so I'm sure this will be immediately discounted as I couldn't possibly know anything about anything. However, from an ORM standpoint, I see four principal drivers for types (categories) of "model" jets:

Weight - full fuel
Complexity - flaps, retracts, slats, speedbrakes, spoilers, etc.
Wingloading - sink rate, flight characteristics in pattern, on final, etc.
Thrust to weight - excess thrust available, some coarse measure of performance category*

Seems logical to me that it's a matrix really, where combination of the four above drive categories. There probably won't be a ton of "non-complex" models, so maybe that's a category all to itself regardless of weight, wingloading, and thrust to weight. On the other hand, as some have pointed out, a small fast narrow CG model may be much more difficult to fly. So you'll have to account for that. Lastly, from a risk management standpoint, I'd be more concerned with total energy as a rough measure of risk, with that risk aggravated or mitigated by distance it can travel on loss of signal before engine shutdown (max velocity x no signal shut down time). The reality is you're talking about a complex process with a lot of variables, and those variables make a big difference in the handling of the jet and therefore the workload on the operator and the skill level required. The other major factor to consider is can the hobby withstand the risk of allowing folks to earn waivers with "easy to fly" jets of any size/weight/complexity and "hope" that they'll acquire the necessary skills and "headwork" ability before they try to fly something "not-easy" to fly? A wise man once told me "hope is not a plan."

I know what I would do, but that would be a slightly more "professionalized" approach. Probably more heavily based on wingloading and complexity with some consideration of the other two factors. But again, I'm not a waiver holder so I can't possible fathom what I don't know about this.

* FYI, a High thrust to low weight might not necessarily be a good thing. For example high thrust low weight plane, absent a ton of drag, might be pretty low in the RPM range on final, thus longer spool up time. That could make recovery from high sink rate difficult. Whereas a plane with lower thrust to weight might be higher in RPM range, making for faster spool up and easier recovery from low/slow or behind power curve situation. Personally, I want high thrust to weight AND the ability to put a LOT of drag on the plane. That way I'm higher in RPM range, faster spool up anyway, and also as soon as I retract the boards (for example), I'm already a bit over powered (and getting better quickly).

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Old 04-20-2019, 04:32 PM
  #41  
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Originally Posted by franklin_m View Post
Personally, I want high thrust to weight AND the ability to put a LOT of drag on the plane. That way I'm higher in RPM range, faster spool up anyway, and also as soon as I retract the boards (for example), I'm already a bit over powered (and getting better quickly).
Ditto here. I want thrust when I need it and control it with the thrust lever to keep with in safe limits. That's why I would prefer not to have arbitrary thrust to weight limits. I also have found smaller high wing loaded models much harder to fly than larger ones, whether turbine or EDF.

I like Mike's idea for some kind of "entry level small jet waiver" with an endorsement or permit for over "X" weight, similar to the LTMA1 and LTMA2 permit idea.

Gary

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Old 04-21-2019, 03:33 AM
  #42  
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Originally Posted by rhklenke View Post
I hear you, and I agree, but you also have to think in terms of a regulatory and insurance framework. If someone were to get a waiver under a system without any qualifications on the aircraft (like over 12 lbs dry), and then have problems flying their larger, heavier aircraft and ultimately have an accident of consequence, the question would immediately come to why were they given the ability to fly that aircraft without better demonstrating their ability to do so.

Yes, your example above is apropos, but I will tell you that I, personally, would not sign off on a turbine waiver on such a jet (or the commercial equivalent - a Shok jet). For me to sign off, the waiver flight has to be done on a bigger, faster jet that has retracts and flaps (i.e., a "complex" aircraft). I have signed off guys on the twin boomed trainer jets before, but I always caution them that they need to build up to the larger, heavier scale jets in some kind of step-by-step approach.

Back when I did my waiver, the "trainer jets" were the Kangaroo and Hotspot (I had a Kangaroo). Let me tell you, if you could fly and land a Kangaroo or Hotspot, you could pretty much handle anything else...

Bob
The problem you will have is that once you start issuing what are essentially type certifications (large complex, small complex, etc.), then your certification structure will have to chane as well. For example, you'll now need to build in WHO can sign off on waivers for large vs. small, complex vs. non-complex. As shown above, you aready have a problem of the "legal waiver" plane above. You WANT to say that knowing how to fly that only qualifies you on turbine operation, but the policy doesn't give you anything to stand on as a hard and fast reason to say no. In SEPCOR, I've already showed you how AMA policy has a huge loophole for LMA, and all someone has to do is print a new piece of paper each day they fly. Just like here you WANT to be able to say that you can't do that, unfortunately the policy is so poorly written that the rules don't say that you cannot.

If you want to do this right, you're talking about a much more professional looking training and certification program. One that has standard operating procedures (not just for sign offs, but for standardization of what's taught, expected during checkout flights, etc.). Then I'd counsel it should also include some way to ensure those signing off on waivers stay reasonably standardized. The worst thing for your community, during this period of enhanced attention from the FAA, would be for them to identify "Santa Claus" waiver sign dloff individuals. Your last line of defense so to speak are those granting waivers by signoff. If they're not standardized, they're accepting a lot of risk on behalf of the community/hobby w/o so much as giving you a vote. Furthermore, if you're not keeping records on who's had waivers pulled, along with info on who qualified them initially, you've given up another tool to track down standardization / quality of check out process issues.

Offer is on the table to help you add some professionalism to this if you like, from someone that's formally trained in aviation safety, designated Aviation Safety Officer (ASO), and has managed aviation safety programs (NATOPS) in two squadrons, a wing, and an air station. However, I'm sure a couple decades experience writing aviation SOPs, managing high risk aviation operations, managing aviation training and certification programs, formal aviation safety program management (NATOPS program manager), etc. will be immediately discounted because I'm not a "waiver holder" ... and thus can't possibly understand.

But the offer to help you is there none-the-less.

Last edited by franklin_m; 04-21-2019 at 03:41 AM.
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Old 04-21-2019, 12:16 PM
  #43  
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Default This ain’t rocket science

Please do not lose sight of the fact that this is a hobby and these are toy model airplanes.....
I worry that it would be too attractive to some to make things unnecessarily complex and regimented (the FAA will be bad enough) when it comes to what amounts to simply a different power source for a model airplane.

Think about it; is there any real quantifiable difference in risk to an insurer between my 19lb dry kero turbine with a Wren Supersport that might go 175mph (requires an AMA turbine waiver) and my 14s EDF Bandit that weighs 23 1/2 lbs RTF and will go 185mph easily. (No waiver required).
As well, the Bandit carries a load of LiPo’s at 14s 8000mah that would be quite a fire in a hard crash and you cannot mitigate that fire danger at impact whereas a turbine can minimize the fire danger by shutting down the engine prior to impact.

Just my 2¢ worth....modern turbine operation is not that exotic.

- Mike
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Old 04-21-2019, 12:46 PM
  #44  
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Originally Posted by rhklenke View Post
I, personally, would not sign off on a turbine waiver on such a jet (or the commercial equivalent - a Shok jet). For me to sign off, the waiver flight has to be done on a bigger, faster jet that has retracts and flaps (i.e., a "complex" aircraft). I have signed off guys on the twin boomed trainer jets before, but I always caution them that they need to build up to the larger, heavier scale jets in some kind of step-by-step approach.
Bob
I would be somewhat offended if someone refused to sign off a waiver if I were flying the sport jet / trainer that I designed myself, just because it doesn't have retracts and isn't "complex" enough. That strikes me as a rather elitist attitude. My first jet was a Boomerang Intro with fixed gear.
The shoulder wing version of mine above is 78" span, the low wing 74" span, and both weigh around 13 to 14 pounds and fly on 60 to 80 N engines. I dialled power back to 45N once and it still flew very well. They were Designed to be simple straight forward models that could operate from any club grass field, and they do just that.

I have a small EDF model with a 90mm fan which flies well (fixed gear, off grass). I'd love to do a turbine version with a Kolibri 35 but I'd fit retracts and fly it much more carefully (from hard runways).

Why not keep it simple? These new tiny turbines are rare, expensive and specialised, so why not just say you need a waiver for turbine engines 45N or more and not
for the little ones and keep your 12 lb rule?

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Old 04-21-2019, 01:08 PM
  #45  
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Originally Posted by speed is life View Post
Please do not lose sight of the fact that this is a hobby and these are toy model airplanes.....
I worry that it would be too attractive to some to make things unnecessarily complex and regimented (the FAA will be bad enough) when it comes to what amounts to simply a different power source for a model airplane.

Think about it; is there any real quantifiable difference in risk to an insurer between my 19lb dry kero turbine with a Wren Supersport that might go 175mph (requires an AMA turbine waiver) and my 14s EDF Bandit that weighs 23 1/2 lbs RTF and will go 185mph easily. (No waiver required).
As well, the Bandit carries a load of LiPo’s at 14s 8000mah that would be quite a fire in a hard crash and you cannot mitigate that fire danger at impact whereas a turbine can minimize the fire danger by shutting down the engine prior to impact.

Just my 2¢ worth....modern turbine operation is not that exotic.

- Mike
I agree to a point and disagree to some extent. First the latter.

First the latter. I think it's hard to characterize them as "toy planes" when forums have disccussions about the need for Faraday cages to protect gyros, electronic engine controls, and receivers from EMI in some applications. That tells me these are complex systems, and as was quoted in at least one mishap investigation: "Complex systems fail in complex ways." So I personally think it's a significant oversimplification to call a turbine a "toy airplane."

On the other hand, I agree that the EDF presents nearly the same risk from a KE standpoint. So in that sense, I would agree with a total energy type calculation as a basis for waivers. In your example, the EDF represents a greater energy (FYI, 23.5lbs at 185 is about the same as a F150 hitting something at about 15 mph). Not exactly a "toy plane" and that takes us full circle.

So I guess I'm not inclined to call these toy planes regardless of the mode of power.
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Old 04-21-2019, 02:17 PM
  #46  
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Default JetMach 60

Bob,

I had a lot of fun with my JetMach 60 with a RAM 500 (12 lb thrust).
Mine was 16 lb dry. Was a bit of a challenge to take off from grass in the summer.
80 inch wingspan, 1300 sq inches, 75.5 in long.
Significantly easier to fly/land than a KingCat, not as "fussy" on landing.

modelaviation.pdf

Mark
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Old 04-21-2019, 03:42 PM
  #47  
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You have to keep things in perspective here. The U.S. is one of the few countries where you need a specific "license" to fly a jet turbine model under the national model aircraft organization. In most other countries, its just a model airplane, regardless of what powers it.

Also, you need exactly ZERO demonstrated pilot proficiency to fly a UAS under Part 107.

The only question under consideration concerns turbine models under 12 lbs dry.

Bob
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Old 04-21-2019, 04:26 PM
  #48  
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Originally Posted by rhklenke View Post
You have to keep things in perspective here. The U.S. is one of the few countries where you need a specific "license" to fly a jet turbine model under the national model aircraft organization. In most other countries, its just a model airplane, regardless of what powers it.

Also, you need exactly ZERO demonstrated pilot proficiency to fly a UAS under Part 107.

The only question under consideration concerns turbine models under 12 lbs dry.

Bob
Response noted ... as predicted ... message comes through loud and clear that non-waiver holders can't possibly understand.
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Old 04-21-2019, 05:46 PM
  #49  
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I'm also not a turbine waiver holder but, like Franklin, I do know aviation. That said, I'm going to throw out another option that no one has really mentioned.
Back in post 43, speed is life said "Think about it; is there any real quantifiable difference in risk to an insurer between my 19lb dry kero turbine with a Wren Supersport that might go 175mph (requires an AMA turbine waiver) and my 14s EDF Bandit that weighs 23 1/2 lbs RTF and will go 185mph easily. (No waiver required).
As well, the Bandit carries a load of LiPo’s at 14s 8000mah that would be quite a fire in a hard crash and you cannot mitigate that fire danger at impact whereas a turbine can minimize the fire danger by shutting down the engine prior to impact."
Using that statement, I think a turbine waiver is totally outdated as well. With the FAA more or less taking control of model aviation, maybe the modelers should be pro-active on updating the waiver process. Let me give you a more realistic waiver policy. A waiver would be required if the plane:
1) exceeds a specific wing loading
2) exceeds a specific thrust to weight ratio
3) exceeds a specific top speed
Notice, I didn't include engine type in this as some EDF jets are just as fast as turbines.
I picked these three requirements due to the "danger" each can pose. My reasons are:
1) High wing loading can stress the main spar so much that a wing can fail with minimal "G" loads added. It won't take many flights with added "Gs" to break a wing if the pilot flies the plane "aggressively"
2) I think the thrust to weight is self explanatory. If not, think like this; a plane can accelerate straight up at less than half throttle, how fast will it be going if the radio fails at full throttle when it hits something/someone. This goes back to Franklin's comparing a plane to an F-150 during an impact in post 45
3) This one should be a given to all
Obviously, most sport and trainer types won't require a waiver since they won't exceed reasonable figures plugged in to the limits I listed above. Most prop scale types won't either. This would and should only impact the high performance prop planes and jets(EDF, DF and turbines) since they are the ones that will be the most dangerous
Then again, what do I know? I'm just someone that has worked in full scale aviation most of my life and has to deal with FAA mandated documents every day at work

Last edited by Hydro Junkie; 04-21-2019 at 10:03 PM.
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Old 04-21-2019, 06:19 PM
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Originally Posted by rhklenke View Post
You have to keep things in perspective here. The U.S. is one of the few countries where you need a specific "license" to fly a jet turbine model under the national model aircraft organization. In most other countries, its just a model airplane, regardless of what powers it.
Maybe it's time that changed...

Originally Posted by rhklenke View Post
Also, you need exactly ZERO demonstrated pilot proficiency to fly a UAS under Part 107.
"People in glass houses shouldn't throw stones..." I seem to remember a discussion about complaince problems in JPO, where someone said "Not driving away members" was a consideration... Recommend you fix compliance problems among waiver holders before you point fingers at 107 operators.
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