There are some changes that will be announced by the AMA with regards to experimental regs this coming week. While I won't go into all the detailed changes as many were simple updates or clarifications, there are a few that are significant for turbine pilots:

1) While there was no overall increase in weight for either Props (100) or turbines (75), the dry weight limitation was removed for turbines. Previously, the regs read a turbine aircraft could not weigh more than 55 dry, 75 fueled. Now it simply reads 75 fueled. This will make it a bit easier for those building the MIBO A10's or CARF Mig29's that were marginal at 55 dry. They should comfortably fit under 75 fueled.
2) Thrust limitation for turbines is simply 1:1 fueled. The prior limitation was 45 pounds for a single, 50 for a twin (combined). This should provide an added safety margin and better all around performance.
3) If you are building an aircraft from a kit, the extensive calculations to determine proper servo torque are no longer required. You must simply meet or exceed the manufacturers specs, without altering or modifying the design. Scratchbuilt models must still provide the torque calculations.

So, for example, if you are working on a MIBO A10 that will be 60 pounds dry and want to power it with a pair of Super Eagles, you are now going to be legal with room for a little more than a gallon of fuel a side.

For those oversees who would like to bring large aircraft to the states, you may now obtain an "event permit" as long as the aircraft has three successful flights. An inspection is still required and you must be an affiliate AMA member. All other limitations and requirements apply. For Canadians, if you have something between 77.3 and 100 pounds where MAAC coverage doesn't apply, the event waiver will work for you as well.

While there were some items we asked for that we couldn't address at this time for various reasons, these are very positive steps forward. The JPO did play a part in moving these changes through the system. Dave Matthewson and Bob Underwood also supported these updates.

There will be a more in-depth look at experimental regs once the FAA subcommittee on light UAVs renders its recommendations, and I would encourage anyone who has additional suggested changes to send me a PM. An increase in weight limit to 100 pounds is already on the list, so there is no need to go on record with this proposal.

I am writing a summary of all the changes for distribution to inspectors, and will post this as soon as it is available.

Keith,

Thanks for the heads up and the information! I hope you're doing well.

Have a Happy New Year!

Chad

Keith,

This is very good news! I have gone on record several times with previous JPO administrations that a 75 lb weight with a 45lb (or 50lb - twin) thrust limit didn't make any sense. Unfortunately, they just didn't seem to either get it, or listen. I thank you and the other folks in the JPO and AMA that made this happen. I hope that this will foster more efforts into "heavy" jets, and let guys who want to power these big models like the 1/7 F-18's and F-15's with 1:1 thrust-to-weight, do so without "bending" the rules.

For those guys in JPO District 4, I am a designated experimental aircraft inspector (Virginia), as is Andy Kane (Maryland). Between the two of us, we can easily get your aircraft inspected - especially if its a manufacturer's kit, so you can go with that P-200 turned up to the full 50+ lbs of thrust... For those of you in other districts, the process of becoming a designated inspector is mostly a paperwork exercise and most of you that I know have the qualifications to perform that role, so go out and get designated for the jet guys in your area! It seems to me that if we demonstrate that there are a lot of new models coming out that fit into this category, *and* demonstrate that they can be operated safely, we have a better chance of getting the "normal" weight limit increased - JMHO...

I also hope that all of you guys will reconsider your membership in the JPO - especially those who left under the previous administration. It appears that the JPO is back to being what the jet modelers need the most - an advocacy group run by actual jet modelers...

Thanks Keith!

Bob

So according to rule #2 I can no longer put a 37lb or 43lb thrust turbine in say a 28lb Eurosport or boomerang??? And are we going to go by manufacturer rated thrust or actual thrust produced by the aircraft since in situations where a bifurcated pipe is installed the aircraft actually looses thrust??

1:1 has been a rule...a while ago

Corrected mis-information...

Uh, no it hasn't......

Hmmm, I couldn't find it either. I must be ahead of my time...

The experimental regs only impact aircraft that weigh more that 55 pounds. So it would be within the rules to put a P180 into a Eurosport. This change is not dramatic, but will allow the legal use of 50 pound turbines in some larger airframes, and in some cases allow builders of twins to install the next larger class size engine in their aircraft.

There is no published rule relative to thrust loss for bifurcated pipes, so it would be up to the inspector. If you were within a pound or two and had a bifurcated pipe, I think most inspectors would be OK with it as long as everything else was up to snuff. Bob may want to comment on this.

Thanks to all of you for the support and kind words. As more and more large kits become available, and assuming the economy recovers at some point, these changes will become more relevant for a larger number of us.

I am reaching back, but I believe in early times, there was a 1 to 1 thrust to weight ratio rule applied to all turbine aircraft under 55 pounds that was eventually replaced by the 200 mph rule. I'm sure someone here will remember. This was just prior to the effort to put speed limiters on all turbine aircraft that fortunately never made it past the EC.

You're not that old yet Keith! Your memory is accurate. As I recall Over 1:1 used to be against the AMA regs, it was dropped as part of the same program that gave us the ability to buddy chord turbines, and stop having to go to ground school and take written tests to get our waivers (man did that suck, I had to fix my answers two times to pass that stupid test!)

I would agree that accounting for 2 or 3 lbs of thrust loss for a bifurcated pipe would be reasonable. It does bring up a good point though, and that is, we (at least in the US) don't have a lot of experience in what the correct pipe sizes should be for an engine with more than 45 lbs of thrust - maybe we can get Tam and/or Bob Wilcox to take a look at this (or maybe they already know).

BTW, I know that the P-200 is currently de-rated to 45 lbs for sale in the US. Anybody know what the normal thrust is, or can be?

Bob

I had one on a test stand one day blowing 56 lbs of thrust at 650 or 700 degrees C, I do not recall the RPM as I was more interested in Temperature at the time. I do remember that I ran it out of fuel because when it blew out, I was not paying attention to fuel flow and in addition to crapping my pants, I thought I had blown myself up

I think the rated thrust of the unrestricted P200 is ~53 lbs.

This might be a good example of the technical data that the JPO hopes to pull together in the next few years for our web site .... a pipe expert's design criteria that we could all use to make sure we sizing pipes correctly. You could even extend the thought to intake area as well.

As I remember the original rule stated "....thrust cannot exceed .9 to 1" before the 200mph limit was made.

I for one am glad to hear the rule changes. My personal thanks to Keith and all those who have worked on these changes. It allows for more creativity in the larger model arena.

My scratch built B-1B project is running about 48 lbs dry with two 20 lb thrust turbines. With all the fuel that will be needed it would have weighed over 55 lbs wet and would then fall into the Experimental category, even with the designed .6 to 1 thrust. Now I feel much more comfortable with the new weight limits and not have to back off on a safe fuel load to get it under the old limits. At least I have built it under the Experimental rules so it has a lot of redundancy and falls within their specs for calculating servo loads. This is going to be a good year.

Roy

ROTFLMAO !!!

Under the older rules, you actually had a choice : (a) .9 to 1 thrust to weight, OR (b) 200 mph. In other words, if you kept to .9 to 1 then it was OK to bust 200 mph, but if you exceeded .9 to 1 you had to keep the speed down to 200 mph max.

Gordon

Gordon has it right.

Actually Gordon and Molar Mender are both right.

The first set of turbine rules adopted by the AMA in 1997 or 1998 limited the thrust to weight ratio to between .5-1 and .9-1.
(The interceptor I was flying at the time weighed about 20lbs at takeoff, and was flying on a 8-1/2 lb thrust FD3-67)
I don't think there was a speed limit.

The speed limit was introduced in the next drafting of the rules as an appeasement for loosening the thrust to weight restrictions.

The rule was actually .9 To 1 weight to thrust and that was 5 or 6 years ago.

Joe L.

Keith,
Thanks to you and JPO for the effort and success in improving and broadening the experimental class for our jets. Getting rid of the 55lb dry and the thrust limit will benefit my current projects, SUPER!!! See you at FJ 2009.
Jorge

Ok, I did some research just out of curiosity and here's what I found:

1) The original rule was a range of .5 to .9 TTW ratio. This regulation was passed in 1997 and remained in effect until 4/1/2000.
2) Effective 4/1/2000, the rule was changed to .9 TTW ratio or speed not to exceed 200 mph.
3) Effective 3/1/2004, the TTW reference was dropped altogether.

Thanks to Ilona Maine, who had all the data.

All this effort...just so Jorge can fly 'legally' !

Ray

Jorge still flies? I thought he was just driving up and down the East Coast these days... LOL

Adil

There are prop planes out there that do 200 or better why are turbines limited to 200