Turbine Thrust limits in the US
09-08-2015 | 12:57 PM
#1
Turbine Thrust limits in the US
Guys,
Responses to the JPO survey are coming in (thanks all!), but they do seem to indicate some confusion on the turbine thrust limit changes that the JPO has just worked out with the AMA.
Previously, the thrust limit for any 55 lb (or under) single-engine turbine-powered aircraft was 45 lbs (of thrust) AND it was specified to be "Manufacturer's rated thrust."
With that rule, NONE of the 200-class turbines, such as the Kingtech K-210 (manufacturer rated at 46.3 lbs @max RPM), Jetcat P200 (manufacturer rated at 52 lbs @ 112,000 RPM), Jet Central Mammoth SP (manufacturer rated at 50.5 lbs @ max RPM), Olympus HP (manufacturer rated at 51.7 lbs thrust) are legal without being derater by the owner (that's you...)
The NEW thrust limit is 50 lbs (of thrust) and its "installed static thrust". Thus, if you are running any of the engines above in a piped installation at anything over standard temperature and pressure, your thrust will be down at least a couple of pounds over the manufacturer's rating (if you believe them) and you are "legal" with respect to the rule.
As I said in the email from the AMA, it seems like a small change, but its important to try and keep the community in compliance with the rules and keep the rules updated to what is going on in the community.
To those guys who wanted higher thrust and speed limits, unfortunately, that is not something that is going to receive a lot of support at this time - not outside of the LTMA program anyway. However, we will continue to listen to all requests and try and gather supporting information to help make them happen.
Bob Klenke
JPO President
Responses to the JPO survey are coming in (thanks all!), but they do seem to indicate some confusion on the turbine thrust limit changes that the JPO has just worked out with the AMA.
Previously, the thrust limit for any 55 lb (or under) single-engine turbine-powered aircraft was 45 lbs (of thrust) AND it was specified to be "Manufacturer's rated thrust."
With that rule, NONE of the 200-class turbines, such as the Kingtech K-210 (manufacturer rated at 46.3 lbs @max RPM), Jetcat P200 (manufacturer rated at 52 lbs @ 112,000 RPM), Jet Central Mammoth SP (manufacturer rated at 50.5 lbs @ max RPM), Olympus HP (manufacturer rated at 51.7 lbs thrust) are legal without being derater by the owner (that's you...)
The NEW thrust limit is 50 lbs (of thrust) and its "installed static thrust". Thus, if you are running any of the engines above in a piped installation at anything over standard temperature and pressure, your thrust will be down at least a couple of pounds over the manufacturer's rating (if you believe them) and you are "legal" with respect to the rule.
As I said in the email from the AMA, it seems like a small change, but its important to try and keep the community in compliance with the rules and keep the rules updated to what is going on in the community.
To those guys who wanted higher thrust and speed limits, unfortunately, that is not something that is going to receive a lot of support at this time - not outside of the LTMA program anyway. However, we will continue to listen to all requests and try and gather supporting information to help make them happen.
Bob Klenke
JPO President
09-08-2015 | 03:25 PM
#3
There were lots of guys out there flying these 200-class engines and I'm sure nobody realized that they were over the 45 lb thrust limit. It didn't seem reasonable to try and get everyone to turn their engines down, and it didn't seem necessary to do so for the sake of safety either (a 55 lb airplane is more likely safer with 50 lbs of thrust than with 45 lbs of thrust - its definitely more reliable), so we initiated the change.
If you are in the LTMA program, you will notice that there is a corresponding change in the thrust limits there from a blanket 75 lbs (LTMA-1) and 90 lbs (LTMA-2) to aircraft wet weight + 5 lbs or 75 lbs (or 90 lbs), whichever was less. That was done to make those thrust limits more reasonable, because a 56 lb aircraft with a 75 lbs thrust engine isn't a good idea...
Bob
09-09-2015 | 05:55 AM
#6
Keeping up with these types of issues is one of the primary responsibilities of the JPO, in my opinion (and it the opinion of the majority who have answered the survey), and is one of the reasons that the JPO needs to continue to exist, even if only about 300 of the 1800+ turbine waiver holders are members. I sure wish it was more, and I'm working to add additional value to JPO membership, but in my opinion, having a strong jet community voice inside the AMA alone is worth $25 a year...
Bob
09-09-2015 | 05:58 AM
#7
There used to be a rule that prohibited a thrust-to-weight ratio over 1:1, but it was virtually unenforceable and very difficult for AMA members to comply with, so it was removed.
The 200 MPH max speed limit is the main limitation to small airplanes with big engines.
Bob
09-09-2015 | 06:19 AM
#8
The JPO initiated it and managed it through the approval process.
There were lots of guys out there flying these 200-class engines and I'm sure nobody realized that they were over the 45 lb thrust limit. It didn't seem reasonable to try and get everyone to turn their engines down, and it didn't seem necessary to do so for the sake of safety either (a 55 lb airplane is more likely safer with 50 lbs of thrust than with 45 lbs of thrust - its definitely more reliable), so we initiated the change.
If you are in the LTMA program, you will notice that there is a corresponding change in the thrust limits there from a blanket 75 lbs (LTMA-1) and 90 lbs (LTMA-2) to aircraft wet weight + 5 lbs or 75 lbs (or 90 lbs), whichever was less. That was done to make those thrust limits more reasonable, because a 56 lb aircraft with a 75 lbs thrust engine isn't a good idea...
Bob
There were lots of guys out there flying these 200-class engines and I'm sure nobody realized that they were over the 45 lb thrust limit. It didn't seem reasonable to try and get everyone to turn their engines down, and it didn't seem necessary to do so for the sake of safety either (a 55 lb airplane is more likely safer with 50 lbs of thrust than with 45 lbs of thrust - its definitely more reliable), so we initiated the change.
If you are in the LTMA program, you will notice that there is a corresponding change in the thrust limits there from a blanket 75 lbs (LTMA-1) and 90 lbs (LTMA-2) to aircraft wet weight + 5 lbs or 75 lbs (or 90 lbs), whichever was less. That was done to make those thrust limits more reasonable, because a 56 lb aircraft with a 75 lbs thrust engine isn't a good idea...
Bob
09-09-2015 | 06:40 AM
#10
Mike
The Jet Pilots Organiation (JPO)
Is our voice with the AMA . As Bob mentioned we are a very small percentage of the AMA and easy to get "lost in the shuffle". It is important to me that our voice in the parent organization is recognized and the best way , in my opinion, is through the JPO.
Even 300 are louder than 1.
With an estimated 1800 - 2000 waiver holders it is a shame that we have only 300 members
Just my two cents worth
Glenn Sheppard
The Jet Pilots Organiation (JPO)
Is our voice with the AMA . As Bob mentioned we are a very small percentage of the AMA and easy to get "lost in the shuffle". It is important to me that our voice in the parent organization is recognized and the best way , in my opinion, is through the JPO.
Even 300 are louder than 1.
With an estimated 1800 - 2000 waiver holders it is a shame that we have only 300 members
Just my two cents worth
Glenn Sheppard
09-09-2015 | 07:09 AM
#11
Has the JPO read thre new rules just released by the fAA? You guys seem to want ridiculous size jets - what do you think of the 55 lb limit for hobby aircraft with bigger ones requiring special exemptions and certifications?
09-09-2015 | 08:15 AM
#13
My Feedback: (11)
09-09-2015 | 08:34 AM
#15
My Feedback: (1)
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From: Fort Wayne, IN
09-09-2015 | 10:07 AM
#17
My Feedback: (16)
I've got a SM A-10 and it needs the LTMA-1 permit. I don't believe that the SM A-10 can be built without going over the wet weight limit. The LTMA-1 process is thorough and it's always good to have another set of eyes go over your installation.
09-09-2015 | 10:20 AM
#19
My Feedback: (16)
The PDF gives you all of the info. You'll need an inspector for the airframe inspection and CDs may do the flight observation. http://www.modelaircraft.org/files/520-a.pdf
Really not an issue at all.
Really not an issue at all.
09-09-2015 | 12:14 PM
#20
Under the "normal" AMA rules, a jet with a maximum wet weight of 55 lbs can have a maximum of 50 lbs of thrust. That's for *all* installed engines, either one or two.
Previously, the single engine thrust limit for jets with a wet weight of 55 lbs or under was 45 lbs, and for twins it was 50 lbs. Thus, as I mentioned before, these 55 lbs (or less) planes with Jet P200's, Kingtech K-210's, Jet Central Mammoths, etc. were not in compliance with the rules. Now they are...
The rules for turbine jets 55 lbs and under (wet weight) are here: http://www.modelaircraft.org/files/510-a.pdf
and for the LTMA program are here: http://www.modelaircraft.org/files/520-a.pdf
Bob
ps. the 55 lb limit is in the AMA's National Model Aircraft Safety Code, to wit:
2. Model aircraft pilots will:
...
(e) Not exceed a takeoff weight, including fuel, of 55 pounds unless in compliance with the AMA Large Model Airplane program. (AMA Document 520-A.)
...
Last edited by rhklenke; 09-09-2015 at 12:17 PM.
09-09-2015 | 12:58 PM
#21
There IS a normal 55 lb weight limit for jets and there IS a special certification program for jets from 56 lbs to a maximum of 100 lbs. See the document I cited in my email above.
Bob
