The 55 pound rule
more discussion

6 May 2003

The rule has been on the books for several years (click here to view the rules/restrictions). For some reason, the details (rule #4) have not been common knowledge to some modelers.

It is interesting that in the reference to take-off weight the words "with fuel" have been deleted in the 2003 printing of the safety code. Officials at the AMA are however, interpreting take-off weight as "including fuel".
All scale entries at the AMA Nationals are weighed during processing, but with no fuel on board and they are not weighed again during the flying portion of the contest, so even the AMA has not been watching this closely.
Many models have been built and some even kitted and sold that are definitely outside of the rules.
In a recent conversation with our AMA president, Dave Brown shared with me his concerns about such models being involved in an accident, especially at an AMA sanctioned event. No C.D. or other AMA official would want to be associated with the outcome.
This recent awareness of the 55 pound rule and the potential consequences of violating it will undoubtedly lead to event directors weighing some models that are obviously close to the limit.

Lobby for 55 dry

Since the current rules (and interpretation there of) are biased against jets because of the disparity in fuel consumption, it would be a reasonable request to leave the number 55 intact but define it as a dry weight. This would even give the prop drivers another pound or two to work with.
I have been informed that there is not much appetite within the AMA for changing the number. There just may be a willingness to even things up between props and jets as long as certain safety issues are addressed.
There is concern amongst some about the amount of fuel that jets carry. It is not our intent to carry excess fuel, only enough to comfortably complete a flight at a jet event or contest. Some may want to put a finite number on that and that would be ok for jet modelers if it were not ridiculously restrictive. Personally, I would want at least 10 minutes of fuel on board for a safe operation. That is equivalent to an 8 minute flight with a safe go-around, or, about 1.75 U.S. gallons for a single 35lb thrust engine or (2) 25lb thrusters.
The difference in the fire intensity resulting from a crash involving one gallon or 2 gallons of fuel is insignificant. Experience has taught us that the water (from hand operated 5 gallon extinguishers) is best used on the downwind periphery of the fire, allowing the fuel spill to simply burn itself out. A prop model that crashes with 1 quart of gasoline on board can be just as hazardous.
The absolute best way to reduce the fire hazard that jets pose is to educate and flight test the pilots so that there are fewer mishaps. This subject is currently being addressed by a committee of JPO and AMA officials.

Example Aircraft

Tommy Woods has twice competed in Top Gun with a Yellow A/C F-18 powered by (2) RAM 1000 engines.
This is a highly modified kit but still has balsa covered foam wings and tails - about as light as they can be built. This 1/7th scale rendition weighs 45lbs dry and carries 10lbs of fuel - barely enough for a comfortable competition flight.
So what is wrong?
The model is so close to the edge that Tommy cannot add pylons and ordinance to the wings or more details to the landing gear - things that make scale fighters attractive to both the judges and other scale model enthusiasts. No one can argue that this model is too big or that this size doesn't look great in the air. And, if you know Tommy, you know that there is no extra glue, paint or other unnecessary components in the model.
Terry Nitsch's Rafale B-O1 with external tanks and (2) Mercury engines weighed 42lbs dry. Add the fuel and it was also very close to the limits.
Amending the rule as proposed would allow us to build slightly larger models (10% or less) that had sufficient internal structures to make them better withstand the speed and G-forces associated with realistic jet flight. Mass balancing of control surfaces such as large stabilators (another safety issue) could also be accomplished without fear of going a half a pound over the current limit.
Prop drivers are flying larger models that are easier to see, wouldn't it be fair for jet pilots to enjoy the same benefit?

Contact your V.P.'s
see Model Aviation for address's

Jet pilots should contact your AMA District V.P.'s and their assistants and your JPO reps if you want a change. Please don't depend on the other guys to get something done.
You might also directly correspond to members of the AMA Safety Committee chaired by Don Lowe.
A list of email addresses for members of the AMA Safety Committee will be published soon.

Bob Violett

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