Sound & Model Aeronautics
Howard Crispin, Jr.
We all get wrapped up in problem situations where the important questions seem to be lost somewhere in the process. This is true in many situations concerning noise generated by our aircraft and the effects on neighbors. Taking sound-level readings following recommended procedures does not, by itself, answer the question of complaints. You must recognize that the complainant is not located at a distance of nine feet from the aircraft (three meters for FAI measurements). One must understand the effects of distance on generated sounds and the actual environment of the complainant. There is also the matter of public relations, which in many cases is nonexistent.
Public relations is the easiest place to start and takes relatively little effort. The attitude that you are at the site through some divine right—or because of a signature on a lease—does not excuse you from inflicting disturbances upon your neighbor. This is even more true if the neighbor has no interest in your activity or any activity outside his/her own property.
I have tried to convey that sounds generated by your aircraft are heard and evaluated against the background (ambient) sound level at the neighbor’s location. You can use a good sound-level meter and take actual measurements, or you can make reasonably good estimates with simple math (a hand-held calculator helps). You should still take readings, according to established procedures, of the sound level of your aircraft.
If an aircraft is properly set up, engine speed should not greatly vary between high rpm on the ground and full throttle in the air. Propeller loading is different between run-up and inflight conditions, but the rpm difference will not appreciably increase the sound level in flight. Flight characteristics will probably also reduce levels, keeping ground measurements reasonably valid for inflight conditions.
You need to estimate the slant-range distance from your aircraft in flight to the complainant’s property. Most fliers do not appreciate the distance between model aircraft and the pilot, which makes other estimates difficult. Some useful reference figures:
- FAI rules for RC Aerobatics relate to a distance of 150 meters to the "box" (the distance out front of the flier), roughly 490 feet.
- If you stand at that mark and increase altitude until your line of sight is 45° up from horizontal, the altitude is about 490 feet and the slant range is about 690 feet. This gives a visual reference for distance and the effect on sound.
Sound levels decrease by about 6 dB with each doubling of distance. For example, if sound is 100 dBA at 9 feet, it will be approximately:
- 94 dBA at 18 feet
- 88 dBA at 36 feet
- 82 dBA at 72 feet
- 76 dBA at 144 feet
- 70 dBA at 288 feet
- 64 dBA at 576 feet
- 58 dBA at 1,152 feet
Ambient sound at a neighbor’s location is likely in the 35–45 dBA range. When the difference between the aircraft sound and ambient is 6–10 dB, the aircraft sound is a significant factor.
Use this formula for any distance calculation: Sound level at X distance = sound level at measured distance − 20 × log10(distance_X / distance_measured)
Example: measured 100 dBA at 9 feet; to find the level at 690 feet:
- ratio = 690 / 9 = 76.666...
- 20 × log10(76.666) ≈ 37.7 dB
- 100 − 37.7 ≈ 62.3 dBA at 690 feet
This assumes open path and relatively static atmospheric conditions. Next month I will include drawings depicting procedures when applying this to real situations.
Mouse Cans
No articles have appeared recently in Model Aviation about using mouse (and similar) cans for add-on mufflers. This was a legal decision by the Academy’s attorney (safety considerations). Articles have appeared elsewhere describing methods, but attempts to find a source for new, empty cans were unsuccessful; few suppliers replied. Retail packaging is increasingly plastic rather than aluminum. A likely alternative is thin-wall aluminum tubing of various diameters; assembly procedures are similar, but you will need to find suitable end fittings for the tubing.
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Executive Director's View from HQ
Jerry Rouillard AMA Executive Director 5151 E. Memorial Dr. Muncie, IN 47302
How do we provide you a better magazine?
The member survey results (reported in the March issue) showed Model Aviation to be the thing members most liked and the thing they most disliked—nearly equal measures. Association publications often have ambivalent readerships. For some the magazine is the most prized benefit; for others it is little more than monthly clutter. The challenge is pleasing a membership with widely diverse interests, ages, and experience levels.
The magazine is essential to AMA: to advocate causes, state official positions, provide a forum for debate, and serve an educational role through technical how-to articles and event reporting. It needs to be attractive, filled with relevant information, and enjoyable to read.
We cannot please everyone, but we can learn readers’ preferences and do our best to satisfy them. Ways to give feedback:
- Model Aviation Suggestion Box: a 24-hour voicemail at (317) 287-1256, ext. 223. Leave a message; if you want a response, leave your name and number.
- A directed readership survey: a Model Aviation readership survey is scheduled to appear in the July 1995 issue. It will ask focused questions to help us publish a magazine that meets members’ needs.
Your participation is essential. Without a strong readership response, the survey will be ineffective and publishing policies will continue to be influenced by complaints rather than preferences. Completing the survey is a personal investment in Model Aviation.
Correction: The February "Executive Director's View from HQ" contained an error regarding an Executive Council motion on additional insurance for sanctioned racing events with models over 20 pounds. The approved motion was for underlying $1 million primary coverage only for sanction sponsors, additional insureds, and AMA.
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AMA News
Executive Council Meetings
- April 21–22 — Visalia, CA
- July 29–30 — Oshkosh, WI
Nats (National Championships)
The Academy’s founding premise stressed competition to promote the health and growth of model aviation. Competition has driven technological advancement and interest, even though only a small percentage of members participate in formal competition. Other sports show similar competitor/noncompetitor ratios; everyone benefits from improvements driven by competition.
Over the years AMA has conducted a large multievent Nats. Events have increased with new technologies and aeromodeling forms; in recent years the Nats included over 90 official and unofficial events, with 700–1,600 participants. Organizing and executing the Nats has become increasingly difficult: management is a mix of paid AMA headquarters employees and volunteers, expenses for volunteers have increased, costs have exceeded income, and Headquarters staff absence creates a burden.
We oppose eliminating the Nats. It is important to the hobby’s visibility and provides fun and stimulation. Recent national media coverage (Discovery Channel, ESPN coverage of T‑6 Races) helps public acceptance, which in turn helps protect local flying sites.
To make the Nats cost-effective and sustainable, we are exploring:
- Holding the event at Muncie once necessary facilities are in place.
- Greater use of volunteers to ease Headquarters’ burden.
- Trimming events to a manageable number and eliminating poorly attended events (using entry cutoff dates).
- Other management improvements.
This year we had to split events because not all facilities were available at one site; some events were moved to Tri‑Cities, Washington, and others to known facilities or piggybacked on other major events at Muncie. We hope to reassemble most Nats events at Muncie next year. We do not wish to end the Nats; we are working to provide a quality event at a reasonable cost.
I will return as author of this column for the May issue with a report on major happenings at the April Executive Council meeting. The June issue will feature a collaboration between two District AVPs.
Until then, the runway is clear!
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Inside View
Headquarters often encounters situations where important questions are lost in the process. One recurring issue is noise generated by aircraft and its effects on neighbors. Taking sound-level readings following recommended procedures is necessary but not sufficient. Recognize the complainant’s location relative to the aircraft and the influence of distance and the complainant’s environment. Public relations and considerate site management are key—no signature on a lease gives license to ignore neighbors. Use sound-level meters and simple calculations to estimate and explain what a neighbor hears; follow established measurement procedures.
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DISTRICT IV REPORT
Delaware / District of Columbia / Maryland / North Carolina / Virginia
Howard Crispin Vice President 611 Beechwood Drive Charlottesville, VA 22901
Associate Vice Presidents:
- Robert E. Babura, 117 Otis Drive, Severn, MD 21144-1130 — Phone: (410) 969-9356
- Bob Champion, 205 Tipton Road, Newport News, VA 23606-3663
- Chuck Foreman, 5811 Rinker Drive, Mechanicsville, VA 23111
- Doug Holland, 3517 Fernwood Drive, Raleigh, NC 27612-6215
- Scotty Meyer, 11 Orchard Lane, Wilmington, DE 19809-1719
- Richard (Dick) Smith, 761 Gwynne Avenue, Waynesboro, VA 22980-3346
- Charles Spear, 106 Crestview Drive, Mocksville, NC 27028-2646
Frequency Coordinator:
- Paul Yacobucci, 6408 Winthrop Drive, Fayetteville, NC 28311-1007 — Evening: (919) 488-5936
Nineteen Hundred and Ninety-Four
1994 ended on a fine note. The Hardy Souls Soaring Contest at Nike Park (the last Saturday of the year) was held under good weather despite forecasts of cold, wind, and rain. Contest Director Luther Mitchell set a 1500 hours cutoff for official flying. Competitors could fly as many times as desired; the top three flights (with landings) counted, allowing most to fly six or more times. The day stayed pleasant until shortly after 1500, when rain began. The event is run by the Tidewater Model Soaring Society.
New Flying Site
The Greensboro Radio Aeromodelers (AMA Club #421) secured a long-term lease after years without a permanent home. The new site features a 400 × 60-foot runway, field shelter, and snack bar. The dedication was during the 14th Annual GRAMS Giant Scale Fun-Fly on 29 October. A new site revitalizes club membership—local effort is essential. The Academy can provide assistance; contact your District Vice President or Headquarters when needed.
Winter Events
Winter flying is sporadic. December 1994 was unusual with no snow in much of the District. January started cold. NVRC has an annual Snow Fly in the month; there are swap shops and other events in the next two months. Notable events:
- Swap Shop at Graham, NC (long-running)
- Newer event in Hampton, VA on 11 February
- 17th Annual Swap Shop/Auction/Static Competition on 18 March by the Roanoke Valley Radio Control Club at Lord Botetourt High School (Exit 150B off I-81)
Sanctions
Contest Coordinator Steve Moulton reports many groups have submitted early sanction applications. If the trend continues we should see equal or more events than in 1994. Support your club and the sport.
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DISTRICT V REPORT
Jim McNeill, Vice President 617 South 20 Avenue, Birmingham, AL 35205 — (205) 322-2127
Important news: Our District V Frequency Coordinator passed away recently. His wife, Dorothy, has asked to take his place and has been appointed. She has handled the paperwork for years, is familiar with the job, and wishes to remain involved. An AMA endorsement form has been mailed to her to become a Leader member.
Notable items:
- Bill Haywood (Foley, AL) is becoming an AMA Leader Member.
- The IMAA Lower Alabama Fall Fly-In at Battleship Park in Mobile had many Big Bird enthusiasts despite uncertain weather.
- Ed Lidgard (Central Georgia), an FF Hall of Famer, helped start an RC club in Perry, GA, by directly petitioning the mayor. The town provided and improved a field; the club now has 34 members. Ed’s story illustrates what determined people can accomplish.
- Joe Mead (Jacksonville, FL) will CD a "Burnie Fields Memorial Fly-In" on April 1–2 at Lannie Road Model Airplane Park; proceeds will go to Dorothy Fields.
- Hester and Maxie Hester (SIG Mfg. Co.) traveled from Iowa to Florida to attend Burnie’s funeral.
- Dr. John Agnew (Fort Myers, FL) commented positively on the LFS Nats at Muncie and the AMA museum; he urged improvement of Muncie facilities.
- Jim Bissell (St. Louis / Orange Beach, AL) thanked organizers for a recent Fly-In and noted TV coverage on the Mobile Press Register.
Several well-run fly-ins have been reported, including the 5th Fall Flying Fly-In at Crestview, FL.
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DISTRICT VI REPORT
A new VP and a refreshed list of Associate Vice Presidents head up District VI. Thanks to all who voted and to Jim Sears for his years of service—he remains active as AVP for Kentucky.
Send photos and information to get your club in print (typed or clearly printed material preferred).
Local highlights:
- Terre Haute, IN: Young twins Jacob and Daniel Sedlacek (about 5) enjoy flying RC with help from their dad, John (Terre Haute R/C Club).
- St. Peters, MO: George E. Appel ran an enrichment program at Francis Howell School teaching five boys (ages 11–13) to build and fly rubber-powered models using plans from Air Trails (May 1949).
- Angola, IN: George Sorg and his Eagle at the Steuben Model Aircraft Klub (SMAK) field; Fred Bright and others in the pit area.
- Chicago, IL: "WOLVE" the blimp entertains Chicago Wolves hockey fans before games. Main pilot Scott Justice, backups Elmer Helfert and Deb Justice. Great PR—contact the team (they are AVPs) for details.
- Orland Park, IL: The Palos R/C Flying Club gave a talk and demonstration to Cub Scout Pack 62, following great Chicago Tribune coverage of their air show. The club has 197 members.
Vintage R/C Society: dedicated to preserving radio control history. Contact Bill Poythress, Secretary, 2 Hemlock Ct., Saugerties, NY 12477.
District facts and figures:
- District VI has 9.96% of AMA membership and is the third largest district (behind Districts V and X).
- There are 276 clubs in District VI (latest information from Headquarters).
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DISTRICT VII REPORT
Iowa / Michigan / Minnesota / Wisconsin
Peter Waters, Vice President
Good news: many clubs with flying-field problems are hopeful, with help from local officials. More participation in local activities helps when negotiating fields. Officers have been contacted to confirm willingness to continue or pass the baton; expect some new faces at meetings.
Gold Leader Club Awards (clubs awarded a banner from the district):
- Pebble Creek Flyers Inc., Wisconsin
- Milwaukee Scimitar Squadron, Wisconsin
- Calumet Flyers Inc., Wisconsin
- Circlemasters Flying Club, Wisconsin
- RUF Model Airplane Club, Wisconsin
- Thunderbird R/C Club, Michigan
- Midwest R/C Society, Michigan
- Port Huron R/C Treetoppers, Michigan
- River District R/C Eagles, Michigan
- Cloudbusters Model Airplane Club, Michigan
- Midland R/C Flyers, Michigan
- Tulip City Air Force, Michigan
- Whirlwind R/C Club of SW Michigan
- Bits and Pieces R/C Flying Club, Michigan
- Petoskey Academy of Miniature Aircraft, Michigan
- Skymasters R/C of Michigan
- St. Paul Model Radio Controllers Inc., Minnesota
- Muscatine Miniature Aircraft Association, Iowa
- River City Radio Control, Iowa
These clubs were presented banners in February and can use them at their fields or shows. District resources available to clubs:
- Frequency monitors (available from frequency coordinators for return-shipping cost)
- Tabletop displays and updated materials
- Videos and literature from AMA HQ (free)
I will attend the first EC Meeting in 1995 at Muncie. A travel tip: a scenic route via I-69 south from I-94 past Fort Wayne and through Markle can cut nearly 20 miles off the trip.
Note: some members received two membership cards due to a printing mistake; the duplicate batch was an attempt to ensure timely delivery.
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AMA News — Closing Note
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