Sound & Model Aeronautics
Howard Crispin, Jr.
MORE OF THE STUDY: One major factor in the detection of sounds generated by aircraft (and certainly true with our model aircraft) is the relationship between aural detection criteria and background sound levels. In the absence of any ambient noise an aircraft signal may be heard if its level is above the threshold of audibility for the listener in the relevant frequency range. Studies have been made with pure tones and with octave bands of constant spectral level; references to both appear in various publications.
Without going into the analysis, the study found that two curves are almost identical and that any differences are less than the errors resulting from source and path estimates. The agencies involved in the study therefore used pure-tone thresholds for evaluation of detectability of aircraft noise. This summary will avoid the mathematics and relate the physical results as much as possible.
Observers (in our situation, our neighbors) are never in a noise-free environment. Ability to detect a sound is affected by the level and frequency distribution of the background noise. Several methods were used to determine the effect of background noise; the study used aural detectability through subjective testing and the application of the theory of signal detectability.
Psychoacoustic judgment tasks were conducted using different background noises (jungle day, jungle night, and suburban—keep in mind this was essentially a military-application study) and various received signals including tones, bands of noise, combinations of these, and measured aircraft flyover noise. It was pointed out that correct detection does not imply recognition; recognition may require higher levels than those for detection.
Charts were developed showing the levels at which given sound signals were detectable under specific background conditions. Results show that detection level is affected by background noise and by frequency. Ambient or background noise varies from place to place and from time to time. High background noise levels result in high detection thresholds, which greatly increase the altitude (or distance) at which an aircraft can be detected. To reduce detectability under specific conditions, the noise source (the aircraft) must be made to operate at lower sound levels or operate at higher altitudes.
For radio-controlled aircraft: exhaust and blade-passage frequencies tend to occupy a rather narrow range, but considering the entire spectrum and harmonics can reveal additional problems. In general, higher-frequency sounds are more easily detected than low-frequency sounds (i.e., they can be detected against lower background-noise levels). Models typically operate from near ground level up to 500–700 feet. Instead of straight altitude, consider slant range to neighbors, since models should not be flown directly over them.
Reducing exhaust frequency (and thus blade-passage frequency) can reduce source sound levels. Improving mufflers will further reduce exhaust-frequency sound. Selecting efficient propellers will reduce harmonics. Most modelers use low-cost sound meters that do not indicate harmonics; accept this fact and work toward effective, efficient systems.
Under many conditions, models will be detectable at very short distances in rural settings where ambient levels are around 35 dBA. Detection thresholds can be even lower for frequencies above 1,000 Hz—figures down in the low 20 dB range and source sound levels measured near 25 dBA were reported at the study site. This means you must be very quiet, or at a large slant range distance from your neighbor, to avoid detection.
Example calculations:
- An aircraft measuring 90 dBA at 9 feet would be at the detectable threshold if kept at a 15,000-foot slant range from the neighbor.
- In areas with ambient around 45 dBA, that same aircraft (90 dBA at 9 ft) would match the background at about a 1,600-foot slant range. If a 5 dBA problem threshold above background is allowed, the minimum distance becomes about 1,000 feet.
Knowing the background sound level in your neighborhood is important. Scan the area with a sound meter during your hours of operation and determine background ranges; arranging hours of operation or locating the field with a highway or other constant noise source behind you can help. Next time we will look at "Path" and how this affects our operations as users of airspace for sport.
Happenings at Muncie
This will be a very busy season at our facility in Muncie. We have 22 events scheduled. The Free Flighters have found a "home" and have seven events scheduled; it is now considered one of the best free-flight sites in the eastern U.S.
We are in Phase Two of our Flying Center development. This addition will provide minimal facilities to host a Nats in 1996. Under construction is a runway complex and parking facility to handle Pattern, Pylon, Scale, and other RC events. We are also adding hard surface to accommodate Control Line events when used with the original general-purpose site.
Further improvements for the Free Flight area will come from the McLaughlan Estate, a gift designated for that purpose. We hope to have the new runway complex in place for the upcoming Pylon World Championships in August. August will also feature Large-Scale Racing and a hot-air-balloon event staged by the City of Muncie.
Operating costs in Muncie are down compared with Reston, Virginia, and the facility is intensively used and attracting national and international attention. Remember the one-hour ESPN coverage last year featuring our new facility, museum, and the T-6 Race. Our goal is to provide a focus for model aviation that draws public awareness and benefits modelers nationwide.
The Future
There seems to be no limit to how far we can go in model aviation. The challenge for creation and accomplishment is always there for those with vision. The role of the Academy is to encourage research and development in a way that is fun, safe, and available to all. We cannot be everything to everyone, but we want to use resources to bring the largest benefit to the most flyers. Safety is a major issue as available technology sometimes exceeds pilots' ability and skill to control it; we must balance fun and safety.
Until next month—FLY SAFELY!!
PROFILE: Charlie Minton
Charlie Minton is the owner, engineer, and manufacturer of equipment for the large-engine fraternity. His company is Air Hobbies, 1621 Liberty Ridge Road, Concord, NC 28025. Charlie first gained notice with an engine mount-muffler assembly machined from aluminum stock and supplied with vibration isolators. The unit is made in several sizes to fit a number of engines.
Debate often arises about the effectiveness of any unit in reducing sound level; much depends on the engine/propeller combination and how you operate it. Consider a 24-inch propeller turning at 8,000 rpm—tip flow is in excess of .75 Mach. This applies to Air Hobbies' systems as with any other. Charlie's units are well made and effective. Vibration isolation is important; Charlie recently changed isolation components to improve consistency and quality.
Air Hobbies also provides engines, electronic ignition, engine rebuilding (including crankshaft straightening), and other parts and services.
Sound / Crispin
Continued from page 131
(See "MORE OF THE STUDY" above for the main study discussion.)
Executive Director's View from HQ
Jerry Rouillard AMA Executive Director 5151 E. Memorial Dr., Muncie, IN 47302
The National Flying Site is really starting to look and feel like the National Flying Site—perhaps due to increased activity or more members visiting the museum. New construction of control-line circles and a multipurpose runway complex (Stage Center) is giving the thousand-plus acres a unique identity tied to model aviation. It will become internationally known as the official home of model aviation.
This summer's National Championship events on-site have gone well enough to assure us that hosting the entire Nats at Muncie next year should be successful. A side benefit has been getting acquainted with leaders of Special Interest Groups: Larry Sribnick (NEAC), Bob Beecroft (NFFS president), and Shaun Ettinger (IRCHA president). With increased reliance on SIGs for operational control, it has been valuable to meet them and find ways to serve their members better.
Construction has presented challenges—tons of dirt moved, Indiana soil variability, schedule issues—but the purpose is to create facilities sufficient to handle the entire Nats next year. New control-line circles allow CL Speed events; the Stage Center accommodates this year's World Pylon Championships and Pylon and Pattern events for next year. Plans will add another site for Pattern and Free Flight at the south end of the property by early next summer.
To coordinate site development, we hired Gary Hover as construction supervisor. Gary's work has been invaluable.
Not everything has been competition or construction. The annual Homecoming in early June brought modelers and newcomers for a weekend of fun and flying. The full-scale EAA Young Eagles program and AMA provided introductory RC and control-line flights for youngsters; 60 youngsters rode in their first airplane flight. It's a great introduction to aviation.
AMA now owns and operates a premier model aviation facility; the organization is redefining its role and taking an active part in shaping the future of aeromodeling. If you're interested, come visit Muncie and see your National Flying Site.
DISTRICT I REPORT
Connecticut / Maine / Massachusetts / New Hampshire / Rhode Island / Vermont Don Krafft, Vice President PO Box 1828, Duxbury, MA 02331-1828 (617) 934-6248
Associate Vice Presidents:
- James M. Semonian, 166 Allen Road, Billerica, MA 01821-5240
- Bob Landry, 80 Main Street, Essex Junction, VT 05452-3146
- M. C. McGuffin, 8 Robinson Street, Houlton, ME 04730-2312
- Harry S. Newman, 36 Sherwood Drive, Hooksett, NH 03106-1077
- Richard Sherman, 28 High Street, Plymouth, NH 03264-1223
- Ed Thompson, 27 E. Greenwich Ave., West Warwick, RI 02893-5405
- Bob Wallace, 91 Sylvan Street, Avon, CT 06001-2230
Frequency Coordinator:
- George Wilson, 82 Frazier Way, Marstons Mills, MA 02648-1866
LOU ANDREWS: Correction—last month’s column listed the wrong date. Lou Andrews passed away on May 10, 1995 (not May 11).
495th SQUADRON SCALE SHOW: The show, organized by Art Alfano for five years, was passed this year to Bill Salter, who did an excellent job. The event was held March 7, 1995, at the Lutheran Church in Chelmsford. Twenty models were displayed; each exhibitor received a certificate and a bottle of CA adhesive. Thanks to Ralph Dionne for the snack bar. Apologies for missing photos; those who displayed models included:
- Richard Carlson – Douglas Dauntless SBD4
- William Salter – Nieuport 17
- Vern Nauk – Roland C-2
- Vincent Nauseda – SNJ
- Art Alfano – Laser 200
- Ed Silva – de Havilland DHC-2
- Gus Deltwas – Stinson L-5
- Bruce Killam – Fly Baby
- Joe Callant – Stinson Reliant
- Dick Bartlett – WACO YMF5
- George McKay – B-17E
- Rupert Kosmala – Marquart Charger
- Bill Curiss – WACO YMF5
- Charles Nelson – WACO YKS-7
- Tom Kosowski – Fokker D.VIII
- Lindsey Smith – Japanese Zero
- Ron Gagner – SNJ
- Hank Ilzsch – Avro 504
- Robert Rulle – F-4 Phantom
- Ed Vrablik – EAA Bipe
In one of my first columns as VP I mentioned a new kit—a control-line old-timer re-kitting of the deBolt All American Sr., produced by Easy-Built Models. It’s finished (pictures #1 and #2). Colors are red, white, and blue, with plenty of stars. Maiden flight was on the 4th of July. The engine is a Fox .35 donated and prepared by Larry Lundy, using a George Aldrich piston and sleeve. Larry also provided wheels, prop, lines, and encouragement. If someone from the Circle Burners sends a stunt pattern, I can practice for their old-timer event on October 8.
DISTRICT III REPORT
Ohio / Pennsylvania / West Virginia Bob Brown, Vice President 35 Sanford Street, Bradford, PA 16701 (814) 368-7655
Associate Vice Presidents:
- Mike Barbee, 6651 Calgary Court, Columbus, OH 43229-2008
- David H. Ellis, 5261 Dewitt Road, Cross Lanes, WV 25313-1209
- Nelson Gould, 1944 S. Idaho Street, Allentown, PA 18103-8519
- John Hathaway, 702 Woodrowne Drive, New Stanton, PA 15672-9449
- Donald Knopp, 300 West Valley Forge Road, King of Prussia, PA 19406-1881
- Joseph S. Vlasiy, 1381 Cranbrook Drive, P.O. Box 851, Maumee, OH 43537-0852
- Lawrence R. Weimer, 15613 Greendale Avenue, Maple Heights, OH 44137-3715
- Frank Noll, 4573 Lamme Road, Dayton, OH 45449
Frequency Coordinator:
- John Cottle, 1012 Wyoming Avenue, Forty Fort, PA 18704 — (717) 287-8970
New AVP for Ohio: Frank Noll Jr. has been named the new AVP for southwest Ohio. Contact: 4573 Lamme Road, Dayton, OH 45439; Tel: (513) 296-1290. Thanks to Mark Wilson for his service as AVP.
AMA Homecoming 1995: Associate VPs Nelson Gould, Frank Noll, and Joe Vlasiy attended and saw the new facilities under construction. Invite them to a club meeting or visit the National Flying Site to see developments firsthand.
District III Activities: The Dayton Sector Flying Aces Club sponsors a late-July contest at Wright Field, Ohio, featuring rubber-powered free flight and mostly flying-scale models. A unique perpetual trophy—the rudder from a 1927 Consolidated PT-1 trainer—is awarded to the meet’s grand champion (1994 Grand Champion: Stu Weckerly).
SPARKS Mall Show: On the weekend of May 5, 1995, the South Park Area Radio Kontrol Society held their annual mall show at Century III Mall in West Mifflin, PA. Thanks to Fred Berman for the picture.
Mansfield Area RC Society: Dick Sheppard and the Mansfield Area RC Society continue to produce one of the most popular large-scale events in District III.
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, Box 296, Kill Devil Hills, NC 27948
- Doug Holland, 3517 Fernwood Drive, Raleigh, NC 27612-6215
- Scotty Moyer, 11 Orchard Lane, Wilmington, DE 19809-1719
- Richard (Dick) Smith, 761 Gwynne Avenue, Waynesboro, VA 22980-3346
Frequency Coordinator:
- Paul Yaccobucci, 6408 Winthrop Drive, Fayetteville, NC 28311-1007 — Evenings: (919) 488-5985
Aerobatics
Dick Smith, Associate Vice President, has been judging Radio Control Aerobatics and Scale. He recently served as a judge at the F3A Team Selection competition. The team consists of Bill Cunningham, David Von Linsowe, and Chip Hyde; the alternate is Chris Lakin. Congratulations to these representatives at the upcoming F3A World Championships.
IMAA Rally (Danville)
The IMAA Rally of the Giants, held at Danville, Virginia, was outstanding. Despite heavy regional rainfall and flooding, daytime flying was unaffected at the Danville Airport; nighttime rain did affect some parking. The event had tremendous community support from the City of Danville, Parks and Recreation, the Airport Authority, the Chamber of Commerce, and industry.
Many pilots flew as much as they wished; five pilot positions were busy. While several aircraft were lost, none were due to interference—only a couple of transmitters were left on (a scanner was used). One transmitter was lost on the last day, likely someone picking up the wrong unit.
Appreciation goes to the Danville Aeromodellers, club President Buddy Green, and Contest Director John Estlow (and Judith Estlow). Reports of the event will appear in IMAA High Flight and Model Aviation. The event moves to Lake Charles, Louisiana, in 1996; District IV may bid to host again in 1997.
Aeromodeling and Education
Aeromodeling should be integrated into school systems to supplement aerospace-technology education. Some local programs exist but are often not part of formal curricula. Organizations can provide outlines and materials for educational incorporation at all levels, including college.
In Virginia, the Virginia Aviation and Space Education Forum promotes aviation and space education in schools and public groups and works with NASA and other agencies. The Forum’s purpose aligns with AMA bylaws in promoting aerospace understanding and career awareness. AMA can support these efforts by participating as an organizational member, promoting the Forum’s agenda, and working with educational institutions.
The Virginia Aviation and Space Forum held its annual open house at the Virginia Aviation Museum, a division of the Virginia Museum of Science. The Richmond Area Radio Control Club represented aeromodeling with static and flight displays in a cramped but effective space.
AMA News
New Fields and Openings
- HUNTSVILLE, AL: The Rocket City Radio Controllers dedicated the Capt. Trey Wilbourn Model Airplane Park with a grand opening on June 24. The new site is near the old airport and golf course.
Florida Anecdote
North Florida has been quiet, but Manny Sousa (USN Capt., Ret.) recently returned from a trip that included marrying his high-school sweetheart Carin in Hollywood, CA. They encountered several disasters—fires, an earthquake, and flooding—while honeymooning, then bought a house in Gulf Breeze. They attended the King Orange Scalemasters Qualifier in Odessa, FL, where Manny flew Sport Scale and finished just a few points out of first. Dr. Bill McCallie ran a very well-managed contest.
Prediction: things will soon come to life again in the Gulf Breeze/Pensacola area.
Mooseheart, IL
The third annual Hobby-Works Air & Water Invitational was held May 13 at Mooseheart Child City and was free to spectators. Weather reduced flying, but some pilots flew off the lake between showers. Wind gusts to 30 mph made flying challenging. The air-sea rescue team (Steve Gawliks and Armin Weber) retrieved models from the water.
FCC/AMA Equipment Labeling
Manufacturers are no longer required to put gold stickers on equipment manufactured after December 31, 1994. All FCC-certified equipment manufactured after 1991 meets FCC/AMA requirements. After December 31, 1994, only equipment manufactured before 1991 will need gold stickers to prove it has been updated to 1991 standards for use at AMA charter club fields or AMA-sanctioned events.
Kansas City, MO
Smithville Lake is a stop in the Unlimited boat-racing circuit. For three years the Clay County Parks and Recreation Department has invited the Northern Knights Model Airplane Club to fly and exhibit aircraft, providing an area, passes, and a tent. About 30 club members participated.
Four RC clubs north of the Missouri River (Northern Knights, Sunchasers, Flying Tigers, Smithville Dambusters) enjoy good relations; the Dambusters shut down their field to enable the Northern Knights to stage this event.
St. Louis, MO
A great CL Combat and Carrier contest was held April 30. The pit area and Combat action were well documented. Thanks to Rich Frost for pictures.
Muncie, IN
On June 10–11 over 200 fliers experienced control-line modeling for the first time at the AMA Homecoming 1995. Thanks to the Muncie Controllers, Sig Manufacturing, and Fox Manufacturing, many young people flew Sig Skyraiders. Most fliers were under 15; the youngest was three-year-old Vincent Woodard who flew with his grandfather Allen Goff. A highlight: Jeromy Moon, 14 and wheelchair-bound, flew his first flight to a cheering ovation. Information and picture courtesy of Allen Goff.
Rockford, IL
The Rock Valley Flyers hosted their race of the year on June 15. Winds shifted unexpectedly to the northeast at 20 mph, resulting in tailwind takeoffs for the fourteen racers. Dan Kane flew a new version of his Hurry Kane and turned 1:08.16 to place 2nd. Nelson engines dominated the day—only two of fourteen were non-Nelson powered.
DISTRICT VII REPORT
Iowa / Michigan / Minnesota / Wisconsin Peter Waters, Vice President 7420 7 Mile Rd., Northville, MI 48167 Phone: (810) 486-4800 — FAX: (810) 486-1603
Assistant Vice President:
- Don Bentfield, 1440 W. Minnehaha Avenue, St. Paul, MN 55104 — Phone: (612) 645-2984
PR/Insurance Coordinator:
- Joseph M. Hass, 5394 English Drive, Troy, MI 48098
Associate Vice Presidents:
- Dave Gish, 5435 State Hwy 99, Wapello, IA 52653
- Bud Gorman, P.O. Box 33, Knife River, MN 55609
- Russell Kretzinger, 2625 E. Shorewood Boulevard, Milwaukee, WI 53211
- Jean Laska, 305 Putl Place, Holland, MI 49423
- Bill Milar, 712 Grand Ave., Petoskey, MI 49770
- Carl Moots, 5024 Lake Mendota Drive, Madison, WI 53705
- Mark E. Robotti, 26540 Olympic Trail, North Lindstrom, MN 55045
- Mike Zingery, 6486 S. Summerton Rd., Shepherd, MI 48883-9308
Frequency Coordinators:
- West: Al Schwartz, 2787 Fernwood, Roseville, MN 55113
- East: Bert Kelly, P.O. Box 39001, Redford, MI 48239
This column will be photo-heavy with a few notes. I announce my resignation from the VP position at the end of this year. My term would be up for election at the end of 1996, but work pressures and building a full-size plane force this decision. The by-laws call for a special election; we have nominated Joe Hass and Don Bentfield. Both have my confidence.
One photo this month is of a decal I had designed: "Working at 90 dB at 9 ft." The decal recognizes clubs working to reduce noise. The decals are self-adhesive, dark-blue text on white background. Cost: free—send a copy of your flying-field rules that state a numeric noise level (e.g., 98 dB). Rules must include a number (not just "mufflers needed"). Send the rules and I will ship your club 100 free decals. Decals will also be available from AMA HQ once in stock.
AMA News — MORE OF THE STUDY (condensed)
A major factor in detecting aircraft noise is the relationship between aural detection criteria and background sound levels. The study used pure-tone thresholds and subjective testing to evaluate detectability. Background noise types (jungle day/night, suburban) and received signals (tones, noise bands, measured flyover noise) were used. Detection does not equal recognition; charts show detection levels vary with background level and frequency. To reduce detectability, reduce source sound levels or increase operating altitude/slant range. For models, reduce exhaust and blade-passage frequencies, improve mufflers, and choose efficient props to minimize harmonics.
AMA News — Howard Crispin Jr.
I am writing this from an RV campground at Pipestem State Park, West Virginia, listening to rain on the Fourth of July. Clara attended the IMAA National Rally in Danville, Virginia. IMAA has over 10,000 members and promotes large-model interest nationwide; it has chosen to join AMA to foster cooperation among large-model enthusiasts.
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