The US Aviation Cumulus is an American
low-wing
A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple planes.
A monoplane has inherently the highest efficiency and lowest drag of any wing confi ...
, single-seat, open cockpit
motor glider
A motor glider is a fixed-wing aircraft that can be flown with or without engine power. The FAI Gliding Commission Sporting Code definition is: a fixed-wing aerodyne equipped with a means of propulsion (MoP), capable of sustained soaring flight ...
that was designed by Dave Ekstrom and produced by
US Aviation, supplied in
kit form for amateur construction.
[Vandermeullen, Richard: ''2011 Kit Aircraft Buyer's Guide'', Kitplanes, Volume 28, Number 12, December 2011, page 73. Belvoir Publications. ][Bertrand, Noel; Rene Coulon; et al: ''World Directory of Leisure Aviation 2003-04'', page 59. Pagefast Ltd, Lancaster OK, 2003. ][Purdy, Don: ''AeroCrafter - Homebuilt Aircraft Sourcebook'', page 314. BAI Communications. ][Downey, Julia: ''2008 Kit Aircraft Directory'', Kitplanes, Volume 24, Number 12, December 2007, page 77. Primedia Publications. ][Downey, Julia: ''1999 Kit Aircraft Directory'', Kitplanes, Volume 15, Number 12, December 1998, page 74. Primedia Publications. ][Bayerl, Robby; Martin Berkemeier; et al: ''World Directory of Leisure Aviation 2011-12'', page 138. WDLA UK, Lancaster UK, 2011. ]
Design and development
The Cumulus was conceived as a lightweight motorglider for soaring and also for touring.
It is a replacement of the earlier
US Aviation Cloud Dancer design.
[Higdon, Dave]
"Race to Cloudbase: Flying the All-New Cumulus Motorglider,"
July 1997, ''Ultralight Flying!'' magazine, United States Ultralight Association
The United States Ultralight Association (USUA) is a non-profit organization that endeavors to support ultralight aviation and ultralight aircraft
It is the oldest ultralight organization in the US, formed after motors began appearing on hang g ...
, Issue 225, retrieved September 20, 2020 The Cumulus first flew in 1995 and was named after the
cumulus cloud.
Developer Dan Johnson initially outsourced aircraft engineering and production to
AeroDreams
AeroDreams S.A. is a defense contractor based in Buenos Aires, Argentina. It has been working since 2001 in developing unmanned aerial vehicles for military and non-military use. The company's CEO is Raúl Fernández.
The company developed and ...
, where the original kit designer / producer was Walter J. "Jim" Collie,
["Aviation Accident Final Report: Accident Number MIA98LA084... N1171U... 2/24/1998...,"](_blank)
National Transportation Safety Board, also reprinted a
PlaneCrashMap.com
and summarized a
NTSB's "Aviation Accident Data Summary: Accident Number MIA98LA084..."
retrieved September 20, 2020 with an assistant designing the fiberglass cabin.
from "The-Grand-Design.com", by an apparent co-designer, retrieved September 20, 2020 Initially, about eight kits were delivered, but production was halted for about four years, following a fatal accident that killed Collie and destroyed the prototype.
Eyewitenesses reported hearing a loud "pop" and seeing the left wing departing the plane in flight. An
NTSB
The National Transportation Safety Board (NTSB) is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and inci ...
investigation concluded that the probable cause was "debonding of the leading edge to spar cap joint, which resulted in inflight separation."
Johnson later conceded that "the project needed someone who understood building techniques better than I did. That man was Dave Ekstrom and he ultimately took over my design."
[Johnson, Dan:]
"Remember the Cumulus Motorglider? It's Flying!,"
May 2008, ''Aviator's Hotline: Light Aviation Edition,'' -- also reprinted a
retrieved September 20, 2020
After 2004, the Cumulus was developed and produced for US Aviation, by Dave Ekstrom, president of
Ultralight Soaring Aviation, in
Bemidji, Minnesota
Bemidji ( ) is a city and the county seat of Beltrami County, in northern Minnesota, United States. The population was 14,574 at the 2020 census. According to 2021 census estimates, the city is estimated to have a population of 15,279, making i ...
, as the
New Cumulus.
["Ultralight Soaring Aviation Re-Intro's Cumulus Motorglider"](_blank)
April 04, 2004, Aero-News Network, retrieved September 20, 2020 According to Ekstrom, "When we completed this task, US Aviation sold us all design rights to the remainder of the aircraft as well as other assets," and Ultralight Soaring also "obtained the inventory created by AeroDreams."
Built from steel tubing (fuselage cage originally reinforced with 4130 chromoly tubing
) surrounding a partially-enclosed pod,
at the end of a 5-inch-diameter, seamless 6061-T6 aluminum main fuselage/tailboom tube,
composites and
fabric
Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not th ...
, the Cumulus is powered by a standard
Rotax 447
The Rotax 447 is a , inline 2-cylinder, two-stroke aircraft engine, built by BRP-Rotax GmbH & Co. KG of Austria for use in ultralight aircraft.Raisner, William: ''LEAF catlog'', pages 6-105. Leading Edge Airfoils, 1995.
Design and development
...
engine in
pusher configuration, although engines from can be fitted. The dope-and-fabric-covered cantilever low wings
are detachable for transport or storage. It has a glide ratio of 20:1. The
landing gear
Landing gear is the undercarriage of an aircraft or spacecraft that is used for takeoff or landing. For aircraft it is generally needed for both. It was also formerly called ''alighting gear'' by some manufacturers, such as the Glenn L. Martin ...
is
conventional and the
cruciform tail __NOTOC__
The cruciform tail is an aircraft empennage configuration which, when viewed from the aircraft's front or rear, looks much like a cross. The usual arrangement is to have the horizontal stabilizer intersect the vertical tail somewhere ...
is
strut-braced.
The aircraft was originally designed to allow removal of one wing without the other dropping, to facilitate single-person disassembly.
Construction time from the kit is estimated at 200 hours.
Specifications (Cumulus)
See also
References
External links
Company website archiveson
Archive.org
The Internet Archive is an American digital library with the stated mission of "universal access to all knowledge". It provides free public access to collections of digitized materials, including websites, software applications/games, music, ...
Photo of Cumulus in flightCumulus page on All-Aero plus specifications and performance data
{{US Aviation aircraft
1990s United States sailplanes
Bowlus aircraft
Cruciform tail aircraft
Motor gliders
Aircraft first flown in 1995
Single-engined pusher aircraft
Low-wing aircraft