Automatic Mixture Control
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In Rotax equipped aircraft, this can be accomplished by manually changing jets and jet needle positions, or automatically, by use of a HAC (High Altitude Compensating) carburetor kit.

The High Altitude Compensating system for Bing Carburetors, also, is nothing new. Design and testing goes back to the late eighties.  On an early "proof" flight, the crew from Robertson B1RD company flew a HAC equipped, Rotax 532 powered,  B1RD to over 23,000 ft. automatically maintaining proper mixture.
Green Sky Adventures, Inc., has tested HAC carburetors on five different Rotax engines for over ten years on the company's Zippy Sport. From speeds of 40 mph to 130 mph, from sea level to 15,000 plus feet, the automatic mixture control is flawless.
Until now, the HACs were available only as a complete package which not only included the HAC chamber, lines, and fittings, but also came with two (one if single carb configuration) complete Bing 54 carburetors, and two application specific Rotax/K&N filters.
Green Sky Adventures, Inc. has now introduced HAC technology in a much more affordable package which, in most cases, eliminates the need to replace existing carburetors or airfilters.  Prices start at $189. Installation time is typically one hour. Includes HAC chamber, Fittings, Lines, and Jets.

To order, ph toll free 888 887-5625 or Mobile 352 318-5625 or click BUY

On this engine, a single compensator (HAC) regulates pressure to each carburetor float bowl  there by changing the mixture. Changes in density altitude are sensed through a static line on one  airfilter to affect deflection of a diaphragm in the HAC chamber.  The diaphragm moves a metering pin which varies vacuum (pressure) to the float chamber(s)

Caution! The HAC alters the mixture of both Carburetors simultaneously. In the event of a differential pressure between the two air filters,  a corresponding differential mixture will result. If  a high pressure exists at the air filter where static pressure for the HAC is sensed, BOTH carburetors will be leaned. For that reason,  on dual carb HAC installations, use of the single oval filter with provision for both carbs is preferred, or a balance tube can be installed between individual filters HAC Chamber

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