Muffler

A compact muffler for mounting to an engine exhaust system of a UAV, the compact muffler comprising a single interior chamber having a fixed volume, the interior chamber is in direct fluid communication with a muffler inlet and a muffler outlet, the interior chamber provides a single gas flow path extending between the muffler inlet and the muffler outlet whereby gas entering the chamber through the muffler inlet travels along the single gas flow path before exiting through the muffler outlet, wherein a casing provides a first internal wall and a second internal wall therein, the first internal wall extending from a portion of a first sidewall which is adjacent the muffler inlet and terminating a distance short of a second sidewall, the second sidewall being opposed to the first sidewall, the second internal wall extending from a portion of the second sidewall which is adjacent the muffler outlet and terminating a distance from the first sidewall, the first internal wall and second internal wall forming the single gas flow path whereby the single gas flow path comprises a plurality of adjacent flow passages, the plurality of adjacent flow passages being arranged so that the single gas flow path utilizes the entire volume provided by the chamber, wherein each internal wall incorporates at least one opening therein which defines at least one bypass passage between adjacent flow passages for further communication between the flow passages and to promote an equalization of fluid pressure within the adjacent passages;

• and wherein said muffler inlet is disposed in a first vertical plane and said at least one bypass passage is disposed in a second vertical plane extending substantially perpendicularly to said first vertical plane.