Editing Pusher configuration (section)

====Propeller efficiency and noise====
The propeller passes through the fuselage wake, wing wake, and other flight surface downwashes—moving asymmetrically through a disk of irregular airspeed. This reduces propeller efficiency and causes vibration inducing structural propeller fatigue<ref group="note">The only approved prop for the Rutan pushers is wood, which is more resistant to fatigue damage.</ref> and noise.

Prop efficiency is usually at least 2–5% less and in some cases more than 15% less than an equivalent tractor installation.<ref>{{cite web|first= Don |last= Stackhouse|url= http://www.djaerotech.com/dj_askjd/dj_questions/pushtractor.html|title= Al Bowers gave us an excellent explanation of the stability issues of a tractor vs. pusher installation. However, there are some other issues that need to be considered.|access-date= 25 September 2011|url-status= dead|archive-url= https://web.archive.org/web/20111121030726/http://djaerotech.com/dj_askjd/dj_questions/pushtractor.html|archive-date= 21 November 2011}}</ref> Full-scale wind tunnel investigation of the canard [[Rutan VariEze]] showed a propeller efficiency of 0.75 compared to 0.85 for a tractor configuration, a loss of 12%.<ref>{{cite tech report|first= Long P.|last= Yip|first2= Paul F.|last2= Coy|date= March 1985|title= Wind-Tunnel Investigation of a Full-Scale Canard-Configured General Aviation Airplane|institution= NASA Langley Research Center|location= Hampton, Virginia|url= https://permanent.fdlp.gov/lps54941/lps54941/ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19850011615_1985011615.pdf|url-status= live|archive-url= https://web.archive.org/web/20210508143622/https://permanent.fdlp.gov/lps54941/lps54941/ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19850011615_1985011615.pdf|archive-date= 8 May 2021}}</ref> Pusher props are noisy,<ref name= "Technicalities" /> and cabin noise may be higher than tractor equivalent ([[Cessna XMC]] vs [[Cessna 152]]).<ref name="1000aircraftphotos.com">{{cite web|first1= Johan|last1= Visschedijk|first2= Walter van|last2= Tilborg|first3= Karl|last3= Smith|date= 14 December 2003|url= http://1000aircraftphotos.com/HistoryBriefs/CessnaXMC.htm|title= Cessna XMC|website=1000aircraftphotos.com|url-status= live|archive-url= https://web.archive.org/web/20080130150407/http://1000aircraftphotos.com/HistoryBriefs/CessnaXMC.htm|archive-date= 30 January 2008}}</ref> Propeller noise may increase because the engine exhaust flows through the props. This effect may be particularly pronounced when using turboprop engines due to the large volume of exhaust they produce.<ref name= "ask don" />