Morgan and Caster 



Fig. 19 - Pressure distribution 

 on the Doak duct for the static 

 condition (19) 



Mention should be made of the pressure distribution on ducts when the 

 ducted system is at an angle of incidence. Kriebel and Mendenhall (19) have 

 made comparisons between theory and experiment for the full-scale X22A ducted 

 propeller system, discussed previously, for angles of attack of up to 80°. These 

 comparisons are not presented here, but it is obvious that significant improve- 

 ments in theory are needed before reasonable predictions of the duct pressure 

 distributions on the inside can be made for ducted systems at the high angles of 

 attack investigated. 



In summary, the prediction of the duct pressure distribution when a propel- 

 ler is operating within the duct is satisfactory on the outside of the duct but 

 varies between marginal and unsatisfactory on the inside of the duct. This poorer 

 prediction than for the duct by itself is most probably related to the fact that the 

 pressure contributed by the propeller is not properly determined. For instance, 

 none of the experimental data reviewed showed a pressure jump at the propeller 



1332 



