Further research on the topic of spillage drag has led me to the text Gas Turbine Performance (P.Walsh/P.Fletcher) where it mentions spillage drag can range from 10 - 20 percent of internal drag in a pure turbojet, to appoximately equal to internal drag at a bypass ratio of 5:1. This does corrolate with the disconnect between the data from the old NACA reports using straight jets against what is being put forward here.
Its a good day when one sets off to prove someone wrong only to demise by his own sword!
The text references data from ESDU 81009, 84004 and 84005 - if anyone has access and could summarize it would be greatly apperciated.
Last edited by mrfox; 1st Nov 2019 at 06:32.
Reason: addd ESDU reference