If the APR library is installed and working, Tomcat will send ajp flush-packets. If the APR library is not install or not working, Tomcat will not send ajp flush-packets. The cause is, that Tomcat choses either org.apache.coyote.ajp.AjpAprProtocol or org.apache.jk.server.JkCoyoteHandler as the backend for the AJP connector depending on whether APR is usable. AjpAprProtocol sends flush-packets, JkCoyoteHandler does not. There seems to be org.apache.coyote.ajp.AjpProtocol, which supports flush-packets too. This might be work in progress. Please either stabalize org.apache.coyote.ajp.AjpProtocol or extend JkCoyoteHandler. Last Version tested: Tomcat 6.0.10
The AJP connectors in trunk (7.0.x) both do flushes now.