I have noticed that 732s that are Stage III hushed still pop and crackle like how JT8Ds are supposed to sound unhushed, but on 727s and DC-9s that are Stage III hushed as well, they don't crackle nearly as much? Why is this the case when all 3 use the same JT8D-1 to -17 engines? I know the 732s have a longer tailpipe on them then the installations on 727s and DC-9s, but does some hoe having a longer tailpipe make the mixer less effective?
After all, there is not much bypass air to mix with having a 0.96 to 1 BPR but maybe the longer tail pipe of the 732 makes the mixer less effective because I assume the hot core air still has room and time to override the mixed bypass air before exiting the nozzle allowing more crackle because the hot air is overriding the bypass air? Whereas 727s and DC-9s have shorter tailpipes so the core air and bypass air exit quicker and the bypass air is able to more effectively collide with the core air because of the short time it takes to exit the nozzle.
I could be wrong, but can someone explain what is going on here and how this is happening?
Moderators: richierich, ua900, PanAm_DC10, hOMSaR
Who is online
Users browsing this forum: No registered users and 39 guests