Originally Posted by
Meikleour
tdracer: Do you have any knowledge of the "pod nod" applied to the R-R engined B747-2/300? I was told that although the airframe was optimised for M.86 cruise it was more commomly cruised slightly slower with a commensurate higher cruise pitch attitude. The "pod- nod" applied a slight droop to the pods giving a better alignment for the slower cruise speed and hence a slight fuel burn improvement.
No, sorry. I didn't start working the 747 until the mid 1980's. We did some work on inlet droop on the Pratt powered 767 in the mid 80's but it never amounted to anything.
The only 'pod nod' I'm familiar with was actually "pod nodding" - also known as "orbiting engine". There was an instability in the fuel control of the early CF6-80C2 engines that could couple with the natural frequency of the strut and cause the inlet to move in a little orbit that could be seen and felt from the cabin - rather disturbing but fortunately it turned out to be an easy fix...