NASA studied the amount of EPNL reduction for the following nozzle configurations: chevrons were installed only on the fan exhaust, only on the core exhaust, and on both.
A substantial benefit in EPNL occurs when the vanes have dissimilar angles of attack, with the upper pair at smaller incidence than the lower pair.
They also considered the addition of a porous wedge-shaped fan flow deflector and show FFD increases the EPNL reductions to 5.
Through these discoveries, EPNL has demonstrated the prospectivity of a new oil play, which is known as "deep Delta".
Thus, Elf thoroughly reinforced its position in Nigeria and EPNL is now one of the major subsidiaries of the Elf group in terms of proven reserves.
The noise reduction hardware ordered by USAir offers a cumulative noise reduction of 17 EPNL
dBs as compared to currently certified Stage II DC-9s operated today.