Phollingsworth: Why just FBW spoilers for the 767 series. Is this true for other Boeing aircraft (737NG, 744, 757). What is your opinion of the overall 764 design?
While I don't know the exact reason why, I can make a few educated guesses.
1. Up to the 777 it was the only Boeing A/C with primary flight control FBW.
2. As to why the spoilers are FBW it is probably to save weight and complexity in a relatively complex control system, where the panels used and the deflections change a fair amount over the operating envelope. Remember that the 767 was designed during the 1970's fuel crises. Saving fuel was a primary driver, hence the 2-3-2 cross-section.
3. As to why the 757 isn't FBW, remember the 757 is a completely different aircraft from the 767, from a structural and mechanical point of view. They were designed by different groups, with the common type-rating a later add on. The differences between the two airplanes always drove me nuts.
As for the 767-400, I think it is a pretty good aircraft. It is basically a drop in replacement for the L1011-1/200/250 and the DC-10-10. Something that the 772, A333, and the A332 are not. The program was driven by Delta's instance that they wouldn't buy a 777 to replace the L1011 as the 772 is significantly larger.
DL wouldn't go Airbus at the time given the bad blood that stemmed from the return of the A310-300 leases. The 764 holds the same number of people as the L1011, has almost the same wing-span, and will fly anywhere that the L1011-1/250s would. This is critical due to gate spacing in
ATL and other airports. There are 4 gates which
DL controls in
ATL that can handle the A330/340s,
MD-11, and 777. The gates on Concourse E can handle these A/C, but
DL pays for each use.
All in all the 764 is a niche A/C, had Boeing gone through with the true
ER version, Kenyan(?) was the only customer at the time of the economic downturn and the Sonic Cruiser start-up. The A/C may have gotten more orders (incidentally, the aircraft would have used the A380 class powerplants).