Originally Posted by
MikeMpls
But then by definition they haven't disappeared. They're just playing hard to find.
Surprised to hear about the 757 being slower, given that it also has a reputation for being one of the most overpowered planes around.
Critical and normal operating Mach are governed almost totally by wing sweep angle. 757s have less sweep than other transports. This yields benign stall characteristics and more lift at lower airspeed than with higher sweep angles, at the cost of lower Mach operating envelope.
Takeoff and initial climb performance are primarily determined by power/weight ratio.
On the 57, the combo of limited sweep and high PWR is deliberate. They have great takeoff performance and nobody needs fear the consequences of engine failure at V1 or V2. During marketing, Boeing demonstrated by performing a single engine takeoff at Lhasa. A heavy 773, by contrast, has utterly dismal OEI performance and can barely crawl away from the flat DXB runway environs at the minimal certification threshold of 300 fpm.
This is why a 752 serves markets like BOG, UIO and others. OEI performance on 737 NGs, except light -700s, isn't good enough, so despite their apparent similarities and DOC advantages, we won't see 739ERs serving those markets any time soon.
For some missions, a 752 is the right solution. But TATL has been a stretch, that wasn't one of the original design specifications.