Flight Safety
When you have a look at the power to weight ratio of jets that fly above FL400 you see that the ratio goes above 30%.
Most airlines at the moment are in the high 20% range, a small comparison is below ..
Below is a quick comparison or aircraft, Power/Weight ratio (%), and Range (nm)
- Citation X 37.47% 3250
- Gulfstearm V 32.99% 6500
- B767-400ER 28.22% 5625
- B777-300 29.70% 5720
- A330-200 26.82% 6400
- A340-500 27.84% 8500
- B747-400 27.43% 7259
- B747SP 29.49% 8315
- A380-100 27.22% 7665
When you go above 30% costs for operating go through the roof. The reason for the high power to weight ratio to allow the aircraft get to the altitude (excess power=climb) and to allow a margin on the buffet boundary.
The power to weight ratio is also linked to the direct operating cost of the aircraft via fuel, oil, lube, insurance, maintenance, and depreciation.
SaturnV,
I mentioned the B757 fuse as I counted about 50 rows along the side of the aircraft, 200 seats, 50 rows, 4 across -> single isle.
The AW&ST article has a lot of good engineering sense, and some interesting quotes …
<font face="Verdana, Arial, Helvetica" size="2">The public evidence that this is achievable at Mach 0.95 is sketchy at best, but by comparing improvements in technology between the 767 and 777, and applying that Mach X L/D increment to the 1970s near-sonic studies, an L/D level of 15-16 might be possible.</font>
<font face="Verdana, Arial, Helvetica" size="2">And given a lull in company R&D and cuts in NASA subsonic research, "it's a very tall order to go from this into a new airplane."</font>
<font face="Verdana, Arial, Helvetica" size="2"> "It burns a little more fuel but the operating cost is very competitive with today's aircraft," Bair said.</font>
Michael B. Bair, Boeing Commercial Airplanes vice president for business strategy and development
Wino,
Climb gradients for one engine inoperative 4 engine aircraft are higher than for one engine inoperative two engine aircraft.
FAR 25.121 has the following gross climb gradients for second and third segments
- 2 engine 2.4% 1.2%
- 3 engine 2.7% 1.5%
- 4 engine 3.0% 1.7%
The gross to net margins are
- 2 engine 0.8%
- 3 engine 0.9%
- 4 engine 1.0%
