If 3 engines is better than 2, then they should make a commercial version of the B-52.

As for ETOPs concerns, when you spend some time away from a divert field (ETOPs is not just about water) you soon realize you should fear a cabin fire way more than an engine failure.

How can that be? Don't the gas turbine cores of the turbofan engines operate most efficiently at maximum load?

Most of the thrust of a turbine is produced in the last 10%. About 2% of the total thrust per percentage of speed.

Turbines idle high.

I see a conceptual error here.

It is true that after the engine failure both aircraft would have the same total power remaining and would use the same amount of runway to continue the takeoff. However, since the twin has more total thrust with all engines operating, the twin gets to V1 (engine failure speed) in much less runway. Therefore the twin uses less total runway for takeoff.

Another minor point is that the regulatory requirement for climb gradient after an engine failure is slightly lower for a two engine aircraft than for a three or four engine aircraft.

Joe

As to the first point, yeah you're right you wouldn't get the same runway requirement with 75% of the max power, but it is going to be some percentage less than 100%. Maybe you need 83% of the power. Whatever it is, it is some number less than what a twinjet needs, which raises the question of which engine configuration is going to be more efficient at cruise.

As to the second point, yeah thats definitely another factor. Is it only the minimum climb gradients required that are higher for trijets, or will every airport (even the ones that have higher than normal climb requirements already) have higher requirements for trijets?

Don't confuse the climb gradient required for Part 23/25 certification with climb gradients required by TERPS for terrain avoidance.

Talk to any of the UPS pilots on the forum that flew the DC-8-73 series with the CFM-56 engines. In their configuration, you ran out of wing a long time before you ran out of engine and one had to be very careful at the higher altitudes. Definitely an example of an "overpowered" aircraft. Due to well trained crews it didn't present significant problems but nonetheless, it was overpowered.

G'Day Mates....and check those mach speeds (low and high) for FL390.

You don't have to imagine, just ask anyone who flies a 727 or DC10. Or even your local aircraft fueler for FedEX.

I've never been given an official explanation, but my best guess is that it is to give the number two engine it's own independent fuel source and prevent an imbalance situation that might result if it drew fuel from the wings. Someone correct me if I'm wrong.

The Globe Swift started off with an 85HP engine, enough power to take it to the crash site. The engine was upgraded until today Swift's are like snowflakes, no two alike. It is not uncommon to find Swifts with 180, 210 and more HP BUT the rudder and the vertical fin was never changed. You can run out of rudder especially if there is a strong crosswind from the left.

And then there was the Hawker Sea Fury... knew a guy who flew them and he said that if you went to full power (above 50-55in) the airplane would be skipping across the runway with full left rudder (engine operates the other way). and more than a few of the big pistons have been torqued over on botched go-arounds.

Lost a P-51 in Camarillo, California 3 years ago with a low speed, high power go-around. Plane rolled inverted and struck the earth at about 45 degrees, upside down. Totaled and dead. First solo in the plane.