Thrust to weight! Whether an F-15 in full burner or a light loaded airliner at full power, it is the thrust to weight ratio that dictates a shit hot vertical takeoff or lumbering the length of the runway clawing into the air. Even a fighter laden with bombs will struggle into the air. But why do commercial airliners have so much excess thrust? Same reason, payload. Also, in the case of airliners safety and economy.
Safety first: every modern (2 engine) airliner is designed to lose an engine on take-off roll (past V-1), at max weight, climb out, clean up and return for a safe landing. Airline pilots are also required to demonstrate this skill every 9 months or annually, depending on the airline. It requires a lot of excess power, even so every take off in a modern aircraft, except in extreme conditions, is de-rated. Some times as little as 85% power. Even at that de-rated power the single engine profile can be achieved. It is nice to have that excess power in your back pocket as well!
Economy: Why so much excess thrust, and how does having more powerful engines equate with economy? A basic principle is, fuel burn equals power, yes the new engines are much more efficient, but simplistically, this concept holds. The reason more power means better economy is altitude. The higher an aircraft goes, the lower the fuel consumption and the easier it is to get to cruise Mach. Thus, faster across the ground for a lower fuel burn. Factor in winds up there that can be 200 plus miles an hour and you can really use altitude to capitalize on economy.
But I have to say; nothing compares to a max burner, pure vertical take-off. Nothing! And that’s why I wrote the Aviator Series. Stand-by as we move into the age of excess thrust!
I feel the need for some vitamin-G, time for some old war-bird flying….