It won't take longer. That is simply incorrect.
You are all so fond of examples, so if you climb or descent do you first change thrust and then you raise or lower the nose to maintain speed. (in a trimmed aircraft this would happen aerodynamically anyway).
The power excess or deficit is what makes you climb or descent.
Say we have an aircraft at 2000ft, fully configured and stable and trimmed Vapp, there are no external disturbances (wind, up/downdraft) and no weight changes.
This aircraft has a certain energy (performance) that is required to fly a 3 degree path. this energy does not have to change until landing as there are no disturbances, so no changes in pitch or power are needed.
If we then add external factors to this equation the situation changes: say we emcounter a downdraft. The required energy to maintain the desired path increases.
The actual energy of the aircraft (performance) is determined by pitch + power/ thrust. Due to the increased requirement of energy to maintain the path we are faced with an energy deficit.
I have 3 options:
1. increase pitch trading speed for for height, this will result in speed loss which reduces the energy state thus you need to add energy with thrust.
2. increase thrust, this directly increases the energy state balancing it with the energy requirement
3. increase pitch trading speed for height and increase thrust directly adding energy to the airframe
So thrust simply gives us a tool to increase/decrease the energy of the aircraft. whereas pitch only allows us to convert 1 type of energy into another. As with all energy conversions energy is lost (heat/drag/etc) so in the end you will still end up with a deficit that needs to be compensated for.
Both thrust and pitch control the path.
Adding thrust always adds energy, it doesn't always increase speed.
Thrust for speed is just a tool to allow people to easily manage the energy. But that is only because we use speed as a measure. whereas energy is more then just speed, its also mass, height etc....
In a balloon you could dump mass to counter for a downdraft.
Last edited by 737Jock; 26th Mar 2014 at 13:57.