Energy is simply the sum of potential and kinetic energy. It’s a scalar and independent of direction
I have to be careful not hitting VNE on cruise with throttle way back to 60% power in ground effect in Turbulents D31 at 1ft over sea water when entering on high speed side of drag curve and zero AOA but they barely make 80kts at 300ft with 100% power, I am sure some interesting stuff happens near the ground 
LeSving wrote:
Energy is simply the sum of potential and kinetic energy. It’s a scalar and independent of direction.
Thanks; I see that you are correct.
Ibra wrote:
I have to be careful not hitting VNE on cruise with throttle way back to 60% power in ground effect in Turbulents D31 at 1ft over sea water when entering on high speed side of drag curve and zero AOA but they barely make 80kts at 300ft with 100% power, I am sure some interesting stuff happens near the ground
What engine is that with? I have the 1600 and get closer to 100 at full power and 2000 feet. On a forward and back course – never tried a proper triangle yet.
It’s the 1600cc but the prop is designed for climbs, it gets 85-90 on some days but 80 is good planning number, however, when cruising in ground effect it does start clocking more kts near 102kts even when you throttle it way back, so something going on for sure?
It’s wrong to assume energy is conserved for aircrafts in form of kenitic & potential when engine is dead as drag dissipate speed & height, the lowest drag paths tend to be associated with free fall trajectories or zero G flying, otherwise with stick pulled way back on full yaw, you tend to lose energy quicker as the whole wing acts as aerodynamic break
What’s your climb rate with that prop? I’m presuming you chose it for short take-offs from grass?
Ibra wrote:
It’s wrong to assume energy is conserved for aircrafts in form of kenitic & potential when engine is dead as drag dissipate speed & height, the lowest drag paths tend to be associated with free fall trajectories or zero G flying
In other words, if your engine fails in a climb you can cover ground in a ballistic trajectory without losing much energy, then find yourself (for the sake of argument) in a stable descent one or two hundred yards further along than if your engine had simply failed when you were in a stable descent.
So you have the same amount of energy in both configurations (stable climb; stable descent – assuming equal speed and altitude) but it still makes a difference whether you are climbing or descending when the engine failure happens.
Ibra wrote:
I am sure some interesting stuff happens near the ground
That something is called ground effect
I think there are wind & temperature gradients as well to be more exhaustive
