Quote:
Originally Posted by Crumpp
Sure there is blackberry, you just have not reached it yet.
Your equilibrium point velocity is found by converting the Vmax TAS to EAS. We are going to change altitude and we don't have to constantly mess with density effects.
Now we can use the relationship our parasitic drag component to find our new velocity. You already know the Cdo of the design.
So using the relationship of parasitic drag force and velocity:
Dp2 = Dp1(V2/V1)^2
Re-arrange to solve for velocity:
At 100 KEAS our airplane produces 5000 lbs of parasitic drag. At what velocity will it produce 10000lbs of parasitic drag?
100 KEAS * SQRT(10000 / 5000) = 141 KEAS
If we suddenly gained 5000lbs of thrust (5000lbs plus 5000 lbs) our new equilbrium velocity would be 141 KEAS.
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When P51 at Vmax=700km/h, what's the air drag force? 1500lbs?
When P51 dive in 45 angle with full throttle, what's the next equilibrium piont speed?
1200km/h!
When Bf109K dive in 45 angle with full throttle, what's the next equilibrium piont speed?
1100km/h!
When P47D dive in 45 angle with full throttle, what's the next equilibrium piont speed?
1300km/h!
When TempestMKV dive in 45 angle with full throttle, what's the next equilibrium piont speed?
1200km/h!
When Dora dive in 45 angle with full throttle, what's the next equilibrium piont speed?
1100km/h!
Since those planes never reach so called the next equilibrium piont,
the equilibrium is totally useless in analysis of 45 degree dive acceleration.Since you have to pull your aircraft out of 45 degree angle
far before reaching the equilirium point, you are always accelerating in dive, you always have excess thrust during dive, higher efficiency propeller always provides higher thrust.
The sum of gravity and engine thrust is always bigger than air drag force.
I post the picture again, do you understand me?
q.jpg