[drgondog]

Originally Posted by Holtzauge

Of course exhaust thrust is a real force. Have either I or Harri said otherwize?

No, you asked me to explain the calculation and I did. Next question?

The exhaust thrust is added to the thrust formula according Harri's post which is SPEED dependant and should not just be added to the thrust available at rest as you claim.

Exhaust thrust is Not dependent on speed. Net Thrust (True Thrust - propeller drag) is dependent on speed

I find Harri's way of calculating dividing the problem up in thrust and drag parts perfectly understandable and have seen many calculations done the same way in both technical litterature and technical papers before.

And yet you still don't understand why a ship may have Max Thrust at zero speed on the runway with chocks in place, not can you explain the physics of acceleration from zero to Vmax as it relates to Net Thrust.

So what does that say about your understanding of a free body force diagram?

You now make a mix above of thrust, exhaust thrust, propeller drag, induced drag and parasite drag in the same sentence with no clear indications how they relate. How do we take these into account by your method? Please, show us mathematically how you intend to calculate this in a practical manner.

I will after you answer each question I posed to ensure you are acquainted with F=ma. In particular I would like to see you demonstrate your knowledge for level flight and a vertical dive (to keep you from wandering into Trigonometry).


Obviously my analogy missed the mark in helping you understand all the forces acting on the airframe system

Now on what grounds is it reasonable to assume that "Net Trust does indeed cancel out the Prop drag and exhaust thrust"? Sources please? What do you mean by "close"? Close to what and in which context?

When comparing the System A to System B - different only by weight but same in all other respects, the exhaust Thrust is the same between the two ships and need not be factored in calculating the differences in Velocity at different Gross weights.

"Close" means that the difference in Prop Drag in System A from the Prop Drag in System B is to the inverse ( 1/2*MV1>>2 - 1/2*MV2>>2) which represents the change in mass flow rate of the stream tube. V1 = higher speed, V2 = lower speed due to the extra weight... and I have to do some checking on this relationship - this is strictly from memory and I could be wrong.

Having said that - please offer your own explanation for the difference?

Holtzauge - you have a somewhat poisonous debating style.

You have already called into question my academic credentials, you ague formulae without demonstrating context knowledge of when and why these formulae work (and don't work).. you keep challenging my questions with sarcasm - but don't answer the questions.

One more time - why doesn't the THp equation yield Total Thrust in the context of Velocity, and why doesn't it work at zero velocity.

Given that it doesn't work at zero velocity, what do YOU use to yield the Thrust/Total Thrust/Total Force (all interchangeable) at max power on the ground, chocks or brakes in place? There IS a Force at work but no acceleration as it is in equilibrium. Demonstrate your knowledge of Physics.

In other words, given your vast knowledge of Aero Engineering, based on the easy to understand explanations by Harri, could you calculate take off run, distance to clear`50 ft obstacle and what would your velocity be over the 50 ft obstacle if;
a.) you knew Bhp, or in case of jet - static thrust
b.) wing Aspect ratio,
c.) gross weight,
d.) CL and CDp,
e.) wing area.

Before you start what do you need to know about Cdp that we have not yet discussed?

After take off, what is the Total thrust vesus the Net Thrust over the 50 foot obstacle?

If you can answer these questions I will know you know the difference between Net Thrust and MaxThrust available - (for each case use the same power setting to simplify).

Out of curiosity hat is your academic and industry background to denigrate mine, or Crumpp's?