Wing Loading & Stall Speed Question

[drgondog]

Download your own copy: Aerodynamics for Naval Aviators : Free Download, Borrow, and Streaming : Internet Archive

Personally, I view this as a very good Intro to Aerodynamics. It will convey all that is required for an FAA exam and, as the Preface states, the primary purpose is to convey the basics of aerodynamics to the application of flight safety and exams such as FAA.

That said, it does not provide the essential knowledge of drag contributions and variations with altitude, TAS, nor the contrubtions of momentum recovery of such features of car/cooling intake, or the losses due to airframe components immersed in a prop stream/vortex. Not enough to do Perfomance Analysis/Comparisons.

Also it was (been awhile) NOT clear that CDmin - expressed as 'zero lift' drag DOES vary as a f(Reynolds Number).

Nor does it explain that Flat Plate Drag, while variable with dynamic pressure, is also dependent on varying contributions affecting Form(profile) Drag imbedded in the total Parasite Drag equations;

For example, there is a contribution due to change of Lift Component (empirically developed in wind tunnel test) at given TAS, for increasing altitude - as angle of attack must be increased to maintain required Lift for level flight - not accounted for in the Induced Drag component. What Is available from the Flat Plate drag equation is the real Drag force opposing the Thrust contributors (Prop, exhaust jet, etc) for equilibrium. Basically, it is everything in the Parasite/Form Drag components - corrected for compressible flow - plus Induced Drag force component of Total drag.

BUT the CDmin that started the discussion has changed signifiantly from the published wing tunnel value - and it is but one component in CDPtotal.

The most important omission, in interests of 'KISS for pilots' is that 'picking a CDmin off the charts, is usually based on a low speed wind tunnel test - but is valid ONLY as an expressed f(RN), said expression determined in wind tunel testing.

In other words, the gamer developer or performance analyst attmpting to Predict performance due to a configuation or power change, needs a lot more to fully understand the resulting possibe top speed or rate of climb.

 

[MIflyer]

And then, for something almost completely different, there is supersonic aerodynamics.

 

[drgondog]

And then, for something almost completely different, there is supersonic aerodynamics.

Amen
particularly on propulsion issues.

 

[pbehn]

If you introduce too much reality into a game, the gamer spends six hours on his computer, usually seeing and doing nothing of consequence.

 

[Greg Boeser]

If you introduce too much reality into a game, the gamer spends six hours on his computer, usually seeing and doing nothing of consequence.

And that is different, how?

 

[Simon Thomas]

Amen
particularly on propulsion issues.

This is 1000% true. I came across the attached paper on the YF-12A the other day, and I found this part that completely floored me:

 

[pbehn]

And that is different, how?

That is the historical reality, it doesnt sell games though.

 

[MIflyer]

If you introduce too much reality into a game, the gamer spends six hours on his computer, usually seeing and doing nothing of consequence.

You've just described a good portion of most Aerospace engineering careers.

This is 1000% true. I came across the attached paper on the YF-12A the other day, and I found this part that completely floored me:

Yep, 17%. I read that over 40 years ago.
Note the importance of the shock inlet cone. I did so many shock calculations in college. And note that the shock cone is actually a double cone, with two different angles, and they are actually angled inwards so the tips are in line with the forward chine.
A double shock cone also was used on the NF-104 with the rocket motor in the tail.
Ever notice how the Mig-21 was the only fighter with a big shock cone sticking out of the intake? Mach 2 fighters like the F-4 and F-105 did not have that. The cone indicates the engine wasn't good enough.

 

[SaparotRob]

I thought it was because it looked cool.

 

[Daggerr]

This is 1000% true. I came across the attached paper on the YF-12A the other day, and I found this part that completely floored me:
View attachment 733206

"Note that the inlet alone provides 70% of the thrust, the spike is 14%, and the ejector pushes with 27% to make up the total thrust for the aircraft."

That is not quite right. The spike does not provide 14 % of the thrust, but provides a drag equal to 14 % of the thrust.

The inlet 0-2 provides 56 % of the thrust (not 70 but 70 - 14), the engine plus ejector provides 44 % (= 17 + 27).