So to any pilots out there... How does DA affect flight? Thinker air requires more power to stay at same altitude, less DA requires less power?
Same as bullet in flight? Maybe thinner air reduces drag on air craft, thinker air makes more drag? If so...I think I'm correct on this... How do bullet markers come up with a BC?
Thinking about all that affects drag(drag=BC) Then BC has to be done in a controlled environment. If not then published BC is (maybe) not correct. If any# change, BC,fps, attitude, DA, then the hold changes. It's math, it doesnt lie (most of the time). Strelok is only as good as the #we put into it.
Real question is how do bullet makers come up with a BC? All other thing change, I get that. But BC is a number, that bullet markers say is right. If I change BC and not DA then hold comes out right. We,are taking a # and not changing it (BC) and believe it is correct. How is that measured? In a controlled environment ? Or at a place that difference from place to place?
Wow...........there's a lot to address here.
First of all, B.C. is NOT the same as drag. It's called a Ballistic Coefficient so that you can predict the drag, and therefore predict where your bullet will hit on the target if you factor in things like range, muzzle velocity, etc. The "etc." includes atmospheric variables.
To convince yourself that B.C. is not drag think about this. A bullet sitting on your loading desk has zero drag. Why? Because it's not moving; however, it has the same BC that it does when it's halfway to the target when you shoot your next match.
When people calculate B.C. they typically measure the actual bullet performance and then work backwards using the actual atmospheric conditions under which they did their testing to arrive at a B.C. which they then publish. Typically they don't test bullets or aircraft in a standard atmosphere. They test in the atmosphere at the time and location they have at the moment, and then correct the results to some standard, usually to a standard temperature and pressure. By correcting their measured results to reflect the altitude, temperature, and humidly during the test, they come up with a standardized B.C. so that you can find the solution you're looking by working the other way. That is to say, you start with their standardized B.C., take into account YOUR weather conditions along with MV, etc. and then you can predict where your bullet will land.
Density altitude is a favorite for pilots because it gives a number in feet above sea level rather than some other unit like slugs per cubic foot. Few people have a feel for what a slug per cubic foot feels like.
If you are at an airport 2000 feet above sea level you can expect your take off performance to be less than you would get at an airport at sea level. But if the weather is hot, your density altitude might be 2800 feet even though your "real" altitude is only 2000 feet, meaning that your take off performance will suffer even more. Of course there are performance charts pilots use to calculate their take off (or landing) performance and Density Altitude is usually one of the primary factors.
Density Altitude is normally easy for pilots to get since they most often do their work at an airport and airports are linked to weather observations and forecasts. We shooters are not so lucky, but we can often find our altitude and temperature which are the main factors. Humidity has less effect on D.A. but it should be counted if you can find out the value. Various ballistics calculators handle atmospheric conditions differently.
Contrary to your intuition, moist air is "thinner" than dry air. It may feel "heavy" to you if you're out in the swamp chasing alligators, but in fact moist air is less dense.
Now when it comes to the power required to fly an airplane in "thick" or "thin" air, the answer is a bit complicated to cover in this thread. Even though my formal education is in the field of Aerodynamics, I have no intention to turn this thread into an aerodynamics course. But I will say this: Generally speaking, lower density altitude (thicker air) requires LESS power to fly; just the opposite from your guess.
