Compression with no thrust?

[TweetyBird]

Someone needs to explain the law a physics that allows a plane with no thrust to continue to compress. Ever hear of buoyancy?
Pressures will do everything in their power to equalize. With the lack of thrust, compressing planes should slow down almost immediately with no thrust. What is up with this missile to the earth crap and 20 seconds of compression with no thrust?
PLEASE someone post that equation. There is only so much speed gravity will give per pound/mass, and then air displacement and drag comes into the picture.
Either the gravity is WAY too strong or the compression algorithm is - well - gamey.
I gota run more test, but I find it ridiculous that a plane with no thrust at 20k will slow down faster than a plane with no thrust in dense 3k air.

Edit - hope this wasn't shrill
but some things in the FM seem a little off

[United]

https://ewhdbks.mugu.navy.mil/freefall.htm

if the terminal velocity of the aircraft is faster than the compression speed, and you had the alt to fall that long, then youre going to compress no matter what throttle settings you have.

[TweetyBird]

Thanks for the link. I have to go over it more closely, but I think it even states it ignores drag in its calculations. With bombs, that might no be a problem, but an aircraft is going to have a lot more drag.

I have in mind a simple test. Take a plane up to 30k, kill engine, point nose straight down and record the speed at diff alts. Then do the same with different flap settings. That should show the influence of drag.

[Ghosth]

Unless you start with full flaps and stay well away from the vertical. You will build up speed, the flaps will autoretract & You'll end up back in compression anyway.

Exception of course those planes (Not the p38) that had true dive flaps. ie SBD, ju87 etc.

[TweetyBird]

>>Unless you start with full flaps and stay well away from the vertical. You will build up speed, the flaps will autoretract & You'll end up back in compression anyway.
<<

Oops - didn't think about that - ty. Maybe drop tank and no drop tank? That big keg handing below should cause drag. And rocket rails...

Have to burn out the dt and shoot the rockets to make sure I'm getting mostly drag and little weight.

[Tails]

Originally posted by TweetyBird
>>Unless you start with full flaps and stay well away from the vertical. You will build up speed, the flaps will autoretract & You'll end up back in compression anyway.
<<

Oops - didn't think about that - ty. Maybe drop tank and no drop tank? That big keg handing below should cause drag. And rocket rails...

Have to burn out the dt and shoot the rockets to make sure I'm getting mostly drag and little weight.

Weight doesnt affect the ~9ft/s/s accelration that is 1 G. I believe Newton proved this some ungodly number of years ago. (I dont mean this with any kind of attitude...just trying to save you some headache)

[Flit]

Originally posted by Tails
Weight doesnt affect the ~9ft/s/s accelration that is 1 G. I believe Newton proved this some ungodly number of years ago. (I dont mean this with any kind of attitude...just trying to save you some headache)

 ya mean 32 ft/s/s ?
 ah you put the number for meters instead of feet
it,s  more like 9.803 m/s squared

[Tails]

Sorry. I was low on caffine when I wrote that, but yeah. Weight doesnt affect acceleration by gravity.

[TweetyBird]

>>Weight doesnt affect the ~9ft/s/s accelration that is 1 G. I believe Newton proved this some ungodly number of years ago. (I dont mean this with any kind of attitude...just trying to save you some headache)
<<

oops again. Good thing - fat skydivers would always land first
Old science fair project - 2 identical containers - fill one with sand - drop both at the same time - which hits ground first..

Thanks for the correction

[Tails]

An Apollo video also comes to mind, where they dropped a hammer and an eagle's feather from the same height on the moon. Pretty neat the theories you can prove without a pesky atmosphere to mess things up.

[Flit]

Tweety, ya need to change ~9ft /s/s to~9m/s/s

[TalonX]

Acceleration on earth is essentially a constant.. (It does vary by altitude, but hardly worth worrying over)

The values are:

32 ft/sec/sec  Or stated 32 ft/second squared

This is the same value as the metric equivalent:

9.8 meters/sec/sec

All this means is that a falling body (ABSENT DRAG) will increase speed at a rate of 32 feet per second for every second it falls....so after two seconds, it will be moving 64 feet per second.   After 3 seconds, it will be moving 96 feet per second, and so on....  Clear?

Now, drag reduces this value..... and terminal velocity is when the drag exactly matches the forces of gravity....hence no more acceleration.   A falling body has increasing drag until drag = gravity...........

Hard to imagine a terminal velocity greater than the compression speed of many airplanes from WW2.......................

[SlapShot]

I am not an aero engineer but this is how I see it ...

Once a plane enters compression, drag, I believe is not in the equation anymore cause you have already accelerated to the compression point. Its not how fast you are going, but at what point do you lose control to change your angle to stop the compressed state.

Once into compression, there is nothing that will slow the airplane down or change its angle outside of the normal control surfaces.

Some planes, as mentioned, had special control surfaces (outside of ailerons, flaps, and elevators) that helped break the flow of air over the wing and slow the plane down or kept the plane slow to the point where the normal control surfaces worked.

So if the speed at which compression starts is greater than the speed at which the control surfaces no longer work, your plane is now trimmed for that angle and you will continue your downward flight path until terra firms interrupts it.

I would assume that the steeper the angle at which compression begins, the harder it would be to maybe naturally pull out of a compressed situation.

If your control surfaces are only good up till 100 mph and you enter a dive that brings you to 150 mph, your screwed. If you cannot somehow slow the plane back down to 100 mph or below, at the angle that you are currently diving, you will lawn dart.

That is how I view it ... I could be all wet.

[TalonX]

I was addressing entering compression through "falling" straight down...I doubted you could easily get going fast enough to enter compression simply by pointing the nose down.

Once you are in compression, the forces are many and varied....I am far less expert on that topic other than to say it used to cause a sensation of locked controls, etc........so rigidly did these forces hold the airplane.

I read of pilots standing on the stick to force a negative G pull out from compression.

In any case, once in, getting out is hard.

[TweetyBird]

>>Hard to imagine a terminal velocity greater than the compression speed of many airplanes from WW2.......................
<<

Surely there must be a list somewhere of the terminal velocities of WW2 planes - gonna search google.

Also, I wanted to test the air in AH2 as it seems its the same density at 30k as 4k (at least in some respects). Where you do have to stay faster to perform certain maneuvers, I notice if you have a plane going 360 mph true air speed at 30k and kill the engine, it takes the exact same time to slow down to 150 as it does at 4k. Now that doesn't make sense does it?