Angle of Attack in a Dive

Well, sooner or later we all have to descend from our beloved airspace. We can get down a variety of ways. We can glide, dive, power off or idle slow flight or descent with power.

Several posts ago I presented a problem on a descent through cloud cover that forced you to make several choices on flight attitudes you could use. 

Some solutions, depending on your training, experience, qualifications of your aircraft, etc. could save your life.

I recall conversations, during a good cup of Joe, talking flying, that a choice may involve putting a plane into a spin. Someone else, with instrument experience thought a normal descent on instruments was his choice.  Another participant in our "hanger talk" thought, since he was intimately aware of his "feel" for his plane, would choose the slow flight method at reduced power.

The dive may be a quick way to penetrate the cloud cover but recovery was questionable if the ceiling was lower than anticipated. You get the idea! 

How does a "dive" work with our discussion of pushing air about to create lift, our possibly, no lift at all?

We don't need  power. Gravity does the job. Obviously, the attitude of the plane is extremely steep. Horizontal forward motion of the plane, separate from the attitude of the very steep nose down attitude of the dive, may be present and, in a certain case, non-existent.

Another way to look at a dive is the similarity to normal cruising flight with a very low angle of attack and increasing speed as you descend. A dive does have its structural limitations.

Since you do have a limited angle of attack, in a vertical dive , the lift generated pushes the aircraft horizontally along the original flight path of the plane. If you thought the dive would take you down to an object directly under the plane ,when you started the dive, it wouldn't be there. It would be well behind you, depending on the altitude you started the dive. Higher the altitude the greater the distance traveled horizontally.

If you really want to perform a military descent to a target directly below you, to make your plane very hard to shoot down, you have to perform a dive where no lift from the wings occurs.

In this dive you actually put the plane on its back past vertical. Look at a war movie where the plane seems to roll over on its back as it descends. Aviators are beginning a "past vertical" dive to a target directly below. The airplane is actually meeting the air at  the "no-lift" angle of attack. Your airplane is not creating lift it has only drag.

In this attitude the airplane can achieve its highest speed and becomes vulnerable to structural failure. It does move forward horizontally.

Civilian planes should not even think about a "past vertical" dive. You have a placard in you plane, colored red, that gives you a "Never Exceed MPH."  

All sorts of things can happen in dives. Turbulence can cause structural failure. Rapid pull out from a dive can cause structural failure. You may experience a "red out" where blood rushes to your head like in a hyperbolic arc flight path. You may put yourself into a "blackout" flight path like a normal pull out from a dive but with significant G-forces to allow the blood to rush out of your head and cause you to lose consciousness.

None of these are good for your health. It is good to know how you can place the plane into the attitude where these can happen. Just don't do them in a civilian plane.