Put the airplane into a dive, then pull up to level off. The VSI will still be showing a descent long after you need to stop pulling. Ditto for a climb and push to level. However, in each case, the altimeter will stop moving right when you need to stop pulling/pushing. This becomes particularly important in partial panel unusual attitude recoveries, in which VSI-oriented pilots will give you a real roller-coaster ride before stabilizing.
Great! I hoped to get a discussion going on the VSI.
Ron, I quoted your demonstration in order to compare to mine, but first, some background:
I, too, only used the vsi for approximate rates of descent on a non-precision approach. That was the way I was taught and, like everybody else, I could see the vsi had to much lag to actually use as a pitch instrument.
Then I learned to fly helicopter instruments. Unlike an airplane, the helicopter attitude indicator is not a reliable indication of the attitude of the wing, so the altimeter, and vsi, become primary pitch instruments.
The reason I entered this discussion was the remark about teaching precise, delicate control touch on the elevator for altitude (pitch) control.
I have found that we all can learn the precise control necessary to keep the altimeter needle within the zero by using the vsi needle to do that. It is a skill, like learning to land the airplane. Landing takes a finely developed control touch on the elevator to get the greasers.
Take the same attitude towards learning to center and control the vsi needle, and anybody that can land an airplane can also learn to center the vsi.
Let's look back at your demo. I use this following demo to start the process of learning how to interpret and respond to the needle movement:
First, the needle moves up or down when the nose goes up or down. Forget about rate, this is trend.
Second, the needle stops moving when the nose is level with the horizon.
To demonstrate:
Start in level flight with the altimeter needle in the zero at the top, and at a comfortable approach speed. Look outside at the horizon, and note where the nose is, start a pull-up to get the needle moving up, note how it starts up
almost immediately. You're pitching up about 10 to 15 degrees, enough to get the vsi needle moving up thru 500 fpm going towards 1000', then push the yoke forward while rapidly cross-checking outside for the horizon and the needle movement. The nose will be coming level with the horizon at the exact moment that the needle stops moving. This is the moment you stop elevator input. Watch the needle. When it moves up, lightly push forward until the upward movement stops, and
freeze the elevator there. The needle laggingly returns to zero.
Go in the opposite direction. from level flight push forward until the vsi goes thru 500 towards 1000, pull back until the needle freezes for a moment, and that's where you freeze your elevator input.
Practice elevator movements, watching the needle movement, and stopping the needle movement with opposite elevator movement until the needle stops, then stop your movement.
Continuing to move the elevator until the needle starts moving in the opposite direction is the cause of over-controlling.
That's how we do the elevator when landing, except we're using the outside plane of the runway to make continuously small adjustments to the elevator to get a 'near-zero' rate of descent. Learning to control the vsi just takes the same amount of determination that we spend on many other areas.
This technique I've used for many years, since learning helicopter instruments, but it has recently shown up in the FAA Instrument Flying Handbook, in the chapter on helicopter instruments.
But that doesn't mean you can't use the skill in an airplane.
It is great for partial panel. In the typical 6-pack, the vsi and heading indicator are side-by-side. I use, and teach, the basic cross-check between heading and vsi for good pitch and roll control, or straight and level. In cruise flight, the airspeed is steady, so I really only have to concentrate on 2 instruments, HI and VSI. ZZZZZ
