My first flight instructor told me to ignore the vertical speedometer. He said there was a lot of delay and it wasn't very helpful. It only took me 25 years to realize how wrong he was, especially when I was soaring.

We have flight instruments that tell us how fast we're going, which way we're going, and how high we are. But none of them tell us our fate, except for the vertical speedometer. Shows what the altimeter will say in one minute.

Here's an example: If I'm trying to level flight at 3000 feet and see my vertical speedometer climbing 200 feet per minute, I need to do something or I'll be at 3100 feet in 30 seconds. If you ignore the vertical speedometer for a minute, I'll be 200 feet from my altitude. So the vertical speedometer predicts my future altitude. If I fix the vertical speed problem as soon as it appears on the device, I will hardly leave my altitude and I certainly won't have to fix it later.

Now let's talk about how the vertical speedometer predicts the future on the glide track.

Everyone knows that the descent rate required to maintain the slide slope depends on the ground speed. For most of us general aviation pilots, this is about 400 to 500 FPM.

So it's the simple fact that if the vertical speedometer descends to 1000 feet per minute, we'll be below the glide path in a matter of seconds. Similarly, if we see vertical velocity below 200 feet per minute, it's an easy guess that we'll soon be on the glide path. The fortune teller warns us before we deviate from the glide path that we must correct the descent rate or face the consequences.

Many pilots spend a lot of time watching the glide indicator. While observing the approaching approaches of the pilots, I often watched the vertical velocity needle go to zero as it flew slightly upwards. At that moment the slip needle is still centered. And if that's all the pilot is paying attention to, he's happy, but it's clear he'll be unhappy in a few seconds because he'll soon be above the glide slope.