Approach Procedures — Page 179, Lesson 257

Let's pick this up right where the approach procedure leaves off. We've just talked about the final segment and verifying glide path information. Now I want to walk you through a few critical concepts that govern how you actually fly these approaches. First, let's talk about the Constant Approach Slope, which is also called a Stabilized Approach. This is a procedure developed primarily to avoid wake turbulence separation, but it also helps with economy and noise abatement. Here's the core idea: the procedure requires the aircraft to depart from the IAF — that's the Initial Approach Fix — and descend at a constant rate throughout the entire procedure. Why does a constant descent help with wake turbulence? Wake turbulence separation is only applicable between approaching aircraft when the second aircraft is at the same altitude as, or within 1000 feet below, the preceding aircraft. So if we ensure the subsequent aircraft is always above the preceding aircraft, there's no requirement for wake turbulence separation at all. That's the clever part — by keeping a constant descent, you naturally stay above the aircraft ahead of you. Now, how do we control that rate of descent? Through aircraft attitude. By controlling attitude rather than making power changes, we reduce noise. And by setting a constant power, we achieve economy in fuel usage. So you have three benefits bundled together: wake turbulence avoidance, noise reduction, and fuel economy. Next, let's look at the Missed Approach. This is what happens when you don't obtain the necessary visual criteria at the DA/H or MDA/H — that's Decision Altitude/Height or Minimum Descent Altitude/Height. The final part of an instrument procedure permits a return to the IAF for another attempt, or to establish the aircraft on a departure profile to go to another aerodrome — your alternate. So the missed approach is your escape route when you can't complete the landing. Now let's move to a fundamental safety concept: Obstacle Clearance Altitude/Height, abbreviated OCA/H. During the development stage of designing a procedure, the OCA/H is determined by the authority of the state through survey. This is the altitude or height at or above which an aircraft must be flown to avoid the dominant obstacle. It consists of the height of the obstacle plus the minimum obstacle clearance allowance, which we call the MOC. This information gets published so you know exactly what altitude protects you from terrain and obstacles. Let me show you how these fit together in the approach geometry. Here's a figure that illustrates the IAF to IF transition for a precision approach. And here's the same transition for a non-precision approach. So to tie it together: the stabilized approach keeps you on a constant slope for wake turbulence, noise, and economy. The missed approach is your contingency when visual criteria aren't met. And the OCA/H is your guaranteed obstacle clearance floor — the altitude you must not go below unless you have the runway in sight. These three concepts work together to keep every approach safe, efficient, and within the published limits.