Nonprecision Approaches

A. Dialogue

 

Student: Instructor:     Student:   Instructor:     Student: Instructor:   Student: Instructor: Student: Instructor: Student: Instructor: Student: Instructor:

Can an approach be made with any navigational aid? Usually. But an approach that doesn't use a glide slope has higher minimums. A nonprecision approach can utilize various navigational aids, such as a localizer, VOR, DME, or an automatic direction finder (ADF). I know DME provides information to make accurate calculations of descent and position points. But what if the plane isn't equipped with DME? Then a pilot makes use of marker beacons, radials, and bearings from other navigational facilities. If none of these aids are available, the approach is timed. The runway environment must be visible at the missed approach point (MAP). If it isn't, a missed approach procedure must be executed. You mean that you time the progress from the final approach fix (FAF) to determine the MAP? That's right. From the FAF you descend to the minimum descent altitude (MDA) and maintain the MDA until you reach the MAP. This is how all instrument approaches were made years ago. Is a VOR as accurate as a localizer? No. That's one reason why a VOR approach has higher minimums than a localizer approach. What about an ADF? An ADF picks up the signal from a nondirectional radio beacon (NDB). Can an accurate approach be made using an ADF? Yes, but it can be less reliable during precipitation or weather disturbances. Then the ADF doesn't register on the CDI the way a localizer or VOR does. Correct. It uses a separate instrument with a rotating needle. The ADF is a good orientation instrument. In some countries VORs aren't common, and the ADFs still guide pilots.

 

 

B. Terminology Practice

 

automatic direction finder (ADF):a navigational radio that senses signals and indicates the direction of low-frequency beacons

Can an ADF locate a lost aircraft?

The bearing to the ADF station is 321 degrees.

An ADF picks up the signal from an NDB.

bearing:the position of an aircraft in relation to a point on a compass

The bearing is 133 degrees to our destination.

Will this bearing take us to the airport?

We're drifting south of our original bearing.

final approach:a flight path in the direction of a landing along the extended runway centerline

When do we begin the final approach?

The time to the final approach is four minutes.

Put the flaps down for the final approach.

final approach fix (FAF):the position at which the final approach is executed

The approach plate says to cross the FAF at 3,400 feet.

We must time the approach from the FAF.

What was the FAF of that aircraft?

minimum descent altitude (MDA):the lowest altitude allowed on the final portion of a nonprecision approach

What's the MDA for that airport?

An MDA applies only to nonprecision approaches.

The altitude of an MDA is measured in feet above sea level?

missed approach point (MAP):the point at which the pilot decides whether to complete an approach or execute a missed approach procedure

Have we reached the MAP yet?

As we passed the MAP, the runway environment wasn't visible.

The time to the MAP is two minutes and three seconds.

missed approach procedure:the procedure to be followed if, after an ILS approach, a landing is not effected and occurring properly

A missed approach procedure was made because there was poor visibility.

We're executing a missed approach procedure.

A sudden snow shower made a missed approach procedure necessary.

nondirectional radio beacon (NDB):a low-frequency transmitter that sends navigational signals

Have we been cleared to fly direct to the NDB?

The FAF begins when the plane passes over the NDB.

The ADF picks up low-frequency signals transmitted by the NDB.

nonprecision approach:an approved instrument approach in which no electronic glide path is provided

Do any nonprecision approaches provide a glide slope?

Nonprecision approaches have higher minimums than precision approaches.

An approach utilizing a localizer is a nonprecision approach.

radial:a magnetic course extending from a VOR station

Use the airway at the 245 degree radial.

Which radial will we follow?

Fly the 345 degree radial to intercept the approach course.

 

 

C. Check-Up

 

Fill in the blanks with the proper terms from the list.

ADF Bearing final approach FAF MAP

MDA missed approach procedure NDB nonprecision approach radial

 

1. The ___________ is the flight path in the direction of landing along the

extended runway centerline.

2. A pilot decides whether to complete an approach or execute a missed approach procedure at the ___________.

3. An ___________ is a low-frequency transmitter that sends navigational signals.

4. The ___________ is the lowest altitude allowed on the final portion of a nonprecision approach.

5. When a pilot can't see the runway environment at the MAP, a ___________ is executed.

6. An ___________ is a navigational radio that receives signals from NDBs.

7. A ___________ is an instrument approach that doesn't make use of a glide slope.

8. The position at which the final approach is executed is the ___________.

9. A ___________ is a magnetic course extending from a VOR station.

10. The position of an airplane in relation to a point on a compass is its ___________.