Precision Approaches

A. Dialogue

 

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Are you familiar with instrument approaches? I think so. An instrument approach is a series of predetermined maneuvers that lead an aircraft to the landing runway. The approach is carefully designed and approved. Two factors that are considered are the performance of the aircraft and safe terrain clearance. Most approaches are made using an electronic guidance system. I'm very familiar with the ILS approach. It involves a high degree of precision That's right. In addition to electronic lateral guidance, an ILS also offers electronic glide path control. Then an ILS has electronic guidance equipment on the runway. Yes, it does. These transmitters send special VHF signals toward approaching aircraft. They're displayed to the pilot on a course deviation indicator (CDI). The vertical needle indicates lateral course deviation from the localizer. The needle of the glide slope indicates whether an aircraft is above or below the glide path. How many marker beacons are there on the runway? Usually two or three. How are they differentiated? Each beacon is identified by Morse code and a colored light. The outer marker beacon is near or at the point of glide slope interception, several miles from the runway. Sometimes the outer marker beacon is equipped with a low frequency transmitter, called a compass locator. An aircraft can home directly to the outer marker with a low-frequency receiver and course needle. What about the other marker beacons? The middle marker beacon is about a half mile from the runway's end and its signal is transmitted to a plane at the decision height. And the last beacon must be the inner marker beacon. Right. It's located between the middle marker beacon and the end of the runway. Inner marker beacons are installed for approaches with specially approved low-descent minimums, which are 100 feet or less above the runway. Minimums are noted on the appropriate approach plate, correct? Yes. At the decision height the pilot must see the runway or its environment. Are there different minimums for various ILS approaches? Yes. There are several categories. The most common has minimums of a 200-foot ceiling and a half-mile visibility. An ILS using an automatic landing offers minimums of no ceiling and a visibility of a few hundred feet. Do you mean that the automatic pilot lands the aircraft? That's right. The most difficult part of this landing is finding the taxi ways and the terminal in such low visibility. Is a microwave landing system (MLS) similar to an ILS? The display and guidance are like those in an ILS. Microwave signals offer more accuracy and flexibility to the precision approach.

 

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B. Terminology Practice

automatic pilot:a device that flies an aircraft automatically

The automatic pilot sometimes lands an aircraft when there is a low ceiling and minimal visibility.

Is this aircraft equipped with an automatic pilot?

I've turned on the automatic pilot.

compass locator:a low-frequency transmitter that is situated at a marker beacon site

Can the compass locator be used as a navigational device?

Proceed direct to the compass locator.

Fly to the compass locator and intercept the localizer.

course deviation indicator (CDI):an aircraft instrument that provides lateral guidance

The vertical needle of the CDI indicates that we're on the localizer path.

The CDI shows that we're above the glide slope.

When did the CDI malfunction?

decision height:the height at which a decision is made to either continue or change an approach

The decision height was 200 feet above the runway.

The runway wasn't visible at the decision height.

What was the decision height for that approach?

glide path:an aircraft's descent path, which is indicated by a radio beam

You're slightly above the glide path.

Are we above or below the glide path?

It's dangerous to fly below the glide path.

glide slope:an electronic signal that provides vertical guidance

It's illegal to fly below the glide slope.

We should intercept the glide slope at 2,500 feet.

The glide slope passes over the outer marker at 1,900 feet.

home:to follow the path of radio waves to the point of transmission

The aircraft homed directly to the outer marker.

Have you homed in on the transmitter?

The marker beacon is a homing device.

instrument approach:an approach to an airport by an aircraft, using instruments and radio guidance

An instrument approach makes it possible to land during low visibility.

We'll make an instrument approach to Orly Airport.

Is an instrument approach necessary?

marker beacon:a device that identifies a location by means of a transmitted signal

Have we already passed the outer marker beacon?

The marker beacon is located along the localizer center line.

We checked the altimeter as we passed the outer marker beacon.

microwave:a short electromagnetic wave

Microwaves range between 1 and 100 centimeters in length.

Radar operates using microwaves.

Are microwaves ever used with an ILS?

microwave landing system (MLS):an ILS that operates in the microwave frequencies

An MLS provides both lateral and vertical guidance.

The MLS is more diverse than other ILSs.

Do MLSs require special aircraft receivers?

minimums:weather conditions requirements established for a particular operation

An ILS using an automatic landing offers minimums of no ceiling and a visibility of a few hundred feet.

If visibility is below minimums, the runway environment won't be visible at the decision height.

What are the minimums for altitude and visibility?

Morse code:a code in which combinations of dots and dashes or longand short signals are used to represent characters

Marker beacons are identified by Morse code.

The Morse code was invented by Samuel F.B. Morse.

Have you memorized the Morse code?

precision approach:a standard instrument-approach procedure in which an electronic glide slope is provided

An ILS is a precision approach.

With the slide slope inoperative, we can't make a precision approach.

Will you describe the equipment necessary for a precision approach?

 

C. Morse Code

 

A	. _	N	_.		. _ _ _ _
B	_...	O	_ _ _		.. _ _ _
C	_. _.	P	. _ _.		... _ _
D	_..	Q	_ _. _		.... _
E	.	R	. _.		.....
F	.. _.	S	...		_....
G	_ _.	T	_		_ _...
H	....	U	.. _		_ _ _..
I	..	V	... _		_ _ _ _.
J	. _ _ _	W	. _ _		_ _ _ _ _
K	_. _	X	_.. _
L	. _..	Y	_. _ _
M	_ _	Z	_ _..

 

D. Check-Up

 

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

automatic pilot CDI decision height glide path glide slope

instrument approach marker beacon microwaves MLS Morse code

1. A ___________ identifies location by transmitting a signal to an aircraft.

2. An ILS using microwave frequencies is an ___________.

3. An ___________ automatically flies an aircraft.

4. A radio beam that indicates an aircraft's descent path is a ___________.

5. ___________ utilizes a combination of long and short signals to represent letters and numbers.

6. A ___________ provides lateral guidance to an aircraft on its approach.

7. When a plane lands using instruments and radio guidance, it has made an ___________.

8. A ___________ provides vertical guidance to an aircraft on its approach.

9. The height at which a pilot decides whether to continue an approach is the ___________.

10. Short electromagnetic waves used for radar are ___________.