I3203

=What To Expect= Expect to do bearing intercepts, NDB holding, and one of the following approaches: KPNS NDB Rwy 35 or [http://www.myairplane.com/databases/approach/pdfs/05048N36.PDF KTLH NDB Rwy 36

Some instructors may have the first student do the KTLH NDB 36 and have the second student do the KMOB NDB 14.]

=ADF=

Characteristics
ADF/NDB (INAV WB pp. 6-3)

The group of navigational aids referred to collectively as non-directional beacons transmits a continuous carrier wave signal which is radiated equally around the station. Unlike VOR or TACAN stations, the signals transmitted by these stations have no directional properties themselves; thus the name "non-directional beacon" or NDB. The azimuth information presented by the NDB is relative to the nose of the aircraft, unlike VOR or TACAN, which presents its information as a magnetic radial from the station.

Because of the non-directional characteristics of their signals and other factors discussed later, azimuth information derived from an NDB is generally less accurate than information derived from a VOR or TACAN.

NDB's are an adjunct to, not an integral part of, the Low Altitude and Jet Airway structures. Aircraft need not be capable of navigating via NDB to fly within the Victor or Jet Route system. They serve as terminal approach navaids and additional means of identifying certain airways and approach fixes. These NDB's transmit a three-letter identifier continuously. It should be noted that when an NDB is used for an approach, the associated landing minimums will normally be higher than those for other types of navaids.

Low- or medium-frequency radio beacons transmit in the frequency band of 190 to 535 KHz. They transmit a continuous wave which can carry voice transmissions. Radio beacons are employed as additional navaids and fixes by which the pilot of an aircraft equipped with a Radio Compass receiver (e.g., KR-87) can determine his bearing and "home" to the station.

The power output of the facility, atmospheric conditions (thunderstorms, precipitation, and time of day), the surface over which the signal travels, and the sensitivity of the aircraft's receiver combine to determine the reception range of LF/MF NDB signals. Under ideal conditions, LF/MF NDB signals can be received from several hundred miles away, but the directional accuracy of signals at these ranges is very susceptible to atmospheric interference. In the vicinity of thunderstorms, LF/MF NDB signals may become totally unreliable.

Although they may sometimes be received from several hundred miles away, the power output and generally accepted ranges of the various classifications of LF/MF NDB's are as follows:

This information is presented, for your reference, in the front of the IFR Supplement, in the table labeled Radio Class Code.

The distances listed in the preceding paragraph should not be misconstrued to mean maximum reception ranges. These navaids are not limited to line-of-sight.

It is not expected that pilots carefully commit to memory the power output and the operational distance of the various class radio beacons. A general knowledge, however, will preclude the frustrating experience of trying to tune and receive a radio beacon classed as L at, say, a distance of 100 miles.

Equipment is provided at selected FSS's by which meteorological and NOTAM data are recorded on tapes and broadcast continuously over LF radio beacons. Broadcasts are made from a series of individual tape recordings. Changes, as they occur, are transcribed onto the tapes. The radio beacons providing automatic transcribed weather broadcast service which are depicted on the FLIP Enroute Charts are classified as H-SAB. The "SAB" portion of the symbol H-SAB means simultaneous automatic continuous broadcast.

Many instrument approach procedures listed in the FLIP Terminal use LF radio beacons. These are termed NDB approaches.

When a radio beacon is used together with an Instrument Landing System, it is called a Compass Locator and is assigned the Radio Class symbol L.

All radio beacons, except the Compass Locators, transmit a continuous three-letter identification in Morse code. (The identification of Compass Locators will be a two-letter Morse code group.)

If continuous automatic transcribed weather broadcast is available on a radio beacon frequency, the symbol AB will follow the appropriate "Radio Class" designator; e.0g., NDB (MHAB) (Nondirectional beacon, less than 50 watts, 25 NM range with transcribed weather broadcast).

If voice is not available on a radio beacon frequency, the symbol W will follow the "Radio Class" designator; e.g., NDB (HW).

To navigate by either LF/MF or UHF/NDB, the aircraft must be equipped with some type of direction finding equipment (DF). Most Navy aircraft now have Automatic Direction Finding (ADF) equipment installed on board. This equipment automatically determines the bearing to any selected radio station within its frequency and sensitivity range. This equipment may also be used as an auxiliary receiver for weather or lost communications information.

The operation of DF or ADF equipment depends chiefly on the characteristics of a loop antenna. A loop receiving antenna gives maximum reception when the plane of the loop is parallel to (in line with) the direction of wave travel. As the loop is rotated from this position, volume gradually decreases and reaches a minimum when the plane of the loop is perpendicular to the direction of wave travel.

These characteristics occur in a loop antenna because the receiver input from a loop antenna is the resultant of opposing voltages in the two halves of the loop. When current flows in a looped conductor, it flows in opposite directions in each half of the loop. This occurs when the plane of the loop is in line with the station. Because one side of the loop is closer to the station, there is a slight delay between the time the signal reaches the closer side and when it reaches the farther one. This creates a phase difference between the voltages induced in each half of the loop. This causes a resultant current flow through the transformer which creates a signal input to the receiver. As the antenna is turned perpendicular to the wave flow, this phase differential is reduced, thereby reducing the signal to the receiver, and reducing the volume. When the loop antenna is exactly perpendicular to the station, the induced voltage is theoretically zero, and the receiver strength is at a minimum. This position of the antenna is called the NULL position.

The null position of the loop antenna, rather than the maximum position, is used for direction finding; that is, a bearing is obtained when the plane of the loop is perpendicular to the line on which the radio waves are traveling when they strike the antenna. The null position is preferred because it can be determined more accurately than the maximum. A 25-degree rotation away from the maximum position causes a signal strength reduction of about 10%, while a 25-degree rotation away from the null position causes a 50 % change in the signal strength.

With the loop antenna rotated to the null position, the radio station being received is on a line perpendicular to the plane of the loop. However, this still leaves two possible directions, 180 degrees apart from each other. The inability of the loop antenna to determine which of the two possible directions is correct is called the 180-degree ambiguity of the loop. This 180-degree ambiguity is eliminated with a sensing antenna, when automatic direction finding equipment is used.

The loop antenna of the radio compass is automatically rotated to the null position when signals are being received over both the sensing and loop antennas, providing you have selected automatic direction finding as your mode of operation. The combination of signals energizes a phasing system which operates a motor attached to the loop antenna. Anytime the loop antenna is turned away from the null position, the phasing system activates the motor to return the loop to the null position. The bearing pointer on the RMI is electrically synchronized and turned with the loop, thus indicating the direction from which the radio waves are coming.

Limitations
When using ADF equipment, the loop antenna is automatically positioned to the null position. However, the antenna can only rotate about the vertical axis (in relation to the aircraft), and cannot tilt. Anytime the antenna is tilted, as when the aircraft is banked, the loop is tilted away from the null, and the motor is not capable of correcting for this error. This is called "dip error," and is present anytime the aircraft is not in level flight. The magnitude of this error depends upon the position of the aircraft from the station, altitude, range from the station, and the angle of bank used. "Dip error" is most noticeable when the aircraft is banked and the station is on the nose or tail. The ADF bearings should be considered accurate only when the aircraft is in level flight.

In the TH-57C, the KR 87 is the radio receiver for LF/MF reception. It is capable of receiving signals in the frequency range of 200-1799 KHz. This allows the pilot to select LF/MF NDB's and commercial broadcast stations (550-1700 KHz). It should be noted that commercial broadcast stations are not under FAA jurisdiction nor are they part of the airway system. They do not necessarily operate continuously, their signals are often highly directional, and the station does not identify itself often enough for airborne use. Even though not compatible with IFR operations, commercial stations can be used as a backup navaid, especially with flying off airways.

=NAVAID voice Capability= AIM 1-1-13

Voice equipped enroute radio navigational aids are under the operational control of either an FAA Automated Flight Service Station (AFSS) or an approach control facility.

HIWAS - broadcasts on some VOR navigation facilites (H)

Unless otherwise indicated on the chart, radio navaids operate continuously except during shutdowns for maintenance. Check NOTAMs.

Check Airport/Facilities Directory for hours of operation and availability.

Low Level Charts - Legend

SHADOW BOXES indicate FSS frequencies 122.2, 255.4 and emergency 121.5 and 243.0 are available at all FSSs and are not shown. All other frequencies are shown. Certain FSSs provide Local Airport Advisory (LAA) on 123.6. Frequencies transmit and receive except those followed by R or T: R - Receive only, T - Transmit only

These frequencies are usually associated with some NAVAID

=Tracking versus Homing= There are two methods which can be used to fly to a TACAN or VOR station:
 * 1) HOMING: This method is similar to what you did in BI’s. Simply turn the aircraft to place the head of the needle under the heading index of the RMI and “follow” it to the station. That works great without any winds, however, what are the odds of that? With winds blowing you off course, you’ll actually be flying a curved path as you try to keep the nose pointed at the station. This is normally only used when you are close to the station.
 * 2) TRACKING: Tracking consists of maintaining a straight path or course over the ground. In order to do this, the aircraft must turn slightly into the wind. When using this method, the needle will not normally be under the heading index but slightly to one side. In this case, you’ll have to rely on your CDI to alert you to a drift left or right of the desired course.

So basically, Tracking is Wind Corrected Homing

Don't forget about sections 403 (Homing) and 404(Tracking) in your instrument FTI

=Compressor Stall= INDICATIONS:
 * Popping or rumbling noise
 * Vibrations
 * Rapid rise in TOT
 * Ng fluctuation
 * Loss of power.

WARNING: Be prepared for complete power loss. PROCEDURES: *1. Collective—Reduce Note: Slight power (collective) reduction will often eliminate compressor stalls. *2. ENG Anti-ice switch - OFF *3. Cabin Heat Valve - OFF *4. Land as soon as possible.

WARNING: When accelerating the rotor system during the initial rotor engagement or after a full autorotation, exceeding 40-percent torque may induce compressor stall or engine chugging.

Note: Mild compressor stalls may occur that will allow powered flight if TOT is within operating limits.

=Engine Underspeed= INDICATIONS:
 * Low Nr
 * Low Nf.

PROCEDURES: *1. Collective — Adjust as required to maintain Nr in operating range. *2. Twist Grip — Full Open. *3. GOV RPM — Full increase. *4. Check power available with Nr in limits.

NOTE: Power available is considered to be sufficient if level flight can be maintained with Nr at 90% or higher. Do not decelerate below 50 KIAS (minimum power airspeed) while executing a power check.

If power is not sufficient: *5. Autorotate.

NOTE: If some usable power exists but level flight cannot be maintained, the power, if sufficient, may be utilized to effect a landing or minimize rate of descent en route to a more suitable site for autorotation. Terrain permitting, a sliding landing provides the lower power available.

If sufficient power is available: *6. Land as soon as possible.

=Engine Overspeed= INDICATIONS: PROCEDURES: *1. Collective — Adjust as required to maintain Nr in operating range. *2. Twist grip—Reduce (to maintain Nf in operating range). Note: The Nf overspeed must be controlled by continually coordinating collective and twist grip. *3. Collective/twist grip — Readjust. *4. Land as soon as possible.
 * Nr increase
 * Nf increase
 * Ng increase
 * TOT increase
 * Right yaw
 * Engine noise increase.