Aural Null Procedures Air Search

Module 9

of

CASARA ELT Training Plan

Aural Null

Using aircraft communications radio

Aural Null

Procedure A Procedure B

AURAL NULL PROCEDURE

• In the event that your homer is not working, you must know Aural Null methods, “A”, and “B”.

• The only equipment you need is:• VHF receiver

• clock

• map

• pen

Signal ReceptionBeware of a difference of signal

reception on the nose of the search aircraft, as compared to the signal off of the tail. Signal strength may vary enough between the two so as to make the results inaccurate. If this occurs it is recommended that readings be taken off of the nose. It will mean flying out of the signal, then making a 180 degree turn and coming back on the same track. When flying back towards the signal, take your readings once the signal is heard again.

Signal Detected

Signal Faded

• Descend to minimum reception altitude.

• Disable squelch if possible and adjust radio volume to minimum reception.

When signal detected:

• Fly a constant heading and draw a track made good on the map.

• Pinpoint your position on map.

• Once signal is lost, do a 180º turn and mark the spot (A) where the signal is acquired again.

• Maintain constant altitude and volume setting at all times.

When signal detected: AURAL NULL PROCEDURE “A”

Signal Detected

Mark Position Draw Track line

A

When signal fades out

Mark PositionSignal Detected Calculate Halfway pt.

B

A

C

• Fly along the same track and pinpoint position of fade out (B), do another 180º.

• Calculate mid-point of track made good (C).

• From this mid-point plot at 90 degrees, a new desired track which extends on both sides of track made good.

• Return to mid point and fly either direction to make good, the new track.

• When signal strength fades out, plot this point on your map (D)– Reverse course, signal will

build and then fade. Plot point at which signal fades (E)

Mark PositionSignal fade

B

A

C

D

E

Make 180 deg turn

When signal fades out

ELT Location

• In theory, the ELT should be located at the mid point of the second track

• Terrain, obstructions and aircraft wreckage can skew the points and make finding the ELT more difficult.

B

A

C

D

E

Fly to Calculate Halfway pt.Calculated ELT Location

Signal Detected

Mark PositionAnd heading

Draw Track line

A

B

Signal FadedMake 180 deg turnSignal DetectedMark Position

Calculate Halfway pt.

Mark Calculated Halfway pt.

CDraw Track line 90 deg to 1st track line

Fly to Calculated Halfway pt. turn left or right and fly until signal fade

Signal fadedMake 180 deg turnSignal DetectedMark PositionDFly track until signal fade

Signal fadedMake 180 deg turnSignal DetectedMark Position

E

Fly to Calculated Halfway pt.

Calculated ELT Location

Are there any questions?

AURAL NULL PROCEDURE “B”

• This method has both an advantage, and disadvantage:– ADVANTAGE: It is faster than Procedure “A”– DISADVANTAGE: It requires sufficient

cockpit space to adequately plot the information

• Requires:– VHF receiver - pen - dividers– map - ruler - 900 triangle

AURAL NULL PROCEDURE “B

• Position of the aircraft is plotted as soon as the signal is heard

• Continue on same heading for a short distance

• Turn 900 either left or right, and proceed until the signal fades. Note this position

• Turn aircraft 1800 and again plot where the signal is heard, and where it fades

• Approximate position of ELT is plotted by:– drawing chord lines

between each set of “signal heard” and “signal fades” positions

– Drawing perpendicular bisectors of each chord

AURAL NULL PROCEDURE “B

• Aircraft proceeds to the point where the perpendicular bisectors intersect.

• The ELT should be there

Are there any questions?

That’s All For Now

Have a pleasant flight!

““THAT OTHERS MAY LIVE”THAT OTHERS MAY LIVE”

THANK YOUTHANK YOU

CA

SA

RA

CA

SA

RA