Operational Check of the Underwater Locator Beacon (ULB)

TASK 23-71-00-720-001-A
Operational Check of the Underwater Locator Beacon (ULB)

WARNING: BE CAREFUL WHEN YOU USE CONSUMABLE MATERIALS. OBEY THE MATERIAL MANUFACTURER'S INSTRUCTIONS AND YOUR LOCAL REGULATIONS.

CAUTION: DO NOT PUT MARKINGS OR LABELS ON THE ULB (ONLY THE BATTERY REPLACEMENT LABEL IS PERMITTED). THEY CAN DECREASE THE PROPAGATION.

ZONE: 312

1. Reason for the Job
Refer to the MPD TASK: 237135-02
OPERATIONAL CHECK OF ULB
This procedure gives the instructions necessary to do a check of the ULB with the ultrasonic test set and the portable test set.

NOTE: You can use one or the other of these test sets to do this test.

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	ELECTRICAL LEAD
No specific	1	STOPWATCH
42A12-1	1	ULTRASONIC TEST SET (42A12-1)
TS200	1	ULTRASONIC TEST SET (TS200)

B. Consumable Materials

REFERENCE	DESIGNATION
(Material No.08BBV9)	Non Aqueous Cleaner-- Trichlorotrifluoroethane Legacy

C. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
312	AFT FUSLG TAIL SECTION
312AR

D. Referenced Information

REFERENCE	DESIGNATION
TASK 23-71-35-920-001-A	Discard ULB Battery
TASK 24-41-00-861-002-A	Energize the Aircraft Electrical Circuits from the External Power
TASK 24-41-00-861-002-A-01	Energize the Aircraft Electrical Circuits from the APU
TASK 24-41-00-861-002-A-02	Energize the Aircraft Electrical Circuits from Engine 1(2)
TASK 24-41-00-862-002-A	De-energize the Aircraft Electrical Circuits Supplied from the External Power
TASK 24-41-00-862-002-A-01	De-energize the Aircraft Electrical Circuits Supplied from the APU
TASK 24-41-00-862-002-A-02	De-energize the Aircraft Electrical Circuits Supplied from the Engine 1(2)

3. Job Set-up
Subtask 23-71-00-860-054-A

A. Aircraft Maintenance Configuration
(1) Energize the aircraft electrical circuits. (Ref. AMM TASK 24-41-00-861-002)
(2) Open the accessory compartment access-door 312AR.
(3) Set the light switch 3LJ on panel 5026VE to the ON position.

Subtask 23-71-00-840-050-A

B. Preparation for the test
(1) On the ULB, read the date on the battery replacement label.
If the date is expired, replace the battery. (Ref. AMM TASK 23-71-35-920-001)

NOTE: It is not necessary to remove the beacon from its support on the aircraft during this test.

4. Procedure
Subtask 23-71-00-720-051-A

A. Operational Test of the ULB with the 42A12-1 ULTRASONIC TEST SET (42A12-1)

ACTION	RESULT
1.Turn the GAIN potentiometer to a fully clockwise position.
2.Set the TUNING knob to between 36.5KHz and 38.5KHz
3.Rub the fingers in front of the microphone.	From speaker you must hear a noise.
4.On the CVR at the ULB: Make a short circuit between the ULB water switch and the battery body with an ELECTRICAL LEAD.
5.On the Ultrasonic Test Set: Set the GAIN control at a good listening level. Point the microphone of the test set to the water switch end of the beacon.	On the Ultrasonic Test Set: A pulse tone heard from the ULTRASONIC TEST SET shows that the beacon is operational. If no sound is heard replace the ULB (Ref. AMM TASK 23-71-35-920-001).
6.Calculate the pulse rate: Count the number of pulses from the ULB during a 10-second cycle measured with a STOPWATCH Divide the number of pulses by 10 (i.e. the number of seconds in the cycle).	The pulse rate must be approximately one pulse per second.

NOTE: The pulse rate measured in air will be more than the manufacturer pulse rate (measured in water).
If the pulse rate increases or decreases, you must replace the battery (Ref. AMM TASK 23-71-35-920-001).
If the ULB does not operate correctly after the replacement of the battery, send the related ULB battery to the workshop for discard and replace it with the new ULB battery.

Subtask 23-71-00-720-056-A

B. Operational Test of the ULB with the TS200 ULTRASONIC TEST SET (TS200)

ACTION	RESULT
1.Set the switch to the ON position.
On the ULB: Attach the clamp to the ULB housing. With the measurement needle, touch the water switch on the ULB.
2. Push and hold the red test button on the test set. During a cycle of 10 seconds, make sure that you can count a minimum of nine pulses.	You hear a pulse tone.

5. Close-up
Subtask 23-71-00-860-055-A

A. Put the aircraft back to its initial configuration.
(1) For the 42A12-1 ULTRASONIC TEST SET (42A12-1):
(a) On the ultrasonic test set:

Set the TUNING potentiometer to zero.
Set the GAIN potentiometer to OFF.

(b) Disconnect the electrical lead that connects the water switch to the body of the battery (short circuit).
(c) Make sure that there is no grease on the support of the ULB and the water switch.
If there is grease, remove it with Non Aqueous Cleaner-- Trichlorotrifluoroethane Legacy (Material No.08BBV9) .
(d) Make sure that there are no markings or labels other than the battery replacement label on the ULB. The markings or labels can decrease the propagation.
(2) For the TS200 ULTRASONIC TEST SET (TS200):
(a) Disconnect the plug of the harness from the Ultrasonic Test Set.
(b) De-energize the test set with the slide switch on the left side of the housing.
(3) Make sure that the work area is clean and clear of tools and other items.
(4) Set the light switch 3LJ on panel 5026VE to the OFF position.
(5) Close the accessory compartment access-door 312AR.
(6) De-energize the aircraft electrical circuits
(Ref. AMM TASK 24-41-00-862-002).

[Rev.10 from 2021] 2026.04.02 06:51:01 UTC