90-Day Beacon

Creating an industry standard

L3Harris believes that the aviation industry is moving toward a 90-day underwater location beacon standard. With the introduction of the L3Harris 90-Day Beacon in 2015, L3Harris has made a commitment to provide upgrade kits that are in accordance with the 90-day beacon mandate, allowing operators to remain in factory Component Maintenance Manual (CMM) compliance as they upgrade their fielded recorders.

Designed to perform, built to survive

The 6.7-ounce aluminum-cased L3Harris 90-Day Beacon is watertight, and capable of operating at depths of 20,000 feet (6,096 meters) and has a direction range of 2,000 to 4,000 yards (1,800 to 3,500 meters) depending on environmental factors. It is built to withstand a sustained pressure of up to 8,700 psi.

Easy to maintain

The L3Harris 90-Day Beacon requires a routine maintenance check every two years as outlined in the L3Harris Component Maintenance Manual (CMM). Its long-life battery should be replaced every six years.


The beacon will provide a minimum of 90 days of uninterrupted operation once activated complying with TSO-C121b, which is an upgrade to the 30-day beacon. It is tested to, and meets or exceeds, all requirements of FAA TSO-C121b and SAE 8045A. The beacon’s batteries are tested in accordance with TSO-C142a.


• Water-tight aluminum case 1.3 in. diameter (3.3 cm)/3.92 in. length (9.95 cm)
• Capable of operating at depths of 20,000 ft. (6,096 m)
• Detection range of 1,800 to 3,600 meters (2,000 to 4,000 yards) depending on environmental factors
• Built to withstand a sustained pressure of up to 8,700 psi
• Weighs 6.7 ounces


• Water switch actuation initiates beacon operation post submersion in either fresh or salt water
• Sustained operation > 90 days
• 160dB at a frequency of 37.5 KHz
• 10 ms pulse occurring once per second


• 2-year routine maintenance check as outlined in L3 Component Maintenance Manual (CMM)
• 6-year battery replacement


L3Harris Aviation Recorder Family

90-Day Beacon Retrofit Kit

Content Description

Standard Product


L3Harris-approved retrofit kit for standard products (kit comes with an L3Harris Service Bulletin enabling the conversion and Manufacturing Inspection District Office (MIDO)-approved installation instructions)

Legacy Products


L3Harris-approved retrofit kit for legacy products (kit comes with an L3Harris Service Bulletin enabling the conversion and MIDO-approved installation instructions)

(Tactical Recorders)


L3Harris-approved retrofit kit for SRVIVR products (kit comes with an L3Harris Service Bulletin enabling the conversion and MIDO-approved installation instructions)

  • 90-Day Battery Replacement Kit: P/N 147-E5542-00
  • 30-Day Battery Replacement Kit: P/N 147-E0305-00

L3Harris Aviation Recorders Quality Management System is ISO 9001:2008 and AS9100:2009 Rev. C Certified


  • What is an underwater locator beacon?
      • An underwater locator beacon is an underwater acoustic locating device designed to survive the impact of an aircraft crash. The device is attached to the cockpit voice recorder and flight data recorders. It is designed to begin emitting a periodic ultrasonic acoustic signal at a frequency of 37.5 kHz when submerged in water.
      • The underwater locator beacon is powered by a lithium battery with a lifespan of 6 years. Typical maintenance requires the beacon to be tested every two years and a full battery replacement every 6 years.
      • The underwater locator beacon is approved in compliance with Technical Standard Order (TSO) C121, C121a, or C121b. Each recorder with beacon provisions manufactured by L3Harris is compliant with a system level TSO which includes an underwater locating beacon as a subset.
  • Who needs/uses an underwater locator beacon?

      All operators/ aircraft that require a flight data recorder and/or cockpit voice recorder also are required to have an underwater locator beacon attached to those recorders.

  • What are the regulations that impact underwater locator beacons?
      • The rules governing underwater locator beacons are the Federal Aviation Administration (FAA) TSO-C121, C121a, and C121b. European Aviation Safety Agency (EASA) is expected to publish ETSO requirements that parallel the FAA standards.
      • Most recently the FAA announced that it would no longer be granting TSO-C121 or C121a approvals to beacons manufactured after December 1, 2015. The intent of this approach is to limit the new manufacture of underwater locating beacons to the newest 90-day standard, TSO-C121b.
      • L3Harris' interpretation of this change is that the FAA hopes to move the industry towards only the 90-day standard underwater locator beacon through attrition. 30-day beacons that are fielded can continue to be used as long as they are serviceable.
      • The European Aviation Safety Agency (EASA) recently published a draft rule change that will require all Commercial Transport Aircraft to be equipped with recorders including the 90-day beacon by 2018. Many people in the industry believe that this will be approved by the EU in 2015 with a mandatory adoption date by the end of 2018. It is L3Harris' belief that with the FAA notice and recent tragedies surrounding Malaysia Flight 370, as well as the availability of the new 90 day beacon, all signs indicate adoption by the European Union.
      • L3Harris is in the process of updating the Component Maintenance Manuals (CMMs) associated with products affected by the newest standards. The CMMs provide specific guidance on which 90-day beacon retrofit kits will be available for which product along with the proper maintenance information as it relates to the Recorder and underwater locating beacon.
  • How will L3Harris handle the update to beacons that fall under their recorder TSO?
      • L3Harris will offer a 90-day retrofit kit for each serviceable product that carries a beacon today. This approach makes a 90-day beacon immediately available to all of our customers who would like to fit their product with a compliant beacon. L3Harris has updated the corresponding component maintenance manuals with the appropriate retrofit kits to be fielded. A service bulletin is available, as a part of each associated retro-fit kit, detailing the steps for a compliant installation in the field.
      • L3Harris offers 30-day battery replacement kits for customers unable to transition to a 90-day beacon retrofit solution. The CMMs have been updated with the part number for these replacements as well.
  • When will the 90-day beacon be available?

      The L3Harris beacon received TSO approval in late December, 2014 and is now available.

  • Where can I purchase a 90-day beacon compliant to both TSO-C121b and an L3 recorder?

      L3Harris is offering a one stop shop for all underwater locator beacon needs. We will offer a 90-day beacon compliant with our recorders (compliant under our recorder TSO), compliant L3Harris 90-day battery replacement kits, and compliant 30-day battery replacement kits. Additionally, we will offer battery testers to perform a return to service test.

  • Why would I want to retrofit my fleet early or all at one time?

      Some of our customers have indicated an interest in converting their entire fleet to the 90-day beacon immediately. Reasons to consider an immediate fleet-wide transition:

      1. Permits you to complete the maintenance at one time,
      2. Enables you to insure complete traceability as to which aircraft and recorders have been upgraded the newly compliant underwater locator beacons, and
      3. Allows you to claim that you have become fully compliant with the most advanced safety regulations. L3Harris is willing to provide fleet wide transition assistance service to install the new beacons for customers who do not have their own maintenance capability or who prefer to have factory installation made available.
  • Will I be able to continue to support my 30-day beacon if I choose to do so?

      Although there are many reasons to switch (traceability, public image, safer product), the regulations permit you to continue to operate with a 30-day underwater locator beacon. In order to assist you in this choice, L3Harris will continue to make compliant battery replacement kits available.

  • Is the 90-day beacon an on-wing retrofit?

      L3Harris has designed the retrofit kits in such a manner that the conversion can be done on wing via beacon replacement and recorder nameplate modification marking.

  • Do I have to have a 90-day beacon to be compliant?

      No. The notice currently affects the manufacture of the underwater locating device. The EASA Notice of Proposed Amendment (NPA) indicates that European aircraft will however, be mandated to carry only the 90-day beacon. Simply translated, the 30-day beacons are no longer available for sale with a valid TSO certification, and can only be maintained. When the EASA rule change takes effect, those operators will be forced to change to the 90-day beacon.

  • Will L3Harris be issuing a service bulletin?

      L3Harris has started to release service bulletins for each product impacted by the beacon change. The service bulletins include Manufacturing Inspection District Office (MIDO) approved installation instructions. These service bulletins will be available as part of the 90-day retrofit kits.

  • I have orders in the system for recorders under the 30-day configuration. Do I need to do anything to convert my orders to the 90-day variant?

      L3Harris would prefer to begin transitioning these orders as soon as possible because the beacon battery has a shelf life. This means we are unable to stock 30-day beacons to continue production. We will be happy to work with you to transition the orders to the 90-day variant.

  • What additional equipment will I need to maintain and support the 90-day beacon?

      L3Harris sells a beacon test set to support the beacons in your fleet. Each of the retrofit kits and beacons will come with all necessary components to complete the replacement. (*a torque wrench is required but will not be included)

  • What are the warranties associated with the 90-day beacon?

      The 90-day beacon will carry a 1 year warranty.

  • Are there any special considerations related to the handling of the 90-day beacon?

      The new 90-day beacon has increased the size of the lithium battery to enabling it to operate for three times as long as the current underwater locator beacon. The increased size of this lithium battery will require special shipping and handling requirements. It is considered a class 9 hazmat.

Product support

Facility/Shipping/Mailing Address:
5353 52nd Street, S.E.
Grand Rapids, MI 49512-9704
Main Phone Line: +1 (616) 949-6600
Fax: +1 (616) 977-6898

Order Administration/Sales/General Inquiries:
Phone: +1 (800) 253-9525 or
+1 (616) 949-6600
Email: avionics.sales@L3Harris.com

Repair and Overhaul Administration:
Email: avionics.service@L3THarriscom
Phone: +1 (800) 253-9525
Fax: +1 (616) 977-6895

Technical Support:
Email: FieldService.Avionics@L3Harris.com
Phone: +1 (616) 949-6600
AOG Hotline: +1 (800) 453-0288 or +1 (616) 949-6600

Technical Publications: Avionics.TechPubs@L3Harris.com

Website: www.avionicstechpubs.com

Cage Code/Federal Supply Code: 25583

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