Implementing Mode 5 IFF Transponders Into Unmanned Aircraft Systems: What To Know

Press

Manned aircraft worldwide have implemented NATO’s requirement for Mode 5 Identification Friend or Foe (IFF) transponders using traditionally sized transponders. However, for unmanned aircraft, down to class 2, the challenges of smaller UAV airframes require new solutions and long-term thinking for a successful Mode 5 IFF transponder implementation.

The minimum specifications for Mode 5 IFF UAS transponders include:

Certification to DoD AIMS 17-1000 Mark XIIB
Civil modes A, C, and S functionality
ADS-B Out
Mode 5 response prioritization
Antenna diversity for space-based and ground-based visibility
Incorporation of internal crypto, or compatibility with an external crypto computer such as the KIV-77
Satisfaction of the robust environmental standards of MIL-STD-461 and MIL-STD-810.

Keeping these basic requirements in mind, here’s what we recommend you consider when you need to implement a Mode 5 IFF micro transponder, such as Sagetech’s MX12B Mode 5 IFF micro transponder, into your UAS:

1. Size and weight. Military legacy Mode 5 IFF transponders are very large by UAS standards – even the “mini” transponders can weigh in at about 6 pounds without the crypto appliqué. In UAS applications where size, weight, and power affect agility, flight longevity, and a host of other critical mission performance metrics, system designers need to reduce the SWaP footprint in a transponder while maintaining all the required functionality. Specifying a certified micro transponder can reduce your transponder size by up to 6x and weight by up to 93%. Compliant with the DoD AIMS 17-1000 specification, look for a micro-sized transponder that offers all the required functionality in a microelectronics format, with no deviations. Today’s units weigh in at under a pound.

*A typical “mini” manned aircraft Mode 5 IFF transponder is still much larger and heavier than a purpose-built UAS transponder.*

2. Power Output. For UAS, there is an appendix to AIMS 17-1000 that allows for reduced output power from transponders on unmanned vehicles. However, we believe that can ultimately prove limiting for your aircraft’s longevity and application across missions. Don’t skimp on output power and range – specify a micro transponder that includes the same output power as legacy larger-sized transponders, which is 57± 2 dBm.

3. Antenna Diversity. Again, for UAS, the appendix allows for a single antenna vs a dual antenna on small unmanned aircraft. However if you are looking to specify one micro transponder across multiple vehicles or programs, we recommend you specify one that offers the dual antenna technology but can operate in both single antenna and diversity modes. Additionally, using a diversity antenna system will only enhance your transponder’s performance in mission-critical situations.

4. ADS-B In and Out. While the spec only calls for ADS-B Out, integrated ADS-B In provides better situational awareness and ease of implementation. Mode 5 IFF is used when the aircraft is in military combat or training modes. However, a military UAV may also need to fly within the national airspace system (NAS) at some point. If so, it will need ADS-B In capability for situational awareness and communication with ATC and TCAS. Ensure your transponder includes this functionality, natively integrated, to save engineering integration time.

5. Flexible I/O. Ethernet rules the day, and may be required to provide enough bandwidth to support many ADS-B tracks, but legacy technologies of RS-232 and RS-422 can be effectively used for transponder control. Cover all potential situations with a transponder that offers all standard options.

6. Updated certifications. The Military Mode 5, DoD AIMS 17-1000 Mark XIIB specification replaces the legacy DoD AIMS 03-1000 Mark XIIA specification with updated requirements that dictate stronger encryption, different response prioritization in the transmitter, and GPS information about target aircraft locations. Update your legacy programs and specify solutions for new UAS programs with transponders officially certified to this new level. Like the legacy transponders, today’s new certified micro transponders offer the performance assurance of rigorous, methodical testing against thousands of requirements within DoD AIMS 17-1000.

7. Upgrade capability. Specifications are continually evolving, and soon we expect new specifications for Mode 5 Level 2B In and Out. Ensure your micro IFF Mode 5 transponder carries an upgrade path to include this future requirement.

8. Military heritage. IFF mission capability is serious, requiring significant technical expertise and complexity. Select a supplier steeped in military program experience to ensure military-proven technology, stability of supply, obsolescence policies, and logistics abilities including spares.

The above considerations are specifically offered with an exclusive focus on Mode 5 IFF applications. For transponder technology recommendations for any civil or military program, please see additional information in our whitepaper.

When specifying micro transponders for Mode 5 IFF requirements, don’t just look for minimalist specs. Think long-term, across multiple platforms and programs, to ensure what you specify works both today and tomorrow.

Sagetech’s MX12B Mode 5 IFF micro transponder packs 100%+ traditional transponder function into a UAS-sized SWaP package. Pre-certified units are now shipping.