Avidyne ADS-B Solutions – The Interfaces – and How They Work The first piece of the puzzle is understanding what ADS-B is. You will often hear people refer to ADS-B “In” or ADS-B “Out”. There is a very important distinction to be made between these two. Also, there is FIS-B Weather. We will start with ADS-B “Out”

ADS-B “Out” ADS-B “Out” ability to transmit a properly formatted ADS-B message from the aircraft to ground stations and to ADS-B-In-equipped aircraft. (both pressure altitude and GPS location). The FAA has mandated that all aircraft in the US must comply with ADS-B Out performance by January 1, 2020, to operate in designated airspace.

AC B FAA Advisory Circular (AC B) provides guidance for the installation and airworthiness approval of Automatic Dependent Surveillance – Broadcast (ADS-B) OUT systems in aircraft. Avidyne currently has 2 products that are capable of ADS-B Out (as of 12/11/2015) They are the AXP340, and AXP322

2 Types of ADS-B OUT 1090 extended squitter (1090ES) and universal access transceiver (UAT). The 1090ES equipment operates on 1090 MHz and has performance requirements specified in TSO-C166b, and is required by CFR for operation in Class A airspace. The UAT operates on 978 MHz and has performance requirements specified in TSO-C154c

AXP-340 First and foremost, the AXP340 is a standard Mode S transponder. The AXP340 has the added capability of ADS-B OUT and meets the requirements for 1090 ES ADS-B OUT operation. We will explore the ins and out of installing the AXP340, and what additional things must be done during installation to ensure it is in compliance.

AXP340 Installation

AXP340 Altitude Source Let’s first take a look at the altitude source, which is required for even a Mode S installation. There are some specific things we will need to understand about how the AXP340 prioritizes altitude information if it is being received by multiple sources.

AXP340 Altitude Source The AXP340 must be connected to an approved altitude encoding source. The AXP340 can use either a parallel Gillham code altitude input, or serial RS232 altitude input. Serial formats allow a higher resolution altitude representation that can be used by Mode S interrogations, whereas parallel Gillham (gray) code format can only represent altitude to the nearest 100 feet. If a parallel Gillham encoder is connected the AXP340 will always use that as the altitude source even if a serial encoder is also connected.

AXP340 Altitude Source If a parallel Gillham encoder is connected the AXP340 will always use that as the altitude source even if a serial encoder is also connected. This was repeated on purpose. This is very important to understand. Another way to say this is “If a parallel Gillham encoder is connected the AXP340 will IGNORE any serial altitude input.”

AXP340 ADS-B OUT As previously discussed, the AXP340 requires a certified GPS position source. In the following case examples we will assume the Avidyne IFD is being used as the GPS position source.

AXP340 – GPS Position Source Interface The GPS Source input on the AXP340 should be configured to TRIG ADS-B with a baud rate of 9600 The GPS Source Output (RS-232) from the IFD540 should be configured to ADS-B (AVI) Also, note that this ADS-B data stream will also include a variation of serial altitude information.

AXP340 GPS Position Source Interface The AXP340 includes a serial altitude output which repeats the altitude received on the encoded input (either parallel Gillham or serial) for connection to a GPS or other equipment. The serial output supplies RS232 output levels, and runs at 9600 bps, no parity. The output format is always “Icarus/Trimble/Garmin” format

AXP340 GPS Position Source Interface The IM calls out all over the place that you can feed the serial altitude output from the AXP340 to the IFD to provide altitude to the IFD. This should only be done if the AXP340 has parallel Gillham code as it’s original altitude source. Due to the priority scheme in the AXP340 If the original source is RS-232, and the AXP340 “repeats” this altitude to the IFD, the IFD will then feed that same altitude back to the AXP340 causing an altitude loop. This is caused by the AXP340 seeing the altitude information included in the ADS-B stream coming from the IFD as a higher priority than the RS-232 altitude coming in from the encoder or ADC.

This is WRONG! In this scenario, notice we are using a “serial” altitude source coming in on the AXP340 pin 7. We should NOT be using serial altitude out from the AXP340 to the IFD. This scenario will cause an altitude loop.

What will an altitude loop look like to the pilot? When we see an altitude loop happening, the indication is that the aircraft checks out fine on the ground. Upon power up, the serial encoder comes online before the IFD, so the encoder sees ground elevation. It sends that altitude to the AXP340, which then “repeats” that altitude to the IFD. The IFD then includes that altitude in the ADS-B stream going back to the AXP340 At this point, the AXP340 begins to ignore the serial encoder, and listen exclusively to the ADS-B output, so the altitude path has now become AXP340 to the IFD to the AXP340 to the IFD etc…

How can we fix it, if the shop has already done this? If the aircraft is already wired up this way, and we have figured out the “hard way” that an altitude loop exists, don’t fret. This is easy to fix. The altitude input on the IFD will be set to Icarus Alt. Simply turn that RS-232 port off, and the IFD will no longer be accepting the altitude from the AXP340.

This is OK! Notice the AXP340 is receiving “serial” altitude from the encoder or ADC, but the serial altitude output from the AXP340 at pin 6 is NOT connected.

This is OK Too! Notice in this scenario, there is nothing connected to the serial altitude input to the AXP340 on pin 7. Instead we are using Gray code altitude input, and in this case it’s ok to connect the serial altitude output from the AXP340 pin 6 to the IFD.

AXP340 Squat Switch ADS-B out installations must have a method of automatically determining the Air-ground status of the aircraft. The AXP340 transponder can use any one of the following sources: ◦  Aircraft Squat (weight on wheels) Switch ◦  Airspeed Switch ◦  Pseudo Weight-on-Wheels output (e.g. GPS derived output such as Avidyne IFD540 and Entegra Release 9 outputs) ◦  Auto-switch on Airdata GPS (e.g. ADC serial input such as Shadin ADC formats, see sec 6.5.4) ◦  Collective switch for Part 27/29 aircraft (Note: additional approval required)

Pseudo Weight on Wheels If this connection is used in lieu of a traditional “squat switch” there is no special configuration needed on the IFD. It will put a discreet (ground) on this line until the IFD senses 35 knots GPS ground speed at which point it will remove the low (open). The AXP340 Squat Switch source should be configured for “Low when Ground”

All of the other AXP340 Configuration items System Certification Level ◦ C (IFD is actually certified to level B, but since the AXP is only level C, it must be set to C) GPS NACv ◦ 10 meters per second The ADS-B output should be able to be tested with an IFR6000 that is ADS-B capable. The other option is to the FAA at Requesting an ADS-B check on your tail number.

AXP322 Remote Mount Transponder The STC has not been approved for ADS- B out on this unit as of 12/11/2015. Therefore, the AXP322 settings in the IFD540 should be set to “un-certified.” But we will get to that soon enough. First, we will discuss how the AXP322 gets it’s altitude information for normal Mode S operation

AXP322 Altitude Input The IFD5XX/4XX retransmits the Altitude data received from external altitude devices to AXP322. The IFD5XX/4XX will use the airdata source with the highest priority, reference Section Installers must ensure the airdata source being used for transponder Mode C transmissions complies with 14 CFR After installation, the transponder system must be tested per 14 CFR to verify the airdata retransmitted by IFD5XX/4XX is operating correctly prior to return to service. With that being said, we need to understand that altitude into the IFD is absolutely REQUIRED for the AXP322 to work.

AXP322 Altitude Input It is of the utmost importance to understand how the IFD will prioritize altitude inputs. This becomes even more important when the IFD is interfaced to the AXP322. Let’s look at a couple of different scenarios keeping this priority scheme in mind.

AXP322 Altitude Input Scenario Let’s say we have an IFD540 interfaced to an AXP322. The IFD is receiving altitude directly from the aircraft’s RS-232 altitude encoder, which has been certified under CFR There is also an old Gray Code encoder installed in the aircraft that hasn’t been certified in many years. It is only feeding altitude information to a traffic unit. We are receiving Traffic via 429 from the traffic unit for display on the IFD In this scenario, is the installation “legal?”

AXP322 Altitude Input Scenario - Continued The answer is NO the installation is not legal! Why not? Because the IFD is now ignoring its “certified” altitude input in lieu of the 429 Traffic Advisory input which is using a non-certified source Due to the IFD’s priority scheme, it sees the altitude info coming from the traffic unit as a higher priority than that of the rs-232 encoder When this happens, the IFD will pass the non- certified altitude to the AXP322 This is not good.

AXP322 Configuration Data Since the AXP322 is “remote mount” there is no faceplate, so all configuration items will take place via the IFD in Mx Mode AXP322 configs are listed on the next slide

IFD Mx Mode AXP322 Configuration settings

2 Types of ADS-B IN 1090 extended squitter (1090ES) and universal access transceiver (UAT). The 1090ES equipment operates on 1090 MHz and has performance requirements specified in TSO-C166b, and is required by CFR for operation in Class A airspace. The UAT operates on 978 MHz and has performance requirements specified in TSO-C154c

Avidyne ADS-B IN options TAS6xx A – These are 1090 ADSB-in capable MLB-100 – This one is a 978MHz UAT Receiver

MLB-100 What will the MLB-100 do? ◦ The MLB100 will receive traffic information directly from nearby 978MHz (ADS-B Out)-equipped aircraft, and indirectly through the rebroadcast of 1090MHz (ADS-B Out)-equipped aircraft via 978MHz ADS-R. ◦ The MLB-100 will provide Flight Information System- Broadcast (FIS-B) weather information, including NEXRAD radar, METARs,TAFs, AIRMETs, SIGMETs, Special Use Airspace (SUA), and Temporary Flight Restrictions (TFRs). ◦ Traffic information from aircraft not participating in ADS-B is received from ground stations via 978MHz TIS-B transmissions (Traffic Information Service- Broadcast).

MLB-100 Installation Information The MLB has multiple interfaces to the IFD. The IFD will provide GPS position data via the standard “Aviation” output on the RS- 232 out configurations The IFD also has two way communication to the MLB-100 via RS-232 in and out set to MLB-100 this connection is used for FIS-B Weather products The MLB-100 provides ARINC429 Traffic to the IFD and the setting on the IFD 429 input set to MLB100 Traffic - High Speed

MLB-100 Installation Information The MLB100 may need to be re- configured using the Avidyne UAT console (version 4.0.9) as follows, GPS: Aviation Format (To and From the IFD) Display Port 1: Avidyne, (To the IFD) ARINC Port: High Speed traffic (To the IFD) FIS-B messages per second: 4 messages

TAS6xx-A How does the TAS-A Work? Avidyne’s VeriTAS is a hybrid traffic avoidance solution that merges both active traffic (Avidyne TAS600 Series) and ADS-B traffic into one system. VeriTAS constantly compares the active traffic target information with ADS-B traffic information to ensure the pilot has most accurate traffic information and alerting. Because of the latency issues associated with both TIS-B and ADS-R traffic information (where it’s available), VeriTAS will use TIS-B and ADS-R to reinforce the accuracy of the active traffic targets.

TAS-A What’s different about the installation from a legacy TAS? ◦ The TAS-A system will require GPS position input from a WAAS GPS position source ◦ Power and ground pins have been moved from the P1 connector pins 1&2 for power; pins 14&15 for ground (Still here for legacy TAS (non TAS-A) units. ◦ On TAS-A units Power is now P2 pins 58&77; ground is P2 pin 59. ◦ Encoder lines have moved from P1 to P2 ◦ Suppression wiring has moved from P1 pins 7&15 to P2 pins 56&59 respectively.