ADSB?

[TedK]

I realize it is part of the regulation, but the question is "Why?". There is no legitimate reason VFR aircraft need to be identified by N-number on whatever system(s) the FAA is running.

The UAT units have an anonymous mode. No reason to have an N number entered. The only thing that really seems to hamstring a portable UAT is the requirement to be integrated to an installed encoder that has passed its checks. And installed GPS and ADS-B antennas to give acceptable performance (yeah, thats the new requirement, have to meet the performance requirements)

I suppose you might be able to modify your encoders harness with some sort of a pigtail that was ready to plug into a portable ADS-B. You could drag the box from airplane to airplane, but each would have to have an already installed and ready encoder pigtail, GPS antenna and ADS-B antenna.

[cub builder]

I suppose you might be able to modify your encoders harness with some sort of a pigtail that was ready to plug into a portable ADS-B. You could drag the box from airplane to airplane, but each would have to have an already installed and ready encoder pigtail, GPS antenna and ADS-B antenna.

It's not clear to me that pressure altitude is required.

From Minimum Operational Performance Standards for UATs:

3.5.3 Altitude
Two sources of Altitude Data are defined in the ADS-B System. Barometric Pressure Altitude relative to a standard pressure of 1013.25 millibars (29.92 in.Hg.) shall be supplied to the ADS-B system. Altitude data, which is corrected for local barometric pressure, shall not be supplied to the ADS-B system. The ADS-B system and the ATC transponder (if installed) shall derive Pressure Altitude from the same sensor (e.g., air data computer or encoding altimeter). If a pressure altitude source with 26-foot or better resolution is available on the aircraft, that source shall be connected to the ADS-B Transmitting Subsystem. Geometric Altitude is derived from the height above the WGS-84 ellipsoid by the GPS/GNSS navigation receiver.

3.5.3.1 Altitude Reporting Source
An interface shall be provided that allows the flight crew to disable the reporting of Barometric Pressure Altitude by the ADS-B equipment.

Note that it says two sources are defined, not required. There is a bit set in the UAT transmission that tags the altitude source as either Pressure Altitude or GPS Altitude. Additionally, the requirement to connect to a pressure altitude is for a 26 foot or better resolution in pressure altitude. Mode-C only has 100 foot resolution.

Tons or reading in this document, and more than I'm willing (or able) to digest. Depending on interpretation, it could be interpreted as self conflicting.

Cub Builder

[CharleyB]

NavWorx has recently come out with a non-TSO ADS-B-out device for Experimental Aircraft. It is offered at a limited time price of $600. It is a remotely mounted box that will use currently installed transponders, has its own WAAS GPS, and will provide ADS-B-In info vial WiFi or a RS-232 cable. Basically a plug and play box.

It is my understanding that it will require testing and certification similar to what is now required for ordinary transponders to legally fly IFR. I also understand that the testing equipment is very expensive and few avionics shops now have the equipment. It is safe to say certification will be expensive and probably have to be done every two years.

For more details, see the following:

http://www.navworx.com/navworx_store...DS600_EXP.html

[cub builder]

Re: SkyGuard, do they or don't they meet the performance specs?

-----
From Skyguard:
We have been talking with the FAA on exactly what this new rule update
for experimental aircrafts means. Even our local FAA (ACO) office does
not yet have the details. As we interpret the new wording, it seems to
state that you can put a non-TSO'd ADS-B Transmitter/Transceiver in
an "experimental class" aircraft and you would be meeting the 2020
mandate. But we don't yet have an official answer on that from the FAA.
The big question is will this non-certified unit be required to have a
certified GPS position source? If not, then our units should comply
with the new ruling. If a certified GPS position source is still required,
then we will need to continue with the certification of our GPS source.
More updates as we learn them.
-----

Since I have one of their units in one of my E-AB aircraft, next time we get some decent weather to fly, I'll try emailing <9-AWA-AFS-300-ADSB-AvionicsCheck@faa.gov> and see what I get back. Will report back then...

-Cub Builder

[TedK]

i had hoped the recent ADS-B rule change might permit nonTSO'd ADS-Bs to be used in Certificated Aircraft (similar to nonTSO'd AOAs) and queried the FAA. Unfortunately, that is not the case per the response I got back from the FAA. Posted below.

Ted
---------------------------------------------------

Regarding your recent inquiry (below) concerning the technical amendment of 14 CFR part 91.225:

“Would this permit a non-TSO'd ADS-B that met the "performance requirements" of the applicable TSO to be installed in a Certificated Airplane operated under Part 91?”

The ADS-B rule contained in §91.225 (as amended) does not change any existing regulatory requirement for alteration of a type certificated aircraft. An ADS-B transmitter (TSO-C166b or TSO-C154c, as applicable) installed on a type certificated aircraft through either a supplemental type-certificate or field approval must have been manufactured under an FAA production approval (TSO authorization) as required by 14 CFR §21.9(a)(2) and marked accordingly per §45.15.

Thank you for the opportunity to clarify the technical amendment to §91.225.

Regards,

James Marks
Aviation Safety Inspector (AC/AV)
ADS-B Focus Team Lead
Flight Standards Service
Avionics Branch (AFS-360)
Office (202) 267-1707

[cub builder]

Re: SkyGuard, do they or don't they meet the performance specs?
-----
Since I have one of their units in one of my E-AB aircraft, next time we get some decent weather to fly, I'll try emailing <9-AWA-AFS-300-ADSB-AvionicsCheck@faa.gov> and see what I get back. Will report back then...

I sent a request to the FAA this weekend following a flight requesting a report on the performance of my Skyguard TWX ADS-B unit. The reply said "The report indicates there are software issues so make sure all software is up to date."

In typical FAA Fashion, the report is loaded with acronyms and numbers that seemed somewhat meaningless. They also attached a second document explaining how to read the report. My interpretation was that the Skyguard unit fails because it has no barometric altitude reporting. That seems to answer the question as to whether a pressure altitude report is required in ADS-B out. I'll post the report as a links to this post.
ADS-B report on my Skyguard TWX
FAA Guide to interpreting ADS-B Avionics Check

-Cub Builder

[TedK]

Interesting article at AOPA with FAA Attachment.

It seems rather bizarre to me that an avionics maker can list nearly any GA aircraft on their Approvel Model List without significant engineering to ensure that the airplanes on the AML are truly compatible with the Avionics without holding any discussion with the airplane OEM, and these airplanes can be used in commercial service. But in the case of an SLSA, the avionics maker has got to mother-may-I the SLSA OEM.

Seems bass akwards to me.

Ted