Electronic Conspicuity in the UK

[cats_five]

It would be hard in many single seat gliders to fit extra batteries.

[Genghis the Engineer]

I think that we should separate this question out into two parts.

(1) What signal am I transmitting?

(2) Who and what can I see?

One of the obvious advantages to PAW is that it can see just about everything (at least if it's got the top end add-ons), whilst using very little power.

What signal you're transmitting is a separate question, in my opinion.

G

[SlopJockey]

Originally Posted by Lima Juliet

Yes but the DEP might be a standardisedposition, but it still gives a false impression in my own opinion. Human’s adapt their look out to compensate for the challenges like canopy arches and window frames. However, those sorts of diagrams make no allowance for that. Therefore, in my view (no pun intended), they are misleading.

DEP has to be standardised so you can assure the designer gets the format and layout of the flight deck correct. There are certification requirements to comply with not opinions.

See ACAS for full awareness of the capability.

Currently, the only commercially available implementations of ICAO standard for ACAS II (Airborne Collision Avoidance System) is TCAS II version 7.1 FLARM is relative and co-operative, P-FLARM uses additional data, transponder information. The exploitation of ADS-B out to enhance TCAS II capability is hybrid surveillance but still a variant of ACAS.

The real problem with and ABS-B In solution stems from accuracy of ADS-B Out. From the FAA:

What are the risks of using an uncertified position source?

The risk for any GPS receiver, when used to support separation services, is how far the position measurement can be in error without detection. If the position error gets large enough, air traffic control would not be able to provide safe separation between your aircraft and other traffic in your vicinity. FAA and our international peers conducted a safety analysis prior to publishing the final ADS-B rule to determine what this error detection boundary should be and the ADS-B performance requirements are based on the results of this safety analysis.

Certified GPS sensors compare GPS satellite measurements against each other. When a satellite signal error becomes large enough to detect, the receiver will reject that signal. The integrity performance specified in the ADS-B rule depends on the proper operation of this error detection feature. It ensures the safety of using ADS-B positioning based on GPSmeasurements.

By comparison, uncertified commercial grade GPS sensors assume the system is working properly and do not attempt to detect errors in the satellite measurements. When presented with an erroneous measurement, they will calculate an erroneous position. This was proven to be an unsafe condition by the FAA's safety analysis. Therefore, ADS-B position based on these sensors was prohibited from being used to support air traffic separation and ADS-B air-to-air operations.

So both TCAS and ADS-B (in and Out) are using certifiable equipment. General Aviation cannot afford the eqpt cost and fights the bureaucracy. Hence the "lightweight" (read cheap, non-assured,) items you get for GA and gliders. You fly these, you take the risks. Unless and until you get "clouted" by the one of the State's aircraft that are also flying in that Class G airspace, fully compliant. The State is easy to attack and the reputation has to be protected hence the attempts to define and install suitable systems in Mil aircraft.

However, UK Mil aircraft do not generally have certifiable eqpt, for lateral or vertical position ie not for RVSM or PBN therefore ADS-B solutions are likely not certifiable. And in some aircraft the height solution does not meet the necessary standard either so anything using the Mode S or 3C transponder ie TCAS may be working on erroneous data, worth noting by those that trust ATC height calls for conflicting aircraft!

Not sure i get either of the points:

Originally Posted by Lima Juliet

Obviously, TCAS will detect ADS-B Out if it is SIL=1 or above, but those using the Pilot Aware’s GPS for their Mode S ES transponders will pnly be outputting SIL=0.

and

Originally Posted by Lima Juliet

So many aircraft would see ADS-B if it was SIL=1 or above (ie. from a certified GPS source) and that would include the military.

TCAS II will detect ac that are transponding; Mode3/3c/S but TA/RA will be limited based upon which those modes it sees. As above quality of GPS solution affects ADS-B based ACAS but not TCAS II.

Please explain SIL =1 or above. Are you referring to Def Stan 00-56? SIL 1 is considered the 2nd lowest level in UK Mil Safety Related SW, after SOUP! "SIL1 has a dangerous failure rate band of 10−1 to 10−2 per year)" so not very secure. Civ eqpt manufacturers nearly always use DO-178 and DAL A (highest), down to DAL D or E(SOUP). A system could not be called ADS-B unless it has high a high level of SW assurance, see AC 20-165, "Note: Although the direct effects to your aircraft of an ADS-B failure may be minor, the ADS-B OUT information will be used by other ADS-B IN equipped aircraft and by ATC."

Might also be worth reading ACAS-X for co-operative system integration into UAS

[Lima Juliet]

SJ

SIL = Source Integrity Level and at level 1 it is the lowest level of quality from a certified GNSS source. Most military aircraft have certified GNSS receivers in my experience. Oh, and many military aircraft have GNSS systems that can be more accurate than civilian systems if the selective availability is turned back on. A certified GNSS receiver isn’t that expensive and the £419 hand portable ADS B In/Out Skyecho 2 has one and so therefore can emit ADS-B at SIL=1.

Most ATC units or ACAS systems will ignore anything that is SIL=0.

i hope that helps?

LJ

[SlopJockey]

An ADS-B In/Out ACAS would need to know where it is but ADS-B Out going to TCAS has no need to know the integrity of the GNSS resolved position. See ACAS Link "ACAS II works independently of the aircraft navigation, flight management systems, and Air Traffic Control (ATC) ground systems. " and FAA piece above.

I feel we are straying towards area we should not in a public forum but it appears your understanding of Certified is quite different to mine. A GNSS receiver may have a Technical Standard Order (TSO) but Certification of the capability is different and where differing systems are installed and work collaboratively. The TSO is but part of the process as compliance with airworthiness regulations must be demonstrated.

[Bagheera S]

When Mode S was made made mandatory for Gliders in Holland, on good soaring days the number of returns swamped the SSR screens to the point the controllers couldn’t do there job effectively. So “mandatory glider transponder off zones” were quickly implemented..... Doh!

You really must be careful what you wish for and really think these things through. I pretty sure this finding put pay to the plans to the enforced Mode S for everybody. Self autonomous deconfliction, which everyone can see will be the way forward.

[Lima Juliet]

SJ

This is what one of the manufacturers of a portable ADS-B In/Out device states: Integrated GNSS SBAS Navigation. Utilizes TSO Certified uAvionix FYX GPS. Meets TSO-C199 Class B.

It appears to use “certified” and “TSO” in the same sentence and that chimes with my understanding.

An ADS-B In/Out ACAS would need to know where it is but ADS-B Out going to TCAS has no need to know the integrity of the GNSS resolved position. See ACAS Link "ACAS II works independently of the aircraft navigation, flight management systems, and Air Traffic Control (ATC) ground systems. " and FAA piece above.

I’m not sure I understand you here. To push out ADS-B you must have a position information for the Extended Squitter (ES) of Mode S. For TCAS II I understand that this must be SIL=1 or greater or it will simply ignore it - however, SIL=3 is needed for full TCAS functionality. To be able to resolve the other position on a display then your TCAS II will need to know its position to provide Hybrid Surveillance warnings. The advantage of Hybrid Surveillance is that ADS-B detections do not require the 1030Mhz interrogations as the ES is being pushed constantly like a radio on 1090Mhz.

That is how I understand it, anyway!

[SlopJockey]

TCAS works by plotting successive responses to interrogation to determine a track and a potential threat and estimates a closet point of approach. Altitude information is key in that solution, hence only TA when no Mode C/S. It is as I said about relativity and co-operation.

Regarding TSOs:

Extended Squitter Automatic Dependent Surveillance - Broadcast (ADS-B) and Traffic Information Service - Broadcast (TIS-B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz)

TSO-C166b PURPOSE. This technical standard order (TSO) is for manufacturers applying for a TSO authorization (TSOA) or letter of design approval (LODA). In it, we (the Federal Aviation Administration, or FAA) tell you what minimum performance standards (MPS) your 1090 MHz ADS-B and TIS-B equipment must first meet for approval and identification with the applicable TSO marking.

Manufacturers means Eqpt manufacturers such as Honeywell or Garmin, they can get eqpt assessed as meeting the TSO and it then is a commercially viable product. Aircraft designers, or other DOs then use this eqpt to install the systems in the aircraft they design and use the credit from the TSO rather than starting from scratch but they must get Certification (Airworthiness Approval).


From AC 20-165 Airworthiness Approval of Automatic Dependent Surveillance - Broadcast (ADS-B) Out Systems - 2-1. ADS-B System Approval Process.

a. This AC addresses the initial airworthiness approval through the type certification or supplemental type certification process of an ADS-B Out system that meets the equipment requirements of 14 CFR § 91.227.

c. ADS-B Out System Components. The ADS-B system is depicted in figure 1 and includes the ADS-B equipment, a position source, a barometric altitude source, an air-ground status source, a TCAS II source if the aircraft is equipped with TCAS II, an optional heading source, and all associated antennas and displays.

Para 3.7 (b) ADS-B Function Failure. The ADS-B system depends on a position source to provide the data to populate the ADS-B messages and reports. This position source or interface may fail and prevent the system from providing pertinent information to the ADS-B equipment. In this case, the ADS-B system cannot function, but there is not a failure of the ADS-B equipment. TSO-C166b and TSO-C154c require this condition to be annunciated. The ADS-B system should indicate this position source or interface failure independently of the ADS-B equipment failure annunciation. The flight manual must describe the means to interpret the difference between the device failure and function failure annunciations if the annunciations are not unique. The ADS-B function failure must not cause a TCAS II system failure.

As you recognise the intent of hybrid surveillance is to reduce the TCAS interrogation rate on 1030 Mhz, observed above as a problem with many gliders, through the judicious use of the ADS-B Out data provided via the Mode S extended squitter to discriminate no potential threat aircraft, without any degradation of the safety and effectiveness of the TCAS.

So degraded ADS-B out should not impact upon TCAS II operation as the fall back is the active interrogation it just means there is less automatic discrimination and greater number of interrogations

There are loads of resources if you look.

https://www.faa.gov/documentLibrary/...AC_20-151C.pdf
https://www.faa.gov/documentLibrary/...%20booklet.pdf
https://sesarju.eu/sites/default/fil...rveillance.pdf