Helicopter reporting: possible with MLAT or Position-only ?


#1

Hello,
This is my first message, I searched through the forums, please point me to existing discussions/wiki if I overlooked something.
I’m trying to understand if my PiAware 2.1(5) can report helicopters. From searching the web, it appears helicopters aren’t using ADS-B.
Can PiAware report helicopters using MLAT and/or Position-only flights ?

A heliport is located 200 meters from where I live and helicopters fly over the house so I’m sure I would “get” some data. Issue is: I don’t know if I can receive and process this data.


#2

I occasionally see ADS-B equipped helicopters but many do seem to be Mode S only. You would need mlat to find a position for them.

You may have trouble getting enough coverage for good mlat, though, since they tend to be low-flying and at lower altitudes, the effective receiver range is much smaller, so you need a higher density of receivers to get the overlapping coverage that mlat requires.

Your site does seem to have working mlat, so you should be seeing mlat results on your local map already.


#3

Thanks, is there any way to filter helicopters in the detected “flights” ? Either specific icon in the local map or flight number (e.g could start with letter “H” but again I have no prior knowledge).


#4

The problem is, how do you identify a helicopter? There’s generally nothing in the received messages that identifies them as one. You’d have to go back to the aircraft registries to work it out.

There is an aircraft category in ADS-B messages that can be “rotorcraft”, and dump1090-mutability will use a different icon in that case. But that only works with ADS-B, and the category is very rarely set, it is almost always the generic “no information” category.


#5

Thanks, that’s what I feared, there’s no obvious information, I was hoping that aircraft registries could be coded with such an information within (simplistic: H for helicopter, P for plane, etc.) but well, nope.


#6

Dump1090 from Mutability (as per obj)shows helicopters with a little helicopter Icon. I see the NYPD Helicopter every day. They likely use it for TCAS as they fly is some very busy airspace.

In the U.S., I think only ATP Helicopters require mode S or ADS-B at the moment.
I live in Brooklyn, NY, with helicopters taking off maybe 100 times a day at the Wall St/Downtown Heliport. Mostly for tourists, a few DHL courriers and a few S76 (Loud and twin engines).

In 2020, when ADS-B is mandatory in the U.S. for most controlled airspace, you will see a lot more.
I expect many will opt for the 978Mhz UAT as it provides for weather and other features but it probably will depend on the cost. 978UAT will satisfy the requirement of aircraft that don’t go above FL180 (Class A Airspace in the U.S.). Most Helicopters don’t go anywhere near FL180.

UAT 978 is only used in the U.S.(at the moment) so aircraft that travel to Canada or Mexico may go for the 1090ES setup.
Flight aware makes money from Commercial flights. They may add these features to their code, however, as they won’t make money from it, I don’t expect too much development.

I have dump978 running and haven’t seen a UAT978 hit in a few days(only ground station messages)
I expect to see a lot more traffic by 2020.


#7

Thanks, this is useful to know. JavaScript shows rotorcraft as an aircraft type, as per obj, would be via ADS-B:
github.com/mutability/dump1090/ … ct.js#L176

Not sure what this code means though it mentions a helicopter:
github.com/mutability/dump1090/ … e_s.c#L904

(I edited as I later understood obj had mentioned this, I had failed to understand mutability was referring to a Github fork)


#8

Are there aircrafts “signatures” for which we can improve a database ? For e.g if I visually spot a helicopter, can I submit the matching dump to a database to enrich it ? Not sure if it makes sense for aircrafts, this is how a simple IDS (Intrusion Detection System) works.


#9

I believe that FA has access to the database.

It is simply that most GA aircraft in the US only need Mode A/C transponders. These do not give out any aircraft details. They only transmit their altitude and Squawk ID when “Painted” by radar and in Mode C.
You could do something with MLAT but it would only provide location and altitude unless they were on a flight plan. If on a flight plan, it may be possible to match it up to more information.

You need Mode S or ADS-B(Mode S/ES or UAT 978) to get an aircraft ID.

In Europe there are more requirements for Mode S and ADS-B transponders.
There are also other systems for gliders. I believe these are somewhat low power as gliders don’t normally have power.

I think Australia mandated the installation of ADS-B on new GA aircraft recently.