"john smith" wrote in message
...
Does LSA require and electrical system?

No.

I have yet to see a handheld transponder for GA.

And you won't. The new system eliminates transponders.

There has to be a transmitter of some type installed to broadcast.

From: http://www.gisdevelopment.net/techno...s/ma04082c.htm


4.1 Automatic Dependent Surveillance (ADS)
In this, the aircraft automatically transmits, via data links, its
identification and 3-D position to the ATC unit. It allows controllers to
observe on a pseudo-radar display, the position of aircraft and possible
deviations from the assigned flight paths. The design of the ADS should
allow the implementation without disrupting ATS. It should also be
sufficiently flexible to adaptability to local requirement and ATS special
requirements, expandability, integration with new technology, provide
sufficient safety and switch over to other forms of ATS in case of failure
or degradation. It should also have the capability to provide a minimum
service to all duly equipped aircraft and become finally part of ATS
infrastructure that derives full advantage of the ADS.

4.1.a Automatic Dependent Surveillance ADS-A (Addressed)
This system operates only in the air-ground mode and at the request of the
ATC unit. It is the controller who determines which reports are necessary
for controlling each aircraft. The basic principle is given as:
Communication contracts must first be established between airborne equipment
and ground systems before being able to receive any ADS report. The
controller determines which report is necessary to control each aircraft in
the flight segments under the control of a given ATC unit. The issuance of
basic ADS report at periodic intervals is defined by the ground system with
one or more blocks of additional data containing specific information. ADS
report may contain geographically defined points, such as waypoints and
intermediate points, in addition to reports triggered by specific
occurrence. Certain types of airborne equipments have the capability to
maintain contracts with four or five ATC unit simultaneously. These aircraft
will also send automatic position reports, in keeping with ADS contracts
made by ground system. At given time or distance before reaching the
boundaries of the FIR, which can vary depending on the ground system. The
latter will immediately prepare and transmit ADS reports addressed to the
grounds system in keeping with the pre-established contracts. In some
system, the controller has the capability to replace the ADS contracts if
necessary. The ground system will issue the appropriate message to start the
modification of exiting contracts.

Automated ground systems can use the ADS position reports and other data
groups from the ADS message to provide automated flight tracking in
accordance with flight plan. Most automated ground system compares the
aircraft position reported by the ADS with the position foreseen by the
ground system, taken from the flight plan. The ground system will prepare
and show the controller the appropriate message in the event that the ADS
report does not match the position foresee by the ground system. This
monitoring capability makes it possible to verify whether the flight is
proceeding according to flight plan. Further more, aircrafts are equipped
with FAN-1A capable of doing their own monitoring and of making an automatic
report in case of significant flight variations, when so required by an
appropriate occurrence contract. The ground system will include, together
with the request for an ADS occurrence contract, the value that triggered
these reports.

4.1.b Automatic Dependent Surveillance Contracts ( ADS-C) :
There are three types of contract, each of them operating independently of
the others. They are periodic contract, occurrence contracts & demand
contracts. A request for a periodic contract defines the contract
requirements to be included in the reports and reporting frequency. Through
an uplink, an ATS unit initiates the periodic report request. This request
allows an ATS unit to include the optional data groups in the basic ADS
reports, also specifying the frequency of inclusion. The controller can
modify the periodic reporting average up and down in order to accommodate
special situations, such as traffic density. Information about the minimum
reporting averages recommended for each type of aircraft can be obtained
from the manufacturer's manual. Only one periodic contract can be
established. if another is to be established , then the previous contract
will be replaced . This periodic contract will remain in force until
modified or cancelled.

The occurrence contract specify a report request to be sent by the aircraft
if certain occurrence takes place e.g. variation in ascent or decent regime,
lateral deviation in flight path, change in altitude, change in reporting
point. Only one occurrence contract may be established each time between the
aircraft and the ground system even so, the contract may contemplate
different type of the occurrence. The demand contracts request is a single
request from the ground system for the airborne equipment to send an ADS
report containing the data specified in the request. A demand contact may be
requested by the ground system at any time. A request for such contract will
not affect any other that exists.

The emergency mode is activated or cancelled by the pilot only. Once
activated, the emergency mode connects the aircraft with all ground systems
that have established periodic or occurrence contracts with it. When pilot
cancels the emergency mode, the on board equipment will send a cancellation
message to each ground station that received this message.

4.2 Automatic Dependence Surveillance- Broadcast (ADS-B)
ADS-B is a new aeronautical surveillance concept by virtue of which the
aircraft transmits its position through data link. The position information
is received by near-by aircraft, which enables all users to be informed
about their own position and the position of all other nearby traffic. The
position information may be displayed in the cockpit of aircraft thus
equipped to allow for new possibility of detecting traffic. Ground vehicle
and facilities can also be equipped to receive and transmit position data,
making it possible to monitor all types of traffic through two-way data
links. In addition to position data, other data like aircraft identification
and speed (obtained from GNSS receiver) may be also transmitted. ADS-B will
play important role in the cockpit environment, and it will keep the pilot
informed about all the traffic vicinity of the airports. The cockpit display
is used to show the position and intentions of all aircrafts within a 200-NM
radius. This equipment is called cockpit display of traffic position (CDTI)
or traffic situation display (TSD).

However ADS-B allows keeping a visual display of all surrounding traffic. On
the ground, the ADS-B will offer ATC new surveillance capabilities at a
fraction of the cost of a conventional SSR. An ADS-B ground station is a
transmitter / receiver station without the complex and costly rotary antenna
radar systems. An ADS-B ground station does not need to make high-precision
measurements of the aircraft position, thus reducing the cost of the ground
equipment considerably. The ADS-B concept is independent of the type of link
used for data transmission. The information can be relayed by VHF or
satellites or SSR mode-S. Therefore ADS-B will be an advanced and relatively
low cost-system that will provide high quality flight surveillance
information, Low cost, flexibility in surveillance reporting, more precise
data capability to support new application,, identical surveillance
information to the all users, surveillance available for all phases of
flight. The ADS-B will also send a message to ground control unit within a
radius of 95 NM around the transmitting aircraft.

ADS messages contain the data like position, time, track, ground speed ,
vertical situation, magnetic heading, Mac number ( speed of the aircraft),
next route reporting point, estimated altitude at next reporting point,
second to the next reporting point, upper wind direction, upper wind
velocity and temperature. Moreover ATC using ADS information must have the
capability to automate the function like flight data validation, automatic
tracking, and direction of potential conflict, conflict resolution and
display of relevant processed data.