AMCP/WGW
Flimsy 1
COMMENTS ON COST BASIS FOR COMPARISON OF ALTERNATIVE ADS-B
DATA LINKS
Stephen Heppe / ADSI, Inc.
This flimsy identifies certain issues regarding the cost/benefit assessment for alternative
ADS-B data links, which were highlighted after consideration of AMCP/WGW WP13
and the summary cost/benefit data provided by US/FAA/ASD-400.
In regard to the total unit cost data provided by US FAA, page 9, the cost data for
scenarios involving VDL Mode 4 appear to be higher than expected based on our own
inputs to the FAA. This could be due to averaging of inputs from other manufacturers;
however, this averaging process may be incorrect from a market analysis standpoint (e.g.,
a more efficient airborne integration concept could quickly dominate and drive down
overall costs for the industry).
ADSI, Inc. provided cost data for low/mid GA and air transport user classes (WP32
Annex A describes the general integration concept).

For low/mid GA, our cost assessment was on the order of US$13,300 per aircraft.
This is roughly US$6000 lower than assessed by the FAA. Our assessed cost is within
10% of the FAA’s assessed cost for UAT – consistent with the general perception that
the specific link technology would not be a significant cost driver compared to other
cost elements associated with ADS-B.

For transport category users, ADSI, Inc. has previously sold dual-channel VDL Mode
4 radios at approximately US$20,000 each; significant price reductions for nextgeneration products are expected. Our proposed airborne integration concept does not
require any new antennas and does not result in any net increase in avionics LRUs.
Therefore, the cost deltas between cost scenarios for AT users, ranging from
US$50,000 to US$100,000 for retrofit and US$40,000 for forward-fit, do not seem to
be reasonable.
The cost differences are significant on an absolute and percentage basis, and indicate that
further explanation and/or analysis is warranted. A simple averaging of cost data from
different manufacturers is not appropriate given these large differences.
The concept of a hybrid architecture, using dual ADS-B systems and integrating VDL
Mode 4 with VHF communications, has not been fully assessed from a cost standpoint.
This architecture (ref. WP32) would appear to offer significant cost savings considering
all CNS domains together, and this type of overall analysis is recommended for future
consideration by ICAO (i.e., since airspace users and service providers are sensitive to
total cost).
AMCP/WGW
Flimsy 1
Further explanation of certification costs is hereby requested. It is not clear why the
certification costs for VDL Mode 4, by aircraft type, are higher than for the L-band
systems.
Further explanation of equipage timelines is hereby requested. The L-band systems were
assumed to follow deployment schedules with initial deployment circa 2006 and “final
fleet equipage levels” achieved circa 2014 for the transport fleet. Conversely, VDL Mode
4 was assumed to follow a deployment schedule with initial deployment circa 2010 and
“final fleet equipage level” achieved circa 2019. These assumptions seem to be overly
optimistic for UAT (which does not yet have SARPs) and overly pessimistic for VDL
Mode 4 (SARPs already approved and adopted). Implementation plans for VDL Mode 4
already exist in Europe and Russia, as well as elsewhere, and orders in excess of 1000
units have already been placed with at least one European manufacturer.
The equipage schedules have an impact on the net present value of assessed benefits, and
must be evaluated more accurately in order to ensure a proper cost/benefit comparison
among ADS-B link alternatives.
The assumed “effectiveness multipliers” for VDL Mode 4 are lower than for the L-band
alternatives, perhaps because the TLAT results incorrectly penalized VDL Mode 4 in
certain applications. The differential is 20%, which may be significant in the overall
assessment. These effectiveness multipliers must be adjusted and aligned given the issues
already identified with the TLAT results.
The cost/benefit assessment makes specific costing assumptions to support surface
operations.1 Hence, the ability of the various links to support these operations, and the
benefits accruing therefrom, should be assessed and included in the link decision process
as well. VDL/4 should be given the benefit for a 1 second update period (95%) on the
airport surface and for parallel approach (the MASPS requirement is 1.5 seconds (95%)).
The UAT does not appear to fully satisfy these requirements.
In regard to the preliminary cost comparison contained in WP13 (Table 1), these data
appear to be based on the summary data discussed above. As such, this table should be
revised once the issues noted above have been adequately addressed. As noted above, the
significant cost deltas between alternatives seem to be unrealistic given the general
perception that the link technology would not significantly affect overall ADS-B system
costs.
1
Your cost model assumes that the 175 largest airports implement multi-lateration, and other airports have
two ADS-B ground stations each, in order to support surface operations.