I am working in a private airlines. We have some Dash-8 Q400 aircraft in our fleet. Recently a SB has been issued telling us to upgrade the Flight Management System from UNS-1E to UNS-1Ew.

Can anyone explain what are the advantages for upgrading the Flight Management System from UNS-1E to UNS-1Ew?


Here is my understanding of the update. As others I believe your primary source should be your OEM.

Main purpose: Ability to use SBAS procedures and navigation

The purpose of moving from UNS-1E to UNS-1Ew is getting the SBAS capability. From the UNS-1Ew manual:

The new “W” series of Universal Avionics Flight Management systems incorporate the Global Navigation Satellite System (GNSS) Space Based Augmentation System (SBAS) known in North America as the Wide Area Augmentation System (WAAS). Other SBAS systems in the world will also be incorporated.

SBAS details

SBAS means using WAAS, EGNOS and other GNSS augmentation systems. SBAS in short provides for correction of GNSS radio signal propagation errors in a limited area. This increases pseudo-ranging accuracy and positioning precision.

SBAS (space-based) is opposed to GBAS (ground-based) where correction broadcasting stations are on the ground, like the DGPS, a surveying GBAS with a positioning precision up to 10 cm.

EGNOS measuring network (SBAS for Europe area):

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Source: Wikipedia

Additional benefits of the update

From UASC documentation:

What else you get with an SBAS-FMS upgrade:

• Performance-Based Navigation (PBN) including Precision-Area Navigation (P-RNAV) compliance and Required Navigation Performance/Area Navigation (RNP/RNAV) up to 0.3 NM approach accuracy

• WAAS LPV / EGNOS APV, LNAV approaches

• Mode S Enhanced Surveillance support

• Accurate SBAS-GPS information provided to the onboard Terrain Awareness and Warning System/Enhanced Ground Proximity Warning System (TAWS/EGPWS) and Traffic Collision Avoidance System (TCAS)

• Large database capacity for worldwide navigation databases

You can read "The Benefits of SBAS" on UASC site.

And if you need more information the UNS-1Ew manual is also available.

  • $\begingroup$ Don't forget that ADS-B requires a WAAS capable receiver. $\endgroup$ – wbeard52 Dec 5 '16 at 1:19

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