Service Information Letter
SIL Number: 606-00182-001
To: Owners, Operators, and Installers of IFD540 Nav/Com/GPS
Subject: IFD540 OBS Calibration
This Service Information Letter (SIL) advises owners, operators,
and installers of Avidyne IFD 540 Nav/Com/GPS of an alternate
Purpose: means of evaluating OBS calibration and VOR navigation
airworthiness and of a possible hardware update that may
improve OBS accuracy in some installations.
Revision: 01
Date: Sept 25, 2014
Problem Description
This Service Information Letter (SIL) advises owners, operators, and installers of IFD540
Nav/Com/GPS of an alternate means of establishing acceptable VOR navigation performance in
the event that OBS calibration criteria cannot be met as described in IFD540 Installation Manual
600-00299-000.
Section 7.5.7 Main CDI/OBS Config Page (Page 6 of 10) of IFD540 Installation Manual 60000299-000 (Rev 00 or later FAA approved revision) indicates that the OBS on the navigation
indicator should be set to 150 degrees and calibrated to the IFD540. This section also indicates
that OBS accuracy should be checked. The indicated OBS value on the IFD540 calibration
screen should be checked against the set OBS value on the navigation indicator on every major
(30deg) heading. The IM procedure sets criteria of +/-2 degrees for this check. IFD540
calibration with specific navigation indicators may exceed 2 degrees on one or more tested
headings.
Solution:
Please check the “Effectivity Section” below or contact Avidyne Technical Support to determine
if the IFD540 in question is eligible for MOD #2, a hardware update that may improve OBS
accuracy in some installations.
Otherwise, in instances where the OBS setting does not match the displayed value on the
IFD540 OBS calibration display within 2 degrees for every 30 deg heading, a VOR check may
be used to verify correct function of the navigation receiver and navigation indicator. A VOR
Equipment Check as described in 14CFR 91.171 may be performed. This allows the use of a
VOT, calibrated VOR test set (e.g. IFR 4000), or airborne check. Criteria are identified in 91.171
(excerpted below). If the VOR check does not meet indicated accuracy criteria please contact
Avidyne Technical Support for further assistance.
Revision: 01
Date: Sept 25, 2014
606-00182-001
Page 1 of 3
Service Information Letter
Sec. 91.171
VOR equipment check for IFR operations.
(a) No person may operate a civil aircraft under IFR using the VOR system of radio navigation
unless the VOR equipment of that aircraft-(1) Is maintained, checked, and inspected under an approved procedure; or
(2) Has been operationally checked within the preceding 30 days, and was found to be
within the limits of the permissible indicated bearing error set forth in paragraph (b) or (c) of
this section.
(b) Except as provided in paragraph (c) of this section, each person conducting a VOR check
under paragraph (a)(2) of this section shall-(1) Use, at the airport of intended departure, an FAA-operated or approved test signal or a
test signal radiated by a certificated and appropriately rated radio repair station or, outside
the United States, a test signal operated or approved by an appropriate authority to check
the VOR equipment (the maximum permissible indicated bearing error is plus or minus 4
degrees); or
(2) Use, at the airport of intended departure, a point on the airport surface designated as a
VOR system checkpoint by the Administrator, or, outside the United States, by an
appropriate authority (the maximum permissible bearing error is plus or minus 4 degrees);
(3) If neither a test signal nor a designated checkpoint on the surface is available, use an
airborne checkpoint designated by the Administrator or, outside the United States, by an
appropriate authority (the maximum permissible bearing error is plus or minus 6 degrees); or
(4) If no check signal or point is available, while in flight-(i) Select a VOR radial that lies along the centerline of an established VOR airway;
(ii) Select a prominent ground point along the selected radial preferably more than 20
nautical miles from the VOR ground facility and maneuver the aircraft directly over the
point at a reasonably low altitude; and
(iii) Note the VOR bearing indicated by the receiver when over the ground point (the
maximum permissible variation between the published radial and the indicated bearing is
6 degrees).
(c) If dual system VOR (units independent of each other except for the antenna) is installed in
the aircraft, the person checking the equipment may check one system against the other in
place of the check procedures specified in paragraph (b) of this section. Both systems shall be
tuned to the same VOR ground facility and note the indicated bearings to that station. The
maximum permissible variation between the two indicated bearings is 4 degrees.
(d) Each person making the VOR operational check, as specified in paragraph (b) or (c) of this
section, shall enter the date, place, bearing error, and sign the aircraft log or other record. In
addition, if a test signal radiated by a repair station, as specified in paragraph (b)(1) of this
section, is used, an entry must be made in the aircraft log or other record by the repair station
certificate holder or the certificate holder's representative certifying to the bearing transmitted by
the repair station for the check and the date of transmission.
Revision: 01
Date: Sept 25, 2014
606-00182-001
Page 2 of 3
Service Information Letter
Effectivity
IFD540 with Release 10.0.0 or 10.0.1 Software
If not already applied, the following IFD540 units are eligible for MOD 2, a hardware update that
may improve OBS accuracy in some installations.
700-00182-() part
Number & Revision
700-00182-000 Rev 00
700-00182-002 Rev 00
700-00182-100 Rev 00
700-00182-102 Rev 00
Containing Assembly 710-00310-000
(A label indicating '710' part number and revision can be found
on the underside of the unit bezel)
710-00310-000 Rev 06 or earlier
710-00310-000 Rev 06 or earlier
710-00310-100 Rev 06 or earlier
710-00310-100 Rev 06 or earlier
Accomplishment Instructions:
No Avidyne changes are necessary to perform a VOR check.
Application of MOD 2 may only be performed by Avidyne or and Avidyne-Authorized Service
Facility.
Warranty Information:
Not Applicable.
Contact Information:
Avidyne Technical Support
1-888-723-7592
[email protected]
www.avidyne.com/support
Avidyne Corporation
55 Old Bedford Road
Lincoln, MA 01773
Revision: 01
Date: Sept 25, 2014
606-00182-001
Page 3 of 3