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01-09-2020, 07:16 AM
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Join Date: Jan 2005
Location: Tampa, FL
Posts: 2,861
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Quote:
Originally Posted by Mark H
The Advisory Circular 90-108 addresses the legality of using an RNAV as alternate means of navigation. The GPS may be used as the means of navigation except for the final approach segment or as a substitute for a LOC. You can legally fly the DME arc using only the GPS until you get inbound at the FAF.
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The AIM also has verbiage to that affect:
4. Pilots may not substitute for the NAVAID (for example,
a VOR or NDB) providing lateral guidance for the final
approach segment. This restriction does not refer to
instrument approach procedures with ?or GPS? in the title
when using GPS or WAAS. These allowances do not apply
to procedures that are identified as not authorized (NA)
without exception by a NOTAM, as other conditions may
still exist and result in a procedure not being available. For
example, these allowances do not apply to a procedure
associated with an expired or unsatisfactory flight
inspection, or is based upon a recently decommissioned
NAVAID.
The Martin State VOR/DME RWY 15 is a good example of an IAP where you can't sub GPS: https://aeronav.faa.gov/d-tpp/2001/05222VDTZ15.PDF
__________________
Todd "I drink and know things" Stovall
PP ASEL-IA
RV-10 N728TT - Flying!
WAR EAGLE!
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01-13-2020, 02:33 PM
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Join Date: Dec 2006
Location: Atlanta, GA
Posts: 1,231
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Quote:
Originally Posted by RV8iator
Select NEAREST, VOR and select the VOR you are using and it displays the bearing/distance to that station.
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You may wish to verify that with your local FSDO or other knowledgeable authority. I am NOT one, most of my instrument knowledge is decades old and I don't fly single engine IFR anymore.
This issue came up decades ago. A DME arc at 30,000 feet is a tighter circle than a DME arc at 3,000 feet, because the DME measures line of sight distance to the beacon. GPS distance to a fix, even if it is a VOR/DME, gives you the LATERAL distance to the fix - so up high your arc may be well outside what was intended by TERPS, and as a result may put you INTO airspace the arc was meant to avoid.
My recollection is that if you are not equipped with the correct type of equipment for the approach, you cannot fly it. Pick an equivalent GPS approach if one is available, otherwise request vectors to an approach point for a GPS approach that does not include the arc.
There was talk of equipping GPS receivers with a calculated "Virtual DME" reading, but I've never seen that materialize on any of the Garmins I've flown with.
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01-13-2020, 02:37 PM
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Join Date: Dec 2006
Location: Atlanta, GA
Posts: 1,231
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Quote:
Originally Posted by Auburntsts
Can't speak to the GTN's "Only for monitoring" annunciation, but the AIM specially allows you to fly the approach with GPS as a DME substitution without monitoring the underlining navaid:
1−2−3. Use of Suitable Area Navigation
(RNAV) Systems on Conventional
Procedures and Routes
2. Use of a suitable RNAV system as an
Alternate Means of Navigation when a VOR, DME,
VORTAC, VOR/DME, TACAN, NDB, or compass
locator facility including locator outer marker and
locator middle marker is operational and the
respective aircraft is equipped with operational
navigation equipment that is compatible with
conventional navaids. For example, if equipped with
a suitable RNAV system, a pilot may fly a procedure
or route based on operational VOR using that RNAV
system without monitoring the VOR.
c. Uses of Suitable RNAV Systems. Subject to
the operating requirements, operators may use a
suitable RNAV system in the following ways.
1. Determine aircraft position relative to, or
distance from a VOR (see NOTE 6 below), TACAN,
NDB, compass locator, DME fix; or a named fix
defined by a VOR radial, TACAN course, NDB
bearing, or compass locator bearing intersecting a
VOR or localizer course.
2. Navigate to or from a VOR, TACAN, NDB,
or compass locator.
3. Hold over a VOR, TACAN, NDB, compass
locator, or DME fix.
4. Fly an arc based upon DME.
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Similar to my response to the above concerning flying a DME arc - GPS is not listed in your post as an "alternate means" of navigating DME approaches. GPS gives you lateral distance, not orthoganal distance - and at 25,000' can put your arc so much further from the fix that you end up INSIDE an airspace meant to be avoided by the arc.
It may be that the GPS actually displays the correct arc, but if you don't want to bust a checkride verify whether the substitution is legal with someone smarter than me.
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01-13-2020, 02:58 PM
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Join Date: Jan 2005
Location: Tampa, FL
Posts: 2,861
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Quote:
Originally Posted by breister
Similar to my response to the above concerning flying a DME arc - GPS is not listed in your post as an "alternate means" of navigating DME approaches. GPS gives you lateral distance, not orthoganal distance - and at 25,000' can put your arc so much further from the fix that you end up INSIDE an airspace meant to be avoided by the arc.
It may be that the GPS actually displays the correct arc, but if you don't want to bust a checkride verify whether the substitution is legal with someone smarter than me.
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It is perfectly legal to fly a DME Arc IAP with an IFR GPS. I didn’t mention the relevant paras for GPS substitution because I thought it was understood that TSO’d GPS systems were an approved RNAV alternate means and I didn’t want to end up quoting lots of AIM paragraphs. But here it is:
b. Types of RNAV Systems that Qualify as a Suitable RNAV System. When installed in accordance with appropriate airworthiness installation requirements and operated in accordance with applicable operational guidance (for example, aircraft flight manual and Advisory Circular material), the following systems qualify as a suitable RNAV system:
1. An RNAV system with TSO−C129/ −C145/−C146 equipment, installed in accordance with AC 20−138, Airworthiness Approval of Global Positioning System (GPS) Navigation Equipment for Use as a VFR and IFR Supplemental Navigation System, or AC 20−130A, Airworthiness Approval of Navigation or Flight Management Systems Integrat- ing Multiple Navigation Sensors, and authorized for instrument flight rules (IFR) en route and terminal operations (including those systems previously qualified for “GPS in lieu of ADF or DME” operations), or
2. An RNAV system with DME/DME/IRU inputs that is compliant with the equipment provisions of AC 90−100A, U.S. Terminal and En Route Area Navigation (RNAV) Operations, for RNAV routes. A table of compliant equipment is available at the following website: http://www.faa.gov/about/office_org/ headquarters_offices/avs/offices/afs/afs400/afs47 0/policy_guidance/
NOTE−
Approved RNAV systems using DME/DME/IRU, without GPS/WAAS position input, may only be used as a substitute means of navigation when specifically authorized by a Notice to Airmen (NOTAM) or other FAA guidance for a specific procedure. The NOTAM or other FAA guidance authorizing the use of DME/DME/IRU systems will also identify any required DME facilities based on an FAA assessment of the DME navigation infrastructure.
c. Uses of Suitable RNAV Systems. Subject to the operating requirements, operators may use a suitable RNAV system in the following ways.
1. Determine aircraft position relative to, or distance from a VOR (see NOTE 6 below), TACAN, NDB, compass locator, DME fix; or a named fix defined by a VOR radial, TACAN course, NDB bearing, or compass locator bearing intersecting a VOR or localizer course.
2. Navigate to or from a VOR, TACAN, NDB, or compass locator.
3. Hold over a VOR. TACAN, NDB, compass locator, or DME fix.
4. Fly an arc based upon DME.
NOTE−
1. The allowances described in this section apply even when a facility is identified as required on a procedure (for example, “Note ADF required”).
2. These operations do not include lateral navigation on localizer−based courses (including localizer back−course guidance) without reference to raw localizer data.
3. Unless otherwise specified, a suitable RNAV system cannot be used for navigation on procedures that are identified as not authorized (“NA”) without exception by a NOTAM. For example, an operator may not use a RNAV system to navigate on a procedure affected by an expired or unsatisfactory flight inspection, or a procedure that is based upon a recently decommissioned NAVAID.
4. Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach segment. This restriction does not refer to instrument approach procedures with “or GPS” in the title when using GPS or WAAS. These allowances do not apply to procedures that are identified as not authorized (NA) without exception by a NOTAM, as other conditions may still exist and result in a procedure not being available. For example, these allowances do not apply to a procedure associated with an expired or unsatisfactory flight inspection, or is based upon a recently decommissioned NAVAID.
5. Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID monitored for final segment course alignment.
6. For the purpose of paragraph c,“VOR”includesVOR, VOR/DME, and VORTAC facilities and “compass locator” includes locator outer marker and locator middle marker.
__________________
Todd "I drink and know things" Stovall
PP ASEL-IA
RV-10 N728TT - Flying!
WAR EAGLE!
Last edited by Auburntsts : 01-13-2020 at 03:07 PM.
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01-13-2020, 09:14 PM
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Join Date: Nov 2006
Location: Saint Simons Island , GA
Posts: 1,523
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Quote:
Originally Posted by breister
You may wish to verify that with your local FSDO or other knowledgeable authority. I am NOT one, most of my instrument knowledge is decades old and I don't fly single engine IFR anymore.
This issue came up decades ago. A DME arc at 30,000 feet is a tighter circle than a DME arc at 3,000 feet, because the DME measures line of sight distance to the beacon. GPS distance to a fix, even if it is a VOR/DME, gives you the LATERAL distance to the fix - so up high your arc may be well outside what was intended by TERPS, and as a result may put you INTO airspace the arc was meant to avoid.
My recollection is that if you are not equipped with the correct type of equipment for the approach, you cannot fly it. Pick an equivalent GPS approach if one is available, otherwise request vectors to an approach point for a GPS approach that does not include the arc.
There was talk of equipping GPS receivers with a calculated "Virtual DME" reading, but I've never seen that materialize on any of the Garmins I've flown with.
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Certified (TSO?d) gps navigators are certainly legal to use until the final segment on VOR approaches.
Second comment...show me an arc approach you would fly at 30?000 feet and worry about TERPS.
All the pertinent info about legally using GPS is shown in a post above quoting the AIM.
__________________
Jerry "Widget" Morris
RV 8, N8JL, 3,000+ hours on my 8.
VAF #818
Saint Simons Island, GA. KSSI
PIF 2008, 2009, 2010, 2011,2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020
 I just wish I could afford to live the way I do
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01-14-2020, 11:38 AM
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Join Date: Dec 2006
Location: Atlanta, GA
Posts: 1,231
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Quote:
Originally Posted by Auburntsts
It is perfectly legal to fly a DME Arc IAP with an IFR GPS. I didn?t mention the relevant paras for GPS substitution because I thought it was understood that TSO?d GPS systems were an approved RNAV alternate means and I didn?t want to end up quoting lots of AIM paragraphs. But here it is:
b. Types of RNAV Systems that Qualify as a Suitable RNAV System. When installed in accordance with appropriate airworthiness installation requirements and operated in accordance with applicable operational guidance (for example, aircraft flight manual and Advisory Circular material), the following systems qualify as a suitable RNAV system:
1. An RNAV system with TSO−C129/ −C145/−C146 equipment, installed in accordance with AC 20−138, Airworthiness Approval of Global Positioning System (GPS) Navigation Equipment for Use as a VFR and IFR Supplemental Navigation System, or AC 20−130A, Airworthiness Approval of Navigation or Flight Management Systems Integrat- ing Multiple Navigation Sensors, and authorized for instrument flight rules (IFR) en route and terminal operations (including those systems previously qualified for ?GPS in lieu of ADF or DME? operations), or
2. An RNAV system with DME/DME/IRU inputs that is compliant with the equipment provisions of AC 90−100A, U.S. Terminal and En Route Area Navigation (RNAV) Operations, for RNAV routes. A table of compliant equipment is available at the following website: http://www.faa.gov/about/office_org/ headquarters_offices/avs/offices/afs/afs400/afs47 0/policy_guidance/
NOTE−
Approved RNAV systems using DME/DME/IRU, without GPS/WAAS position input, may only be used as a substitute means of navigation when specifically authorized by a Notice to Airmen (NOTAM) or other FAA guidance for a specific procedure. The NOTAM or other FAA guidance authorizing the use of DME/DME/IRU systems will also identify any required DME facilities based on an FAA assessment of the DME navigation infrastructure.
c. Uses of Suitable RNAV Systems. Subject to the operating requirements, operators may use a suitable RNAV system in the following ways.
1. Determine aircraft position relative to, or distance from a VOR (see NOTE 6 below), TACAN, NDB, compass locator, DME fix; or a named fix defined by a VOR radial, TACAN course, NDB bearing, or compass locator bearing intersecting a VOR or localizer course.
2. Navigate to or from a VOR, TACAN, NDB, or compass locator.
3. Hold over a VOR. TACAN, NDB, compass locator, or DME fix.
4. Fly an arc based upon DME.
NOTE−
1. The allowances described in this section apply even when a facility is identified as required on a procedure (for example, ?Note ADF required?).
2. These operations do not include lateral navigation on localizer−based courses (including localizer back−course guidance) without reference to raw localizer data.
3. Unless otherwise specified, a suitable RNAV system cannot be used for navigation on procedures that are identified as not authorized (?NA?) without exception by a NOTAM. For example, an operator may not use a RNAV system to navigate on a procedure affected by an expired or unsatisfactory flight inspection, or a procedure that is based upon a recently decommissioned NAVAID.
4. Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach segment. This restriction does not refer to instrument approach procedures with ?or GPS? in the title when using GPS or WAAS. These allowances do not apply to procedures that are identified as not authorized (NA) without exception by a NOTAM, as other conditions may still exist and result in a procedure not being available. For example, these allowances do not apply to a procedure associated with an expired or unsatisfactory flight inspection, or is based upon a recently decommissioned NAVAID.
5. Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID monitored for final segment course alignment.
6. For the purpose of paragraph c,?VOR?includesVOR, VOR/DME, and VORTAC facilities and ?compass locator? includes locator outer marker and locator middle marker.
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Thanks for the info. Things have certainly changed!
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01-14-2020, 11:39 AM
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Join Date: Dec 2006
Location: Atlanta, GA
Posts: 1,231
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Quote:
Originally Posted by RV8iator
Certified (TSO?d) gps navigators are certainly legal to use until the final segment on VOR approaches.
Second comment...show me an arc approach you would fly at 30?000 feet and worry about TERPS.
All the pertinent info about legally using GPS is shown in a post above quoting the AIM.
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As I said, my knowledge is old and apparently has been superseded. Thanks for the update.
The 30,000' was simply an exaggerated example to illustrate the difference. I rarely got that high in Phantoms, we usually cruised around FL250.
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01-14-2020, 02:00 PM
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Join Date: Jan 2005
Location: Tampa, FL
Posts: 2,861
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And back to one of the original questions in this thread about displaying the distance to the VOR that you?re flying the ARC around on the GTN. When you display the map on a GTN there are 4 user controlled data fields? one in each corner of the map. One of the choices is ?VOR/LOC - Tuned VOR/LOC Info?. Select that, tune the applicable NAVAIDs freq into the Nav radio and blam, the radial and distance is displayed right there on the moving map while the GPS navigates to the arc?s exit waypoint.
__________________
Todd "I drink and know things" Stovall
PP ASEL-IA
RV-10 N728TT - Flying!
WAR EAGLE!
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01-14-2020, 02:22 PM
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Join Date: Jun 2012
Location: Frederick, MD
Posts: 821
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Quote:
Originally Posted by Auburntsts
Can't speak to the GTN's "Only for monitoring" annunciation, but the AIM specially allows you to fly the approach with GPS as a DME substitution without monitoring the underlining navaid:
1−2−3. Use of Suitable Area Navigation
(RNAV) Systems on Conventional
Procedures and Routes
2. Use of a suitable RNAV system as an
Alternate Means of Navigation when a VOR, DME,
VORTAC, VOR/DME, TACAN, NDB, or compass
locator facility including locator outer marker and
locator middle marker is operational and the
respective aircraft is equipped with operational
navigation equipment that is compatible with
conventional navaids. For example, if equipped with
a suitable RNAV system, a pilot may fly a procedure
or route based on operational VOR using that RNAV
system without monitoring the VOR.
c. Uses of Suitable RNAV Systems. Subject to
the operating requirements, operators may use a
suitable RNAV system in the following ways.
1. Determine aircraft position relative to, or
distance from a VOR (see NOTE 6 below), TACAN,
NDB, compass locator, DME fix; or a named fix
defined by a VOR radial, TACAN course, NDB
bearing, or compass locator bearing intersecting a
VOR or localizer course.
2. Navigate to or from a VOR, TACAN, NDB,
or compass locator.
3. Hold over a VOR, TACAN, NDB, compass
locator, or DME fix.
4. Fly an arc based upon DME.
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Yes, but still need DME and VOR equipment on the aircraft and operational.
__________________
Dan Morris
Frederick, MD
PA28-140
Hph 304CZ
RV6 built and sold
N199EC RV6A flying
Learn the facts. "Democracy dies in darkness"
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01-14-2020, 03:04 PM
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Join Date: Jan 2005
Location: Tampa, FL
Posts: 2,861
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Quote:
Originally Posted by RVDan
Yes, but still need DME and VOR equipment on the aircraft and operational.
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I don’t think that’s completely true. It is true non-WAAS but I think there’s an out for WAAS IFR GPS’s:
2) Aircraft using un-augmented GPS (TSO-C129() or TSO-C196()) for navigation under IFR must be equipped with an alternate approved and operational means of navigation suitable for navigating the proposed route of flight. (Examples of alternate navigation equipment include VOR or DME/DME/IRU capability). Active monitoring of alternative navigation equipment is not required when RAIM is available for integrity monitoring. Active monitoring of an alternate means of navigation is required when the GPS RAIM capability is lost.
however
2) Ground−based navigation equipment is not required to be installed and operating for en route IFR operations when using GPS/WAAS navigation systems. All operators should ensure that an alternate means of navigation is available in the unlikely event the GPS/WAAS navigation system becomes inoperative.
9. Unlike TSO−C129 avionics, which were certified as a supplement to other means of navigation, WAAS avionics are evaluated without reliance on other navigation systems. As such, installation of WAAS avionics does not require the aircraft to have other equipment appropriate to the route to be flown. (See paragraph 1−1−17 d for more information on equipment requirements.)
[Note the above paras are talking about TSO 145/146 WAAS boxes like the GTN]
__________________
Todd "I drink and know things" Stovall
PP ASEL-IA
RV-10 N728TT - Flying!
WAR EAGLE!
Last edited by Auburntsts : 01-14-2020 at 03:13 PM.
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