GPS approaches and display choices

[GravityHater]

An airplane has a mfd that will show either a Moving Map or an EHSI display.

The EHSI can toggle between FMS or VOR or LOC or ADF inputs. There is no other depiction on the panel of gps(fms) data. The FMS provides approved GPS-approach info.

T or F:
The airplane can be flown on instrument approaches in imc with only the moving map display, the pilot is not required to be looking at the EHSI.

I am requesting references to prove this to someone, whatever the answer is. Opinions, while interesting to me, will be discarded as what I am really in need of is referenced fact. Thanks for understanding this point.

 

[Donsa320]

An airplane has a mfd that will show either a Moving Map or an EHSI display.

The EHSI can toggle between FMS or VOR or LOC or ADF inputs. There is no other depiction on the panel of gps(fms) data. The FMS provides approved GPS-approach info.

T or F:
The airplane can be flown on instrument approaches in imc with only the moving map display, the pilot is not required to be looking at the EHSI.

I am requesting references to prove this to someone, whatever the answer is. Opinions, while interesting to me, will be discarded as what I am really in need of is referenced fact. Thanks for understanding this point.

I do not think you will find what you want but I can offer this. A long time ago, in France, an A320 was flying a VOR approach in what we call the VOR rose mode. In that mode the Nav display is just an HSI with VOR course deviation shown. No waypoints displayed. The approach had numerous stepdowns as the terrain was moutainous. The descents were being made manually, that is, with the vertical speed knob, no vertical nav. The crew missed an intermediate level off and hit the terrain with fatalities. The aircraft was not equipped with GPWS as France had no national requirement for it. The official cause was determined to be using the rose mode was improper as it did not give the crew good awareness of the progress of the approach. Senior company officials went to prison for criminal lack of supervision.
Yes, all the intermediate stepdowns were displayed on the MCDU but the investigation said that was not good enough.

I would agree.

 

[cjdriver]

The lack of regulation in this matter would indicate no preference.

 

[ProFracPilot]

T or F:
The airplane can be flown on instrument approaches in imc with only the moving map display, the pilot is not required to be looking at the EHSI.

I am requesting references to prove this to someone, whatever the answer is.

For which approach? You don't differentiate between VHF, ADF and FMS approaches. But the answer you are seeking will be found in the Approved Flight Manual, or the the AFM Supplement for that given airplane.

Now, you can discard this if you want as I don't have a direct reference (perhaps AC 20-130 could provide some insight): The udate rate of the MFD "Moving Map" is insufficient to be used as the only source for any navigational guidance.

 

[LJ45]

For which approach? You don't differentiate between VHF, ADF and FMS approaches. But the answer you are seeking will be found in the Approved Flight Manual, or the the AFM Supplement for that given airplane.

Now, you can discard this if you want as I don't have a direct reference (perhaps AC 20-130 could provide some insight): The udate rate of the MFD "Moving Map" is insufficient to be used as the only source for any navigational guidance.

I agree, your AFM for that aircraft, supplement or approved avionics manual should have restrictions, if any.

 

[GravityHater]

Sorry; GPS approaches (see title)
will check manual
thank you.

 

[GravityHater]

Here is the manual
I can find nothing discussing it.
https://www.bendixking.com/servlet/...me=/TechPubs/repository/006-08845-0000_10.pdf

 

[ProFracPilot]

Ok. Is your GNS-Xls an OEM installation or was it an STC'd upgrade to the aircraft? Either way you should have an AFM Supplement that contains, among other things, Operating Limitations. These limitations will tell you what modes and displays can be used, and when you can use them. It will also contain a statement worded something like: "When in use, the Honeywell GNS-Xls Operator's Manual P/N 006-08845-0000 will be made immediately available to the flight crew". This manual alone is not the AFM Supplement or the "Approved" document that results from an STC'd installation. Honeywell doesn't know how your unit is interfaced to your EFIS or autopilot. The answers you seek are in an AFM Supplement for that particular airplane. If you can't find it there, contact either the aircraft manufacturer's avionics tech people; or if it was an STC upgrade to the airplane, the folks that certified the installation.

Hope this helps.

Pfp

 

[ksu_aviator]

Short answer: NO

Proof:

According to Terps, one of the requirements for executing a GPS approach is...

• ​

Course deviation indicator (CDI)
scale sensitivity. The spec requires automatic
scaling of +/- 5 nm for en route
mode, +/- 1 nm for terminal mode, and
+/- 0.3 nm for approach mode.
Terminal mode is intended to be active
for the initial approach segment
when within 30 miles of the airport, and
for the intermediate and missed approach
segments. Approach mode is
only for the final approach segment,
with auto-transition from terminal to
approach CDI sensitivity starting two
miles prior to the final approach
waypoint (FAWP). All other segments,
including feeder routes, airways and
initial approach segments more than 30
miles from the airport are intended to​

be flown with en route CDI sensitivity.

http://www.terps.com/ifrr/jan97.pdf

Since your moving map does not have a CDI, you cannot use it as the sole reference for executing an approach.

I'm positive you can't even use it as sole reference for en route operations, but I don't feel like finding a reference for that.

Confession: I peak at it to make sure I'm right But, isn't that exactly what it is for?