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Replacing GNS530/430W to take advantage of VNAV in my Jetprop

This is not fully solved even on big jets (which normally have loads of spare power); their APs do VNAV but AIUI you cannot program a profile of multiple steps. Only the immediate step can be programmed.

Don’t know about big jets but the PC24 has no problem flying multi-step climbs in VNAV and FMS speed mode up to service ceiling. SIDs are flown customarily in VNAV with the autopilot flying the SID leveloffs as published and with the highest step altitude preselected (as preselect alt overrides FMS altitude).

T28
Switzerland

Can you program interleaved climbs and descents?

Administrator
Shoreham EGKA, United Kingdom

Yes, VNAV will follow whatever target altitude you load in the FMS for a specific waypoint as long as it is not above alt sel.

T28
Switzerland

I have now upgraded my GNS530W/430W units to IFD550/440 and as mentioned in the ForeFlight v Garmin thread I have been able to fly coupled LNAV/VNAV and LNAV+V approaches with my KFC225 autopilot. It works as advertised and I think Avidyne deserve credit for reverse engineering the GNS install to provide such a relatively straightforward path to the next generation of avionics without having to butcher the existing panel.

Avidyne have released v10.3 of the IFD simulator to give an advanced preview of what to expect when v10.3 is finally released into the wild. Regarding the VNAV feature as far as I can determine from playing with the simulator; it is advisory only and displayed on the SVS page of the IFD550 as lateral and vertical offsets exactly as an ILS presentation, so I do not think it can be used with the other IFD models.

For my typical mission I think this implementation of VNAV is of very limited use. Most turbines and I guess jets tend to follow a continuous descent profile to the FAF to save fuel and simplify workload so the only real altitude constraint that needs to be observed and planned for is the FAF altitude. In practice the vast majority of both arrival and approach step down fixes in Asia at least are “at or above” altitude constrains which can largely be ignored since planning a CDP to the FAF generally keeps you well above those in any case.
I would have much rather seen an implementation of the Garmin GNS VNAV function that gave you an ETE and Descent rate (based on altitude/ rate of descent) to a known (FAF) waypoint on the flight plan. It is quick and dirty but works and all you need most of the time. On the IFD FMS, having all arrival/approach waypoints with altitude constraints removes the ability to get to the FAF ETE/VDR until it is the next WP to be sequenced, or you manually delete all the preceding altitude constraints.
From my perspective that is a step backwards.

The other major addition in v10.3 is the ability to select visual approaches to an airport (published ICAO airports only) Each published runway presents with the option of a visual approach complete with base, downwind or straight in joining options.

Cheers – E

Last Edited by eal at 29 Sep 07:19
eal
Lovin' it
VTCY VTCC VTBD

In v10.3 you can load the actual published visual circuit (noise, shape, height, arrivals, departures) and have your FD/AP flying it? or just some ideal rectangle 4nm*1000ft agl?

SkyDemon loads the actual visual circuit and produce joins to downwind, base, final but the HSI guidance is on your tablet rather than in the aircraft panel

I do recall that IFR VPT manoeuvres (in France, visual pattern with prescribed tracks either on radio nav or on visual nav unlike IFR circle to land) are not in Garmin but some heavy metal FMS have them in their database, I am not sure if something similar is doable for published visual VFR circuits, especially to reduce noise complaints and helps to avoid looking at tablet for the visual approach when low in busy circuit

PS: of course this would be an advisory guidance not to be used in IMC to fly a VFR circuit as one is supposed to use their eyes but it will come handy for VFR circuit flying in VMC

Last Edited by Ibra at 29 Sep 07:34
Paris/Essex, United Kingdom

Does it add a virtual glide slope to the visual approach ?

EBST, Belgium

Ibra wrote:

In v10.3 you can load the actual published visual circuit (noise, shape, height, arrivals, departures) and have your FD/AP flying it? or just some ideal rectangle 4nm*1000ft agl?

In the updated FMS set up you can define the Final length – Nm, Pattern width – Nm, and glideslope – degrees as a generic visual approach setting applicable to all visual approaches.

airways wrote:

Does it add a virtual glide slope to the visual approach ?

Yes, based on the above settings, it looks like it presents an advisory virtual GS displayed on the SVS page of the IFD550. So similar to the VNAV functionality it looks like the GS aspect and lateral offset would be available on this IFD model only. I am by no means certain of this as there is no documentation yet, so I am simply speculating based on what I can see and assuming the way it operates.

Cheers – E

Last Edited by eal at 29 Sep 08:12
eal
Lovin' it
VTCY VTCC VTBD

Out of interest how does the GTN implement VNAV and Visual Approaches?

I am obviously missing a trick here, but I am struggling to see the practical value of managing visual approaches via a GPS navigator. Other than providing location and runway orientation isn’t the point once you approach the runway for a visual approach to be flying outside the window, or is this an attempt to automate this aspect of flying by coupling it to an autopilot?

Cheers – E

eal
Lovin' it
VTCY VTCC VTBD

eal wrote:

Yes, based on the above settings, it looks like it presents an advisory virtual GS displayed on the SVS page of the IFD550. So similar to the VNAV functionality it looks like the GS aspect and lateral offset would be available on this IFD model only. I am by no means certain of this as there is no documentation yet, so I am simply speculating based on what I can see and assuming the way it operates.

Doesn’t the GTN display the advisory lateral and vertical guidance on the HSI? It would be disappointing if Avidyne only did a half-assed attempt at it. Being based at an airfield without an IAP, this was the feature that was leaning me towards the GTN over the IFD.

EIMH, Ireland

Hard to tell based on the simulator app only. Not much info on the Avidyne forum neither…

EBST, Belgium
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