AW139 VNAV
 

This is a question for those who flies AW139.

In some documentation we see that VNAV is advisory only and provides no automatic vertical control, and in other doc we see that VNAV can be coupled to the the autopilot for VGP approach and MOT mode.
Can someone tell me more about VNAV?

Thanks.

Eric

VNAV can be integrated with lateral flight plan for the entire flight. But, all the needed values (altitude, speed, vs etc.) should be entered to the FMS for each leg during the performance initialization phase. It is not possible to couple the FMS to the FD. You should fly it manually or using the ALTA mode of AP. What you have on the PFD is vertical deviation scale with a VDI bug (cyan) on the right side.

VGP should be considered together with LNAV-APP mode for RNAV-GPS approaches if the procedure is present in the FMS database. For this time, it is possible to couple the FMS to the FD. You have the same VDI bug on the right side of scale, and also the colour changes, now it is magenta (means coupled), and the path is automatically followed like GS of ILS approach.

I remember VNAV and MOT buttons on the AP director of SAR models, but i've got no idea how to use it.

aw139
 

Thanks a lot.

Mmmm ...

Also you will NOT be able to descend below the altitude selected on your PFD (ALT select) step down for each stage of your descent ... so that will take some co-ordination to ensure safety and vertical separation criteria is ensured ......

The VNAV button on the SAR FD is not yet functional.

Perhaps in Phase 7.....?

Meanwhile,enroute altitude must be controlled the "old fashioned way" - ALTA or ALT or VS... or the real old fashioned way.

VGP can be coupled for altitude control for published approaches with a vertical decent profile.

When pressing the VNAV button on the AFCS panel in AW139, AW169, and AW189 helicopters, it shows "VNAV is not installed" or "function unavailable."
Why is VNAV not engaged on these helicopters?

If NAV SOURCE is set to FMS, pressing the APP button activates a VGP approach. If NAV SOURCE is set to ILS, pressing the APP button activates an ILS approach.
When and how does the AFCS use the VPATH mode of VNAV submode?
https://cimg1.ibsrv.net/gimg/pprune....11a717bfc5.png

Always great to see operators with no OEM support seeking advice from social media. It really helps to boost the image of how we operate in the RW world.

The letters in the vertical path indicator on the 139 are important.

V = Vpath. Defined by the ToD position for a leg where the pilot has entered altitude information for 2 or more FMS consecutive waypoints and ToD is calculated by the descent angle defined in performance initialisation. V may also appear when a direct to altitude is selected on a single leg rather than direct to waypoint. VPath is advisory only, the AP cannot be coupled to this information. VNAV has no AP function as of phase 8.

P = VGP. Defined by the baro altitudes on a published and activated approach, either VOR overlay, NDB overlay where waypoint altitude is defined for the final segment or where a GPS approach has no LPV or the pilot has deliberately selected LNAV/VNAV minimums. Coupled to the FD by use of the APP/DCL button. P may also be seen when established prior to the FAF on an LPV approach and may capture for a period before the transition to LPV.

L = LPV. As per above but for LPV approaches only. Defined by GPS altitude. G = GBAS very similar but an option so not fitted by default.

I = ILS Glide slope. Self explanatory. Not an FMS mode therefore no FMS altitude is used. The nav source must be LOC to allow it to couple however it can transition from LNAV to LOC through use of PRV.

F = SAR MOT vertical guidance. Automatically calculated and coupled.

Just realised I'm answering a 13 year old question..... thanks for the zombie thread resurrect! 🤨

First Q, because, as indicated by the aircraft, it's not installed. It has never been installed but it may yet be in the future, so the button is present.

Second Q. It doesn't except to generate annoying messages on the 139 about resetting the ALT select. The AFCS doesn't do anything useful with VNAV info, because, well, see answer 1....

I'm not sure if there are any helicopters certified with VNAV. Seems like an opulent expensive install. If there are, please educate me.

VNAV certification issue
 

The reason for VNAV is not active can be related with certification issue.
“It should be noted that there is no vertical requirement in this AMC associated to the use of VNAV guidance outside of the final approach segment. Vertical navigation on the initial or intermediate segment can be conducted without VNAV guidance.”


https://cimg2.ibsrv.net/gimg/pprune....c84a3ccf76.png

13 years between post #5 and #6....:-)

Focus VNAV
 

Everyone should focus the why VNAV mode is not couple with AFCS in case of VNAV button is present on AFCS Control Panel.

time between posts are not your business.

Does Airbus' "Rig'N Fly" count (as VNAV, not opulent expensive install)? It can't be used for en-route vertical guidance, but it will fly the step-down changes and deceleration automatically and then up and into the hold all based on the numbers the user plugs into the FMS. The functionality compared to VNAV is the same, but its compressed only into the last few NM of the flight rather than the whole thing.

VNAV function works quite nicely in the S76D thank you very much.

could you give us detailed information about s76d vnav?

Depends how you are defining it. Many helicopters can fly coupled LNAV/VNAV approaches, even if they can't fly coupled VNAV enroute. Many more can display VNAV information, both on the FMS and PFD, but have no (VNAV) coupling function for any phase of flight.

Was referring to a full VNAV system comparable to FW aircraft, with ability to fly STAR's and complicated DP's with speed and altitude constraints. Not much use for most helicopters. Never flew the Thales D 76.

Why AW139/169/189 is not using VNAV at cruise phase?