Altitude constraint
Hi.
Why when I use VNAV descent it doesn't respect constraint altitude?
I must to use VS to descent more quickly when I arrive at my altitude constraint.
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Hi.
Why when I use VNAV descent it doesn't respect constraint altitude?
I must to use VS to descent more quickly when I arrive at my altitude constraint.
Comments
Hello, please say specifically which airport, which SID / STAR and a picture of the corresponding F / PLN page
Hi,
It took me quite a while to figure out what was the problem as you were not giving enough information.
I understand you are going to KLIT where there are no STARs and ALMOW is the IAF for Rwy 18.
VS 1600 Ft/mn is not a problem at all as your GS looks around 270 Kt. But your GS could change quite a bit in the next 700 Nm.
Anyway, what you should do is to be stable (landing flaps and gear down) before reaching ALMOW and to do so decelerate to be level quite few Nm before ALMOW (say 7 Nm).
Then you sould have enough time to decelerate and reprogram your VNAV approach to KLIT.
JP
I figured out i must to divide G/S by 2 to get my V/S to descent.
flight plan:EGLL to LFPG
sid:MAXI1F
star:BIBA9E
as you can see i must to be LORNI for 7000 feet .
VNAV profile ok.
Im at 15300 feet and im almost to arrive.
But you should have had 10,000 ft in KOLIV, 8,000 ft in NOPAR. You have already missed these restrictions with currently 15,000 ft. How did you program the VNAV?
Hi,
The first thing is to have your STAR right.
Coming from EGLL you arrive BIBAX 9E which is correct but after you should select the correct transition: MOPAR 6E, not LORNI which is to be used only when you arrive from the North East or the East.
Usually you should be by FL100 at KOLIV when East configuration and FL110 when West config. You'll probably land on Rwy 09L.
You should have selected, when programming VNAV, to be 10000 by KOLIV, then MOPAR.
When you land CDG (real world) you are vectored by ATC so to have it as near as the real thing the best way would be to follow the LOST COMS procedure as described on the chart.
JP
My VNAV set up is for the waypoint FF27L 5000 feet.
1500 V/S.
Are you executing the proper procedure to have VNAV capture the constraints correctly? This is what those who are trying to help are asking.
While we are all here to help, there has to be some input on the user to acquire some of the valid information required.
I can recommend you to a good source written by MudSpike (no affiliation with Majestic Software) which has been very helpful to many. You want to have look at Chater 10 - Approach and Landing.
https://www.mudspike.com/wp-content/uploads/2019/01/P3D-Majestic-Q400-Guide.pdf
Cheers
Hi
From EGLL to LFPG the arrival is always through BIBAX. So far, so good.
The landing Rwy should be 27R
BIBAX 9E that you are using is only for East landings. You should use BIBAX 9W. It is in theory used only by Jet planes but suitable for the Q400 due to her performances.
Then the transition is MOPAR 6W. You should not go to LORNI. Plan to be at MOPAR at FL110.
The Jeppesen charts: 20-2L / 21-OA08 / 21-8.
As mentioned in my previous post as we do not have radar vectors with the sim, follow the LOST COM.
If you follow exactly the procedure it should go fine.
JP
normally me I would use FF27R 5000 feet.
Your first constraint is KOLIV FL130, then MOPAR FL110.
You set up your VNAV 11000 and your ALT (no need for ALT SEL) 11000.
You'll need to be level by GIZOQ 5000' so you set VNAV 5000 and your ALT 5000 and also ALT SEL to make sure you level at 5000'.
You do not use FF27R which is your TOD for the ILS 27R.
When you turn right on track 238° you switch from PINK to BLUE, HDG SEL 238° and arm APPR to intercept LOC and GLIDE.
Plane not suppose respect all altitude constraint ?
Constraints:
KOLIV FL130
MOPAR FL110
GIZOQ 5000'
After GIZOQ you are on the ILS Loc and you are going to intercept the glide at FF27R so to make it simple, after GIZOQ forget about LNAV/VNAV and follow the ILS (BLUE instead of PINK).
Real life could be a bit different as you would be cleared direct KOLIV or MOPAR FL110 and radar vectors with altitude and speed given by ATC until you intercept the ILS. So with radar you do not work LNAV/VNAV but HDG, ALT with ALT SEL.
If you set your VNAV MOPAR 11000 it would respect KOLIV 13000 and would level 11000 at MOPAR.
Then you set GIZOQ 5000 and it would level 5000 by GIZOQ.
To make sure to be perfectly stabilized in altitude and speed at GIZOQ, you can enter few Nm before the WP as I explained in my previous post regarding KLIT.
On the charts and in the FMS the altitudes are clearly marked.
Forget about FF27R. This WP is after GIZOQ and you have to be at 5000 at GIZOQ.
Sorry But why I can't set FF27R and if I set FF27R why plane don't respect all altitude constraint before ?
Due to the different time zones, the discussions always take place when you can't yourself ;-)
Assume that ATC will bring you down on time and in compliance with the restrictions that they are also aware of. I myself always enter the first height restriction for calculating the TOD, as this must be observed first and then I am "Ready for Descend" a good 50 NM beforehand, in order to be able to descend flexibly. The descent using VNAV then takes into account all other restrictions, you just have to pre-select the altitude accordingly in the MCP. So theoretically you can sink down to the final approach, only VNAV will briefly disconnect before the FAF (depends on certain circumstances) in order to get a defined, new confirmation of the VNAV mode for sinking in the final.
You don't have to / can't always go down with VNAV, as ATC often messes up our profile. So it will be necessary to switch to VS somewhere, because we have to stay at a certain height for too long or have been assigned an intermediate height that is not known in the VNAV profile. In many cases, vectors in the vicinity of the airport mean that you have to change the modes of the autopilot system.
Because FF27R is not a constraint. It is the start of the glide for the ILS.
You should do it the way described if you want to do it as near as the real thing otherwise I do not think it would work and you are going to be disappointed by the results especially if you intercept a false glideslope.
ILS are flown that way: LOC intercepted, on centerline, altitude stable in level (5000' ILS 27R CDG) before to intercept the glide with the flaps and gear and that has been done that way long ago before the FMS existed.
Sorry, I did not see FraPre comments when I posted.
No, you program (or I'll do it that way) VNAV based on the first restriction in the flight path. VNAV remains active and only levels where the height set on the MCP is reached. If you pretend (offline) that you always get the next altitude cleared in time, you turn in the next altitude in a timely manner and the aircraft continues to sink using VNAV, also taking into account the next altitude. Only before the FAF (Final Approach Fix), i.e. at the beginning of the Final Approach, VNAV is automatically deactivated, since the autopilot system really wants to ensure that you go to the final with VNAV. Here you simply activate VNAV on the MCP again. I have to see if I can get a series of photos banned into a PDF without exceeding the data size.
Look this video.
First constraint with alt select
Not very nice, but you can see that it works. The flight went from EVRA to EYVI. The problem with the 5000 ft came from adjusting the regional air pressure.
Plane will descent even if I put 11000 so why you put 11000 instead of 5000 and alt select and will respect all altitude constraint.
Thank you for the pictures.
When you set vnav for 11000 you don't set anymore for the next altitude constraint ?
Only set next lower altitude and vnav will continue to descent ?
So I want to make it a bit realistic, even when I'm flying offline. If you are released by ATC at a height, you set this as ALT SEL on the MCP, because I am not allowed to sink any lower. I could set the 5000 or 3000 without ATC, then the descent would go to this height, but still take into account all restrictions. You can play a lot there if you understand the AP modes. When is the best time to use which AP modes are part of an airline's line training. I often only fly the first part of the descent with VNAV and then switch to V / S, but then switch back to VNAV for the final approach if necessary.
To Hélico 55,
There is a way to have it LNAV/RNAV all the way down to GIZOQ is to fly the MOPAR 8Z transition (Jeppesen chart 21-0B4). This procedure is used only at night but who cares with the sim.
flight plan LFRS to LFMN
Sid:LUGE3V
star:NISA6R
runway:4R
sorry for the picture but can you help me for wapoint between MUS and CI04R ?
MUS have not constraint,must i add constraint for MUS ?
Hi,
Without ATC you are right in choosing the LOST COM procedure.
After MUS you do not follow LNAV/VNAV anymore. You are with the BLUE NEEDLES.
If you were with ATC they were not going to ask you to be at FL120 at TIPIK and MUS at 5000' as they know the performances of each aircraft and loosing 7000' in about 2'30" is possible but a bit much for the Q400.
MUS 5000' is not such a constraint, it is a safety altitude, same between MUS and IF 4000'.
The best way for you would be to select 5000' for MUS with ALT SEL and after MUS 4000 with ALT SEL, VS around 1/2 the GS for the 3°.
So, being 5000' at MUS, HDG 088° ALT SEL 4000' APPR to intercept the LOC, the glideslope is going to be active at 12.5 Nm and the ILS is going to bring you down to the Rwy. Be careful as the LOC is OFFSET 2°. If you choose Rwy 04L, then you are on the Rwy axis.
The point D17 is not for you, it is when coming from NERAS.
JP
I never use ATC.
If I use atc I can't use vnav because I must to wait atc
say me when to descent ?
So must to use V/S to descent and I must to calcul
V/S feet I must to use.
In that case I would go down with V / S. On the one hand, ATC expects a certain rate of descent (I mean there are sometimes different values of 500/1000 ft / min.), On the other hand, the instruction to sink is not always associated with a certain waypoint, but you fly on your planned routing and get that Instruction to drop to FL xyz, what should I program with VNAV? The programming of VNAV based on the first waypoint with a restriction generates a TOD, by which one can orientate oneself and prepare, nothing more. Knowing AP modes and using them sensibly is not just VNAV. ATC also knows what the individual aircraft types can do and what can be expected of them.
Why on the picture Satot 11000 and next constraint Pigna 5000 and after Nopos 9000 ?
It's star Lafleur 6 for Cyul 10-2E navigraph chart.
Well, it starts with SATOK with in or below 11000, with PIGNA in or above 5000 and DEGVI in or below 9000. This doesn't really contradict each other, since the two larger values represent maximum values, the 5000 a minimum value. This navigation point is in the terminal area of CYMX, where the corresponding procedures and heights are taken into account.
For Cyul runway 24 R
Must I set vnav with Lonna 3000 feet ?
The total Jeppesen document is 1435 pages.
Here is the explanation for SID/STARs.
JP
It really is a difficult subject, it seems to me. From the cruise, you program VNAV with the first waypoint in the direction of flight with an altitude restriction. This will be somewhere on the STAR or the transition. From this, the FMS now calculates the TOD, for you an orientation where the descent, if you fly according to the charts, begins. If you are flying online, it is a clue from where ATC may instruct you to descend (so you should have completed your descend preparations).
For the first sinking it is necessary to set the ALT in the MCP to a lower value and to arm the VNAV. We've also had the topic of heights before. The real altitude is entered as SEL, which ATC instructs us. With further instructions, this is reduced again and again and secured with SEL, otherwise there is a risk that at some point you will continue to sink without ATC approval, because the VNAV profile specifies it. If you then sink once in VNAV mode, VNAV complies with all restrictions, i.e. sinks to an altitude, holds it if there is no further descent at first and then continues to sink at some point if the VNAV profile specifies this.
Due to vectors or technical circumstances (waypoints without specified restrictions) it may be necessary, or simply better, to switch to VS and cancel VNAV. Then simply activate VS. sink to the desired or instructed height and adjust the sink rate if necessary.
If you are cruising at FL 240 and, according to the ATC, are supposed to sink to 11000 ft, it will happen with VNAV that if there is a waypoint with a restriction of 15000 ft in between, VNAV levels the descent to 15000 ft and first to the instructed ones 11000 ft will continue to sink when the VNAV profile specifies this again. But that's not what ATC intended, they want you to sink directly to 11000 ft. So here you have to go down with VS to do ATC justice. At some point, in your case, ATC will release you or yourself to 3000 ft and send you on an intercept heading to the final approach. The approach in your case is an ILS approach.
I think VNAV is not so superficially the mode that is used in normal descent, but VS. If you fly alone and strictly according to the charts, you can use VNAV taking into account the technical characteristics.