All Of A Sudden IAS,Alt Loss
Set out on a flight, route and fuel loading created by SimBrief, from FSDT's KJFK v2(New York) headed for KUNV,(State College) a mere 168 miles away. Reached CL at 22000ft all running perfectly normal, when all of a sudden, at exactly same point, waypoint ETX(East Texas) as happened last night, the aircraft from Cruise Power speed and at 22000ft started losing IAS and ALT, and became awkward to even fly by hand as it started to veer left, right and go bananas. Had to abort the sim.
Any clues as to why this would happen, and yet I have used it in Europe, e.g. LOWI-EGCC with no problems at all?
Comments
Hello, a first request, have you been traveling with a weather program and have you activated the same weather both times?
If there were suddenly strong gusts of wind, the autopilot remained active, if so, with which modes?
Cheers
Thanks for that reply.
But it was only a daylight flight, no weather engine employed, just the default P3Dv4.5 weather, and I just tried the very same route in a PMDG 737,same ALT, and not a glitch. Perfect flight. But Ill re-try and this time switch on the AI
I would try the route again and see if the issue can be repeated..
Thanks again. No defined weather, just the sim's fair weather. Am re-flying the same route again with AI switched on this time, same fair weather engaged. So, let's see if the same yo-yoing happens again. Will report back.
Update as promised. It seems leaving the anti-ice switches was what caused that erratic behaviour, because as soon as I switched it on in prepping the aircraft, the very same route, except dusk this time, as compared to this morning's clear daylight, I had a problem-free flight. Now, I have no idea as it was New York to State College whether I was over the Appalachian Range that may have caused ice detection, I have not a clue, as I was using nil weather engine, and default sim fair weather.
Anyways, now I know what led to that odd behaviour yesterday and this morning.
Trying the previous scenario to see if you can replicate the issue would be interesting.
Thanks again for your reply. Will give it a try as soon as daytime free time allows, and report back
Thanks again for your reply. Will give it a try as soon as daytime free time allows, and report back
Okay, can now confirm, same routing, same altitude, did not switch the AI on, at same place along the route, after reaching 22000 ft with no problems at all, until this showed up and it reverted to what I first reported.
Default sim fair weather was loaded
Would have been nice to see the ED or overhead and glare shield / pedestal. When I see these messages, I wonder if the engines are still running? The messages "Tank Fuel Low" and "ENG Fuel Press" suggest that you run out of fuel or that it does not come to the engines. Very strange.
There has to more to this puzzle that you are not aware of or not enlightening us about.
Thanks for the 2 replies.
When climbing this morning
MCDU Payload
The route map
This is round about where things started going haywire
And there you have all the information I hope you wanted
You also have to refuel, if I see the right one you have around 270 kg on board
The fuel page that you show in the FMS is what you were planning to put on the aircraft, correct? However looking at your fuel gauges you are practically flying on fumes as you only have 265 kg of fuel. So I am suspecting that if you are loading the aircraft via the cpan your fuel loads are not planned correctly.
There are 2 boxes for fuel in the cpan... The top one is for preffered fuel and the bottom one is your intended fuel burn for the trip.
Funny, you mentioned that because that was a screenshot I took while climbing out of New York this morning. And I did tell GSX to load 7000lbs of fuel, which I thought for a short hop was adequate enough. Either GSX screwed up, or I did not check the cpan.
Now I that am aware, thanks to you two, what caused that weird AP repeatedly switching off and the IAS bleeding speed, I will make another attempt, no AI switches on, again, and this time monitor the fuel without GSX
Thanks for that. While I am at it, where can I get a real good YouTube or text Tutorial on the programming of the VNAV?
In the forum here you can actually find everything, which is not that difficult. You inform yourself in the cruise about the first height restriction, which can be found on the STAR or at the latest at the IAF / IF. This determines the start of the descent on the T / D. On the VNAV site you look for this point, because all restrictions are noted here at the waypoints. You then select the sink rate (usually 1800 ft) and confirm this. The T / D is now shown to you. The VNAV Deviation Bars appear 2 minutes before reaching the T / D, you will receive the corresponding information on the PFD. You can now turn in the first target height on the MCP and arm VNAV. The descent then starts automatically at the T / D. This is also clearly described in the manual.
An example
Find the first height restriction on STAR or IF in the charts and / or on the LEGS Page. In this example it is OBANO it FL11000 or above.
Call up the VNAV page on the CDU and look for the suitable waypoint that you need for VNAV programming, i.e. OBANO, the 3rd
Enter 3 in the highlighted field and press ENTER
OBANO now appears with its restriction and the next field is highlighted, but we can generally not need to be skipped with ENTER.
The specified height restriction is now highlighted and can be confirmed with ENTER. If you would like to use a waypoint without a specified restriction, then enter the desired value here and confirm with ENTER.
Now the sink rate is Now the sink rate is highlighted, the default is -1800, but can be changed, confirm again with ENTER., the default is -1800, but can be changed, confirm again with ENTER.
The system now has all the necessary information and calculates the T / D with distance and arrival time
The deviation bars appear 2 minutes before the T / D is reached
We now turn the desired target height, so here FL11000 + ALT SEL and armed VNAV in the MCP
As we get closer to the T / D and nearing the VNAV PATH, the deviation shelf begins to move
When the VNAV Path is captured, the AP modes change from ALT Sel to VNAV PATH.
In the course of the descent, we then have to set the height in the MCP to the new target heights and do not forget to press ALT SEL in order not to accidentally sink too low.
Done all that but it never comes up in the PFD as flashing VNAV for me to trigger the VNAV button. Nevertheless, thanks, will try and follow your instructions.
@FraPre Tried the above as you suggested, even saved those screenshotsof yours of of the MCDU to refer to for a flight from KMCI to KIAD, and did exactly as per your instructions above, put the first descent ALT, but that deviation bar did not show any V at the top. See attached.
Where am I going wrong, please?
If you have adopted the 1800 with ENTER on the VNAV page, only then will it be calculated where the TOD is and this is also displayed on the VNAV page. The TOD should be a bit ahead of MGW, since you have to mine 17000 ft.
VNAV programming must of course also be done in good time. If the time at cruising altitude is only short, you should program this immediately after reaching the cruising altitude, not that you have already passed the TOD long ago.
However, some things on your PFD also do not fit (Speed, 15000 ALT blue), but only by the way.