Pressure problems with Radar Contact

[kryten 1]

I have been having problems with assigned altitudes when using Radar Contact as ATC and the QNH is low, such as 989 HPa, For instance, after passing the TA and pressure is set to STD  if I am cleared by ATC to FL410 i climb to that altitude and level off. The RC ATC then tells me repeatedly that I am not at the assigned altitude even though 41000 shows on the PDF altimeter tape. It would be very helpful if anyone using Radar Contact was to try to replicate this in the PMDG 747 and report back the results. Just set the weather to a low QNH (I use one of the weather themes, stormy weather I think) and see how RC ATC responds.  The problem does not occur at a normal QNH.

[pschlute 37]

From your other thread on the same issue, it appears your problem is that pressing STD does not change the QNH at all !

 

Are you changing both pilot and co-pilot to standard ?

[kryten 1]

No, I'm just pressing the pilot knob to STD. I hope to be flying tomorrow afternoon and will change both pilot and copilot to STD to see what effect that has. 

[kryten 1]

I have flown today using both pilot and copilot low QNH settings and setting both to STD when passing TA but I still had the assigned altitude problem with RC.

[pschlute 37]

I have flown today using both pilot and copilot low QNH settings and setting both to STD when passing TA but I still had the assigned altitude problem with RC.

 

I think you need to sort out your STD setting in the aircraft. Then RC will fall into line.

[scandinavian13 5,192]

I have been having problems with assigned altitudes when using Radar Contact as ATC and the QNH is low, such as 989 HPa, For instance, after passing the TA and pressure is set to STD  if I am cleared by ATC to FL410 i climb to that altitude and level off. The RC ATC then tells me repeatedly that I am not at the assigned altitude even though 41000 shows on the PDF altimeter tape. It would be very helpful if anyone using Radar Contact was to try to replicate this in the PMDG 747 and report back the results. Just set the weather to a low QNH (I use one of the weather themes, stormy weather I think) and see how RC ATC responds.  The problem does not occur at a normal QNH.

 

Wait...

 

Isn't this the same exact issue you started another thread about, in this exact same forum?

http://forum.avsim.net/topic/449973-qnh-to-std-pressure/

 

...on top of a few other threads elsewhere (the original thread you posted here has allusions to those)?

 

 

 

If you want an issue to be fixed, it's best to keep it to one thread in each forum.  When you make multiple posts in a single forum, people start replying to both without knowledge of the other, and the ideas that get shared either get repeated, or lost.  People don't get the opportunity to build off of each other's thoughts.

 

Please - have patience, and keep it to a single thread.

[kryten 1]

 

 

I think you need to sort out your STD setting in the aircraft. Then RC will fall into line.

 

Will you please elaborate on this. With a low QHN of 989 I am setting this pressure on both pilot and copilot EFIS. When passing TA I set both to STD. When attaining and leveling of at the assigned altitude RC ATC I am told I am NOT at the assigned altitude.

 

 

 

If you want an issue to be fixed, it's best to keep it to one thread in each forum.  When you make multiple posts in a single forum, people start replying to both without knowledge of the other, and the ideas that get shared either get repeated, or lost.  People don't get the opportunity to build off of each other's thoughts.
 
Please - have patience, and keep it to a single thread.

 

The reason for the new post was to attract the attention of those people using Radar Contact and had not been sufficiently interested by the title of the first post to read it. My aim, as I said in the first post of this thread, was to ask those using RC to replicate the situation I was having the problem with,

[pschlute 37]

 

 

Will you please elaborate on this

 

You said this in your other thread:

 

"I am starting to think that pressing the STD button does not change the QNH (for example 989) to STD (1013). This would account for the ATC problem. Another thing that makes me think that this is the problem is that when I change from a QNH of 989 to STD I would expect the altimeter tape to "jump" to a new altitude on the PFD altitude tape because of the sudden change to a significantly different pressure setting. There is no "jump".

 

You should indeed see the altitude tape "jump" if you change from an extreme low/high QNH to STD. If this is not happening, then this is a fault with your setup/install of the PMDG747, and is the reason why you are being told by RC that you are at the wrong altitude. You need to correct the fault with the 747. If instead of pressing STD, what happens if you dial in 1013 ? Does the altitude tape move ?

 

I would suggest a search on this forum to see if others have had this problem. Perhaps consider a re-install ?

[kryten 1]

Yes, I think the best thing to do is reinstall the 747.

[kryten 1]

 

 

I would suggest a search on this forum to see if others have had this problem. Perhaps consider a re-install ?

 

I uninstalled the 747 program and re installed it but the problem is still there. I cannot find anyone else on this forum with a similar problem which is why I started the thread. I hoped that someone else would be able to repeat my situation and report results but it has failed totally because nobody has posted a reply having tried to replicate the problem using PMDG 747, Radar Contact and a low QNH.. 

[agutz 13]

It doesn't make much sense to start different topics in more than one forum.

And yes, I have replicated the probem and posted in the RC forum.

It looks like the OP (signature missing) is better at starting topics than at reading what is coming in.

 

Let me collect what is known by now:

 

It is not an installation issue.

It is not a RC issue.

It is a rather obscure issue with the altimeter of the 747X.

 

Like the OP did I made a flight with the initial QNH set to 898. I was not using RC. The QNH is monitored by FSUIPC reading the appropriate offset and displaying it on screen. At TA I pressed STD, on the MFD "STD" was displayed in green, but the altimeter did not react (FSUIPC readout is still the same) indicating that the plane still flies at QNH 898. I had to turn the knob to 1013 to make the altimeter tape jump.

 

If you don't have FSUIPC logging on or if are not using a "rubbish" ATC program like RC, you will never know the altimeter didn't change.

 

I am a bit puzzled by this. I have been flying the 747X many times and never experienced this before. But then I probably never started with such a low QNH.

[Ray Proudfoot 8,946]

I would appreciate someone from PMDG responding here to this problem as kryten is telling me on the RC Forum that PMDG is blaming RC.

 

As Andreas has kindly confirmed the STD button doesn't set standard pressure of 1013 / 29.92 without RC running how can this program be responsible? :rolleyes:

[agutz 13]

There is a another way to demonstrate this pecularity (PMDG 747-400X only, and only when departing at rather low QNH) by using AivlaSoft's Electronic Flight Bag (EFB):

At TA with QNH 898 both, the plane's altimeter and EFB, show 18000. For this demonstration I leave the plane in level flight. After pressing STD the altimeter tape moves to a new position of 18000 and EFB now shows the plane to be at FL 173, indicating that the altimeter is still on 898 and I am 700ft below the altitude I'm supposed to be with STD setting (1013).

Manually adjusting the altimeter to 1013 the altimeter tape on the MFD moves again to a new position of 18000 and EFB reads FL 180.

QED

I am not going to test at what higher QNH the altimeter's functions return to normal.

[Ray Proudfoot 8,946]

1 hPa = 25.879ft. Let's round that up to 26ft.

 

Radar Contact's default altitude deviation setting is 300ft. So 300/26 = 11.54hPa.

 

Therefore if the QNH was within 11.5hPa of standard pressure of 1013.2hPa whilst you were maintaining Flight Levels that would keep Radar Contact happy. That would be a QNH in the range 1001.7 to 1024.7.

 

That's why this problem is not apparent on every flight if real-world weather is used and assuming that Radar Contact users do not change that default altitude deviation.

[Elsmoko 5]

I just noticed this issue while flying the PMDG 744.  My altitude shows as FL340 on PFD (STD appears on the bottom of PFD);  and pressing

Shf + z  shows that I'm at FL325 and of course RCV ATC is giving "advisories".    Pressure at the departure airport (SAEZ) was Q1026.

Could flying near the poles cause this?  I'm flying a Great Circle route (SAEZ-YSSY) which has taken me near to Antarctica (south of Lat S68....).

I don't ever remember having this issue in the past with the 744 or any other AC.

Best to all,

Ken Boardman