Hi,When using the NGX with either default FSX online weather or an external program such as AS2012 or such, I'm finding that all weather depiction in FSX has trouble interpolating temperatures aloft; at least on my setup. For example, in between the normal published reporting levels, the temperatures aloft in FSX tend to stay at the temperature of the current or lower reporting level for too long before transitioning to the temperature at the next reporting level. There isn't simply isn't enough interpolation between the weather reporting levels for a realistic, smooth temperature change as the aircraft is climbed into the higher flight levels. As a result, with the high fidelity flight and engine performance dynamics inherent in an aircraft like the PMDG NGX, the 737NGX tends to climb at a sporadic rate, rather than a realistic, predictable climb to higher altitudes. Climb rate when flying a constant IAS or MACH should of course diminish as the aircraft gains altitude, but with the NGX on my installation I experience normal climb rates that will suddenly diminish and taper off from around 2000 feet a minute at around FL240 (at standard weights) to something like 200 feet a minute. Sometimes the NGX will even level off for a few seconds during the climb as it struggles to maintain constant airspeed. It's very easy to predict when this anomaly will happen because I can monitor the true outside air temp on the FMC Progress page 2. The NGX struggles when the temperature aloft is not changing fast enough from the previous reporting level to the temperature at the next highest reporting level. When the temperature finally does begin to match that of the next higher reporting level, the NGX's climb rate shoots back up to around 2000 fpm again. I essentially experience periods of temperature induced 'climb porpoising' in any given situation and I'm not able so far to find a way around it. Again, I experience this with default FSX online weather and either AS2012 or ASE. I have a registered version of FSUIPC installed, but I've also been able to reproduce the climb behavior with FSUIPC completely uninstalled. One might suspect some kind of situation with SIMCONNECT, but since I experience the climb problem even with default FSX online weather this would seem to rule that out as well. Do any of you guys NOT experience this kind of climb behavior with the NGX and online real weather of any kind? I'm just wondering if this is a situation one has to live with given the limitations on how FSX is currrently able to depict weather or if there is something that perhaps can be fixed on my side.Thank you for any help or insight!Signed,John C. Thomas

I don't have that problem with AS2012. If you're using FSInn, make sure its weather is completely disabled.

I don't have that problem with AS2012. If you're using FSInn, make sure its weather is completely disabled.

I don't have FSINN, but thanks.Signed,John C. Thomas

Try to enable wind smoothing in fsuipc. I experience the same symptoms when the wind abruptly changes in FSX.

Try to enable wind smoothing in fsuipc. I experience the same symptoms when the wind abruptly changes in FSX.

Hi, I have wind smoothing enabled in both FSUPIC and ASE, but thank you. Signed,John C. Thomas

You shouldn't be using fsuipc and ase. select "weather settings off" on fsuipc and see if that helps.

You shouldn't be using fsuipc and ase. select "weather settings off" on fsuipc and see if that helps.

Hi,I've experimented with FSUIPC completely uninstalled from FSX and yet I experience the same problem, but thank you.Signed,John C. Thomas

I am not sure this is a weather issue at all. So when you say something like "Climb rate when flying a constant IAS or MACH should of course diminish as the aircraft gains altitude", that is actually only relevent in low altitude props or turbo props from Cessna's to JS41 or Dash 8. Anything much larger and you should be using the VNAV equipment your employeer paid so much for. Turbo jets do not normally takeoff at max power, and their power levels do not diminish with altitude they same way combustion engines do. Also IAS and MACH measurements are not the absolutes that you seem to think they are.

Paul, well the rates should diminish somewhat, of course not like when you try to pull a full AT72 to FL250, but even an NG should not keep the same rate at 250 indicated on level 380 as it does on pressure altitude 038...

Paul, well the rates should diminish somewhat, of course not like when you try to pull a full AT72 to FL250, but even an NG should not keep the same rate at 250 indicated on level 380 as it does on pressure altitude 038...

Yes, thinner air = less climb performance at high altitudes.

I am not sure this is a weather issue at all. So when you say something like "Climb rate when flying a constant IAS or MACH should of course diminish as the aircraft gains altitude", that is actually only relevent in low altitude props or turbo props from Cessna's to JS41 or Dash 8. Anything much larger and you should be using the VNAV equipment your employeer paid so much for. Turbo jets do not normally takeoff at max power, and their power levels do not diminish with altitude they same way combustion engines do. Also IAS and MACH measurements are not the absolutes that you seem to think they are.

Hi Paul,I do always climb with VNAV engaged on the NGX. The normal VNAV climb profile for any given cost index will initially fly a constant IAS above 10,000 ft, then intercept the programmed cruise Mach number at whatever relevant altitude (depending on temps aloft), then maintain cruising Mach number until cruise altitude is reached. All things considered then, climb rate is always a resultant variable depending on weather conditions and aircraft weight; airspeed is however is a constant with normal climb profiles. Jet engines do of course safely produce more power and become much more efficient as the temperature aloft decreases, but the air is getting thinner and thinner as the aircraft is climbed to higher flight levels. The turbine engines are highly efficient at these high altitudes but the lifting bodies (wings, stabilizer) become increasingly less aerodynamically efficient. Thus, climb rate naturally diminishes in this situation. What I'm experiencing is way beyond the natural decay in climb rate using normal VNAV climb profiles. I'm seeing the aircraft level off completely sometimes during the climb, which should never happen at the aircraft weights I fly with. Signed,John C. Thomas

John, watch the PROG 2 page on the FMS, and tell us if the SAT suddenly changes or is positive at high altitudes.Watch the wind indicator on the ND, and tell us if that's suddenly changing.

As far as I know FSX weather gets SAT modelling right. It's a simple linear law, hard to get wrong. I haven't seen temperature change in a series of steps. Therefore it's unlikely that FSX temperature is creating the problems you notice. However FSX weather does change in discrete steps as the aircraft moves from one weather station area to another. This might be what is causing the changes (could be a few degrees temp change or a few HPa pressure). This would be enough to create porpoising in a climb as any step changes in conditions could trigger the natural phugoid oscillation. You would also notice changes in pressure altitude and power requirements in cruise too as FSX updates the weather.

I have noticed what you are talking about John, mostly when climbing out of a warmer climate (Hawaii) using AS2012. The temperature reduction really seems to lag in reducing as you climb, like the temp interpolations between the known altitude values get behind in the processing. I have experimented at a given altitude by closing AS2012 and then reloading it, and the temperature returns to a more normal value once AS2012 reloads. This might be something for us to take over to the AS2012 forum.I have noticed what you are talking about John, mostly when climbing out of a warmer climate (Hawaii) using AS2012. The temperature reduction really seems to lag in reducing as you climb, like the temp interpolations between the known altitude values get behind in the processing. I have experimented at a given altitude by closing AS2012 and then reloading it, and the temperature returns to a more normal value once AS2012 reloads. This might be something for us to take over to the AS2012 forum.

I appreciate everyone's replies and very good advice on this subject! I think I've exausted every possible solution to no avail. I'll next try reinstalling FSX altogether and just try starting from stratch to eliminate any kind of conflict with other addons I have.