AS 2012 – “problem” with OAT (& PMDG 737 NGX) + updates question

[Adam4171 0]

Hi,I have a couple of questions related to AS 2012 & PMDG 737 NGX.1) I plan a flight, for example, from EETN to LKPR (CRZ ALT F400). When I need to know what the CRZ TAS is going to be, I have to know the OAT in that level -- then I calculate speed mach 1 (in kts) according to that OAT and multiply it by the mach number which is going to be my CRZ (ECON from FMC); the speed that is economical for me in F400 is mach 0.782 … that's why I need accurate OAT -- BUT here I see the problem: For filling T/C OAT in FMC, I always find any airport that is located near by the T/C point (seen from NavDisplay), then I write this ARPT (ICAO) to the Active Sky (Wx Report) to see the TEMP at the required FL (under the symbols of weather, there are wind and temperature information for certain altitudes -- 3K, 6K, 9K, … 49K) -- so from that I can read that e.g. in 39K feet the OAT is –57.4 °C etc. According to that temps, I calculate the OAT for 40,000 ft (which is sometimes higher than in lower FLs -- possible?) -> I put that temp. to this http://www.csgnetwor...achonecalc.html and just calculate the mach 1 speed according to that temp, and then multply it by e.g. 0.782 -> I find out that my CRZ speed (that I also fill in the FPL) is going to be +- 447 KTAS. … well, as soon as I reached F400, I saw in FMC that the OAT was much lower, approximately –77 °C, so my airspeed then was a bit lower, e.g. just 425 KTAS and not 447 as I had been expecting… But if I check the weather at AS (locked to nearest ARPT), I can see there's just written something like 39K & –55.8, 44K & –57.4 --- so how is it possible that I have so much lower OAT than everywhere is issued? -- now I mean also this: http://jeppesen.com/...ion-weather.jsp -- also showing the TEMP if you open the wind forecast -- e.g. FL390 & showing –55 °C, but in FMC I can see OAT –77 °C…So, I'd like to know if the AS (and then aslo the JEPP. weather) shows the OAT correctly (-> then there must be any problem with FSX/PMDG), or if the OAT that shows FMC is correct. (But I suppose there shouldn't be any incorrect entry in the JEPP. weather maps.) :)And why do I need to know it?Well, just because I don't like when something is not working as it should / is not accurate, then also to fill the CORRECT CRZ airspeed to the FPL, and finally, when I calculate the EETs to FIRs, then it's not accurate (according to the planned TAS & actual TAS -- even if the wind is calm).P.S. I'm not using FSInn, but Squawkbox with Weather settings OFF.And the second, last, not so long question: :)2) Is it very important to have very quick internet connection to get the actual METARs on time (with minimum delay)? Because I have Wifi connection and sometimes it's delayed up to 20 min. -- it's 10:20 Z and I still have valid METAR from 09:30 Z (instead of 10:00 Z). And just one more note: In AS 2012 settings, I have set Automatic Downloads (+ VATSIM Online Weather) to every 5 min., but if I look on Wx Report, I can see “Last Updated: 00:15” and now it's 00:43 -> so “Last Updated” should now be showing +- 00:40 (update every 5 mins.); am I correct? (if yes, why is it not?)Thank you very much in advance!Adam

Edited February 6, 2012 by Adam4171

[Jet_Airliner 0]

1) When you flying, call outside temprature SAT. Secondly, to calculate the TAS use free tool Adacalc. What you need is to fill the plan in active sky and scroll down the table of waypoints till you see average wind and temperature. Use average temperature to calculate the isa deviation, or simply put this temperature in fmc and it wil give you the isa dev.Open adacalc -> speed calculations and enter your planned mach number, flight level, isa deviation and it will give you TAS. Use DWC in active sky for correct wind and temp on flight levels.2) I guess the weather won't change in sim, till your pc will be conected to internet while the active sky updating the weather. If the update cycle is failed, then it will try again at next update. When it will be successful - it will show correct times.

Edited February 6, 2012 by Jet_Airliner

[Adam4171 0]

OK, thanks for that reply!What a useful calculating tool! I hadn't known about this before and I'll be using that since now always for sure! :) Well, I am always filling the AS FPL to have the route on map; but I am asked for the cruise speed -- and how do I know it before I see the SAT? Or is it not so important here to be accurate? OK, I fill there e.g. 440 KTAS (just my supposition). Now, I have filled the AS FPL, with waypoints as required. When I look on the Flight Plan, I scroll down and see there a “table” with the waypoints and winds aloft by them. Next to the wind, there is the SAT in the brackets -- so do I manually have to calculate the average CRZ SAT? Because under that I only can find the average wind at F400, but not the average SAT. Then, as soon as I know the (T/C) SAT, I enter it into the FMC and find out the ISA DEV, which I then can enter to the Adacalc to know, finally, my TAS (also according to mach). But many times the SAT in changing during CRZ (sometimes a lot) -> then also the TAS is changing -> I would prefer to fill the cruise airspeed in mach into the FPL, but it's impossible (only knots).To the updates: So if the update cycle is unable to be successfully downloaded/updated (no/slow internet connection), then it will just wait till the next download (in the next 5 min.)? But now it seems to be OK, btw. the truth is that I was having problems with internet connection during my flight yesterday -- sometimes I was disconnected from Wifi or it was very slow -> then it's no wonder that I was having problems with AS updates. I'll try to improve the Wifi connection and have some flight to check it.Thank you,Adam

[Adam4171 0]

Now I'm cruising in F370; according to the AS, the SAT should be here --55 °C, but when I look into FMC, I see --60 °C -> different ISA DEV -> still different TAS; i calculated the TAS using an upper mentioned tool -- and the TAS I should fly was 450 kts and I have now TAS 444 kts. I really don't know why the SAT is not showing correctly (in AS / in PMDG 737 NGX), but I would really like to fix that…Adam

[Jet_Airliner 0]

First of all, I use Aerosoft FSC9 for making Flight Plan for Active Sky and PMDG.Then I go to active sky and open this flight plan. And I change just the Flight Level and add alt. airport. You don't have to put anything into speed.That's what you put for wind at desired flight level and temperarure to get isa dev.If the SAT changes in flight - it's normal behavour. Especially in winter there are many huge cyclones, so the atmosphere is very unstable.

I would prefer to fill the cruise airspeed in mach into the FPL, but it's impossible (only knots).

You mean vatsim flight plan? Just use the average value from adacalc! That doesn't change anything. It's just a forecsting and planning. In flight many things change. You might change flight levels due to turbulance, traffic and other stuff, so the values are changing.All above is for calculating the fuel, because it's important to take the wind and temperature in account. If the flight is very long you can get to the destination with tailwind, but on the way back you have to refuel somewhere because of headwind.

[Adam4171 0]

Hi again, sir!Well, now it seems to be more clear! Thank you!I have also been using FSC, I have just tried to save my FlightPlan, and when I click on Import in AS and select the FPL saved from FSC, it just doesn't work -- the cursor just skips to Alternate ID box, but the DEP and DEST airports boxes stay blank (so I cannot to create the FPL)… But If I try to open the .fpl in FSC again, it was working. Don't you know why it's not working?Btw. yes, I mean Vatsim FPL -- I file it via the Vatsim FPL website and there's no possibility to enter e.g. M078 in the cruise airspeed (-> then it's showing the ATC "0". But as you wrote -- it's just for forecasting and planning and even in winter it's very probable that the values will be during flight (even if it's a long flight) changing.

Edited February 6, 2012 by Adam4171

[Adam4171 0]

OK, I have found it out! :) I hadn't been saving the FPL in FSC as FSX format… :) Mea culpa.… and that's what I didn't know before -- I thought that AS only could create flight plans using VOR or NDB navigation; but now I know that for every weather-planning of the flight, I'll save the route in FSC (in FSX format) and then it's gonna be working for 100 %! ;-) (Using the averages, which btw. I can now also see there under the waypoints table.)So, as soon as I fly somewhere tomorrow (I hope), I'm going to plan it carefully -- with using AS and FSC (+ Adacalc); so now I hope it should be alright (but the truth is, which I had not realized before, that it's winter and the weather now changing a lot -- cyclones, winds, icings, etc. --).… we'll have to wait for summer for the most accurate values! :–)So, I think my problem is solved (if there are some problems again, I'll post them). ;-)THANK YOU VERY MUCH!!Adam