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Guest Graeme Paterson

744 Cruise Phase - Loss of Airspeed/Altitude

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Guest Graeme Paterson

HiI have searched though the forum and come accross a couple of instances where my query was raised previously but I was hoping someone might be able to update me on the latest advice re a solution.I absolutely love the PMDG 744 and it is now firmly established as my aircaft of choice however whenever I attempt a long haul route - usually, but not always over an ocean - 1/3 to 1/2 way through the flight the aircraft will start to gradually bleed airspeed. After a short while when the IAS has reduced below something like 190 knots I start losing altitude and then get into an almost irrecoverable nose high attitude.I am using ASVE and having looked on their forum have unchecked all VAS options as suggested but I am still having the same problem with every flight I try to make.I really hope someone can help as the problem is ruining my enjoyment of which, in all other regards, is a super add-on.ThanksGraeme

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I had the same problem today. Don't know wat's causing it? But realy would like to now. It was the first time I had this problem. So, I guess it has something to do with the Stormy days we had the past week.

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If you at at OPT or near it then you should look at what type of WINDS you have coming at you from ASVE. [h4]Randy J. Smith[/h4]AMD 64 4000+|ASUS K8V DELUXE|SAPPHIRE ATI X800XT PE|MUNCHKIN 3200|80 gig SATA|DELL 1905FP 19" LCD|TRACKir PRO|PFC JEPPESEN MOONEY YOKE|CH PRO PEDALS|


Randy J Smith

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Guest lou ross

I believe that this is rather common. It seems to be a real prob flying westbound, but not much of a prob flying eastbound. Only solution I've found is when you definitely see you're losing airspeed, descend at 400 fpm for 2000 feet, maybe 4000 feet, level off and the speed usually picks back up. Sometimes you need to keep descending. When the speed is increasing, climb back to your original alt. I also had this happen, but not as pronounced, with the DF727.louross.

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Hello,this issue was discussed at great length with numerous inputs in the old but still searchable forum. I'll give you a combination of the party line and then my input which PMDG had overlooked:1. This is likely to happen when the weather changes unrealistically fast, such that headwind component decreases rapidly. PMDG rightfully suggested to ensure weather changes are realistically gradual. That forum suggested settings to ASV/FSUIPC.2. At OPT ALT in CRZ thrust, the excess thrust available is too low, around 5% N1 average. I have no real B744 data but suggested on that forum that the excess thrust be reviewed. On top of the remedy in item 1, I set the cruise thrust mode to CON. It makes available 5% more N1 when necessary for the aircraft autoflight system to recover from such situations, without violating any aircraft operation limitation. I will use this till the issue is fixed.>Hi>>I have searched though the forum and come accross a couple of>instances where my query was raised previously but I was>hoping someone might be able to update me on the latest advice>re a solution.>>I absolutely love the PMDG 744 and it is now firmly>established as my aircaft of choice however whenever I attempt>a long haul route - usually, but not always over an ocean ->1/3 to 1/2 way through the flight the aircraft will start to>gradually bleed airspeed. After a short while when the IAS>has reduced below something like 190 knots I start losing>altitude and then get into an almost irrecoverable nose high>attitude.>>I am using ASVE and having looked on their forum have>unchecked all VAS options as suggested but I am still having>the same problem with every flight I try to make.>>I really hope someone can help as the problem is ruining my>enjoyment of which, in all other regards, is a super add-on.>>Thanks>Graeme


Regards, Opher Ben Peretz

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Guest Graeme Paterson

OpherI did review the Active Sky forum at length and have changed my FSUIPC settings to ensure all wind shifts / pressure changes etc are as gradual as possible but with no success.I will now try the change you suggest re setting Thrust mode to CON and see if this helps.ThanksGraeme

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Graeme,What is your weight and what altitude are you flying at? It might be as simple as trying to fly at an altitude too high for the gross weight. Hope it helps,


Mats Johansson
PMDG Flight Test Dept
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Guest Graeme Paterson

MatsVarious weights and altitudes. I use the PMDG 744 Load Manager to set up weights etc for each flight and then will set my cruise altitude to align with (or usually be slightly lower than) the OPT as indicated on the aircraft's FMC after I have loaded in all the appropriate data i.e. flight plan, ZFW etc etc.

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This is my report of a flight from WSSS to EDDF.Remember I don't have the registered version of FSUIPC.Planned a step climb after each 2000 ft and my initial altitude was FL300 which was the exact OPT. Alt for my weight (nearly 398 Tons) when I finaly got to FL360 around OIII (2/3 of flight past) My troubles started. After a while, flying at FL180, I was able to fly to FL380 for the new Opt alt. but nearly ended up with 6 Tons of fuel remaining at EDDF. I had 235 passengers onboard with around 25 Tons of freight. ASVE is my weather program. So, once again, I and Greame ask the same question again: Wat's causing it?

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Have either one of you by chance tried turning off ASV, and setting FS9 weather to clear. No winds, no clouds, no nothing and then seeing what happens?Not saying it will fix it, I'm just curious to see what will happen if you do.


Mike Roth

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Guest Graeme Paterson

Ive just completed a flight from KLAX to PHNL.As suggested by Opher when i reached the Cruise altitude I deselcted VNAV and selected SPD with Mach set to 0.86. I managed to complete the flight without any trouble. On a couple of occasions I actually noticed the airspeed start to bleed off however the engines responded by spooling up very quickly, and to a higher N1 % than I believe would have been the case under VNAV, with the result that the airspeed quickly recovered to the selected value and no altitude loss was encountered.I will try another longer flight sometime this week (if i can find the time) and report my results but it looks as if the problem may be overcome, as a short term fix, by flying the Cruise phase under SPD and not VNAV.Still dont know why it is happening mind you. I also fly long haul, trans oceanic, flights routinely with the LDS767 and have never had any problem at all.RegardsGraeme

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I have flown allot with ASVE and never had this problem before..I did infact tried flying without a 3rd party sofware and cleared all the WX, no problems.

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I specialy looked after the temp. and there were some changes of 2 degrees +/-And I'm looking forward to that new release because I think it has to do with ASVE and not with PMDG.And since I like both products realy much, I hope the problem get fixed then. :)

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Today I was flying from KMIA to KSEA I leveled off at FL350. LNAV was tracking my course perfectly and autothrotles were holding a solid 340KTS and ALT was set at FL350. I went away for 30 minutes (bad pilot) and when I returned, I was reduced to cinders. Either I went overspeed or my speed decayed and I stalled. I had fuel set at 150,000 lbs and ZFW at 347,000 lbs.


Paul Gugliotta

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