PMDG 747-400 cannot increase the speed effectively

[Guest dogdog1985]

Most of the time, I use 747 to fly Pacific Ocean to USA from HKG. The wind speed at Pacific Ocean can change very suddenly. yesterday, i flew to KSFO from VHHH. The wind speed suddenly change from -20knots to +100knots in around only half minute. The 747 nearly stall because of losing airspeed. So I increase the thrust to G/A mode, however, the 747 did not respond quickly to increase the speed again the tailwind. And it has a N1%-=102%, but the airspeed did not increase a lot.So, what 's the problem in PMDG??????

[michal 44]

Didn't you ask the same question before? There were numerous threads on the subject of sudden wind speed change. I suggest using the search option. And I don't think it is PMDG's "problem" since such wind gradients do not happen in real life outside of pockets of really violent weather so I suggest you do something about your weather program. Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

[Qavion 19]

In the real world, in VNAV, in cruise, I hear that the throttles are designed not to respond to speed changes as rapidly as in other flight phases (If it did, the autothrottle servo would wear out very quickly, hunting for exactly the right speed).Perhaps in the real world with a sudden wind change of 120 kts, the aircraft WOULD stall?Which would you prefer?Cheers.Q>

[Tabs 2,790]

There's absolutely nothing we can do if your weather program is injecting 120 knot windshear into the environment. I doubt the real plane would make it out of that.

[Headley 26]

Patrick,What you can do is with FSUIPC (registered version) enable wind smooting. I set a wind smooting of about 2sec for 1 knot (speed/direction) change.This may delay the speed of wind changes in your weather program and give your plane the time needed for adapting throttle settings to these new windspeed/direction.Hope this helped.

[Guest SilverCircle]

>Most of the time, I use 747 to fly Pacific Ocean to USA from>HKG. The wind speed at Pacific Ocean can change very suddenly.>>>yesterday, i flew to KSFO from VHHH. The wind speed suddenly>change from -20knots to +100knots in around only half minute.>The 747 nearly stall because of losing airspeed. So I increase>the thrust to G/A mode, however, the 747 did not respond>quickly to increase the speed again the tailwind. And it has>a N1%-=102%, but the airspeed did not increase a lot.>So, what 's the problem in PMDG??????No, it's not a problem of the plane. It's a problem of the "real" weather, because in real life, you will never ever experience a wind change of this magnitude. From 20knots head to 100 knots tail means an airspeed decrease of 120 knots within just a few seconds - no wonder the aircraft will run into troubles, I guess a real 747 would aswell.The fix is to use wind smoothing. There are multiple ways to do this - registered FSUIPC can do it aswell as Active Sky and possibly other weather generation addons. Smoothing in that context means that changes in wind direction and speed will happen "over time" not immediately.If you limit wind changes to 1 deg/kt per second (or even slower), an absolute change of 120kts speed will take 2-3 minutes - much better than only 30 seconds and in that case, the plane should be able to deal with it.

[Jim Harnes 13]

Hmmmm...if memory serves winds aloft do not affect IAS - only speed over the ground. Of course, wind shear on approach is something else again.I've long believed the IAS variations associated with FS wind shifts represent a fundamental flaw in simulating real flight.Jim

[Peter Clark 21]

When flying real aircraft turbulence and other sudden windshifts make the ASI bounce with dependable regularity. The issue isn't that shifting winds make the airspeed change, but that in real life you don't cross a mythical border from station KBOS to station KORH (for example) and have a wind shift in the order of 50+ degrees or 30+ knots. As you fly between those two points the windspeed changes and the direction changes gradually so there's no sudden jump, like loading a new reporting station in FS. That's where FSUIPCs smoothing functions kick in. Smoothing out those changes makes it much closer to real life, but still not perfect.

[Jim Harnes 13]

Indeed! Even FSUPIC can't stop the IAS going +/- as the wind aloft changes direction and speed.Jim Harnes

[michal 44]

>I've long believed the IAS variations associated with FS wind>shifts represent a fundamental flaw in simulating real>flight.I don't think there is any flaw here, at least not in aircraft simulation. Even in real life a sudden gradient in wind will cause your IAS to fluctuate. The point is that real winds aloft change their values slowly enough that you hardly every notice it. It all boils down to rather poor modeling of winds in FS.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

[Guest flightgamer]

I think a better question would be, 'What is up with FS?'PMDG has some of the best flight dynamics ive seen, i can hardly believe this is PMDG related....

[Guest thepilotny]

By the way, theres REAL situations when the wind could change in 20 miles radio between 60 to 120 head to tail.and perhaps 20 miles when you are flying at 0.80M is just a blink.This situation happen frequently in Hurricane Season in the Caribbean (off course all Airways in this path is no using for dispatch )just the Lockheed WP-3D Orion plane get into this business and they know about this wind changes for their records..and happy experience.

[michal 44]

>20 miles when you are flying at 0.80M is just a blink.Well, it is about 2.5 minutes so I would not call it a 'blink' and Lockheed's Orion definitely doesn't fly at 0.8 Mach so make it about 4 minutes. ;)Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

[Peter Clark 21]

And my point was that during that 20 miles the wind gradually shifts over that arc, it's not 000 one minute and then a new station loads and it's 180 the next, which is what causes problems in FS.