[REPORTED] serious headwind/tailwind bug - Page 4 - ED Forums
 


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Old 01-12-2020, 03:19 PM   #31
bbrz
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Quote:
Originally Posted by Mr. Big.”Biggs” View Post
Thinking out loud. Flying into a head will increase the speed of wind thus amount of lift under your wings..
No. That's a common misconception. (Steady) wind has absolutely zero effect on an airplane in flight except for ground speed and track over ground.

Concerning kites; I kite is connected to a fixed point on the ground, so it's not even remotely comparable to an aircraft in any case.

Furthermore lift is usually created above, not under the wings.
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Old 01-12-2020, 04:20 PM   #32
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Quote:
Originally Posted by Mr. Big.”Biggs” View Post
Thinking out loud. Flying into a head will increase the speed of wind thus amount of lift under your wings but could potentially decrease your relative airspeed. The opposite is also true no? Strong tail wind along with fast relative movement of the plane decreases the amount of wind going under the wing decreasing lift??
Kind if like flying a kite. When you pull it upwind or hold the string, it stays put and climbs. However if the string breaks, the kite “flys” downwind but looses altitude and hits the ground.
Not suggesting I have your answer, just trying to think thru it....
That would be true if the airplane was pulled on a string by a man with his feet on the ground with equal ground speeds with and against the wind. If there is 10 knots of wind and the airplane flies back and forth at 100 knots ground speed each way then yeah, it's going to be 90 knots of airflow one way and 110 knots of airflow the other.

But that's not how unaccelerated vehicles propelling themselves through a fluid medium act. For a given power setting flying back and forth it's the airspeed that's constant and the ground speed which varies.
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Old 01-12-2020, 05:10 PM   #33
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Quote:
Originally Posted by Deano87 View Post
Has anybody actually a PMed a mod so they see this report?

Also BK. Post a track of you getting RPM changes as you go through a different wind layer.
Hey Deano, I would but I saw this effect on the AO server, a track of that would be pretty useless.
Maybe I can re-create it in a single mission.


EDIT: couldn't re-create the RPM fluctuations in SP, however I tested with headwind/tailwind and there is indeed a difference in both top speed and fuel flow.

at 11.000 ft with a 97kts tailwind: top speed 518 kts, fuel flow 3300lbs per engine
at 11.000 ft with a 97kts headwind: top speed 510 kts, fuel flow 2800lbs per engine.
Attached Files
File Type: trk F-5 wind-engine-bug.trk (1.62 MB, 21 views)
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Last edited by bkthunder; 01-12-2020 at 05:50 PM.
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Old 01-13-2020, 04:26 AM   #34
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Originally Posted by bkthunder View Post
EDIT: couldn't re-create the RPM fluctuations...
As mentioned a few times already, the rpm difference isn't noticeable at high speed where the engine is apparently operating at or close to max rpm.

Suggest to run the test again at 250kias.

Last edited by bbrz; 01-13-2020 at 09:54 AM.
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Old 01-13-2020, 12:09 PM   #35
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Originally Posted by bbrz View Post
As mentioned a few times already, the rpm difference isn't noticeable at high speed where the engine is apparently operating at or close to max rpm.

Suggest to run the test again at 250kias.
I don't see the RPM changes, however, I did a further test (track attached) and the difference is absolutely enormous!

Set up was: wind 97 kts
Engine RPM: I maintained 80%
Altitude: 11.500 (inside the wind layer I set up)

head-wind: the airplane cannot sustain flight with engines at 80%, the speed drops below 150 and keeps dropping.

Tail-wind: I can reach 400kts with engines at 80%.

Man, ED really needs to take a look at this!


EDIT: just tested, the F-16 has the same issue. will post in the relevant section.
Attached Files
File Type: trk F-5 wind-engine-bug2.trk (2.89 MB, 20 views)
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Last edited by bkthunder; 01-13-2020 at 12:26 PM.
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Old 01-13-2020, 01:43 PM   #36
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Maybe ED has 'corrected' the rpm problem, but by doing this they apparently made the problem even worse.

It's very disappointing that the F-16 suffers from the same problem.
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Old 01-13-2020, 01:50 PM   #37
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Always learning. Thats why I like this place.
Cheers!
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Old 01-13-2020, 11:58 PM   #38
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Reported guys, thanks.
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Old 01-15-2020, 06:03 PM   #39
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Can you try the F-5 again, and if you are still seeing issues send a new track and Mission, I am currently not seeing the issue. Thanks.
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Old 01-16-2020, 09:45 PM   #40
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Hello,


Roughly reproduced this bug.


SP mission with F-5 and A-10A (since it has thrust issues too).


Wind @75kts from 000 at all alts except at surface (33kts).


Spawned at 11.5K'. Unable to maintain speed or altitude into the wind at 000 HDG at 82%Ng.



Turned to 180 HDG, advanced thrust to get back to ~11.5k and stable, then reduced power again. Able to comfortably maintain 250kts IAS and 11.5k'.



Turned back to 000HDG with no changes to inputs, unable to maintain altitude or speed at 82%Ng.



Including track with A-10A flown on same profile for reference.
- Note 1: A-10A does not appear to have the same bug.

- Note 2: I noticed I could not get more than 83% N1 even at max throttle input, which is odd. Engines being anemic is one thing, but I know the TF-34 gets most of its thrust from the fan so I'll see if I can find some charts for N1/N2 speeds.
Attached Files
File Type: trk F5ThrustCheck.trk (442.0 KB, 16 views)
File Type: trk A10ThrustCheck.trk (796.3 KB, 13 views)
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