X-Plane Technology Preview One

[Gilandred 690]

1 hour ago, rka said:

XP has nothing of PMDG quality (no, flight factor is not on PMDG level).

Not true.  LES Saab and IXEG 737 are absolutely up there in terms of PMDG-esque quality.  The Toliss buses are probably up there as well.  May as well throw in the Hotstart TBM, and REP packages for GA.

Edited June 7, 2021 by Gilandred

[Gilandred 690]

1 hour ago, rka said:

XP has nothing of PMDG quality (no, flight factor is not on PMDG level).

Double post.

Edited June 7, 2021 by Gilandred

[Janov 2,383]

1 hour ago, Alec said:

X-Plane does the same but using Height over the Runway as a Slope for the XWind component to be way lower by the time you get near to touchdown. This Slope has been demonstrated to be way more agressive than some documentation on how the wind surface should behave in real life.

I dug around a bit and found this:

https://www.semanticscholar.org/paper/Estimation-of-wind-speed-profile-using-adaptive-Mohandes-Rehman/85ed09555b460aeefe468ecf6888cf9699d6f3da/figure/5

The typical wind measurement is taken at 10 meters. The height of the vertical fin of a C-172 goes to 2.7 meters.

X-Plane will reduce the reported wind by about 40% for a C-172...that seems to fit the prediction pretty well.

Cheers, Jan

 

[Alec 370]

3 hours ago, HumptyDumpty said:

Huh , are you that same Alexis from discord ? 

If you are that lazy Mig21 Looser Pilot I heard of, then it's not me 🤣

2 hours ago, Janov said:

I dug around a bit and found this:

https://www.semanticscholar.org/paper/Estimation-of-wind-speed-profile-using-adaptive-Mohandes-Rehman/85ed09555b460aeefe468ecf6888cf9699d6f3da/figure/5

The typical wind measurement is taken at 10 meters. The height of the vertical fin of a C-172 goes to 2.7 meters.

X-Plane will reduce the reported wind by about 40% for a C-172...that seems to fit the prediction pretty well.

Cheers, Jan

 

Interesting,

I don't have access to the material I referenced anymore, Jose, by working at an meteorology institute, probably has way more info to share on this subject, but since he is now on vacation, it will have to wait. But if I remember well, it was not as agressive as X-Plane does, and happens much later than 10meters to be so significant as is in X-Plane.

How reliable are the IRS Calculation on a 737, for Wind Vector and Speed? You should know pretty well.

https://youtu.be/zuLnXwg5R7c?t=113

Looking at this video, it's only at 10 feet that the wind will start reducing from the 24knots it stayed during the entire approach. So + or - 3 meters. But I don't know how reliable this information is.

[Janov 2,383]

12 minutes ago, Alec said:

How reliable are the IRS Calculation on a 737, for Wind Vector and Speed? You should know pretty well.

They are fairly reliable - but subject to some factors like inertia and beta (sideslip angle). Since the wind information is the difference between IRS and ADC speed vectors, it is just an indirect indication of actual wind speed that is a bit laggy (kinda like a conventional variometer).

Also consider that a 737 is substantially taller than a Cessna 172, reaching around 12 meters at the tip of the vertical stabilizer - so the reported wind (measured at 10 meters) is pretty much the same wind you will read off on the nav display just as you touch down. The velocity change ABOVE the 10 meters is much more gradual than the one below (as you near the ground).

Cheers, Jan

 

Edited June 7, 2021 by Janov

[Bjoern 1,157]

I just hope that XP12 will pull me out of my flightsimming depression. Nothing is fun anymore.

[jcomm 5,919]

Alexis, thank you for your kind words !

I'm actually on vacations, with reduced access to internet ( by option ) and very limited access to aviation weather docs, but this wikipedia link is good enough.

Wind gradient - Wikipedia

including the Hellmann exponent.

In soaring it is very noticeable, and on some gliders a moderate x-wind component can really become tricky during the last phases of landing and on early takeoff.

The LS1c I sometimes fly even calls for the use of full spoilers with moderate x-wind, progressively retracted as speed increases during the towed  takeoff, and before leaving ground, because the turbulent airflow helps with bringing the ailerons alive sooner and avoiding some really bad experiences...

A well known accident occured in 2010 with a Fox aerobatic glider making a landing under really strong and gradient intense wind. The experienced / seasoned aerobatic pilot was, thankfully not injured:

Shoreham Airshow 2010 Glider Crash - YouTube

Edited June 7, 2021 by jcomm

[Humpty 751]

7 hours ago, Alec said:

If you are that lazy Mig21 Looser Pilot I heard of, then it's not me 🤣

 

Yeah that's me ! 

[jarmstro 2,402]

10 hours ago, Gilandred said:

The Toliss buses are probably up there as well.

Both the Toliss aircraft are my favourite airliners in X-Plane. However in terms of the visual modelling they are actually quite poor. (Check out the nose cone, the low polygon count on curves and the seams on the wings where they flex for just three examples.) Indeed they are visually far below the standard of the default A320 in MSFS and A320nx with its cockpit improvements.

Edited June 8, 2021 by jarmstro

[mjrhealth 820]

But thats teh problem its not about flying is it, im surprised how much  ** put up with from users, not enough rivets, it off by 2 mm, get over it  not even real planes are perfect. Especially after a year or so of service. But people need to complain to justify there existence.

[Janov 2,383]

11 hours ago, jcomm said:

including the Hellmann exponent.

In soaring it is very noticeable, and on some gliders a moderate x-wind component can really become tricky during the last phases of landing and on early takeoff.

It looks like X-Plane is using the Hellmann exponent for "neutral air above human inhabited area" or about 0.4.

A 10kt wind at 10 meters height is reduced to 4,7 kts acting on the Cessna 172 sitting on the ground.

Changing to the 737 this changes to a wind of 6,7 kts.

I believe the wind indicated in the DATA OUTPUT is probably the wind acting at the center of gravity of the aircraft...but I believe I remember Austin stating that he is actually calculating the center position of each airfoil to determine the wind effect.

 

Edited June 8, 2021 by Janov

[Randall 82]

Very interesting conversation. But I think we exhausted the topic of this thread…..

[Janov 2,383]

1 hour ago, Randall said:

But I think we exhausted the topic of this thread…..

Not by a long shot! 😋

[mSparks 2,086]

4 hours ago, Randall said:

But I think we exhausted the topic of this thread…..

Just because the preview one left you speechless doesn't mean we can't start speculating when preview two is gonna drop.

[mSparks 2,086]

like, for.... example