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LoganCastle

PMDG 777 KSFO 28L Threshhold Problem

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In the PMDG 777 when crossing the threshold on runway 28L at KSFO the aircraft crashes into something that is invisible when the approach is slightly low or shallow. After hearing the "thump" of hitting something I immediately pause the sim and go outside and see the aircraft is about 30 to 50 feet above the runway. I unpause and watch from the outside to see the nose drop to the runway and the nose gear collapse. It's broken. Baro/alt is about fifty feet. Radio/alt is at -2 feet after touchdown. Can the radio/alt ever legitimately be negative? Sometimes a cloud of dust is kicked up from the invisible obstruction. I see nothing wrong with the terrain image and nothing wrong with the runway image. Can the radio/alt be set to a higher value? Or are the values given by the radio/alt being misread by the KPMG model? Or what? Thanks in advance.

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In the PMDG 777 when crossing the threshold on runway 28L at KSFO the aircraft crashes into something that is invisible when the approach is slightly low or shallow. After hearing the "thump" of hitting something I immediately pause the sim and go outside and see the aircraft is about 30 to 50 feet above the runway.

 

Hi, Logan,

 

Are you using addon scenery or an addon AFCAD?  I have landed at KSFO 28L many times using default scenery -- some landings well below the glideslope ( :mellow: ) -- and have never experienced this problem.  Another thing, since I don't run Autogen much, if your Autogen is on try turning it off to see if the problem goes away.

 

One other thing occurs to me:  sometimes if the aircraft hits the ground or water (with crash detection off) it bounces back into the air.  So if you are not looking until after the thump, maybe you are hitting the water or ground too hard but by the time you look the aircraft has bounced up again.  If you have video recording software, record it and take a look at where you are on the PFD just before/during the thump.  Also, an FS-Recorder (freeware) recording should show from external view where the aircraft was just before the thump. 

 

Edit:  Instant replay should work well enough to see if it is bouncing as well.

 

You are not flying in Asiana livery are you?  Maybe that livery has this crash built in! :rolleyes:

 

Mike


 

                    bUmq4nJ.jpg?2

 

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Radio/alt is at -2 feet after touchdown. Can the radio/alt ever legitimately be negative?

 

Yes.  I forget the actual physics and location of the whole thing, but the radio altimeter is set up in such a way that when the plane settles fully, it will show a negative value.

 

 

 


Can the radio/alt be set to a higher value?

 

That's not the issue, really.  All that would do is give you a higher indication.  The plane wouldn't actually be higher, or fly higher.  When tracking the glideslope, it's following that signal.  While it does receive input from the radio altimeter, it doesn't quite provide guidance enough to fix this issue.  Sounds like a scenery issue.

 

 

 


Or are the values given by the radio/alt being misread by the KPMG model? Or what?

 

The who now?  Have audits and taxes on the mind?  :P


Kyle Rodgers

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This sounds like a scenery problem, not a PMDG 777 problem. Perhaps your needs will be better served posting this in a scenery forum?


Matthew Bellette

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Assuming it is Flightbeam KSFO, I have the same problem n a PMDG 747 but never find out the root of the issue. Temporary solution: land on 28R.


Danny F

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I'm not sure about how to reply to replies in this forum, so someone clue me in if you would. I initially had the problem with plain old vanilla FSX scenery and then thought maybe there had always been a problem with that so I tried an add on. Same thing. Then I went back to old FSX. Same thing. But if the elevation of the scenery at the threshold were too high wouldn't it show as too high in the sim visual? It looks fine. The aircraft looks fine. I don't know how the sim is written but there must be something that is there to detect when the aircraft is at the runway level to make them come together as a landing. The baro/alt and radio/alt reports the information correctly to the instruments and is displayed correctly and the bay/seawall/runway correspondences seem to be right but interference detection seems to fail. PMDG interference code may be sensing that the threshold and aircraft are trying to occupy the same space at the same time when they are not, in fact. So, are the altimeters reporting ok to the sim math but a decimal point is out of place? This may be unintelligible, if so I will try to clarify if asked. And some of you have noticed that this may be about AAR214, and it is. The irony is striking, ain't it!? Pun intended. Did 214 hit an invisible dirt pile? Hate those things! Yeah, KPMG, senior moment.

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http://www.youtube.com/watch?v=BVUdYjBnugs

 

 

I had a similar problem with planes dropping 60 feet instantaneously at the threshold.  It usually  occurred over a runway with water before it - like 28L.  See Youtube video of my crash.

I was told it was a mesh problem and ZI needed to reduce mesh to 18. 

 

 


Paul Gugliotta

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I'm not sure about how to reply to replies in this forum, so someone clue me in if you would.

 

You can highlight a part of someone else's reply and then click on "selective quote."  That is what I just did.

 

 

 


I initially had the problem with plain old vanilla FSX scenery and then thought maybe there had always been a problem with that so I tried an add on. Same thing. Then I went back to old FSX. Same thing. But if the elevation of the scenery at the threshold were too high wouldn't it show as too high in the sim visual? It looks fine. The aircraft looks fine.

 

it is very possible for there to be something in the scenery that is not visible but still registers in the sim as an object.  You should click on "Ignore crashes and damage" in Settings-Realism and see if that fixes the issue.  More than once I have had a long flight, good landing, end with an FSX crash due to some invisible obstacle at the arrival airport.

 

I am almost certain this has nothing to do with the aircraft, radar altimeter or anything like that.  You need to be sure that you don't have an AFCAD installed somewhere, as I've never had this problem with default scenery and apparently other people haven't either.  Take a look in Addon Scenery/Scenery, or Flight Simulator X/Scenery/Global/Scenery or Flight Simulator X/Scenery/World/Scenery.  If that doesn't work use Windows Search to search for any file anywhere in FSX that includes SFO in its name and ending in bgl. 

 

 

 


And some of you have noticed that this may be about AAR214, and it is. The irony is striking, ain't it!? Pun intended. Did 214 hit an invisible dirt pile? Hate those things! Yeah, KPMG, senior moment.

 

I'll bet that's an excuse Asiana's pilots and officials haven't thought of!

 

Mike


 

                    bUmq4nJ.jpg?2

 

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when you search for SFO.bgl, you may have to also look at hidden files. I say this because I found an errant file lurking out of sight years ago


Rob Marton

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Ok, I just tried several approaches to SFO 28L, with crash detection and allow collisions with other aircraft on, maxed out autogen, ultra high scenery, full air, ground, vehicle, boat, etc. AI, still no interruption on short final at SFO.  (Didn't use Asiana livery though! :rolleyes:) So I'm still thinking an AFCAD, or possibly as Paul G said a mesh problem.  Do you have any mesh or other scenery for the San Francisco area aside from the airport itself?

 

Mike


 

                    bUmq4nJ.jpg?2

 

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Funny you mention Asiana. I've started flight 212 RKSI to KSFO in the PMDG 777. Let's see what happens. I'm using Flightbeam's KSFO scenery. I'll report back.

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It has to do with the mesh settings I believe.  I had identical problems when approaching runways that were right next to bodies of water (St Marten for example).  I saw this fix on a Youtube video with a user with the same problem, and turning off crash detection would only result in the aircraft instantly slamming to the ground at the point where it would've crashed. I believe that the mesh resolution setting has to be set to 19.  Try it, it fixed the problem for me.


Mark Javornik

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Many good pointers, thanks a lot. I need this to work badly so I'm hell bent and exhausted on it. So I looked a little closer and I believe I isolated the cause but don't know what to do about it. If I approach the runway low (3 red on PAPI) just as I cross the threshold the runway jumps up about 30' or so and actually strikes the nose gear since it is the only part over the runway at that point (my angle-of-attack is good so why nose gear damage). That explains why I end up with a lot of collapsed nose gear instead of damage of other sorts. This also clears up why it only happens on sharp angle glide slope approaches. It probably happens at a normal angle also but it jumps too quickly for me to see and causes no damage. It would also explain why (as someone mentioned) it seems to happen on over-the-water approaches. There is no way for the scenery designer to taper the water . It seems to come down to this. The airport threshold elevation and the approach terrain elevation are misaligned. When I checked the field elevation for KSFO it seems to be specified as 13'. The altimeter in the airplane reads about 25'. If there were a way to lower the entire airport to align it with the terrain I think it would be solved. BUT I don't know how. Are airfields level so that all thresholds are at the same altitude? Are there airport add-ons that have runways that follow the terrain so all thresholds line up with the surrounding terrain.?  Thanks for all the good pointers.

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