Having a weird intermittent problem with takeoffs.

[eslader 1,774]

This one's got me stumped. It's rare enough that I can't discern a pattern to it. I'll be on takeoff, usually in something big by PMDG but sometimes with the QW787 or something smaller like the Flysimware Falcon 50. As I rotate after VR, the nose instantly pops back down to the runway. I don't think it's a control issue (either in-sim or physical hardware), because if I'm at 10 degrees up, I'll go from 10 to back on the runway instantly, with no in-between. It does this over and over again until I run off the end of the runway. Usually if I quit the sim and restart the problem goes away, but that gets really annoying after spending 45 minutes getting a 747 ready to fly.

Running p3d 4.4 on Win10. Addons include Orbx base/vector, Flightbeam airports, Activesky. Any ideas? I did a search but didn't find anything.

[eslader 1,774]

Here: Made a really terrible video of the problem. Bad screen recorder that decided to record all 4 of my screens, so I cropped to the one P3d was on. That made the resolution horrible, but you'll get the idea of what's going on. Not like this is going on a demo reel. 😉

 

[Bob Scott 7,704]

Looks like what happens when you run into terrain, right as your mains traverse that crossing runway.  So I'm guessing there's some kind of uneven or noncontiguous terrain issue related to that crossing runway.  I'm wondering if there's a problem with the flatten the airfield sits on.

Does this happen at other airfields?  Is crash detection turned on?

 

[eslader 1,774]

Yes, it happens at other airfields, and no, crash detection is not turned on. Thing is, 9 times out of 10 if I reboot my machine, and then set up the same flight from the same runway, I'll take off just fine. 

It's kinda hard to see in the bad video, but I can always tell when this is going to happen because shortly before it slams back to the ground, there's a slight vertical bobble that the plane should not be capable of doing. In this video it happens at 0:50. If you frame-by-frame it you can see the plane settle toward the ground very briefly just before it reaches the cross runway. That is not a control input or a stall - that's the sim giving me the sign that it's about to screw my takeoff up.

 

Edited April 20, 2019 by eslader

[Bob Scott 7,704]

I think you're hitting a bump or a void in the terrain.  I'd look at terrain mesh resolution and tesselization settings, and any add-on mesh products or add-ons that incorporate terrain mesh.  If you have the mesh res set too high, for example, the interpolation process can produce some wonky anomalous defects in the terrain floor.  It may well be that reboots are a red herring...perhaps you're just missing those small bumps/holes on some of your takeoff rolls and hitting them on others.

Regards

[vgbaron 3,482]

Out of curiosity - turn crash detection on and try the flight - I'm thinking you will see a crash. As Bob says, that effect sure looks like running into terrain.

Vic

[Christopher Low 5,324]

What is your mesh resolution setting? I have noticed that this can happen if the resolution is set higher than 5 metres.

[Boeing or not going 578]

Even though Orbx Vector has a scanner to disable their files if you have an addon airport, I found APB_ .bgl files also need to be manually disabled for each addon airport I have. Also using mesh higher than 5m can cause it since some scenery developers do not supply a high resolution mesh to cover their airport. FSDT has bumps in their airport taxi and runways when using mesh slider to 1m.

[eslader 1,774]

Yeah, the mesh resolution is set to 1m. But here's the weird part. Now that I've got it fairly consistently having the problem, I've made sure not to reboot so I can do some testing.

Here's another vid, where I abused the plane by firewalling the engines so that it would rotate sooner. You will see that the same problem happens even though it rotates long before it did in the other vid.

This plane had max weight in the cargo bay, and then enough fuel to bring it to MTOW. Now, if I do the same takeoff, but empty out all the cargo and only put 10,000 pounds of fuel in, it takes off with no problem, even if I rotate it at the point where it slams back in the vid. So it seems to be related to when the plane is heavy. I didn't make vids of all this because that's a pain, but I can take off from other runways, and other airports, and the same thing happens - heavy, it slams back, light, it doesn't. 

Am I wrong in thinking that if it was a terrain problem, it should manifest no matter what the plane's weight is?

 

[Christopher Low 5,324]

My short 747 flights (circuits at a single airport) are with MEDIUM FUEL and ZERO PAYLOAD. I do not know where that puts it on the weight scale, but scaling the mesh resolution back to 5 metres effectively solves the problem.

Edited April 20, 2019 by Christopher Low

[Indy511 686]

@eslader

What airport are you at for the video?

Don't mean to be redundant but have you tried sitting the mesh at 5m? This is what Orbx recommends for their products. If the problem affects different planes and airports then it has to be the sim options settings somewhere.

Edited April 20, 2019 by BillS511

[Sethos 4,266]

20 hours ago, eslader said:

Here: Made a really terrible video of the problem. Bad screen recorder that decided to record all 4 of my screens, so I cropped to the one P3d was on. That made the resolution horrible, but you'll get the idea of what's going on. Not like this is going on a demo reel. 😉

Off-topic but you should check out Open Broadcaster Software. It's able to record as well, even using the Nvidia GPU hardware, plus you can select multiple modes of recording, like a specific window, monitor, application etc. and it's free. Just in case you ever need to record something again.

[downscc 1,327]

2 hours ago, eslader said:

Yeah, the mesh resolution is set to 1m.

I will have problems such as yours or even during a landing if my terrain mesh setting is further to the right than 5 m.  This problem has been around awhile and usually is quite common where the runway is near water such as CYVR, KSAN and VHHH for example.

[eslader 1,774]

Sounds good. I'll set it to 5m and do some testing over the next few days. Thanks.

 

To answer the airport question, it's KMSP by Flightbeam.

 

 

[Boeing or not going 578]

2 hours ago, eslader said:

Sounds good. I'll set it to 5m and do some testing over the next few days. Thanks.

 

To answer the airport question, it's KMSP by Flightbeam.

 

 

What happens when mesh slider is still at 1m but you disable this file?