aaronkia

Strange hard landing/gear behavior on touchdown

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Hello, 

I've been experiencing weird behavior on both the -400 series and -8. Upon touchdown the aircraft seems to almost slam down onto the runway. This does not happen when the outer set of wheels make initial contact but only when the inner set of wheels make contact. I cannot replicate the problem and it is not unique to one particular scenery. I believe it is a similar issue previously reported in this topic: 

 

I have also attached some videos of the problem I am encountering.

Kind regards, 

Aaron Kia

 

Edited by aaronkia
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I think you are over rotating.  Rotation is no more than 3 deg nose up from approach attitude.

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Hi Dan thanks for the reply. While it is a possibility I am over rotating, it doesn't explain why this happens sometimes and sometimes doesn't as I am landing with the same technique each time. Here are another two videos of landings with the same  flare but no weird behavior: 

Aaron Kia

Edited by aaronkia
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In my experience, odd simulation behavior in and around the runway such as during approach or the initial climb out characterized by a unexpected change in aircraft altitude has always been related to the scenery and mesh.  As an experiment, set up a trial where the behavior is the same each time, then change your terrain mesh resolution.  It's just a test... if you can create the test conditions that are predictable then changing variables may help figure out what's happening.  If you cannot create a trial where the behavior is the same each time then I'd be suspicious of your pilot techniques and take a closer look at those.

In all the beta and normal use of the B744/748 I personally have not encountered such problems except one event months ago at a location that I've forgotten about it seemed like on takeoff about the time V2 is achieved the aircraft seemed like it instantly lost about 50 ft of altitude without any change in speed or pitch.  I forgot about it and never when back to investigate and it never happened again.  I've not had similar events landing and that is over a period of time where I've accrued 202 B744/748 flights according to my logbook.

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Yes I thought it may have something to do with scenery/terrain as I remember once also having a similar issue when approaching KSFO when the water and land intersect the aircraft suddenly fell out the sky. It's just weird how intermittent it is but at least it's only happening about 3 times out of 10 I'd say. 

 I'll have a play around with settings and report back if I find any correlations. Likewise I'd be very grateful to hear if anything springs to mind for you too. Many thanks for your help. 

Aaron Kia

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I have a similar problem often - if you find out what causes it, please do report back! 🙂

 

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Yes, this very much looks like the same problem I was reporting in my thread. Aso here the pitch down seems to stop abruptly before the nosewheel touches down. From the cockpit this pitch down even looks more agressive.

I strangly did not get this behaviour over my last 5-6 flights, but  - to my knowledge -  I didnt change anything.

The only thing I can say is that it seems very unlikely to be mesh-related because this would in any case lead to the same behaviour at a certain scenery always and also to probably similar behaviour with other planes. Tests with diff mesh settings suggest to disregard mesh as a cause, too

Also I doubt landing technique is in play here actually, I saw it happening and not happening with very different types of flare.

 

best regards

 

Edited by Sekkha

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1 hour ago, Sekkha said:

Yes, this very much looks like the same problem I was reporting in my thread. Aso here the pitch down seems to stop abruptly before the nosewheel touches down. From the cockpit this pitch down even looks more agressive.

I strangly did not get this behaviour over my last 5-6 flights, but  - to my knowledge -  I didnt change anything.

The only thing I can say is that it seems very unlikely to be mesh-related because this would in any case lead to the same behaviour at a certain scenery always and also to probably similar behaviour with other planes. Tests with diff mesh settings suggest to disregard mesh as a cause, too

Also I doubt landing technique is in play here actually, I saw it happening and not happening with very different types of flare.

 

best regards

 

I completely agree.

For me the aggressive pitch down is only stopping just before the nose wheel touches down due to me pulling back on my joystick pretty quickly to prevent it slamming down. The inconsistency of the problem suggests it isn't a problem with scenery/mesh. My best guess is it is perhaps something to do with the way the two inner sets of wheels of the main gear are programmed (probably not the right word I know!) as it does not occur when the outer wheels make contact as seen in all videos above. 

Landing flare technique can also be disregarded as further testing showed with some example videos above that it does not cause the problem. 

I hope we/PMDG can find a solution.

 

Aaron Kia

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Please try an Autoland and manual landing without autobrakes and get back. 

From what I see that is a known problem with the real world 744 and 748 at brake setting 1, it will grab pretty harsh at the first application.

With a/b 2 and 3 should be smooth and 4 is also strong but not as harsh as 1. 

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Aaron,

I did a few landings and I agree with you 100%, there is something going on and I filled the discrepancy on "to do list".

When is gonna get fixed, I don't have an answer. All that I can say is that is on the list.

And also I have to apologize, I had this discrepancy on my list for about 2 month but I forgot to list it. 

Edited by killthespam
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Hi Alan, no need to apologise! Thanks for adding it to your list and hopefully a fix can be found 🙂 

I did think it could be related to the autobrakes but I can't seem to find a correlation between the autobrake setting and it happening. As shown in the video above with the Cathay Pacific cargo -8 at Sydney, the autobrake was on 1 but the issue didn't happen whereas in the BA -8 video at VHHH the autobrake was on 2 and it happened. .

Many thanks for your help,

Aaron Kia

Edited by aaronkia

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It is not uncommon for the real 74 to pitch down rapidly upon landing.  It's more todo with the Autobrake especially 3 or higher.  But spoilers also cause the aircraft to settle onto the ground rapidly when deployed. It's an aircraft that requires you to pay attention after touchown and fly the nose down. You should never let the aircraft just drive through nose in.  Good way to bend metal.

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Arron,

I'm sure that the fix will be addressed but when I don't know.

We're a few real world 744 and 748 pilots part of the tech team helped by beta people, our findings get sorted out by PMDG developers and programmers on a list. From there, priorities and decisions are in their hands.   

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