747-8 Slaming down on runway at take off

[Cyrille de LATTRE]

Good morning, I am experiencing very annoying problems with the 747-8 at take off. Before going into details of what I am doing to prepare my flights, everything is done and calculated by the book, I am a long time user and real aircraft experienced. That said at VR, when slowly approaching 9-10 degrees pitch up, just when you think your aircraft is at effective lift off, then the nose slams down on the runway. I have not experience this with the 747-4.

It is what I call systemic but erratic now. Yesterday I uninstalled the 747 and 747-8 and reinstalled everything, took of with the same weight real weather with ASP3D, went like a charm. then we had a power failure and I decided to test again, same condition, same runway, same weight same speeds, everything, and then boom, it happens again.

The only common thing there is when it fails is after V1 and before VR, you can see the speed tape slowing down by 5 to 10 kt, while the is no gusting winds.

for the record, GW was 978318 lbs, take of weight was 975318, V1 165, Vr 181, V2 194, 08L at LFPG, D-TO31, 96.6% Flaps 10 Trim 6.8 Performance calculated with the EFB

Win 10 pro 2004, P3DV4.5, ASP3D, REX SKY FORCE, Aorus Z390 // Icore 9900 Coffe Lake @4.8 Ghz // 32Gig RAM DDR4 // GTX1070 OC @112% core clock+200 memory clock +400) Corsair liquid cooling H105 Ipro

If any one as an idea, please tell me.

Thanks for your help,

Cyrille de LATTRE

[Extra300driver]

Cyrille hi you are not far off MTOW for the 748

Question:

- is this only an issue in VR?
- do you have the same problem with FLAP 20?

Is this only happening at LFPG or do you have the issue at other airfields? If you have not already done so, turn off crash protection in P3D

Sorry I am not of more help

Let me know how you get on

Adrian Howe

[Ephedrin]

It's not you. I described the same thing before and so did others and I'm pretty sure it's an incorrectly recognized tail strike. It would normally occure at 12.1° pitch in the 748 but it seems the system does it at around 10 degrees. I was told to reduce the mesh resolution but that can certainly not be the goal as many sceneries won't work correctly anymore.

Have a look here:

https://forum.pmdg.com/forum/main-fo...arp-down-747-8

I hope PMDG will work on this as even IF that's a tail strike it should still not smash down and reset the stab trim.

[Cyrille de LATTRE]

Cyrille hi you are not far off MTOW for the 748

Question:

- is this only an issue in VR?
- do you have the same problem with FLAP 20?

Is this only happening at LFPG or do you have the issue at other airfields? If you have not already done so, turn off crash protection in P3D

Sorry I am not of more help

Let me know how you get on

Adrian Howe

Thanks for the reply but nope, not in VR, I do not use this, and crash detection is OFF, and yes not far from MTOW, but even at MTOW it should not be a problem... Also it does happen not only at LFPG, but also in other places.

Cyrille de LATTRE

[Cyrille de LATTRE]

It's not you. I described the same thing before and so did others and I'm pretty sure it's an incorrectly recognized tail strike. It would normally occure at 12.1° pitch in the 748 but it seems the system does it at around 10 degrees. I was told to reduce the mesh resolution but that can certainly not be the goal as many sceneries won't work correctly anymore.

Have a look here:

https://forum.pmdg.com/forum/main-fo...arp-down-747-8

I hope PMDG will work on this as even IF that's a tail strike it should still not smash down and reset the stab trim.

Thanks for the reply... yes, but also I am just experimenting another flight, with a much lighter aircraft, 823Klbs TOW at LFPG, same weather, same runway, and no problem, bu I did not dare flirting with more than 9 degrees pitch, which led to an effective lift off close to V2 and I used more runway than I should. V1 160, Vr 162, V2 180, 26R, 58C D-TO flaps 10

Cyrille de LATTRE

[Ephedrin]

Jup I do the same. Very slow rotation and landing with some power left, that seems to help

[Pilatuz]

If I begin rotation AT V2, then 2-3° per second, I always am able to increase pitch beyond 12° if needed. You guys rotating slightly before V2?

[Cyrille de LATTRE]

You are supposed to initiate the rotation at Vr

Cyrille

[Pilatuz]

Yes, that's what I said. I rotate AT V2. I was asking if others weren't.

[DDowns]

Yes, that's what I said. I rotate AT V2. I was asking if others weren't.

No... by V2 you should be accelerating through maybe 15-20 ft, and at 35 ft be at V2+10. Start rotation at about 2.5 deg per second and at about 2 - 3 seconds you should be at initial takeoff attitude of 9 deg nose up (10 deg in 744) and continue climb out and rotation such that at 7.5 sec be at 11-14 deg nose up and 35 ft with V2+10 speed for initial climb. Tail clearance is good up to 12.1 deg and at a 9 deg nose up attitude with flaps 20 you have 43 in (109 cm) tail clearance with wheels on the runway and gear struts extended.

If you are getting tail strikes, and you are using the OPT calculated speeds and flap for your weight, then you are definitely over rotating. Do not wait for V2 to start rotation, the takeoff is a process not an event and a good clean and safe takeoff takes almost 8 sec to read 35 ft and V2+10.

[Pilatuz]

No... by V2 you should be accelerating through maybe 15-20 ft, and at 35 ft be at V2+10. Start rotation at about 2.5 deg per second and at about 2 - 3 seconds you should be at initial takeoff attitude of 9 deg nose up (10 deg in 744) and continue climb out and rotation such that at 7.5 sec be at 11-14 deg nose up and 35 ft with V2+10 speed for initial climb. Tail clearance is good up to 12.1 deg and at a 9 deg nose up attitude with flaps 20 you have 43 in (109 cm) tail clearance with wheels on the runway and gear struts extended.

If you are getting tail strikes, and you are using the OPT calculated speeds and flap for your weight, then you are definitely over rotating. Do not wait for V2 to start rotation, the takeoff is a process not an event and a good clean and safe takeoff takes almost 8 sec to read 35 ft and V2+10.

I am totally standing corrected my mistake, yes rotate at VR, that's what I meant but for some reason my brain was jumbled earlier when i read this post! Must have covid or something 😷

[Bluestar]

I left PGUM this morning at MGTOW, rotated at Vr to 10 degrees, held the 10 degrees until "positive rate", then watch the radar altimeter to make sure it's climbing, and then gear up. By them I'm through V2 then I chase the flight director to set my climb angle of attack. It works for me every time.

Please remember I'm old and easily confused. ROFL

[von]

Air Force One landing :
https://www.youtube.com/watch?v=Larlotxwl4A

Note: I posted this link in the wrong forum topic on accident.

[rsrandazzo]

Gents,

I'm seeing some discussion of rotation technique, and I want to chime in here:

The 747-400 and the 747-8 are prefectly prone to setting their tails on the ground if mishandled during rotation, especially when very heavy and (believe it or not) even more so, when light.

The proper technique is as follows: (this is from my notes during training on the 744):

"At start of takeoff, maintain slight forward pressure on the column, gradually reducing it to neutral at 80 knots. At Vr, rotate smoothly and continuously (max 3deg per second) to a target pitch attitude near 10deg. Early, or excessive rotation may trigger stick shaker or cause fuselage contact with the runway. WIth the main gear on the runway, tail contact will occur at approximately 11deg ANU. Proper rotation will result in reaching V2 at 35' AGL. Depending upon flap position and weight, the pitch attitude required to maintain V2 + 10 knots is approximately 15-17degrees ANU, but should not be attempted before reaching 35' due to tail strike risk."

This comes pretty naturally if you practice it a bit. Often when I watch simmers videos online, there is a tendency to pitch up and just keep pulling the nose higher and higher until the airplane leaps off the ground. That is a horrible technique, and shouldn't be applied to an airplane of this size. Rotate smoothly until you are 9-10deg ANU, then hold your pitch constant. The airplane is accelerating and it will leave the ground at it's own time and pace. You don't want to force it here- as she is in the proper attitude to fly- and when she is ready she will do so.

NOTE: All of the above goes out the window if you are attempting a Vmu maneuver. We can talk about that some other time.

[Traian Vuia748]

Robert,
I think that the guy who gave training is one with experience in tail strike real event (unfortunately).
We initiate a smooth continuous rotation towards 15 degrees of pitch attitude (not 10) at Vr with about 2.5 degrees/sec, in this way, there is no concern of any tail strike unless wrong calculated speeds, flaps, or problems with Weight and balance papers.
Absolutely an early rotation before Vr of more than 3 degrees/sec will get a tail strike, but again the pitch attitude that you get a tail strike for the 400 is a pitch angle of 12.5 not 11 or for the -8 at 12.1.
I guess the confusion about 10 degrees (actually 10.1 not that I can see .1 on the PFD, I use glasses) is the liftoff attitude for the 400 and only 9.0 degrees for the -8.
This training guy did a number on you guys, all I can say is that I'm sorry to hear stuff like that. I wonder why he didn't just follow the guidelines listed in the FCTM.
Anyhow, an interesting situation.

[Ephedrin]

Just right at this moment I‘m sitting here at the airfield in Klatovy, CZ with a former KLM 744 captain (being austrian he speaks german like myself so no language barriers) and let him read these comments. He said that he never deliberately stopped the rotation at any pitch but the 747-400 (he says he doesn‘t want to comment on the -8) at Flaps 20 and typical trans atlantic weights was quick to lift off at around 9 degrees. His comment is „the aircraft will naturally fly long before a tail strike occures as long as Vr is correct and you don‘t overrotate.“

[Captain Kevin]

(he says he doesn‘t want to comment on the -8)

I wouldn't blame him, given that KLM never had them, so I seriously doubt he flew one.

[Ephedrin]

I wouldn't blame him, given that KLM never had them, so I seriously doubt he flew one.

Hasn‘t flown the 8, that‘s why he can‘t say anything about it, but flew many airframes like Citation, MD80, Q400, 737, 767, 747-400 for various airlines and is now doing training on the SC-7 as his last emplyoment at a huge european low cost airline was degrading so he said. Cough... and he‘s happy to finally be back to real control

[Captain Kevin]

Hasn‘t flown the 8, that‘s why he can‘t say anything about it

I figured as much.

[skyteam78]

Unfortunately this happen to me today. I was departing rnwy 33 at Anchorage (PANC). Reaching Vr the aircraft started lifting off then after few seconds I suddenly found myself on the ground. Didnt see this behavior ever with other planes.

[Bluestar]

Unfortunately this happen to me today. I was departing rnwy 33 at Anchorage (PANC). Reaching Vr the aircraft started lifting off then after few seconds I suddenly found myself on the ground. Didnt see this behavior ever with other planes.

Pilot error. Every time you over rotate in the -8 there will be a tail strike. The deck angle can't exceed 10 degrees until there is a positive rate of climb (radar) and the gear has started up.

I fly out of PANC 3 or 4 times a month, usually at MGTOW on RWY33 using Aerosoft PANC and P3dv5 and have never had any issues.

[cavaricooper]

To follow RSR's and Bode's excellent advice, I will add that any of the longer fleet (777W, 747-8 and even the 737-900) benefit from a 2 stage rotation. I typically pull for 8.5 in those birds, allow for fly off (2 confirmed sources- RA + ALT climb/solid IVSI), select gear up and then pull for circa 15 and then V2+10 or 20 depending on deck angle. Works every time, give it a go... it's just muscle memory and will become second nature with some practice. Then you won't have to worry about all those skid touch-ups, let alone tea and soggy biscuits with the CP

C

[Sekkha]

Pilot error. Every time you over rotate in the -8 there will be a tail strike. The deck angle can't exceed 10 degrees until there is a positive rate of climb (radar) and the gear has started up.

I fly out of PANC 3 or 4 times a month, usually at MGTOW on RWY33 using Aerosoft PANC and P3dv5 and have never had any issues.

When will people finally understand and accept that the fact that they dont have an issue does not necessarily mean that there is no issue ???

What would you as a pilot think if an NTSB investigations would conclude "PILOT ERROR = YOUR ERROR" without knowing anything about what had happened ? But it is not just that. There are many reports here from guys which assure they do not over rotate and still have this nose down issue be it on landing or on takeoff. This means your conclusion is "PILOT ERROR" not only not knowing anything about the details but even willingly ignoring a lot of information contrary to your conclusion. I really hope you are not working for NTSB or a similar organisation

[DDowns]

I'm with Bode on this one... and I wonder why you offered your two cents. You are not the OP. Over rotating the -8 on both landing and takeoff is a pretty common issue in this forum, and comes up often enough to support this response as a reasonable one. By the way, the FCTM does use 11 deg as the liftoff rotation pitch, not 10 but that is splitting hairs.

[Sekkha]

Dan, with all my due respect, but I am wondering how exactly you are asking why somebody offers his/her 2 cents on a thread not being the OP....
But that aside.

Simple question: Do you know to how many degrees Gregory was roating to?

It is just not reasonable at all to argue in the following way:
1) I dont have this issue, hence there is no issue
2) Many people over rotate, therefore you did that as well, hence it was a pilot error

Like Bode you just willingly ignore all evidence of cases where over rotating was most likely not the reason for this behaviour. And I am talking about own experience.

[Sekkha]

This is how a tailstrike looks in P3D. The nose wont slam back to the ground at all. It just stays like this. Did you ever bother to try that ?

[Sekkha]

If it where due to over rotation you will easily be able to reproduce it. Just over rotate and see what happens..try it and report back if you dont mind

[DDowns]

That is the whole point, if you over rotate you are doing it wrong. Fly it correctly and you will not have problems.

[Sekkha]

The whole point is that when you over rotate you wont get the nose snap back to the ground. Therefore there must be something different causing it.

[skyteam78]

I found this video showing exactly what happened to me.

This is Matt Davies video: :https://www.youtube.com/watch?v=3NxnoPvySvs.
It happens around the 50 minute mark (50:05 to be precise) he begins his rotation and it slams back onto the runway.

I am sorry but it doesn't look like pilot error or over rotate.

[Ephedrin]

I found this video showing exactly what happened to me.

This is Matt Davies video: :https://www.youtube.com/watch?v=3NxnoPvySvs.
It happens around the 50 minute mark (50:05 to be precise) he begins his rotation and it slams back onto the runway.

I am sorry but it doesn't look like pilot error or over rotate.

great that you found it!

I've given up on this topic due to the massive headwind of ignorance and arrogance. PILOT ERROR! 5 degrees pitch angle, but TAIL STRIKE and PILOT ERROR!! reset pitch trim at this very moment too but PILOT ERROR! There are other people who know a thing or two about flying too..

I've explained it in a long post how I can reproduce it during the landing at almost 100% chance but hey.. who cares, I'm over-rotating or over-flaring etc. If the same person tells me over and over again it must become true some day. Don Quijote is getting tired. It's frustrating.


The video is from 2017 btw...

[Michael Codd]

Marc, as a Beta tester you should realise that it is inappropriate to compare a 2017 video with what may or may not be happening in PMDG's latest version of the same aircraft. Frustrating as these sort of issues are for any user, P3D - and PMDG's 2020 version of the B747-8 - are both significantly different to the files that existed in Matt Davies 2017 Youtube video. I am not experiencing this issue at all in the B747-8, but the fact that some users seem to be reporting similar issues with other third party addon aircraft as well leads me to believe it is more likely to be found and fixed within the simulator's own files and/or scenery configuration.

[Ephedrin]

Michael, as much as I agree that platforms and files change the issue I see is exactly the same now in P3Dv4.5HF3 as it was in the version Matt used in this video. It looks the same, it happens at the same time and I have been able to reproduce it for more than one version. Fact is: I don't strike my tail neither at takeoff nor at the landing. I'm experienced enough to judge that. My fault is that I have absolutely NO idea about coding. I understand maths quite well and I know how many things can influence an equation and also how many ways lead to the same result. You can find x in many ways. PMDG has chosen one way, maybe this way is buggy in P3D.

I have explained my way to easily reproduce it. I have not received any response from anyone if he was able to reproduce it that way or anything else. To me as a totally normal user regarding the airplane systems and flight model simulation it looks like this problem is being ignored. Robert said it was a tail strike - at 5 degrees, but okay.. - the airplanes' beta testers say it's a tail strike... Sry but I have no intention to fight agains wind mills. People explain it all the time, I guess there are minimum 5 threads about it with several people joining and everytime the same people immediately tell them it's a tail strike. Everytime the issue occures during takeoff the fun's gone. The stab trim resets to 4.5ish, a PMDG system and certainly not normal, and I can hardly get it off the ground on time before I reach the end of the runway, depending on the airport and weight. Usually I only hit Ctrl+C and Enter when this happens and do someting else. I'm done with it. It's been a problem for ages, since the 747 came out while I've never seen it in the 777, not even the -300 and I'm sure I have tail striked it a lot. So I highly doubt that this comes from P3D.

As I said, I'm not a program developer, I'm a tool technician. I can tell you everything about diamond cutting plates in aluminium but I don't know where to search for our issue and how to fix it. All I know is that I have only seen it in the PMDG 747-400 and -8 and the NGXU. While I have indeed seen the coast-problem mentioned by Dan in several aircraft. both are different issues and the thing in the video is (on my system) exclusive to PMDG.

[Sekkha]

Sorry to again chime in here, but this issue spoiled dozens of landings for me as well and it really makes me as frustrated as Marc seeing that the issue is not getting the attention it really deserves.

Therefore one general word about Beta testing because Michael mentioned that (and that is not against you Michael !):

What I would expect from a Beta tester is that he tries by all means to prove a theorie about an issue he might have. If some guys theory is that over rotating is causing this issue, why dont they try to reproduce this issue by just over rotate on takeoff and landing in different configurations and locations and see what happens. It is really an easy and quick setup. I was never able to reproduce it this way myself though. But there is enough evidence in this forum that the issue happens without the slightest bit of over rotation.

Therefore insisting in over rotation as the problem is falling into the trap of cognitive dissonance which a beta tester should never do.

best regards

[DDowns]

great that you found it!

I've given up on this topic due to the massive headwind of ignorance and arrogance. PILOT ERROR! 5 degrees pitch angle, but TAIL STRIKE and PILOT ERROR!! reset pitch trim at this very moment too but PILOT ERROR! There are other people who know a thing or two about flying too..

I've explained it in a long post how I can reproduce it during the landing at almost 100% chance but hey.. who cares, I'm over-rotating or over-flaring etc. If the same person tells me over and over again it must become true some day. Don Quijote is getting tired. It's frustrating.


The video is from 2017 btw...

This is landing... the topic is take off rotation. Not landing flare.
This has been known to be an issue with the QOTSII from it's first entry into market, and it can be reproduced at a variety of locations where there is a water/land boundary near the threshold, or a sudden change in surface elevation. I agree, this rapid descent during landing is not pilot error and I've read theories that it might be the length of the aircraft combined with the multiple contact points and P3D muffs it up.

Let's don't use the landing flare as an excuse for take off over rotation.

[Emi]

This is definitely not pilot error. It is a P3D issue with certain sceneries and mesh settings combined with very long aircraft. For instance the Aerosoft A330 or Captain Sim 767 suffer from it as well.

In most cases I could prevent it by setting the Mesh Terrain slider in P3D to 5m.
Higher settings cause this to happen on certain airports by certain developers on my system.

[Ephedrin]

This is landing... the topic is take off rotation. Not landing flare.
This has been known to be an issue with the QOTSII from it's first entry into market, and it can be reproduced at a variety of locations where there is a water/land boundary near the threshold, or a sudden change in surface elevation. I agree, this rapid descent during landing is not pilot error and I've read theories that it might be the length of the aircraft combined with the multiple contact points and P3D muffs it up.

Let's don't use the landing flare as an excuse for take off over rotation.

Dan,

It is EXACTLY the same. I land (500 miles from any shoreline or water), the nose starts to settle and THEN IT SLAMS down, EXACTLY as in this video. Not necessarily at 5 degrees, but WAY after the landing. I seldomly touch down with a pitch more than 6 or 7 degrees. It happens totally reproducably when I use the reverser axis on my throttle quadrant before the spolers have been fully deployed.. the lever is set to force the F1-key first and then deploys the reversers.

What you mean with the water boundaries IS indeed known but looks different. In that case it would "suck" the airplane out of the sky to the runway which would also be recognizable on ACARS programs like SmartCARS which measures a touchdown rate or -1500fpm or so. This is definitely something else. In the case we have here the main wheels are on the ground, the airplane has not yet taken off or the nose gear has not yet touched down. but beside from that it's a totally normal landing. And again, I can reproduce it whereever I want. In Denver if you wish.

with the nose slam comes a sudden reset of the stab trim to 4 or 4.5,. Both during takeoff and landing. That is certainly no coincidence and even more certain no pilot error. This is what I bluntly call a bug.

I have accustomed myself to rotate slower than taught and to touch down with some thrust left and only then idle the engines as I have never had this problem this way and when I do that I give the spoilers more time.

Emi

I could prevent it by setting the Mesh Terrain slider in P3D to 5m.
Higher settings cause this to happen on certain airports by certain developers on my system.

Higher settings: Do you mean a higher number or a "better" setting like 1m. 5m would be perfect for almost every scenery to be displayed correctly.

[Emi]

Correct, I mean that anything "sharper" than 5m can cause this. So 1m, 2m, etc. can cause this problem.

[Ephedrin]

It's certainly something to play with, I normally use 2m. But anything higher than 5m will cause several sceneries to display incorrectly.

[Ephedrin]

Dan, Robert and Michael,

I think I owe you an apology. I called the reactions on this issue arrogant and ignorant. Later on I had a conversation via PM with you, Michael, about that nose wheel issue and we were talking about control assignments and Michael wondered about my settings were I make my reverser axis send the F1 key via FSUIPC to force the 747‘s thrust levers to idle before applying reverse thrust with the same axis.

After that little conversation I dove into my settings and checked the FSUIPC.ini against what the FSUIPC user interface showed me against the different aircraft options I used over the last months and years.

Michael corrected me on a misunderstanding regarding the PMDG simulation of flight idle when I incorrectly assumed that the 747 would still apply thrust via the thrust levers like the older 777 or NGX do. I took the FSUIPC setup I „developed“ for my hardware for these older airplanes and used it in the 747.

what I found is that it‘s true that when I quickly apply reverser AXIS (Hardware) before the airplane actually recognized that it‘s on the ground the F1 signal was sent to the plane but didn‘t go when the reverser range was entered. I obviously don‘t know the PMDG code nor the FSUIPC code and I don‘t know what happened now but it seems the airplane received F1 (throttle cut) and my reverser axis commands at the same time.

I did about 30 landings and took off, turned around and landed again in P3D’s default Edwards on the long runway with different mesh settings. I found that 1 and 2 meters are definitely a problem for the 747 like Dan and Emanuel said. 5m and 10m caused it too as long as I used that FSUIPC command setting. Then I deleted this F1 and 5m mesh became totally fine and I was not able to reproduce this issue anymore.

I doubt that other people have that strange hardware settings and I have no idea what to tell them except don‘t use 1 and 2m meshes as you guys did.

my relation to the takeoffs and why I had the same issues on landings and takeoffs? Well, laugh at me: I had one of my four engine levers assigned to F4 at the very top to be able to firewall the throttles in the case of a wind sheer. Later I deleted that setting and placed a dead zone there to move my throttles to the forward hardstop so I could set the PMDG options to „override im ARM mode“. This has been deleted in the FSUIPC UI but not in the ini for some reason. So I assume it sent a mix of F4 and null zone against the planes TOGA mode. 🤷🏻♂️ FSUIPC my great love, lovely when treated well, a b***h if you forget the flowers once...

so the conclusion: 98% my fault, 1% FSUIPC and 1% PMDG for producing so complicated systems 😂

[Michael Codd]

I think you mean : 98% your fault, 1% FSUIPC and 1% Boeing for producing such complicated aircraft systems 😂 Glad to be of help, Marc.

[Ephedrin]

And we‘ve left LM out lol

[mats0916]

Glad you found a solution!