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kmanning

747-400 Turning Radius

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Hi all,If I'm correct, the PMDG is not modeled with a nosewheel steering tiller. When I try to make a 180 degree turn with the PMDG 747-400, it doesn't make the turn tight enough and the nosewheel goes off the pavement. I've seen 747s make 180 degree turns on the runway without going off the pavement. I'm thinking that it's because the PMDG is not modeled to use the tiller but only steers using the rudder pedals. In the real 747, the tiller can turn the nosewheel 70 degrees in either direction and overides the rudder pedal steering. With the rudder pedals, it only turns the nosewheel 7 degrees in either direction and does not activate the body gear steering. Since the PMDG is not modeled to use the tiller, could this be the reason why I cannot make this tight turn on the runway? Will PMDG model this feature soon? Ken.

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Ken,The 70 degree nose wheel is implemented on the rudder pedal steering. But the most likely reason you are seeing this is the poor ground friction handeling by FS.The dev team and the 747 pilots were scratching their heads to come up with a solution but seems like it will always be some sort of bad compromise until FS friction is modelled correctly.If you want to tinker with it yourself there's supposedly a tweaked sim1.dll out there which allegedly will give you better ground handling.Cheers,


Mats Johansson
PMDG Flight Test Dept
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| Asus Z270-A | Intel i5-7600K @ 4.8 GHz OC/H2O | nVidia Geforce GTX 1070 8GB OC/O2|

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Guest Ray51

lookes like about 70 degrees to meRay

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Hi Mats,Thanks for the informanion. Ray, you're correct. I've checked mines and it also appears to be at 70 degrees. So, it's like Mats said, the 70 degrees nose wheel steering is implemented on the rudder pedal. Is the boogie gear steering also modeled in the PMDG? It looks like it turns as well. I have that modified sim1.dll but it still doesn't seem to turn me tight enough. I'm going to look up in the chart and find the turning radius of a 747. I'm supposed to have that. Ken.

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Well, I am not sure if sim1.dll has anything to do it with it. It fixes only the longitudonal rolling friction coefficient. There is also a lateral friction coefficient which is apparently way too low in FS9 and to my knowledge no one ever attempted to fix it (few people around here are aware of its existance and importance) - regardless if sim1.dll encodes it or not. As a physicist I suspect that the turning radius may very well be affected by the lateral coefficient of friction - if it is too low your nose gear will be slipping on the ground and the turn radius will be larger. Just imagine there is no lateral friction (it is ZERO) - in such case no matter would you did with your nose gear you would be going straight. As a matter of fact you could probably get to some exterior view, get close to the front gear and tires and watch the interface between the tires and the ground, maybe you can even see them slip.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg


Michael J.

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Gents-If you do a search on steering, you'll find I've put up some pretty detailed posts on this topic in the past. Might help you understand why the airplane won't haul a 180 turn as you'd expect...This little "artifact" of MSFS behavior is unfortunate- and the larger/heavier the airplane- the worse it becomes.We have made our needs know to our friends up in Redmond....


Robert S. Randazzo coolcap.gif

PLEASE NOTE THAT PMDG HAS DEPARTED AVSIM

You can find us at:  http://forum.pmdg.com

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>If you want to tinker with it yourself there's supposedly a>tweaked sim1.dll out there which allegedly will give you>better ground handling.Could you please give me link for the updated sim1.dll?I wasn't able to find it on avsim and flightsim.


Regards,

Radek

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Are you guys using the correct Boeing method of doing a 180 turn on the runway? Its not nice in real life,as the cockpit ends up over the grass and it looks like you are going off the side!cheersJon

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how can a 747 make a 180degree turn on a runway ,sure the bird takes up most of the runway width as it is with the wing span. i would have thought the load shifted when turning would place the engines in danger of hitting objects or runway signs etc?PaulDublin, Ireland


Paul McMahon

Ireland

747400.jpg

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Guest Raptor

in mine,The nose wheel turns okay, but it doesn't move in turning.I mean the aircraft is turning (e.g. right) but if I switch to outside view the nose wheel still in 00 .. looks stupid while turing!

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Mats Johansson
PMDG Flight Test Dept
Boeing777_Banner_BetaTeam.jpg

| Asus Z270-A | Intel i5-7600K @ 4.8 GHz OC/H2O | nVidia Geforce GTX 1070 8GB OC/O2|

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Paul,You basically come off the centre line to one side then hard down on the tiller keeping the speed at abot 8-10kts,the airport signs should in theory be of a design that keeps them small low enough not to be a problem. There`s a set boeing procedure laid down which involves positioning so the side of the runway appears in the edge of the opposite windshield,this puts the outboard wing gear a couple of feet from the runway edge. The minimum runway width required is 153ft to complete a 180 turn!regardsJon

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>Paul,>You basically come off the centre line to one side then hard>down on the tiller keeping the speed at abot 8-10kts,the>airport signs should in theory be of a design that keeps them>small low enough not to be a problem. There`s a set boeing>procedure laid down which involves positioning so the side of>the runway appears in the edge of the opposite windshield,this>puts the outboard wing gear a couple of feet from the runway>edge. The minimum runway width required is 153ft to complete a>180 turn!>regards>Jonwow pretty amazing she can turn the full 180. id imagine you really gotta give some throttle to keep 8-10knots with the tiller pulled hard. i must see can i find some Boeing material on that procedure. ha i always learn something new about this aircraft. thanks again jon


Paul McMahon

Ireland

747400.jpg

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Paul,its contained in the boeing flight crew training manual( somewhere I think). we do them at Antigua and other Carib` destinations quite often,makes you sweat a bit untill you come out of the turn!!cheersJon

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If 153 ft is required for the turn then it seems only 200 ft runway would be sufficient, 150 ft wide runway would fall tad short. But then 200 ft wide runway would have plenty of spare room, unless perhaps those airports have runways that defy the typical 150/200 ft wide convention.EDIT: just checked and Antigua runway is 45 m wide which is exactly 150 ft.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg


Michael J.

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