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What determines multiple bogey landing gear tilt?
Been wondering for awhile, what determines the angle that rear tilted landing gear (such as the landing gear on the 777, A330 and 757) and front tilted landing gear (such as the landing gear on the 767 and A350-900), and why do some planes (such as the A350-1000) don’t have tilted landing gear?
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- SimProgrammer
- Posts: 217
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Re: What determines multiple bogey landing gear tilt?
When I worked at Airbus, the tilt was determined by the shape of the wheel bay.
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- BWIAirport
- Posts: 1602
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Re: What determines multiple bogey landing gear tilt?
SimProgrammer wrote:When I worked at Airbus, the tilt was determined by the shape of the wheel bay.
At least on the 777, the tilted gear is straightened before it is stowed in the wheel bay.
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- Starlionblue
- Posts: 21730
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Re: What determines multiple bogey landing gear tilt?
KPTKRampy wrote:Been wondering for awhile, what determines the angle that rear tilted landing gear (such as the landing gear on the 777, A330 and 757) and front tilted landing gear (such as the landing gear on the 767 and A350-900), and why do some planes (such as the A350-1000) don’t have tilted landing gear?
As mentioned, it's determined by the shape of the gear bay. An actuator tilts the gear into position when not in contact with the ground.
The A350-1000 does have "tilted" landing gear. There is a Bogie Pitch Trimmer Actuator just as on the -900. The angle is just different.
From the A350 FCOM:
"A bogie pitch trimmer actuator holds each MLG bogie in a correct pitch attitude when the gear is not in contact with the ground.
...
The hydraulic pressure in the pitch trimmer actuators is low. Therefore, when the aircraft is on the ground, the bogies are forced to the horizontal position by the weight of the aircraft."
Re: What determines multiple bogey landing gear tilt?
I think we have to differentiate here between bogie pitch trimmers, whose function is to position the bogie when off the ground, and active bogie positioning for retraction.
I remember a thread from quite a few years ago discussing the nose-down hang of the 767 bogies, and the consensus was that this was an example of 'passive bogie trimming' - the bogies hang like that when in the air so that they fit in the gear wells. However, quite a few airliners also actively reposition the bogie from its normal hang as part of the retraction cycle (777 as mentioned above, plus also from memory, the old VC-10 does this - so it's not a new thing).
I remember a thread from quite a few years ago discussing the nose-down hang of the 767 bogies, and the consensus was that this was an example of 'passive bogie trimming' - the bogies hang like that when in the air so that they fit in the gear wells. However, quite a few airliners also actively reposition the bogie from its normal hang as part of the retraction cycle (777 as mentioned above, plus also from memory, the old VC-10 does this - so it's not a new thing).
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- Starlionblue
- Posts: 21730
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Re: What determines multiple bogey landing gear tilt?
You want convoluted bogie positioning? Behold the Tu-144.and C-5.
https://youtu.be/E5f1XZaj-9g
https://youtu.be/vQHtskG4jjQ
https://youtu.be/E5f1XZaj-9g
https://youtu.be/vQHtskG4jjQ
Re: What determines multiple bogey landing gear tilt?
Would a nose-down or a nose-up hang impact the ability to grease a landing?
In this close-up of a QF A380, there are 2 distinctive impacts (albeit in a very short period of time) when the front wheels of the bogey touches down on the runway, followed very closely by the rear wheels (as it pivots on the centre of the bogey).
https://www.youtube.com/watch?v=nW30ghS8xqQ
In this close-up of a QF A380, there are 2 distinctive impacts (albeit in a very short period of time) when the front wheels of the bogey touches down on the runway, followed very closely by the rear wheels (as it pivots on the centre of the bogey).
https://www.youtube.com/watch?v=nW30ghS8xqQ
Re: What determines multiple bogey landing gear tilt?
889091 wrote:Would a nose-down or a nose-up hang impact the ability to grease a landing?
In this close-up of a QF A380, there are 2 distinctive impacts (albeit in a very short period of time) when the front wheels of the bogey touches down on the runway, followed very closely by the rear wheels (as it pivots on the centre of the bogey).
https://www.youtube.com/watch?v=nW30ghS8xqQ
I think some have mentioned that a rearward tilt like the 777 / A330 does allow for a smoother landing but this is not taken into account during design from what I understand.
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- RetiredWeasel
- Posts: 942
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Re: What determines multiple bogey landing gear tilt?
I can only speak for the 747 and you can't raise the gear handle unless the gear is tilted as it must be to fit in the wells. Additionally the tilt switches replace the 'squat' (wheels off the ground) switches on the struts of single bogie aircraft. Many systems are wired to these switches.
Re: What determines multiple bogey landing gear tilt?
889091 wrote:Would a nose-down or a nose-up hang impact the ability to grease a landing?
In this close-up of a QF A380, there are 2 distinctive impacts (albeit in a very short period of time) when the front wheels of the bogey touches down on the runway, followed very closely by the rear wheels (as it pivots on the centre of the bogey).
https://www.youtube.com/watch?v=nW30ghS8xqQ
The forward trailing tilt of the main landing gear on the 767 was very unforgiving on landing making for harder landings whereas the slight rearward tilt of the 757 gear was quite forgiving
Re: What determines multiple bogey landing gear tilt?
Max Q wrote:889091 wrote:Would a nose-down or a nose-up hang impact the ability to grease a landing?
In this close-up of a QF A380, there are 2 distinctive impacts (albeit in a very short period of time) when the front wheels of the bogey touches down on the runway, followed very closely by the rear wheels (as it pivots on the centre of the bogey).
https://www.youtube.com/watch?v=nW30ghS8xqQ
The forward trailing tilt of the main landing gear on the 767 was very unforgiving on landing making for harder landings whereas the slight rearward tilt of the 757 gear was quite forgiving
Is there any explanation to the effect?
I can see two possibilities, but both would be minor inputs from my perspective, especially if the bogey is more or less free to straighten on ground contact.
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- gregorygoodwin
- Posts: 148
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Re: What determines multiple bogey landing gear tilt?
I recall a MD10 that came into our hangar at IND for structures work because the bogie didn't center, or didn't center soon enough, when the main gear retracted. The main gear actuators apparently have the muscle to stow the gear even if it isn't centered for the wheel well. Spent about two days of around the clock structures work to get everything put in order.
Gregory
Gregory
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