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A330 Main Gear Bogey Tilt  
User currently offlinefaro From Egypt, joined Aug 2007, 1556 posts, RR: 0
Posted (3 years 1 month 1 week 5 days 18 hours ago) and read 6438 times:

The A330 main gear bogies exhibit a very marked backward tilt on extension. In neighbouring A.net threads, bogey tilt in general was explained as being necessary to facilitate the retraction of the bogies into the wheel wells or to soften landings.

On the A330 however, the wheel wells are parallel to the fuselage and there doesn't seem to be an appreciable softening of landings by the bogies on videos of A330 landings. Is it to provide a cautionary soft 'detent' against tailstrikes or for some other reason? The tilt does seem to be rather extreme and doesn't help the aircraft's drag in the landing configuration...

Faro

PS: Does automatic ground spoilers deployment activate with rear bogey or front bogey impact? This is not too clear on video shots.


The chalice not my son
17 replies: All unread, jump to last
 
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 1, posted (3 years 1 month 1 week 5 days 17 hours ago) and read 6404 times:

Maybe the weight bias around the axis at the bottom of the strut makes them tilt like that, meaning the designers wanted the rear axle to hit first.

Quoting faro (Thread starter):
The tilt does seem to be rather extreme and doesn't help the aircraft's drag in the landing configuration...

I think the extra drag is probably negligible in the context of the gear in general. Not to mention flaps and slats.

Quoting faro (Thread starter):
Does automatic ground spoilers deployment activate with rear bogey or front bogey impact? T

Pretty sure armed spoilers deploy when the strut for the main gear compresses. If one or both main struts I don't know.

The nose gear has no bogey. It's just a single axle unit with two wheels.

Quoting faro (Thread starter):
there doesn't seem to be an appreciable softening of landings by the bogies on videos of A330 landings.

You wouldn't be able to tell from a video.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently onlinemandala499 From Indonesia, joined Aug 2001, 6921 posts, RR: 76
Reply 2, posted (3 years 1 month 1 week 5 days 16 hours ago) and read 6388 times:

Quoting Starlionblue (Reply 1):
Pretty sure armed spoilers deploy when the strut for the main gear compresses. If one or both main struts I don't know.

Both Main Gear compressed and RA less than 6ft...
And...
If GNDSPLR is unarmed, at least 1 Thrust Lever in reverse and the other lever at idle (ie: if both in reverse, it would deploy)
or
If GNDSPLR is armed, both levers at idle or less.

If only 1 MLG compressed, and RA is less than 6ft and at least 1 Thrust Lever in reverse and the other lever at idle or lower, it would partially deploy as long as this condition remain valid.

Mandala499



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlinemy235 From United States of America, joined Mar 2009, 92 posts, RR: 0
Reply 3, posted (3 years 1 month 1 week 5 days 9 hours ago) and read 6211 times:

IMHO A330's have the softest landing of any airliner due to the added length of the landing gear. The 747 also has about the same angle of tilt on two of it's four rear bogies. I think the design was to have the gear contact the runway with the aircraft still at the top of ground effect.

User currently offlineN243NW From United States of America, joined Jul 2003, 1638 posts, RR: 20
Reply 4, posted (3 years 1 month 1 week 5 days 8 hours ago) and read 6180 times:

One of the interesting things is the noticeable pitch forward that the pilots command (or the aircraft exhibits) after the rear axle hits on the A330 and A340. Can someone shed some light on this? Is it a technique to help get the whole truck on the ground and the spoilers out or is it a phenomenon that simply results from the geometry of the gear?

Also, to those who fly (or fly on) the 330: I would make the assumption that the part of the landing that is "felt" the most is the front axles coming down...am I correct? It seems that the rear axles would create a light shudder inside the cabin and the main thump would come from the rest of the truck hitting the ground.



B-52s don't take off. They scare the ground away.
User currently offlinemy235 From United States of America, joined Mar 2009, 92 posts, RR: 0
Reply 5, posted (3 years 1 month 1 week 5 days 2 hours ago) and read 6103 times:

Quoting N243NW (Reply 4):
It seems that the rear axles would create a light shudder inside the cabin and the main thump would come from the rest of the truck hitting the ground.

You are so right. I've flown on A333/343 a number of times. Almost every landing was how you described. Smooth as silk.

http://youtu.be/lowrM-780tg


User currently offlineimiakhtar From , joined Dec 1969, posts, RR:
Reply 6, posted (3 years 1 month 1 week 4 days 13 hours ago) and read 5945 times:

Quoting N243NW (Reply 4):
One of the interesting things is the noticeable pitch forward that the pilots command (or the aircraft exhibits) after the rear axle hits on the A330 and A340. Can someone shed some light on this? Is it a technique to help get the whole truck on the ground and the spoilers out or is it a phenomenon that simply results from the geometry of the gear?

Not sure about the A340 but the recommended technique on the A330 is to ease off on the back pressure and relax the side-stick towards the neutral position when you feel the rear wheels touchdown and let the aircraft de-rotate naturally. Once the whole main gear is down you "fly" the nose down - otherwise you risk a hard nose gear touchdown like the Royal Air Maroc 767 at JFK a few years ago. The whole idea is to get weight on wheels and maximise the braking effort.

Quoting my235 (Reply 5):
Smooth as silk.

http://youtu.be/lowrM-780tg

That wasn't very smooth on the nose gear!


User currently offlineshufflemoomin From Denmark, joined Jun 2010, 480 posts, RR: 2
Reply 7, posted (3 years 1 month 1 week 4 days 13 hours ago) and read 5933 times:

Quoting my235 (Reply 3):
IMHO A330's have the softest landing of any airliner due to the added length of the landing gear

When my SAS A330 landed in EWR in January it was the hardest landing I've ever felt followed by the hardest braking I've experienced too. My iPad bounced of the seat and thanks to the braking ended up about 2 or 3 rows in front. I guess it all really comes down to the guys up front.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 8, posted (3 years 1 month 1 week 4 days 12 hours ago) and read 5909 times:

Quoting shufflemoomin (Reply 7):

When my SAS A330 landed in EWR in January it was the hardest landing I've ever felt followed by the hardest braking I've experienced too. My iPad bounced of the seat and thanks to the braking ended up about 2 or 3 rows in front. I guess it all really comes down to the guys up front.

You can't draw any conclusions from one landing. Any number of special circumstances that the guys in front had no control over may have been in effect.

Note also that pilots are not paid to perform smooth landings. They are paid to perform safe landings.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineN243NW From United States of America, joined Jul 2003, 1638 posts, RR: 20
Reply 9, posted (3 years 1 month 1 week 4 days 10 hours ago) and read 5873 times:

Quoting imiakhtar (Reply 6):
That wasn't very smooth on the nose gear!

At that point the PF was starting to realize that his "smooth as silk" touchdown had used up 3-4k feet of runway and he better get the nose down and start slowing  



B-52s don't take off. They scare the ground away.
User currently offlineMax Q From United States of America, joined May 2001, 4657 posts, RR: 19
Reply 10, posted (3 years 1 month 1 week 3 days 22 hours ago) and read 5713 times:

Quoting N243NW (Reply 9):

At that point the PF was starting to realize that his "smooth as silk" touchdown had used up 3-4k feet of runway and he better get the nose down and start slowing

No, when the nose gear finally touched down, he had completely run out of elevator authority, if you look closely you will see it is deflected fully up.



In other words, it was coming down no matter what the Pilot did !



The best contribution to safety is a competent Pilot.
User currently offlineN243NW From United States of America, joined Jul 2003, 1638 posts, RR: 20
Reply 11, posted (3 years 1 month 1 week 3 days 22 hours ago) and read 5705 times:

Quoting Max Q (Reply 10):
No, when the nose gear finally touched down, he had completely run out of elevator authority, if you look closely you will see it is deflected fully up.

Ahh, so I see the crew was practicing their soft field technique then!  



B-52s don't take off. They scare the ground away.
User currently offlineMax Q From United States of America, joined May 2001, 4657 posts, RR: 19
Reply 12, posted (3 years 1 month 1 week 3 days 22 hours ago) and read 5696 times:

Quoting N243NW (Reply 11):

Ahh, so I see the crew was practicing their soft field technique then

Not something to practice in a widebody Jet Transport.



The best contribution to safety is a competent Pilot.
User currently offlineN243NW From United States of America, joined Jul 2003, 1638 posts, RR: 20
Reply 13, posted (3 years 1 month 1 week 2 days 10 hours ago) and read 5476 times:

Quoting Max Q (Reply 12):
Not something to practice in a widebody Jet Transport.

The reason why I added the smiley...



B-52s don't take off. They scare the ground away.
User currently offlinehal9213 From Germany, joined May 2009, 302 posts, RR: 0
Reply 14, posted (3 years 1 month 1 week 15 hours ago) and read 5285 times:

Quoting my235 (Reply 3):
IMHO A330's have the softest landing of any airliner due to the added length of the landing gear.

Weird, I always get bumpy touchdowns on my trips. But this definately mostly depends on a whole lot of other factors.
I love the 777 landings, on some smooth ones, you can actually feel the triple-bogey, like thumb-thumb-thumb followed by the springy strut compression.


User currently offlineAirbus_A340 From Hong Kong, joined Mar 2000, 1560 posts, RR: 19
Reply 15, posted (3 years 1 month 6 days 20 hours ago) and read 5194 times:

As most posters above have observed and posted, you can experience a smooth touchdown on the rear-bogies but then it is very unforgiving when the rest of the bogie comes into contact with the ground.

Deceleration of the aircraft increases the hardness of the landing as the aircraft slows and "falls" onto the rest of the bogie. As imiakhtar has said, the recommended technique is to neutralise the controls for derotation. Having said that, there are some "tricks" to soften the second touchdown. After rear bogie touchdown inputting forward sidestick input to assist the derotation. A second "trick" is to delay pulling thrust reversers, again delaying the deceleration. Having said that, i stress that this is not a recommended technique, though you will find many people on the line utilising these techniques on non-field length limited runways to smoothen the landings. The techniques I described may be noticed in some videos that can be found on yourtube.

hope that helps



People. They make an airline. www.cathaypacific.com
User currently offlinemy235 From United States of America, joined Mar 2009, 92 posts, RR: 0
Reply 16, posted (3 years 3 weeks 5 days 3 hours ago) and read 4694 times:

Quoting hal9213 (Reply 14):
I love the 777 landings, on some smooth ones, you can actually feel the triple-bogey, like thumb-thumb-thumb followed by the springy strut compression.

A+  


User currently offlineFlyingCello From United Kingdom, joined Jul 2010, 159 posts, RR: 0
Reply 17, posted (3 years 2 weeks 3 days 9 hours ago) and read 4199 times:

The A330 is well known for having a low wing loading...at low weights, descent planning is supposed to be key, as the beast just doesn't want to descend! Is this one possible reason why the landings are 'soft'?

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