Airfoilsguy From , joined Dec 1969, posts, RR: Posted (7 years 3 months 3 weeks 5 days 9 hours ago) and read 5046 times:
I don't seem to recall seeing break rotors on the nose gear of most aircraft. If they don't have breaks on the nose gear, why not? Wouldn't that help reduce stopping distance. I know cars use the front wheels for a majority of their stopping power.
Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17 Reply 1, posted (7 years 3 months 3 weeks 5 days 9 hours ago) and read 5044 times:
The nose gear only takes about 10% of the aircraft's weight, so can't provide much braking force. There have been a few airliners with nosewheel brakes (some 727s had them). Generally they aren't seen as being worth the weight penalty.
I'd guess the front wheels of a car might be taking 60% or more of the weight of the car under heavy braking, which is why they provide most of the braking force.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
Airfoilsguy From , joined Dec 1969, posts, RR: Reply 2, posted (7 years 3 months 3 weeks 5 days 8 hours ago) and read 5042 times:
Quoting Jetlagged (Reply 1): I'd guess the front wheels of a car might be taking 60% or more of the weight of the car under heavy braking, which is why they provide most of the braking force.
My though was that once breaking action started the center of gravity shifts toward the front of the plane, thus putting a greater percentage of the aircrafts weight forward.
2H4 From United States of America, joined Oct 2004, 8950 posts, RR: 62 Reply 3, posted (7 years 3 months 3 weeks 5 days 8 hours ago) and read 5033 times:
HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58 Reply 5, posted (7 years 3 months 3 weeks 5 days ago) and read 4955 times:
Since the Main Gear brakes take most of the Aircraft Weight.It makes sense to have them Installed there.On the B727 there were NLG brakes.
Cannot locate a pic though.
If the purpose can be served by The Main Gear brakes alone,the Weight savings along with the Mechanical complications can be avoided.
Also the NLG Brakes were effective only after approx 60% of the Main Brake application as I was told.
LH4U From Germany, joined Jan 2006, 12 posts, RR: 0 Reply 6, posted (7 years 3 months 3 weeks 4 days 17 hours ago) and read 4882 times:
Quoting Airfoilsguy (Reply 2): My though was that once breaking action started the center of gravity shifts toward the front of the plane, thus putting a greater percentage of the aircrafts weight forward.
Center of gravity doesn´t move when braking.... it´s only dependent on weight ditribution. The main wheels are almost always behind CoG, so when main gear braking starts, there will be a momentum on the nose gear. That´s probably what you mean. But still, with this momentum nose gear braking would have relatively little effect...
2H4 From United States of America, joined Oct 2004, 8950 posts, RR: 62 Reply 7, posted (7 years 3 months 3 weeks 4 days 17 hours ago) and read 4879 times:
Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17 Reply 8, posted (7 years 3 months 3 weeks 4 days 17 hours ago) and read 4879 times:
Quoting Airfoilsguy (Reply 2): My though was that once breaking action started the center of gravity shifts toward the front of the plane, thus putting a greater percentage of the aircrafts weight forward.
Still its a very small percentage on a small contact area. The vast majority of the aircraft's weight stays on the main wheels, even under braking. Also, the nosewheel tyres have enough work to do with nosewheel steering.
Car tyres start with roughly 50/50 fore/aft weight split (maybe 55/45 allowing for the engine). Braking g loads further increase this imbalance. In an aircraft, to transfer significant weight forward onto the nosewheel would required dramatic deceleration rates, which might not go down too well with the self loading cargo.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
CosmicCruiser From United States of America, joined Feb 2005, 2211 posts, RR: 17 Reply 9, posted (7 years 3 months 3 weeks 4 days 16 hours ago) and read 4854 times:
Fedex had all the nose gear brakes removed on our 727s years ago.
Elvisisalive From United States of America, joined Aug 2005, 24 posts, RR: 0 Reply 10, posted (7 years 3 months 3 weeks 4 days 13 hours ago) and read 4803 times:
Am pretty sure all the wheels on the 747-400 nose or main are the 3-1479-2
so if the -400 does not have nose brakes is there just a cavity in the wheel were the brake would be ?
FredT From United Kingdom, joined Feb 2002, 2184 posts, RR: 26 Reply 11, posted (7 years 3 months 3 weeks 4 days 13 hours ago) and read 4795 times:
Quoting Jetlagged (Reply 1): Generally they aren't seen as being worth the weight penalty.
Not to mention maintenance!
Quoting Airfoilsguy (Reply 2): My though was that once breaking action started the center of gravity shifts toward the front of the plane, thus putting a greater percentage of the aircrafts weight forward.
The center of gravity stays put, but the weight distribution among the wheels is changed by the torque generated by the braking force.
The Saab Gripen has nose wheel braking. Makes for a lot of stopping power, combined with lift dumping, canards doubling as giant airbrakes and anti-lock brakes that can be applied prior to touchdown. Hardly an airliner though...
So, who will be first to estimate the force on the nose wheels of an airliner during braking?
Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
Matt72033 From United Kingdom, joined May 2005, 1617 posts, RR: 4 Reply 12, posted (7 years 3 months 3 weeks 4 days 13 hours ago) and read 4793 times:
Quoting Elvisisalive (Reply 10): Am pretty sure all the wheels on the 747-400 nose or main are the 3-1479-2
so if the -400 does not have nose brakes is there just a cavity in the wheel were the brake would be ?
Matt72033 From United Kingdom, joined May 2005, 1617 posts, RR: 4 Reply 15, posted (7 years 3 months 3 weeks 3 days 23 hours ago) and read 4682 times:
Quoting Matt72033 (Reply 12): Quoting Elvisisalive (Reply 10):
Am pretty sure all the wheels on the 747-400 nose or main are the 3-1479-2
so if the -400 does not have nose brakes is there just a cavity in the wheel were the brake would be ?
no brakes on the nosewheel of a 744
but your right, i checked, and the part numbers are interchangeable!
HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58 Reply 16, posted (7 years 3 months 3 weeks 3 days 19 hours ago) and read 4657 times:
Quoting Saintsman (Reply 14): There are brakes fitted to some aircraft to stop the wheels spinning after they have been retracted. They are applied directly to the tyres
They are referred to as Snubber pads.The above pic does not depict the total pads though,the Aft section is visable.Will post a better one when available later.
regds
MEL
Gunships From United States of America, joined Nov 2001, 574 posts, RR: 6 Reply 17, posted (7 years 3 months 3 weeks 3 days 8 hours ago) and read 4583 times:
Quoting Saintsman (Reply 14): There are brakes fitted to some aircraft to stop the wheels spinning after they have been retracted. They are applied directly to the tyres.
We used to call them "spin brakes" on the C-141. Just static brake pads installed near the top of the NLG wheel well that the NLG tires would contact as they retracted.
Eliminated the "gyro" effect of the tires spinning, which would add an unecessary force to an already heavily-stressed structure.
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