Nose Wheel Brakes
short flights long nights
Thread Starter
Nose Wheel Brakes
I was just talking to my sister on the phone from Oz, who was telling me that (wrongly reported of course) a QF 74 had a "Nose Wheel Brake Fire". I then exlained to her that this was impossibe, because aircraft do not have nose wheel brakes. Her question was "OH Why not". And I could not answer, because I dont know, I mean ..well..they just dont....!!!!
So, please, can some of you in this forum, who know a lot more than me, explain why we dont have nose wheel brakes?
Thanks in advance.
So, please, can some of you in this forum, who know a lot more than me, explain why we dont have nose wheel brakes?
Thanks in advance.
SOPS
I can't speak about modern aircraft but the older ones that I have worked on did have nose wheel brakes. These were referred to as "spin brakes" and were friction pads fixed in the nose wheel bay. When the undercarriage was retracted the nose wheels contacted the friction pads and were "braked" to a stop. This prevented "nose wheel rumble" when the nose gear is retracted. The main gear is braked by an autobrake for the same reason. I have never heard of nose wheel spin brakes catching fire though!!
Hope this is of some help.
CC
I can't speak about modern aircraft but the older ones that I have worked on did have nose wheel brakes. These were referred to as "spin brakes" and were friction pads fixed in the nose wheel bay. When the undercarriage was retracted the nose wheels contacted the friction pads and were "braked" to a stop. This prevented "nose wheel rumble" when the nose gear is retracted. The main gear is braked by an autobrake for the same reason. I have never heard of nose wheel spin brakes catching fire though!!
Hope this is of some help.
CC
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Have to agree with MaximumPete regards nosewheel brakes fitted to B727 (200).Inflight brakes for the nose wheels are basically pads attached to either a spring loaded rod or a curved plate of stainless steel.(BTW dont go sniffing it).
cheers
cheers
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The only aircraft that I have come across with Nose Gear brakes is,as was already stated,the 727. [only worked Boeing in the main tho]
Compasscall,the spin brakes for the nose wheels are not just restricted to older aircraft.The 737NG,like all the 73's, have them.
Compasscall,the spin brakes for the nose wheels are not just restricted to older aircraft.The 737NG,like all the 73's, have them.
FWIW, on 747's they use the same wheel assembly for the nose wheels as the main wheels. Saves on the cost of getting tyres & so on.
As mentioned above, the only brakes they have for the nose wheel are a pair of sprung metal gadgets that slow the wheels after they've been tucked up into the bay.
As mentioned above, the only brakes they have for the nose wheel are a pair of sprung metal gadgets that slow the wheels after they've been tucked up into the bay.
The Reverend
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The Convair 880 and 990 had anti skid nosewheel brakes. Inflight braking of nosewheels was accomplished during retraction by diverting the return from the extend side of the NLG actuating cylinder to brake return at the brake metering valve. Pressure was restricted to 200 - 400 PSI.
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What's up with aviation reporting in Dunnunda? Recall the article about the Quantas flight (767?) which had to return after a fan belt broke?
(It was the fan which went to pieces, of course)
Cheers,
Fred
(It was the fan which went to pieces, of course)
Cheers,
Fred
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As well as the Convairs the 727 was available with full nose wheel braking. Remember that it's unique selling point originally was as the first 'stol' jet opening up fields that had never had turbo-jet operations prior to its development.
In practice, however, the brakes were got rid of when companies' gained enough experience in the field to get a feel for the cost/ benefit effects.
Regards
Rob
In practice, however, the brakes were got rid of when companies' gained enough experience in the field to get a feel for the cost/ benefit effects.
Regards
Rob
Last edited by PPRuNe Towers; 3rd Jul 2003 at 21:52.
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Some 146 pilots 9and others) ask you the "Nose Wheel Break status" (wordered differntly on the pilots) when you are doing a start up with the headset so they must have them
Do a Hover - it avoids G
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The only nose wheel brake that I am familiar with was on G-APUX Hawker's original Hunter two seat demonstration aircraft. It was very effective, in the way that the front brake on your bike is better than the rear one. As you brake the nose (aircraft or bike) dips and forces the braked wheel even harder onto the ground improving retardation. In the Hunter the measured reduction in landing run due to the nose brake was (by chance) the same as streaming the brake chute.
The downside is weight (a long way forward) cost, maintenance and most of all sorting out the leg and its mounting structure to carry the enormous drag loads that are trying to snap the leg backwards. The brake chute had the advantage that it was lighter overall and worked on runways covered in water, snow and ice.
The downside is weight (a long way forward) cost, maintenance and most of all sorting out the leg and its mounting structure to carry the enormous drag loads that are trying to snap the leg backwards. The brake chute had the advantage that it was lighter overall and worked on runways covered in water, snow and ice.
short flights long nights
Thread Starter
Thanks all for response, but I know the nose wheel has a "brake" when it retracts into the well, what I was asking is why dont they have disk brakes used for stopping. And the 727s I flew did not have nose wheel brakes. I await your reply
Regards SOPS
Regards SOPS
I've been asked to arrange approval of a few nosewheel brake mods on various light types, and they are invariably a pain in the neck.
(1) The main aircraft structure is seldom designed to take what in effect are compressive loads towards the middle of the aeroplane.
(2) If used at speed (landing or aborted t/o) a nosewheel brake alone tends to destabilise the aircraft and it can try to skew off the side of the runway.
(3) Mains already have a very substantial structure that doesn't struggle to take braking loads, this is not necessarily true of noselegs which are much lighter affairs.
(4) You can't achieve differential braking with a nosewheel brake!
(5) Trying to put significant braking effort through one or two smallish tyres (the usual on nosewheels) leads to very short tyre life.
So it's possible, but in general terms a daft idea best avoided.
G
(1) The main aircraft structure is seldom designed to take what in effect are compressive loads towards the middle of the aeroplane.
(2) If used at speed (landing or aborted t/o) a nosewheel brake alone tends to destabilise the aircraft and it can try to skew off the side of the runway.
(3) Mains already have a very substantial structure that doesn't struggle to take braking loads, this is not necessarily true of noselegs which are much lighter affairs.
(4) You can't achieve differential braking with a nosewheel brake!
(5) Trying to put significant braking effort through one or two smallish tyres (the usual on nosewheels) leads to very short tyre life.
So it's possible, but in general terms a daft idea best avoided.
G
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SOPS ...it was a factory option. Customers could choose. Likewise, B720s could be ordered with brake cooling fans.
For similar reasons, have you ever seen an A320 with four wheel boggies instead of the usual duals?
For similar reasons, have you ever seen an A320 with four wheel boggies instead of the usual duals?
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wing_nut1
This has to be a wind up so I'll gratefully bite.If the 146 had nose wheel brakes wouldn't it want to spear off to the right every time they were applied ??BTW for the uninformed the nose gear isn't in the centre of the a/c,its offset which is why when steering is used itis "easier"one way !!
Cheers
This has to be a wind up so I'll gratefully bite.If the 146 had nose wheel brakes wouldn't it want to spear off to the right every time they were applied ??BTW for the uninformed the nose gear isn't in the centre of the a/c,its offset which is why when steering is used itis "easier"one way !!
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Glue Ball try Indian Airlines????
Also Concorde has a disk brake on the nose wheel live axle for spin down braking prior to retraction.
Regarding the issue of QF B744 Brakes, (another thread) .
A colleague saw a brake fire on one of these on arrival due to the carbon dust catching fire and some surplus grease on the axle...he extinguished it in a few sconds. However it does hi lite the issue of who meets and greets the aircraft? Now usually some one on the minimum wage looking to go home early and not an engineer trained on the aircraft....so you get what you pay for!!
Also Concorde has a disk brake on the nose wheel live axle for spin down braking prior to retraction.
Regarding the issue of QF B744 Brakes, (another thread) .
A colleague saw a brake fire on one of these on arrival due to the carbon dust catching fire and some surplus grease on the axle...he extinguished it in a few sconds. However it does hi lite the issue of who meets and greets the aircraft? Now usually some one on the minimum wage looking to go home early and not an engineer trained on the aircraft....so you get what you pay for!!
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Dittos to what PPRuNe Towers said--
The nose brake on the initial 727 was history after the airlines found they were comfortable with operating the aircraft on short fields. The recurring cost of maintenenace was not worth the benefit.
The wheel stop devices used during retraction are called "snubbers" (never to be confused with "chubbers" another very import series of parts no aircraft should fly without).
PT
The nose brake on the initial 727 was history after the airlines found they were comfortable with operating the aircraft on short fields. The recurring cost of maintenenace was not worth the benefit.
The wheel stop devices used during retraction are called "snubbers" (never to be confused with "chubbers" another very import series of parts no aircraft should fly without).
PT
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SAAB's JAS39 Gripen uses nosewheel brakes, along with extreme nose-down canard position to increase nose gear reaction loads. Consequently the nose gear looks pretty beefy for such a small airframe. With relatively demanding STOL requirements the penalty was considered worth paying.
I'll add a (6) to Genghis' list of negatives:
(6) reduced nosewheel steering effectiveness - the more braking is employed, the less sideforce the tyres can generate.
from this article:
(Although not mentioned, I'm sure mainwheel brakes figure in the mix too)
I'll add a (6) to Genghis' list of negatives:
(6) reduced nosewheel steering effectiveness - the more braking is employed, the less sideforce the tyres can generate.
from this article:
The Gripen automatic landing mode triggers at nose wheel ground contact, and provide large deflections of canard, elevon and air-brakes and also application of a nose-wheel brake, as deceleration means.
