What Happens When You Slam On the Brakes in a 747?

[Pedro_The_Swift]

Emergency testing a Boeing's brakes equals awesome — Autoblog (http://www.autoblog.com/2011/05/11/emergency-testing-a-boeings-brakes-equals-awesome/)

[WhiteD3]

What Happens When You Slam On the Brakes in a 747? | Wired Science| Wired.com (http://www.wired.com/wiredscience/2011/05/what-happens-when-you-slam-on-the-brakes-in-a-747/)

Not much, thankfully

[stig0000]

200m, from 200mph,, crazy,,, dose anyone no if planes have some sort of ABS????

[JDNSW]

200m, from 200mph,, crazy,,, dose anyone no if planes have some sort of ABS????

Yes. Not all planes, of course, but ABS was invented for aeroplanes.

I am reminded of the time many years ago I flew into Wellington (NZ) in a 747SP - if you know that airport, it looks too short to land even an SP. The landing was apparently made with the brakes on, with ABS switched on, and full throttle reverse thrust as soon as the wheels were on the ground. I was in Business Class on the upper deck, and the poorly stowed coffee pot (fortunately empty) sailed down the aisle to land at the pilot's door.

John

[Pedro_The_Swift]

These sort of stories fascinate me John,,

so do the engineers that say yes you can land one of these things on that runway make the same sort of safety calculations as they do for fuel?

[Pedro_The_Swift]

I think I've been Modded!
was sure I posted this in The Parking Lot,,
:Rolling:

[RR P38]

That was 200m less than expected, i didnt hear a final distance covered.

Yes aircraft have had ABS systems for a long time.
I am pretty sure disc brakes were first developed for aircraft then applied to road vehicles.

[JDNSW]

These sort of stories fascinate me John,,

so do the engineers that say yes you can land one of these things on that runway make the same sort of safety calculations as they do for fuel?

Yes, although the margins are closer than fuel, because fuel has to cover unexpected delays. Every aircraft, even the smallest has performance charts (or computer programs) that you plug in wind speed, temperature, altitude, slope, runway surface, landing mass etc, and if the answer in landing distance is less than the runway length, the landing can be undertaken. Also coming out of the calculation is the approach speed, and the flight manual and operator policies also dictate the approach angle, flap settings, procedures such as rate of brake and reverse thrust application etc. Similar calculations apply for takeoff, and on occasion weight (usually freight or baggage, but occasionally passengers) have to be offloaded to reduce the required distance to the available distance. The pilot actually has very little discretion in airline operations, more in light aircraft operations, where most runways are far longer than needed.

John

[p38arover]

I think I've been Modded!
was sure I posted this in The Parking Lot,,
:Rolling:

You were and yes it was.

[rick130]

I think I've been Modded!
was sure I posted this in The Parking Lot,,
:Rolling:

Now that is funny :lol2:

[stallie]

It's not always a case of jumping on the brakes like in a car and hoping the ABS does its bit...

I'd have to check the manual in my bookcase for the Boeing 747, but for the Airbus, the pilots have a choice of three modes for auto braking, LO MED and MAX.

MAX is armed for all takeoffs and used for aborted takeoffs and will activate above 72 knots - it provides the maximum stopping rate in the minimum distance and is extremely violent for the uninitiated.

LO and MED are pilot choices for landing and these command a deceleration rate of 2m/s^2 in Lo and 3m/s^2 in MED and modulate the amount of braking accordingly. I regularly land on a solid ice runway and the ABS can be heard clicking in and out and some days the light indicating LO or MED flicks off if the commanded deceleration is not being met.

On long runways, however it's common to land with no autobrake and coast to the end, sometimes with no reverse at all - especially if there's noone behind you. Saves brake wear and engine wear, but more importantly on tight turn around it keeps the brake temperatures down for a quick tunraround. They can take a long time to cool - and 300°C is the maximum brake temp for takeoff...

I can write a whole pile of stuff on how the certification and calculations of braking, takeoff speeds and performance work if anyone's interested...

[jb747]

It's not always a case of jumping on the brakes like in a car and hoping the ABS does its bit...

I'd have to check the manual in my bookcase for the Boeing 747, but for the Airbus, the pilots have a choice of three modes for auto braking, LO MED and MAX.
They are the settings on the 'classic' 747. If I remember correctly (it looks as if I've deleted the manual I had), the settings on the 747-4 were 1 through 4, then max. None of them actually give max braking, there's only one setting that does that...RTO...rejected take off.


MAX is armed for all takeoffs and used for aborted takeoffs and will activate above 72 knots - it provides the maximum stopping rate in the minimum distance and is extremely violent for the uninitiated.RTO is armed for takeoffs, not MAX. The 72 knots is an Airbus thing. Below that speed the spoilers don't automatically extend in an abort, and it's the spoiler activation that trips the autobrake to RTO. Manual selection of the spoilers will cause RTO to activate down to 40 knots (and when active it stays engaged until the aircraft stops, or it's turned off).


LO and MED are pilot choices for landing and these command a deceleration rate of 2m/s^2 in Lo and 3m/s^2 in MED and modulate the amount of braking accordingly. I regularly land on a solid ice runway and the ABS can be heard clicking in and out and some days the light indicating LO or MED flicks off if the commanded deceleration is not being met.There is no indication on any aircraft that I have flown (747-2/3,767-2/3, 747-4, or A380) of ABS activating. You can't feel it, nor is there any clicking.


On long runways, however it's common to land with no autobrake and coast to the end, sometimes with no reverse at all - especially if there's noone behind you. Saves brake wear and engine wear, but more importantly on tight turn around it keeps the brake temperatures down for a quick tunraround. They can take a long time to cool - and 300°C is the maximum brake temp for takeoff...Company policy will control this. I would consider it foolish to land with no autobrake selected, though it may well be disconnected shortly after touchdown. Idle reverse should be used in all cases, simply to eliminate the residual forward thrust of the engines. A large engine at idle forward thrust is still producing thousands of pounds of push. For what it's worth though, reverse thrust does very little actual braking. Only about 4000 lbs of reverse thrust will be available from an engine that may well produce 60,000 lbs forward. Biggest benefit of reverse is that it blasts any water off the runway...and so allow the brakes to do their job.

[stallie]

Thanks for the clarifying the Boeing side of things, my comments related to aircraft from the other side of the Atlantic, however the principle still achieves the same goal, no matter what TLA the competing manufacturers use. :)

Re the speeds, doesn't the B744 have a similar speed (85kts) below which the RTO autobraking will not normally activate?


There is no indication on any aircraft that I have flown (747-2/3,767-2/3, 747-4, or A380) of ABS activating. You can't feel it, nor is there any clicking.

I've never heard it on a paved runway wet or dry, only on solid ice or snowcapped ice runways, and not every time. It depends on the friction on the day (and sometimes that varies by the hour).

As for landing no autobrake selected, naturally it depends on the runway aircraft and payload. I do it frequently given the routes, payloads (or lack thereof) and usual parking positions we use. Horses for courses.

[jb747]

Actually, my comments were a mix of Airbus and Boeing. I've mostly flown B, but currently fly ze French.


Re the speeds, doesn't the B744 have a similar speed (85kts) below which the RTO autobraking will not normally activate?Probably. I can't remember, and my manuals haven't survived the move to new computers. I'll have to track some new discs down next time I go to work..if only for sentiment's sake.



I've never heard it on a paved runway wet or dry, only on solid ice or snowcapped ice runways, and not every time. It depends on the friction on the day (and sometimes that varies by the hour).Where are you flying that you land on that stuff frequently? Anyway, you won't hear anything in any of the big jets I mentioned, even on icy runways.


As for landing no autobrake selected, naturally it depends on the runway aircraft and payload. I do it frequently given the routes, payloads (or lack thereof) and usual parking positions we use. Horses for courses.And probably affected by aircraft size. In any event, banned in my company.

[stallie]

Where are you flying that you land on that stuff frequently?


YWKS and NZPG in your current steed's second smallest sibling.:D

[jb747]

YWKS and NZPG in your current steed's second smallest sibling.:D

Jesus...that's way too far from anywhere with only two engines. I'd don't like it down there with four....but then I've been known to need a rat hole in a hurry.

How is the runway marked?

[stallie]

That's way too far from anywhere with only two engines
You don't want to hear about the 12 hour ferry flight of our skiplanes there then :D For the 'bus though, it's 180 minute EDTO operation.


How is the runway marked?
With black flags. There is an non compliance raised against part 139 for not having numbers and white lines down the runway :)

[jb747]

You don't want to hear about the 12 hour ferry flight of our skiplanes there then :D For the 'bus though, it's 180 minute EDTO operation.
So I guess you're waiting with baited breath to hear whatever happened to AF447?



With black flags. There is an non compliance raised against part 139 for not having numbers and white lines down the runway :)
Oh, I'm sure they're there. Just used white paint....

[muddymech]

As a further development airbus now allow the pilots to select the exit point off the runway so that the brakes regulate the braking for the exit point.

[stallie]

It's called "Brake to Vacate"

From what I read in the glossy monthly mags from Airbus, it's an option on the A380 and will be standard on the A350. No word on other aircraft types for retrofitting.

Its a great idea as it will save fuel and time for both your aircraft and those following as they don't have to wait for you to get off the runway.


So I guess you're waiting with baited breath to hear whatever happened to AF447?


Yes, along with everyone else I guess. It will be very interesting; it's great news that it's readable.

[VladTepes]

http://www.boeing.com/Features/2011/05/bca_747-8_RTO_05_04_11.html'sms_ss=email&at_xt=4dc2ab81c042aa99%2C1 (http://www.boeing.com/Features/2011/05/bca_747-8_RTO_05_04_11.html'sms_ss=email&at_xt=4dc2ab81c042aa99%2C1)

Impressive



Those 747-8's are way more good lookin' than the A380 !

[Pedro_The_Swift]

try and keep up Vlad,,,:p

[dhc4ever]

200m, from 200mph,, crazy,,, dose anyone no if planes have some sort of ABS????


Those markers are 1,000's of feet not 100m. Its still bloody impressive though, I wonder if your bum biting the seat makes a difference:eek:

Yes they have an anti lock brake system.
They guys above who drive them have pretty well covered it.

[Plane Fixer]

Not all aircraft have ABS.
I wish that the Twotters and B1900D I was looking after in a West African country had, as we were constantly changing wheels due flat spots or worn completely through.
I have on a couple of occasions seen the wheel on a Twin Otter nearly ground down to the axle. That was due to poor pilot training as they used to land with size 10 on top of the pedals.
I have a good selection of photos of various problems I encountered there.
Ironical it may seem is that I am writing this from an old iron ore mine in the south of the same country I declared I will not work in again. This time it is looking after an Australian aircraft here on a job and I am out in a couple of days and I cannot wait.

[C00P]

Fascinating stuff chaps! Sounds like you need a license and 6 weeks study just to learn how to use the brakes, there are so many options/ possibilities.
In my 1946 AusterJ1 we don't have brakes- we have "influencers" that slightly retard motion and influence direction. And you work them with your heels...
But then, we've only got 2000 lbs Max to stop.... from about 50kph.
First post on here- pleased to see some other pilots about. And, of course, I operate another British device designed to spread oil around the countryside- a Series III Landrover. (The Auster is powered by a Gypsy Major, so it spreads more oil in a fine spray over a much larger area).
And then, if we want comfort- of a sort- we have out Morris 1100 which contributes its own portion of oil to our carbon footprints.
If it's British and leaks oil, we own it...
Regards

Coop

[stallie]

That was due to poor pilot training as they used to land with size 10 on top of the pedals.
Bloody hell. Not good at all.
I once had a student put the handbrake on in flight that I didn't see, made all the worse when we touched down he heard the screech and locked his toes on the brakes. I got my left hand under his knees, pulled them up and disengaged the handbrake in enough time not to leave a flatspot on the tyres...

[VladTepes]

Surely the minute you hit the ground with wheels not able to spin the tyres would flat-spot ?

[dhc4ever]

Surely the minute you hit the ground with wheels not able to spin the tyres would flat-spot ?

Yes you would get a flat spot, the really talented drivers could blow all tyres, the merely inept would just flat spot them. Sometimes the tyres would still be within limits after this abuse, but not usually.

We had a case of a Caribou taking off with the hand brake ON in East Timor, the reason he didnt notice it was on was because it was a dirt strip (strip being a very loose description, paddock would be closer) very muddy, the aircraft was sinking, and it took full power and full flap to get going. He found the handbrake on during the pre landing check list. Looking at the high water/mud line and he had mud to the top of the tail which is 38 ft high, I reckon he cleared the prop tips by about 10 cm.
Now dont get me started on the female pilot who managed to blow all 4 main tyres twice in 1 week, she obviously had issues with the prelanding check list.
For some reason my kind offer for her to help out in wheel bay fixing her handy work fell on deaf ears.:wasntme:

[85 county]

In my 1946 AusterJ1 we don't have brakes- we have "influencers" that slightly retard motion and influence direction. And you work them with your heels...


Coop
HA love it
but i know what you mean. DH89 throtels on the left, differential brake on the right, feet on the peddles, taxing you always felt you were short 1 arm and a hand. not that they had that much of an influence any way. a wee bit of swing on take off. nope try again. and again and again.
tiger moths, people think these must be easy to fly, nope top heavy and wobble yet so easy to do a woffle fobber.

[stallie]

I did a very good look at the main tyres after landing and we obviously hadn't travelled far enough to flatspot them. Some slight scuffing / wear was just detectable if you were looking for it (someone else had trouble finding it), but nothing you would say was a classic flatspot.

As for taking off with the park brake on, a similar problem can happen when taxying on slushy snow on ice runways. The slush gets into the brakes, melts and refreezes... Then when taxying, the wheel just slides over the ice, causing a surprising buildup of heat The end result is actually an ice burn into the rubber, rather than a flatspot, and you have no way of knowing in the cockpit.

And dhc4ever, your steeds aren't the biggest to achieve this park brake feat. An A320 did it..... http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20100827X20401&key=1

[85 county]

And dhc4ever, your steeds aren't the biggest to achieve this park brake feat. An A320 did it..... WPR10IA430 (http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20100827X20401&key=1)

aaahhh so a new airbus is just like my 84 Isuzu county, no light for the hand brake.

[stallie]

There is meant to be an aural chime and caution light if the park brake is selected in flight.

The final report is not out yet, so i shall reserve comment, as I've been caught when a similar warning system didn't work....