After the Rejected Takeoff

[Nice Wing]

After the RTO

I recently carried out a Rejected Takeoff in an A330 at a relatively low speed. I can tell you from first hand experience that it all happens very quickly once the spoilers go and the autobrakes are applied with maximum force. The airplane literally stands on it’s nose and my focus was on getting the aircraft stopped and then getting word to the Cabin Attendants and Passengers not to evacuate.

Reading the post below on Rejected Takeoffs highlighted to me the requirement to turn the aircraft into wind to ensure that any fire was not directed towards the aircraft fuselage. This is written in our flight manual which I have read and thought about many times, but is not a situation I have ever practiced in the simulator. I wonder if it had been an engine fire if I would have thought about this during the RTO. Obviously this is something that I will ask to do in my next simulator session to evaluate how easy this is to do with a large aircraft and how easy it is to control with the autobrakes bring the aircraft to a stop using maximum braking.

In my airline and from the reading here, in most airlines we beat to death the calculations and decisions involved with aborted takeoffs. When we practice aborts in the simulator, we inevitably end up either carrying out an emergency evacuation with something on fire, or resetting back to the button for another takeoff.

The reason I am writing is to ask others opinions on what they would do after the RTO, assuming the aircraft has been brought safely to a stop the ECAM (emergency procedures) carried out. Now you are now stopped on the runway with brakes temperatures starting to rise.

Up to what brake temperature will you consider taxiing off the runway?
Would this be higher if you are at a busy airport with a single runway?
Would you taxi off quickly after the abort to try and keep runway clear before the tires deflate?
Would you consider having fire crews soak the wheels as a preventative measure if they are present and it is obvious that the temps are going very high?
Will you be unnecessarily damaging the brakes by doing so?
When would you start the evacuation with fire crew on the scene and brake temps rising?
Would foam or water be better for cooling the brakes?
After a low speed abort would you consider a second try if the problem has cleared?
Are there any brake energy limits on the A330 for takeoff?
If your brakes temps were fine starting the takeoff, but you get a brakes hot message at V1-10 knots, would you stop or go? (this is a non-inhibited message on the A330, so would give a warning message even at V1)

I am not looking for quotable answers, just your thoughts and opinions.

For reference in this discussion here are the temps and implications of them for the A330. (degrees C and carbon brakes)

>300 – do not take off as hydraulic fluid may ignite in the wheel well when gear retracted.
>450 –may get smoke from the brake from any fluid contamination (not necc. a fire)
>550 -need brake cooling to prevent acidification of hydraulic fluid
>600 - may have a fire, seek outside aircraft confirmation (tower – other a/c… ;)
>800 – fuse plugs go and the tires deflate
>900 – time for a new set of wheels, brakes and tires

Thanks for any input

[ 25 October 2001: Message edited by: Nice Wing ]

[Bhing]

Hi NM,

This is a very complex question indeed. As a 340 operator myself with more than 6000 hours on A340/A320 we are talking about a similar piece of kit. In fact the brakes are exactly the same. Yes the brakes are fantastic but they are very susceptible to damage if you do a max stop from a reasonably high speed. The other point to remember is that the true brake temperature takes about 5 minutes to be reflected on the indication due to sensor location.

Regarding you concern about brake fire spreading beyond the wheels. Next time you are under the aircraft, have a good look at the space around the wheels and you will aggree that it is unlikely that fire will spread beyond the wheels. What is of more concern is the possibility that debris from failed wheels or brakes may have punctured the wing fuel tanks above (as in many previous accidents).

Now your concern about getting the aircraft pointed into wind. For the A330 (A340) and other similar large aircraft that I have operated it is critical to first get the aircraft stopped as per SOP's. Now to get the aircraft pointed into wind is another thing that takes time. Time being the commodity you can ill afford in a real emergency. May I recommend to you that it is far more important to stop exactly on the centreline for a very good reason. Usually runways slope away from the centreline, thus if you do have a fuel tank punctured then fuel leaking to the ground will flow away from the fuselage. For your information I have tried to practice pointing into wind and I have found it unsatistactory for many reasons. One is mentioned above but another is the fact that you will now have the nose of the aircraft pointing at and maybe close to the runway edge. This will now cause evacuation problems but more importantly cause difficulties for the fire crews as the first strike for these emergency staff in case of fire is from the front of each main wing. This may now not be possible.

Regarding your various questions about brake temperatures etc. The answer is basicly answered by Airbus in FCOM 3. If you do a stop from above 100 knots it is serious. The degree is based on what brakeing you used. If the reason for stopping is not serious and you quickly released the auto MAX brake and used only low brakeing, then I see no problem with any decision about what you might opt to do subject to brake limit temp. If you used MAX brake to stop from above 100 Knots, then thats it - stay stopped. Don't move the aircraft regardless until you have been externally inspected and have a clearance that is is safe to do so. I have physically inspected brakes that were used to stop from about 120 knots using auto MAX and they were completely destroyed. Even trying to taxi the aircraft would not have been safe if at all possible. By the way it is not recommended to put anything but cool air on carbon brakes without risking total destruction of same.

Re the stop/go question - definately NO. Just leave the gear down after take-off until they cool down (unless you have an engine failure)

So in summary, stay on the centreline, stop, sort out the problem, and only when you are completely happy that it is safe to do so (preferably after an external inspection if in any doubt), then taxi off the runway. If it is a single runway airport, then all I can say is "you can't help bad luck" but you and your passengers have priority and safety is the priority.

If you want to read a very good accident summary on this subject especially on the things NOT to do, just look up the British Midland Rejected take-off accident many years ago now.

I hope this gives you something to think about

Have a nice day

[The Nr Fairy]

Bhing :

My understanding is that the reason for pointing the nose out of wind is in the event of an external fire - in theory the wind should blow flames and fumes away from the cabin.

Unless someone can point me to another accident which provided an impetus for this, I think the Manchester 737 fire you refer to, which killed 50 or so people, was a turning point. Most if not all the casualties were caused by inhalation of fumes, either from the engine itself or from the burning of cabin contents initiated by the flames from the engine which were blown over the cabin by the wind ( not directly burned ) - most if not all would have survived had the damaged engine been upwind and flames and smoke not penetrated the cabin. For those interested, the full report is to be found here (http://www.aaib.detr.gov.uk/formal/gbgjl/gbgjl.htm).

I would query any logic about stopping in line with the centre line - is not the onus to ensure the passengers ( and you ) have the best chance of exit and therefore survival, not to make things easier for the arriving emergency crews ? The biggest contributory factor to a successful evacuation is more time, and more time without fumes in the cabin.

I'd welcome any numbers people have on the ratio of people overcome by fumes compared to those burned to death in similar accidents to support, or disprove, my point.

And a caveat - my knowledge of this specific area is taken from a non-professional pilot perspective, and gleaned from accident reports and other posts on PPRuNe.

[A and C]

On the issue of cooling the brakes this should be done by letting them cool down WITHOUT assistance from the fire crews water or foam as the thermal shock may result in the wheel exploding ,if the landing gear is on fire this should be put out with dry powder.

I suspect that a fine water mist could be used to cool the landing gear but i,m not sure that i would want to be the first to try it as a hot wheel with a tyre at 200psi (cold) could be described as an unexpolded bomb !.

[Nice Wing]

Thanks for your responses. It is interesting to hear the ideas and reasonings of others.

I personally would be tempted to taxi off the runway if all was well, but the brake temps were still rising. My understanding is that it will take at least 15 minutes for the temps to actually rise, and that this is not just an indication problem. Why not get the aircraft off the runway before the tires deflate.

As evacuation will cause injuries, I really question whether one should be evacuating the aircraft with brakes that are heating up to the point of fire if the fire crews are on the scene. It is however hard to know the source and extent of any fire. Thoughts?

How many of you big jet drivers actually think about stopping into wind on aborts?

[moggie]

Yes the Manchester accident changed the way BA handle RTOs - ANY engine failure is treated as a fires and the engine shutdown once the aeroplane has come to a stop (using the Engine Fire Checklist memory action). We train pilots for BA and they also push the "turn towards the dead engine if you have a headwind" philosophy - to blow external fire away from the fuselage.

BA policy is to evacuate ONLY if the Captain believes it to be more dangerous to remain on board (and this really means an uncontained fire). Hot brakes or an engine fire that has been fully extinguished (backed up by visual inspection) would not normally justify and evacuation.

I have only ever had one RTO - engine failure at IAD in a VC10 from 100kt. We had no brake temp gauges but in the absence of obvious problems on a visual inspection we taxied clear.

I have also had one evacuation. This followed a tyre burst in the wheel well at top of descent, leading to ruptured fuel lines, double engine failure, loss of all fuel in the port wing and unknown damage to the maingear in question and fuselage (we in fact had broken the pressure hull, too). We stopped ASAP after landing, were told by the fire crews that we had fuel dripping onto hot brakes and so elected to evacuate. Good news was a pax load of 38 Royal Marines who were calm and organised during evacuation - but don't fancy trying it with 250 men, women, children and drunks.

[RatherBeFlying]

Heat from the brakes will take some time to heat up the tires by conduction/radiation; so, just after an RTO the tires will not have reached their maximum temperature and may be usable to turn off a very nearby taxiway provided any smoking pieces are kept downwind.

Delaying evacuation unless/until a "contained" fire becomes uncontained carries the great likelihood of being subjected to long series of tedious questions at inquiries and lawsuits brought by grieving relatives.

I recall an incident at Calgary where the passengers initiated the evacuation when the smoke became obvious and all survived -- I believe the a/c was destroyed or severely damaged. Time is far too precious at such times to squander waiting for emergency services to drive up and sort out their equipment -- seconds count.

[moggie]

People get hurt when evacuating down the chutes - and a broken back caused when evacuating un-necessarily will also end in a law suit.

Quite honestly, the only time you can make the decison to go out or stay in is when presented with the circumstances on the day. No two incidents are identical, and hindsight will almost always prodcue a better plan than the one the crew had to formulate when under pressure on the day.

Both arguements have their merits, different airline have different ideas and there may be more than one right answer in many cases.

However, the point on tyres heating up for some time after the RTO is valid - that is why we also checked the brake cooling graphs before taxying clear.

[rr892igw]

The 330 I flown had brake fan installed which
will shortern cooling time by half.It is helpful if the fault has gone and you can try another takeoff in 25-30 minutes.
Decision to turning the plane requires more info than just fire warning indication in the cockpit,probably visual confirmation would help(not that the cabin crew are good at it!).Why not open the sliding window and stick you head out to see for yourself?
Then the big word comes "Commander's discretion".

Happy flying. :cool:

[RatherBeFlying]

Perspectives can be quite different: The pilots have two cockpit escape windows and two passenger doors close by and the FAs are seated by the exits.

Passengers can be several rows away from the nearest exit with several score people to queue up behind.

If I'm in the back, any hint of smoke/fire and I'm going for the exit NOW.

The frail and handicapped may well be better off waiting to see how the situation develops -- and their chances will be better in the case of smoke/fire going uncontained if the bulk of passengers are already off.

[GlueBall]

RTOs come in different packages. Runway Length, Wet/Dry pavement, Airport elevation, Airplane Gross Weight,... are all factors affecting technique. Assuming Max Gross Take Off Weight: If I had a V1 cut on Rwy 13R (14,572') at JFK I wouldn't have to stand on the brakes and risk a brake fire. But if I were on Rwy 13R (12,467') at Santa Fe De Bogota (Elev 8355') a V1 cut would be a most violent maneuver with probable multiple tire failures, directional control problems and wheels glowing cherry red. Under the latter scenario I wouldn't be concerned about "facing into the wind" nor would I be dabbling with lengthy "evacuation/shutdown checklists." Because I already know that there will be a brake fire, I would give the evacuation signal for all non everwing exits, order the fire handles pulled and then get out the door if the slide inflates, or via the inertia reels. There would be no need for me nor for any other crewmember to waste precious seconds to assess, to deliberate or to second guess the situation at hand.
:eek:

[Nice Wing]

Glue Ball,

This is where this all gets interesting. You have said "Because I already know that there will be a brake fire, I would give the evacuation signal for all non overwing exits, order the fire handles pulled and then get out the door if the slide inflates, or via the inertia reels. There would be no need for me nor for any other crewmember to waste precious seconds to assess, to deliberate or to second guess the situation at hand."

However other threads above and myself would not neccesarily be so quick to evacuate. When has a brake fire ever led to an aircraft fire? Why do so many of us assume and train to order an evacuation at the first mention of the word fire? I am not sure that this is always the best decision.

I obviously cannot say that such a decision is right or wrong, but I can say that I think it is rarely cut and dried. You have decided that in these circumstances, you would evacuate. Fine. That was the extent of my analysis prior to a couple of weeks ago. What I am now thinking about and asking is when you you give it another try? When would you taxi off the runway before the tires deflate? Would the fire crews attending a brake fire and staying onboard not be preferable to ecacuating when you have a brake fire? and the rest of the questions above :confused:

[RatherBeFlying]

Time to bring in some physics here; namely, the amount of energy to stop a given mass at a certain velocity is a constant whether standing on the brakes or being gentle.

The energy required from the brakes can be reduced with headwind, spoilers and reverse thrust from remaining symmetric or centreline (DC-10, 727) engines -- i.e the failed engine and its opposite are unavailable for reverse thrust.

Memory fails me on the details, but an accident report from an RTO in the US some twenty years ago found that gentle braking instead of heavy braking led to a brake fire that consumed the aircraft -- happily everybody got out.

I do not recall the precise explanation why the gentle braking was implicated. I suspect heavy braking is more energy efficient and obtains the most velocity reduction for a given amount of heat production. The margins at limiting conditions are narrow and the lower braking efficiency (in the physics sense Work/Energy Expenditure) put the brakes over their limits.

[moggie]

Thought: Does heavy braking reduce the amount of heat created by getting the wheeks stationary more quickly, therefore reducing the amount of time that they are flexing and heating? After all, it is the number of rotations of a tyre that determines how much they heat up when taxiing.

As for "reverse is not available on the failed engine or it's oposite" - well you can use asymmetric reverse thrust (I have done it) provided that you are prepared to reduce/cancel it if you get a drift. Also worth thinking about which side the wind is from - reverse on the right hand side would help to cancel a strong crosswind from the left (thrust yaw vs weathercocking).

I still maintain that a policy of immediate evacuation as opposed to assessing the situation first is fraught with hazards. Anyone seen the video of the Pan Am acident at San Francisco when the folks going out the front doors of the 747 dropped vertically to the tarmac because an aft CofG had the aeroplane tip back on it's tail? No-one staying on board was hurt because the brake fire went out.

what I do say is that each case must be treated on merit and no two RTOs will be the same.

[GlueBall]

There's high risk involved in keeping passengers aboard during a brake fire. For one thing, passengers will not sit idle when they see smoke rising from underneath the fuselage, especially those who are seated directly below the source of the smoke. Additionally, when smoke is pumped into the cabin by A/C Packs, passengers who don't see the smoke will smell it and become desperate and claustrophopic if ordered to remain seated. Furthermore, the response time of fire trucks may be insuficient to check the propagation of flames and heat from reaching the center fuel tank. The risk of explosion is just too real to take the chance of keeping anxious, desperate, passengers in their seats.

Typical MTOW scenario. Click It (http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20001208X08661&ntsbno=LAX97FA276&akey=1)

[ 28 October 2001: Message edited by: GlueBall ]

[RatherBeFlying]

Moggie,

Tire flex will contribute to heat accumulation during an RTO, but I do not have the numbers or formulae to properly apportion or even guess the heat build-up components.

Yes, something less than full reverse thrust may be useable from an asymmetric engine depending on the factors you have mentioned. I plead guilty to trying to explain too much too consisely.

In the Gimli Glider incident where an Air Canada 767 ran out of fuel, the nosewheel collapsed. The passengers who evacuated the rear doors also suffered severe injuries from a near vertical drop to the tarmac. So yes by all means, evacuate by the lower exits when one end has come down to the ground unless there's a fire in the way.

[HalesAndPace]

With reference to use of reverse thrust, am I right in remembering that Performance A assumes that in the event of a rejected take off, reverse thrust is assumed inoperative? Boll*cks to turning off the runway, stop aircraft on runway (turning into wind if emergency/brakes/steering allows), run emergency checklist for immediate problem, evacuate soonest if needed.

[Hudson]

Re B737 aborts. One of the things that I noted in the B737 simulator was that the pilot sometimes concentrates too much on getting the throttles back through the interlocks into reverse, and imperceptibly relaxes pedal pressure on the brakes. This was on the 737-200 non-RTO. On the 737 Classics there was the temptation to instinctively over-ride the RTO function, and disconnection of RTO could also occur inadvertently if the aircraft was swinging off the centre line for whatever reason.

Unless the runway is wet, reverse thrust does not make much difference to an abort. In fact I believe it is only worth 80 feet in the 737-200. I believe that there is the danger of too much accent on selecting reverse rather than concentrating on maximum brake pedal pressure throughout the abort.

[moggie]

As I understand it, reverse thrust is not considered when detrmining performance for regulatory purposes - so if available it is a bonus. However, if used properly and in conjunction with the other stopping aids (correct training!)then it will shorten the stopping distance. However, if not used properly it may be a distraction or even contribute to directional control problems. advice - learn the correct technique for YOUR aeroplane.

As for the point on tyre flex - the brakes create x amount of heat when stopping a particular aeroplane from a particular speed at a p[articular weight. So, if you stop quickly, you will create the same amount of heat from the brakes but the fewre number of tyre rotations will create less heat through flexing.

In my experience of training pilots, most are under the impression that they have applied full braking when in fact they are only applying 1/2 to 2/3 braking effort. they are amlost always surprised at how hard you have to press to stop. So, if you have autobrake with an RTO setting - let them do it. If not - push like your life depends upon it (which it may).

As an aside, the motor manufactures are finding the same problem - people drive into an accident with only partial braking applied. This is why we now have Emergency Brake Assist which increases braking effort if you keep the pedal pressed for a certain period of time. The computer assumes that you MEANT to do an emergency stop, even if you actually are not! RTO setting equivalent?

[RatherBeFlying]

Moggie, I'm not sure that reduced final brake temperature when heavy braking is applied is solely due to reduced tire flex -- mind you I don't have the numbers.

Speculating, I can conjure up two other mechanisms: Reduced time the brake pucks are held against the disks at low efficiency Increased erosion of high temperature particles

A brake disk erodes and loses mass with successive braking applications. A maximum effort stop from a given speed at the same weight and other conditions will produce a lower final temperature on a new disk than on a thinner disk near the end of its useful life.

For that I can offer an equation:

T = mEc

Where: T - Temperature increase m - Mass E - Energy Transfer to disk c- Heating coefficient of brake disk material, i.e. Temperature increase of unit mass of brake disk material per heat energy unit input

[scanscanscan]

I recall an Air France 747 did a low speed abort at Bombay rw27 and cleared and stopped on the runway turn off, to sort things out. The brakes were hot (as was the oat) and they caught fire.
Two fire tenders were dispatched, and one turned over when it did a "go direct" fully tanked, over the soft grassland.
The remaining fire tender refused to approach the 747 as all four engines were still running.
The fire progressed and the 747 was destroyed.
The fire tenders were unable to communicate with the 747 crew by radio.

At Delhi a new 747 again Air France aborted on Rw26 and slightly over ran the runway,all the passengers exited uninjured by the L1 door step (about 2ft) the 747 having ploughed into the soft earth clearway. This time there was no brake fire the wheels being several feet under the earth.
I believe this 747 was a write off.

At CDG a GF L1011 had a main tyre failure on takeoff, shortly followed by its axle mate,( the double pop sound) during the abort the remaining tyres on the same side were destroyed, and the gear leg ploughed a furrow in RW27 effectively slowing and then stopping the aircraft.
The GF L1011 tyre problems were cured I recall, by useing only new tyres,slightly increasing the pressures, and monitoring these pressures to ensure the correct inflation after every landing.
Crews were instructed on straight line taxi speeds and brake application methods, and taxi speeds in turns and the degree amount of these turns allowed.

Regarding brake application on Boeings 767/757 during aborts.
The following points I recall, and hopefully they may help.
Sometimes it is forgotten that on top of the rudder pedals are brake horns, and the feet have to be lifted well up onto these horns. They are positively and agressively rotated at full force by the pilot, with the ball of his feet,during serious high speed aborts, simple toe pressure will not achieve the stopping distance.
Often also forgotten is the immediate manual follow up of the speedbrake lever after smart closure of the throttles and the ATs disconnect.

[OverRun]

Bhing raised two good points I'd like to comment on.

First, a recommendation to stop exactly on the centreline - fully agreed. Almost always, the runways slope laterally away from the centreline at a gradient of at least 1%, which is enough to clear rain pretty quickly, and it'll do the same with fuel. If you do have a tank punctured, then fuel will definitely flow away from the fuselage. You can genuinely stand on the runway, and watch liquid flow off.

Secondly, stopping in the middle of the runway does make it easier for the fire crews. They can then drive up the runway and deploy around the aircraft.

Fire trucks are very heavy and can struggle on soft ground. They've got the power and the all-wheel drive to grind across the grass if they have to. (We've got 6 fire trucks, and I've designed plenty of roads for them). The crews often have the training to do likewise. But the grass beside the runway might be softor muddy. The true life stories are legion - about what can go wrong can go wrong can go wrong in the process. Best to keep it easy and simple.

[The Nr Fairy]

Overrun - if fuel isn't on fire, it won't harm you unless you drink it, but it's more harmful if it's on fire or the smoke is blowing over the fuselage.

I think it boils down to the priorities in the actual situation. My gut feeling is that most crews will want to maximise the survival of pax as it tends to maximise theirs.

[GlueBall]

What a brake fire can do for you, when not extinguished soon.BRAKE FIRE! (http://www.airdisaster.com/photos/madras/photo.shtml)

[RatherBeFlying]

I see the APU extinguisher did an excellent job. :D

[Lima Xray]

Can I put a question to the design of landing gears and wheel brakes?

The question arises what have design engineers so far come up with to cure live threatening (simple) wheel fires. What can be done about improving cooling agents and or onboard fire fighting agents?

[RatherBeFlying]

So it seems that brake fires only happen on hard surfaces. If you go into the overrun or off the side and bury your wheels, there's no oxygen to sustain the fire. Something else to carefully consider in the building panic if there's no fire crew doing an effective job and the smoke and flames are increasing.
And the pax get a softer landing off the slides.
Then all you have to do is sell the chief pilot on your ex tempore brilliance while he's looking at a fat bill for pulling the a/c out of the mud and major structural repairs.