Strange procedures followed after RTO by Cathay Pacific B773 at HKG. 18 injured.

[flashcrash]

(2) FL360aero on Twitter: "18 people have been injured due to emergency evacuations following a Cathay Pacific Boeing 777-300ER aircraft (B-KPQ) aborted take-off on Runway 07R of Hong Kong International Airport (HKG/VHHH), that resulted in tire bust on 24 June. #incident #aviation https://t.co/quexhyvHW0" / Twitter

The story is probably confused and the facts garbled, but it would appear that the aircraft taxied to the gate after the RTO instead of waiting on the runway for ARFF and brake cooling. The high temp plugs on the gear then blew out during the taxi, puncturing the tires, the slides were inflated at the gate (?), several passengers took luggage with them damaging the slides, multiple elderly passengers were injured, two of them seriously.

[Gabriel]

I would like to know why the evacuation was ordered. I have seen cases of brake / tire fire where an evacuation was NOT ordered.

[LH-B744]

I've never in my life seen the consequences when I use the RTO knob in Randazzos B744 simulator. But I still assume that the RTO knob for 744, 748, 773ER and others once was invented
to save lives. 18 injured.

But all souls on board have survived. A good knob.

[Evan]

I've never in my life seen the consequences when I use the RTO knob in Randazzos B744 simulator. But I still assume that the RTO knob for 744, 748, 773ER and others once was invented
to save lives. 18 injured.

But all souls on board have survived. A good knob.

RTO knob? I think you mean the autobrake selector. But you should be setting that to RTO before every take-off roll.

[Gabriel]

I've never in my life seen the consequences when I use the RTO knob in Randazzos B744 simulator. But I still assume that the RTO knob for 744, 748, 773ER and others once was invented
to save lives. 18 injured.

But all souls on board have survived. A good knob.

Does the Randazzos B744 simulator simulate brakes temperature?
In any case it is totally normal that a high speed reject in a heavy plane results in brakes overheat and fuse plugs melting (fires deflating to avoid exploding) and even small transient wheel fires for cases close to worst-case (V1 reject at MTOW in a high-hot airport). You can see that result in every maximum brake energy rejected take off certification test, like this one.

https://www.youtube.com/watch?v=f4LFErD-yls

https://www.youtube.com/watch?v=_g6UswiRCF0

[flashcrash]

I would like to know why the evacuation was ordered. I have seen cases of brake / tire fire where an evacuation was NOT ordered.

So would I. It seems very strange to do it using slides at the gate. According to SCMP, all flight crew have been relieved of duty as "standard protocol"
Hong Kong’s Cathay removes pilots and aircrew from flight duties after aborted take-off, stresses decision is ‘standard protocol’ | South China Morning Post (scmp.com)

[Gabriel]

So would I. It seems very strange to do it using slides at the gate. According to SCMP, all flight crew have been relieved of duty as "standard protocol"
Hong Kong’s Cathay removes pilots and aircrew from flight duties after aborted take-off, stresses decision is ‘standard protocol’ | South China Morning Post (scmp.com)

Those stupid moves for PR.

You have all the staff very likely with a very similar training, skill and culture. And you are removing the only crew that is most likely not to make this mistake (again).

[Evan]

A good knob.

The RTO setting is going to apply the most braking pressure the anti-skid will modulate. That is going to overheat the rims and blow the fuse plugs (and maybe start the tires on fire).

But what if you are rolling on a runway that is a good 2000-3000ft longer than your required runway length, which already takes into account an RTO at V1?

Should you set the autobrakes at 4 or even 3 instead. Would doing so actually be safer in the end?

Hmmm...

[Gabriel]

The RTO setting is going to apply the most braking pressure the anti-skid will modulate. That is going to overheat the rims and blow the fuse plugs (and maybe start the tires on fire).

But what if you are rolling on a runway that is a good 2000-3000ft longer than your required runway length, which already takes into account an RTO at V1?

Should you set the autobrakes at 4 or even 3 instead. Would doing so actually be safer in the end?

Hmmm...

No. The temperature of the brakes after you stop will be about Tf = (Mp*V^2)/(2*Mb*C)+T0 no matter how hard you brake.
This equation says that all the kinetic energy that the plane has when starting to reject the take-off is converted to heat in the brakes.
Adding extra 5 or 10 seconds of heat dissipation because you take 5 or 10 extra seconds to slow down to a stop with a lower deceleration will make virtually no difference.
The use of reversers may do a little more difference if you brake less hard, since the reversers have more time to take more kinetic energy away and hence less kinetic energy has to be taken by the brakes. However if the difference is between braking very hard or ridiculously hard, the difference is still going to be very small because the brake force is so much higher than the reverse thrust. If you are in a very long runway and either use a lower autobrake setting (like 2) or the runway is wet so the brakes will not be able to apply that much force regardless of the autobrake setting, then the reversers start to do a more meaningful difference.

In other words, the effect of stopping from the same initial condition using different autobrake setting is mostly how quickly you heat up the brakes, not how much.

In any case, I don't know of any case where it is appropriate to start the take off roll with the autobrakes in 3 or 4, Imagine that you are past V1 and past Vr and the plane will not rotate or you have a multiple engine failure or something that forces you to abort. You will want ALL the braking ability and then some.

[Evan]

Another RTO taxiing back to the apron on the rims. Air Algeria. Three RTO's five minutes apart. You can't make this stuff up:

http://avherald.com/h?article=50b3e29c&opt=0

[flashcrash]

You can't make this stuff up:

http://avherald.com/h?article=50b3e29c&opt=0

What were they thinking????

[Gabriel]

What were they thinking????

You are going too far making bold assumptions, like that they were thinking.

[3WE]

The RTO setting is going to apply the most braking pressure the anti-skid will modulate.

Incorrect, the full ~3000-something PSI is sent to the brake actuators /Blue font

[flashcrash]

Incorrect, the full ~3000-something PSI is sent to the brake actuators /Blue font

That blue font tag is a little small isn't it? How about actually making the font itself blue? Just a thought

[BoeingBobby]

Incorrect, the full ~3000-something PSI is sent to the brake actuators /Blue font

I'm staying out of this!