AirAsia over run.

[Sop_Monkey]

I have an idea that may address this problem. The military are of course familiar with these.

What about installing drag shoots for braking. As some of the speeds mentioned the chute maybe the only way to retrieve the situation to a manageable level.

Why not have a net installed at each end of runway. If the controller thinks there maybe an over run he could have the net raised. Or it could be automated. Not sure what sought of installation would be needed to stop a runaway A380. Quite substantial I would imagine.

[fa2fi]

Or you could just fly a stable approach and if you don't get the flare right, go around instead of floating half way down a runway just to save face. It would be a lot easier, cheaper and of course safer.

[Sop_Monkey]

Oh yes that's the obvious solution of course. It's the mindset we are having difficulty with.

[DaveReidUK]

What about installing drag shoots for braking. As some of the speeds mentioned the chute maybe the only way to retrieve the situation to a manageable level.

Don't be silly.

[Doors to Automatic]

I suggested a FBW enhancement in another thread in which the computers could partially deploy the spoilers in the event of a float to 'help' the aircraft onto the runway earlier. It was pretty much dismissed and I am willing to bet my sanity was called into question in private! However about a week later I was astonished to read (in Flight International) that this very technique was actually deployed manually during a hot and high landing into Grand Cayman and that it PREVENTED an overrun! I think this needs to be looked at again!

[Metro man]

On the A320 the spoilers can partially deploy if the aircraft is not quite on the ground if certain conditions are met. Eg one main gear only or a bounce. It is called the Phased Lift Dump Function.

The spoilers will also deploy automatically even if not armed if both main gear are on the ground, reverse is selected on one engine and the other is below max continuous.

[SlamBam]

Conf 3 is apparently standard with Air Asia Philippines. Dunno about the other affiliates.

[Dan Winterland]

Saves a few KG each approach. But all those years of savings are wiped out instantly with an over-run.

[Dan Winterland]

What about installing drag shoots for braking. As some of the speeds mentioned the chute maybe the only way to retrieve the situation to a manageable level.

Nice idea, but I suspect, you're thinking that it could be deployed if it's clear that an over-run is going to happen. Unfortunately, as the majority of a brake chute's work is done immediately on deployment at a high TAS, (drag increases as a square of the speed) at this stage it will have little effect and be practically useless. I used to fly a 4-jet which regularly used a brake chute. The majority of it's effect was within the first four seconds after fully deploying. In strong crosswinds, we used to dump it after those four seconds.

For regular use, the time available required to retrieve and re-pack the chutes will really slow down the operation and it won't be cost effective.

[White Knight]

Originally Posted by Dan Winterland

Carbon brakes wear every time the brakes are applied. As they cool after use, the top layer oxidises and this is what gets worn away on the next application. So if you use full reverse on landing, the brakes apply, then the reverse comes in. At this point, the brakes release a bit to maintain the set deceleration rate. When you stow the reversers, the brakes apply a bit more again to maintain the deceleration rate. By using reverse thrust, you achieve the same landing distance, but e=wear the brakes more and use more fuel. In dry conditions, there is little or no benefit in using full reverse thrust. In wet conditions, or worse, the brakes may not achieve the full selected deceleration rate, and this is where greater than idle reverse thrust should be considered to achieve the desired rate and reduce the landing distance.

It does however take a few minutes for the brake surfaces to oxidise; therefore the autobrake modulation during a single landing won't make any difference to brake wear. In fact, on 330/340/380 SOP is to use full reverse to 70 knots. With the 330/340 we were permitted to brief and use idle reverse (when fuel was at it's peak), but for the 380 the BTV autobrake setting requires full reverse! That's because reverse thrust is far more efficient at higher speeds - as I'm sure you're aware, and the brakes only 'kick' in later in the landing roll.

I know it's not 320 but does give a bit more background perhaps

Anyway - if it's wet and kakky then anything that helps you stop should be used and damn the brake wear!

[Sop_Monkey]

Dan

Correct. My suggestions were rather tongue in cheek.

Yes aerodynamic (reverse or chute) braking for high speed and wheel brakes and barrier for low speed.

[EK380]

BTV FULL REV?

White Knight, not sure where you got the "BTV requires full REV with BTV on the A380"?

No such requirement and IDLE REV is allowed on the A380.

[White Knight]

Possibly because EK380 the 'wet' stop line is calculated taking into account the use of Reverse Thrust, and secondly BTV is not available if a thrust reverser is INOP!!!

Reverse idle is fine without BTV but I don't agree with it on a short runway on a kakky day. As I stated already.