PBL,
I'm thinking, for example, about the guidance concerning Loss of Braking. As in, how much extra runway might you need if you don't get the decel light (for whatever reason) and you follow the Loss of Braking SOP. Looking at data from this accident, it seems to me you could need 1950 m after TD (let's say at 250m beyond threshold), plus your procedural time for getting to stomping the pedals, which amounts to, say, 5 seconds (at 70 m/s) or 350 m. Total 2550m. You can reduce that to 2200 m if you choose to land with manual braking.
Would you please compare these figures with this little study I did somewhere else : ( I was off by 700 kg on the *official LW ).
"
First, a few facts :
1/- The airplane landed at CGH on runway 35L.
That runway is 1940m long and the LDA - landing distance available - is 1880m.
The METAR reports at 1720 was :340/08 6000m RA BKN 900 ft OVC 7000 ft Temps 16 / 14 QNH 1018 hPa
2/- Two experienced pilots were at the controls, one TRE and a qualifying captain.
3/- 187 people were on board.
4/- The airplane stayed on the runway centerline until just reaching the end of the runway, where it veered left.
5/- It seems official that the airplane was dispatched with one - #2 - reverser inoperative.
6/- The airplane seemed very fast and apparently did not lose as much speed as it would normally do.
7/- Some pilots noticed standing water on the runway, which wasn't grooved.
I jotted a few figures, making assumptions as to the weight of the airplane :
1/- Dry operating weight 41,000 kg
2/- 181 passengers and luggage 18,000 kg
3/- Fuel remaining on board, with a planned diversion to Guarulhos 3,000 kg
The above give a landing weight at 62,000 kg or 62 tons.
At that weight, the required landing distances are :
for dry runway : 1490 m
for wet runway : 1690 m
for 3 to 6 mm of standing water : 2130 m
Those are the baseline figures for sea level and OAT < 40� C, without reversers and without auto brakes.
Congonhas being 2600 ft above sea level, a correction of 3% per thousand feet applies for a wet runway, and 4% for 3 to 6 mm of standing water.
The resulting landing distances then became :
for a wet runway : 1690 x 107.5% = 1822 m
for standing water :2130 x 110.5% = 2354 m
Compare these figures to the LDA in fact #1."
My first comment when I compare both sets of figures (mine come from an
in-flight performance chart out of a QRH ) is that your results are very close to the *contaminated* runway data I obtained. Granted those are estimated performance, yours deduced from the actual braking achieved eventually by the crew.
Personally, I have never accepted the *wet* data outside big airports -those with looong runways- and at the flight preparation phase always gone *one state worse*, i.e in this case, my prep would have been with the quarter-inch standing water tables and the consequent reduction of the landing weight (fuel / freight / passengers). Furthermore, and it's one of the reasons I would dearly hear the pre-descent / landing briefing is whether they'd have been aware of the bad runway drainage and the presence, still visible the morning after the accident, of
pools of water. That concept of pools of water is important for it means a risk of potential
asymetric braking - a situation in which the use of autobrakes is discouraged.
I feel rather strongly about this aspect of this accident as I think that the dispatch of this flight hadn't been done with enough concern for safety. The thirty-five minute turnaround in Porto Alegre (they landed on frame 183400 and took off on frame 186060, leaving just under 45 minutes between them, to which I substracted 10 minutes taxi time.), didn't leave enough time for anything but a routine dispatch preparation.
IMO, this is an example of collective responsibility.