PPRuNe Forums - View Single Post - TAM A320 crash at Congonhas, Brazil
View Single Post
Old 10th Aug 2007, 15:13
  #1443 (permalink)  
discountinvestigator
 
Join Date: Mar 2006
Location: A oneworld lounge near you
Posts: 145
Likes: 0
Received 0 Likes on 0 Posts
With regards to deceleration, I think you would expect 1.7 m/s/s (or 0.17g in real units) and 3.0 m/s/s (or 0.3g) for Lo and Med on an Airbus, I seem to remember but I do not have the manuals in front of me. With Medium brakes selected you should still get 0.3g on a dry runway even with one engine EPR around 1.20. Don't go near the tyres afterwards and look at the colour of the carbon brakes! Same effect with full manual braking on a dry runway, both make the assumption that anti-skid is working.

Please be aware of the time frame and data recording buffer differences in this data. Please be aware of draft comparisons of FDR and CVR time.

PBL, I support your reasoning for the comments relating to making the investigation more public. There are others too, but I am not willing to discuss them here.

Secondly, there have been a few studies which show that pilot reaction time to engine failure on take-off for application of full brakes is around four seconds. I can see that figure and logical brain processing time being similar here for spoiler non-activation to brake application. As an academic, you might be able to find an old NASA contractor report, or similar, done in the late seventies or early eighties on this. They were investigating why so many aircraft fell off the end of runways with V1 RTOs. The answer was because the certification decision time was one second and the pilots took four seconds to react. The good news is that they increased certification reaction time for the pilots to two seconds.... now does this explain why we need runway strips and runway end safety areas?

As a side issue, they also found that pilots did not press the brake pedals fully, but that issue was included in training afterwards. Boeing lets you apply more brakes and only disconnects when you apply more than the autobrake setting. I think that Airbus disconnects on sensing foot pedal pressure, so actually applying manual braking can release the brake pressure and then apply more.

Finally, if you are going to do a WBA on this, can I join in please?

Discount
discountinvestigator is offline