Thanks for highlighting my error after I'd edited my post to correct it.... I got in to my head the original post referred to Dublin, hence me thinking it came under the IAA rather than AAIB. I do have reasonable knowledge of the boundaries and major settlements within the United Kingdom and its constituent nations, and those of the Irish Republic, I just made an embarrassing misreading.

Thanks for the link Stephen, better than going off some dubious journalism! Somewhat surprised the crew didn't go for TOGA until after rotation, despite recognising the problem far earlier.

Edited November 22, 20187 yr by ckyliu

If you read the official report, it talks a lot about developing a Take-off Performance Monitoring System and explain why the working groups said it was not possible. Since I am definitely not a science guy and therefore fail to understand that(my bad!), can someone (who read the report) explain why it wasn't possible? You have the data: t/o weight, use-able runway length, qnh, N1 value, etc... Is it difficult to develop a software which will say "Hey with this acceleration rate you wont be able to hit VR (or V2) by the time you reach the end of runway, once the take off roll starts?

From the report: " The aircraft’s FMC did not have the capability to alert the flight crew to the fact that they had entered the incorrect OAT into the FMC, although this capability existed in a later FMC software standard available at the time."

So the solution to this problem looks pretty simple from where I sit...update the FMC software!

 

Forgive me for my potential lack of understanding, but it looks like the pilots failed in at least two important points, inputting the wrong temp in the fmc and not monitoring their N1 gauge during the take off roll. Stating that it only gave them 60% of the require takeoff power is quite a big discrepancy to not notice at some level, regardless of whether they did the calculations or not. Sure a 5-10% off is understandable but 40%, especially for pilots who have many hours in that flight deck?

Edited November 22, 20187 yr by Kevin_28
was going to delete, but someone already posted a response, so might as well keep it.

10 minutes ago, Kevin_28 said:

Forgive me for my potential lack of understanding, but it looks like the pilots failed in at least two important points, inputting the wrong temp in the fmc and not monitoring their N1 gauge during the take off roll. Stating that it only gave them 60% of the require takeoff power is quite a big discrepancy to not notice at some level, regardless of whether they did the calculations or not. Sure a 5-10% off is understandable but 40%, especially for pilots who have many hours in that flight deck?

The actual N1 was about 81% -- a little low but perhaps not entirely unreasonably so (and only about 10% N1 less than the actual required setting of about 90% N1).

The "60%" figure AFAIK is based on an estimation of the actual thrust output (i.e. in lbf) (which is obviously non-linear with N1). 

1 hour ago, w6kd said:

So the solution to this problem looks pretty simple from where I sit...update the FMC software!

 

That's what they did in the end 🙂