We started using EFB over a year ago. Within weeks on the line I found FO's proposing all sorts of homespun ideas on how to increase the stop margin when they felt it necessary. These were often not their own ideas, but methods they'd been shown by other Captains.
Personally I think it is dangerous and deluded to play around with the data inputs (altering TOW?! altering RWY length!?) without a specific policy or procedure published by your company. You might THINK your modifications are reasonable and even conservative - but think about the consequences of any kind of incident where an RTO goes even slightly wrong. Your 'massaging' of the EFB figures is going to be used to hang you out to dry. You will carry the blame for the incident/accident. Do not do it. If your company has a recognised policy which might improve the Stop Margin, use it. Perhaps an intersection TO calculation is allowed. That will legally allow you to improve the Stop Margin figure.
This issue is most likely to be a problem when doing FLEX TO's of course. The EFB will seek to acheive MAX FLEX TEMP and this can mean even a low weight takeoff on a long runway showing minimal stop margins. The EFB software does have an option to choose a REDUCED FLEX Temp. That would be the ideal solution. It is what we used to do when we had paper tables - Airbus published a procedure allowing the Commander to drop the FLEX TEMP down to a lower value if he felt the need. In my company they have not activated this EFB option - meaning,
they have taken away my ability to reduce the FLEX if I felt the need. In my opinion this is a retrograde policy and one which further erodes the Commanders right to exercise Airmanship and Command decision making. When I asked them why they did so they told me they think it would only 'confuse' pilots!
The REAL reason is - they don't want you to reduce the FLEX temp, for economic reasons (somebody above charecterised this as 'not trashing the engines! Bull.). Its all about the $$$.
Unfortunately it leaves me with only two options. I can choose only MAX FLEX, or TOGA. Which ultimately costs them more $$$.
So when compared to using paper charts for take off performance, we don't have access to stop margin information ( I always assumed it to be 0m anyway ), now we can see a figure some people are uncomfortable with it
I've heard this argument in my company too. "You're only worried about stop margins now because now you can actually SEE the stop margin, when before you couldn't!".
Two things about that argument; First - having been in this business for decades and on multiple types, in all sorts of weather conditions, and on all lengths of runways, I think I have a fair idea about the RTO risks I might face on a short runway with high WAT conditions. Call it 'experience', call it 'intuition', whatever you like - but I'm not dumb enough to be suckered into believing it carries the same risk as a 10'000ft runway in low weight and perfect ISA conditions. I don't need a pretty picture on an EFB to tell me to consider a lower FLEX Temp, or even TOGA.
Second - when I went on the Airbus I got a new system called EGPWS with a nice picture on a TV display. I already knew where the terrain was - I briefed that from my charts, including highest spot heights, terrain location relative to my SID/STAR, highest Sector MSA's etc. But now I have it all right there in living colour on my ND. It enhances my already good situational awareness. I'm glad to have it.
Likewise with the EFB. I always knew the threats, and how I could mitigate them. The EFB gives me even greater situational awaeness, thus improving my safety margins.
Should I turn off the EGPWS picture if it interferes with the $$$ imperatives?
Should I turn off the EFB stop margin display if it interferes with the $$$ imperatives?
It seems some already do!
Disgusting.