A320 Emer. Elec Config , Asda And V1
 

scenario:

Aircraft 320 G.W= 72T V1/VR/V2 = 145/145/150 ( ASDA) RWY= 3500M
hypothetically :rolleyes:
an emer elec config condition given at 140 kts with nearly half the runway behind. You elected to continue due to the degraded braking performance and reduced stopping dist avail. as the BSCU systems are inop and only manual braking is effective to a max 1000psi.

My question is that the certification of an aircraft with regards to v1, to my knowledge, is bascially based on the worst case failure happening at v1 and being able to stop the aircraft within the remaining dist available. Most example are based on and engine failing at v1 at max tow etc.. ... .....
However the airbus case is .........:hmm::hmm:
Looking into the QRH Abnormal Elec Emer. Conf. at 72t produces a vref of 142kts and a Actual landing dist Req. approx 2800m (Landing dist is factored by 2.5)
if we simplify the physics an aircraft landing at 142kts and rejecting at 140kts will have the same momentum (disregarding gravity). Hence logic would say that you would need 2800m to stop the aircraft if such a failure occurred near v1 (140kts).
BUT as we are told any MAJOR FAILURE below V1 we are instructed to reject the takeoff ....
During such a failure with the cockpit light and screens going blank to a degree added the stress and uncertainty of the situation, One would instinctively reject the takeoff and if so would certainly run off the end of the runway.
now considering the situation how valid would be the V1 value taking into account this particular failure... :rolleyes::rolleyes:
i been going over the Airbus manuals and nowhere does it instruct or inform the crew to the relationship between the particular failure, v1 and or decision to go. From what i have seen all scenarios regarding this failure are based whilst the aircraft is airborne.

go minded
 

BUT as we are told any MAJOR FAILURE below V1 we are instructed to reject the takeoff .


read again on FCOM 3.02.10 Reject Take Off section...

Emergency Electrical Config is not in itself a failure. It is an electrical configuration the crew can intentionally set in an attempt to control smoke/fumes/avionics smoke

Although setting Emerg Elec Config results in a loss of many systems, you get many of them back when you select GEN2 and EMER ELEC GEN 1 LINE on before landing, and as such that landing distance factor will not apply. You are more likely to end up landing in direct law (LDF 1.3 approx)

Note that ISIS, PFD1 and ND1 are all available.

Your scenario of "screens and lights going blank at V1" is not Emerg Elec Config, and would require multiple simultaneous failures at exactly the same time to occur.

Given the above, actual landing distance and ASDA (for the stopping portion) are not possible to compare when you dont know what failures you have. Just because screens go blank does not mean A/SKID and THR REV etc are not available and V1 is not the time to go fault finding i.e stick to what Airbus say in 3.02.10

If you are currently active on type I suggest you spend some time in the QRH.

Have a look at FCOM 1.24.20 "warnings and cautions"

Here you will see that several electrical problem will give a warning in phase 5, i.e. the T.O. roll between 80 kts and liftoff.

In my standard T.O. briefing I always say that I do not intend to stop for electrical problems in the high speed regime. This includes the loss of both GENs!

Indeed, if during t.o. roll you see several screens momentarily go blank, don't go in the "engine failure mode" immediately. If you can't feel thrust loss continue the T.O. ! The captain will get his screens back in a few seconds time.

Next time you have some spare time in the sim, ask the instructor to throw you a dual gen failure at 100 kts and see what happens if you try to abort!

The chance hat you'll ever get such a strange failure in reality is very small, but it does make a nice sim scenario. :ok:

Anyway, I think it's best NOT to stop for electrical failures at high speed as you might indeed have serious braking problems!

Best regards,
Sabenaboy

Thanks for the reply everyone ...

yes still trying to get my head around the airbus documents:ugh: its been nearly a year since a transitioned on type before was on the b737 which had a more sımplified documentation.

but thanks for the insight :))