QF72 Story
Morno.
I admit I am completely unqualified, but I have always wondered if ‘what’s it doing now” goes through crew mind, then getting it into Alternate Law, or Direct Law if possible, would at least put pilot back in charge.
I have been reluctant to ask this given my lack of real knowledge.
. However if I’m starting to say “WTF is it doing now?!?!”, then yes, by turning 2 ADR’s off, it puts it into alternate law and nearly all your normal protections are turned off. It puts the pilot mostly back in charge of the thing and should act only from inputs from the pilot.The safety in turning off the ADR’s, is they’re reversible. So if you want to venture down the trouble shooting path and restore some normality to the system, it’s only the press of a button. The aircraft only needs 2 ADR’s to restore normal law.
I’m not type rated on the 330, only the 320, but essentially they are mostly the same. Perhaps the 330 is just slightly different in its flight control computers (PRIMS?), being a bit newer than the 320.
On the 320, and I assume it’s the same on the 330, Direct Law only occurs when you have selected gear down. So it’s normally only in those last few minutes of flight. And it’s a pain in the ass (in the sim at least) to fly, because the deflection of the flight controls is directly correlated to the control input from the side stick (it’s been a while since I’ve read this, so excuse me if it’s incorrect. Might be time to refresh my knowledge). Unlike Normal and Alternate Law, which still goes through the computers and deflects the controls an appropriate amount to meet the demand that we input through the side stick. So it will do it smoother and better. Unfortunately the side stick has zero connection to any flight control system, only a computer. So we have no feel at all.
When everything is running swimmingly, the Airbus is easy and quite nice to fly. When it starts going bad, it’s a pain in the ass. Almost as if Airbus couldn’t work out a better way to deal with abnormal situations, so it’s like a bunch of problems and checklists stacked on top of one another. Unlike the apparently easier way that Boeing has done it, whereby you have a problem, you run a checklist that deals with the situation from start to finish.
Last edited by morno; 6th Sep 2019 at 03:31.
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One of the things I’ve always kept in the back of my head after this and a few other incidents, as an absolute last resort, if the aircraft starts pitching itself around uncommanded, ADR 2&3 OFF, get the thing into alternate law. At least then the protections are turned off and I have a somewhat more controllable aircraft.
Why don’t you look up first and check if one has an amber light illuminated before you rush in and turn two good ones off.
3 ADRs off results in a world of hurt/BUSS.
And when you’re looking up switching 2&3 off the F/O loses his instruments.
So what happens if you turn 2 and 3 off and it turns out number 1 is stuffed.
Why don’t you look up first and check if one has an amber light illuminated before you rush in and turn two good ones off.
3 ADRs off results in a world of hurt/BUSS.
And when you’re looking up switching 2&3 off the F/O loses his instruments.
The problem is when none of the systems detect a fault, like in the QF72 case. But again, alternate law will stop the abrupt nose down pitching.
As for the FO losing his instruments, big whoop. There’s still a set on my side.
No Instruments on the FO side, or plunging into the ground, I know what I’d choose.
Finally Miles, it’s a procedure that is an absolute last resort when nothing else is working and still lets you fly the aircraft.
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There's an old well worn adage by computer engineers that still holds since computers were invented and it goes like this:
"We put the bugs in the system."
So why carp on about all the "what-if's"?
The software is never perfect - only tested to a common standard.
The plane is never perfect - only tested to a common standard.
Just as well Cpt Sullivan being ex US Mil had seen imperfection in aircraft before and was the smoothing interface between a smoking hole in the ground and a safe return for all.
And to think some people want to remove that filter out of the flying equation.
"We put the bugs in the system."
So why carp on about all the "what-if's"?
The software is never perfect - only tested to a common standard.
The plane is never perfect - only tested to a common standard.
Just as well Cpt Sullivan being ex US Mil had seen imperfection in aircraft before and was the smoothing interface between a smoking hole in the ground and a safe return for all.
And to think some people want to remove that filter out of the flying equation.
Your real aim is to stop the aircraft reacting to any dud data, and to do that you want a law change. Turning off the PRIMS will drop it to direct law, but all of the ADRs will still be available for you to try to resolve which is the bad source.
My AB time is only on the 380, so I’m just extrapolating from it to the other types.
Only half a speed-brake
The smaller kites have only 3 ADRs. In case of two delivering good data (identical by necessity), it is the corrupt third that will get flagged. No need to deactivate two, a single one - the bad apple - would suffice.
Once you’ve got control over the situation and worked out the faulty one, it can be isolated and HAL can be brought back to the negotiating table.
If you turn the two two good ones off you’ll work it out pretty quick. You’ve still got 5 mins of the ADR being off before it’s incapable of being reactivated.
Not to take anything away from the crew on the day but the good training and level headedness that ensured a successful outcome were not specific to military trained pilots only. They are the good skills and habits that all good pilots develop and hone over the course of their careers.
Last edited by dr dre; 7th Sep 2019 at 15:23.
Only half a speed-brake
The aim of the game is to turn two off ADRs for alternate law and thus preventing crazy flight protection inputs from HAL.
Once you’ve got control over the situation and worked out the faulty one, it can be isolated and HAL can be brought back to the negotiating table.
If you turn the two good ones off you’ll work it out pretty quick. You’ve still got 5 mins of the ADR being off before it’s incapable of being reactivated.
Once you’ve got control over the situation and worked out the faulty one, it can be isolated and HAL can be brought back to the negotiating table.
If you turn the two good ones off you’ll work it out pretty quick. You’ve still got 5 mins of the ADR being off before it’s incapable of being reactivated.
Think again, please. If you had two good ones (out of three) - which the previous post was so afraid of turning off - the HAL is happy an so is everyone onboard. 
The specific lifesaving trick discussed needs to be used only if TWO are wrong supplying incorrect but identical data, so the poor third correct bugger gets voted out of business. But then there's no fear of turning two good ones off, because you only had 1 to begin with.
The specific lifesaving trick discussed needs to be used only if TWO are wrong supplying incorrect but identical data, so the poor third correct bugger gets voted out of business. But then there's no fear of turning two good ones off, because you only had 1 to begin with.
