Originally Posted by Machinbird
Do that in roll direct and I suspect you will learn gentleness, and there might even be an additional mess in the cockpit.
Alternate1 and Alternate2 laws might work similarly in pitch, but they bear no resemblance in roll.
What relevance it has to AF447? For Finnegan's sake it didn't crash in spiral dive or rapid roll to ocean but in upright stall! That's what happens when you try to pull the aeroplane where she just can't go perfomancewise.
Originally Posted by gums
So if the FCS doesn't have an absolute AoA limit, then at least show the pilot the stall AoA.
Herein lies the rub; on 330 it is very much mach and configuration dependent. No airspeed - no mach - no meaningful alpha limit.
Originally Posted by gums
If you want some kinda "magenta line" to helpsteering
Who gives a rat's stern about my wishes? I have commented on the way I performed visual (no steering cue) and CAT3a (cue required) approaches using head-up guidance system I.A.W. what my employer expected of me.
Originally Posted by gums
We had one important backup mode - Standby Gains, which is extremely relevant to our discussions here the last three years. If air data was deemed unreliable the FCS used a fixed value for "gains".
Thanks, I stand corrected: Viper had degradation modes, different in details but principally similar to Airbus FCS laws.
Originally Posted by gums
We did not worry about a myriad of alpha stuff
Neither need Airbus pilots as long as they don't bust the lift limit.
Originally Posted by gums
Both limited the jet to stall AoA ( roughly).
...on aeroplane supported by cropped delta of relatively low aspect ratio i.e. with far larger useful AoA span (per design and intended use) than moderately swept, high aspect ratio, supercritical, cruise optimized wing of 330.
Could still run outta energy in a steep climb and momentum would allow the jet to exceed the limts because the flight controls could not react quickly enough ( very hard for our jet, and even more so for the heavies, IMHO)
It's hard to climb heavy steeply but if combat aircraft controls can not react quickly enough, what chances have the civil transport ones?
Originally Posted by gums
Otherwise, much of my views could be misunderstood.
As someone who was using HUD in airliner for a while I agree it is quite useful but I don't think it would have saved the AF447.
Originally Posted by BOAC
not sure what 'vent' means here
Typo for "went".
Originally Posted by BOAC
it does appear that the designers forgot this very important 'trigonometry' and that a jet in a fully developed stall can and did, in fact ?'vent'? below 60kts (IAS).
20/20 hindsight. No one has proven before that it can.
Originally Posted by Owain Glyndwr
With hindsight the logic is faulty, but I don't see any need to alter the logic governing validity of AoA signals which might well bring on other problems we know nothing of. Instead I would propose a change of stall warning logic so that if triggered by a valid AoA signal it should stay latched on until it received another valid AoA signal that stall conditions were a thing of the past.
Spot on. Instead of introducing WoW signal into stall warning logic and creating another possible point of failure, not completely dissimilar to one affecting Spanair 5022, this one could be done by simple software code change. However...
Originally Posted by Owain Glyndwr
That would have avoided the confusion found in the AF447 cockpit for a minimal change to the aircraft systems
...if there was confusion about everything else, at least actions on the stick show that CM2 firmly believed that stall warning can be resolved by pulling.
Originally Posted by BOAC
However, why WoW was 'abandoned' I do not know
It was never there. If you already must have speed and mach input to calculate critical angle of attack, it makes sense to simplify it by just putting in a couple of lines of code that cut alpha readouts at speeds that are completely unsustainable.
Originally Posted by BOAC
but I cannot see why posters are going on about 'non-swivelling pitot tubes'
I am just mocking the inability of some to understand pitot tubes reliably measure only total pressure resulting from airstream approximately parallel to aeroplane's longitudinal axis. Such a design has been with us since they have first been attached to aeroplane and everyone except a couple of PPRUNers finds it fine.
Originally Posted by BOAC
Surely we all understand why the IAS reading was invalid?
Those who think IAS reading below 60 kt was really invalid - not.
Originally Posted by Dozy Wannabe
In response to that, Airbus reduced the required pressure on the WoW sensors
I don't recall anything about this. What I remember is that post-Warsaw spoiler logic on 320 was changed inasmuch selecting reverse cracked open the spoilers thereby killing a bit of lift and compressing both struts. The rest remained unchanged and full deployment was still only available when both MLG WOWs detected landing. Way the Airbus spoilers designed, WOW signal is a must to prevent airborne activation of ground spoilers.
Originally Posted by Dozy Wannabe
OG, I'm almost certain you're correct in that the <60kts AoA NCD flag has nothing to do with determining air/ground mode - it's purely an attempt to enforce the AoA vane manufacturer's specified limitation of minimum 60kts airspeed for valid data, and prevent junk data from being used in FCS calculations.
Interesting... I'd like to hear more about about junk data when Airbus flies slower than 60 kt, I mean why is this problem not solved yet by introducing the alpha probe that can work reliably below 60 kt?
Originally Posted by gums
Basic airmanship and flying skills, ya think?
Yes.