Gentlemen, thank you for quite useful discussion on AoA gauges. I don't have definite opinion on the matter of necessity of equipping the airliners with them and anyway I spent about 150 hours warming up the front right seat on A320 of mid 200s S/N vintage, that had AoA indicators; small, round, analog, mechanical, pretty devoid of markings on dial face (just some units which might have been degrees or indices or whatever, no bugs or typical AoA markings) and set outboard of PFDs. There was description of the way system works in our manuals but there was not a single procedure based upon them. They did provide some inflight entertainment, especially in CONF 1 as they were not config compensated.
Nevertheless, I am not convinced that AoA gauge would have been necessary or even helpful to get AF447 crew out of their predicament as 1) UAS was never recognized and prescribed actions were never initiated 2) 36 other crews managed to do just fine under similar circumstances just relying on attitude and power 3) CVR and FDR don't paint a pretty picture; it seems that both pilots got utterly confused simultaneously and did not realize what was going on. In my opinion the IFR pilot that is unable comprehend the implication of the attitude he's putting the aeroplane into and does not realize what is that synthetic voice shouting "STALL STALL" trying to convey has zero chance of understanding what AoA gauge is telling him.
Originally Posted by Hazelnuts39
AFAIK Valpha max is the '1g' stall speed and is not g-sensitive.
No. The wording of the manual does leave many possibilities for creative misinterpretation but I am pretty sure I've spent about a dozen hours overhead Lambourne, watching it creep up during turns.
Another misconception is that low speed cues are g-sensitive. They are not. They are alpha sensitive, just as the Cl is, therefore change of AoA will simultaneously change low speed cue position and wing lift which leads to Nz (colloquially: G) change. Applying
post hoc, ergo propter hoc one can come to fallacious conclusion you need inertial source to drive low speed cue.
Originally Posted by HazelNuts39
The gust velocities that can be derived from the DFDR data were posted here.
The meteorological analysis by Tim Vasquez points to the possibility of a gust velocity of 23 m/s = 75.5 ft/s = 4527 ft/min based on the atmospheric temperature profile obtained in a radiosonde ascent from Fernando de Noronhas.
Valiant effort, but if you tried to prove there was significant turbulence that has affected the flight, you needed not bothered. Interim 3, page 42 shows difference between control induced Nz and measured one - which is indication of turbulence. +/- 0.4 G is moderate. Also very short lived.
Originally Posted by DozyWannabe
Careful TD, your source is not exactly known for impartiality.
...but their PPS has sinister looking, dark figure of pilot on almost every page. Perchance compensating slight and not so slight distortions of facts with stage effects?
DGAC and EASA did know about far more than just AF's 9 pitot blockages. Consideration was given to changing SB regarding the replacement of Thales probes with Goodrich ones to AD somewhere in late 2008 but change was not effected. If it suits you, you may believe it to be a conspiracy. However, I have no problems seeing how the already more than twenty incidents that ended uneventfully could lead EASA to belief that every crew knows what to do when loosing IAS.
While Goodrich pitots perform far better than Thales, they are not perfectly immune from same type of clogging and their installation will not absolve the pilots from obligation to recognize UAS, know appropriate procedures for it and apply them. Law of self-preservation demands so.
Originally Posted by gums
Seems the commercial airline folks do not want to implement a wide field-of-view HUD, but I can tell you that the sucker is invaluable in bad weather.
Actually, for last three years, I have been earnin' my daily bread by staring through wide angle Head-up Guidance System grafted onto my Q400. It's a wonderful thing. It has flight path vector. It has inertially driven energy caret so you know you'll lose or gain speed before IAS makes a slightest movement. It has speed error column on FPV so you don't need as much as look left across the HUD to check your speed, let alone perform quick glances inside the cockpit to check ASI on primary flight display while maneuvering manually during final approach. It's not direct measure or readout, but vertical distance between aeroplane reference and your FPV represents your AoA. There are pitch limit indicators preventing you from whacking your tail on takeoff rotation, unusual attitude recovery help, flight path limit showing you margin to stickshaker, TCAS RA flightpath (instead of VSI) guidance and lots of other neat stuff.
Is there a downside to it? Of course there is; it's too good and too easy to use and aeroplane can be dispatched with HUD or IRS failed so you are back to classic instruments scan. It's easy to let your classic scan get rusty so I make a habit of using HUD only on about half of the flights, to stay in shape.
Did my company buy this neat gizmo to make my life easier? Of course not. Our base gets pretty foggy in winter and HGS enables us to perform low visibility approaches down to 200m RVR and 50 ft DH, rather than 300m/100ft we had before HGS. It was cheaper to install HGS then to develop autoland capable autopilot cum autotorque.