Amazing amount of material posted in the last few days. I was out of town,
and so did not FOD the thread.
A thought on AoA probes and 60 knots.
Originally Posted by a former flying squid
My personal experience with the US Navy peg, cone and vane type AOA sensors is that they would come alive in a definite breeze, perhaps 10 knots.
A vane type that needed 60 knots to be reliable would be a sticky one in my book.
Aye, but here is a thought: if the mission designed approach and takeoff speeds are typically 150 kts and more, maybe the design criterion can accept them not being as swift as the nautical brand at less than half of the operating speeds?
Two thoughts I see bubbling up, the answers to which are not clear to me.
Once they were in Abnormal Attitude Law, the Stab (THS) Trim remained where it was last. (In this case full nose up)
From the "flight & laws" link above, if in Direct Law the pilots will see "USE MAN PITCH TRIM" on the PFD. Is that also the case in Abnormal Law?
Is there an unambiguous answer to those nested questions?
What I don't see from the latest BEA narrative is how many attempts to move the stick down, or move the nose down, were in play. Two are mentioned. Was that all?
This related to an earlier observation: a continuing attempt to move the stick down (though they mention some instances of stick movement toward nose down, the event flow is hard to discern) to unstall also runs into temporal distortion and its effects on pilots handling upsets.
Many pages ago, one of our posters pointed out that he was suprised to learn how long it takes for his inputs to unstall one of the big jets. With that in mind, was the crew in AF 447 (if and when they finally figured out "we are stalled!") not aware of how long it takes to get the AoA to start increasing again for the position they were in when "we are stalled and falling" became evident?
We may never know. CVR might tell.
Aside/musing. (Not sure how applicable this is to the mishap underdiscussion).
FWIW, from a pilot, but not an Airbuss 330 pilot.
If I command the nose down or up with the stick, and the nose does not go up or down, there is something horribly wrong, and I am by definition, in a condition known as
out of controlled flight.
I am using a very simple definition of out of controlled flight.
You are in the aircraft, you make inputs with the stick and rudder and throttle, and the plane does not respond as you command it to. (Or, as you expect it to). Recovering from out of controlled flight is a skill set that relies on the flight controls working as they are known (or designed) to work in response to your inputs, so you have to get to that state. As an emergency or recovery procedure, out of controlled flight recovery means taking a set of steps that gets you to the point where the flight controls respond to your inputs to go up, down, left, right, etecetera. It often takes time and altitude to get through those steps.
From a pilot and human factors point of view, and the flight regime the cockpit crew found temselves in ...
Given the flight regime they were in, and considering the likely concerns about not overspeeding or going to fast in turbulent air present due to envirnonemt, the crew was in the condition for a surprise upset:
You don't expect to be stalled, which means you have to spend "x" seconds (or fractions thereof) overcoming the
denial stage, and getting to
the action stage. (Responding to your training and knowledge of your equipment and situation).
That some of the cues were either ambiguous or at odds with previous training looks to have led to counterintuitive responses ... but we don't know what PF was seeing.
Further thought on aerodynamics and degree of stall.
If the answer to the two nested questions is "no visual alert" and "yes, you need to take over manually to get THS to work the nose attitude to your advantage" then there is a possible training improvement to be harvested.
To the question of ineffectiveness of elevators, as aircraft speed decreases, due to V^2 ... the slower you are in the airstream, the more pronounced the effect of THS overwhelming the elevators in pitch control. (I hadn't considered the masking due to high pitch/AoA). Does this make sense, in terms of me understanding that characteristic of the flight controls?
The deeper into stall you go, particularly if THS running most of the way up was a factor, the harder it is to unstall with your stick control.
Maybe my math on that is off, and it washes out and is a linear relationship.
Yes, pitch and power brigade, the basics are important.