Could you add the size in inches (or mm) across the horizon, on the A/H part, so that I ( and others interested ) can adjust the scale on a monitor to be able to appreciate the instrument properly, as it might be viewed by a PF or PNF.
‐ The altitude indications are based on GPS data. Two amber dashes cover the last two digits because the GPS altitude is less accurate than the barometric altitude
‐ The vertical speed indication is no longer available.
Let me try to understand: static air data is deleted from the system? Is that what is going on in this mode?
So, once STALLED, there would not only seem to be no need for all NU from the THS, but that it would be highly dangerous to leave it there. With a continuous STALL warning, one would hope a 'smart' a/c would return the THS to neutral, and allow the Pilot to recover with elevators.
Since the speeds had returned, it becomes especially apparent (to the aircraft) full up THS is not a good thing? No alert, no lowering the THS,
So, you're advocating more automation? I'm not disagreeing here... I actually think all the information required to help the crew was available.
All ADR data is removed when ADRs are switched OFF.
With this BUSS option installed the AOA signal is fed into IR part of ADIRU, IR part is available even with Air Data P/B off. Don't know if more inputs are re-routed.
3hole, a few threads back, I think number 4, a gent who has taught in the A330 simulator related to us how some Unusual Attitude drills and recoveries required use of the trim wheel, manually, to get the pitch under control (in other than normal law, IIRC) in a suitable time frame. He wasn't sure if that was a "simism" or not.
Point?
There were or are some training drills that can be used to accustomize crews to using the trim wheel to control nose pitch in cases where the auto trim is either too slow or not helping redirect the elevators and THS where the pilot needs them. You could call the trim wheels a secondary flight control (Not sure if I am right about that) which means any rated pilot ought to know, like the flaps, when and how to use it.
And practice doing so.
Is it anywhere referenced to use it in this situation? I could only find the following references, where the mechanical trim is desscribed as standby system in case of autotrim not being availble.
Quote:
THS MECHANICAL CONTROL The mechanical pitch trim commmands are achieved by the handwheels in the cockpit and transmitted to the input shaft of the THS actuator. The THS mechanical control can be used :
- on ground, to trim the stabilizer when electrical control is not possible.
- in flight, as a standby system if automatic control (autotrim) is not available. (REF. LTTM)
Quote:
The control wheels are used in case of major failure (Direct Law or mechanical back-up) and have priority over any other command. (REF: FCTM)
Quote:
The purpose of the mechanical backup is to achieve all safety objectives in MMEL dispatch condition: To manage a temporary and total electrical loss, the temporary loss of five fly-by-wire computers, the loss of both elevators, or the total loss of ailerons and spoilers. It must be noted that it is very unlikely the mechanical backup will be used, due to the fly-by-wire architecture. For example, in case of electrical emergency configuration, or an all-engine flameout, alternate law remains available. In the unlikely event of such a failure, mechanical backup enables the PF to safely stabilize the aircraft, using the rudder and manual pitch trim, while reconfiguring the systems. (REF. FCTM)
Quote:
When automatic pitch trim is no longer available, the PFD indicates this with an amber USE MAN PITCH TRIM" message below the FMA. (Ref. FCTM)
Quote:
THS MECHANICAL CONTROL General The Trimmable Horizontal Stabilizer (THS) has a mechanical control system. You can use the mechanical control system on the ground to trim the stabilizer when electrical control is not possible. The mechanical control system is also used in flight as a standby system if automatic control is not available. The mechanical control transmits mechanical pitch-trim signals, put into the hand wheels in the cockpit, to the input shaft of the THS actuator. (REF. LTTM)
We know now that it might have helped to defuse the situation, how could the AF447 crew know? By not knowing the above references?
Why wouldn't I be advocating for more automation? Or a better fit between what exists and the crew? Isn't that what this is all about?
If this airframe thinks enough of itself to protect the Rudder from inadvertent and harsh deflection, why would it not also want to protect itself from a TRIM trapped STALL?
If more than 8 degrees Rudder is not available at certain speeds, why would -13 PU be available? This is the "disconnect" I see from the outset of this thread, some logic here, some logic there, but something short of a continuous path in all directions.
It can be explained, but excuse me, pulling out the book and trying to get task specific recurrent in these conditions is insanity.
Knowledge plus experience equals wisdom. Substitute the word intuitive for wisdom, and there you go. Nothing that can occur on this aircraft can be permitted to be anything short of fluid, intuitive, and absolutely resistant to failure.
And that is the goal for when things are difficult, and doable; to say this argument is justifiable at all when problems of a familiar nature are involved is frankly outrageous.
It would be so nice to simply say PE. That is not any longer acceptable if one also expects to take credit for a failure resistant a/c when faults are so readily apparent?
We read here from guys who dream this stuff and live it. But there are real people here, and when some assume a posture of haughty self satisfaction that makes my fur hurt. The aircraft has holes, fill them.
A33ZAB, Many thanks for the details of the ISIS.... looks and sounds very much like the SAARU in the triple 7. ...an everything-you-need-PFD-in-a-self-contained-box. Pop one of those in your little ragwing and you're home free!
Lyman.... Thanks for clarifying... One further comment, re: "If this airframe thinks enough of itself to protect the Rudder from inadvertent and harsh deflection, why would it not also want to protect itself from a TRIM trapped STALL?" Because it is NOT "trapped" at all and there is no risk of structural damage as there is with the rudder.
Speed is decreasing and as speed is decreasing, they don't see it and what does the THS do on FBW machine?: It tries to maintain flight path, so as speed is decreasing to maintain flight path the autotrim goes up to the limit, incidence is growing up to maintain flight path. On a Boeing, even in alternate law, you would have to trim as speed decrease to maintain flight path, it would alert you that something is wrong.
Autotrim will do exactly the same on a boeing if the automatics are trying to maintain a flight path (with speed decreasing). See Schipol 737 and similar accidents/incidents.
Many thanks for the details of the ISIS.... looks and sounds very much like the SAARU in the triple 7. ...
Minor correction:
-ISFD (Integrated Standby Flight Display) is the B. naming for ISIS.
-SAARU (Secondary Attitude Air data Reference Unit) is the "back-up" ADIRU of the777.
Quote:
an everything-you-need-PFD-in-a-self-contained-box. Pop one of those in your little ragwing and you're home free!
Exact! 1 standby instrument for whole fleet! A. thru Z.
"No risk of damage, as with the Rudder?" Methinks the reason the THS was not deployed in the climb, and the elevators were not allowed to grab too much at a time had to do with protections.
The a/c at the bottom is not Damage?
The Rudder could disintegrate and part the VS, no crash. The THS, at full NU does not risk damage to the a/c? What if they had recovered aero flight, and the THS remained at -13 in a steep and high speed dive. No risk of damage? What a ride. ?
No inference of applicability, but look at this. The Rudder on AA587 tore the VS off (That was at <250 knots). If 447 had been in a recovery from Stall, the THS couldn't take the Tail off? I wouldn't place a bet.
I concur, Increasing AOA is toward the bottom. Oriented this way to make the display read in a manner similar to airspeed. Note: There are no numbers on the display.
Shouldn't the note at the bottom right say: Red lower area corresponding to CAS < VLS
AF447 would have been at the bottom of the bottom red band while on its way down. Even three highly confused aviators would have understood their plight then. Well, lets hope so.
Maybe the "whooler" shouldn't have been eliminated, but I'm not at all sure that would have made any difference here.
It might have though...
I think a THS position trim clacker might well have alerted PNF to something going very awry in pitch much earlier and at least have glanced at the wheel or pointed the Captain to it immediately upon cockpit re-entry ?
.. even if PF himself was 'focused down a very narrow tunnel of perception' and would likely have been aurally blocking it out.
Speed is decreasing and as speed is decreasing, they don't see it and what does the THS do on FBW machine?: It tries to maintain flight path, so as speed is decreasing to maintain flight path the autotrim goes up to the limit, incidence is growing up to maintain flight path.
On a Boeing, even in alternate law, you would have to trim as speed decrease to maintain flight path, it would alert you that something is wrong.
Autotrim will do exactly the same on a boeing if the automatics are trying to maintain a flight path (with speed decreasing). See Schipol 737 and similar accidents/incidents.
Not a FBW issue, not an AB issue.
This is a drastic speed decrease, all the way down to a Stall condition, which is determined, and announced for 53 seconds by the "a/c's controls". Stall means fall !!!!
During these 53 seconds, of definite Stall Condition, determined by the a/c's computers, the THS went also under the a/c's computers control from -3 to -13 degree, which is MAX Nose Up, which is exactly the opposite of what in a Stall condition the pilot, or the computers should be commanding.
Personally, I would not consider this a FBW issue, in the sense of the FBW being a system in which the medium for transferring/passing bi-directionally control information is wire.
Is this really not an Issue??? if Boeing is doing to wrong thing, it is OK for AB to do the same?
Lyman.... Thanks for clarifying... One further comment, re: "If this airframe thinks enough of itself to protect the Rudder from inadvertent and harsh deflection, why would it not also want to protect itself from a TRIM trapped STALL?" Because it is NOT "trapped" at all and there is no risk of structural damage as there is with the rudder.
I dunno about structural damage for THS .. but this ended with a big structural damage (the entire plane and it's load) Maybe it's to understand Lyman prose as: Why the THS still full up .. when the plane know (seem's the pilots no) he is in a full stall Plane know this is a full stall .. plane know this is a full up THS deflection The two are contradictory Why not automatically reset the THS in a better position (with a warning to pilots) like it's a limitation for rudder deflection in particular situations ?
So, once STALLED, there would not only seem to be no need for all NU from the THS, .... With a continuous STALL warning, one would hope a 'smart' a/c would return the THS to neutral, and allow the Pilot to recover with elevators.
So, you're advocating more automation? I'm not disagreeing here... I actually think all the information required to help the crew was available.
It's not "more automation". It is rather "right automation"!!!
All of the AOA information to avoid this crash are present in every modern Airbus aircraft, as standard equipment. In addition to the stall warning and the VLS/Alpha Prot, Alpha max scale on the left side of the PFD, there is an even better, direct measure of AOA, even though it does not come from the AOA installed on the aircraft (3 on the 320 series).
The problem is, no one is trained to use it.
What is AOA? It is the angular difference between the relative wind and the longitudinal axis of the aircraft (chord of the wing, more specifically). In lay-mans terms (I am one), it is the difference between where the airplane is pointed, and where it is going, about the lateral axis.
Call up the "bird". With the wings level, the AOA is the vertical distance from the pitch bars (where the aircraft is pointed), and the "bird" (where the aircraft is actually going). Non-wings level, you visually drop a perpendicular from the plane of the pitch bars to the bird. That distance, measured on the PFD, is your AOA, and would have prevented this crash.
I know some engineer (I am one also) will say that this AOA measurement is not "perfect", but neither is an AOA gauge. Not even close. Just as IVSI is more useful than a pure VSI, this IRU based measurement is actually more user friendly to the pilot, more reliable, and "cleaner". And it is EXACTLY where the pilot is staring to control the aircraft, there is no other "scan" to learn.
On a 320 series, cruise is usually 2-3 degrees up, green dot, S, and F speed are 7-8, Stall warning (in alternate law in the sim) comes on at 10-12 degrees with the stall happening a bit above that. In level flight this is the "pitch attitude". In non-level flight, this is the perpendicular distance from the pitch bars to the bird. Icing doesn't affect the IRU's and there are 3 of them on the 320.
