If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.
Announcement
Collapse
No announcement yet.
Edelweiss almost touches down again immediately after lift-off
Remember AoA may increase even with pitch remaining unchanged or even decreasing. AoA and pitch are related but not correlated. AoA = pitch - climb gradient.
So you're saying if the climb gradient dropped off, Alpha max pitch would be reduced and the FBW would subsequently cause the pitch reduction? It doesn't look like much climb is occurring at all before this happens. But maybe. Again, I expect that this is complicated by the blending aspect of the flight control laws.
It still looks to me like a low energy (wrong v-speeds) takeoff followed by a manual input possibly following the SRS, a SPEED warning (if not yet in Normal Law) or just instinctive reaction to the lack of climb performance.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
So you're saying if the climb gradient dropped off, Alpha max pitch would be reduced and the FBW would subsequently cause the pitch reduction?
Not sure what you mean with "Alpha max pitch would be reduced", I would just say that alpha max (the AoA, not any particular pitch) would be achieved or exceeded and then yes, the FBW would subsequently command an AoA reduction which in this case would most likely result in a pitch reduction , in normal law.
I am trying to be careful with my selection of words. I explained in my old stall rant thread how a pilot can reduce the AoA (which involves "pushing down" or, more accurately, reducing back pressure on the control column) while at the same time the climb gradient, climb rate and pitch all increase. The reason why this can work is also the basic reason why the old and very inadequate approach to stall recovery procedure (TOGA and pitch 10 deg) still worked most of the times.
Again, I expect that this is complicated by the blending aspect of the flight control laws.
Yeah, I don't know either.
It still looks to me like a low energy (wrong v-speeds) takeoff followed by a manual input possibly following the SRS, a SPEED warning (if not yet in Normal Law) or just instinctive reaction to the lack of climb performance.
I don't what triggered it, but I also suspect manual input.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
I don't see any nose down command.
After unstick upon reaching the target pitch attitude you can usually fully release the back pressure on the sidestick on the FWB Airbuses (with the correct stab trim setting).
That's exactly what what happened here. It took more than 1 second after the elevator was in the neutral position until the nose suddenly started dropping without any pilot input or any visible elevator deflection.
Maybe due to wake turbulence from the preceeding plane on the crossing runway less than a minute ago.
Not sure what you mean with "Alpha max pitch would be reduced"
I meant the pitch equating to Alpha Max in that moment, i.e. the pitch limit. In other words:
Originally posted by Gabriel
I would just say that alpha max would be achieved or exceeded and then yes, the FBW would subsequently command an AoA reduction which in this case would most likely result in a pitch reduction , in normal law.
I don't see any nose down command.
After unstick upon reaching the target pitch attitude you can usually fully release the back pressure on the sidestick on the FWB Airbuses (with the correct stab trim setting).
That's exactly what what happened here. It took more than 1 second after the elevator was in the neutral position until the nose suddenly started dropping without any pilot input or any visible elevator deflection.
Maybe due to wake turbulence from the preceeding plane on the crossing runway less than a minute ago.
Don’t you need to achieve around 100’ altitude before the translation to autotrim (Normal Law) has occurred?
Don't know about the A340, but on the A320 the transition from gnd to flt mode occurs 5sec (pitch) and 0.5sec (roll) after unstick if the pitch attitude is higher than +8°.
The 100ft apply only during autoland, (50ft during manual landing).
Don't know about the A340, but on the A320 the transition from gnd to flt mode occurs 5sec (pitch) and 0.5sec (roll) after unstick if the pitch attitude is higher than +8°.
The 100ft apply only during autoland, (50ft during manual landing).
Alpha floor on the A320 at Conf 1+2 is >15°.
How does sidestick control law apply to autoland? Anyway, this seems to occur within 5 seconds after unstick. What happens if the pilot releases the stick before then?
I am not seeing where watching the nose or AI or flight director and keeping hands on controls BECAUSE THIS IS A SORT OF CRITICAL FLIGHT PHASE is part of said discussion.
More of a highly-accurate regurgitation of cryptic procedures.
JMAHO.
Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
I am not seeing where watching the nose or AI or flight director and keeping hands on controls BECAUSE THIS IS A SORT OF CRITICAL FLIGHT PHASE is part of said discussion
Because, as always, we discuss what might have happened (and why) and you focus on what should have happened based upon your Cessna proficiency.
Don't know about the A340, but on the A320 the transition from gnd to flt mode occurs 5sec (pitch) and 0.5sec (roll) after unstick if the pitch attitude is higher than +8°.
The 100ft apply only during autoland, (50ft during manual landing).
Alpha floor on the A320 at Conf 1+2 is >15°.
That's a good data point. I don't think that the plane ever got close to 15° so unless there was a huge updraft that increased that AoA way beyond the pitch angle, the plane should have never reached alpha floor.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
I am not seeing where watching the nose or AI or flight director and keeping hands on controls BECAUSE THIS IS A SORT OF CRITICAL FLIGHT PHASE is part of said discussion.
More of a highly-accurate regurgitation of cryptic procedures.
JMAHO.
I an Airbus plane in direct law, if the FBW decides to lower the nose because you reached alpha max, what you do with the sidestick is not really important. The plane will do what FBW says, not what the pilot right or wrong wants. And this feature has already saved lives.
Note the if.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
For your endless listings of possibilities, you can’t come up with a mechanism where airspeed loss results in an increase in AOA?
I can (indirectly, eventually, with a delay, and temporarily... unless something else other than the loss of airspeed happens), but you raised the exception so I want to know what you have in mind.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
We process personal data about users of our site, through the use of cookies and other technologies, to deliver our services, personalize advertising, and to analyze site activity. We may share certain information about our users with our advertising and analytics partners. For additional details, refer to our Privacy Policy.
By clicking "I AGREE" below, you agree to our Privacy Policy and our personal data processing and cookie practices as described therein. You also acknowledge that this forum may be hosted outside your country and you consent to the collection, storage, and processing of your data in the country where this forum is hosted.
Tweet
Comment