Airbus A 321 Managed/Open DES with no A/THR.
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MD80rookie
I don't have to try. I have seen it and already know. If you had used the correct terminology this discussion was not required. What you meant was that the aircraft will enter steep descent to capture the speed. Isn't that what it is supposed to do? But it will still do it at -1G and not violently. While reducing thrust if you ensure that negative large trend vector does not develop then the situation is no different than with ATHR on. And I never heard this phrase Toulouse style protection. Steep descent and high negative G are not same.
I don't have to try. I have seen it and already know. If you had used the correct terminology this discussion was not required. What you meant was that the aircraft will enter steep descent to capture the speed. Isn't that what it is supposed to do? But it will still do it at -1G and not violently. While reducing thrust if you ensure that negative large trend vector does not develop then the situation is no different than with ATHR on. And I never heard this phrase Toulouse style protection. Steep descent and high negative G are not same.
Last edited by vilas; 9th Apr 2015 at 05:16.
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Too bad the new FCOM versions did away with the FCBulletins.
But if you still got access to them, a bulletin states that, with the FADEC working, the fastest rate of thrust reduction the FADEC would allow is 1% PER SECOND.
Meaning, even if you close the thrust levers at the speed of light, thrust reduction would still go no faster than 1% per second.
That's why I don't get all this concern re Open Des.
But if you still got access to them, a bulletin states that, with the FADEC working, the fastest rate of thrust reduction the FADEC would allow is 1% PER SECOND.
Meaning, even if you close the thrust levers at the speed of light, thrust reduction would still go no faster than 1% per second.
That's why I don't get all this concern re Open Des.
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Regarding the "violent" pitching.
I have seen (from the jump seat) an A330, fully autopilot coupled, pitch itself down into its own "pitch attitude protection" limit in OP DES. This was due to the captain pulling open descent at Mach .82 at 41,000 feet and descending from a 100-ish knot headwind into a 50-ish knot tailwind through a fairly tight shear layer. The thing just couldn't catch the speed target, as it kept creeping up the tape while the actual airspeed was affected by the tailwind shear.
The vertical rate got to about 7000 FPM (indicator turns yellow) down within a matter of about 10 seconds, and the pitch dropped below 12 degrees. As the plane went thru another shear layer, the pitch touched the green hash marks and started to immediately rise. This of course made the speed drop, causing the airplane to pitch down again, etc etc etc.
The whole process here took less than 20 seconds. It took the operating crew that long to respond to my corrective callout. Why? They were busy looking out the window for traffic to follow, while complying with a descent clearance. The autopilot was so amazingly smooth that they simply did not notice until it was diving like a homesick brick. Nighttime with no moon, no horizon outside to reference.
Both of your comments, in other words are true.
Moral? In normal situations don't pull open descent at FL410 if you are descending into a tailwind / quickly weakening headwind.
I have seen (from the jump seat) an A330, fully autopilot coupled, pitch itself down into its own "pitch attitude protection" limit in OP DES. This was due to the captain pulling open descent at Mach .82 at 41,000 feet and descending from a 100-ish knot headwind into a 50-ish knot tailwind through a fairly tight shear layer. The thing just couldn't catch the speed target, as it kept creeping up the tape while the actual airspeed was affected by the tailwind shear.
The vertical rate got to about 7000 FPM (indicator turns yellow) down within a matter of about 10 seconds, and the pitch dropped below 12 degrees. As the plane went thru another shear layer, the pitch touched the green hash marks and started to immediately rise. This of course made the speed drop, causing the airplane to pitch down again, etc etc etc.
The whole process here took less than 20 seconds. It took the operating crew that long to respond to my corrective callout. Why? They were busy looking out the window for traffic to follow, while complying with a descent clearance. The autopilot was so amazingly smooth that they simply did not notice until it was diving like a homesick brick. Nighttime with no moon, no horizon outside to reference.
Both of your comments, in other words are true.
Moral? In normal situations don't pull open descent at FL410 if you are descending into a tailwind / quickly weakening headwind.
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It is not forbidden to adjust the speed in such a way that your pitch and ROD will stay within acceptable limits or as you suggest revert to V/S. The point is that whatever the crew decides, the airplane flight path must be monitored. Having 2 pilots looking out the window means that nobody is flying the airplane.
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Moral? In normal situations don't pull open descent at FL410 if you are descending into a tailwind / quickly weakening headwind.
Firstly when 100kts. head wind turns into 50kts. tail wind it is not normal. It is a serious wind shear and what happened is not unusual. It could have been worse as it could have tripped the auto pilot or triggered alpha protection. It has happened before. So open descent is not the cause. Secondly the original topic by MD80 was manually reducing the thrust quickly in open descent, which obviously one shouldn't and aircraft pitching down steeply to regain lost speed which it should. If the thrust is reduced as auto thrust does then there is no problem. My point is AB FBW may pitch down to whatever degrees but it will do so at 1G, you can call it a steep descent and want to avoid it, that is fine. Toulouse style protections is another mystery, may be he is repeating a phrase by one of his experienced Airbus sceptical instructors because by his own admission he is a neophyte to the bus.
Firstly when 100kts. head wind turns into 50kts. tail wind it is not normal. It is a serious wind shear and what happened is not unusual. It could have been worse as it could have tripped the auto pilot or triggered alpha protection. It has happened before. So open descent is not the cause. Secondly the original topic by MD80 was manually reducing the thrust quickly in open descent, which obviously one shouldn't and aircraft pitching down steeply to regain lost speed which it should. If the thrust is reduced as auto thrust does then there is no problem. My point is AB FBW may pitch down to whatever degrees but it will do so at 1G, you can call it a steep descent and want to avoid it, that is fine. Toulouse style protections is another mystery, may be he is repeating a phrase by one of his experienced Airbus sceptical instructors because by his own admission he is a neophyte to the bus.
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All true. I can only assume that slamming the throttles to idle in a similar situation would make it even worse.
Not a typical wind to be sure, but have seen it come pretty close more than once descending out of a jet core landing in the tropical Pacific. Shear layer about 5-10,000 feet thick, well below the high tropopause typical of the latitude. Hence "chasing the Mach" in the descent. Seen the "open descent Mach dive" more than once, usually with inexperienced crews. They usually catch it right away.
A managed descent in managed speed, with a good wind profile inserted, makes the whole thing a total non-issue.
Not a typical wind to be sure, but have seen it come pretty close more than once descending out of a jet core landing in the tropical Pacific. Shear layer about 5-10,000 feet thick, well below the high tropopause typical of the latitude. Hence "chasing the Mach" in the descent. Seen the "open descent Mach dive" more than once, usually with inexperienced crews. They usually catch it right away.
A managed descent in managed speed, with a good wind profile inserted, makes the whole thing a total non-issue.
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MD-80 Rocks! Stuff Open Climb!!
On the MD-80 we sometimes flew high at the edge of the aircraft’s performance envelope (in those days the performance tables and aircraft weight were not so exact) and encountered buffeting in turns with more than 10° bank.
If you entered the top layer of a thunderstorm in such conditions, you could lose lift rapidly and disappear in the cloud.
In 2006 I flew a heavy A321-200 above its maximum recommended flightlevel to get over a thunderstorm.
With open climb mode I anticipated a slow climb.
Checking the primary flight display it showed an unexpected ROC of 3,500ft/min with rapidly decreasing airspeed.
What happened?
The computer extrapolated that beyond normal range the aircraft would not be able to fly high and fast simultaneously, and reduced speed to M.73 by itself.
To get there from M.79 it pitched up to a ROC irrationally high in thin air.
It would have meant stalling and falling into an active storm.
The A321 software may be updated to avoid this condition but it shows the vigilance needed at the edge of its performance envelope.
A computer-controlled aircraft is still only an aerodynamic machine.
If you entered the top layer of a thunderstorm in such conditions, you could lose lift rapidly and disappear in the cloud.
In 2006 I flew a heavy A321-200 above its maximum recommended flightlevel to get over a thunderstorm.
With open climb mode I anticipated a slow climb.
Checking the primary flight display it showed an unexpected ROC of 3,500ft/min with rapidly decreasing airspeed.
What happened?
The computer extrapolated that beyond normal range the aircraft would not be able to fly high and fast simultaneously, and reduced speed to M.73 by itself.
To get there from M.79 it pitched up to a ROC irrationally high in thin air.
It would have meant stalling and falling into an active storm.
The A321 software may be updated to avoid this condition but it shows the vigilance needed at the edge of its performance envelope.
A computer-controlled aircraft is still only an aerodynamic machine.
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Winner rather than the technical aspect of the airplane I would consider the fact that climbing above REC MAX to get over a thunderstorm can lead to some serious headaches.
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I'm pretty sure it didn't change the speed to increase the climb rate.
Speed is only changed to adjust flight path in the descent.
Possibly the aircraft entered an area of significant temperature difference and the econ climb speed changed.
Speed is only changed to adjust flight path in the descent.
Possibly the aircraft entered an area of significant temperature difference and the econ climb speed changed.
Errr, Winnerhofer. Why were you trying to fly OVER a thunderstorm at your level????
And why did you talk about flying THROUGH the top of a thunderstorm in a previous post???
Dude, you must go AROUND thunderstorms, and stay at least 20 nm away from them, and on the upwind side. They are bloody dangerous.
Perhaps you should dig out your meterology notes and refresh your memory.
And why did you talk about flying THROUGH the top of a thunderstorm in a previous post???
Dude, you must go AROUND thunderstorms, and stay at least 20 nm away from them, and on the upwind side. They are bloody dangerous.
Perhaps you should dig out your meterology notes and refresh your memory.
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winnehofer
I am glad you are here to speak with us today.
Exceeding REC MAX in any situation is foolish and unprofessional.
To do so on top of an active storm is gravely ignorant.
Above and below storms are both very dangerous places, upwind is the place to operate.
I am glad you are here to speak with us today.
Exceeding REC MAX in any situation is foolish and unprofessional.
To do so on top of an active storm is gravely ignorant.
Above and below storms are both very dangerous places, upwind is the place to operate.
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47 T seem very light but ok. Pitch is LF in the airbus during flight in normal law. I never tried your technique but what I suspect is that when you immediately cut the power the pitch will adjust gradually. Initially leading to a slight underspeed and then with a high ROD catching up with the speed and probably leading to a slight overspeed again. You sometimes see it in an open climb as well. Very high roc to maintain the speed and then you lose all your v/s because it now underspeeds by >10kts. At high altitude in climb i prefer use of V/S exactly to avoid an underspeed due to large vsi changes
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Also, if descending from high level with a Mach in OP DES the speed will increase as a natural function of Mach vs airspeed.
I have seen >7000'/min descent often in A318, all normal if a little unsettling.
I have seen >7000'/min descent often in A318, all normal if a little unsettling.
