Whats the logic here?
Joined: Nov 1999
Aviation Qualifications: ATPL
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From: UK
As an aside, I once landed an A320 or 321 which had a reverser locked out. Our SOP in this situation was to put both thrust levers into reverse rather than just the one that was working.
However, something went wrong and when I applied full reverse to both engines, the good one went into full reverse but the faulty one went into FORWARD thrust at whatever N1 full reverse is. As a result the aircraft suddenly pitched up, lifting the nosewheel off the ground and yawed. This was completely unexpected, but I instinctively controlled the aircraft with rudder and elevator, and cancelled reverse thrust and brought it to a safe stop.
However, something went wrong and when I applied full reverse to both engines, the good one went into full reverse but the faulty one went into FORWARD thrust at whatever N1 full reverse is. As a result the aircraft suddenly pitched up, lifting the nosewheel off the ground and yawed. This was completely unexpected, but I instinctively controlled the aircraft with rudder and elevator, and cancelled reverse thrust and brought it to a safe stop.
Last edited by Uplinker; 30th December 2017 at 14:06.
Joined: Feb 2009
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From: Seattle
Why use thrust reverse if inop on one side?
Please excuse my lack of pilot training experience as I am a career flight controls engineer, but not a pilot. It seems to me that having thrust reverse inoperative on one engine of a twin would be good reason to avoid thrust reverse usage all together due the the known yaw asymmetry that will cause.
It is my understanding that landing field length considerations do not count on the availability of thrust reverse and thus planning not to use it would not impact the performance decision as to whether a particular field is long enough given airplane type and weight. Am I wrong here? Is credit taken for availability of thrust reverse when calculating required landing field length?
Always looking to learn more.
It is my understanding that landing field length considerations do not count on the availability of thrust reverse and thus planning not to use it would not impact the performance decision as to whether a particular field is long enough given airplane type and weight. Am I wrong here? Is credit taken for availability of thrust reverse when calculating required landing field length?
Always looking to learn more.
Joined: Jan 2014
Posts: 720
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From: N5109.2W10.5
Hi
FCeng84,
Have a quick look at:
https://aviation-safety.net/database...?id=20070717-0
FCeng84,
It seems to me that having thrust reverse inoperative on one engine of a twin would be good reason to avoid thrust reverse usage all together due the the known yaw asymmetry that will cause.
https://aviation-safety.net/database...?id=20070717-0
Joined: Feb 2009
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From: Seattle
Asymmetric throttle lever control during landing risky?
Goldenrivett - thanks for posting that link, I found it to be an interesting read about a sad event that should have been preventable.
It seems to me that any procedure that calls for asymmetric control of the throttle levers during landing introduces a safety risk. In the event referenced, one lever was left commanding significant forward thrust while the other was moved to idle and then to reverse. Would it not be better to have a procedure that calls for both throttle levers being retarded to idle with reverse thrust being commanded on both throttle levers at pilot discretion provided there is not a known reverser fault?
There is mention in the report of a 55 meter landing distance penalty related to how the throttles are used during landing, but it is not clear if that would mean that longer runway is required for landing with no usage of reverse vs. landing with one of the reversers known to be inop but planning to use the other.
Having a system where moving the throttle lever to command reverser can result in increased forward thrust if the reverser fails to deploy seems to me to be a major design error. There should be interlocks such that engine spool up for increased reverser action will not happen unless the reverser has properly deployed.
I am still left with the question as to whether or not landing field length requirement determination takes credit for availability and usage of reverse thrust.
It seems to me that any procedure that calls for asymmetric control of the throttle levers during landing introduces a safety risk. In the event referenced, one lever was left commanding significant forward thrust while the other was moved to idle and then to reverse. Would it not be better to have a procedure that calls for both throttle levers being retarded to idle with reverse thrust being commanded on both throttle levers at pilot discretion provided there is not a known reverser fault?
There is mention in the report of a 55 meter landing distance penalty related to how the throttles are used during landing, but it is not clear if that would mean that longer runway is required for landing with no usage of reverse vs. landing with one of the reversers known to be inop but planning to use the other.
Having a system where moving the throttle lever to command reverser can result in increased forward thrust if the reverser fails to deploy seems to me to be a major design error. There should be interlocks such that engine spool up for increased reverser action will not happen unless the reverser has properly deployed.
I am still left with the question as to whether or not landing field length requirement determination takes credit for availability and usage of reverse thrust.
Joined: Mar 2006
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From: USA
Stopping distance does not take credit for reverse thrust. If I'm not mistaken, the only time reverse thrust is accounted for is a rejected takeoff an a wet runway [25.109(f)], with the good engine at idle reverse. Standing by to be corrected if I'm wrong.
That said, if I'm landing with an inoperative reverser, I'll select idle reverse on the god side. The asymmetrical force isn't that significant at idle.
That said, if I'm landing with an inoperative reverser, I'll select idle reverse on the god side. The asymmetrical force isn't that significant at idle.
Last edited by Check Airman; 2nd January 2018 at 21:33.
Joined: Jun 2007
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From: Wanderlust
In A320 recommend procedure is to select both reversers. It doesn't cause any control difficulties. However if due to strong gusty crosswind causes a problem it is supposed to be brought to idle reverse, control the direction and reapply as necessary. There is no point making one's own procedures.
Joined: Jun 2007
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From: Wanderlust
A320ECAM
It is not called degraded protection but Abnormal attitude law. If the aircraft gets into unusual attitude(which is defined) due to environmental factors full application of controls to recover is enabled in this law.
It is not called degraded protection but Abnormal attitude law. If the aircraft gets into unusual attitude(which is defined) due to environmental factors full application of controls to recover is enabled in this law.
Joined: Sep 2011
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From: FL390
Would it not be better to have a procedure that calls for both throttle levers being retarded to idle with reverse thrust being commanded on both throttle levers at pilot discretion provided there is not a known reverser fault?
Joined: Nov 1999
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From: UK
Oh man, what a disaster. No matter what the reverser situation was, both thrust levers should have been reduced to idle in the first instance, while flaring, and then reverse selected.
My situation was that the reverser that should have been locked out wasn’t, so when I selected reverse on both, the engine with the faulty reverser spooled up but the reverser did not deploy, so I got forward thrust on that engine and reverse thrust on the other.
As long as one is careful, and is landing on a runway with normal grip: using reverse on just one engine of a twin does not present any significant yaw control problems.
Joined: Jul 2013
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From: Everett, WA
My situation was that the reverser that should have been locked out wasn’t, so when I selected reverse on both, the engine with the faulty reverser spooled up but the reverser did not deploy, so I got forward thrust on that engine and reverse thrust on the other.
(3) Each system must have means to prevent the engine from producing more than idle thrust when the reversing system malfunctions, except that it may produce any greater forward thrust that is shown to allow directional control to be maintained, with aerodynamic means alone, under the most critical reversing condition expected in operation.
Joined: Sep 2016
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From: USA
I suppose that the "means" to prevent the system from developing more than idle power could malfunction. So you'd need a means to prevent the means from malfunctioning. And a means to prevent the means to prevent the means...
Joined: Jul 2013
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From: Everett, WA
Vessbot, it's not that simple. 25.1309 requires a safety assessment - I can't speak for Airbus, but Boeing (at the FAA's insistence) treats above idle thrust in an uncommanded direction to be potentially catastrophic. That in turn means the probability of the failure needs to be less than 1/billion flight hours (among other things - that also means it can't happen due to a single failure - it needs to require multiple failures).
Somehow I don't think Uplinker is that unlucky...
Somehow I don't think Uplinker is that unlucky...
Joined: Dec 2002
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From: Where the Quaboag River flows, USA
Is any of this related to the A320 accident at São Paulo Congnhas accident? That was attributed to a reverser malfunction or crew’s response to one.
Joined: Mar 1999
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From: UK
Going back to the opening post.
On my bus conversion course ground school, it was hammered into us that a 320 tends towards being tail heavy and to avoid passenger splits with front cabin empty and rear cabin full like the plague. This was already a well known problem in 2004.
Later in my career I had exactly this happen on a triangular charter where check in staff allocated passengers to the first destination to the front cabin and second destination the rear cabin despite company loading instructions being to divide destinations by left aisle and right aisles instead.
During disembarking at first destination I had the FO monitor the nose wheel strut extension. Sure enough the aircraft was going to go very nose wheel light. There then followed a period of musical chairs as transiting passengers were moved forward to reload the nose wheel. Nightmare as we had to do the same on boarding as the new passengers had been allocated seats in the front cabin based on the seating plan sent from our original departure point. All compounded by the baggage being loaded as per the passengers. First landing in the forward holds. Second in the rear. Would you believe that 3 weeks later, despite the air safety report I filed as well as complaining directly to tech management the same airport repeated the same offence. My comments were completely unprintable. The reason they gave was it was driven by making the baggage handling easy and keeping families together.
My awareness of the potential for loading issues goes back to flying freight in Shorts 360 where the rear hold being bigger than the forward hold was an obvious target for incorrect loading. In fact we had the habit of feeling the weight on the nose leg during the take off roll to check all was well . This probably saved the life of some friends when it was seriously out of balance and wanted to rotate of its own accord at about 30 kts.
To go back to the Verona incident if the passenger split was brought to the captains attention, then this elevates the incident gross professional negligence.
On my bus conversion course ground school, it was hammered into us that a 320 tends towards being tail heavy and to avoid passenger splits with front cabin empty and rear cabin full like the plague. This was already a well known problem in 2004.
Later in my career I had exactly this happen on a triangular charter where check in staff allocated passengers to the first destination to the front cabin and second destination the rear cabin despite company loading instructions being to divide destinations by left aisle and right aisles instead.
During disembarking at first destination I had the FO monitor the nose wheel strut extension. Sure enough the aircraft was going to go very nose wheel light. There then followed a period of musical chairs as transiting passengers were moved forward to reload the nose wheel. Nightmare as we had to do the same on boarding as the new passengers had been allocated seats in the front cabin based on the seating plan sent from our original departure point. All compounded by the baggage being loaded as per the passengers. First landing in the forward holds. Second in the rear. Would you believe that 3 weeks later, despite the air safety report I filed as well as complaining directly to tech management the same airport repeated the same offence. My comments were completely unprintable. The reason they gave was it was driven by making the baggage handling easy and keeping families together.
My awareness of the potential for loading issues goes back to flying freight in Shorts 360 where the rear hold being bigger than the forward hold was an obvious target for incorrect loading. In fact we had the habit of feeling the weight on the nose leg during the take off roll to check all was well . This probably saved the life of some friends when it was seriously out of balance and wanted to rotate of its own accord at about 30 kts.
To go back to the Verona incident if the passenger split was brought to the captains attention, then this elevates the incident gross professional negligence.