Reverse Thrust & X/Winds
Even with an interpretation ‘it must be operational’, the absence of a subject or operational consideration in the MEL is not approval for absence of operational thought.
Too often, IMHO, pilots revert to a simplistic ‘SOP’ / ‘legal’ interpretation of documents without thinking about the issue. Of course thinking requires some basic knowledge of the subject, which unfortunately is often absent or has been biased by inappropriate speculation.
So from the gist of the discussion above, when / how would single reverse be used?
Personally I would not; and to avoid the ‘but if you really had too’ argument, there are few if any such situations which could not be covered by a pre departure decision. No go for crosswind on a 'dry' take off (RTO) – the Captain judges the value, and a 'dry' crosswind or wet/ contaminated runway for landing (EU operators may, in addition have to consider landing distance if reverse is credited on contaminated runways).
The MEL covers pre departure issues; what if there was an en route failure, is there similar operational advice in the QRH or is the issue entirely ‘operational’?
Too often, IMHO, pilots revert to a simplistic ‘SOP’ / ‘legal’ interpretation of documents without thinking about the issue. Of course thinking requires some basic knowledge of the subject, which unfortunately is often absent or has been biased by inappropriate speculation.
So from the gist of the discussion above, when / how would single reverse be used?
Personally I would not; and to avoid the ‘but if you really had too’ argument, there are few if any such situations which could not be covered by a pre departure decision. No go for crosswind on a 'dry' take off (RTO) – the Captain judges the value, and a 'dry' crosswind or wet/ contaminated runway for landing (EU operators may, in addition have to consider landing distance if reverse is credited on contaminated runways).
The MEL covers pre departure issues; what if there was an en route failure, is there similar operational advice in the QRH or is the issue entirely ‘operational’?
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Just found...
Just found in the bowels of an old Airbus document which
is entitled "Getting to Grips with Approach and Landing
Accidents Reduction". It's an old document...the issue I
have is "Issue 1" published in October 2000.
Have a read....the subject of interest and discussion is
addressed toward the end of the many-page booklet.
In any event, it's a good read...the whole document is....
BTW, there may be an updated version of this. If someone
knows of such a revision, please let me know....I'll try to
find, download, and save.
is entitled "Getting to Grips with Approach and Landing
Accidents Reduction". It's an old document...the issue I
have is "Issue 1" published in October 2000.
Have a read....the subject of interest and discussion is
addressed toward the end of the many-page booklet.
In any event, it's a good read...the whole document is....
BTW, there may be an updated version of this. If someone
knows of such a revision, please let me know....I'll try to
find, download, and save.
I have had a quick read of it and the Airbus document is remarkably similar to the B737's FCTM.
In both cases they explain how in a X-wind situation, reverse thrust can be resolved into (basically) two vectors, the one we are interested for the purposes of this discussion is the "side force" component.
From the Boeing 737NG FCTM. (The Airbus document requires very similar techniques)
....... As the airplane starts to weathervane into the wind, the reverse thrust side force component adds to the crosswind component and drifts the airplane to the downwind side of the runway. Also, high braking forces reduce the capability of the tires to corner.
To correct back to the centerline, release the brakes and reduce reverse thrust to reverse idle. Releasing the brakes increases the tire-cornering capability and contributes to maintaining or regaining directional control. Setting reverse idle reduces the reverse thrust side force component without the requirement to go through a full reverser actuation cycle. Use rudder pedal steering and differential braking as required, to prevent over correcting past the runway centerline. When directional control is regained and the airplane is correcting toward the runway centerline, apply maximum braking and symmetrical reverse thrust to stop the airplane.
Neither manufacturer mentions using asymmetric reverse thrust.
safetypee wrote:-
Entirely your call as to whether or not you use a single reverser. The B737 allows dispatch with only one operational reverser, provided performance considerations are met. Having done a "couple of dozen" landings in various versions of the 737 (-100/200/600 excepted) in my experience it is a non-event.
Again 737 specific. There is no checklist for a reverse thrust failure whilst in flight. From a performance point of view adjustments to your landing distance, based on the number of serviceable reversers, are covered in the QRH/PI.
As ever operate your aeroplane in accordance with your company's SOPs
In both cases they explain how in a X-wind situation, reverse thrust can be resolved into (basically) two vectors, the one we are interested for the purposes of this discussion is the "side force" component.
From the Boeing 737NG FCTM. (The Airbus document requires very similar techniques)
....... As the airplane starts to weathervane into the wind, the reverse thrust side force component adds to the crosswind component and drifts the airplane to the downwind side of the runway. Also, high braking forces reduce the capability of the tires to corner.
To correct back to the centerline, release the brakes and reduce reverse thrust to reverse idle. Releasing the brakes increases the tire-cornering capability and contributes to maintaining or regaining directional control. Setting reverse idle reduces the reverse thrust side force component without the requirement to go through a full reverser actuation cycle. Use rudder pedal steering and differential braking as required, to prevent over correcting past the runway centerline. When directional control is regained and the airplane is correcting toward the runway centerline, apply maximum braking and symmetrical reverse thrust to stop the airplane.
Neither manufacturer mentions using asymmetric reverse thrust.
safetypee wrote:-
So from the gist of the discussion above, when / how would single reverse be used?
Personally I would not; and to avoid the ‘but if you really had too’ argument, there are few if any such situations which could not be covered by a pre departure decision. No go for crosswind on a 'dry' take off (RTO) – the Captain judges the value, and a 'dry' crosswind or wet/ contaminated runway for landing (EU operators may, in addition have to consider landing distance if reverse is credited on contaminated runways).
Personally I would not; and to avoid the ‘but if you really had too’ argument, there are few if any such situations which could not be covered by a pre departure decision. No go for crosswind on a 'dry' take off (RTO) – the Captain judges the value, and a 'dry' crosswind or wet/ contaminated runway for landing (EU operators may, in addition have to consider landing distance if reverse is credited on contaminated runways).
The MEL covers pre departure issues; what if there was an en route failure, is there similar operational advice in the QRH or is the issue entirely ‘operational’?
As ever operate your aeroplane in accordance with your company's SOPs
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Unless AFM specifically allows messing with it for x-wind, I wouldn't consider assymetric reverse use.
Don't try this at home!
When I was a young chap in RHS of a caribou, skipper made a steep approach on a strip to avoid actual enemy ground fire. He selected full reverse pitch just before touchdown due we were already half way along the strip. Due to a fault, one prop stayed in forward pitch, with approx climb power, so it was an exciting ride from there to touchdown and for the remaining 700 ft.
Don't try this at home!
When I was a young chap in RHS of a caribou, skipper made a steep approach on a strip to avoid actual enemy ground fire. He selected full reverse pitch just before touchdown due we were already half way along the strip. Due to a fault, one prop stayed in forward pitch, with approx climb power, so it was an exciting ride from there to touchdown and for the remaining 700 ft.
