new procedures for approach-to-stall
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new procedures for approach-to-stall
I understand that a carrier in the US has issued a bulletin to its pilots changing the procedures for approach-to-stall in that they should use the stall procedures- lower nose to escape buffet/shaker even below the horizon if nec and TOGA, instead of TOGA and using pitch to maintain altitude.
Nothing new here. Airbus AND Boeing worked together and came up with a new "Stall recovery" checklist that placed emphasis on lowering the nose to reduce the AOA BEFORE adding thrust. This checklist was placed in our QRH's DEC 2010.
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One of the concerns at high angles is that a fistful of throttle results in a significant up force at the nacelle lip .. just what you don't want recovering from a stall ....
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You talking about the nose up moment or increased relative
A of A at the inlet lip caused by same ? (c'mon, be nice .. it's not fair when you've figured out who I am but I haven't been able to do the same of you, yet - JT)
A of A at the inlet lip caused by same ? (c'mon, be nice .. it's not fair when you've figured out who I am but I haven't been able to do the same of you, yet - JT)
I suspect that the notice clarifying (or changing) stall recovery procedures is in response to one of the recommendations made in the NTSB report of the Colgan Dash 8 accident near Buffalo, NY.
The NTSB recommended that operators (and manufacturers) take appropriate action to ensure that clear direction is given to crews about the stall recovery procedures for each type, and to emphasize the need to get the aircraft flying again ASAP (as opposed to 'not losing altitude').
The NTSB recommended that operators (and manufacturers) take appropriate action to ensure that clear direction is given to crews about the stall recovery procedures for each type, and to emphasize the need to get the aircraft flying again ASAP (as opposed to 'not losing altitude').
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You talking about the nose up moment
Jet or prop at high alpha (ie low speed) with a significant thrust increase (ie fistful of throttle) sees an increase in mass airflow with a change of airflow direction through the nacelle inlet or prop disc. Result is a vertical force in the plane of the prop or nacelle face which provides a nose up pitching moment component to the equation of what's going on in pitch.
This can be a particular problem on piston to turboprop conversions with higher power output engines due to moving the engine forward to keep the airframe cg under design control .. ie a bigger moment arm for the normal force to act at.
Some such mods then need to include a SAS add-on to provide artificial elevator loading - at the lowspeed end of the envelope - to fool the pilot into seeing an acceptable static stability. In its simplest form, a SAS is just a variable downspring loading in the elevator circuit to keep control forces as they should be for the pilot. Without the SAS input, and especially for the landing climb case, one can see a major reduction in static stability. Some mod designs may see the aircraft with a stick load reversal without the SAS input. It is for this reason that some POH procedures will impose a thrust increase limit for the landing climb case if the SAS is out of action .. so limiting the nose up force and the associated nose up pitching moment which, in turn affects the elevator loads felt by the pilot.
Jet or prop at high alpha (ie low speed) with a significant thrust increase (ie fistful of throttle) sees an increase in mass airflow with a change of airflow direction through the nacelle inlet or prop disc. Result is a vertical force in the plane of the prop or nacelle face which provides a nose up pitching moment component to the equation of what's going on in pitch.
This can be a particular problem on piston to turboprop conversions with higher power output engines due to moving the engine forward to keep the airframe cg under design control .. ie a bigger moment arm for the normal force to act at.
Some such mods then need to include a SAS add-on to provide artificial elevator loading - at the lowspeed end of the envelope - to fool the pilot into seeing an acceptable static stability. In its simplest form, a SAS is just a variable downspring loading in the elevator circuit to keep control forces as they should be for the pilot. Without the SAS input, and especially for the landing climb case, one can see a major reduction in static stability. Some mod designs may see the aircraft with a stick load reversal without the SAS input. It is for this reason that some POH procedures will impose a thrust increase limit for the landing climb case if the SAS is out of action .. so limiting the nose up force and the associated nose up pitching moment which, in turn affects the elevator loads felt by the pilot.
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Nothing new here. Airbus AND Boeing worked together and came up with a new "Stall recovery" checklist that placed emphasis on lowering the nose to reduce the AOA BEFORE adding thrust. This checklist was placed in our QRH's DEC 2010.
CulturAiles - human factors - B737-800 stall during approach
I suspect that the notice clarifying (or changing) stall recovery procedures is in response to one of the recommendations made in the NTSB report of the Colgan Dash 8 accident near Buffalo, NY.
TK1951
CulturAiles - human factors - B737-800 stall during approach
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Nitpicker,
Agreed in terms of generic advice, but now there is a specific procedure for stall reovery where previously the non-normal maneuvre was for approach to stall which is a controlled flight condition and it specified adding thrust first. In the old QRH there was actually a line of text which stated that if a stall recovery was required, then the first action is to apply and maintain nose down elevator and was mashed up with the nose low recovery procedure and stangely divorced from the nose high one.
The amendment is overdue, when I realised one day that I had confused the approach to stall procedre for stall recovery I wondered why there was no specific procedure.
Nothing new here. Airbus AND Boeing worked together and came up with a new "Stall recovery" checklist that placed emphasis on lowering the nose to reduce the AOA BEFORE adding thrust.
The amendment is overdue, when I realised one day that I had confused the approach to stall procedre for stall recovery I wondered why there was no specific procedure.
