Assymetric-How much difference between heading and track?
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I should dig out some old 727 notes but my recollection is that the VG would re-erect to a false horizon if prolonged bank were to be maintained ... some head-scratching here but 7-8 degrees max for the problem to exist strikes a chord in the memory .. I will dig out the systems notes next week and check ...
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john tulla says....
(a) best climb performance is somewhere around 2-3 degrees bank (similar for any multi) ...
Banking away from the horizontal will never give you better climb performance. You are tilting the lift vector away from the vertical.
The "five to the live, half ball slip" is a Controllability (=Vmca) technique.
Think of the sine v. the cosine of an angle of 2-5 degrees.
Tilting the lift vector a small amount (2-5 degrees) results in a LOSS of climb performance, but negligible in a practical sense (cosine of a small angle approaching 1). But it does result in a small but useful turning force into the live engines (sine of the same small angle), effectively lowering Vmca for the same power setting. A very useful technique in piston twins and light turboprops. Rent a Duchess and a skilled Multi instructor and see the difference in controllability approaching Vmca with (a) nil bank and (b) 'five to the live.'
This is not usually required in most transport aircraft due to the rudder power available.
Also, the Duchess, etc don't have roll spoilers.
SOP in the BAe146 with one or two inop on the same side is to fly wings level, and apply rudder on the 'live' side to level the control wheel. A small amount balance ball left or right as appropriate will be indicated.
This also ensures that the roll spoilers, activated at about 3 degrees of control wheel deflection, are not deployed (and therefore not adding drag during one or two inop abnormals) except when rolling into and out of a turn.
(a) best climb performance is somewhere around 2-3 degrees bank (similar for any multi) ...
Banking away from the horizontal will never give you better climb performance. You are tilting the lift vector away from the vertical.
The "five to the live, half ball slip" is a Controllability (=Vmca) technique.
Think of the sine v. the cosine of an angle of 2-5 degrees.
Tilting the lift vector a small amount (2-5 degrees) results in a LOSS of climb performance, but negligible in a practical sense (cosine of a small angle approaching 1). But it does result in a small but useful turning force into the live engines (sine of the same small angle), effectively lowering Vmca for the same power setting. A very useful technique in piston twins and light turboprops. Rent a Duchess and a skilled Multi instructor and see the difference in controllability approaching Vmca with (a) nil bank and (b) 'five to the live.'
This is not usually required in most transport aircraft due to the rudder power available.
Also, the Duchess, etc don't have roll spoilers.
SOP in the BAe146 with one or two inop on the same side is to fly wings level, and apply rudder on the 'live' side to level the control wheel. A small amount balance ball left or right as appropriate will be indicated.
This also ensures that the roll spoilers, activated at about 3 degrees of control wheel deflection, are not deployed (and therefore not adding drag during one or two inop abnormals) except when rolling into and out of a turn.
ITCZ,
I disagree with your assertion that wings level will give max performance (asymmetric case). If the wings are kept level there WILL be some amount of sideslip with a consequential rise in total drag.
Min. drag will occur at around 2-3 deg AoB and that's where best performance will be found. Is that slight gain in performance necessary? Most times not, expecially in performance 'guaranteed' a/c. Occasionally (or perhaps, more likely) in FAR23 or equivalent types it can well mean the difference between descending or not.
Yes, 5 deg AoB is a controllability consideration, and is one of the conditions set by the certification authority to set realistic boundaries to just how low a Vmc is achievable. A very low Vmc is desirable by the manufacturer because of V1/Vr etc gains.
I disagree with your assertion that wings level will give max performance (asymmetric case). If the wings are kept level there WILL be some amount of sideslip with a consequential rise in total drag.
Min. drag will occur at around 2-3 deg AoB and that's where best performance will be found. Is that slight gain in performance necessary? Most times not, expecially in performance 'guaranteed' a/c. Occasionally (or perhaps, more likely) in FAR23 or equivalent types it can well mean the difference between descending or not.
Yes, 5 deg AoB is a controllability consideration, and is one of the conditions set by the certification authority to set realistic boundaries to just how low a Vmc is achievable. A very low Vmc is desirable by the manufacturer because of V1/Vr etc gains.
