mechanism about differential spoilers

[junechw0326]

HI guys. Wanna ask for a detailed explanation about the mechanism of differential spoiler and non differential spoiler. How do them actually work? just get frustrated when i saw an expression below:

non differential spoiler:

speed brakes fully retracted:right spoiler extends
left spoiler remains retracted

speed brakes fully extended:right spoiler remains extended
left spoiler remains extended

speed brakes half extended:right spoiler extends further
left spoiler doesnt move

differential spoiler:

speed brakes fully retracted:right spoiler extends
left spoiler remains retracted

speed brakes fully extended:right spoiler remains extended
left spoiler retracts

speed brakes half extended:right spoiler extends further
left spoiler retracts

few questions about this statement:
here it was saying the difference between diff. spoiler and non-diff. spoiler is diff. spoiler retract and supplement roll control when speed brake is fully extended. however, if non-diff. spoiler doesnt contribute to roll control, why there is difference between right spoiler and left spoiler?(because of balancing P factor? I dont know just guess :P)
also why right spoiler needs to extend further when speed brake half extended?
is the situation of differential spoilers above talking about one direction roll movement or i am actually out of track?

Pls help!
i am a newbie on aviation as well as in this forum.sorry for my poor English and if i am posting it in a wrong place.

Thanks all!

[vapilot2004]

The term "differential spoilers" relates to how spoilers augment the roll commanded by the ailerons during speed brake operation. This arrangement maximizes the augmentation of roll control with a small sacrifice in (commanded) profile drag braking.

"Non-differential" spoiler arrangement will augment aileron roll control to a lesser degree during partial extension and when the speed brakes are fully extended, they offer no help.

The example you have given is for a right turn.

the difference between diff. spoiler and non-diff. spoiler is diff. spoiler retract and supplement roll control when speed brake is fully extended.

This is one of the key differences. See below for the rest.

however, if non-diff. spoiler doesnt contribute to roll control, why there is difference between right spoiler and left spoiler?

Non-differential (standard) spoiler deployment contributes to roll control in all but the fully extended speed brake configuration. Another way to think about it is the non-differential spoiler arrangement never reduces profile drag during roll control augmentation.

why right spoiler needs to extend further when speed brake half extended?

To assist with roll control.

[PDR1]

The reason for using spoilers for roll-control is to do with torsional stiffness in the wings. Ailerons are effective, but they impart a twisting load at a point which is both a long way out spanwise, and a long distance from the centre of wing area chordwise. If the wing isn't stiff then what *actually* happens is the aileron causes the wing to twist in the opposite direction, often to the extent that the change in wing AoA produces a greater roll moment than the aileron - a phenomenon called "aileron reversal". To visualise this think of the aileron acting as a servo tab on the wing TE.

To prevent this situation occuring the wing must be torsionally stiff, and the extra structure to do this is a significant weight penalty in an airliner; one which they'd rather avoid.

One of the earliest solutions to this problem was to move the ailerons inboard to a stiffer part of the wing - as first seen on the F100 super sabre. This approach works for the low aspect ratio wings of fighters, but doesn't provide sufficient roll authority for the high aspect ratio wings of transports. So the alternative is to use spoiler controls which don't impart big torsional stresses. IIRC this was first done by Howards Hughes's team on the sadly abandonned XF-11 project, and then by Northrop on the P-61 black widow. Its use on large aircraft is now almost universal, and the small ailerons which are still fitted are often only there to provide tactile feedback ("feel") for the pilot.

[galaxy flyer]

One of the earliest solutions to this problem was to move the ailerons inboard to a stiffer part of the wing - as first seen on the F100 super sabre.

Might have solved aileron reversal, but the Hun still at strong adverse yaw at higher AOA—high G or slow speed. Nasty Sabre dance video. Best 500 hours of my flight time.