Angle of Incidence

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07 Nov 2011 19:49 #1 by Eric
Angle of Incidence was created by Eric
This is VERY different to aoa, although at first glance it is the same thing.
Angle of Incidence is the angle of the aerofoil centreline compared against the longitudinal centreline of the aircraft fuselage.

So - in normal flight, the fuselage is level, but the Incidence is slightly positive, to create lift.

The difference is, if the Incidence is neutral or negative (ie trailing edge is too high), relative to the fuselage, the back end of the fuz hangs down in flight like a droopy bum, and looks very untidy, as well as creating extra drag, or if the incidence is too positive (leading edge is too high) the aircraft in flight looks as though it is trying to dive at the ground all the time. because the back end will be stuck up like a giraffe's neck.

The angle of Incidence also applies to the tailplane, which should closely match the angle of the mainplane, (sometimes referred to as Decalage), to achieve stable flight. If there is too much difference of angle, the airspeed becomes very critical, because the aircraft will only fly level at one speed. Go faster, and it will keep trying to zoom up into a loop.
An aerobatic aircraft usually has a zero - zero setting, meaning that the incidence of both main and tailplane are both set to zero compared against the longitudinal centreline of the fuselage.
This means that it doesn't matter which way up, or how fast or slowly (within reason) the aircraft goes, the flight characteristics will be unaltered.
A typical trainer aircraft (model and full-size) will have a positive incidence, - ie the tailplane will be set in a position that pulls the back down slightly. At cruising speed, everything will be balanced out by the trim, but as the aircraft slows, the nose will drop, and as it speeds up again, the aircraft will climb, and eventually will settle back at cruising speed.

if you are calm and collected when all about you are going berserk - you've missed something important!

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26 Oct 2012 23:40 #2 by The Beard
Replied by The Beard on topic Angle of Incidence
Am I right that angle of incidence is on the aircraft and Angle of attack is the angle of the aircraft in the Air.

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  • Garry Pollard
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27 Oct 2012 03:35 #3 by Garry Pollard
Replied by Garry Pollard on topic Angle of Incidence
Correct young man .

Garry

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27 Oct 2012 06:42 #4 by The Beard
Replied by The Beard on topic Angle of Incidence
Well Im learning slowly,and Ive also learnt that sometomes we have to reduce the angle of attack as it can be to steep,and this wil cause the model to tip stall because its as if its going up hill to steeply loses speed and stalls,which causes a tip, which causes a crash and makes us unhappy :dry: :oops: :S

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