Is an aircraft in equilibrium when it's in a spin?

[jodiem]

Hey guys,

Have heard varying answers, none seem succinct or clear enough to me so just wondering if anyone could post a correct and easily explainable answer to the question "Is an aircraft in equilibrium when its in a spin?".

Thanks for your time.

[tigerbatics]

The forces and moments acting on an aeroplane in a fully developed steady state spin are in equilibrium. That is why it is a steady state spin. At the earlier stage of the spin, after entry, the equlibrium has not been attained so the spinning motion depends on the mass distibution and aerodynamic forces developing to the point where it occurs. So, yes and no.

[B2N2]

Not in the entry phase or initial phase also called an incipient spin.
After some point, usually 3-4 rotations the spin stabilizes as in the rate of rotation and the pitch attitude or pitch oscillations become constant. From there it is a self sustaining stabilized maneuver. I guess you could call that "equilibrium".

Read all about it...:
Spin (flight - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Spin_(flight))

[Bfpplbp]

hi jodiemEquilibrium is the state of an object when no part of the object is accelerating. Two conditions for equilibrium are that the net force acting on the object is zero, and the net torque acting on the object is zero. eg, flying in a straight line at a constant speed...same principal applied to an aircraft in a turn,aircraft turning/banking through 360* at a constant rate, in balance and maintaining altitude is not in equilibrium as the aircraft is accelerating towards the centre of the turn.... ie changing direction thus there must be a torque or force.... (not a condition of equilibrium)hopefully someone can provide a better answer and examplehappy and safe flying!

[homeguard]

Jodiem

The simplest explanation is given by Ron Campbel, Flying Training for the Private Pilot Licence, Instructor Manual; Spinning Long Brief, 'The Characteristics of a spin'.

To qoute: "Once the aircraft has settled into a spin the forces and the moments acting upon it will be in equilibrium and this balance of forces and moments will determine the values of angle of attack, sideslip, turn radius, rate of descent and other factors".

Hope that helps.

[jodiem]

Hey guys,

Thanks for the words of wisdom. I put them to the pilot who posed the original question and he seemed pretty happy with the responses so cheers!

Jodiem