During a recent uunet debate I asserted that an aircraft would not depart, or spin, from a coordinated turn.

It was my understanding there had to be yaw, in order to risk a spin.   Note that I have demonstrated spins or received specific spin instructions in five different airplanes, on six occasions; and I am by no means an expert.



                                                               

I was chided that a coordinated climbing turn could produce a dramatic wing drop (and potentially a spin) due to the different angle of attack experienced by the outside wing.

The responder offered the following references:

Full power stalls in a balanced climbing turn tend to result in the outer wing stalling first, because of the higher aoa of the outer wing, with a fairly fast wing and nose drop (particularly so if the propeller torque effect is such that it reinforces the roll away from the original direction of turn and the aircraft is a high wing configuration) and likely to result in a stall/spin situation that any pilot lacking spin recovery experience may find difficult to deal with. If the climbing turn is being made with excessive bottom rudder then the lower wing might stall first with the consequent roll into the turn flicking the aircraft over. Recovery from a stall in a climbing turn is much the same as any other stall – ease the control column forward to about the neutral position, stop any yaw, level the wings and keep the power on.

http://www.auf.asn.au/groundschool/umodule11.html#climb_turns

When the aircraft stalls in a climbing turn, the high wing is at a greater angle of attack than the low wing and therefore stalls first, which results in a rolling motion toward the high wing, creating asymmetric lift and drag. The down-going wing will stall further as a result of less lift and more drag than the up-going wing. A deeper stall, generated by aft C of G, will aggravate these asymmetries, increasing aircraft rolling and yawing moments into the down-going wing. In addition, the aft C of G reduces the distance from the C of G to the centre of pressure of the vertical fin, thus reducing directional control authority, making recovery more difficult

http://www.tsb.gc.ca/en/reports/air/1994/a94o0316/a94o0316.asp?print_view=1

In a climbing turn, the outside or upgoing wing is meeting the relative wind at a slightly higher angle of attack than the lower wing.   If we pull on the column to the stalling bite, then the upgoing wing will reach it first...The upgoing wing suddenly drops and the wing falls away from the original direction of turn.

http://www.casa.gov.au/fsa/2000/sep/FSA34-35.pdf

The Transport Canada Guidelines on Stall Training and Spin Awareness specifically requires demonstrations in coordinated climbing turns:

http://www.tc.gc.ca/civilaviation/general/Flttrain/TP13747/stalltrain.htm

I am not certain you could actually accomplish a spin in a certficated airplane, stalling it in this manner
from coordinated flight.  My original thesis in the debate insisted that if the ball was in the center (and controls
were properly applied thru the stall) there would be no spin.

If a climbing turn on the verge of Vs risked departure would preparations for a chandelle turn carry specific
warnings?   I could find none in instructional texts?  Granted, at the point of minimum airspeed the bank angle is
being relaxed to zero; however the hamfisted manuevers I have demonstrated should have risked
catastrophe.

I did a cursory check of the NTSB database and could find no correlation between chandelle and spin, however,
there were incidents of loss of control following a climbing go-around.



At this time, I do not know the answer to the question; departing from coordinated flight.  However, the
discussion has challenged my thinking:

The convergence of insufficient right rudder and a slipping turn, the left turning tendencies and the 
assymetrical stall could gang up on our hapless pilot resulting in a quick snap and
spin during a climbing right turn away from obstacles in the departure path.