When is wake vortex strength the greatest for a generating aircraft?

7-4-3. Vortex Strength
a. Weight, speed, wingspan, and shape of the generating aircraft's wing all govern the strength of the vortex.
The vortex characteristics of any given aircraft can also be changed by extension of flaps or other wing
configuring devices. However, the vortex strength from an aircraft increases proportionately to an increase in
operating weight or a decrease in aircraft speed. Since the turbulence from a "dirty" aircraft configuration hastens
wake decay, the greatest vortex strength occurs when the generating aircraft is HEA VY , CLEAN, and SLOW.
b. Induced Roll
Wake Turbulence 7-4-1

AIM 2/20/25
1. In rare instances, a wake encounter could cause catastrophic inflight structural damage to an aircraft.
However, the usual hazard is associated with induced rolling moments that can exceed the roll-control authority
of the encountering aircraft. During inflight testing, aircraft intentionally flew directly up trailing vortex cores
of larger aircraft. These tests demonstrated that the ability of aircraft to counteract the roll imposed by wake
vortex depends primarily on the wingspan and counter -control responsiveness of the encountering aircraft.
These tests also demonstrated the difficulty of an aircraft to remain within a wake vortex. The natural tendency
is for the circulation to eject aircraft from the vortex.
2. Counter control is usually effective and induced roll minimal in cases where the wingspan and ailerons
of the encountering aircraft extend beyond the rotational flow field of the vortex. It is more difficult for aircraft
with short wingspan (relative to the generating aircraft) to counter the imposed roll induced by vortex flow. Pilots
of short span aircraft, even of the high performance type, must be especially alert to vortex encounters. (See
FIG 7-4-2.)
FIG 7-4-2
Wake Encounter Counter Control
COUNTER
CONTROL