The Extension of ADS-33—Metrics for Agility Enhancement and Structural Load Alleviation

Load alleviation in tilt rotor aircraft through active control; modelling and control concepts

“…In RHILP it was proposed that the flight path quickness should be adopted as the criterion for quantifying the SLA system effect on handling qualities (HQs), during pitch manoeuvres in aeroplane mode. Quickness is a hybrid measure of how quickly a manoeuvre can be performed (20) . Specifically, it is defined as the ratio of peak rate of change of motion to the motion change, when considering the response to a singlet command (for rate command response type).…”

Rotorcraft Design for Maximized Performance at Minimized Vibratory Loads

“…One of the reasons the attitude quickness criterion has gained large acceptance was due to its physical interpretation (in the limiting case gives the time constant of the aircraft as a function of the time constant of the maneuver). It can be demonstrated that agility quickness has also a physical interpretation, in the limiting case for small-amplitude maneuvers giving the heave damping, for large amplitudes giving the attitude quickness (Pavel & Padfield, 2002). …”

“…This is because the vibratory activity in the hub reaches its absolute peak rather quickly, depending mainly on the initial velocity, the input amplitude (which is a measure of the level of aggressiveness in executing the maneuver) and not on the pulse duration. However, for very aggressive maneuvering, (Pavel & Padfield, 2002) showed that it might appear the situation in which, increasing the flight path change enabled the pilot to pull more g's (so, increased performance) but also increased the vibratory activity in the rotor. The goal of the structural designer would be then to alleviate these high peak loads to lower levels and reduce the sensitivity of the vibratory loads to flight path angle.…”

“…This novel approach may reform the methods presently used to accomplish agility of a new design as it is well known that, in practice, performance is itself often compromised by the need to control and minimize vibration. (Pavel and Padfield, 2002) define an parallel metric, so-called 'vibratory load quickness' quantifying the buildup of loads in the rotor during maneuvering flight:…”

“…As a potential successful metric for agility, (Pavel & Padfield, 2002) proposed a new metric for characterizing agility, the so-called 'agility quickness' defined as the ratio of peak quasi-steady normal acceleration qs z pk n in g units corresponding to a step change in flight path angle :…”