Page 19 - Index

Kåre Halvorsen

Figure 2. Flight data recorder output.

the pullout. The crew called “MAYDAY” to sidered, including computational fluid
air traffic control. The engines were left in dynamics, scale model wind tunnel testing,
takeoff position during the entire pullout, scale model flight testing, etc., but due to
and the speed increased to 325 knots. Once time and cost constraints associated with
control was regained, the “MAYDAY” was these methods, it was decided to develop
cancelled and the flight continued toward a representative (similar but not exact)
Torp, where an approach and landing took model using available aircraft design Michael Bromfield
place without further problems. The NSIA software and desktop mathematical mod-
investigation did not revealed any tech- eling and simulation software. A generic
nical malfunctions in the aircraft and its business jet linear flight dynamics model
control systems. was developed using Matlab/Simulink,
The aircraft's anti- and deicing systems aircraft geometry, mass and balance, initial
on the wings and tailplane were switched flight conditions from the flight data, and
on. The aircraft’s tailplane rubber deicing estimated stability and control derivatives.
boots were in automatic mode and inac- Aircraft static and dynamic stability of
tive during the takeoff and when the stall the generic business jet was assessed for
occurred. It is NSIA’s (Accident Investiga- a range of tailplane efficiency factors to
tion Board Norway) assessment that the simulate the effects of tailplane icing.
systems were not suitable to remove this
relevant type of ice and snow. This acci- Methodology
dent shows the significance of functioning To assess the static and dynamic stability,
crew resource management (CRM) in the modeling of the total aircraft pitching
cockpit when an unexpected and extreme moment is needed, and individual con-
flight situation occurs. In this instance, tributions of all major components are Nadjim Horri
the first officer’s situational awareness and required, not simply tail lift and wing lift.
initial pullout saved the crew.
Static Stability
Special Investigations: The total aircraft pitching moment about
Modeling and Simulation the aircraft’s center of gravity consists of
A review of loss of control in flight (LOC-I) contributions from wing, tail, and fuselage
accidents where icing was a contributory/ (see Figure 3, page 20). Each contribution
causal factor was conducted. Theory relat- generates moments that vary with an-
ed to the effects of icing on main wing and gle of attack and contributions that are
tailplane aerodynamics was undertaken, independent of angle of attack (constant).
and the relationship to stability and con- A negative total pitching moment slope
trol was investigated. Due to the limited represents positive static stability—the
flight data parameter set, it was decided to aircraft returning to the trimmed flight
use modeling to simulate the effects of tail- condition following a disturbance (e.g.,
plane icing and compare it with available sudden change of tail lift). Knut Lande
known data. As ice builds up on the tail, it becomes
Several modeling methods were con- less aerodynamically efficient, and
October-December 2021 ISASI Forum • 19