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Pilot’s Operating Manual
Revision A1: Nov, 2002
Hawker 800XP Pro Line 21
Section VII - SAFETY INFORMATION
decrease, if airspeed is reduced; (2) remain constant, if airspeed is held constant and no failures occur;
or (3) increase to the point of self-destruction, especially if airspeed is high and/or is allowed to increase.
Flutter can lead to an in-flight break up of the airplane.
Airplanes are designed so that flutter will not occur in the normal operating envelope of the airplane as
long as the airplane is properly maintained. In the case of any airplane, decreasing the damping and
stiffness of the structure or increasing the trailing edge weight of control surfaces will tend to cause
flutter. If a combination of these factors is sufficient, flutter can occur within the normal operating
envelope.
Owners and operators of airplanes have the primary responsibility for maintaining their airplanes. To
fulfill this responsibility, it is imperative that all airplanes receive a thorough preflight inspection.
Improper tension on the control cables or any other loose condition in the flight control system can also
cause or contribute to flutter.
Pilots should pay particular attention to control surface attachment hardware including tab pushrod
attachment during preflight inspection. Looseness of fixed surfaces or movement of control surfaces
other than in the normal direction of travel should be rectified before flight. Further, owners should also
take their airplanes to mechanics who have access to current technical publications and prior
experience in properly maintaining that make and model of airplane.
The owner should make certain that control cable tension inspections are performed as outlined in the
applicable Raytheon Aircraft Company Inspection Guide. Worn control surface attachment hardware
must be replaced. Any repainting or repair of a moveable control surface will require a verification of the
control surface balance before the airplane is returned to service. Control surface drain holes must be
open to prevent freezing of accumulated moisture, which could create an increased trailing-edge-heavy
control surface and flutter.
If an excessive vibration, particularly in the control column and rudder pedals, is encountered in flight,
this may be the onset of flutter and the procedure to follow is:
1. IMMEDIATELY REDUCE AIRSPEED (lower the landing gear if necessary).
2. RESTRAIN THE CONTROLS OF THE AIRPLANE UNTIL THE VIBRATION CEASES.
3. FLY AT THE REDUCED AIRSPEED AND LAND AT THE NEAREST SUITABLE AIRPORT.
4. HAVE THE AIRPLANE INSPECTED FOR AIRFRAME DAMAGE, CONTROL SURFACE
ATTACHING HARDWARE CONDITION/SECURITY, TRIM TAB FREE PLAY, PROPER CONTROL
CABLE TENSION, AND CONTROL SURFACE BALANCE BY ANOTHER MECHANIC WHO IS
FULLY QUALIFIED.
Turbulent Weather
A complete and current weather briefing is a requirement for a safe trip.
Updating of weather information enroute is also essential. The wise pilot knows that weather conditions
can change quickly and treats weather forecasting as professional advice, rather than an absolute fact.
He obtains all the advice possible, but stays alert to any sign or report of changing conditions.
Plan the flight to avoid areas of reported severe turbulence. It is not always possible to detect individual
storm areas or find the in-between clear areas.
