air entering the compressor section of jet engines has to be subsonic. Entry of supersonic airflow into the engine can cause compressor stalls
engine stag-nation and flame out. Therefore
the inlets for aircraft designed to operate in the transonic or supersonic speed ranges must be designed to slow the air entering the engine to subsonic speeds before the air enters the compressor section. Jet aircraft which are operated above their limiting Mach number may therefore experience engine malfunctions associated with the ingestion of supersonic airflows.G. FLuttER (see Figure 33-5). Flutter involves a combination of the following three factors: 1. High dynamic pressure (high density or more likely high speed) 2. Structural stiffness (the amount of deflection experienced by a load on a structure and its ability to store energy elastically). 3. Inertia factors (which involve the natural frequency of the structure and the frequency with which the aerodynamic forces are applied.Flutter is a possibility any time an aircraft flies above its limit airspeed.H. LoSS oF ContRoL EFFECtIvEnESS/ContRoL REvERSAL (see Figure 33-6). Excessively high speeds or excessively flexible structure can result in degraded control effectiveness or even loss of control. All air-planes are flexible. When exposed to loads
their structure deflects. When a control surface such as an aileron or an elevator is deflected trailing edge down
the wing or horizontal stabilizer to which it is attached will twist leading edge down. When the control surface is deflected leading edge up
Figure 33-6. Loss of Control Effectiveness/Control Reversal.