1 2 3 .1 .2 .3 .4 .5 .6 .7 .8  Load Factor –G  Indicated Mach Number 19,000 lbs 18,000 lbs 17,000 lbs 16,000 lbs 15,000 lbs 14,000 lbs 13,000 lbs 12,000 lbs 11,000 lbs M$_{MO}$ 30,000 35,000 40,000 45,000 20,000 P $_{r}$e s u $_{r}$e A l t i $_{t}$u d e – 2 5 $_{,}$0 0 0 f t Sea Level 5,000 10,000 15,000 A B D C fact that drag increases more rapidly than lift, causing a  sinking flightpath, is one of the most important aspects of  jet airplane flying qualities. in drag and sink rate as the airplane slides up the back side  of the power-required curve. The sink rate can be arrested  in one of two ways: The stalling characteristics of the sweptwing jet airplane can  vary considerably from those of the normal straight wing  airplane. The greatest difference that will be noticeable to  the pilot is the lift developed vs. angle of attack. An increase  in angle of attack of the straight wing produces a substantial  and constantly increasing lift vector up to its maximum  coefficient of lift, and soon thereafter flow separation (stall)  occurs with a rapid deterioration of lift. By contrast, the sweptwing produces a much more gradual  buildup of lift with a less well-defined maximum coefficient.  This less-defined peak also means that a swept wing may not  have as dramatic loss of lift at angles of attack beyond its  maximum lift coefficient. However, these high-lift conditions  are accompanied by high drag, which results in a high rate  of descent.  [Figure 15-13] In a typical piston engine airplane, V$_{MD}$ in the clean  configuration is normally at a speed of about 1.3 VS.  [Figure 15-12]  Flight below V$_{MD}$ on a piston engine airplane  is well identified and predictable. In contrast, in a jet airplane  flight in the area of V$_{MD}$ (typically 1.5 – 1.6 V $_{S}$) does not  normally produce any noticeable changes in flying qualities  other than a lack of speed stability—a condition where a  decrease in speed leads to an increase in drag which leads to  a further decrease in speed and hence a speed divergence. A  pilot who is not cognizant of a developing speed divergence  may find a serious sink rate developing at a constant power  setting, and a pitch attitude that appears to be normal. The  The differences in the stall characteristics between a  conventional straight wing/low tailplane (non T-tail) airplane  and a sweptwing T-tail airplane center around two main areas. 15-11 • The basic pitching tendency of the airplane at the stall. • Tail effectiveness in stall recovery. • Pitch attitude can be substantially reduced to reduce  the AOA and allow the airplane to accelerate to a  speed above V$_{MD}$, where steady flight conditions  can be reestablished. This procedure, however, will  invariably result in a substantial loss of altitude. • Thrust can be increased to accelerate the airplane  to a speed above V$_{MD}$ to reestablish steady flight  conditions. The amount of thrust must be sufficient to  accelerate the airplane and regain altitude lost. Also,  if the airplane has slid a long way up the back side of  the power required (drag) curve, drag will be very high  and a very large amount of thrust will be required. Stalls Figure 15-11.  Mach buffet boundary chart.