During touch-down, some jolts can be added to the platform.
Different cues can be made, depending whether it is left wheel first or right-wheel first. Furthermore, a soft landing may produce small
bumps, while a hard landing will induce larger amplitude jolts. Vertical
speed before touch-down can be a measure for the amplitude.For making the jolt waveform programmable, I have chosen a sine-wave with
exponential decay.

Sine polarity, begin amplitude, sine period, and decay can be set before the
effect begins. The effect can be added to both roll and pitch axis,
each with independent parameters.

Triggering flight parameter is the wheels-on-ground bit. Aircraft bank
just before touch-down will determine the sine polarity.

The trial program is shown below.

20 ON ERROR GOTO 140

30 CLOSE #1

40 OPEN "com1:9600,n,8" FOR RANDOM AS #1

50 A$=""

55 ON ERROR GOTO 50

60 LINE INPUT#1, A$

70 P$=mid$(A$,3,2)

80 R$=mid$(A$,5,2)

82 D$=right$(A$,2)

85 P=INSTR("123456789ABCDEF",right$(P$,1))+16*INSTR("123456789ABCDEF",left$(P$,1))

86 R=INSTR("123456789ABCDEF",right$(R$,1))+16*INSTR("123456789ABCDEF",left$(R$,1))

87 D=INSTR("123456789ABCDEF",right$(D$,1))+16*INSTR("123456789ABCDEF",left$(D$,1))

90 IF D AND 2 GOTO 95 'check wheels-on-ground bit

91 AR=20:AP=30:N=-1:Rout=0:Pout=0: 'AR is max roll sine amplitude, AP
is max pitch sine amplitude

92 IF R>127 then RPOL=-1 else RPOL=1 'set roll sine polarity
depending on bank

93 GOTO 120

95 ER=1.4:TR=1:EP=1.8:TP=2:NR=20 'ER is roll exponential, TR is
roll sine period, EP is pitch exponential, TP is pitch sine period, NR is
total number of cycles (20 is about 1 second)

100 IF N>NR then Rout=0:Pout=0:GOTO 120 'finish sequence after N
cycles

105 N=N+1

110 Rout=INT(RPOL*AR*(sin(N*3.14/(2*TR)))) 'Roll sine wave with
polarity

111 Pout=INT(AP*(sin(N*3.14/(2*TP)))) 'Pitch sine wave

112 PRINT N;AR;AP;Rout;Pout

115 AR=AR/ER 'Roll sine amplitude decay

116 AP=AP/EP 'Pitch sine amplitude decay

120 DAC1=127+Pout

121 DAC2=127+Rout

123 IF DAC1>255 or DAC1<0 then goto 127

124 OUT 888,DAC1

125 OUT 890,3

126 OUT 890,11

127 IF DAC2>255 or DAC2<0 then goto 131

128 OUT 888,DAC2

129 OUT 890,9

130 OUT 890,11

131 GOTO 50

Left wheel first
Right wheel first

Above graphs show the DAC outputs at touchdown with above program::

Top waveform is roll axis, bottom is pitch axis

**>>> A flight video of the above motion cue can
be seen here. **The video shows a
lousy landing with right-wheel first, bounce and then left-wheel first.

The effect feels pretty good. Most important is the roll jolt. Pitch will
just add a little bump upwards (since you are sitting behind the rotation
point, upward bump = pitch down), probably not really needed.

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