The main objectives in developing the NASA in situ windshear detection algorithm were to provide a measurement standard for validation of forward-look sensors under development, and to demonstrate the algorithm's ability to operate with a suitably low nuisance alert rate. It was necessary to know exactly how the algorithm was implemented and what parameters and filtering were used, in order to be able to fully test its effectiveness and correlate in situ results with forward-look sensor data

Oseguera, Rosa M.

English

NASA Technical Reports Server

Session I. NASA Flight Tests N93- 9
NASA Wind Shear Flight Test In Situ Results
Rosa Oseguera, NASA Langley Research Center
https://ntrs.nasa.gov/search.jsp?R=19930010404 2020-03-17T08:13:24+00:00Z
NASA WINDSHEAR FLIGHT TEST
IN SITU RESULTS
Presented By:
Rosa M. Oseguera
NASA Langley Research Center
at
4th Combined Manufacturers' and Technologists'
Airborne W1ndshear Review Meeting
April 14-16, 1992
OUTLINE
• BACKGROUND
- OBJECTIVES
- DESIGN REQUIREMENTS
• IMPLEMENTATION
• RESULTS
- ALGORITHM TESTING
- MICROBURST FLIGHTS
• SUMMARY
46
OBJECTIVES
O PROVIDE MEASUREMENT STANDARD FOR
FORWARD-LOOK SENSOR EVALUATION
• DEMONSTRATE OPERATIONAL UTILITY
The main objectives in developing the NASA in situ windshear detection algorithm were
to provide a measurement standard for validation of forward-look sensors under
development, and to demonstrate the algorithm's ability to operate with a suitably low
nuisance alert rate. It was necessary to know exactly how the algorithm was
implemented and what parameters and filtering were used, in order to be able to fully
test its effectiveness and correlate in situ results with forward-look sensor data.
II I n I
DESIGN REQUIREMENTS
• MINIMIZE AIRCRAFT-INDUCED HAZARD INDEX
DUE TO:
-CONFIGURATION CHANGES
-THRUST EXCURSIONS
- MANEUVERING FLIGHT
-TURNS IN STEADY WIND
MINIMIZE NON-HAZARDOUS ATMOSPHERE-INDUCED
HAZARD INDEX
- TUNE TO APPROPRIATE SCALE OF MOTION
- GUST REJECTION / TIME-TO-ALERT TRADE-OFFS
- LOW NUISANCE ALERT RATE
• EMPLOY CURRENTLY AVAILABLE STANDARD
SHIP-SET SENSORS
The major design requirements are 1) minimize effects of aircraft-induced motions,
such as those shown in the first bullet item, and 2) minimize the effects of non-
hazardous atmospheric motions, which is done using gust-rejection filters. The second
item shows the major issues addressed in development of the filters, such as tuning the
filters to the larger-scale motions associated with windshear, choosing an acceptable
trade-off between improving the gust-rejection characteristics and decreasing the
latency in the system, and maintaining a low nuisance alert rate; 3)implementing the
system using currently available, standard sensors, to make the implementation
feasible on any inertially-equipped airplane.
47
WIND SHEAR HAZARD INDEX
• THEORY
T-D
- POTENTIAL CLIMB ANGLE 7p- mg
- HAZARD INDEX
V_# • e a w h
F- g Va
F
• IN SITU IMPLEMENTATION
F { _i " ea- va Wh= } -
The method for quantifying the windshear hazard is by computing the windshear
hazard index (F-factor), which is shown as it relates to an airplane's potential climb
angle and ratio of thrust-minus-drag to weight. The definition of F-factor (second
equation) is shown as a function of the wind vector dot product with a unit vector in the
direction of the airspeed vector, vertical wind component, and true airspeed. The
bottom equation shows the general full 3-dimensional implementation of an in situ
algorithm, with F computed from aircraft-measured parameters such as inertial velocity
rate and airspeed rate, rather than wind measurements. The NASA implementation was
realized in full 3-D form, to not degrade its performance in any flight regime.
CONCEPTUAL REPRESENTATION OF NASA IN SITU
F-FACTOR ALGORITHM
INERTIAL
AND AIR
DATA
SENSOFIS
ALGORITHM
PROCESSING
7. +
-
This shows the how the in situ algorithm is implemented on NASA's B-737-100, where
the Algorithm Processing represents the first part of the in situ algorithm, which
produces the three terms shown. These terms are then filtered (shown as G(s) boxes)
to give horizontal, vertical, and total in situ F-factor.
48
PUSHOVER/PULL-UP
(FUGHT DATA. 2"3flAY 01)
_ 30). ! , , ! :.1..........L_ _L .........!
.,°°
I 0 10 20 30 40 50 _ ?0 00
0.10
0.06
_0.00
-0,10
l I i , :
!
....... '-- i .... I ! i i! J : 1 : ,
""-4----' 4_ ¢
10 20 30 4o so 8o 70 _0
TIME. seconds
The in situ algorithm was flight-tested locally, with maneuvers intended to induce
significant changes in specific state variables to ensure the algorithm's ability to reject
aircraft maneuvering effects. This figure shows a pushover/pullup maneuver, where the
airplane was pitched up and down in a porpoising type of motion to induce high normal
acceleration changes. Ideally, F-factor (bottom plot) should be close to zero, with
allowances for acceptable levels of turbulence and signal noise, and well below the
FAA-established alert threshold level of F=0.105. As shown, there was no adverse
effect of the pitching motion on the in situ F-factor measurement.
I I II
,_ PUSHOVER/PULL-UP
(FLIGHT DATA, 23 MAY 91)
.--. 2.0
p l ; _ i
ul i i i , i i
)1.0 . : ....
"J O.S , . ; .i l i ,,
,K
cc o.o| .... i-- " _ _
2(I0
; i1__.,. I :_ ! I
-=
180 . , ............ . ....................
10 20 30 40 50 00 70 tJo
TIME, seconds
The top figure shows the range of measured normal acceleration, which equals 1.0 g in
level, unaccelerated flight. This maneuver induced an increase of 0.6 g and decrease
of 0.4 g from the nominal value. True airspeed and groundspeed (bottom plot) am close
in value, indicated there was no significant wind.
49
ACCELERATION/DECELERATION
(111.10_ DATA. 21 MAY 91)
3OO
0 10 20 3O 4O SO 6O 7O
0.10
-0.10
t+1ti!
i
0 10 _ _ _ _ m
TIME, seconds
The effect of changing longitudinal acceleration was tested by executing abrupt
accelerations and decelerations, where the maximum rate of change was sustained
over at least 50 knots change in airspeed. The effect of this motion did not appear to
cause any adverse effect on the F-factor (bottom plot) computed by the algorithm.
i
_J
Z
<
,-I
,J
O
TURNING FLIGHT
(FLIGHT DATA, 23 MAY 91)
_0 .................................
!-I ....i\ i/_ !\i i
..o + ': iV
-6o i I ' ' :
20 40 60 80 100 120 140 160 100
O. t 0 ........ ........ ; ......... _ ....
1 i I _ , i
¢ 0.05 i I
'" .o._
,,0.10 l i ' i
20 40 eO I10 100 120 140 160 1110
TIME, seconds
The effectiveness of the 3-D implementation was tested by executing turns at high bank
angles. The top figure shows a number of partial turns, at high bank angles and
through abrupt changes in direction.
SO
TMP,NING IN STEAD¥ WIND
(Iq.JGHT DATA. 2 OCT 9O)
2O0
40
d
_o
r
SO 100 1110 200 250 3OO
0.10
.r
U. -O.OS
.4.10
0
....... i .... i .... i .....
50 100 t50 200 250 3(X)
TIME, seconds
A final manuevering test was turning in a steady wind condition. The top plot shows the
bank angle for the two turns executed in a steady wind of greater than 60 knots. The
first was through a 3600 heading change at 200 bank, the second through 1800
heading at 45 o bank. F-factor (bottom plot) shows no adverse effect of this manuever.
II II III
5OO
o
= 450
G 400
q
,350
TURNING IN STEADY WIND
(FLICIIT DATA. 2 OCT 90)
._., .... , .... , .... _'.._ , ....
\ /
\ /
• _ "
\ /
\ / _ "
_true -,Irtpeed
|roundtpeed
,.,,I .... | .... lli.,J.j.,I.,,#
0 |00 200 300 400 500 600
100
.-." o
[ -5o
 -Ioo
-150
,'_T,|,,,,| .... i,,,,| r,,,| ....
i, • | .... J .... | .... | .... J,* •
0 100 200 800 400 500 _00
TildE, goeond=
These plots show the effect of the turns in steady wind on the airplane's velocity. The
top plot shows true airspeed was constant, while groundspeed varied throughout the
turns. The bottom plot shows the along-track wind measured by the airplane, varying by
150 knots over 20 seconds (t=250 to 270 sec), and indicates the algorithm's ability to
reject the change of longitudinal wind, rather than measure it as a shear.
51
LANDING APPROACH
THROUGH MICROBURST
(SIMULATOR DATA)
0.4 .... .... 1....
i
0.3 - ---_-- Ir
/
- -1" W
0.1 --
0.0 '
-0.1 • •
-0.2 ..............
vt,l[_Mr|,t,tlev,t B,,,=o,,,
i
i
Ind_derlvea
1 i
.....i.....[.... 1........ i ....
0
_!\.l 1
............ L.._I_._]
10 20 30 40 50 60 70 80 90 100110 120130140
TIME, seconds
After having shown in flight that the algorithm rejected aircraft maneuvering effects, it
was necessary to show that it could also detect a windshear, which was done in
simulation, as shown. The in situ F-factor shows some lag and attenuation of the peak,
which is primarily due to the effect of the gust-rejection filters, and was expected. Wind-
derived F-factor is an instantaneous F-factor computed directly from the known winds.
MICROBURST PENETRATION
FLIGHT DATA, 20 JUN 91
82
0.15.. , • , • , " 1 • , • , " , " , " , • = • , '
o.osi- / "\ ,,;
-oo t
0 10 20 30 40 50 60 70 80 90 100110 120
15.- = - = - , - , - , . = . I - I . , - i - = .
10 _ --along-track p_ ._ jk
i. ___v..,°.,
o-t,..,._.l ,. ( - .,,-,...
0 10 20 30 40 50 60 70 80 90 100 110 20
TIME, seconds
Data shown is for a microburst
penetration during the 1991 NASA
windshear flights; this particular
case was catalogued as event
#142, during which in situ F-factor
approached the alert threshold of
F=0.105, and showed good
correlation with the observed
change in along-track windspeed
(bottom).
MICROBURST PENETRATION
FLIGHT DATA, 17 JUN 91
0.20 ........
0.t50. I0
i 0.05
0.00
-0.05
-0. I0
0 10 20 80 40 50 80 ?0 80 90 lOOilO
8O
i '°100
-10
-20
.,.,.,.,.,.,.,._.,.,.j
- --Ilong-trlck An _ n_ J_k. -J
• \/
.,. .,.,)::.,,,,,. ]
0 I0 20 80 40 50 80 "tO 80 90 100110
TIME, seconds
i i i ii ii i i i
MICROBURST PENETRATION
FLIGHT DATA, 17 JUN 91
Data shown is for microburst
penetration, event #143, with a
peak in situ F of O.167. Along-track
and vertical wind time histories
show characteristics of passing near
the core of a microburst.
0.10
0.05
0.00
-0.05
z
-0.10
0
• I . l . I • I . l . l . l . l . l . I I I I
10 20 30 40 50 60 70 80 90 100 110 120
Isi.,.,.,. ,.,.,.,.,.,.,.,.
i. F _=long-track _l_lt../1.
10 ---vertical _ "-_/I
5/ .- ,_/"" ...
-10
0 10 20 30 40 50 60 70 80 90 100 110 120
TIME, seconds
Data shown is for microburst
penetration, event #97. In this case,
in situ F peaked at about 0.05,
though along-track wind shows a
general headwind-to-tailwind trend.
The time scale of this event shows
that the in situ algorithm is tuned to
windshear that is hazardous to the
airplane's climb performance,
whereas this event was over a
longer time scale (or distance), and
as such was not a hazard to the
airplane. The smaller-scale
fluctuations in along-track wind
(period of about 10 sec) are evident
in the in situ F-factor plot (between
t=75sec and end of run).
53
MICROBURST PENETRATION
FLIGHT DATA, 20 JUN 91
0.15 I. " , . , • , . , • , • , • , • , • , . , • , •
l: O numeric, 3.ucond av_ago
13I tl I" _ln |ltu (airplane data) 'J
.... f - - .filtered wind derivative _,_o oo
o 2 .
.0.10e . , . , . , . * . , . , • , • , . ' . = • ' •
0 10 20 30 40 50 60 70 80 90 100 110 120
15. • , • , • , • , • , • , • , • , • , . , . , •
-10
-15
-20 ' "
0 10 20 30 40 50 60 70 80 90 100 110 120
TIME, seconds
To demonstrate how in situ F and
wind-derived F correlate in-flight, F
was computed from aircraft-
measured along-track winds, and
differentiated with a gust-rejection
filter identical to the one used in the
in situ algorithm. This is plotted
along with the horizontal portion of
in situ F-factor (top plot), and an
unfiltered numerical differentiation of
averaged along-track wind (wind
data was averaged over 3-seconds,
then differentiated). All three curves
show very similar characteristics,
indicating that F-factor from the
in situ algorithm is nearly equivalent
to the along-track wind derivative.
Data shown is from event #142.
MICROBURST PENETRATION
FLIGHT DATA, 20 JUN 91
" I " | " I " I " I " | " I " I " I " I " I "
0.15 j: O O numerlc, 3-lee avg.
i: ._ _ln Iltu (airplane data)
0.10 _- , i_ - - -filtered wind derivative
T', o o,, J I-,.%='v& o
-0.05
-0.10 t, i , , • , • , • , . , - ' • ' . ' ' 'C" '
0 10 20 30 40 50 60 70 80 90 100 110 120
Same analysis method as previous
case, for event #143.
30.. , . , • , • , • , • , • , • l • , . , • , -
20
15
! '°50
-5
-10 [ = _ " = " = ' i , i , , • = • i , , • _ •
0 10 20 30 40 50 60 70 80 90 100 110 120
TIME, seconds
54
MICROBURST PENETRATION
FLIGHT DATA, 17 JUN 91
0.15 . , . , . , . , . , . , . , . , . , . , . o .0 numeric, 3-seoond aversge
I O.10 _n sltu (adrplamodais)
- - .filtered wlnd dodvltlve 0 0
0.05 O O
9 " o
0.00
-0.05
-0.10
0 10 20 30 40 50 60 70 80 90 100110 120
Same analysis method as for
previous case, for event #97.
15 " I " I " I " I " I " I " I " I " I " I " I "
.J lO
l,
o
"100 10 20 30 40 50 60 70 80 90 100110120
TIME, seconds
L RITHMPERF RMAN E T DATE
•OVER 100 FUGHT HOURSCOMPLETED
• APPROXIMATELY320 TAKE-OFFSAND LANDINGS
• NO NUISANCEALERTSGENERATED
•ALERTSGENERATEDDURINGMICROBURST
PENETRATIONSCONRRMEDBY GROUNDRADAR
•IN SITU HAZARDINDEXCONRRMEDBY WIND
MEASUREMENTS
The in situ algorithm's performance is summarized as shown. The algorithm has
operated on NASA's B737 for over 100 flight hours, included over 320 take-offs and
landings. No nuisance alerts were generated during low-level flight (below 1400'AGL),
which included flight in convective weather, gust fronts, and aggressive maneuvering;
alerts were generated during microburst penetrations, and confirmed by an
independent measurement (ground radar); analysis of in situ hazard index
measurement showed that it compared well with hazard index from measured along-
track wind.
55
SUMMARY
OBJECTIVES MET
• VAUDATED IN SiTU ALGORITHM AS MEASUREMENT
STANDARD FOR FORWARD.LOOK SENSOR EVALUATION
• DEMONSTRATED OPERATIONAL UTILITY
DESIGN REQUIREMENTS MET
• MINIMIZED AIRCRAFT MANEUVER4NDUC:ED ERRORS
IN HAZARD INDEX
• MINIMIZED EFFECTS OF TURBULENCE AND
NON-HAZARDOUS A'IMOSPHERIC MOTIONS
• STANOARD SENSOR IMPLEMENTATION
Results can be summarized by re-stating objectives and design requirements, which
were satisfied as originally set forth.
I I
56
NASA Wind Shear Flight Test In Situ Results
Questions and Answers
Q: Pete Sinclair (Colorado State University) - I think you might want m be a little cautious
about estimating the total F-factor from just the long track winds. Our flight measurements
indicate that the vertical term can be as large or larger than the horizontal component and that can
throw the F-factor to values above 0.15. Yours looks like that is suppressed quite a bit in the
traces you have shown us.
A: Rosa Oseguera (NASA Langley) - Maybe there is a little bit of a misunderstanding. The
overall F-factor that we were showing; the first one I showed, is a total F-factor. We are
including the vertical tern1 in there. Tile last slides that I showed where strictly for comparison
purposes with the along-track winds. In those slides I was just using the horizontal portion of the
F-factor to compare with. That is really all that we are computing from along-track winds. For
the purpose of comparing with the forward-look sensors and for providing the alert, the total
F-factor was used and that inclt,ded the vertical term. In fact, that was shown on the block
diagram. I just did not clearly point it out. The third term that was computed there was the
vertical part of the F-factor.
Q: Pete Sinclair (Colorado Slate University) - How do you measure the vertical component?
A: Rosa Oseguera (NASA l,angley) - It is co,nputcd from the difference between inertial
flight-path angle and airmass flight-path angle, and groundspeed and airspeed. Roland did you
want to expand on that'?
Roland Bowles (NASA l,;mgley) - The whole point is that we want to reject certain scales of
motion. This measurement is the difference between the ainnass and the inertial flight-path
angles. This was a fourteen knot peak downdraft in that microburst. When you look at the
airplane performance loss the In Situ system peaked out at about fourteen hundred feet per
minute, which is about fourteen knots. In other words, that was the measurement of that
microburst.
Pete Sinclair (Colorado Slate University) - What 1 am saying Roland, is that your system may
not be seeing all of the vertical term?
Roland Bowles (NASA L'.mgley) - We don't want it to see all of the vertical term. We don't
want small scale turbulence to trip the system. We are not making a wind measurement, we are
making a total energy change measurement on the airplane. That is what is hazardous to the
airplane.
Pete Sinclair (Colorado State University) - But that vertical term is part of the total hazard to
the airplane.
Roland Bowles (NASA Langley) - Sure, at the right scale. This was a small scale microburst.
The vertical channel there shows you how the vc,'tical term is estimated. Notice, we are not
making wind measurements and processing winds. We are pulling from the backbone sensors on
57
anairplane,theaccelerometersand air-data system. We are not making a wind measurement and
then processing the winds. You do not see winds anywhere in there. That's the key.
Q: Jim Evans (MIT) - There is a different issue which ! think one has to be concerned about
and that is the altitudes at which this testing was done. We know that some microburst have big
thick outflows and some of them have much stronger outflows near the surface. We will be
showing examples of that later in the conference. One of the questions that comes up is most of
this testing was done at the minimum altitude of 1,000 feet, and yet in the context of the guidance
we had for TDWR_LWAS users group, that is the altitude at which people start to get
concerned about Wind Shear. One of the questions that would come up is whether the agreement
would be as good if you flew down at lower altitudes were we see much more evidence of strong
pitching moments. If you look at the Dallas/Fort Worth crash traces for example, you see very
strong eddies and things that were definitely effecting the plane at low altitude. So one of the
questions I think you would have to ask is, to what extent can you extrapolate the measurements
here, at about 1,000 feet altitude, dow,1 to much lower altitudes?
A: Roland Bowles (NASA Langley) - That is a gored question. The evidence shows that the
total energy change to the airplane stays about the same, because the vertical wind component
diminishes as a function of altitude were as the horizontal gradient may peak at about 80 to 100
meters, but the overall performance loss is about the same; at normal approach speeds. We were
making measurements at the point at which we were testing our sensors. We are not trying to
characterize the relative threat level, we were making the in Situ measurement to use as a
standard of goodness to comp:tre to the predictions made by the remote sensors.
Dan Vicroy (NASA Langley) - The other point I would like to make is that the F-factor is a
performance measurement and in reference to your com,nent about the pitching moment, that is
more of a handling qualities problem and the F-htctor is not going to reflect that at all.
Roland Bowles (NASA Langley) - Again, it is a scale of motion you are trying to identify.
Pat Adamson (Turbulence Prediction Syslems) - This is just a point of clarification. The
F-factor that you guys are talking about is slightly larger because of the airspeed you were flying.
The airspeed plays a big factor in the magnitude of F.
58


NASA wind shear flight test in situ results

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