This presentation shows the latest analysis results of the DAA airborne radar's field of view analysis for high and medium speed UAs

McDonough, Kevin

Wu, Minghong G.

English

NASA Technical Reports Server

Bihrle Applied Research Inc. | 81 Research Drive, Hampton, VA 23666 USA | +1 757.766.2416 | bihrle.com
Prepared for
DO-366 Appendix-C&D Update for High and 
Medium UA Speed Ranges
RTCA F2F
Kevin McDonough kmcdonough@bihrle.com
Gilbert Wu gilbert.wu@nasa.gov
https://ntrs.nasa.gov/search.jsp?R=20200000600 2020-03-11T12:33:07+00:00Z
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• DO-366 Appendices C and D document analyses of the 
air-to-air radar (ATAR)’s field of regard (FOR) in terms of 
alerting times before a loss of DAA well clear (LoDWC)
• These analyses are to be repeated because
• SC-228 Phase 2 work selects an alternative non-cooperative 
DWC
• 2200 ft horizontal distance
• 450 ft vertical distance
• The one radar category in DO-366 will be expanded to 3 
categories characterized by varying UA speed ranges
• High speed UA from 100 to 291 KTAS
• Medium speed UA from 100 to 200 KTAS
• Low speed UA from 40 to 110 KTAS (not analyzed in this work)
Background and Objectives
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• Radar Declaration Range (RDR) Requirement (computed by Adaptive Aerospace Group and NASA)
• It is dependent on:
• The bearing angle of the intruder aircraft to the ownship UAS
• The size of the intruder aircraft which is based on the intruder aircraft speed
• The speed of the ownship UAS
• Assumed FOR angular ranges: ± 110° azimuth, ±15° altitude
• Radar Closest Performance Range (RCPR) Definition
• 4000 ft
• Track declaration time 
• 15 seconds track delay when the intruder enters the FOR within the RDR
ATAR Field of Regard (FOR) Requirements
Intruder Bearing Angle RDR Correction FactorSmall Medium Large
𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚 < 𝟑𝟑𝟑𝟑 1 1 1
𝟑𝟑𝟑𝟑 ≤ 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚 < 𝟔𝟔𝟑𝟑 0.59 0.67 0.76
𝟔𝟔𝟑𝟑 ≤ 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚 < 𝟗𝟗𝟑𝟑 0.33 0.51 0.66
𝟗𝟗𝟑𝟑 ≤ 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚 < 𝟏𝟏𝟏𝟏𝟑𝟑 0.17 0.25 0.40
Intruder Bearing Angle RDR Correction FactorSmall Medium Large
𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚 < 𝟑𝟑𝟑𝟑 1 1 1
𝟑𝟑𝟑𝟑 ≤ 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚 < 𝟔𝟔𝟑𝟑 0.70 0.78 0.84
𝟔𝟔𝟑𝟑 ≤ 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚 < 𝟗𝟗𝟑𝟑 0.39 0.59 0.76
𝟗𝟗𝟑𝟑 ≤ 𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚 < 𝟏𝟏𝟏𝟏𝟑𝟑 0.20 0.30 0.45
High Speed UAS Medium Speed UAS
Intruder Size Nominal RDR 
[nm]
Small (𝑠𝑠𝑖𝑖𝑖𝑖𝑖𝑖 ≤ 100 KTAS) 4.9
Medium (100 < 𝑠𝑠𝑖𝑖𝑖𝑖𝑖𝑖 ≤ 130 KTAS) 5.2
Large (130 > 𝑠𝑠𝑖𝑖𝑖𝑖𝑖𝑖 KTAS) 5.7
Intruder Size Nominal RDR 
[nm]
Small (𝑠𝑠𝑖𝑖𝑖𝑖𝑖𝑖 ≤ 100 KTAS) 4.1
Medium (100 < 𝑠𝑠𝑖𝑖𝑖𝑖𝑖𝑖 ≤ 130 KTAS) 4.5
Large (130 > 𝑠𝑠𝑖𝑖𝑖𝑖𝑖𝑖 KTAS) 5.0
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• 1 million encounters are created overlaying NASA UAS trajectories with VFR trajectories sampled from 
MIT Lincoln Lab’s uncorrelated encounter model
• Weighted distributions represent the frequency at which the encounters actually occur
• Trajectories with high ownship speeds occur infrequently in the original NASA UAS track data; trajectories with 
lower ownship speeds have longer track durations
Full Encounter Set
2000 4000 6000 8000 10000
Altitudes (ft)
0
0.02
0.04
0.06
0.08
0.1
0.12
Fr
eq
ue
nc
y
Ownship
Intruder
Weighted Altitude
50 100 150 200 250 300
Airspeed (knots)
0
5
10
15
Fr
eq
ue
nc
y
10 4Ownship Airspeed
0 50 100 150
Speed (kts)
0
2000
4000
6000
8000
10000
12000
14000
Fr
eq
ue
nc
y
Intruder Airspeed
50 100 150 200 250
Speed (kts)
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Fr
eq
ue
nc
y
Ownship
Intruder
Weighted Airspeed
0 2000 4000 6000 8000 10000
Altitudes (ft)
0
2
4
6
8
Fr
eq
ue
nc
y
10 4Ownship Altitude
0 2000 4000 6000 8000 10000
Altitudes (ft)
0
0.5
1
1.5
2
Fr
eq
ue
nc
y
10 4
Intruder Altitude
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• The 1 million encounters were filtered to a set that includes only 
those encounters that are strictly within the speed bounds for High 
Speed UAS
• 100 KTAS to 291 KTAS
• This includes all Medium Speed UAS encounters as well
• 100 KTAS to 200 KTAS
• High Speed UAS set includes 247,827 encounters
• Medium Speed UAS set includes 157,299 encounters
Encounter Set Stats
High Speed UAS (247,827 encs) Medium Speed UAS (157,299 encs)
# of 
Encs
% of Encs Weighted % 
of Encs
# of Encs % of Encs Weighted % of 
Encs
LoWC 79,949 32.26 3.98 48,480 30.82 3.79
NMAC 12,252 4.94 0.20 7,849 4.99 0.19
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• App Goal: Compare RDR Time Margin to corrective 
alert requirements
• Definition: time margin Δ𝑡𝑡 = 𝑡𝑡𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 − 𝑡𝑡𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑
• 𝑡𝑡𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 = the time of first loss of well clear (LoWC)
• 𝑡𝑡𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 = the time of track declaration
• Average corrective alert time: 55 seconds
• Late Alert time: 20 seconds
Appendix D Definitions and Goals
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High Speed LoWC Time Margin Data
• Green has a time margin of Δ𝑡𝑡 ≥ 55 𝑠𝑠
• Yellow has a time margin of 0 s ≤ Δ𝑡𝑡 < 55 𝑠𝑠
• Red has a time margin of Δ𝑡𝑡 < 0 𝑠𝑠
• This includes ALL of the data. All of the Red and many of the smaller valued Yellow data are 
intruders that entered the FOR below the RCPR (< 4000 𝑓𝑓𝑡𝑡).
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Appendix D Preliminary Results
𝚫𝚫𝚫𝚫 Bracket [s] High Speed UAS (79,949 total)
# of Encs % of LoWC
Encs
Weighted % 
of LoWC Encs
Δt > 55 69,555 86.99 95.1620 < Δ𝑡𝑡 ≤ 55 10,352 12.95 4.61
Δ𝑡𝑡 ≤ 20 42 0.05 0.22
𝚫𝚫𝚫𝚫 Bracket [s] Medium Speed UAS (48,480 total)
# of Encs % of LoWC
Encs
Weighted % 
of LoWC Encs
Δt > 55 41,092 84.76 86.4220 < Δ𝑡𝑡 ≤ 55 7,347 15.15 13.34
Δ𝑡𝑡 ≤ 20 41 0.08 0.23
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• Late alert % is very low. It appears that the RDR 
may be too conservative
• Possible differences due to 1.5 deg/s turn vs 3 
deg/s
• 3 deg/s results in RDR that is roughly 0.7-0.85 the RDR at 1.5 
deg/s
• Rounding up in the way RDR definition:
• Using worst case bearing across the bearing range (e.g. using 
0 deg bearing for all of 0 to 30 deg)
• Taking the largest RDR across ownship speed range
• Using 1.5 deg/s turn rate
• Rounding up at each stage may push RDR too far out
App D Preliminary Results Comments and 
Questions
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• App Goal: Determine effect of 15 second track delay when intruder 
enters FOR within RDR
• Definition: time margin Δ𝑡𝑡 = 𝑡𝑡𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 − 𝑡𝑡𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑
• We want to find the percentage (and weighted percentage) of LoWC
encounters entering the FOR below RDR that results in a Δ𝑡𝑡 ≤ 30
seconds
• For a encounter first observed within RDR, a 15 second delay is 
considered for track declaration time.
• We also want to ignore any cases below the RCPR
• RCPR defined as 4,000 ft horizontal distance
Appendix C Definition and Goals
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High Speed LoWC Time Margin Data When 
Intruder Entered FOR Within RDR
• Same color convention as before
• Removal of sub-RCPR FOR entrance data and only considering the cases where the intruder 
entered within the RDR.
• No more Red data.
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Percent of Sub-RDR Encounters Currently with 
the FOR relative to Δ𝑡𝑡 for High Speed UAS
• By Δ𝑡𝑡 = 30 seconds, nearly all of the Sub-RDR entrance encounters are within the FOR  
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Weighted Percent of Sub-RDR Encounters 
Currently with the FOR relative to Δ𝑡𝑡 for High 
Speed UAS
• These weights are calculated for only the subset of Sub-RDR Entrance encounters
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Appendix C Preliminary Results
Where the intruder entered 
the FOR
High Speed UAS (79,949 total)
# of Encs % of LoWC Encs Weighted % of LoWC Encs
Within RDR but above RCPR 3,642 4.55 6.57
Within RDR but above RCPR
with Δt ≤ 30 seconds (cases
impacted by 15 second track 
delay)
18 0.02 0.20
Below RCPR 40 0.05 0.06
Where the intruder entered 
the FOR
Medium Speed UAS (48,480 total)
# of Encs % of LoWC Encs Weighted % of LoWC Encs
Within RDR but above RCPR 2,852 5.88 6.68
Within RDR but above RCPR
with Δt ≤ 30 seconds (cases
impacted by 15 second track 
delay)
14 0.03 0.20
Below RCPR 39 0.08 0.06
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• There are some significant changes in percent 
values from the previous work
• E.g. previously, 3527 encounters (3.3%, 2.1% 
weighted) of LoWC events could be affected by 
15 sec delay where as current work suggests only 
18 (0.02%, 0.2% weighted) encounters of the 
current set are impacted.
• This could be explained by differences in the set 
and our analysis parameters (no 𝜏𝜏 factor, >100 
KTAS ownship, HMD is 2200 from 4000 last time).
App C Preliminary Results Comments and 
Questions
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Are the RDR Requirements and Definitions 
Suitable?
• Interesting cases to consider
• Entrance in to the RDR through any of the radial faces (like what is circled in red)
• What happens when the intruder enters the FOR at 1.01 × 𝑅𝑅𝑅𝑅𝑅𝑅 for a given bearing?
• Is there a different definition or functional version of RDR that might make sense (i.e. 
something without the range discontinuities)?
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Backup slides
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• Of the 3642 encounter entering the FOR below RDR
• 1566 are cases where the ownship is non-maneuvering 
(43.0% of below RDR encounters, 3.86% weighted for 
LoWC encounters)
• 1746 are cases where the ownship is 
climbing/descending (47.94%, 1.35% weighted)
• 180 are cases where the ownship is turning (4.94%, 1.23% 
weighted)
• 150 are cases where the ownship is both turning and 
climbing/descending (4.12%, 0.12% weighted)
Appendix C Preliminary Results Cont.
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All High Speed Detected LoWC Encounters
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High Speed LoWC Time Margins Compared to 
Mean Range Rate
It appears that the high valued LoWC time margin points (high on the vertical axis) have a low 
magnitude (i.e. a slow) mean closing speed. 


DO-366 Appendix-C&D Update for High and Medium UA Speed Ranges

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