Brownout Situational Awareness Upgrade (BSAU)
Development and Integration on the CH-47D and UH-60L
Helicopters
Major Charles S. Walls IV, Mr. Stephen M. Paris, Mr. John A. Wood, Mr. Nathan Scoggin
US Army Aviation Applied Technology Directorate
Research Development and Engineering Command (RDECOM)
Fort Eustis, Virginia USA
Figure 1
Abstract
The Aviation Applied Technology Directorate (AATD) located at Fort Eustis, Virginia, in concert with both the
CH-47 and UH-60 Program Manager’s Offices in Huntsville, Alabama, designed and integrated a Brownout
Situational Awareness system onto the CH-47 and UH-60 helicopters to aid pilots in degraded visual
environments due to brownout conditions. The purpose of the effort was to reduce aircraft mishaps and
incidents caused by blowing sand which often leads to spatial disorientation during landings in a desert
environment. The concept was to develop a “kit” for the aircraft that would generate Embeded GPS/INU
symbology onto a cockpit display to allow precise aircraft control without out-the-window visual reference.
Both pilot and copilot Horizontal Situational Indicators (HSIs) were replaced with Rockwell Collins Multi
Function Displays (MFDs) which contained an HSI page and three BSAU pages as well as several engineering
pages which enabled the test pilots to vary damping ratios of each piece of MFD symbology. The symbology
set was also evaluated on EFW’s Flat Day HUD display. Testing was initiated in October 2003 and was
conducted in four phases. Phase one focused on developing the BSAU symbol set. Phase two was a qualitative
assessment of the symbol set. Phase three was actual brownout landing conducted at Yuma Proving Grounds.
Phase four was a user assessment of the developed system. Testing was completed in March 2005.
Background
In recent years many aircraft mishaps during desert operations have been attributed to loss of spatial orientation
during brownout landing conditions. When landing in a blowing sand environment, loss of outside visual
reference often leads to unintended aircraft drift during landing and/or taking off causing aircraft roll-overs. In
an effort to reduce brownout related mishaps, PM Cargo and PM UH joined together in an effort to field a
system that would provide situational awareness during brownout landings. The joint PM team brought the
Aviation Applied Technology Directorate (AATD) on board to develop, integrate and test a BSAU on both the
CH-47D and UH-60L aircraft. Early development focused on integrating MFD displays with the existing
aircraft Doppler. Further integration of sensor information from MFD through ANVIS-7 HUD SDC on to EFW
Flat Day HUD display allowed for evaluation of symbology set on both the MFD and Day HUD display. It was
determined that the Doppler input did not give the fidelity required to drive the symbology precisely enough for
operations in a degraded visual environment when landing and taking off. Development then shifted to
integrating an EGI onto each aircraft to drive the symbology and provide the accurate acceleration cues to the
pilot required for precision low speed operations. Figure 2 shows BSAU system architecture.
EGI
EGI
On/Off
Switch
4 to 1
GPS
Antenna
Splitter
ASN-128B
Doppler
Zeroize
Switch
28VDC, 3 A
ARINC
575
Circuit
Breaker
PDP
Circuit
Breaker
PDP
ARINC
429
28VDC, 1 A
MFD255M
Circuit
Breaker
PDP No. 1
MFD255M
ARINC
429
ARINC
429
28VDC, 7.5 A
CH-47D
New 5 position HUD Switch on
Copilot's Thrust Control
ARINC
429
HSI Mode
Select
UH-60 Dual Function GoAround Button
28VDC, 7.5 A
CH-47D - New 5 position
HUD Switch on Copilot's
Thrust Control
HSI Mode
Select
HUD SDC
APN-209
RADALT
Day
HMD
VOR
Circuit
Breaker
PDP No. 2
Day
HMD
UH-60 Dual
Function Go-Around
Button
ASN-43
COMPASS
ADF
Figure 2
Once integration of the EGI was completed, testing began which focused on optimizing each piece of
symbology to find a balance between providing accurate cues and damped enough to prevent pilot induced
oscillations. Figure 3 shows the optimized symbology set.
Figure 3
Both quantitative and qualitative data was collected to quantify the system characteristics as well as evaluating
pilot performance. Data was used toward system qualification.
Objectives
The objective of this test was to evaluate and demonstrate the functionality of an Interim Brownout Solution
system as installed on the CH-47D and UH-60 A/L helicopter by providing a system which:
1.
2.
3.
4.
Allowed successful degraded visual environment DVE take-offs and landings
Minimized lateral drift and descent rate at touchdown to prevent aircraft damage
Prevented spatial disorientation by eliminating pilot induced oscillations (PIO)
Allowed controlled approach angle to selected touchdown point
Testing and Results
General
Although both the CH-47D and UH-60 were tested , representative CH-47D data is presented below.
Phase I – Qualitative Results
Prior to all symbology assessment testing, a functionality/software regression check was conducted by checking
each symbol in flight to ensure proper functionality. The Acceleration Cue was assessed for latency and refresh
rate by performing step inputs in each flight control axis and qualitatively assessing symbology response. An
incremental build-up in control input magnitude, from controls centered to no greater than 2 inches in ¼ inch
increments, were conducted. Control fixtures were used using procedures outlined in United States Naval Test
Pilot School (USNTPS) Flight Test Manual (FTM) 107. It is important to note that the step inputs were to
characterize the symbology response not the aircraft control response therefore maximum rates in a specific
control axis were not targeted. Accuracy of the velocity vector, vertical speed indicator, and heading tape was
also assessed by comparing symbols with other aircraft systems or fixed visual reference points while
conducting the following: low airspeed checks forward, aft, and laterally in 5 knot increments, climbs and
descents at 20, 60, 100, and 120 knots at 500 and 1000 feet per minute, and hovering turns at 5, 10, 15, and 20
degrees per second. Data was recorded on hand held data cards, a synchronized video system, an ARINC data
recorder, and the Advanced Range Data System (ARDS) data recorder. The ARDS data was considered “truth”
data for analysis purposes. Figures 4, 5, and 6 show representative data plots of symbology performance for
lateral velocity, vertical velocity, and heading during low airspeed flight, climbs and descents, and hovering
turns, respectively. Acceleration is still being evaluated and is not presented below. In figure 4, data indicated
that there was no significant latency in lateral velocity between the EGI sensor and MFD/HUD display. Digital
ground speed readout on each display, the Doppler digital groundspeed readout, and the velocity vector
symbology presentation correlated. Lateral velocity was assessed as accurate.
Figure 4
Lateral Velocity Correlation
In figure 5, data indicates that there was no significant latency in vertical velocity between the EGI sensor and
MFD/HUD display. Vertical velocity was assessed as accurate.
Figure 5
Vertical Velocity Correlation
In figure 6, data indicates that there was no significant latency in yaw rate between the EGI sensor and
MFD/HUD display. Yaw rate was assessed as accurate.
Figure 6
Yaw Rate Correlation
In figure 7, the resultant of longitudinal and lateral position drift from a known hover point is displayed and data
indicates that there was no significant latency in position between the EGI sensor and MFD/HUD display.
Position information was assessed as accurate.
Figure 7
Hover Point Drift Correlation
Phase II – Qualitative Results
Phase two focused on assessing the pilot’s ability to perform specific maneuvers while flying with symbology
only to simulate brown-out conditions. Maneuvers were selected from ADS-33E as well as the CH-47D
Aircrew Training Manual and modified where appropriate to make pertinent to brownout environments. Three
subject experimental test pilots flew maneuvers from the co-pilot station with the cockpit field-of-view
obstructed by card board over the co-pilot windshield and chin bubble, forcing the subject pilot to fly using the
symbology only. A safety pilot, with an unobstructed field-of-view, occupied the pilot station. Handling
Qualities Ratings (HQRs) were assigned by each test pilot IAW the procedures contain in the USNTPS FTM
107 following each maneuver to characterize the resultant aircraft handling qualities when flying a specific
system. The Visual Cue Ratings (VCR) were determined to be “Good” as defined in ADS-33E in that the
displayed symbology provided cues which enabled the pilot to make aggressive and precise corrections with
confidence. The safety pilot determined if desired or adequate performance criteria was met using visual
ground reference points. Maneuvers were selected to represent what is reasonably expected for a pilot to
perform while, landing, taking off, or recovery from a brown-out condition as well as to force the pilot to
use/evaluate each symbol in the symbology set. The maneuver set was flown with the MFD being driven by
the EGI, the HUD being driven by the EGI, the MFD at heavier gross weights, and the MFD with the EGI in a
degraded mode (GPS signal removed). A baseline target aircraft gross weight of 32,500 pounds was flown,
and heavier gross weights of 40,000 and 48,000 pounds were assessed (spot checked) to ensure that the heavier
aircraft gross weights did not noticeably affect symbology performance due to changed aircraft handling
qualities. Overall, the displays provided visual cueing, which allowed pilots to obtain level 2 handling
qualities. It was noted that there was little change in pilot performance between displays (MFD or Flat Day
HUD) or while in the “degraded” mode of operation. Pilot performance did improve as pilot’s gained
experience flying the symbol set. The maneuvers flight tested were:










Hover
Landing (from hover)
Hovering Turn
Vertical Maneuver
Lateral
Brownout Lateral Recovery
Slope Landing
Takeoff
Approach
Go Around
Table 1 contains the participating test pilot’s experience level.
Table 1
Pilot Experience
Pilot
Total Flight Hours
CH-47D Hours
1
2
3
1700
3500
3100
100
200
2300
HUD/Symbology
Hours
50
800
500
Table 2 contains the HQRs from phase 2 testing for MFD and Flat Day HUD at light, medium, and heavy gross
weight configurations and in fully operational as well as degraded sensor modes.
Table 2
Phase 2 Handling Qualities Ratings
Pilot
Hover
1
2
3
Avg.
5
5
5
5
Hover
1
2
Avg.
5
5
5
Hover
Medium
Heavy
4
5
Landing
(hover)
5
4
3.5
4.1
Hover Turn
Landing
(hover)
4
4
4
Hover Turn
Landing
(hover)
4
4
5
5
5
5
6
5
5.5
MFD Degraded/INU Only
Vertical Slope Takeoff(1)
Man
Norm/ITO
6
---4/5
5
4.5
4/5
5.5
4.5
4/5
Landing
Go-Around
5
5
4
4.6
5
4
3
4
Landing
Go-Around
5
5
5
5
4.5
4.75
MFD/Full Up Medium and Heavy Weight (Pilot 2)
Hover Turn Vertical Slope Takeoff(1)
Landing
Man
Norm/ITO
5
5
6
4/5
5
4.5
5
5
5/4
4
Phase 2 HQRs HUD/Full Up
Landing
Hover Turn Vertical Slope Takeoff (1)
(hover)
Man
Norm/ITO
5
4.5
5.5
6
4.5
5/4
5
4
4
5.5
4.5
4/4
5
4
6
6
7.5
4/4
5
4.2
5.2
5.8
5.5
4.3/4
Notes: (1) Normal Takeoff and Instrument Takeoff.
Hover
1
2
3
Avg.
MFD/Full Up
Vertical Slope
Takeoff(1)
Man
Norm/ITO
5
6
4/5
5
5
3/5
5
4
4/4
5
5
3.6/4.6
Go-Around
5
4
Landing
Go-Around
5
4
5.5
4.8
4
5
4
4.3
Lateral
Recovery
5
4
4
4.3
Lateral
Recovery
5
5
5
Lateral
Recovery
4
5
Lateral
Recovery
4
5
5
4.6
Maneuvers Flown During Phase II
Hover- Altitude control drove the HQRs for the hover task. Very small thrust control inputs, +/- 1/16 inch,
resulted in large altitude changes, +/- 5 feet, which made precise altitude control difficult. The difficulty in
altitude maintenance was most likely due to the large aircraft power margin which increases thrust sensitivity.
Although the aircraft altitude hold was not used during the evaluation portion of testing, radar altitude hold
reduced pilot workload during practice hover tasks. It was also helpful to leave the trust control trim engaged
and use pressure/counter pressure against the trim to prevent larger than desired altitude changes when
hovering. Generally, adequate performance was obtained requiring considerable pilot compensation. One
finding was that pilots use radar altitude hold during hover tasks in brownout environments to reduce pilot
workload and reduce the chances of spatial disorientation. Also, it was noted that pilots should leave the
thrust control trim engaged when hovering in a brownout environment and use pressure/counter pressure
against the trim to prevent larger than desired altitude changes.
Landing from a hover- Rate of descent control and position maintenance drove the HQRs for the “landing
from a hover” task. It was helpful to touchdown with slight forward movement to aid in preventing aircraft
lateral drift. Generally, desired performance was obtained requiring moderate pilot compensation. One
finding was that pilots leave the thrust control trim engaged and use pressure/counter pressure against the trim
to prevent larger than desired altitude changes when hovering. Another finding was that aircraft touchdown
with slight forward movement will aid in preventing lateral drift when landing from a hover.
Hover Turn- Altitude maintenance drove the HQRs for the hover turn task. Very small thrust control inputs,
+/- 1/16 inch, resulted in large altitude changes, +/- 5 feet, which made precise altitude control difficult. The
increased pilot compensation for altitude control can be attributed to the large aircraft power margin, as stated
in the “hover” paragraph above. Generally, adequate performance was obtained requiring considerable pilot
compensation. It was noted that pilots should leave the trust control trim engaged and use pressure/counter
pressure against the trim to prevent larger than desired altitude changes when hovering.
Vertical Maneuver- Altitude capture and rate of ascent/descent control drove the HQRs for the vertical
maneuver task. Due to the required altitude change for this maneuver, the difficulty in maintaining rates of
ascent and descent and capturing target altitude were exacerbated by predicting when to adjust thrust control
inputs. Small thrust control inputs during ascent/descent to arrest the ascent/descent resulted in capturing the
targeted altitude , +/- 5 to 7 feet. Generally, adequate performance was obtained requiring considerable pilot
compensation.
Sloped Landings- Rate of descent control and position maintenance drove the HQRs for the “landing from a
hover” task on sloped terrain. The increased pilot compensation for rate of descent control can be attributed to
the large aircraft power margin, as stated in the “hover” paragraph above. The resultant rate of descent from a
given power reduction was non-repeatable, often resulting in unpredictable aircraft to ground contact. The
unpredictable ground contact coupled with lateral drift resulting from difficulty in maintaining position will
result in uncommanded roll deviations upon ground contact which could lead to increased chances aircraft
rollover during slope operations. One finding was that slope landings no greater than 5 degrees should be
attempted when flying aircraft with the symbology as the sole reference source.
Takeoffs- Standard takeoffs and instrument takeoffs (ITO) were performed. Lateral drift drove the HQRs for
the takeoffs. Generally, desired performance was obtained requiring moderate pilot compensation.
Landings- Landings to a specific landing area using the symbolgy as the sole reference required training
which ranged from 2 to 4 hours. It was determined that the technique of initiating the approach from 50 feet
and 35 to 40 knots ground speed allowed for the most controlled approach to landing. Generally, desired
performance was obtained requiring moderate pilot compensation. One finding was that initiating approaches
from 50 feet and 35 to 40 knots ground speed. Another finding was that the Directorate of Evaluations and
Standards (DES) determine how much training is adequate for pilots to safely conduct landings using the
BSAU.
Go Around- Generally, desired performance was obtained requiring moderate pilot compensation.
Lateral Recovery- The lateral recovery maneuver was evaluated to simulate recovery from spatial
disorientation during brownout conditions. Large lateral control inputs, +/- 1/2 inch, to arrest lateral velocity
and capture a hover point resulted in small lateral position changes, +/- 5 feet, which made precise position
capture difficult Generally, desired performance was obtained requiring moderate pilot compensation.
Phase III- Qualitative Results
Phase three focused on performing actual brown-out landings and takeoffs to determine the effects of blowing
sand on aircraft systems which drive symbology. The cockpit was in a mission representative configuration, no
black-out card board. The landings and takeoffs were conducted by two experimental test pilots during day,
night, and while wearing NVGs. NVG compatibility of the MFD-255 was also as well as Human Factors
(HFE) considerations were also assessed.
(1) Actual Brownout Landings- A total of 20 actual brownout landings were conducted at Yuma Proving
Grounds, AZ using the MFD, Day HUD and NVG HUD during both day and night VMC. Three separate
pilots performed the brownout takeoffs and landings. It was noted that the symbology of the Day HUD was not
bright enough during bright sunlight conditions. The Day HUD display was made brighter following Phase III
testing and was assessed as bright enough to provide adequate cues during bright sunlight conditions. There
were no other system anomalies noted during the takeoffs and landings. One go-around was performed during
the test due to excessive lateral drift just prior to touchdown. The lateral drift was noted and announced by the
safety pilot at which time the pilot flying the aircraft made a successful go-around. Aircrew coordination aided
in successful takeoffs and landing by having the flight engineer announce when the dust cloud was at the tail of
the aircraft and having the pilot not on the controls calling out airspeed, altitude, vertical speed and lateral drift.
The pilot flying the aircraft transitioned to the symbology when the flight engineer announced “dust cloud at the
tail” which gave the flying pilot time to establish a MFD cross-check prior to entering the dust cloud. All other
internal aircraft communication was kept to a minimum to enable prompt communication between the pilot on
the controls and the safety pilot who was monitoring aircraft conditions via the MFD. Figure 5 and 6 displays
photo documentation of the brownout landings for CH-47D and UH-60L, respectively.
Figure 5
CH-47D Brownout Landing Sequence
Figure 6
UH-60 L Brownout Landing Sequence
(2) NVG Compatibility and HFE Considerations- The NVG compatibility and HFE assessment was an
ongoing qualitative pilot evaluation as well as a quantitative evaluation conducted by Dr. Bill McLean from
USAARL and Dr. Tom Frezell from USAATTC. The quantitative assessment was conducted after nautical
twilight at the Mid-East test course at Yuma Proving Ground, Arizona. Following the culmination of the
flight/qualitative portion of the assessment, the CH-47, serial number 87-70077, was parked at Laguna Army
Airfield away from artificial lighting sources. The MFD was evaluated using both photopic photometrics and
ANVIS radiance to determine if there were significant differences between the brown-out display and other
illuminated crewstation displays and controls. A subjective evaluation was also conducted to determine display
readability under “dark” conditions. A Minolta LS-100 photometer was utilized to measure photopic luminance
of the electronic brown-out display and other nearby light displays to determine display balance between the
various displays. The Minolta photometer was then modified utilizing an adapter and a PVS-14 NVIS
intensifier tube in order to measure NVIS radiance of various lighted controls and displays. The obtained
values were then compared with each other to determine if substantial differences existed. Pilots that flew the
modified CH-47 were asked for their comments on the legibility and display brightness of the electronic brownout display immediately after their unaided and aided night flights. A color-balanced light source was utilized to
illuminate the electronic display to 10,000 foot-candles in order to evaluate daylight readability. Photopic
measurements of the brown-out display indicated that it was well-balanced with other crewstation flight
displays (attitude indicator, vertical speed indicator, heading indicator). NVIS radiance measures provided
fairly uniform readings except in the case of the “transmission oil pressure selector switch” and the
“transmission oil temperature selector switch.” These selector switches were 10 times brighter (NVIS radiance)
than any other flight displays or controls. Several of the pilots indicated that the brightness of the transmission
oil temperature/oil pressure scan switches were quite noticeable and distracting and should be reduced for
ANVIS flight. The brown-out display was considered to be NVIS acceptable and did not produce any
“blooming” in the pilot’s ANVIS when viewed directly through the ANVIS (cockpit displays are not viewed
through the ANVIS by the pilots but are viewed under the ANVIS). The tested electronic display did not
produce any visible windscreen reflections. The brown-out display was considered legible during all flight
conditions (day and night) and was readable under 10,000 foot-candles direct illumination.
Conclusion
The developed symbol set displayed on the MFD and HUD enabled the pilot to conduct brownout takeoffs and
landings and is satisfactory. It was noted that increased time flying the symbology resulted in better
performance of each test pilot. One finding is that the Directorate of Evaluations and Standards (DES)
determine how much training is adequate for pilots to safely use the BSAU as well as develop specific
procedures required for executing brownout landings. The following procedures were used during BSAU
testing to execute successful landings :
1.
2.
3.
4.
5.
6.
7.
8.
Ensure all windows and doors are closed
Initiate approach at 50 Feet AGL and from 40 to 35 knots ground speed.
Pilot on the controls establish a descent and deceleration aiming for the intended point of touchdown.
Flight Engineer makes a “dust at the tail “call and any other lateral drift call which he determines to be
excessive.
Pilot on the controls transitions to the MFD/HUD when the “dust at the tail” call is made.
The non flying pilot monitors MFD and calls excessive deviations in airspeed, rate of descent, or lateral
drift.
Any crewmember calls for a go-around should excessive lateral drift or rate of descent develop.
Aircrew communication should be kept to a minimum so that only critical calls can be communicated by
any crewmember.
Although symbol set displayed on both MFD and Day HUD provided adequate cues, the Day HUD reliability
became questionable in that all of the 8 Day HUDs supplied for testing failed during testing. Findings show
that improvement of reliability of the Day HUD is required.
Major Charles S. Walls IV and Mr. Stephen M. Paris, Mr. John A. Wood, are experimental test pilots at the
Aviation Applied Technology Directorate (AATD) of the Research Development and Engineering Command
(RDECOM) at Ft Eustis. Virginia. Mr. Nathan Scoggin (USNTPS Class 120) is an electrical engineer and flight
test engineer at AATD.