Hange, Craig E.

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National Aeronautics and Space Administration
Aerodynamic Testing, Analysis, & Modeling of 
Powered-Lift
Craig Hange
From VTOL to eVTOL Workshop
May 24, 2018
https://ntrs.nasa.gov/search.jsp?R=20180003215 2019-08-31T16:35:06+00:00Z
National Aeronautics and Space Administration
Outline
From VTOL to eVTOL Workshop, May 24, 2018 2
• Powered-lift for VTOL flight (Non-Rotary Wing)
• Some of the past projects, programs, and facilities at Ames that we have 
used in VTOL / STOL research. Some of the multi-disciplinary research
– Aircraft Flight Testing - The X-14A, the Augmentor Wing Jet STOL Research 
Aircraft  (AWJSRA), Quiet Short - Haul Research Aircraft (QSRA), and V/STOL 
Systems Research Aircraft  (VSRA)
– Wind Tunnels Tests at The National Full-Scale Aerodynamics Complex (NFAC) 
including the 40 X 80 Foot Wind Tunnel, 80 X 120 Foot Wind Tunnel and 
Outdoor Aerodynamic Research Facility
– CFD - The “From Computation to Flight” the Computational Approach to 
Aeronautics Research
– Vehicle / Airspace / Environment Integration
• Summary, future work, and take away points
National Aeronautics and Space Administration
Powered-Lift for VTOL Flight
• Flight regime of “powered-lift” for VTOL applications.
– Size and velocity of the flow field
• ‘High’ disc loading. Low mass flow with high kinetic energy
– Vehicles with propulsion systems comprising of direct jets, ducted fans, or 
augmented jets
– In-ground-effect and out-of-ground effect show distinct and different flow 
field characteristics 
– A flow field whose “average” dynamic pressure (q) may not be relevant
– Mission profile:  Hover, transition, cruise, transition, and back to hover
• It is understood that using electric power changes many of the issues, 
especially hot gas ingestion, but most aerodynamic characteristics 
remain relevant
• “Are you sure you need to hover during take-off and landing?”
– Please consider “Short” Take-Off and Landing (STOL)
From VTOL to eVTOL Workshop, May 24, 2018 3
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VTOL ‘Wheel’
• A wheel of (mis)fortune
– Technically, vehicles were 
flown successfully
– ‘Misfortune’ is due to 
program issues and failure 
to identify real requirements
• Almost always found a 
5,000 foot runway 
somewhere to fly in and 
out was cheaper than 
hovering
– The technology is worthy of 
revisiting due to:
• Electric Propulsion
• Control Systems including 
Autonomy
• Advances in CFD, flow 
modeling, vehicle 
structural design process
• Missions have ‘true’ need 
to hover
From VTOL to eVTOL Workshop, May 24, 2018 4
www.vtol.org
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VTOL Flow Field – Effects
From VTOL to eVTOL Workshop, May 24, 2018 5
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The Ames VTOL / STOL Projects of the Past
• Some of them even before my time
From VTOL to eVTOL Workshop, May 24, 2018 6
National Aeronautics and Space Administration
A History of Ames in VTOL
• The X-14A
– Flew from 1958 until 1981
– Helped to provide understanding of jet-borne hover, 
including the Apollo lunar lander
From VTOL to eVTOL Workshop, May 24, 2018 7
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The Augmentor Wing and Quiet Short Haul 
Research Aircraft
From VTOL to eVTOL Workshop, May 24, 2018 8
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A History of Ames in VTOL
• The Augmentor Wing STOL Research Aircraft
From VTOL to eVTOL Workshop, May 24, 2018 9
Note the use of the choke flap 
to facilitate high frequency  lift 
and roll response. It could 
create drag too, and made a lot 
of noise (a whistle)!
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A History of Ames in VTOL
• The Augmentor Wing STOL Research Aircraft
From VTOL to eVTOL Workshop, May 24, 2018 10
The Curved-Decelerating Descending Approach
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A History of Ames in VTOL
• The Quiet Short-Haul Research Aircraft
From VTOL to eVTOL Workshop, May 24, 2018 11
National Aeronautics and Space Administration
From VTOL to eVTOL Workshop, May 24, 2018 12
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A History of Ames in VTOL
• The V/STOL Systems Research Aircraft
– Significant contributions to the JSF (F-35B) program in the area of 
integrated flight / propulsion controls
– Ability to test other V/STOL flight control configurations
From VTOL to eVTOL Workshop, May 24, 2018 13
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The 40 X 80 Foot Wind Tunnel
• Early Powered, Powered-Lift Models
From VTOL to eVTOL Workshop, May 24, 2018 14
Swept Augmentor Wing
Externally Blown Flap
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Avrocar
From VTOL to eVTOL Workshop, May 24, 2018 15
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The 40 X 80 Foot Wind Tunnel
• Early Powered Models
From VTOL to eVTOL Workshop, May 24, 2018 16
Swept Augmentor Wing Acoustic Suppression Model
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The 40 X 80 Foot Wind Tunnel
• Full-Scale Powered Models
– Airspeeds ranging from about 30 knots to almost 300 knots
– Almost hover conditions, low-speed transition and then high-speed transition through 
cruise
From VTOL to eVTOL Workshop, May 24, 2018 17
The E-7 Ejector Concept in the Tunnel
The E-7 Ejector Concept 
Under Construction 
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STOL Acoustic Testing in the 40 X 80
From VTOL to eVTOL Workshop, May 24, 2018 18
• Aerodynamics / Propulsion / Acoustics Integration Tests
• Lockheed Martin SACD was powered by Williams turbofans
• Cal Poly hybrid wing/powered-lift model was powered by TPS (high pressure air) 
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Small-Scale Testing in the Full-Scale Facility
• Consider small-scale testing in the NFAC if you need large spaces to get 
unimpeded flow and reduce wall-effects on flow field
• You will want a ground plane, the tunnel’s boundary layer is too big
From VTOL to eVTOL Workshop, May 24, 2018 19
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Small-Scale Testing in the Full-Scale Facility
From VTOL to eVTOL Workshop, May 24, 2018 20
Transition from/to hover flight in off nominal flow 
fields and orientations 
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The Outdoor Aerodynamic Research Facility (OARF)
• Model Check-Out and Thrust Calibrations
From VTOL to eVTOL Workshop, May 24, 2018 21
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The Outdoor Aerodynamic Research Facility (OARF)
• Hover Testing In- and Out-of-Ground-Effect
From VTOL to eVTOL Workshop, May 24, 2018 22
Smoke demonstrates just how large the hover flow field can be
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The Outdoor Aerodynamic Research Facility (OARF)
• Jet Decay Rake Measuring Pressure Distribution of the Lift Fan Jet Exhaust
From VTOL to eVTOL Workshop, May 24, 2018 23
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Airspace / Vehicle Integrated Operations
• The aircraft, its trajectory, airspace, and 
environment all work together
• The powered-lift aircraft has the ability to fly off-
normal landing approaches. Can we optimize that?
From VTOL to eVTOL Workshop, May 24, 2018 24
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NM-STAT Noise Mitigation Smart Terminal Area Trajectory (Worst Acronym Ever!)
The C-17 Noise Measurement Team
From VTOL to eVTOL Workshop, May 24, 2018 25
September 2005 – A demonstration of low cost testing techniques to measure the 
noise footprint of STOL approaches in the vicinity of an airport
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NM-STAT Noise Mitigation Smart Terminal Area Trajectory
• The Lakebed Acoustic Array Set Up and Three Types of Landing Approaches
From VTOL to eVTOL Workshop, May 24, 2018 26
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NM-STAT Noise Mitigation Smart Terminal Area Trajectory
Typical Microphone / Computer 
Station with Cal Poly Student Operator
From VTOL to eVTOL Workshop, May 24, 2018 27
Acoustic Footprint over adjacent areas
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Summary
• Ames has unique capabilities built on its long history and 
expertise in VTOL / STOL powered-lift
– A History of Flying Unique VTOL and STOL Aircraft
– Large-Scale Tests at the NFAC and OARF
– Small-Scale Testing
– CFD for complex VTOL flow fields
– Acoustics of powered / augmented lift
– Flight control systems research
– Development of new displays and procedures to aid the pilot 
during unique take-off, transitions, and landing 
– Integration of aircraft and trajectory with the airspace and 
environment in the take-off and landing area
From VTOL to eVTOL Workshop, May 24, 2018 28
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Contributions to VTOL Powered-Lift  State of the Art
• Scale Effects
– Analyzed how small-scale testing can be used as a cost-
effective data source as long as a limited amount of full-
scale testing supplements the database
– One needs to match the jet decay characteristics for the 
scaling to be valid
• Effect of Jet Decay
• The jet structure effects the entrainment, mixing properties of 
the secondary flow
• Significant impact to the jet-noise
• Swirl introduced into the jet can bias the flow field
From VTOL to eVTOL Workshop, May 24, 2018 29
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Future Work That Will Be Needed for UAM
• Flow Field
– Minimize negative flow effects, entrainment, re-circulation
– Jet-induced moment predictions are poor
– Understanding jet decay of lighter disc load fans
– The optimization of electrical systems to facilitate VTOL 
aerodynamics
– Understanding internal flows better
• Auxiliary systems, especially cooling!
– Measuring flow field in the presence of other structures
– Foreign Object Damage (FOD)
• Noise!
From VTOL to eVTOL Workshop, May 24, 2018 30
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Take-Away Points
• Ames has unique capabilities built on its 
long history and expertise in VTOL / STOL 
powered-lift
• VTOL / STOL powered-lift flight is not trivial, 
and you’ll be amazed how uncooperative 
the flow field will be
From VTOL to eVTOL Workshop, May 24, 2018 31


Aerodynamic Testing, Analysis, and Modeling of Powered-Lift

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