Blended Wing Body X-48B Flight Test - 129.171.203.12129.171.203.12/cms/file/liebeck.pdf · Designs start from some requirement or need.\爀䘀漀爀攀砀愀洀瀀氀攀Ⰰ 倀愀礀氀漀愀搀ⴀ爀愀渀最攀Ⰰ

EOT_RT_Sub_Template.ppt | 1/6/2009 | 1BOEING is a trademark of Boeing Management Company.Copyright 2009 Boeing. All rights reserved.

R. H. LiebeckBWB Chief ScientistApril 2015

Blended Wing BodyX-48B Flight Test

X-48B Being Installed in ODU 30x60 Tunnel

BOEING is a trademark of Boeing Management Company.Copyright 2004 Boeing. All rights reserved.

Engineering, Operations & Technology | Boeing Research & Technology

EOT_RT_Sub_Template.ppt | 2Copyright 2009 Boeing. All rights reserved.

Concept Genesis

1903 1947 1992

Is there an Aerodynamic Renaissance for the long-haul transport?-Dennis Bushnell, December 1988

44years 45years

PresenterPresentation NotesDesigns start from some requirement or need.For example, Payload-range, Mission capability like short field landing, or simply to investigate what your competitors are up toThe BWB started from a question.Almost 45 years of aviation innovation transformed the Wright flyer into the swept wing b-47After another 45 years of development the a330 enters the market place

Students often want to work on something that looks different in search of some breakthrough. But we know that things look they way they do for a reason. The, now, conventional design makes a very good airliner

Have we reached the end of this path or is there another leap waiting to occur?Has industry gotten too comfortable in its own success?

A very small NASA contract was set up to explore other designs looking for a break though



Early BWB Concept(NASA / Douglas Aircraft 1993)

Span Loading with Circular Pressure Vessels

Batwing

PresenterPresentation NotesIn an attempt to have your cake and eat it tooWe tried to have the span loading benefits of the BWB configuration with the cabin assembled of multiple tubes pressurized in hoop tension

As this concept developedThe aircraft was rapidly developing back into a conventional configurationMaybe this tells us something?But remember our initial need statement was to explore alternate configurations.

This is one of the most difficult and important lessons I have learned in advanced designOne needs to recognize which constraints are driving the configuration and recognize which are real and which are objectivesAll constraints should be challenged, why is this so? (incidentally, this drives the preliminary design folks nuts, typical answer, because thats they way we do it)Here the circular pressure vessel was believed to be a constraint, when it was only preferred knowledgeAn example is a student design team who was given a negative design spaceThree of the four teams struggled, the fourth looked at the requirements, knew that there was no design that could satisfy these but that the range probably was not a requirement they won the design contestFurther more there was an industry design team, where one discipline stood up and something could not be doneThis drove all their configurations for over five years, while the competition made extensive progress with out this constraint

The balancing act, of course, is not to ignore those things that are important, like containerized cargoBut who says it has to be todays containers?



Span loading Non-lifting vs lifting fuselage Independent vs integrated wing box Payload distributed normal vs parallel

to wing Ideal circular vs flat pressure vessel

Conventional Aircraft Blended Wing BodyAerodynamic Lift

Pressure Loads

Structural Efficiency



Structural Layout

Exaggerated Cabin Skin Deflection at 2X Pressure



Initial Performance Comparison (1993)



Boeing BWB-450 Baseline

247 6

157 10

42 7



Interior Volume Comparison

Frontal Cross Section

Side Cross Section

A380-700



Growing a BWB

Fuel volume available in wing Adds payload Adds wing area Adds span Balanced Aerodynamically Smooth

250

350

450

Common Cockpit, Wing and Centerbody Parts



BWB-5-250G

38-4

129-6

199-2

BWB-5-450G

39-8

152

222

OML Commonality



Definition of Common/Cousin Parts Between BWB-250 and -450

Gauge Changes

Unique OML for Stretch

Payloads - 80% Common- 14% Cousin

Wing Inner Spars & Bulkheads- 100% Common

39%Common

33%Cousin

28%Unique

Total Aircraftby Weight

12%

Recurring Fleet Cost

RecurringCommonality Benefit

23%Non-Recurring Fleet Cost

Non-RecurringCommonality Benefit



Greener than A Green Giant*

Aircraft ComparisonShown to Same ScaleApprox. 480 passengers eachApprox. 8,700 nm range each

MaximumTakeoffWeight

BWB

A3XX-50R

18%

BWB

A3XX-50R

19%TotalSea-Level

Static Thrust

19%BWB

A3XX-50R

OperatorsEmptyWeight

FuelBurn

per Seat

32%BWB

A3XX-50R

QuieterLower thrustEngine noise shielded by body

Not reflected down by the wingNo multi-segment flaps producing air noise

Lower EmissionsLower thrustLower fuel burn

Lower Material WasteComposite constructionLower structural weightLonger airframe life

* A3XX Briefing 2000



Why flight test?

Flight test is justified when required data cannot be obtained via ground-based analyses and testing.

Sub-scale, low-speed flight test requires that the vehicle is dynamically scaled. High-speed requires Mach scaling.

Dynamic scaling assures that the angles between the 6 force and moment vectors are independent of scale.



Vehicle Scaling Laws

Example: Low Speed Vehicle High Speed VehicleK = Scale Factor = 0.085 Dynamic Scaling Mach ScalingLength, L K K for Vehicle, 1 for Motion Area, S = L2 K2 K2

Volume, V = L3 K3 K3

Density, = m/V 1 1/K for Vehicle, 1 for AtmosphereMass, m K3 (Wt = 525 lb) K2 (Wt = 6,176 lb, Wing loading preserved)Moment of Inertia, I = mL2 K5 K3 to K4 (Impossible to obtain K3)Time, T K1/2 1Velocity, U K1/2 1Mach Number K1/2 1 (Must be 1)Force, F = U2S K3 K2

Acceleration, F/m 1 1Moment, M = U2SL K4 K3

Angular Acceleration, M/I 1/K 1 to 1/K (Motion too fast due to MOI < K3)Angular Rate or Frequency, 1/K1/2 1 to 1/K (Response is not correct)Angle, 1 1 to 1/KReynolds Number, LU/ K3/2 K (Similar to pressurized wind tunnels)



Critical Flight Control Technology

B-2 pre-stall limit

CL

BWB post-stall limit

Performance gain

reduced wing area

and weight

CM Stable UnstableIncreased challenge to maintain

control in unstable post-stall region

Controllable in post-stall region

High-rate large control surfaces create large secondary power

demands

BWB Elevon #1

Need to Prove that the BWB is as Robust as a C-17

PresenterPresentation NotesN: But, there are challenges to overcome in order to make a BWB viable.Without tails, the airplane is less stable.Our challenge is to prove that a BWB with an advanced flight control system can be as robust as an airplane with tails.

Some people ask, How is the BWB approach different from the B-2?The Boeing philosophy is to provide the pilot the ability to achieve maximum lift.This means being able to control the airplane up to and past stall.The B-2 has pre-stall angle of attack limiters and has never been stalled in flight testing. (CLICK)



Flying Wing Spin & Tumble Departures

Flying wing dynamics dominated by minimal aerodynamic pitch and yaw damping

Post-stall, this could lead to unrecoverable spin and tumble modes

Spin testing shows that the BWB potentially has unrecoverable spin and tumble modes

Need to prove that an advanced flight control system will prevent entry into departure regions

Then...

Now

Air Flow

Model BWB-450-1L



Two X-48B Vehicles #1: Wind Tunnel & Flight Test #2: Primary Flight Test

Two Configurations Slats extended & retracted

Dynamically Scaled Maximum Weight: 525 lb Wing Span: 21 ft

Max Equiv Airspeed: 118 kts Max Altitude: 10,000 ft MSL Vertical Load Factor Limits: +4.5 to -3.0 gs Flight Duration: 30 to 50 min Emergency Recovery System (Drogue, Parachute, and Air Bags) System Fabricated by Cranfield Aerospace in the UK

BWB X-48B Overview



Triple JetCat P200 Engines Drogue Boom

Interchangeable slat assemblies

Air Data BoomsPilots View Camera

Clean top surface

X-48B Configuration Top View



Fixed Landing

Gear

Triple Airbags for Impact Attenuation

Access Hatches for Avionics, Fuel Tank, Actuator access, etc.

Drogue Boom

Split Drag Rudders

20 Flying ControlSurfaces

X-48B Configuration Underside View



Air Data Interface

Main Chute

Avionics Crate

BatteriesFuel Tank

Laser Height Sensor (Under)

Fuel Pumps & ECUs

Drogue Ejector

Air Bag Inflation System

Drogue Ejector Control Panel

AntennaeGPS Antennae

IMU (Rear of

Bulkhead)

X-48B Configuration Internal View

Drogue Chute Lines (Under Boom)

Drogue Boom

Air Data Boom

Control Surface Actuators

BIT Panel

Transponder



Air Vehicle Configuration Basic Construction Details

Wing Joint

Center Body

WingControl

Surfaces

Slat



Air Vehicle Configuration Major Components

Laser Height SensorAvionics Crate & Cards

Systron Donner C-MIGITS III IMU / GPS

Air Data ProbeKearfott K2000 & Volz Actuators

JetCat P200

ATL Fuel Tank

Nose & Main Landing GearHitachi

Camera

Drogue Ejector



Ground Vibration Test & Inertia Measurement



GCS Trailer

PresenterPresentation NotesM: Here is the Ground Control Station (or GCS) trailer that is located in our hangar at the north end of the NASA Dryden flight test facility at Edwards Air Force Base. (CLICK)Inside the GCS is the pilot station with all the flight controls and displays.This is a good view of the HUD overlay on the pilot view camera display in the flight simulation mode.On the left is the Range Safety Officer position and on the right is the Flight Test Engineer station. (CLICK)



GCS Pilot Station

PresenterPresentation NotesM: In this photo you can see various controls and displays.Starting on the pilots right is the Touchscreen panel used to set the aircraft flight control modes including autopilot, autothrottle, waypoint navigation, and Parameter ID functions like frequency sweeps.Above it is one of the area map displays.Moving to the left and directly in front of the pilot is the HUD and below it the Heads Down display with PFD information.On the bottom left is the flight control, systems, and engines display.Above it is another area map boundary display.A real time impact predictor and keep away range boundaries are displayed on the map displays and are used by the Range Safety Officer to monitor the aircraft position during flight, including waypoint navigation tracking in the emergency event of telemetry link loss.This is also good view of the rudders and the control stick with the red flight termination switch cover.In true British heritage, the control stick is from a Westland helicopter and the rudder petals are from a Harrier. (CLICK)Even the throttles are from the British Tornado, but cut and split to provide separate control for the 3 engines of the X-48.You can see the speedbrake control handle to the right and the engine control and backup trim panel aft of the throttles.To the left is the pilot radio communication panel.Finally, notice the unused mouse and keyboard control to the far left that is even provided with a backup emergency mouse. (CLICK)



Edwards Air Force Base



Recovery System

Drogue

Main

Airbags

PresenterPresentation NotesN: While we will not intentionally spin the vehicle, there is always the potential that the airplane departs controlled flight, so we added a recovery system.You saw the first part in the spin video.The objective of the drogue is to recover the airplane from a spin or tumble and to orient the airplane to come straight down.This is required for range safety to minimize the potential impact area. (CLICK)The drogue is ejected from an aluminum canister using compressed nitrogen. (CLICK)While the first part of the system is the only thing required by range safety, we would like to recover the airplane in one piece.So, we have a main parachute, which is ejected by a barometric trigger at around 1,100 feet above ground level. (CLICK)A spring drogue pulls the parachute pack up the door ramp to take it clear of the engine nacelles. (CLICK)After the airplane is stabilized in a level attitude, doors open under the airplane and blower fans inflate three airbags. (CLICK)Like the Mars rovers, these are designed to cushion the landing.But, the airplane will not bounce off the ground due to the black blow-out vents. (CLICK)



X-48B 30x60 Wind Tunnel Test

ODU Langley Full-Scale Tunnel Wind tunnel test completed April / May 2006 250 hours of testing with flight control hardware active Data used by Boeing for X-48B simulation and flight control software

PresenterPresentation NotesN: After ship 1 was completed, it underwent 250 hours of wind tunnel testing in the Langley Full Scale Tunnel.It is rare to test your actual flight vehicle in a wind tunnel before flight.We collected the air data calibrations during the test before the airplane ever flew. (CLICK)

The X-48B flight control system was active during the entire test to collect the air data and to move the control surfaces.This gave us significant confidence in the robustness of the flight control hardware.

All of the data from the test was reduced before flight and put into the airplane simulation model used by the GCS. (CLICK)



X-48B Flight Test Summary

92 Flights completed (as of May 2011) 55 Flights w/ Slats Extended 37 Flights w/ Slats Retracted (12 Flights conducted to stall/deep stall)

Test Highlights: Test Maneuvers

Real-Time Stability Margins Envelope Expansion Automated Parameter Identifications (PID) Freq Sweeps/Doublets Steady Heading Sideslips - Simulate Cross-winds Lazy-8s and Wind-up Turns Airspeed Calibrations (Triangle method) Successful Approach to Stalls & Beyond Trim in Ground-Effect at 10 feet AGL Engine-out RTB and normal landing

Operations from Hard Surface Runway vs. Lakebed Runway Edwards AFB North Base 6/24 3,000 Feet (Eastern End)

PresenterPresentation NotesN: As of May 8, we completed fourteen flights.Initial envelope expansion was done with the slat extended.Envelope expansion included three CGs, and the full weight and altitude range of the airplane.We are now working on envelope expansion with the slats retracted.Because the slat retracted aerodynamics of the airplane are very different, we treated this like another 1st Flight.Weve completed the Mid-CG testing and are now moving on to other CGs.We have performed a variety of maneuvers during the test program so far.Real Time Stability Margin tests are used to verify flight control stability margins.Parameter Identification maneuvers, such as doublets and frequency sweeps, are executed automatically from the flight computer.Steady Heading Sideslip maneuvers were used to clear the crosswind envelope.We flown approaches to stall, but have not yet stalled the airplane.Stall testing will be part of the next flight test phases.The winter rains flooded the lakebed runways, so we are now operating from the Edwards North Base and will continue to do so as we collect less dust on the airplane. (CLICK)



6:00 am July 20, 2007



7:00 am



8:30 am



8:45 am



First Flight Video

PresenterPresentation NotesM: So lets just jump right into some video clips put together from the first flight of the X-48.Our call sign is SKYRAY 48.(CLICK).Heres the takeoff from the view of our ground chase truck on the lakebed.Notice the wing dip as the aircraft transitions from ground to flight mode.We used a NASA T-34 aircraft for photo and safety chase that you can see here.We are doing autopilot and autothrottle on/off checks in the climb, and that is what you hear on the radio about the tape mismatch.Here you can see a manual yaw frequency sweep test point.Notice the motion on the split outboard rudders.In later flights we used the automated programmed PID from the touchscreen.Time for descent comes quickly and we usually pull the throttles to idle, and continue to click through test points.The next event is when the aircraft reaches MEPHR altitude which is stands for Minimum Emergency Parachute Recovery altitude.This is the lowest planned altitude that the Flight Termination System is designed to be employed and safely recovered almost like a minimum bailout or ejection altitude for manned aircraft. The brake check is part of our before landing checks.Laser altimeter is our accurate radar altimeter for height above ground, and the FTE verifies that it has become active descending through 50 feet AGL.Another view of the landing from the chase mission complete.Notice the plane rocking side to side as the brakes are applied, one of the things we noticed even on the first taxi tests was that the lack of feedback may cause the potential of braking PIOs. (CLICK)



9:20 am



10:30 am



I. Unique tailless configuration required development of special flight control laws.II. Flight simulator developed to evaluate control laws and train pilots.III. Following first flight, test pilot reports that flying the simulator and flying the

airplane are equivalent.IV. Test pilot reports that the X-48B exhibited no unusual characteristics, and is a

very nice airplane to fly.

X-48B Primary Flight Test Result

Copyright 2007 Boeing. All rights reserved.



X-48B Lessons Learned

COTS Design approach Initial Equipment Cost Low, But Integration Cost may be High Original planned Engine Design not COTS large impact to Flight Duration

Waypoint Nav Design / Software V&V testing Test Limits - Windshear, Gusts / Weather Balloon Data

Flight Simulator invaluable for Successful Tests Very good match for flight Excellent flight rehearsal / pilot training tool

Braking PIO potential High No Decel Feedback to Pilot / Brake Spring or Ground Models inaccuracies

Robust Flight Control System can Mask some Control Law Deficiencies

Lessons Re-Learned

Copyright 2007 Boeing. All rights reserved. 41

PresenterPresentation NotesN: Weve learned a lot from this project and quite a few of the lessons are useful for other programs.COTS equipment can initially save time and money, but not having a complete understanding of the inner workings of the equipment can lead to high integration costs.Custom developed equipment, such as our original engines, can fail to work as promised.So, a careful balance needs to be struck in choosing equipment and it is always good to have a backup plan.The autonomous waypoint navigation system took considerable time to develop and test.The verified capabilities of this system often set our wind limits, even though the pilot may be capable of handling higher winds.We use a weather balloon prior to flight to verify that the winds are within limits.

M: The GCS flight simulator is invaluable for successful flight tests.The flying qualities matched very closely possibly due in large part to the result of the being able to extensively test the actual flight hardware in the wind tunnel.The GCS provides excellent flight rehearsal opportunity, particularly in light of the extremely short flight duration.Additionally, it is a valuable pilot training tool for qualification and Emergency Procedure training.Braking PIO potential is high because there is no deceleration feedback, and possibly due to some brake spring and or ground modeling inaccuracies.While full braking is always available, we are effectively working around this by normally evenly applying only half brake pressure on landings when there is plenty of runway remaining.Finally, a robust flight control system can mask some control law deficiencies as was evidenced in the beta vane switching and the pitch authority differences in ground versus flight modes. Now, Norm will talk some about what the future holds for the X-48 (CLICK)



X-48B Whats Next for the Future

COTS Design approach Flight Duration Flight control logic (Beta Switching) Waypoint Nav Design / testing Test Limits (windshear, gusts) 2-D view soda straw limitations Braking PIO potential

Copyright 2007 Boeing. All rights reserved. 42

Testing planned to continue thru FY2012 Modified Geometry for Lower Noise

PresenterPresentation NotesN: The project will continue flying through the end of the year to complete the currently funded 25 flight and other planned testing.Additional follow-on testing will likely extend the project through the end of fiscal year 2010.

In the immediate future, we will complete our slat retracted envelope expansion and then move into riskier testing.The next phases will include stalls, high angles of attack, and simulated engine out testing.We will perform the riskiest testing last, which will include high sideslips and aggressive testing of the departure prevention limiters.All of this will first be done slat extended before going to the riskier slat retracted configuration.

Coming down the road at some point will be a change to turbofan engines that are now in development.These engines have the potential to cut our fuel burn in half, thus allowing longer flights. (CLICK)



BWB X-48C



X-48C Low Noise Configuration in 30x60 Wind Tunnel



Innovation: Before & After

Initial Goal: Create a concept for a subsonic transport that may be distinct from tube & wing (DC-8, B707).

Initial Result: BWB that offered reduced fuel burn via a very high Lift/Drag ratio and large wingspan.

Developed Result: BWB that offers breakthrough fuel efficiency and noise reduction.

Unplanned Features: Natural family, low noise, low part-count and low cost.

Unplanned Liability: As a disruptive technology, the BWB may be regarded as a threat to existing airplanes.


EOT_RT_Sub_Template.ppt | 46Copyright 2009 Boeing. All rights reserved.Copyright 2006 Boeing. All rights reserved.

Thank You

Blended Wing BodyX-48B Flight TestConcept GenesisEarly BWB Concept(NASA / Douglas Aircraft 1993)Slide Number 4Structural LayoutInitial Performance Comparison (1993)Boeing BWB-450 BaselineInterior Volume ComparisonSlide Number 9Slide Number 10Slide Number 11Greener than A Green Giant*Why flight test?Vehicle Scaling LawsCritical Flight Control TechnologyFlying Wing Spin & Tumble DeparturesFlying Wing Spin & Tumble DeparturesBWB X-48B OverviewX-48B Configuration Top ViewX-48B Configuration Underside ViewX-48B Configuration Internal ViewAir Vehicle Configuration Basic Construction DetailsAir Vehicle Configuration Major ComponentsGround Vibration Test & Inertia MeasurementGCS TrailerGCS Pilot StationEdwards Air Force BaseRecovery SystemX-48B 30x60 Wind Tunnel TestSlide Number 306:00 am July 20, 20077:00 am8:30 am8:45 amFirst Flight VideoSlide Number 369:20 am9:20 am10:30 amSlide Number 40X-48B Lessons LearnedX-48B Whats Next for the FutureBWB X-48C X-48C Low Noise Configuration in 30x60 Wind TunnelInnovation: Before & AfterSlide Number 46

Documents

Blended Wing Body X-48B Flight Test - 129.171.203.12129.171.203.12/cms/file/liebeck.pdf · Designs start from some requirement or need.\爀䘀漀爀 攀砀愀洀瀀氀攀Ⰰ 倀愀礀氀漀愀搀ⴀ爀愀渀最攀Ⰰ

Blended Wing Body X-48B Flight Test - 129.171.203.12129.171.203.12/cms/file/liebeck.pdf · Designs start from some requirement or need.\爀䘀漀爀攀砀愀洀瀀氀攀Ⰰ 倀愀礀氀漀愀搀ⴀ爀愀渀最攀Ⰰ