Dougie Hunter Msc Aerospace Vehicle Design 1985/86 Head Of

Introduction

Dougie Hunter MSc Aerospace Vehicle Design 1985/86

Head of Aerospace Defence and Security at The Manufacturing Technology Centre

Chairman of Cranfield College of Aeronautics Alumni Association

1 The National Flying Laboratory Centre: In-Flight Measurement and Research

Nick Lawson Professor in Aerodynamics and Pilot National Flying Laboratory Centre

School of Aerospace, Transport and Manufacturing Cranfield University, U.K.

2 www.cranfield.ac.uk November 2020 Contents

• National Flying Laboratory Centre . Foundations . Evolution of NFLC . The Present • Recent Research . EU – AIM2 airborne sensors . ATI – Advanced aerodynamic sensors . Application of CFD to in-flight testing • The Future • Summary

3 AIM2 – Advanced In-Flight Measurements 2 National Flying Laboratory Centre - Foundations

https://www.britishpathe.com/video/aeronautical- Pathe News (1953) 4 school?fbclid=IwAR2SvDPCJfFYVgQ6R8Fr-JfqW7O6EmC_1JXXaXJP7IUXKZGZPaeXpMCOiqI National Flying Laboratory Centre - Foundations

Airborne electronic equipment for the measurement of undercarriage loads. Equipment designed and built by 2nd year students (Anson)

5 College of Aeronautics (CoA) Brochure 1947 National Flying Laboratory Centre - Foundations

Department of Flight Aircraft (1947) • Dove • Ansons x 3 • Tiger Moths x 3 Department of Flight (CoA Brochure 1947): • provides students with actual flying experience to demonstrate the theories taught in other departments (Aerodynamics, Aircraft Design, Propulsion, Aircraft Economics and Production) • has complete facilities for flight testing and full scale research • provides instruction in the latest methods of testing aircraft & aircraft equipment in flight 6 National Flying Laboratory Centre - Foundations

Department of Flight Aircraft Fleet (1960’s)

Department of Flight Avro Lancaster PA474 – Laminar flow control test bed

7 National Flying Laboratory Centre - Foundations

1st Year Syllabus 2nd Year Syllabus

8 National Flying Laboratory Centre - Foundations

Light aircraft have played a key role in NFLC’s delivery: Department of Flight provides an ab initio flying training scheme by which students can be taught to fly solo at reduced charges. Instruction is given on Tiger Moth aircraft by a full-time flying instructor…. (1947)

putting theory into practice! 9 National Flying Laboratory Centre - Evolution

• First 3 Jetstreams acquired in early 1970’s from HP • Two converted, third sold • Further operated on behalf of Racal

• CEGB & EU – atmospheric monitoring • Racal – navigation / radar / GPS systems • Ferranti – avionics / sensors • Easams – TCAS development • Meggitt / Smiths – avionics • GEC Marconi / Cranfield Aerospace Solns - various 10 • BAE Systems – avionics / sensors (Jetstream 31) National Flying Laboratory Centre - Evolution

• formation of the National Flying Laboratory Centre (NFLC) came from proposal to HEFCE by Martin Eshelby (Cranfield) in 1992 / 1993. Significant support of the proposal and ongoing funding by Prof. Ron Fletcher (Deputy VC) • Subsequent HEFCE funding allowed expansion of the number of UK university partners using NFLC • Research with industry continued. Jetstream Mark 1’s retired by 2005 and replaced by current Jetstream 31, G-NFLA 11 National Flying Laboratory Centre - Evolution

• Substantial collaboration evolved with BAE Systems Jetstreams • NFLC operated the BAE flying testbed G-BWWW on regular flight trials • Last major flight trial was ASTRAEA II to demonstrate ‘see and BAE Jetstream 31 avoid’ and comms technology in controlled airspace

G-BWWW was set-up as a surrogate UAV test platform. ASTRAEA used a ground control station to control the aircraft and communicate with ATC. A major milestone for the UK aerospace (2013) In 2021 WW will become a teaching aid for Cranfield University students 12 National Flying Laboratory Centre – Test Pilots

Astronaut Neil Armstrong with Chris Daggett

Courtesy: Colin Martin

‘Dodge’ Bailey Test Pilots (TPs) always give NFLC key credibility • Grp Cptn. Ronald C. Hockey DSO DFC (40’s – 50’s) • Robbie Robertson DFC (40’s – 70’s) • Prof. Charles McClure (50’s – 70’s) • Angus McVitie (70’s – 90’s) Simon Davies • Roger ‘Dodge’ Bailey (90’s – 2015) 13 • Simon Davies (our current TP) National Flying Laboratory Centre - Present

Jetstream 31 Slingsby T67

G-NFLA Flying Laboratory Flight test short courses G-BWXT Bespoke equipment testing Student flight experience (flying 1600+ students/yr from Part SPO Operation Aerobatic training 20+ UK uni’s & Limerick Uni) - Accountable manager - Safety Manager - Compliance Manager Saab 340B Bulldog - Air Ops Manager - Ground Ops Manager - Training Manager - Airworthiness Manager - Chief Demonstrator - Light Aircraft Manager G-BCUO Flying Test Bed - Test Pilot & Pilots Instrumentation research G-NFLB – replacement Student flight experience flying laboratory early 2021 A great Centre – thank you! Aerobatic training 14 Saab340B Flying Laboratory and Test Bed

General: • 32 seat turboprop (~£3M) • Aircraft currently being modified by Saab (into service Q1-Q2 2021) • WiFi cabin with student tablets for interactive experiments • Angle of attack, angle of sideslip, control and tab positions, stick forces • Air and engine data, inertial and differential GPS, wing/cockpit cameras • SatCom system / avionic industrial flight trials rack (DARTeC + other)

Student tablet lab screen

15 DARTeC – Digital Aviation Research and Technology Centre Saab340B Flying Laboratory and Test Bed

Cranfield Aerospace Solutions

Scitek - Derby

Saab Saab

16 Bulldog Fibre Optic Sensors Flying Test Bed

General: • Aerobatic category (+6g to -4g) 2 seat light aircraft • Aircraft modified in 2013-2014 as part of EU FP7 AIM2 project • Two fibre pressure and wing strain systems installed • Recently modified 2019-2020 with air data and control posn sensors

Modifications: • Power supply box • Data logger / AHRS / trigger box • Smartscan FOS interrogator • On board cameras • Elevator, rudder, aileron, flap sensors • Air data computer & air data boom

17 FOS – Fibre optic sensor AHRS – attitude heading reference system Fibre Optic Sensors for Flight Test

Prof. Ralph Tatam Head – Engineering Photonics

Fibre Bragg grating (FBG) core Smartscan FP pressure Aero sensor + Kulite interrogator pressure sensor for in-flight for verification fibre signal Fabry Perot fibre sensor processing

2mm 18 BLADESENSE

First fibre optic shape and strain sensing on a rotating helicopter rotor Ground test trials on an Airbus H135 helicopter in November 2019 rotating hub with wifi connected fibre optic shape and strain interrogator

initial dynamic results from blade mounted dual fibre optic shape sensor 19 WINDY – WIng DesigN methodologY validation First fibre optic pressure wing FBG arrays and strain sensing in a for strain transonic wind tunnel M0.82 Wind tunnel trials ARA Bedford September 2019

9’ x 8’ tunnel top sensor plate

wing strain

fuselage fuselage sensor test pressure plate (fibre optic pressure and Kulite) 20 Bulldog ‘Leans’ Study (with TNO and TU Delft)

Condition Start Slow roll Fast roll Intended attitude indicators can to: to: expectation

be misinterpreted Matching under strong g-cues: (practice) the ‘leans’ No leans ‘leans’ can lead to A Typical major loss of control Attitude Leans- Indicator opposite

Leans- level

The practice and test conditions

50 Cranfield ‘non-pilot’ students conducted the ‘leans’ disorientation study 21 Bulldog ‘Leans’ Study (with TNO and TU Delft)

https://1drv.ms/v/s!AqvNv7Mai6RqhbBj_SqWpQViOTgg1Q?e=D5LLuu 22 • Ana Oliveira Das Neves • Simon Davies • Bidur Khanal (Coventry Uni.)

23 Stall – Spin: Background

• Fixed wing aircraft can stall or spin in any category • Stall – spin most prevalent in take-off and climb for general aviation • 30% of all general aviation accidents originate from stall – spin

Source: AOPA 24 Stall: Background

• Stall is a condition with significant BL separation and loss of lift from a wing/body • Angle of attack a is the key variable for stall and spin • Flight path & reference line define angle of attack (a), lift & drag vectors Lift

Thrust

a Drag flight path

climb horizon mg stall descent Lift Drag (CL) (CD)

25 Angle of Attack a Spin: Background • Spin is a stable flight condition with asymmetric wing stall • the aircraft autorotates about a near vertical axes descending rapidly • CoG follows helical flight path with aircraft pitching/rolling/yawing • Recovery (if possible) with rudder and elevator

Source: NASA https://1drv.ms/v/s!AqvNv7Mai6R qhat0WSpLitjoSLv6og?e=knTTc1

https://1drv.ms/v/s!AqvNv7Mai6Rqhat2vmcVqyniKjI-xA?e=XXXzMa

26 Spin: Background • Spin is a stable flight condition with asymmetric wing stall • the aircraft autorotates about a near vertical axes descending rapidly • CoG follows helical flight path with aircraft pitching/rolling/yawing • Recovery (if possible) with rudder and elevator

Source: NASA • New computational methods Mechanics of Flight offer complementary 2nd Edition, W.F. approach to wind tunnel and Phillips, Wiley (2010) flight testing (spin & stall)

• Cranfield has strong previous connections with spin research (Colin Martin – CoA*) 27 *Colin Martin FRAeS is ex-College of Aeronautics staff and holds the Lawrence Hargrave Medal 2015 Slingsby Firefly T67M260 Aircraft

• Aerobatic category (ex-RAF trainer) • Experimental (in-flight) • 2 seat side-by-side light aircraft • Numerical – CFD • Engine 260hp Lycoming AE10-540 • Comparisons (in-flight vs CFD) • +6 to -3g envelope • Tailplane-Wake Interaction • MTOW 1157kg / Wing chord 1.2m • @50m/s (ISA) Re = 4.1 x 106 chord S&L flight data (CL, a)

steady CFD soln

stall flight data (CLmax, a, buffet)

unsteady CFD steady soln

CFD vs experiment

28 CFD – computational fluid dynamics Straight and Level Flight Tests

Straight and level used to find range of angle of attack a up to stall: • Validate steady CFD model • Steady CFD soln is initial condition for unsteady CFD model Record airspeed, OAT (oC), altitude, power (rpm, manifold press) and equate lift weight & engine pwr airframe drag/V L = mg – Tsina L = 1/2C rV2S L D = Tcosa Ph = TcosaV T p a flight path 2 D = 1/2CDrV S

horizon mg

29 L = lift D = drag T = Thrust V = true airspeed r = density CL = lift coeff. Flight Stall a: Flight Measurement

Stalled flight (engine idle) results in aircraft descending with changing a: • Stalled flight must measure FPA - l and pitch attitude - q simultaneously • a is the sum of l and q For test, record ground speed (cross wind), altitude, pitch attitude N.B. airspeed indication unreliable in stall

FPA – flight path angle l pitch attitude

horizon q a l

flight path

30 Flight Stall a: Test Set-ups

Method 1 – iPad-Level-Altimeter Method 2 – Pixhawk Inertial Unit

Pixhawk4 250Hz accels 5Hz GPS

digital level

iPad ground speed digital level camera (1Hz)

31 Flight Stall a: Flight Test Results

Both tests indicated stall characteristics around a = 15o – 20o

Heavy buffet and wing drop at: a = 20o – 30o

Unsteady CFD modelled through range: a = 14o – 18o

N.B.: ‘validation’ from iPad / digital level l2/l3, a2/a3 from Pixhawk4

5 knot head/tail wind at 30m/s equates to FPA error l ~8o

32 CFD Model Set-up

Single mesh refined for steady and unsteady model with wake density region: • SA / k-w SST models tested – k-w SST chosen • Key grid spacing follows the Smagorinski LES model 푘−휀 푘−휔 • DES blending through 퐶퐷퐸푆 = 1 − 퐹1 퐶퐷퐸푆 + 퐹1퐶퐷퐸푆

• 10 monitoring points + CL and CD half model Mesh sizes: Coarse (7.6M) Medium (11.3M) Fine (17.2M) domain wake density region

mesh y+ 1 – 5 wing

monitoring points

33 DES – detached eddy simulation Stall Buffet: CFD Movies a = 16o

• results indicates tailplane interaction • tailplane not heavily stalled

https://1drv.ms/v/s!AqvNv7Mai6Rq hat51vmhLbHs3FaA_Q?e=vYEn8H

https://1drv.ms/v/s!AqvNv7Mai6Rq 34 hat4dkV0vTgOxsjrPA?e=duKh6a Flight Stall Buffet: Tests

Aircraft bought into a stall and buffet recorded before ‘wing drop’: • Shimmer3 IMUs for in-flight aerodynamic buffet frequency (up to 1kHz) • Ground tests of natural wing frequency (6.2Hz) using IMUs • 30Hz HD cameras monitoring pitch attitude

Dominant natural frequency of ~6Hz will allow discrimination from aerodynamic buffet frequencies

IMU in-flight set-up

35 http://www.shimmersensing.com/images/uploads/docs/Shimmer_User_Manual_rev3p.pdf Flight Stall Buffet: In-Flight Data

sample windows flight data from IMU #1 at different a

‘wing drop’

(IMU/camera sync)

36 Flight Stall Buffet: In-Flight vs CFD

Flight data with increasing a

CFD data

spectral frequency comparison, ~1% error (dependent on flight a estimate)

37 Flight Stall Buffet: Wake Tailplane Interaction

accelerometer mounted onto tailplane and an impulse disturbance used to excite the accelerometer structure

spectra indicates a key natural frequency of around 9 Hz

38 Flight Stall Buffet: Wake Tailplane Interaction

rear view: progressive stall to heavy buffet and ‘wing drop’

front view: https://1drv.ms/v/s!AqvNv7Mai6Rqhat1RHb-AeOriCqNhg?e=2Yj2Jr 39 rear view: https://1drv.ms/v/s!AqvNv7Mai6RqhatzgheKAiSgmdqvww?e=3ODRxW Flight Stall Buffet: Wake Tailplane Interaction

spatially correlate image sequence v using xpiv software u 50Hz image sequence

tailplane v point sample component from correlation 9Hz spectrum v component dominant frequency

40 NFLC – The Future

simpleflying.com + = 10MW wind turbine electro-fuel plant annual A350 fuel

41 electro-fuel fuel plant: https://ineratec.de/en/become-a-pioneer/ accessed Oct 2020 NFLC – The Future

• Digital Aviation Research & Technology Centre (DARTeC) – the NFLC aircraft will provide an airborne platform to test digital aviation systems. A SatCom system will initiate this work from 2021 • The Saab340 will allow NFLC to continue to develop a dual role for the aircraft, with increasing industry involvement • NFLC has an ambition to promote sustainable aviation fuels (SAFs), as part of the ‘netzero’ transition in aviation. There is an opportunity for NFLC to run its aircraft on Cranfield produced SAFs in the next 5 years • The establishment of a Sustainable Aviation Research Centre (SARC) will allow the development of future aviation systems using aircraft operated by NFLC • STEM outreach will be expanded to promote aerospace to the next generation of engineers through experiential learning, on the ground and in the air

42 electro-fuel fuel plant: https://ineratec.de/en/become-a-pioneer/ accessed Oct 2020 Summary

• NFLC originated from the requirement to demonstrate flight test techniques to aerospace engineers – a key part of the validation of aircraft design • NFLC has engaged industry over 5 decades to advise and help with complex flight trials and to develop science and sensors • The recent investment by Cranfield and its partners in the new Saab340 aircraft will continue the close engagement with academia and industry

• Research activity in NFLC involves close collaboration with internal and external aerodynamic, instrumentation and human factor groups • Recent research is advancing fibre optic sensors for aerodynamics and airborne research and human factors trials • Advanced numerical methods offer enhanced approaches to flight test and aircraft design

43 Acknowledgements

• Handley Page Association / CCAAA • Royal Aeronautical Society • Industry and NFLC university partners • Cranfield Senior Management Team • Cranfield Media • Cranfield Alumni and Alumni Team

• Dodge Bailey • Graham Braithwaite • Andy Foster • Jack Stockford

44 Questions?

Professor John Fielding

President, of Cranfield College of Aeronautics Alumni Association

45 Vote of Thanks

Professor Helen Atkinson CBE, FREng Pro-Vice-Chancellor Aerospace, Transport and Manufacturing Cranfield University

46 Awards

Congratulations to: Dr Alan C Brown DCAe Honorary Doctor of Science from Cranfield University on the 2020 J.C. Hunsaker Award in Aeronautical Engineering presented by the US National Academy of Engineering "for innovative contributions to the design of commercial and military aircraft, and particularly leadership of the team that developed the Lockheed F-117 Stealth Fighter."

47 NFLC Fundraising Campaign

https://www.youtube.com/watch?v=zfya9EB3_Ak 48 Closing Remarks

Dougie Hunter MSc Aerospace Vehicle Design 1985/86

Head of Aerospace Defence and Security at The Manufacturing Technology Centre

Chairman of Cranfield College of Aeronautics Alumni Association