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Natural Icing Trial on Nimrod MRA4: Results and Lessons Learned

This article provides an overview of the Nimrod MRA4 natural icing trial, including trial planning, execution, results, and lessons learned. It covers topics such as certification requirements, ice protection system performance, and icing encounter management. The trial was conducted in Nashville, TN, USA, in Feb 2008.

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Natural Icing Trial on Nimrod MRA4: Results and Lessons Learned

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  1. Knowing when to ask for help.Nimrod MRA4 Natural Icing ProgrammeNashville TN, USA - Feb 2008Ed Townshend- Nimrod Test & Evaluation

  2. Scope • Background to Trial • Trial Planning • Trial Execution • Results • The Outcome • Lessons learnt

  3. Background – The Requirement

  4. ICE SHAPES DRY AIR TESTS NATURAL ICING FULL ENVELOPE HANDLING ANTI ICE SYSTEM PERFORMANCE ANTI ICE SYSTEM PERFORMANCE ACCRETION MODEL BASIC HANDLING PERFORMANCE Background – The Requirement ICING CLEARANCE

  5. PRE DEPLOYMENT CONFIRM WEATHER CHARACTERISATION PROBES HAVE NO EFFECT ON HANDLING Background – Certification Requirements Def-Stan Requirements & JAA Guidance DEMONSTRATE ICING PROTECTION • DEMONSTRATE ICE PROTECTION ACROSS RANGE OF ICING CONDITIONS (APPENDIX C) • DEMONSTRATE ICE PROTECTION SYSTEM UNDER SINGLE FAILURE STATE • VALIDATE ENGINE AND AIRFRAME ICE PROTECTION SYSTEM MODELS DEMONSTRATE TOLERANCE TO ICING • CONFIRM ICE ACCRETION MODEL CORRECT • DEMONSTRATE BASIC HANDLING & SYSTEM PERFORMANCE UNDER FULL AND PARTIAL PROTECTION. • CONFIRM ICE RELATED PERFORMANCE PENALTIES

  6. Background – The Aircraft • PA1 used as primary programme handling aircraft. • Fully instrumented Anti Ice System • No Mission System Radar, but standalone Weather radar fitted Heated Windscreen panels Horizontal stabiliser anti-icing Engine intake Anti-icing Ice detection probe Visual ice accretion vane Wing leading edge anti-icing

  7. Planning – Start point Pre trial Company Military aircraft icing experience: ZERO

  8. Planning - Logic DEFINED & UNDERSTOOD REQUIREMENTS Programme Timescales Maximise Safety IDENTIFY RISKS MAXIMISE EFFICIENCY MANAGE ICE ENCOUNTERS MINIMISE EXPOSURE TO RISKS CERTIFICATION

  9. Planning – Gathering experience HOW TO FIND ICING HOW TO MEET CERTIFICATION REQUIREMENTS HOW TO CAPTURE RESULTS DESIGN AUTHORITY WORKS WITH CUSTOMER EXPERTS CONTRACT METEOROLOGIST WITH ICING EXPERTISE CONTRACT WEATHER CHARACTERISATION EXPERT

  10. Planning – Finding Icing • Identify time of year trial programme planned • Identify list of potential venues from experience • Identify factors for scoring locations and weighting: • Daytime available • Frequency of Icing encounters within range • Base Weather / facilities • Availability of diversions • Air Traffic Density • Quality / Availability / Cost of Forecasting data • Nashville chosen from list of Prestwick, Keflavik, St Johns & Central USA • Extensive dialogue with FAA to build understanding with US ATC Picture courtesy of NASA

  11. Planning - Accurate Meteorology • Weather out of our control • Response to weather is under our control • In depth knowledge of icing weather systems • Maximise understanding of forecast • Target weather and plan Escape routes • Continue to monitor weather as it evolves • Track aircraft throughout flight • Compare route with forecast and results • Refine onward approach

  12. Planning - Instrumentation • Wing pylon with two instruments for droplet diameter measurement and identification: • Forward Scattering Spectrometer Probe (FSSP) • 2 Dimensional Cloud optical array probe (2DC) • Window mounted King Probe to measure Liquid water content • System partially integrated into existing FTI • Existing FTI records aircraft system performance

  13. Planning - Instrumentation • Four video cameras mounted in windows / pylon • Window mounted periscope with camera mount for tail observation • Multiple handheld stills and video cameras for crew use • Ice depth gauges mounted on wings and tail

  14. Planning - Instrumented Aircraft

  15. Planning - Informed Meteorologist

  16. Planning - Communication Traditional Open Loop method Remaining testing Encounters feedback sortie plan Conduct Test Weather forecast Takeoff Land

  17. Planning - Communications THE GAP

  18. Planning - Communication Traditional Open Loop method Remaining testing Encounters feedback sortie plan Conduct Test Weather forecast Takeoff Land Closed Loop method Remaining testing Encounters feedback sortie plan Conduct Test Meteorologist Weather forecast Takeoff Land Weather update / PIREPS / Aircraft Location PIREPS – Pilot Icing REPorts

  19. Planning - Satellite Communications

  20. Planning – Crew roles • 10 Crew • 2 pilots, Navigator, Comms to fly aircraft safely • 3 FTOs to monitor icing build up and anti ice system status & performance • 1 Weather Characterisation Expert, Design Authority FTO & Customer Representative FTO to provide on board expertise and test validation. • Second Team of 5 FTOs to enable concurrent reporting

  21. Planning - Summary HOW TO MEET CERTIFICATION REQUIREMENTS HOW TO FIND ICING HOW TO CAPTURE RESULTS DESIGN AUTHORITY WORKS WITH CUSTOMER EXPERTS CONTRACT METEOROLOGIST WITH ICING EXPERTISE CONTRACT WEATHER CHARACTERISATION EXPERT CLEAR TEST REQUIREMENTS AND SUCCESS CRITERIA PLAN FOR TRACKING WEATHER AND A/C INSTRUMENTED AIRCRAFT TO RECORD WEATHER

  22. Planning – Trial approval • Two main documents required: • Flight Test Programme document • Operational Management Plan • Trial assessed as High / Medium Risk • Concept and Safety Reviews mandated • Required approval from the Company, UK Military Flying Regulator, & FAA

  23. Planning – Considered Risks • Ice accretion on unprotected surfaces not as expected • Ice accretion on protected surfaces due to poor system performance or severe conditions • Ice induced Landing gear / flap system malfunctions • Reduced directional stability leading to increased sideslip / fin loads • Stalling with ice is new untested configuration • Engine flameout or damage due to intake ice shedding • Damage on ground due to ice shedding

  24. Planning – Logic Summary DEFINED & UNDERSTOOD REQUIREMENTS Programme Timescales Maximise Safety Combine knowledge of Specialists & Operators IDENTIFY RISKS MAXIMISE EFFICIENCY MANAGE ICE ENCOUNTERS MINIMISE RISKS CERTIFICATION

  25. Execution • Departed UK 29th Jan – date set 1 year previously • Fitted External Instrumentation • Redeployed briefly to avoid Severe Weather • Flew 11 sorties over next 21 days • Flying only curtailed by: • 1 day President Bush visit to storm victims • 1 day servicing • 1 day aircraft snag • 6 days unsuitable weather • Removed external instrumentation • Arrived back in UK 4th March, again within plan

  26. Appendix C completion Full AI handling - 2.0” Part AI handling - 1.0” Part AI handling - 1.5” Full AI handling - 1.0” Full AI handling - 0.5” Part AI handling – 0.5” Full AI Systems Tests - 2.0” Dry Air Rehearsal Execution – Incremental Approach Full AI = Airframe + Engine Anti Ice ON Part AI = Airframe OFF + Engine Anti Ice ON Experience Time

  27. Execution – Area covered

  28. Results – Wing – Protection On

  29. Results – Wing – Protection Off

  30. Results – Wing and Tail

  31. Results - Fin

  32. Results – System Failure Test

  33. Results – Runback

  34. Results – Probes

  35. Results – Probes

  36. Results – Post flight observations

  37. Results – Encounter Envelope LIQUID WATER CONTENT MEAN DROPLET DIAMETER (Microns)

  38. The Outcome HOW TO MEET CERTIFICATION REQUIREMENTS HOW TO FIND ICING HOW TO CAPTURE RESULTS    TASK AGREED COMPLETE BY ALL PARTIES BEFORE DEPARTURE 11 FLIGHTS 61 HOURS 21 DAYS ICE WAS FOUND AND SAFELY CHARACTERISED ON EVERY TEST FLIGHT

  39. Lessons Learnt • Get help for areas where you are lacking knowledge and experience • Planned Concept of Ops worked extremely well: • Meteorologist and Weather Characterisation experts • Satellite telephone communications • Design Authority and Customer direct involvement GO OUT AND GATHER THE BEST POOL OF EXPERIENCE TO GET THE BEST RESULTS

  40. Questions

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