Statistical Assessment of Changes in Bird Certification Rules for Aero-Engines Through Time

Transcription

1 University of Nebraska - Lincon DigitaCommons@University of Nebraska - Lincon 2011 Bird Strike North America Conference, Niagara Fas Bird Strike Committee Proceedings Statistica Assessment of Changes in Bird Certification Rues for Aero-Engines Through Time Juian Reed Impact Engineering at Ros-Royce., Juian.Reed@Ros-Royce.com Foow this and additiona works at: Reed, Juian, "Statistica Assessment of Changes in Bird Certification Rues for Aero-Engines Through Time" (2011) Bird Strike North America Conference, Niagara Fas This Artice is brought to you for free and open access by the Bird Strike Committee Proceedings at DigitaCommons@University of Nebraska - Lincon. It has been accepted for incusion in 2011 Bird Strike North America Conference, Niagara Fas by an authorized administrator of DigitaCommons@University of Nebraska - Lincon.

2 Statistica Assessment of Changes in Bird Certification Rues for Aero-Engines Through Time Dr Juian Reed Associate Feow Impact Engineering Ros-Royce pc 2011 Ros-Royce pc The information in this document is the property of Ros-Royce pc and may not be copied or communicated to a third party, or used for any purpose other than that for which it is suppied without the express written consent of Ros-Royce pc. This information is given in good faith based upon the atest information avaiabe to Ros-Royce pc, no warranty or representation is given concerning such information, which must not be taken as estabishing any contractua or other commitment binding upon Ros-Royce pc or any of its subsidiary or associated companies. Page 1 of 17 Dr J M Reed

3 Overview Aim: to deveop a means of assessing potentia benefit of engine certification rue changes Feet cyces past and future Bird rue changes through time Bird strike distribution considerations Monte-Caro method engine capabiity for different rues Feet risk through time Rate of introduction of new products Feet risk in the future Concusions and recommendations Note: predictions made regarding future feet mix are soey the judgement of the author Ros-Royce proprietary information Page 2 of 17 Dr J M Reed

4 Feet Aircraft Cyces Per Year Increase is sustained through time and predictabe Trend seems to recover from major setbacks Recession 9/11 Guf War Ros-Royce proprietary information Page 3 of 17 Dr J M Reed

5 Feet Cyces Per Year Looking Forward 40 miion fights per year by 2030 Wi have doubed since start of century But what ies behind the curve? Ros-Royce proprietary information Page 4 of 17 Dr J M Reed

6 Feet Cyces Makeup Data from ASCEND Part 33 Issue 1 st Med Bird A6 FOD 1½b Med Bird A10 FOD Critica Areas A20 Birds 2½b Med Bird A24 Lge Fock Ros-Royce proprietary information Page 5 of 17 Dr J M Reed

7 Bird Ingestion Certification Rue History Section 33.13/19 Feb 1965 Origina Rue Sma, medium, arge birds defined Section A6 Oct 1974 Concept of critica areas on engine introduced for arge bird Run-on after ingestion mandated Section A10 Mar 1984 Critica areas expanded to a bird sizes Section A20 Dec 2000 Medium bird increased to 2½b Ingestion at critica conditions Very significant increase in capabiity Section A24 Nov 2007 Large Focking Bird added to address Goose popuation growth Ros-Royce proprietary information Page 6 of 17 Dr J M Reed

8 2011 Bird Reguation Summary Chart b Large Birds 1x4 1x6 1x8 Large Focking Birds None 1x4 1x4½ 1x5½ Additiona Integrity Requirement None 1x2½ 1x2½+4x1½ 2x2½ 1x2½+6x1½ 1x2½+6x1½ 3x2½ 4x2½ Medium Birds 1x1 2x1½ None 2x1 1x12oz Inet Area m 2 3x1½ 4x1½ 1x2½+3x1½ 1x2½+5x1½ Notes Large Bird: Ingestion at 200kt and SLKPt. Safe shut-down. Large Focking Bird: Ingestion at 200kt and average fan speed. No more than 50% thrust oss aowed and run-on for 20 minutes (different schedue to medium bird). Additiona Integrity Requirement: Ingestion at critica forward speed and SLKPt. Demonstrate that engine does not ose more than 25% thrust and does not shut-down. Medium Bird: Ingestion at critica forward speed and SLKPt. No more than 25% thrust oss aowed and run-on for 20 minutes (different schedue to arge focking bird). Sma Bird: One 85g bird per each fraction of 0.032m 2 up to a maximum of 16. Same conditions and pass/fai as for medium Page 7 of 17 Dr J M Reed

9 Bird Popuation Considerations 1.5b medium bird test accounts for ~67% of bird popuation 2.5b medium bird test accounts for ~92% of bird popuation To gain a further 1% of bird popuation (1.1% increase in capabiity) test mass 2.9b 16% increase in energy Law of diminishing returns appies here 2.5b We Geared Return Poory Geared Return Ros-Royce proprietary information Page 8 of 17 Dr J M Reed

10 Monte-Caro Technique Summary The Monte-Caro technique depends on severa things: Description of a process (such as bird strike) mathematicay - Weight of bird - Location - Speeds - Geometry of engine etc Distributions describing the input parameters A random number generator These parameters can be combined to generate in the case of Ros-Royce an impact energy Repeating the process many times gives a picture of the range of impact energies that an engine is ikey to see as it continues to ingest birds Comparing the energies to a test standard enabes assessment of singe/mutipe engine power oss rates Ros-Royce proprietary information Page 9 of 17 Dr J M Reed

11 Monte-Caro Technique Output Tabe contains normaized singe engine power-oss rates for categories of interest may be used as probabiities Rue Year Inet Area (m^2) < > ???? Note improvement in situation particuary after 2001 These factors used with feet cyce data to cacuate risk Red denotes NTSB area of interest after Hudson River Ros-Royce proprietary information Page 10 of 17 Dr J M Reed

12 Cacuation Process The feet historica cyces data is maintained in a spreadsheet For each aircraft/engine combination inet size is known, 1 6 For each aircraft/engine combination EIS date is known, 1 7 A standard ingestion rate of 1/5000 aircraft cyces is assumed A ook-up tabe for inet size and EIS date is used to return the appropriate engine shut-down (ESD) probabiity Thus for each aircraft/engine combination for each month the number of ESD is cacuated Data is then summed across the entire feet for each year to provide a tota risk Data is then divided by number of fights per year to obtain the per cyce evauation Ros-Royce proprietary information Page 11 of 17 Dr J M Reed

13 Resuts Risk cacuated using the feet cyce data in conjunction with the Monte-Caro generated power-oss rates Rue change dates annotated at date of incorporation Ros-Royce proprietary information Page 12 of 17 Dr J M Reed

14 Observations As of 2011 the genera trend in risk is downward Due in part to much oder engines being retired Due in part to engines designed to more recent rues being introduced This means that we are yet to see fu benefit for rue changes aready made i.e. it takes many years for the fu benefit of rues to be seen New products are not introduced immediatey there is a rue change Introducing new rues does not introduce step changes in risk eve i.e. the curve is smoothy transitioning Ros-Royce proprietary information Page 13 of 17 Dr J M Reed

15 Looking Forward In order to assess future trends, need three pieces of information Rate at which new aircraft are introduced Which aircraft are ikey to be retired Which engine sizes wi be required for repacement aircraft Assumed 25% of feet wi have been repaced by 2030; of which, 5% very arge, 10% corporate, 10% regiona Ros-Royce proprietary information Page 14 of 17 Dr J M Reed

16 Risk Prediction for Next Two Decades Prediction performed for 3 main cases: 1; Od aircraft retire; repaced with existing feet mix 2; Od aircraft retire; repaced with 2007 certificated products 3; Od aircraft retire; repaced with 2011 certificated products Ros-Royce proprietary information Page 15 of 17 Dr J M Reed

17 Observations Over the next 20 years the risk curve begins to assymptote This is a function of Increased number of feet cyces year on year A greater proportion of the feet being certificated to the same rue standard The degree of improvement for a rue change is very sma This effect wi be more marked as yeary feet cyces increase i.e it becomes more difficut to achieve a significant feet percentage for new products The effect of any rue change is not seen for ~20 years after it is made This effect wi be more marked as yeary feet cyces increase as above Ros-Royce proprietary information Page 16 of 17 Dr J M Reed

18 Concusions A method has been deveoped to enabe numerate assessment of risk for different scenarios The resuts show that a change in engine certification bird rues wi not deiver a significant risk reduction in the short to medium term More timey measures must therefore take priority Risk is a product of engine robustness and number of strikes per aircraft cyce engine robustness is ceary eveing out The more effective risk reducer must be to reduce the number of strikes Product safety remains the number 1 priority within Ros- Royce; the rue assessment process is propery supported Ros-Royce proprietary information Page 17 of 17 Dr J M Reed