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September 2005 The Implications of Handling Qualities in Civil Helicopter Accidents Involving Hover and Low Speed Flight Daniel C. Dugan, NASA CDR Kevin.

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Presentation on theme: "September 2005 The Implications of Handling Qualities in Civil Helicopter Accidents Involving Hover and Low Speed Flight Daniel C. Dugan, NASA CDR Kevin."— Presentation transcript:

1 September 2005 The Implications of Handling Qualities in Civil Helicopter Accidents Involving Hover and Low Speed Flight Daniel C. Dugan, NASA CDR Kevin J. Delamer, USN GOVERNMENT INDUSTRY ACADEMIA NRTC

2 September 2005 WHEN HELOS GO BAD

3 September 2005 Introduction Background Analysis Results Stability Augmentation Directional Control Teetering Rotors Instrument Flight Conclusions Recommendations

4 September 2005 KEY’S STUDY Army Helicopters Hover in DVE (Night, Dust, …) Equipped with Rate Command SAS “Marginal” HQ

5 September 2005 AH-64A / OH-58D UH-60 / CH-47D U.S. Army Helicopter Mishap Causes Hovering Flight Data from David L. Key, “Analysis of Army Helicopter Pilot Error Mishap Data and the Implications for Handling Qualities,” 25th European Rotorcraft Forum, Rome, Italy: September 14-16, Data from 276 Mishaps in Hovering Flight,

6 September 2005 ADDITIONAL STUDIES SURVEYED “U.S. Civil Rotorcraft Accidents ” - Harris, Kasper, Iseler “Analysis of US Civil Rotorcraft Accidents, Iseler and DeMaio …….” “Final Report of the Helicopter Accident Analysis Team,” DOD, FAA, and NASA “Near Term Gains in Rotorcraft Safety Strategies for Investment” - Workshop

7 September 2005 HARRIS, KASPER, ISELER Fatalities 228 Serious Injuries 319 Helicopters Destroyed 1114 Total Mishaps Piston and Turbine Rotorcraft All Flight Regimes All Flight Regimes 13.2 % Due to Loss of Control 13.2%

8 September 2005 THIS STUDY 547 Accidents, Hover or Low Speed, (Gyrocopters not Included) 126 or 23% attributed to Loss of Control which could be attributed to poor HQ 127 Fatalities, 97 Serious injuries, and 134 Helicopters destroyed

9 September 2005 HOVER AND LOW AIRSPEED MISHAPS Handling Qualities issues accounted for a greater percentage of Hover mishaps than mishaps overall (23% versus 13%) 547 Mishaps Reviewed 126 Due to Loss of Control (HQ) 126 Due to Loss of Control (HQ) 15 Manufacturers* 15 Manufacturers* Over 30 Models Over 30 Models 23 % * - All kit / homebuilt included as one manufacturer

10 September 2005 STABILITY AUGMENTATION HELICOPTER IN HOVER VS. AIRPLANE FAR 27 SFENA MINI-STAB HELISAS

11 September 2005 EXTERNAL LOAD OPERATIONS 15% MISHAPS 6% FLIGHT HOURS FATALITIES 30% 85 Mishaps 85 Mishaps 38 Fatalities 38 Fatalities 26 Serious Injuries 26 Serious Injuries 26 Helos Destroyed 26 Helos Destroyed

12 September 2005 Mission Analysis Personal Use and Instructional Flights Accounted for Almost Half of the Mishaps While Accounting for Only 15% of Flight Hours* * - Utilization Rates from FAA Aerospace Forecasts 48.2%

13 September 2005 DIRECTIONAL CONTROL LOSS OF TAIL ROTOR EFFECTIVENESS AC “UNANTICIPATED RIGHT YAW IN HELICOPTERS” MORE CRITICAL IN HOVER AND LOW SPEED FLIGHT FACTORS: WIND DIRECTION DIRECTIONAL CONTROL POWER AND CONTROL MARGINS POWER APPLIED (COLLECTIVE PITCH) PILOT SKILLS AND EXPERIENCE

14 September 2005 LTE PERCENTAGES Initial Data Survey Hover/Low Airspeed Mishaps - 45 LTE Related (15%) - 45 LTE Related (15%) Expanded Data Set- 547 Hover/Low Airspeed Mishaps - 82 LTE Related (15%)

15 September 2005

16 MISHAPS BY TYPE ROTOR SYSTEM Number of Mishaps 56 %

17 September 2005 TEETERING ROTORS ( Author’s Opinion/Experience) PROS Rugged Construction Blade Retention Failures Rare Start/Stop in High & Gusty Winds Not Susceptible to Ground Resonance Cost/Low Complexity CONS Susceptible to Mast Bumping - Usually Fatal in Flight Control Lags - can Induce PIO Vibration (Two Blade Systems)

18 September 2005 MAST BUMPING - CAUSES & AVOIDANCE ABRUPT, EXCESSIVE AND UNCOORDINATED CYCLIC CONTROL INPUTS SIDESLIP AFT CENTER OF GRAVITY LESS THAN 1G FLIGHT RESULT: LARGE ROTOR FLAPPING ANGLES - HUB TO MAST CONTACT POSSIBLE

19 September 2005 HELISAS HeliSAS – R44 Installation 12 Pounds 12 Pounds Approximately $30,000 Approximately $30,000 Two Servo-actuators, Cockpit switches Two Servo-actuators, Cockpit switches and Gyro Package and Gyro Package * - Pictures and system description, [12 Sep 2005]

20 September 2005 CONCLUSIONS IT REMAINS PUZZLING WHY HANDLING QUALITIES HAVE NOT BEEN PINPOINTED AS ACCIDENT CAUSES OR FACTORS A SIGNIFICANT NUMBER OF THE ACCIDENTS STUDIED COULD HAVE BEEN PREVENTED BY IMPROVED HANDLING QUALITIES THE INFERENCE IS THAT A SIGNIFICANT REDUCTION IN ACCIDENTS, INJURIES, AND PROPERTY DAMAGE COULD BE ACHIEVED BY THE INTEGRATION OF STABILITY AUGMENTATION SYSTEMS INTO THE CONTROL SYSTEMS OF THE LOWER PRICED HELICOPTERS

21 September 2005 RECOMMENDATIONS THE FEASIBILITY OF INCORPORATING LOW COST, LIGHT WEIGHT STABILITYAUGMENTATION SYSTEMS SHOULD BE EXPLORED BY HELICOPTER MANUFACTURERS REPRESENTATIVE CLASSES OF LIGHT PISTON AND TURBINE POWERED HELICOPTERS SHOULD BE EVALUATED BY THE GOVERNMENT TO ASSESS AND DOCUMENT HQ DEFICIENCIES


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