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Occupant Range Expansion for In-Service Ejection Seats James Pearse Martin-Baker Aircraft Co. Ltd. 2
The Challenge Majority of in-service ejection seat systems were developed against the RAF aircrew population More recently requests are received to expand this boarding range, drivers include; Political or operational requirements to reduce barriers to population range entering flight training Population variation in international export sales of aircraft; Typically lightweight pilot populations (India, Asia, etc) can be as much as 14kg lighter at the mean Typically heavyweight pilots populations (USA, etc) are up to 5% heavier at the mean 3
140 SAFE Europe: 30 th March 2010 Example Aircrew Boarding Mass Ranges 130 Aircrew boarding mass (kg) 120 110 100 90 80 70 60 50 Mk10 (Typical) Mk16L (Typical) Boarding Mass = Pilot plus Aircrew Equipment Mass 4
Governing Factors Occupant range is governed by a number of competing variables, including; Ejection gun velocity for aircraft tail clearance and Zero-Zero performance Ejection gun phase acceleration experienced by the occupant Parachute inflation and descent rate Centre of gravity of the ejected mass (seat and occupant) 5
Governing Factors Occupant range is governed by a number of competing variables, including; Ejection gun velocity for aircraft tail clearance and Zero-Zero performance Ejection gun phase acceleration experienced by the occupant Parachute inflation and descent rate Centre of gravity of the ejected mass (seat and occupant) 6
Ejection Gun Performance Metrics The ejection gun propels the seat from the aircraft With a ballistic seat this is the only propulsion system on the seat With a rocket assisted seat the ejection gun and under-seat rocket motor consecutively provide seat propulsion Two critical ejection gun performance metrics Final velocity the higher the better for seat performance Most critical for the heaviest seat occupants Peak acceleration, as measured by the Dynamic Response Index (DRI) the lower the better for injury risk Most critical for the lightest seat occupants These design metrics conflict with each other so a balance between final velocity and peak acceleration has to be found 7
Ejection gun performance metrics Dynamic Response Index DRI The ejection gun acceleration profile physiological performance assessed through the Dynamic Response Index (DRI) criterion The ejection gun acceleration-time history is passed through a filter that models the response of the human lower spine The peak value of DRI is related to the risk of lower spine injury Non-permanent vertebral injury The Mil-Spec aim for rocket assisted seats is for the DRI to Not exceed 18 at normal equipment temperature Not exceed 22 at elevated equipment temperature 8
Ejection gun performance metrics Dynamic Response Index DRI g 25 limit at elevated temperarure 20 limit at normal temperarure maximum value = DRI 15 10 5 DRz acceleration 0 0.00 0.05 0.10 0.15 0.20 time from ejection gun initiation (sec) 9
Enhanced ejection gun technology Conventional ejection gun and cartridges Un-choked cartridges Pressure in cartridges is, or can be, the same as that in the ejection gun tube Nitrocellulose Primary cartridge Auxiliary cartridge Ejection gun with choked primary cartridge Pressure in primary cartridge chamber is de-coupled from the pressure in the ejection gun chamber Primary cartridge acts as a pure gas generator Primary cartridge propellant burns at its optimum pressure Extruded Double Base propellant (Nitrocellulose & nitroglycerin) Auxiliary cartridge 10
Enhanced ejection gun technology Benefits of using a choked cartridge ejection gun Less variability of performance over Crew mass range Temperature range Imposed aircraft acceleration range Can accommodate a wider aircrew mass range while meeting : Physiological acceleration limits (DRI) with low mass occupants Minimum ejection gun velocity requirement with high mass occupants 11
Governing Factors Occupant range is governed by a number of competing variables, including; Ejection gun velocity for aircraft tail clearance and Zero-Zero performance Ejection gun phase acceleration experienced by the occupant Parachute inflation and descent rate Centre of gravity of the ejected mass (seat and occupant) 12
GQ5000 Parachute Low descent rate 19 glide angle, as deployed 31 glide angle when additional drive / steering selected Very stable during descent Rigging-lines-first deployment - no lines taut snatch load The GQ5000 is fitted to Two Mk 10 seats (retro-fit) Mk 14 seat / US Navy NACES All Mk16L seat variants 13
Parachute Descent performance Parachute descent rate at sea level (m/sec) VERTICAL COMPONENT 10 8 7.0 m/sec limit 6 4 2 GQ1000 GQ5000 Example Current BA10LH Current Max Max Target Max 0 40 50 60 70 80 90 100 110 120 130 140 150 Total suspended mass (kg) (crew + flight clothing + survival kit + harness) 14
GQ5000 parachute GQ5000 addresses high parachute inflation g issues for extended boarding masses Peak parachute inflation g is lowered and acceptable throughout Escape envelope Expanded boarding mass range 15
GQ1000 parachute Canopy first deployment GQ1000 parachute 16
GQ5000 parachute GQ5000 parachute is designed to be deployed rigging lines first This requires that the parachute be packed in a sleeve The sleeved parachute is then packed into the parachute container (headbox) 17
GQ5000 parachute Rigging lines first deployment GQ5000 parachute 18
Governing Factors Occupant range is governed by a number of competing variables, including; Ejection gun velocity for aircraft tail clearance and Zero-Zero performance Ejection gun phase acceleration experienced by the occupant Parachute inflation and descent rate Centre of gravity of the ejected mass (seat and occupant) 19
Occupant Position With introduction of smaller crew, occupant position adjustment is required for two reasons; Anthropometric Allows smaller crew to achieve the correct eye height and/or reach foot and hand controls for normal flight activities Mass properties Restores the seat/occupant centre-of-gravity location with lower mass crew to acceptable position for ejection performance Removable spacers or actuating backrest Spacer back cushion or actuating backrest moves occupant mainly forwards in crew station Spacer base moves occupant mainly upwards in crew station 20
Ejection Performance example spacers (cushions) Smaller, lower mass occupant will increase thrust line offset Excessive thrust line offset will result in increased rearward pitch; Affects parachute deployment Risk of parachute entanglement 21 Thrust line offset Rocket motor thrust line Reduced thrust line offset
Developing and Qualifying the Modification System Modelling Tools MBA developed Seat Model Seat6D Ejection Gun Model Thermodynamic Pyrotechnic Model Seat6D Flexible 6 degree of freedom model Can be configured for any seat / aircraft / flight condition Monte-Carlo analysis assessment of real life variability Variation of certain parameters within a known / given probabilistic range 22
Ejection Seat System Simulation 23
Developing and Qualifying the Modification Development testing of ejection gun solution Slave seat ejection gun testing Ballasted to represent CoG and MoI of seat and occupant Reduced variability Reduces testing hardware costs 24
Example of Slave Seat Ejection Gun Test 25
Developing and Qualifying the Modification Qualification testing Net Tests Ejection gun tests of seat and instrumented ATD Ejection gun phase only Test seat and occupant recovered in catch net Further qualification testing Requirements for further ejection or Ballistic Signal Transmission System (BSTS) tests would be assessed dependant upon level of change or similarity to previously qualified solutions 26
Thank you for your time any questions? 27