vibration behaviour of external payload on rotorcraft
TRANSCRIPT
Vibration Behaviour of
External Payload on Rotorcraft
Schmid David
RUAG Switzerland Ltd
Division Aviation
Torino, 23.04.2013
03.05.2013 RUAG Aviation 2
Content
About RUAG
ISSYS Pod Purpose and Structure
Project Goal
Dynamic Model
Vibration Tests
Comparison of Test and Simulation
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RUAG Aviation:
Independent Life Cycle Support Business and military aircraft MRO
Final assembly, MRO and upgrades, authorized service
centre for various aircraft types (F/A-18, F5, Cessna,
Piaggio, Bombardier, Dassault, Dornier 228 and NG
and many more)
Components and subsystems
Development of new structures and products,
engineering of modifications & repairs for existing
aircraft, Static & Fatigue Testing of Coupons and Mid-
Size Components, Wind Tunnel facilities
EASA Part 21 Subpart G, EASA Part 21 Subpart J, EASA
Part 145, FAR-145, Type Certificate Holder Do 228
ISO 9001, EN 9100
Based in: CH, DE, USA, 1980 employees
Net sales: CHF 487 million
EBIT: CHF 22 million
Proportion R&D: 12%
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ISSYS Pod
Self Protection System against guided missiles integrated
into a mobile pod
Pod is attached to the aircraft with an interface adapter
customized for each aircraft type
Interchangeable between aircraft in a short time by ground
personnel
Lower cost of pod versus fully integrated system
Pod system remains the same for all helicopter types, only
interface adapter needs to be redesigned
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ISSYS Pod
Missile Approach
Warning Sensor (2x)
Radar Warner (2x)
Laser Warner (2x)
Countermeasure
Dispenser
Avionics (EWC, PCU,…)
inside Pod
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Interface Adapter – UH-1D
2 Milled Brackets
(Pod-Side)
2 Milled Brackets (A/C-
Side) 8 Adjustable Length Push-Pull
Rods
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Project Goal
Develop an analysis model to accurately predict eigenfrequencies of
system for new interface adapters and different pod configurations
Challenges:
System non-linearity due to non-linear force-deformation curve of struts
and freeplay between struts and other structure
Short engineering cycle – no time for large engineering tests
Conventional FE analysis (static & eigenmodes) not adequate
Large amount of design constraints & requirements
Solution:
Use MotionView / MotionSolve to simulate vibration behaviour of
system
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Design Constraints & Requirements
UH-1D Interface Adapter
Pod position must be adjustable in all 6 degrees of
freedom within certain range
Lightweight (max total weight of LH & RH adapter is 7kg)
Pod position far aft and outboard relative to the hardpoint
positions due to passenger sliding door
Large tolerances of A/C hardpoint positions (absolute and
relative)
Adapter – Pod system must avoid main rotor frequency
bands
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Analysis Work Flow
Component (Strut)
Test Data
Static Analysis FE
Models
CAD Model
Dynamic Model
Vibration Test
Dimensions /
Component
Masses
Force –
Displacement
Curve
Deformable
Bodies
(FlexPrep)
Validate
Model
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Dynamic Model – Assembly
Non-Linear
Spring-Damper
Elements
(Struts)
FlexBodies
(from static
model using
FlexPrep)
Point Mass
(Magazine
with Flares)
User Configured
Analysis Flow
Simulating Real
Installation Work Flow
Simulated
Exciter Input
(White Noise)
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Dynamic Model – Static Checks
Pod Mass
Static Analysis (1g Gravity) shows good correlation between test and
model
Test Model D
Pod 47.5 kg 47.2 kg <1%
Mag w Flares 9.93 kg 9.93 kg 0%
Total 57.43 57.13 <1%
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Vibration Tests
Strain Gage Time History Data
(1 configuration only)
Frequency Response
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Sample Result: Z - Axis – Full Magazine
Sensor: Envelope Z-Axis
Configuration: CIDAS 100 Light LH
Full Magazine (36 Standard Flares)
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Summary
First two modes predicted accurately without model tuning
(D<5%)
Third mode prediction less accurate (D~15%)
Model is easy to set-up and modify
Model not yet ready for standalone prediction, still some
tests needed for simulation of new interface adapter
designs, but helps tremendously during design phase