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CASE STUDY

MSC Software: Case Study - ADA

Certifed To Fly

Case Study: Aeronautical Development Agency

Key Highlights:

Industry

Aero

Challenge

Determine unsteady air loads due to the

structural vibration modes at various

altitudes and speeds

MSC Sotware Solutions

Patran to create a FE model, check the

quality of the data and the import proces

MSC Nastran Aeroelasticity to determine

unsteady air loads due to the structural

vibration modes at various altitudes

and speeds.

Benefts

Accurate FE Model Reproduction

Reliable Analysis

Improved Design Process

Fighter aircrat typically carry a number o

dierent under-wing external stores such as uel

tanks, bombs and missiles. The geometrical

and inertial parameters o these stores have an

inuence on the ight envelope and the utter

characteristics o the aircrat. An imported

aircrat is certifed by the OEM or the carriage

o certain stores within a specifed envelope.

However, i the country which has acquired the

aircrat decides to integrate a new store, then it

has to either approach the OEM to help in the

certifcation process or devise a mechanism to

carry out the exercise itsel. The ormer approach

has a twoold disadvantage viz. violation o

secrecy and also the prohibitive cost. Hence, it isimperative that an independent approach, along

with the local certifcation authorities, be evolved

to achieve the required objective.

Assisting with Flight Certifcation

One o the aircrats in the inventory o the

Indian Air Force had to be integrated with a new

store which the aircrat under consideration

was not certifed to y with. At this juncture

the Aeronvvautical Development Agency

(ADA), located at Bangalore, was approached

or assisting in obtaining the necessary ight

certifcation. ADA was established in 1984

to oversee the design and development o

the Light Combat Aircrat, Tejas During the

course o this program, ADA has acquired

expertise in various areas o Computer Aided

Design (CAD), Computer Aided Engineering

(CAE), Computer Aided Manuacturing (CAM),

Avionics, Systems, Independent Validation and

Verifcation and Flight Simulation. One o the

areas in which ADA is acknowledged as an

authority in the country is in the area o Loads,


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CASE STUDY

2 | MSC Sotware

MSC Sotware: Case Study - Aeronautical Development A

FE model o the aircrat generatedrom accelerometer locations in GVT

Dummy fnite element model o aircratrequiring utter clearance

Structural Dynamics and Aeroelasticity. The

group which is responsible or this task is

part o the Airrame Directorate o ADA. This

group was charged with the responsibility

o ormulating a strategy or obtaining the

clearance or integrating the new store on

the aircrat under consideration. The task o

ormulating the strategy and implementing it

to certy the aircrat with the new store wascompletely handled by Mr. Dhandabani V, Dr.

Hemalatha E and Mr. Kamesh J V o ADA and

Shripathi V o CSM Sotware, Bangalore, India.

CSM sotware is a provider o Engineering

Services and also a business partner o MSC

Sotware. Through its partnership with MSC

Sotware Corporation, CSM has helped many

companies accelerate innovation and generate

a higher return on investment.

This case study primarily dea ls with the

clearance o the Altitude Mach No. envelope

o the aircrat, with the new store, which is

essentially based on utter computations.

The Novel Methodology

The method deve loped by ADA takes advan-

tage o the act that utter computations are

carried out in the modal domain and that modal

parameters can also be generated by Ground

Vibration Tests (GVT). GVT data is normally

used to measure A ircrat modal characteristics

and to veriy and update analytical vibration

models. In GVT testing, sot support systems

are used to simulate the unconstrained bound-

ary conditions that an aircrat experiences

during ight. The aircrat is excited through the

use o electrodynamic shakers. Accelerometer

are used to measure the response o the

structure. A data acquisition and analysis

system is used to acquire the data and extract

modal parameters rom measured data.

ADA analysts validated the new method on

an aircrat (Aircrat-1) or which a complete FE

model was available. They created a dummy

FE model o this aircrat in Patran with a smallnumber o nodes; one or each accelerometer

used in GVT. The nodes were connected with

2D CQUAD and TRIA elements. Mode shapes

were visualized in Patran to check the quality o

the data and the import process.

MSC FlightLoads was used to create a 2D

aerodynamic model using plan orm geometry.

The aerodynamic and structural models

were then coupled or utter computations at

The excellent correlation between FE based utter analysis and utter

analysis based on GVT data validated the use o this method on the

second aircrat, the one with a new store requiring utter clearance.


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Aerodynamic model o aircrat used or validation Aerodynamic model o second aircra t

Flutter results based on ull FE model vs. resultsobtained rom GVT data or the validation study

Altitude

Flutter CharacteristicsDetailed FE

Flutter Analysis

Model Based

on GVT Data

Mach Freq

(Hz)

Mach Freq

(Hz)

Low 1.39 12.7 1.41 13.04

Medium 1.69 12.7 1.54 12.5

High 2.18 12.7 1.88 13.03

Flutter speed and requency or aircratrequiring utter clearance

Altitude

Flutter Characteristics (Mach)

Store 1 New Store Store 2

Low 2.66 1.68 1.52

Medium 3.01 1.89 1.55

High 3.57 2.31 1.69

the required altitude and speed levels. MSC

Nastran Aeroelasticity I and II were used to

determine the unsteady airloads due to the

structural vibration modes at various altitudes

and speeds.

The MSC Nastran Direct Matrix Abstraction

Programming (DMAP) module was used to

update the structural model by replacing

the modal mass, stiness and mode shape

matrices with the data measured in GVT. The

DMAP module provides the ability to modiy

MSC Nastrans prewritten solution sequences

or write customized solution sequences to

solve specialized problems. DMAP delivers a

high-level, exible, and powerul programming

language that allows users to expand MSC

Nastrans capabilities by writing their own

applications and installing their own custom

modules. DMAP has its own grammatical rules

and compiler built inside o MSC Nastran that

provide matrix operations or the manipulation

and creation o data blocks or use by MSC

Nastran or other programs.

The methodology described above was used to

predict the utter characteristics o the aircrat

or which FE data was available using MSC

Nastran Solution 145 or utter analysis. The

utter results using GVT data also matched up

well to those obtained rom the FE model as

shown in Figure 4. The Mach numbers show

the speeds at which the analysis predicted that

utter would occur.

Application o the Methodology toAircrat under Consideration

The excellent correlation between FE based

utter analysis and utter analysis based on

GVT data validated the use o this method on

the second aircrat, the one with a new store

requiring utter clearance. The same method

described above was used to calculate the

utter characteristics o this second aircrat.

Figure 7 shows the primary utter speeds

and requencies obtained rom the analysis at

dierent altitudes or the new store. The result

show that the utter speed o the new store lie

between two previous certifed stores, Store 1

and Store 2, in the majority o cases. Based o

this study the certifcation authorities cleared

the aircrat or carrying the new store.

The method o us ing GVT data to drive a FE

analysis has been used previously but this

application is believed to be the frst time that

utter clearance has been based on GVT data

This approach made it possible to quickly and

efciently evaluate the utter perormance o

the aircrat with the new store.

CASE STUDY

Case Study: Aeronautical Development Agency

MSC Sotware: Case Study - Aeronautical Development Agency


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CASE STUDY

Europe, Middle East,

Arica

MSC Sotware GmbHAm Moosel d 1381829 Munich, GermanyTelephone 49.89.431.98.70

Asia-Pac ifc

MSC Sotware Japan LTD.Shinjuku First West 8F23-7 Nishi Shinjuku1-Chome, Shinjuku-KuTokyo, Japan 160-0023

Telephone 81.3.6911.1200

Asia-Pac ifc

MSC Sotware (S) Pte. Ltd.100 Beach Road#16-05 Shaw TowerSingapore 189702Telephone 65.6272.0082

Corporate

MSC Sotware Corporation2 MacArthur PlaceSanta Ana, Caliornia 92707Telephone 714.540.8900www.mscsotware.com

The MSC Sotware corporate logo, MSC, and the names o the

MSC Sotware products and services reerenced herein are trademarks

or registered trademarks o the MSC Sotware Corporation in the United

States and/or other countries. All other trademarks belong to their

respective owners. 2011 MSC Sotware Corporation. All rights reserved

ADA*2011AUGUST*CS

About MSC Nastran

Accurate, Efcient & Aordable Finite Element Analysis

MSC Nastran is the worlds most widely used Finite Element Analysis

(FEA) solver. When it comes to simulating stress, dynamics, or vibration

o real-world, complex systems,

MSC Nastran is still the best and most trusted sotware in the world

period. Today, manuacturers o everything rom parts to complex

assemblies are choosing the FEA solver that is reliable and accurate

enough to be certifed by the FAA and other regulatory agencies.

Engineers and analysts tasked with virtual prototyping are challenged

to produce results ast enough to impact design decisions, and accu-

rate enough to give their companies and management the confdence

to replace physical prototypes. In todays world, nobody has time or

budget to spend evaluating the accuracy o their FEA sotware you

need to know its right.

About Patran

CAE Modeling and Pre/Post Processing

Patran is the worlds most widely used pre/post-processing sotware

or Finite Element Analysis (FEA), providing solid modeling, meshing,

and analysis setup or MSC Nastran, Marc, Abaqus, LS-DYNA,

ANSYS, and Pam-Crash.

Designers, engineers, and CAE analysts tasked with creating and

analyzing virtual prototypes are aced with a number o tedious,

time-wasting tasks. These include CAD geometry translation, geometry

cleanup, manual meshing processes, assembly connection defnition,

and editing o input decks to setup jobs or analysis by various solvers.

Pre-processing is still widely considered the most time consuming

aspect o CAE, consuming up to 60% o users time. Assembling

results into reports that can be shared with colleagues and managersis also still a very labor intensive, tedious activity.

Please visitwww.mscsotware.comor more case studies

About MSC Sotware

MSC Sotware is one o the ten original sotware companies and the

worldwide leader in multidiscipline simulation. As a trusted partner, MSC

Sotware helps companies improve quality, save time and reduce costs

associated with design and test o manuactured products. Academicinstitutions, researchers, and students employ MSC technology

to expand individual knowledge as well as expand the horizon o

simulation. MSC Sotware employs 1,000 proessionals in 20 countries.

For additional inormation about MSC Sotwares products and services,

please visit: www.mscsotware.com.

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