d2-7 john crocco - full spectrum crashworthiness criteria methodology

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Full Spectrum Crashworthiness Criteria Methodology

John Crocco Aviation Applied Technology Directorate Session 4 Analytics 2:15-2:50

DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.


Outline

Background History of Crash criteria

Overview Full Spectrum Crashworthiness effort

Crashworthiness Index methodology

Summary


Chronology of Crashworthy

Design Criteria


Army Crashworthy Helicopters

Army helicopters designed using military crashworthiness guidance

UH-60 Black Hawk AH-64 Apache RAH-66 Comanche ACAP (S&T)

Army helicopters designed to FAA standards

(CFR part 27)

UH-72 Lakota

(Eurocopter EC145)

ARH-70 Arapaho

(Bell 407)

Crashworthy features on other

helicopters:

Stroking seats Occupant restraints Wire cutters Cockpit airbags Fuel systems

MIL-STD-1290ADS-36


MIL-STD-1290 Requirements

Current Crash Criteria / Design Guidance

Summary of crash impact design conditions from MIL-STD-1290 (AV)

UH-60, AH-64 size

Rigid Surface requirement (landing gear absorb large % of energy)

SDGW

Crew, not occupant protection


Historical Data

CRI Study Army '80-'85 Army '71-'76 Navy '72-'81 Civil '74-'78

Rigid 16.4 14.2 8.0 21.7 19.8

prepared surfaces 16.1 13.0 7.0 17.9

ice 0.3 1.2 1.0

hard ground 17.9

flight deck 1.1

runway 2.7

frozen 1.3

offshore rig 0.6

Water 2.3 1.6 2.0 45.7 11.3

water 2.3 1.6 2.0 11.3

open sea 38.0

shallow water 3.8

deep water 2.7

river 1.1

Soft Soil 76.5 78.0 49.0 15.2 40.1

sod 66.4 63.0 43.0

bog 6.0

soggy 10.1 15.0

soft ground 10.3

desert 3.8

marsh/swamp/mud 1.1

soft 40.1

Other 4.7 6.3 41.0 17.4 28.8

snow 4.7 6.3 1.0 0.5 4.3

trees 30.0

in trees 0.5

through trees 4.9

dense woods 1.6

vegetation 15.9

rocks 10.0 2.2

ravine/steep slope 7.6

uneven ground 8.6

Safe, Inc


Outline




Summary


Why New Crash Criteria

Operating realities Current criteria only applicable to small to

medium sized aircraft (AH-64, UH-60)

Aircraft fly over a range of operational weights

Majority of crashes on sod and water

Troops in back need protection

Future Vertical Lift requirements Joint Multi Role, Joint Future Tactical Lift

Size, weight, mission, cargo retention, troop protection

High weight variability full fuel / cargo vsempty fuel / cargo

Class IV UAVs - No occupant but high value payloads

60000

70000

80000

90000

100000

110000

120000

130000

Gro

ss

We

igh

t (l

b.)

Center of Gravity

A

A'

B

B'

Fuel Burn Large Variationin Gross Weight

Uniqueness of unconventional rotorcraft is not represented in current criteria

Current criteria optimized for point design, not operational variability

Technology improvements Analytical methods (Large deformation finite element modeling)

Materials

Adaptive systems (structures, rotor blades, seats)

Energy absorption (e.g. external airbags)

Digital flight controls (blade control, optimize descent path)


Task Objective:

Develop rotorcraft crashworthiness criteria for a wide range of classes (Class

IV-VI), configurations (conventional, tilt-

rotor and tandem) and crash conditions

Full Spectrum Crashworthiness

Products:

Design guidance for future rotary wing aircraft

Varied impact surfaces, payloads, etc.

Multipoint design

Methodology to evaluate crashworthy designs

Technology and modeling roadmap

Impacts:

Improved crash survivability of rotary wing vehicle occupants

Reduced loss of high value payloads

Applicable to existing or new platforms across rotorcraft classes

Efforts FY08 FY09 FY10

Future Op Environ

Wt, CG, surface variability

System level approaches

Technology survey

Current criteria review

Mishap study

M&S assessment

Criteria development


FSC Conclusions - Kinematics

Vertical impact velocity increases

post in-flight impact

Aircraft weight at impact varies

greatly, yet trend is

toward increasing

weight.


FSC Conclusions - Kinematics

Pitch and Roll at impact can affect

performance of crash

systems


FSC Conclusions - Surfaces

Army data fairly consistent over time

Considerably different than Navy & civil data

The future CONOPs environment could change this trend, as Joint aircraft and missions could increase water mishaps with Army rotorcraft.


Outline




Summary


Definition of Crashworthiness

Index

The quantitative measure of a rotorcrafts crashworthiness based on various: Environments Conditions Systems

Weighting factor based on what is desirable to the customer Requirements Specific Operational

Environment

Historical mishaps

n

n

nn fWCI1

*

nW

nf


Occupant Protection

Determines Crashworthiness

Human tolerance limits Lumbar loads

Head Injury Criteria (HIC)

Chest loads

Survivable volume (%)

Ability to egress (time, hatches)

Requirements are based on ensuring occupant protection during the entire crash event.


FSC Methodology

Describe performance requirements

Prioritize

Missions Impact surfaces Value of capability

Demonstrate Capability

Calculate CI based on:

PrioritizationsCapability

Iterate based on changes

over the life of the a/c

Government / Customer

Contractor / Designer


CI Calculation Example

Scenario: Customer description of performance requirements

A vertical lift rotorcraft is needed to carry cargo, troops, and vehicles.

Maximum cargo weight is on the order of 30 tons.

Maximum range is 400 miles,

Maximum endurance time is 8 hours.

Aircraft is to be Joint, will focus on Army system

The primary mission is cargo resupply, followed by vehicle transport, followed by troop transport.


e.g.:

A value of 0.5 is obtained by

achieving 26 ft/s capability, 1.0 for

95th percentile of mishaps.

No value is assigned for capability

below 26 ft/s,

More value for providing capability

above the 95th percentile.

26 ft/s = .5

Value (V)=.5 + [(1.0-.5)/(95-83)] x (92-83) = .875 .87595%=1.0

Customer Prioritizes Capability


Rigid 16.4 / (16.4+2.3+76.5) = 0.172

Water 2.3 / (16.4+2.3+76.5) = 0.025

Soil 76.5 / (16.4+2.3+76.5) = 0.803

CRI Study Army '80-'85 Army '71-'76 Navy '72-'81 Civil '74-'78

Rigid 16.4 14.2 8.0 21.7 19.8

prepared surfaces 16.1 13.0 7.0 17.9

ice 0.3 1.2 1.0

hard ground 17.9

flight deck 1.1

runway 2.7

frozen 1.3

offshore rig 0.6

Water 2.3 1.6 2.0 45.7 11.3

water 2.3 1.6 2.0 11.3

open sea 38.0

shallow water 3.8

deep water 2.7

river 1.1

Soft Soil 76.5 78.0 49.0 15.2 40.1

sod 66.4 63.0 43.0

bog 6.0

soggy 10.1 15.0

soft ground 10.3

desert 3.8

marsh/swamp/mud 1.1

soft 40.1

Other 4.7 6.3 41.0 17.4 28.8

snow 4.7 6.3 1.0 0.5 4.3

trees 30.0

in trees 0.5

through trees 4.9

dense woods 1.6

vegetation 15.9

rocks 10.0 2.2

ravine/steep slope 7.6

uneven ground 8.6

Safe, Inc

Surface Factors (SF)

The impact surface

weighting factors are

decided by the customer.

In this case, the mishap

percentages from the

recent SAFE, Inc. mishap

study are used.

Customer Prioritizes Impact Surface


Customer prioritizes missions: % time conducting a specific mission

At the same time, designer identifies variations under each mission that affect crashworthiness:

Gross Weight, CG, % time in a weight / CG condition (per mission),

Customer Prioritizes Missions

Mission#1 45%

Mission #2 20%

Mission #3 35%

Combined Sum = 100%


Combination of all missions adds up to various weight / CG configurations that will need to be

analyzed on various surfaces and at various pitch / roll conditions.

Can be reduced and simplified to sixor less configurations

10 conditions

x 3 surfaces

x 6 positions in pitch/roll

= 180 analysis runs

6 conditions

x 3 surfaces

x 6 positions in pitch/roll

= 108 analysis runs

Missions Reduced

120000 22 13 0 0 0 0

110000 0 13 0 0 0 0

90000 0 0 0 18 0 30

70000 0 0 0 0 5 0

540 600 660 720 780 840

GW

CG STA

Analysis Prioritization


Capability on surface (ft/sec)

Pitch / Roll CapabilityF indicates full pitch and roll capability (MIL-STD-1290A) PR Weighting Factor=1.0

L indicates level only capability PR Weighting Factor=.72

Aircraft, EA systems, Surface, and Occupant Models

Low Probability

conditions

Simplified

conditions

FULL SPECTRUM

Rigid

120000 L L

110000 L F

90000 F F L

70000 F F L

540 600 660 720 780 840

Water

120000 F F

110000 F F

90000 F F F

70000 F F F

540 600 660 720 780 840

Soft_Soil

120000 L L

110000 F F

90000 F F L

70000 F F F

540 600 660 720 780 840

CG STA

GW

GW

GW

CG STA

CG STA

Rigid surface performance (ft/sec)

120000 20 22

110000 25 26

90000 29 28 32

70000 30 32 36

540 600 660 720 780 840

Water surface performance (ft/sec)

120000 25 27

110000 30 31

90000 34 33 37

70000 35 37 41

540 600 660 720 780 840

Soft_Soil surface performance (ft/sec)

120000 30 32

110000 35 36

90000 39 38 42

70000 40 42 46

540 600 660 720 780 840

GW

CG STA

GW

CG STA

GW

CG STA

Designer Demonstrates Aircraft

Capability


e.g.:

A value of 0.5 is obtained by

achieving 26 ft/s capability, 1.0 for

95th percentile of mishaps.

No value is assigned for capability

below 26 ft/s,

More value for providing capability

above the 95th percentile.

Water

120000 25 27

110000 30 31

90000 34 33 37

70000 35 37 41

540 600 660 720 780 840

GW

CG STA

26 ft/s = .5

Value (V)=.5 + [(1.0-.5)/(95-83)] x (92-83) = .875 .87595%=1.0

Value of the Sink Speed Capability


Calculate the weighted average of capability for a given mission

Score = (0.172 x PRrigid x Vrigid) + (0.025 x PRwater x Vwater) + (.803 x PRsoil x Vsoil)

Total combined score can then be calculated

Score variation indicates loss in

fidelity due to simplifying mission

profiles

Mission 2

120000 0 0 0 0 0 0 Sum 0.758378

110000 0 0.245339 0 0 0 0

90000 0 0 0.086441 0.042323 0 0.239757 Score 75.83777

70000 0 0 0 0.047149 0.097368 0

540 600 660 720 780 840

GW

CG STA

Missions Combined

120000 0.078316 0.053243 0 0 0 0 Sum 0.652025

110000 0 0.06484 0.03 0 0 0

90000 0 0 0.047543 0.112156 0 0.186668 Score 65.20252

70000 0 0 0.030873 0.00943 0.041381 0

540 600 660 720 780 840

Missions Reduced

120000 0.085085 0.056503 0 0 0 0 Sum 0.639267

110000 0 0.091126 0 0 0 0

90000 0 0 0 0.152363 0 0.205506 Score 63.92667

70000 0 0 0 0 0.048684 0

540 600 660 720 780 840

CG STA

GW

CG STA

GW

(out of 100)

Summation of the CI


Outline




Summary


Summary

Historical studies show need for better crash criteria

Future requirements need better crash criteria

Methodology to evaluate rotorcraft crash performance to meet those needs

has been described.


Questions

For more information:

CRI Final Reports available from AATD

CI calculation tool also available

System Crash assessment tool available

SAFE, Inc. Final Report on DTIC (ADA508186)

Complete FSC Criteria to be released (Draft available on www.dodtechipedia.mil)

d2-7 john crocco - full spectrum crashworthiness criteria methodology

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