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AD/A-U01 754

DESIGN, DEVELOPMENT AND QUALIFICATIONTESTING OF THE U. S. NAVY NES-21APARACHUTE ASSEMBLY

Jon T. Matsuo

Naval Aerospace Recovery Facility

Prepared for:

Naval Air Systems Command

July 1974

DISTRIBUTED BY:

NatioMu Technical Imon ServiceU. S. DEPARTMENT OF COMMERCE

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TECHNICAL 'REPORT NO. 1-74

NOTICES

Qualified requestors may obtain copies of this report from the Defense Documen-tation Center. Cameron Station, Alexandria, Virginia 22314. Department ofDefense contractors must be established for DDC sorvices or have "need toknow" certified by cognizant military agency of their project or contract.

DDC release to NTIS is not authorized.

When U.S. Government drawings, specifications, or other data are used for anypurpose other than a definitely related government procurement operation, thegovernment thereby incurs no responsibility nor any obligation whatsoever;and the fact that the government may have formulated. furnished, or in anyway supplied the said drawings, specifications, or any other data is not to beregarded by implication or otherwise, as in any manner licensing the holderor any other person or corporation or conveying any rights or permission tomanufacture, use or sell any patented invention that may in any way be relatedthereto.

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REPOT DCUMNTATON AGEREAD WSTNUCT1ONSREPWCIM ENTTIONPAG BEORECOAIPLFTU4G FORM1. s~oOTmum001 . GOVT ACCESSION No. I RECIPIENT'S CATALOG MUMMER

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4. TITLE (and~iite.J S TYPE OF REPORT a PERIOD COVERED

Design, Development and Qualification Testing of FinalThe U.S. Navy NES-21A Parachute Assembly 6 P911:IIRP G 004. MIkPORT NSUMBER

7.ATOR~e) 0. CONTRACT ORt GRANT Numeaf~s)

Jon T. Matsuo NAVAIRSYSCOM WR 1-8 110

9. P111FORUNOW OWGANI&ATIOON NAME1 AND ADDRESS 10 :PIOGMAM tLE1111NT. PROJECT. TASKC

Naval Aerospace Recovery Facility CRA a WORIC UNIT? NUMSERS

El Centro, California 92243

It. CONTROLLING OFFICE NAME &NO ACOOI'SS t1S. RIPORT CATC

Naval Air Systems Commrand JulyI O 19AGE

Washington, D. C. 20360 I3514. MN#UTORMNG AGIENCY NARC A1 ADOORISS~o duffer.en from, CorihwoJlfsj Offce.) It SECURITY CLASS. (of OlAS. repoev)1UNCLASSIFIED

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to. cosTsRuvoITOm STATIEMENT (of #Al. Roponij

Qualified requestors may obtain copies of this report from the DefenseDocumentation Center, Cameron Station, Alexandria, Virginia 22314. Depart-ment of Defense contractors must be established for DDC services or have"Need to know" certified by cognizant military agency of their project or contract

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Parachute QualificationParachute, Seat TypeAircrew Escape

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This report covers the design, development, and the U. S. Navy ServiceQualification Program conducted on the NES-21A personnel parachute assembly.The NES-21A assembly was designed by personnel of the NAVAERORECOVFAC(Naval Aerospace Recovery Facility) for use in ejection seats of U.S. Navy

B-31 and QT-33A aircraft. The NES-21A design objective was to provide a re-

trofitable replacement for the existing NS-3 personnel parachute assembly which

DO D " 14 73 EDITION4 OF INOV GS IS O@SOLETE ,UCLSZ ~SECURITY CLASSIFICATION OF T4IS PAGE (When Coee Ent

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would operate with a decreased opening time. This factor wouldimprove aircrew survivability in the low speed, zero altitudeoperational envelope. This improvement was accomplishedprincipally by the incorporation of a 40-inch diameter internalpiiot cnute and main canopy PDVL (Pull Down Vent Lines).

The qualification testing program was based on MIL-STD-85"8."Testing Standard for Personnel Parachutes". Because theNES-21A parachute assembly is identical in many respects to theexisting NS-3 parachute assembly, many testing requirementswere satisfied by virtue of its high content of similiar,previously qualified components.

The NES-21A parachute assembly will perform satisfactorily aspresently designed, in the QT-33A or T-33B aircraft (with T-

33B Airframe Change No. 187 incorporated) at 90 KrAS (KnotsTrue Airspeed) and above, for ground level and higher altitudeejections.

UNCLASSIFIEDSeCumT CLAWFIC*70I OF Too PAO&MM

/

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TECHNICAL REPORT NO. 1-74

U.S. NAVAL AEROSPACE RECOVERY FACILITYEl Centro, California

DESIGN, DEVELOPMENT AND QUALIFICATION

TESTING OF THE U.S. NAVY NES-21A PARACHUTE ASSEMBLY

by

Jon T. Matsuo

This Technical Report has been reviewed and is approved:

D.A

Head, Engineering Department

H. C. FISH

Technical Director

CAPT C. E. RICH, USNCommanding Officer

July 1974

/


ABSTRACT

This report covers the design, development, and the U.S. Navy ServiceQualification Program conducted on the NES-21A personnel parachute assembly.The NES-21A assembly was designed by personnel of the NAVAERORECOVFAC(Naval Aerospace Recovery Facility) for use in ejection seats of U.S. Navy T-33Band QT-33A aircraft. The NES-21A design objective was to provide a retrofitablerepla.-.ment for the existing NS-3 personnel parachute assembly which wouldoperate with a decreased opening time. This factor would improve aircrew surviv-ability in the low speed, zero altitude operational envelope. This improvementwas accomplished principally by the incorporation of a 40-inch diameter internalpilot chute and main canopy PDVL (Pull Down Vent Line).

The qualification testing program was based on MIL-STD-858, "Testing Standardfor Personnel Parachutes". Because the NES-21A parachute assembly isidentical in many respects to the existing NS-3 parachute assembly, manytesting requirements were satisfied by virtue of its high content of similiar,previously qualified components.

The NES-21A parachute assembly will perform satisfactorily as presently designed,in the QT-33A or T-33B aircraft (with T-33B Airframe Chanae No. 187 (incorporated)at 90 KTAS (Knots True Airspeed) and above, for ground level and higheraltitude ejections.

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TABLE OF CONTENTS

Page

List of Illustrations ivList of Tables Vi

Glossary of Terms viiIntroduction 1

Background 1Purpose 1

Description of Equipment Tested 1General IScope of Tests 7

Methods of Test 11Data Acquisition and Reduction 1]

Space Positioning 1]Telemetric Equipment 11Photographic Equipment 12

Test Methods and Procedures 12Ejection Tests 12

Test Equipment 12Test Procedure 12

Airdrop Torso Dummy Tests 13Test Equipment 13Test Procedures 13

Live Jump Tests 14Test Equipment 14Test Procedures 14

Test Results and Discussion 14Ejection Seat System Tests 14Torso Dummy Airdrop Tests 22Live Jump Tests 25Test Data Comparison 25

Conclusions 26Recommendations 29

iii


LIST OF ILLUSTRATIONS

Figjure Page

1. NES-21A Personnel Parachute Assembly 2

2. Pilot Parachute and Connector Strap Assembly 3

3. Pull Down Vent Lines 4

4. NES-21A Container Assembly (Inside) 5

5. NES-21A Container Assembly (Outside) 6

6. Model 7000 Automatic Parachute Actuator 8

7. NES-21A Parachute Harness Assembly 9

8. Back Cushion, Seat Pan Assembly, LRU-7/P Life Raft 10and Emergency Oxygen Cylinder

9. Ejected Seat Tests, NES-21A Parachute Assembly, Opening 15Time (Pack Open to Canopy First Full Open) versus Airspeedat Pack Open

10. Ejected Seat Tests, NES-21A Parachute Assem.bly, Altitude 16Loss During Opening (Pack Open to Canopy First FullOpen) versus Airspeed at Pack Open

11. Torso Dummy Tests, NES-21A Parachute Assembly, Opening 17Time (Pack Open to Canopy First Full Open) versus Airspeedat Pack Open

12. Torso Dummy Tests, NES-21A Parachute Assembly, Altitude 18Loss During Opening (Pack Open to Canopy First Full Open)versus Airspeed at Pack Open

13. Torso Dummy Tests, NES-21A Parachute Assembly, Maximum 19Opening Force Versus Airspeed at Pack Open

14. Torso Dummy Tests, NES-21A Parachute Assembly, Typical 20Total Riser Force versus Time

iv


LIST OF ILLUSTRATIONS (Cont'd)

Figure

15. Torso Dummy Tests. NES-21A Parachute Assembly. Maxi-mum Opening Force Rate of Onset versus Airspeed atPack Open 1 21

i6. Live Jump Tests, NES-21A Parachute Assembly, OpenTime (Pack Open to Canopy First Full Open) versusAirspeed at Pack Open 23

17. Live Jump Tests, NES-21A Parachute Assembly, AltitudeLoss During Opening (Pack Open to Canopy First FullOpen) versus Airspeed at Pack Open 24

18. Comparison of Opening Time (Pack Open to Canopy FirstFull Open) versus Airspeed at Pack Open of VariousCurrent Escape System Parachute Assemblies 27

19. Comparison of Altitude Loss During Opening \Pack Opento Canopy First Full Open) versus Airspeed Pack Open ofVarious Current Escape System Parachute Assemblies 28

v


LIST OF TABLES

Table

I Test Results of N."S-21A Parachute Assemblies Ejected From 30Navy F-9 Aircraft Using T-33 Ejection Seat

11" Results of Aerial Drop Tests of NES-21A Parachute Assemblies 31Launched at 3,000-ft. Altitude With 263-lb Gross WeightTorso Dummy

III Results of Live Jump Tests Using NES-21A Parachute 32Assemblies at Launch Altitude of 6,000 ft.

IV Results of Navy Aerial Drop Tests of Parachute Assemblies 33Equipped With Stencel Spreading Guns, Launched at 2,000-ft.Altitude, Ballistic Mode, 270-lb. Gross Weight

V Results of Navy Live Jump Tests From 5,000-ft. Altitude 34With Stencel Spreading Gun, Ballistic Mode, 3-SecondDelay, Less External Pilot Chute

VI Average Test Results (All Configurations) of U.S. Air Force 35Aerial Drop Tests Using Stencel Spreading Gun

vi


GLOSSAP" OF TERMS

Airspeed at Pack Open The airspeed (wind corrected) of the dummyV as

as determined from the cinetheodolite data at the

time the parachute pack opens.

Altitude Loss The vertical distance the dunimy travels during

a given interval.

Deployment Time The time interval between pack open and linestretch.

Dynamic Pressure One-half of the product of the air density and the

square of the airspeed.

Full Open The first moment that the canopy attains a full

hemispherical shape.

Gross Weight The total weight of the torso dummy and parachute

assembly.

Line Stretch The moment when the suspension lines are

initially observed to be fully extended afterquarter-bag separation.

Opening Force The maximum total force applied to the parachute

risers during inflation of the canopy.

Opening Time The time interval between parachute pack open

and canopy full open.

Pack Open The first instant that the parachute pack flapsare observed to open, or first instant pilot

chute is seen.

Snatch Force The total first peak force imposed on the risers

due to the sudden acceleration of the canopymass at line stretch.

vii

I


INTRODUCTION

Backsground. The NAVAERORECOVFAC was directed by Naval Air SystemsCommand to conduct a design and qualification program to update the presentT-33B aircraft ejection seat egress system, in order to improve the low speed/altitude egress performance. The design objective was to improve survivabilitywithin an ejection envelope of 90 KTAS and zero altitude AGL (Above GroundLevel); and 400 KTAS and 3,000-ft. altitude MSL (Mean Sea Level).

Principal features of the proposed improvement are: Multi-stage drogue parachutedesigned to provide improved seat/man stabilization and deceleration;40-inch internal pilot chute, and PDVL (Pull Down V-nt Line) to decrease thedeployment and development times respectively, of the main parachute.

Purpose. Purpose of the report is to present design and qualiiication performancedata resulting from testing of the NES-21A parachaite assembly. The NES-21Awas designed as a low cost, retrofitable parachute wvhich would improve theoperational envelope of the T-33 3ircraft ejection system, as compared to theexisting NS-3 parachute assembly.

DESCRIPTION OF EQUIPMENT TESTED

general . The NES-21A (Figure 1) evolved from, and thus is similar to thelatest configuration of the NS-3 parachute assembly currently used in the T-33series aircraft; both assemblies make use of several identical components.

1. The NES-21A assembly P/N 693AS103, -1 (regular), -2 (oversize), differsfrom the NS-3 P!N 2b4AS100-1 (regular) and 264AS109-1 (oversize) in thefollowing details:

a. 30-in. pilot chute is replaced with a 40-in. pilot chute (P/N 693AS106-1)(see Figure 2).

b. PDVL (F/N 693AS107-1) is added to the main canopy (see Figure 3).

c. Container (P/N 693AS104-1) (see Figures 4 and 5) is similar to the NS-3container (P/N 264AS101-1) but incorporates two additional stow loops toaccomodate the re-routed arming cable-hook assembly and housing of the

1


52 2S57

FIGURE NO. 1. NES-21A PERSONNEL PARACHUTE ASSEMBLY

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automatic parachute actuator (see Figure 6) to permit a more direct pullusing a floor-mounted attachment point, and one pack opening band (P/NMS70105-3) is added.

2. The NES-21A uses the following itcens which are identical to componentsof the NS-3 parachute assembly:

a. Harness (see Figure 7)

b. Back cushion, seat pan. life raft and emergency oxygen (see Figure 8).

3. The NES-21A zero delay lanyard subsystem differs from the currentzero delay lanyard and incorporates the following advantages per ACC (AircrewSystems Change) No. 181:

a. Eliminates the requirement for manual hookup at take-off with subsequentunhooking after tLPe-off and hookup during landing. The NES-2IA is engagedat all times thus unburdening the pilot and minimizing the human error factor.

b. Eliminates an approximate 300- to 400-lb. side load on the seat duringejection. It also places the lanyard/aircraft attachment along the longitudinalcent er line of the aircraft and seat, thus reducing the actuation force from 300-400 pounds to 10-20 pounds. The reduction in pull force improves ejectionperformance by eliminating eccentric loading that exists with ACC No. 181configuration. The actuation force (retardation force on the seat) is reducedto a value where it has no significant effect on escape performance.

4. The procedure for stowing canopy suspension lines in the parachute containerfor the NES-21A differed from the NS-3 in order to accommodate the PDVL usedto assist parachute deployment.

Scope of Tests. The NES-21A was developr1 and tested concurrently withthe T-33B ejection seat drogue parachute program.

In accordance with MIL-STD-858, "Testing St andard For Personnel Parachutes",the following standard methods far developmental and qualification testing ofman-carrying parachute assemblies were waived either entirely or partiallyon the basis that:

a. It is not a new concept (TiOl, T102, T103, T104, T105 and T107); and

b. Its similarity with qualified equipment (TM06, T108, T109, TI10,T,11 and T112 considering parachute assemblies NS-3, NES-8B with PDVL*and LW-3B with 40-in. pilot chute).

7

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ZERO DELAYLANYARDSNAP HOOK

ARMINGCABLE

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62-2480

FIGURE NO. 6. MODEL 7000 AUTOMATIC PARACHUTE ACTUATOR

8

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.CI.:iICALI . REPORT NO. 1-74

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MAIN (TYP)SLING R

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FIGURF NO. 7. .'1S 21A PARACIIT -E HARNESS ASSEMBL.Y

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SP-A SEAT PANEL ASSEMBLY

BACK CUSHIONASSEMBLY LRU-7/P RELEASES~HANDLE

RAFTEMERGENCY

OXYGEN CYLINDER62-2479

'IGURE NO. 8. BACK CUSHION. SEAT PAN ASSEMBLY, LRU-7/P LIFERAF'I AND EMERGENCY OXYGEN CYLINDER

10


Qualification was based on the results of the following tests to demonstratethe suitability oi the 40-in. pilot chute, addition of the PDVL and the redesignedcontainer:

a. Aircraft ground level and airborne ejection seat system tests wereconducted for qualification testing of the proposed T-33B ejection seat improve-ment program of which the NES-21A is a major component. Five preliminary

truck-launched ejection seat system tests were conducted to develop ande•,aluate systems effectiveness and test procedures. Seventeen airborneejection seat system tests (11 with drogue chute subsystem and 6 without)were conducted to evaluate seat-man collision and overall performanceeffectiveness. The airborne ejection seat system tests were made from therear seat of a Navy TF9J aircraft at speeds from 90 to 400 KIAS (Knots Indi-cated Airspeed) and altitudes rang;ng from zero feet AGL to 3,000-ft. MSL.

b. Airdrop tests using torso dummies were conducted for design evaluation,airblast integrity, performance evaluation, and qualification testing of theNES-21A. Fourteen torso dummy airdrop tests were made using Navy NU1B,C-47 and A-3B aircraft. All tests were conducted using main riser strain gagelinks to obtain individual riser forces during parachute deployment and develop-ment. Launch speed varied frow 90 to 170 KIAS with all drops Leing made at3,000-ft. MSL and a gross weight of 263 (t) 5 pounds.

c. Twelve live jump tests were conducted to man-rate the NES-ZIAparachute assembly. All live jumps were made from the Navy NUIB and C-47aircraft at 6,000-ft. MSL altitude, and at speeds of 44 to 90 KIAS.

METHODS OF TEST

Data Acquisitik i and Reduction.

1. Space Positioning. Askania and Contraves cinetheodolite cameras wereused on all tests (except the five ground level runway ej,;ction seat systemtests) to obtain event times, altitude losses, airspeeds, rates of descent anddynamic pressures. The data were corrected to compensate for surface windsand standard National Advisory Committee for Aeronautics day conditions.

A Bowen Model 6 acceleration camera operated at 60 f.p.s. (frames per second)was used on the five ground level runway ejection seat system tests to obtainevent times and altitude data.

2. Telemetric Equipment. TM (Telemetric Equipment) was used in conjunctionwith main riser strain gage links to obtain left- and right-hand riser forcesduring parachute deployment and opening for the torso dummy tests. Totalriser force time histories were obtained by electronic summation of left- and

right-hand riser forces.1]


3. Photographic Ecquipment. 16mm cameras were used on all tests for ground-to-air, plane-to-air, and air-to-air motion picture coverage. Color film wasexposed at rates of 50, 64, 100, 128 and 200 f.p.s. and still photographs were

taken to document rigging and damage using a press-type camera.

TEST METHODS AND PROCEDURES

Ejection Seat System Tests.

1. Test Equipment. The NES-21A was tested in its operational environmentas a component part of a proposed modified T-33B aircraft ejection seat egresssystem. The seat modifications primarily consisted of the addition of:

a. A rocket catapult

b. An automatic 0.5-second delay seat-man separation system

c. Seat bucket filler blocks

d. A seat drogue parachute system (except on six tests where no droguechute was used for comparative purposes); and

e. A center floor attach point for the automatic parachute actuator armingcable snap hook.

The tests results of the proposed modifications to the T-33B ejection seat egresssystem are the subject of a separate document NAVAERORECOVFAC TechnicalReport No. 6-74. Articulated dummies weighted either to 145 or 210 (+5)

pounds, were used for all ejection seat tests of the NES-21A.

2. Test Procedure. Seventeen T-33 ejection seat system tests were conductedwith the system being launched from the rear seat of a Navy F-9 aircraft.Test events/procedures were as follows:

a. At the proper time, an electrical circuit was closed and a pressurecartridge fired, which in turn actuated an M-28 gas initiator. This simultaneouslyfired the rocket catapult, the drogue gun assembly (except on six tests), and

the one-half-second time delay M-72 gas initiator of the seat/man separator

system.

b. Upward movement of the ejection seat in turn pulled the arming cable

of the NES-21A automatic parachute actuator equipped with a 2-second time

delay pyrotechnic carti'idge.

12


c. Approximately 0.2 seconds after the rocket catapult had fired, thedrogue gun (except on six tests) fired and deployed the drogue parachutecanopy. At approximately 0.5 seconds after rocket catapult actuation,seat/man separation and rocket burnout occurred.

d. The seat and dummy free-fell separately for approximately 1.5seconds. Approximately 2.0 seconds after first movement of the ejection seat,the automatic parachute actuator opened the NES-21A parachute container.

e. A spring-loaded, 40-inch diameter pilot chute deployed the standard28-ft. diameter, flat circular personnel parachute canopy with standard shortPDVL incorporated.

Airdrop Torso Dummy Tests.

1. Test Equipment. The test equipment consisted of a 263- (+5)-poundtorso dummy with telemetric cavity and a reserve recover- parachute; theNES-21A parachute assembly which had been modified to accept main riserstrain gage links and a 2-channel TM package. A NAVAERORECOVFAC-designed PDVL "daisy chain" manual release subassembly, and the standardU.S. Air Force 4-line (rear) release subassembly were incorporated duringfour tests (Nos. 1587, 1588, 0122 ard 0123) to check structural integrity andcompatibility of the release subassemblies with the NES-21A before the livejump tests were conducted.

2. Test Procedures. In tests conducted from the U-lB and C-47 aircraft,the torso dummies were launched individually from the side door. For thesetests, the dummies were placed in an upright position adjacent to the door andthen pushed out chest first. After exit of each dummy, the Model 7000 automaticparachute actuator oi the NES-21A (2-second time delay) and the F-lB automaticreserve parachute actuator (10-second time delay) were armed simultaneouslyby a static line 3 feet long.

In tests conducted from the A-3 aircraft, the dv~mmies were released individuallyfrom compartmented racks installed in the aircraft's bomb bays. The dummieswere positioned in the racks with the head toward the line of flight and theparachute container facing upward. After exit of the dummy, the same pro-cedures and equipment were used to arm the automatic parachute actuatorsas with tests from the U-lB and C-47 aircraft.

The TM equipment was calibrated and checked out immediately prior to eachlaunch.

13


Live Jump Tests.

1. Test Equipment. Each parachutist used a NES-21A assembly and worean underharness to which a reserve parachute assembly had been attached.

The NES-21A was modified to incorporate the PDVL daisy chain type ofmanual release and the standard Air Force rear suspension line releasesubassemblies previously tested on torso dummies. These modifications weremade to alleviate any dangerous canopy oscillations and to minimize thepossibility of ground impact injuries.

2. Test Procedure:. Each parachutist assumed the uncontrolled airborneposition - feet extended but together, head down looking toward feet, hands overreserve, elbows close to sides and torso bent slightly forward. After a timedelay of 2 to 5 seconds. the NES-21A parachute assembly ripcord handle waspulled manually.

The test parachutists were instructed to descend normally during the first1,000 feet and then to take whatever actiun they deemed necessary in an effort tominimize discomfort and avoid g,-ound impact injuries. A jumper's evaluationreport was submitted by all test parachutists, as a means of recording hissubjective evaluation

Test Results .And Discussion.

Ejection Seat System Tests. The test results and applicable remarks areshown in Table I. Figures 9 and 10 depict graphically the most pertinentdata.

The runway (ground level) ejection seat test results were not plotted ornFigures 9 and 10 because airspeed data required for specific events were notavailable. The opening time intervals (pack open to canopy first full open) wereconsistent with only 0.5 seconds difference between the slowest and thefastest. The altitude losses during the time intervals from pack open tocanopy first full open, varied from 8 to 64 feet. The 56-foot variation inaltitude loss is considered acceptable for the low altitude/low airspeed,pack open environment. The method of measurement used had an accuracyof + 5 feet.

Figure 9 depicts the opening time interval envelope (pack open to canopy firstf-"Jl open) versus airspeed at pack open. The variations in opening timeinterval are typical for uncontrolled pilot chute deployment.

14


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21

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Figure 10 depicts the altitude loss (during pack open to canopy first fullopen envelope) versus airspeed at pack open. The variation of 81 feet for theentire pack open airspeed range is not unusual for uncontrolled pilot chutedeployment.

Torso Dummy Airdrop Tests. Test results and applicable remarks for eachtest are presented in Table II. Figures II through 15 depict, in graphicform, the pertinent data from Table 11. Data from test No. 1584N were not usedbecause of major damage to 50 percent of the parachute drag surface.

Figure 11 depicts the opening time interval envelope (pack open to canopy

first full open) versus airspeed at pack open. The variations in openingtime interval are considered excellent.

Figure 12 shows the altitude loss (during pack open to canopy first full open)envelope versus airspeed at pack open. The 80-foot (maximum) variationfor the entire pack open airspeed range is considered excellent.*

Figure 13 depicts the maximum opening force envelope versus airspeed atpack open measured at the parachute risers. A typical force-time history isillustrated in Figure 14. The absence of any significant snatch force istypical of uncontrolled deployment.

Figure 15 shows the opening force rate of onset envelope (pounds per second)versus airspeed at pack open. For drop test No. 1590N (Figure 14), themaximum incrase in opening force was 4800 pounds during a period of 0.63seconds for an average value of 7,620 pounds per second. Bc:h the averagemaximum opening force and the average opening rate of onset of the NES-21A,when compared with the other Navy operational emergency personnel parachute

assemblies (at comparable pack open airspeeds) were:

a. Approximately the same as the NES-8B or NES-14A, which utilizesthe short PDVL;

b. Greater than the average maximum opening force and lower than theaverage opening force rate of onset of the NB-II, NES-12C, NES-15A, which

utilize the spreading gun.

*The use of aerodynamically clean torso dummies tended to downgrade the

significance of the relatively small variations when compared with tests inwhich articulated dummies were used.

22


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Live Jump Tests. Test results and applicable remarks for each test are pre-sented in Table III. The data from test No. 1577 were not used due to entangle-ment of the pilot chute with the parachutist and the main parachute canopy.Figures 16 and 17 depict graphically the pertinent data shown in Table III.

Figure 16 shows the opening time interval envelope (pack open to canopy firstfull open) versus airspeed at pack open. The opening time intervals variedfrom 1. 2 to 2.0 seconds or an 0.8-second maximum variation in, opening time.

Figure 17 shows the altitude lost during pack open to canopy first full openenvelope versus airspeed at pack open. The altitude lost varied from 79 to214 feet. The variation may be due to the body position of the acceleratingparachutist (either rapid or slow acceleration) and the initial effectivenessof the pilot chute (aerodynamic interference of the parachutist).

Although there is no specific limitation as to the maximum force (openingshock) or the force rate-of-onset imposed on the crewmember during parachutedeployment, it is believed that the NES-21A borders on the edge of safe, humantolerance levels of impact force in the head-to-toe axis. The test subjectswho parachuted using the NES-21A objected to the extreme opening shockdiscomfort and the extreme oscillations induced by the (unbroken) PDVL'swhich can cause nausea and injuries on ground impact due to unpredictablelanding attitudes. Both the opening force and the oscillation magnitude en-countered by the test parachutists were higher than desired but consideredacceptable since they are comparable to other Navy parachutes such as theNES-8B and NES-14A assemblies.

Test Data Comparison. As a means of evaluating the NES-21A performancedata noted in Tables I, II, and III, data from previous tests of similar contemporaryescape system parachute assemblies were reviewed on a comparative basis.Data from the following tests were used:

Table IV, Navy torso dummy drops of the NB-11 parachute assembly equippedwith the Stencel spreading gun and a 50-inch external pilot chute.

Table V, Navy live jump tests of NB-11 parachute assembly equipped withthe Stencel spreading gun but without an external pilot chute.

Table VI, Air Force Torso dummy tests using the Air Force, standard, free-type, back-style parachute assembly equipped with the Stencel spreading gunand without quarter-bag or external pilot chute. The assembly was packedin accordance with Air Force T.O. 14D1-2-81 except that the spreading gunwas Installed

25

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Navy NB-7 back-style modified parachute assembly* averaged test results of26 tests.

Figure 18 summarizes the opening time interval envelope of the NES-21Aassembly (from Tables I. II. and IIl) compared to the comparative data containedin Tables IV, V. and VI. It is considered impracticable to obtain parachutedeployment or development time intervals, when uncontrolled parachutedeployment is involved, because separation of the two specific phases is notpossible. The opening time interval (pack open to canopy first full open) of aparachute assembly versus pack open airspeed, was chosen as one of theprimary parachute performance comparison parameters. The NES-21Aand the NB-7 are considered to have uncontrolled parachute deployment and theStencel spreading gun-equipped assembly to have controlled parachute deploy-ment. The NES-21A had an equal or shorter opening time (pack open tocanopy first full open) at all test airspeeds at pack open when compared withcurrent Navy and Air Force parachute assemblies equipped with the Stencelspreading gun and that averaged by a Navy NB-7 parachute assembly.

Figure 19 depicts test data concerning the altitude lost during parachute packopen to canopy first full open envelope versus pack open airspeed for comparableparachute assemblies. The altitude lost during parachute opening for theNES-21A assembly equaled that for all test airspeeds at pack open, when comparedwith the Navy and Air Force assemblies equipped with the Stencel spreadinggun and the averaged Navy NB-7 parachute assembly.

CONCLUSIONS

1. The NES-21A parachute assembly will perform satisfactorily as presentlydesigned, in the QT-33A or T-33B aircraft (with T-33BAirframe Change No.187 incorporated) at 90 KTAS and above, for ground level and higher altitudeejections.

2. The standard, short, single-stage PDVL does decrease the opening tim. e(pack open to canopy first full open) of the NES-21A parachute assembly at alltested airspeeds.

3. The unbroken PDVL weak link is the cause of the very high canopyoscillations that occurred during descent.

*NAVAERORECOVFAC technical paper, "A Comparison of Parachute Opening

Shock Experience By Humans and Human Analogs", by Jon 0. Baldock, DonaldH. Reid, John A. Buckman, Joseph E. Doerr, and John D. Whitecar, dated1 October 1973.

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4. The NES-21A parachute harness (unchanged from the NS-3, NB-6, NB-8)is not optimized for high opening force parachute assemblies. The lack ofparachute canopy releases make this harness potentially dang'rous, particularlywhen high wind conditions during landing increase the danger of being dragged.

RECOMMENDATIONS

1. The NES-21A parachute assembly be adopted for Fleet operational use inthe T-33B and QT-33A aircraft when T-33B Airframe Change No. 187 (or equiva-lent) has been incorporated.

2. The standard, irt PDVL, common to many parachute assemblies, isacceptable but in ne nf improvements because:

a. The weak link . designed is too strong and is the primary cause of thehigh opening forces encountered at all tested airspeeds; and

b. The unbroken weak link is the cause of the very high canopy oscillationsthat occur during descent of the NES-21A parachute assembly.

3. The NES-21A parachute assembly harness should be replaced by the stand-ard MA-2 integrated parachute-restraint harness, for flight safety reasonsas stated in paragraph 4. of CONCLUSIONS above.

29

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