UNCLASSIFIED AD NUMBER LIMITATION CHANGESOpening; shocks, snatch forces, opening times, rates of descent, and. down times of a number of man-carrying, cargo, and extraetior parachutes

UNCLASSIFIED

AD NUMBER

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FROM:

AUTHORITY

THIS PAGE IS UNCLASSIFIED

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Approved for public release; distribution isunlimited.

Distribution authorized to U.S. Gov't. agenciesand their contractors; Critical Technology; NOV1966. Other requests shall be referred to AirForce Flight Dynamics Lab., Attn: Research andTechnology Division, Wright-Patterson AFB, OH45433. This document contains export-controlledtechnical data.

AFFDL ltr dtd 24 Jan 1973

'■'■" I ■ —» p»"-»-' "-

AFFDL-TR-66-103

00 W CALCULATED VALUES OF TRANSIENT AND STEADY STATE °* PERFORMANCE CHARACTERISTICS OF MAN-CARRYING, 0 CARGO, AND EXTRACTION PARACHUTES

EUGENE L. HAAK RICHARD V. HOVLAND

UNIVERSITY OF MINNESOTA

TECHNICAL REPORT AFFDL-TR-66-103

NOVEMBER 1966

This document is subject to special export controls and each transmittal to foreign governments or foreign nationals may be made only with prior approval of the Vehicle Equipment Division (FDF), Air Force Flight Dynamics Laboratory, Wright-Patterson AFB, Ohio.

AIR FORCE FLIGHT DYNAMICS LABORATORY RESEARCH AND TECHNOLOGY DIVISION

AIR FORCE SYSTEMS COMMAND WRIGHT-PATTERSON AIR FORCE BASE, OHIO

MM

■■■■■■'II ■!■

CALCULATED VALUES OF TRANSIENT AND STEADY STATE PERFORMANCE CHARACTERISTICS OF MAN-CARRYING,

CARGO, AND EXTRACTION PARACHUTES

EUGENE L. HAAK RICHARD V. HOVLAND

UNIVERSITY OF MINNESOTA

This document is subject to special export controls and <iach transmittal to foreign governments or foreign nationals may be made only with prior approval of the Vehicle Equipment Division (FDF), Air Force Flight Dynamics Laboratory, Wright-Patterson AFB, Ohio.

FOREWORD

This report was prepared by the Department of Aeronautics and Engineering Mechanics cf the University of Minnesota in compliance with U. S. Air Force Contract No. AF 33 (615)-2554, "Theoretical Deployable Aerodynamic Decelerator Investigations," Task 606503, "Parachute Aerodynamics and Structures," Project 6065, "Performance and Design of Deployable Aerodynamic Decelerators."

The work accomplished under this contract was sponsored jointly by U. S. Army Natick Laboratory, Depart- ment of the Army; Bureau of Aeronautics and Bureau of Ordnance, Department of the Navy; and Air Force Systems Command, Department ot* the Air Force and was directed by a Tri-Service Steering Committee concerned with Aero- dynamic Retardation. The work was administered under the direction of the Recovery and Crew Station Branch, Air Force Flight Dynamics Laboratory, Research and Tech- nology Division. Mr. James H. DeWeese was the project engineer.

This study was guided by Prof. H. G. Heinrich, with Mr. R. J. Niccum and Dr. R. E. Rose contributing significantly to its success. The authors also acknowledge the assistance rendered by students of Aerospace Engineering of the University of Minnesota.

The manuscript was released by the authors in April 1966 for publication as an RTD Technical Report.

This technical report was reviewed and is approved.

J2 - ._ SOLOMON R. METRES Acting Chief Recovery and Crew Station Branch AF Flight Dynamics Laboratcry

IX

■ Jim ^'W

ABSTRAGT

Opening; shocks, snatch forces, opening times, rates of descent, and. down times of a number of man-carrying, cargo, and extraetior parachutes are calculated on the basis of analytical equations and certain other assumptions. Comparisons of the calculated data with full scale experimental values are somewhat limited, but show reasonable agreement when available. This report represents a first step in an attempt to catalog full scale experimental values from which, eventually, more exact analytical methods can be derived.

iii

J

™~— ■■■■i ■! »wmî

TABLE OF CONTENTS

PAGE

I. Introduction 1

II. T-10 Personnel Parachute , . 2

III. T-10 Reserve Parachute, Chest Pack .... 8

IV. Maneuverable Personnel Parachute 14

V. Halo Parachute 18

VI. T-7A Cargo Parachute 23

VII. G-13 Cargo Parachute 28

VIII. G-12D Cargo Parachute (Platform Load) ... 32

IX. G-12D Cargo Parachute (A-22 Cargo Container; 37

X. G-11A Cargo Parachute 42

XI. Extraction Parachutes ...... 48

XII. Conclusion ..... 57

XIII. Reierences 58

Appendix 59

iv

;

TABLES

1

TABLE PAGE

I. Parachute Performance Characteristics of the T-10 Personnel Parachute 7

II. Parachute Performance Characteristics of the T-10 Personnel Reserve Parachute ... 13

III. Parachute Performance Characteristics of the Maneuverable Personnel Parachute . . . 17

IV. Parachute Performance Characteristics of the Kalo Free Fall Personnel Parachute . . 22

V. Parachute Performance Characteristics of the T-7A Cargo Parachute ......... 27

VI. Parachute Performance Characteristics of the G-13 Cargo Parachute 31

VII. Parachute Performance Characteristics of the G-12D Cargo Parachute-Platform Load . 36

VIII. Parachute Performance Characteristics of the G-12D Cargo Parachute - A-22 Cargo Container 4l

IX. Parachute Performance Characteristics of the G-11A Cargo Parachute 47

X. Parachute Performance Characteristics of the 15 Foot Ringslot - Extraction Parachute, Unreefed . 53

XI. Parachute Performance Characteristics of the 15 Foot Ringslot - Extraction Parachute, Reefed, Lj. = 260 in . 54

XII. Parachute Performance Characteristics of the 22 Foot Ringslot - Extraction Parachute ............. 55

XIII. Parachute Performance Characteristics of the 28 Foot Ringslot - Extraction

•"-I I" ■ «■ -*m

ILLUSTRATIONS

FIGURE PAGE

i. T-10 Personnel Parachute Deployment Sequence 4

2. T-10 Personnel Reserve Chest Pack Deployment Sequence , 10

3. Maneuverable Personnel Parachute Deployment Sequence 16

4. Halo Free Pall Personnel Parachute Deployment Sequence 20

5. T-7A Cargo Parachute Deployment Sequence 25

6. 0-13 Cargo Parachute Deployment Sequence 30

7. G-12D Cargo Parachute Deployment- Sequence ... 34

8. G-12D Cargo Parachute Deployment Sequence - A-22 Cargo Container 39

9. G-11A Cargo Parachute Deployment Sequence , 44

10. Ratio of Inlet Area to the Total Area as a Function of the Dimensionless Time, T 46

11. Extraction Parachute Deployment Sequence 51

vi

-—T—— iimwn Wim * ■»

c

(C])S)b

(CDS)C

(°Ds)max

Do

Pc

Fo

Ps

g

h

*]

Ll

Lex

Lr

Ls

mb

mc

P

P'

SYMBOLS*

effective porosity of canopy (Ref l)

drag coefficient based on canopy surface area, S0

drag area of suspended load

drag area of uninflated parachute canopy or deployment bag

maximum canopy drag area

nominal canopy diameter, v4 SQ/R

average canopy drag force

opening force of inflating canopy

snatch force

acceleration due to gravity

height or altitude

landing zone elevation

dimensionless factor used in determination of opening shock

length of static line

length of extraction line

length of riser

reefing line length

length of suspension lines

mass of suspended load

mass of parachute canopy

tractive force in suspension lines

breaking strength of suspension lines

impact pressure corresponding to the velocity

* under consideration of definitions of Ref 1

vii

T

t

tl

tf

V

V

1,1

1,2

VI,3

vn,i

SYMBOLS (CONT.)

surface area of canopy-

time ratio, t/tf

time

time at beginning of deployment (time for static line extension)

time required for suspension line extension (deployment time)

time at the end of suspension line stretch or snatch- force occurrence

time from release to end of suspension line extension

canopy filling time

filling time of pilot parachute

opening time for canopy

total time from release of parachute to touchdown

velocity of suspended load at time t^

velocity of suspended load at time t2

velocity of suspended load at time to,

velocity of parachute at time t^

velocity of parachute at time t2

Vjjj2(rel) velocity of parachute relative to suspended load at time t2

VII,3

vd

Ve

Vo

Vs

VT

*b

velocity of parachute system at time to

deployment velocity

equilibrium velocity for descent

launching velocity - aircraft velocity

velocity at suspension line stretch, snatch velocity

free fall terminal velocity

weight of suspended load

viii

SYTBOLS (CONT.)

w\

w.

^total

r ?

Pave

weight of canopy only

weight of complete parachute

number of suspension lines

total porosity

per cent elongation of suspension lines at P1

per cent elongation of extraction lines

air density

average air density between release altitude and landing zone elevatior

lx

■— III .11 ■ II ■ .1 ■ -I I I- I . 1-1 —»»-™

I. INTRODUCTION

In the following, an attempt has been made to calculate the transient and steady state Performance characteristics of several commonly used man-carrying, cargo and extraction parachutes.

The parachutes considered in this report are:

1) T-iO personnel parachute 2) T-10 reserve parachute 3J Two maneuverable parachutes h) T-7A cargo parachute 5) G-13 cargo parachute 6) G-12D cargo parachute

a) with a platform load b) with an A-22 cargo container

7) G-11A 8) Three standard ringslot extraction parachutes

The physical parameters, deployment systems, simplifying assumptions used in the calculations, governing equations, and results in the form of tables, are presented for each of the above parachutes.

The performance of these parachute systems is considered for an aircraft velocity range between 60 and 150 knots (TAS) at altitudes of 6,500 ft, 11,500 ft. and 20.000 ft (MSL)*.

In this report, all values of aircraft velocity and parachute system velocities as well as the related dynamic pressure are based on true airspeed conditions.

The respective drop zone elevations are 5.»000 f^, 10,000 ft, and 18,500 ft, yielding an actual altitude above terrain of 1500 ft. The calculations for the Halo parachute, a free fall deployment, employ .somewhat different altitude conditions which are noted where they occur.

The calculations are performed by neans of simplifying assumptions and methods which were considered and decided upon in cooperation with members of a Tri-Service Steering Committee and their staffs.

The more important equations and detailed explanations are presented in the Appendix. In many instances, these basic equations have been adjusted slightly to fit the particular parachute system. The.se variations are noted in the text.

*Mean Sea Level

II. T-10 PERSONNEL PARACHUTE

This is a parachute primarily used by airborne troops. Its principal characteristics are described in Ref 1, while the specific parameters important for this study are listed below.

A. Physical Parameters

Nominal canopy diameter, D0 = 35 ft - 10$ Plat Extended Skirt Canopy

Weight of suspended load, W^ = 250 lbs

Weight of canopy, Wc = 11.70 lbs Wp - 14.13 lbs

Canopy material, nylon cloth, MIL-C-7020, Type I, 1.1 oz/yd2 Nominal Porosity=72-132 (Assume 100)

Load Drag Area (CpS)^ = 6.0 ft2

Deployment bag drag area, (CpS)c = 1.925 ft2

Bag dimensions: Length, L = 22 in Width, W = 12 in Height, H - 5 in

d)bag =1,05 (Ref 2)

Number of suspension lines, Z = 30

Breaking strength of suspension -lines, P1 =375 lbs, Type II of spec. MIL-C--5040

Suspension line length, L = 25-5 ft

Static line length, L1 ■ 15 ft

Per cent elongation of suspension lines, >' = 32$ at rated breaking strength

Drag coefficient based on DQ, Q-Q =0.70

Dimensionless factor, K = 1.3

5. Performance Conditions

In view of the practical use of this parachute, the performance conditions for which the transient and steady state characteristics will be investigated are as follows:

■ I ■ ■

Altitudes:

h = 6,500 ft h - 11,500 ft h m 20,000 ft

These altitudes are defined as 1500 ft above terrain.

Aircraft Release Velocities:

V0 = 60 knots (TAS)

V0 - 90 knots (TAS) V0 = 120 knots (TAS)

V0 - 150 knots (TAS)

These conditions are the same for all parachute studies unless otherwise stated.

C. Deployment System

Thp T-10 personnel parachute is deployed by a static line one end of which is attached to the aircraft while the free end pulls the deployment bag, in which the parachute is located, off the back pack. Upon extension of the suspension lines, the deployment bag is separated from the parachute and the canopy is free to inflate. The deployment system is presented schematically in Pig 1.

D. Assumptions Used in Calculations

For the velocities, altitudes, and loading conditions, the following simplifications appear to be justified and are used:

1) The snatch force is assumed to be negligible.

2) The deployment and canopy filling occur in H near horizontal flight path, and trajectory curvature is neglected.

E. Governing Equations'1

The calculation of the performance characteristics is acconrolished in view of the following concepts.

l) The total line extension time, toj-, was calculated, assuming the jumper travels a length of Lj + Ls +

*See Appendix for a summary of equations.

3

" --••"—'■' ■"-"" "» ■'—■" ■■HM L INI- L . . I nnp| III

V DEPLOYMENT BAG

9 1. Canopy In Deployment

Bag 2. Canopy Pulla out of

Deployment Bag

3. Suepenslen Line« Tight 4. Canopy Fully Opened

LEGEND: A MAN WITH My BACK PACK

Fig. 1 T-10 Personnel Parachute Deployment Sequence

s

D0/2, acted upon by his own drag a"d gravity, after leaving the aircraft, by altering Eqn 1 of T.ht appendix to read:

Ll + Ls + &o ={ St-D

2\2

,"T7 +[Vo fcDt - Jl ln I1 + JlVotDtj (la)

The terms JN, JQ, and Jb are defined in the Appendix. Prom this equation, the time tnt was evaluated by an iterative process.

given: The velocity of the parachutist at this instant is

Since the snatch force is neglected for this type deployment, the main canopy begins to fill at this time. There is a short period of time neglected from Taen the canopy is first out of the bag in the sail" shape until it aligns itself along the trajectory. With this time neglected, the term, VT 2 is assumed to be the velocity at the beginning of the filling process.

2) The filling time, tf, for 10$ extended skirt canopies was determined in accordance with the method presented in Ref 3, leading to Eqn 3, which was solved* for tf by means of a computer.

f T=0. 2^ f

D0 = tf

where

T=0

5.271T^ + 2.597T + O.2587

_JL +of /S (M M „ T) + _RVg

Z1T \ N ^N R ' R , dT (3)

M = wtotal +fDo3 (0.009169T + 0.00006478)

N = O.OO9169 £D03

P = 0.00647 (CDS)max + (CDS)D

R . wtotal + 0.0005478 eD03

S = 0.1445 (CDS)max

*This and all other computer solutions mentioned in the following were performed at Research and Technology Division, Wright-Patterson Air Force Base, Dayton, Ohio.

wvmtmmwim ■ —H—W^M

Vs = snatch velocity = Vj 2

^ = density

tf - filling time

3) The opening force, F0, was calculated in accordance with Ref 4, where the maximum force is:

and

F0 = CD0S0^3 x K (4)

qs = impact pressure corresponding to the velocity, VR = V'

1*2 and x and K are dimensionless

factors for various types of parachutes.

4) The total opening time, tQ, is the sum,

t0 = tut + tf (5)

5) The rate of descent, or the equilibrium velocity, Ve, was determined from the force equilibrium, expressed as

Ve = D, o %CDo »tal (6) ave

where Pave is the average density between landing zone elevation"and release altitude, and W-fcotal *ö the total weight of the parachute and 'luspended load. This assumes that there is no a_ ,itude loss during the opening process. For the large cargo parachutes, however, where t0 is relatively large, this altitude loss may be significant.

6) The total down time, trp, is given

tT a t0 + -~- (7)

F. Results

The results of the performance calculations performed in accordance with the conditions explained above are presented in Table I.

H

pq < EH

pH o

co o H

co 5^ H B PC, X

a o <

o K < < PC P-, < a r3 o i ^< w s ü o a CO < K s W (X Pu o &H o K rH

w 1 PH EH

g o

P-,

• a —« «-C x t P p

p (1 o — Cw CM

CM a: o

o fc O O

O o o o in o •.

•* „ „ a Is- -=t aj o VO t~- o ITv CO O VO it c m If CM in ITi H CT> l-H rH CO rH r** co N it

IT1 rH CO h-J in OJ o Ch m rH ON CT ii

,—4

r-\ -—i CJ II r-l OJ OJ 11

, 1

1—i rH CM

x: •* p, ^ #k

c • x cr c G 0 <M 0) *tfe o O

■H (D SI —' •H nH p « fr. P -P cd >

cd >

CO

> 0) <D 0

■H iH rH w w w 0) * ' 0; 0 C fi r-1

■4

o o N

o a *-.

• X o bO <M 0 0 i hO hO

0 EH to ß c •H K-p ^ •W •H

-0

$ Ü

EH 0)

it it o\ CU L- O- o OJ ^ .3- Ch vo rH oo

• • cr,

• cn vo • •

rH • it 0^ • VC 1

-P Oj o Ch CG CO jH^ ■;n 00 OJ LO it 00 rr 00 fr- f- IS- '"V- >- !"- t-- VO vo vo VC

• 8* o Q-< 0 0 CO ee 00 OJ \0 -H r-H oo Ch vo rH CO o o ^ •V

KP *—• !—i H

o OJ

VC * * o t- VO 0J t"- CO o l>- o 0 00 Ci 1

II <M ° +> 2

IT h- •X) (—I II

rn vo oo c II

or) vo CM O • • • • • • • • • • • 1

CO OJ rH H H OJ —1 rH rH /•! rH 1—1 ,- x: v Ä r-1

•* ft .-- •V •\ <u • X o Q) 0

-Ö <M 0 0) •o •Ö 3 0 Q w 3 3 -p K-p •«-' P p ■pj ■H

-P •H P -P ^~s 03 H h- o Ch oo r-i VO Ch vo 00 \Q

H < Ö a)

CO • CU • VO * m rH < CO CO • • uo H

< CO 00 0-- • VC'

-P CO rH rH r-l iH rH H rH rH r-l H rH H Q) to Cd

'v~' CO

cd

0 CO cd *-> CO CO n , CO it it it it VC vc vo VC

0 \o M • • • 0 • V • » 0 • • • < H ,0) -P 0

P* <M CO Ch Ch cr, OA rH H rH rH rH rH it it it it

0 H r—' ~-4 H 0 OJ OJ CM 01 0 CM 01 0J OJ fC 1 ' K K

*— VO CO ^t UC CM Ch VC CL f-- vo 00 CM - o • a m • • • « • » • • •

.TO \ 0 CO in rH VX~ o CO in H CM 00 OJ O !> -p ra CO CM VC Ch CTi CM VO O Ch 00 ^~- H

CM H rH H H H OJ H rH ■0J ^-^ CO -p^

0 O CO o o o O o O O o o 0 0 O VO a\ OJ in VO Ch CM m vo Ch OJ X

.H H rH H rH rH v~ 1

— -

III. T-10 RESERVE PARACHUTE, CHEST PACK

The T-10 reserve parachute is an integral part of the T-10 troop parachute assembly, and the study of its transient and steady state performance characteristics has been accomplished essentially in the same manner as the one used in the preceding chapter, but because it is a canopy - first deployment, the snatch force cannot be neglected. In addition, this canopy is deployed by a pilot parachute, which is described and considered in the calculations.

A, Physical Parameters

1) Main Canopy

D0 = 2k ft - circular flat canopy

Wb = 250 lbs

Wc = 5.93 lbs

Wp =8.06 rbs

Canopy material, nylon cloth, MIL-C-7020 Type I, 1.6 oz/yd2 Nominal Porosity = 72-132

(CDS)b = 6.0 ft2

Uninflated canopy drag area, (CDS)C =2,2 ft2

Z = 24 suspension lines

P" - 550 lbs - Type III of Spec. MIL-C-5040

Ls = 20 ft

£' = 55% at rated breaking strength

K = 1.4

2) Pilot Parachute - AF Drawing 49J 7161

Do = 3 ft Plat octagonal

Material, nylon cloth, MIL-C-7020, Type I Nominal Porosity = 72-132 ft3/ft2-min.

Z = 8

P» = 100 lbs - MIL-C-5040B, Type I

8

■ü '*mw—r i "II I tmnkmm »

Ls = 31 in

B.

*' = 30% at rated breaking strength

CDo= 0.55

Deployment System

The T-10 personnel reserve parachute is deployed manually by a ripcord. This releases a spring-loaded pilot parachute which extracts the main canopy from the pack, followed by the suspension lines (Pig 2).

C. Assumptions Used in Calculations

The following simplifications are used:

1) Although it is realized that this canopy in an emergency use may deploy and open in vertical fall, the calculations of snatch force and filling time utilize the existing equations for a horizontal or near horizontal trajectory.

2) The opening shock of the pilot parachute is neglected, and it is assumed that at the time tfp, the pilot parachute is fully open and the deployment of the reserve parachute begins at this instant.

3) V0 is considered as the velocity of the system when the reserve parachute ripcord is pulled.

D. Governing Equations

As before, transient and s eady state performance characteristics are calculated in view of existing concepts and equations.

l) The pilot parachute filling time, tfD, has been calculated from Ref 7.

'f« ~

2 D o

P 3 V0n(-7% - $

The velocity of this instant is then given by:

(8)

vd = vlfl = vn#1 = jlVo t°p + r

and represents the system velocity when the main canopy begins to deploy.

(2)

.IUW.PUJMIJ ,,UII LI Uli . Ill *wfâ«m«i.i.uiipR.iiiPiii ii w ' "^msmtf^mm

■NMHoawa

¥ 1. Man Out of Aircraft 2. Pack Opened Manually and

Pilot Chute Released

LEGEND: 0 MAN WITH CHEST PACK

J$

3. Canopy Extracted by Pilot Chute

h. Canopy Filled

Pig. 2 T-10 Personnel Reserve Chest Pack Deployment Sequent

10

""—■■'■-*-■-■ ■ '■' ■" —~

f -—. i ■■ »■■^■■r iL.iniunyj.i ii»^ ■!■■■! in . ■

2) The time for suspension line extension, tp, can then be found by iteration of the equation

Ls = J^ ln (1 + JbVdt2) - j^ In (1 + JcVdt2) (9)

where the Jp cerm includes the drag areas of both the inflating canopy ana the pilot parachute.

Tiie velocities of the primary and secondary bodies3 man and reserve parachutes, respectively, at time t2, were determined from:

'1,2 - JbVf,*£ * 1

'11,2 ~ JcVdt2 + 1

VII,2(rel) " VI,2 " VH,2 and

VI,3 = VII,3 = VI,2 = Vt

(10)

(11)

(12)

(13)

3) The snatch force was determined from the following equation (Ref l),

Ps = P + Pc (14)

where the aerodynamic drag is

Pc =| (CDS)C-^ + V

~2~ (15)

and the dynamic force

P m cKl,2(rel)]ZP' (16)

4) tj)^ is the time from the release to the instant at which the deployment begins, tf^ plus the time for suspension line extension, tp.

fcDt = tfp + t2 (17a)

5) The filling time, tf, for circular flat canopies was determined by the method of Ref 2, and a computer solution for tf was obtained from

11

•'•Il ' ■-"' ' ' " I ■»—Li »■■

D0 = tf

J1

"r=°'3 T 1.873T2 + 2.96T + Ö.C886 t.

LW7 + 2 JN IN ln S " TJ + Tf j

dT (18)

with the parameters wtotal M

g + ^D0

3 (0.020624T + 0.0000264)

N - 0.020624 £D03

P - 0.003733 (CDS)max + (CDS)W

R = „total + 0.0000264 £D03

S = 0.12237 (CDS)max

6) The opening force, P0, was calculated by Eqn 4

7) The opening time, t0, is the t- me from release to the time the canopy is fully inflateo.

t0 - tDt + tf (5)

8) The rate of descent. Ve, was determined from the equilibrium conditions (Eqn 6; where Pave is the average density between release altitude and landing zone elevatior.i.

9) Total down time, tip, was determined by

-T - tO + -y^-

where "he veie-je altitude is 1500 ft above ground.

(7)

E. Results

The results of the performance calculations are presented in Table II.

12

H H

a < EH

• 0. -—! P P

p CD fl> *-^ Q-i c^ Q_ K O o

o O o o o

o ^ in - o r-> c r- r-1 o \p rH o O •* o OH cn vn •»

P? s CM ■A ac O rH co St ^J- CO CO 0- o h- CO in O VO oc m vo LP 0- CM rH VO un VO rH

» H CM AT II rH OJ ^f

II

rH

rH OJ ^r

£ X •v p. •* •* i

p • * cr* e C 0 <M CO =<fc o o ■H 6) o *—• TH Tt p Kfe p P cd >

nj >

cd >

0) CD 0 H O- a a in rH IT vo cn vo rH vo rH o Sf w

Bfc. % OJ ■^ N H w a; CO o^ o w rH 00 in CM 00 CM VO H o rH in o N- o ^t 00

CD P o

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' in ir IT in LO LP in in U'I m LP LP

• & o ft-i CD CD CD O CO «P *—

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O <D ^t- VO 0J cn LP vo CM o VO' 0- on o 4i CO • ■ • • • J • • • • • •

Cvi H H o OJ rH rH rH CVI H rH rH

P P Cw

P 4H

<M P.— • X CJ O O

O <w CD CD c o o CD «H CQ in o in K-P v-

H o vr ^-* -3- O" l> OJ rH m OJ t-- H CM (X H .p H

^ s ^ CO

LP O tN vo m O t— VO LP O f- X il • • • II » • • • II • • • •

rH r-i c o H rH o o H rH o o J3 **-* £

•* 1

p. *— CD • X o CD CD -o <H CD CD •0 •t) 3 CD P CO 3 3 P «■P *-- •P -p

•H p

■H P P ^-~ CM 00 rH 0- in

cn en CO CO 00 cn •=f on

rH P o ^J- -* N 0- H vo cn cn rH o cn -ti ^f < Q vo ^ o-^ <C H "• m ■=t

P CO a • 1 • • • • * • • • • 0) CO CO

o o o ° 0 CO cd o

o o o o CD CO cd CD

rH o o o

\o in IT LP m ^f zt ■3- * cn cn cn cn rH ,m P O • 4 1 • r-> >i • • • H • • • • Cy VO VO VO VO t- 0- 0- IV 0) a. a) ro co K *-* OJ CM CM CM

■

CM CM CM CM

cn tc CM CM CM CM

,_-^ in CO H ^t CM 0- no H r-i rH OJ O • • • * • • • ■ • * •

CO \ CD ^l- rH 'T VO LP* CM O 0- VO ^r OJ o ' F> P CO cn î" OJ 0") ay ■^■ cn a\ cn ^r cn it 4H H H CM rH rH CM rH H CM

■w*

CO p^

O 0 CO o Ü Ü O o Ü O o ü o o o vo O^ !M in vo cn CM u\ VÜ en CM m > H H H H rH rH

^^t

13

IV. MANEUVERABLE PERSONNEL PARACHUTE

With the advancement of parachute technology, maneuverable parachutes have come Into existence which, from the standpoint of aerodynamics, are highly interesting aerodynamic vehicles. The following studies, however, are merely concerned with the transient and steady state conditions similar to those considered in the preceding sections. Under investigation here is a modified T-10 troop type parachute.


Do = 35 ft - 10$ flat extended skirt canopy with cut-out in rear, static line deployment

Wb = 250 lbs

Wc = 11.87 lbs

Wp = 14.3 lbs

Canopy Material, nylon cloth, MIL-C-7020 Type I, 1.1 oz/yd2

(CDS)b = 6-0 ft2

(CDS)C = 1.925 ft2 (deployment bag)

Bag dimensions: Length, L = 22 in Width, W = 12 in Height, H = 5 in

CDbag = 1-°5 (Ref 2)

Z ■-= 30 suspension lines

pi = 375 lbs - Type II of Spec. MIL-C-5040

Ls = 25.5 ft

Lx = 15 ft

& = 32$ at rated breaking strength

CD0= 0.70

K = 1.3

B. Deployment System

Since this system is identical to the T-10 main canopy described in Section II, with the exception of a

14

—

cut-out area in the lower rear of the canopy, which removes only 3.7# of the canopy area, all calculations and results are identical* The system schematic (Pig 3) and the tabulated results (Table III) are included only for continuity.

I

15

— _

DEPLOYMENT SAG _ SUSPENSION LINES

— DEPLOYMENT BAG

1. Canopy in Deployment Bag 2. Static Line Tight

4. Suspension Lines Tif-ht

3. Canopy Alignment With Trajectory Angle

LEGEND: 4j MAN WITH BACK PACK

5. Canopy Fully Open

Fig 3. Maneuverable Personnel Parachute Deployment Sequence

16

—■' ■ ' ■

H H H

W a EH

O g CO p O E H O En < co cc H < K CM

o w «>; S K < o

< s § K W P-.

b W o < < a,

o CO

W CM o

a cq

s

17

V. HALO PARACHUTE

The Halo Parachute is the maneuverable parachute of TV above which, however, is deployed in free fall. Its characteristics are identified below.


1) Main Canopy

Do = 35 ft - 10$ flat extended skirt canopy with cutout in rear

Wb - 250 lbs

Wc = 12.17 lbs

Wp = 14.6 lbs

Canopy Material, Same as IV.

(0DS)b - 6.0 ft2

(CDS)C = 4.69 ft2 (uninflated canopy)

Z =30 suspension lines

P« = 375 lbs - Type II of Spec. MIL-C-5040

Ls = 25.5 ft

£' = 32$ at rated breaking strength

cDo= 0.70

K = 1.3

2) Pilot Parachute - USAF Drawing 60J 42'!9

Dr 40 in - 8 gore vane type

B. Performance Characteristics

Since this is a free fall system, the transient and steady state characteristics shall be considered for the following conditions:

Aircraft Release Altitude:

h h h

11,000 ft 16,000 ft 21,000 ft

18

^■"»"

Parachute Opening Altitude:

h = 9,000 ft h - 14,000 ft h = 19,000 ft

Terminal Velocity of parachutist at Altitudes defined above with (Cj)S)h ~ 6.0 ft2 (Ref 5):

VT =125 ft/sec

VT = 133.8 ft/sec

VT = 155.4 ft/sec

C. Deployment System

The parachutist free falls to a preselected altitude above ground (4,000 ft). At this altitude an automatic device, or the man, pulls the ripcord on the main parachute pack and releases the pilot chute. The pilot chute extends the main canopy, the lower portion of which is retained in a quarter bag*. The suspension lines which are stowed on top of the quarter bag, are then extended. The canopy is then released from the quarter bag and inflates (Pig 4).

D. Assumptions Used in Calculations

1) Although it is realized that this canopy in normal use may deploy and open in vertical fall, the calculations of snatch force and filling time utilize the existing equations for a horizontal or near horizontal trajectory.

2) The parachutist was assumed to be at terminal velocity when the ripcord was pulled. To make this approx- imation valid, a free fall of about 2000 feet was required (Ref 5). For this reason, the aircraft release altitude of 6000 feet above terrain was selected.

3) The quarter bag does not effect the deployment and opening chararteristics, as defined by the governing equations.

E. Governing Equations

l) The parachu'^/t's terminal velocity was calculated from the information given in Ref 5.

*Ref 1

19

Min IMIIMIII a-""^mm/mmammammmmmsm* qpp^n» wmmmammm

f *ö

1. MAN OUT OF AIRCRAFT 2. PILOT PARACHUTE DEPLOYED

AUTOMATICALLY AT PRESELECTED

ALTITUDE

3. PILOT CHUTE EXTRACTS

MAIN CANOPY

LESEND: A MAN W,TH ^ BACK PACK

CANOPY FILLED

Fig. 4 Halo Free Fall Personnel Parachute Deployment Sequenc«

20

VT altitude lost from ?xit to terminal velocity

time to reach terminal velocity"

,

where fche altitude lost between exit from the aircraft and where terminal velocity is reached âs found from a graph (Fef 5) of jump altitude versus altitude lost from exit to terminal vertical velocity. Ai?o from Ref S it was possible to determine the time it takes the jumper to reach terminal vertical velocity after he has left the aircraft.

2) The deployment time for the pilot parachute has been neglected. However, the filling time has been calculated from Eqn. 8.

3) The deployment velocity of the canopy was then calculated from Eqn 2.

4) The time for suspension line extension was calculated by the iteration process of Eqn 9-

5) The remaining calculations proceeded exactly as those shown in Section III, but utilizing the parameters characteristic of the extended skirt parachute. It should be pointed out, however, that although a snatch force was calculated it may be a considerably higher value than that experienced in actuality with a quarter bag deployment.

F.

Table IV.

Results

The results of these calculations are presented in

21

_J

pq <

O pri

PL,

AH K

• P, -~ •p P

-

p a; cj — CM CM <M (C o 1

o o

&. 1 O O O

O O o O •» * ,^—v -\ in m r° ^ -3- O p- rH ml fo 3 C1

H ac OJ ii CT II 0 || en

rH H rH

j2 C •V a i *\ •»

C • ><: «*-» c c 0 CM CD :fc 0 0 •H a> ra *—' •H «H P Kfi P

> > CU 0) CD

rH w

c

CG OJ <r rH

rH w

rH W

CU M

CO

M

rH

o O O N p, -»

• X O M) CM CD CD 60 60 c G) EH a> 23 ß •H KP w «rH •H •O 1

T3 C '—

« 0 0

M r- CO P

ü irr> CD

P CO J Q

CO

1 OJ H rH

• 8* "o 1 ti 8 O 1

<D o m j K-p *^

L "~» LT CO en o f- LTi rs

o <u I 0 « ,p co OJ OJ OJ ^fc—*

P P CM

P CM

_i

<M P. <-» • X ü O O

O CM <D <D O O o CU U-t CO O O o KP *—

0\ CM ° CT

rH rH r-l

in II 4J1 CD

co rH II • II •

XÜ

•t

"— X J2

P. *-* <D • X 0 CU CD

"O CM 0) d) ■Ö •O 3 (Up m 3 P -P K P — p P •H ■H

P *.*J

-P ^-* -P i-l "* <M CO 0 rH rH H 00

CU M CD OJ CU OJ K ' K «

^-s it LH OJ O * • #

. co\ P co rH OJ -=}•

CM rH H 1—1 ^..•' *^-^ O IT Ät Lf>

0 \ P CO

^ 1

rH H r-<

--- 1 i

22

■

!

'.

VI. T-7A CARGO PARACHUTE

As a static line deployed cargo parachute for light loads, its important parameters are:

Physical Parameters

Dr 28 ft - circular flat canopy

Wb - 500 lbs

Wc - 12.62 lbs

Wp = 15.^6 lbs

Canopy Material., nylon cloth, MIL-C-7020, Type II, 1.6 oz/yd2 Nominal Porosity = 90-176

(CDS)D - 7.125 ft2

A-21 cargo container dimensions:

Length, L = 30 in Width, ¥ = 30 in Height, H = 20 in

CDA_2i -1.14 (Ref 2)

(CDS)C - 3 ft2 (uninflated canopy)


P' = 550 lbs - Type III of Spec. MIL-C-5040

Lq ■- 22 ft, 10 in

Lj = 15.5 ft


CDo= 0.75

K = 1.4


The parachute-load system is released in such a manner that the parachute canopy is deployed first, follow^ by the suspension lines. The deployment is accomplished by a static line attached to the aircraft. Upon full extension of the suspension lines, the skirt hesitator* tie is broken

*Ref 1

and the tie between the canopy and the static line is also separated (Pig 5).


1) The deployment and opening sequence was assumed to take place in a near horizontal condition.

2) The snatch force is negligible compared to the opening force for the static line deployment.

3) Effects of the skirt hesitatcr were not considered,

D.

be used.

Governing Equations

With these assumptions, the following equations can

l) The time, t\s for static line extension is found by means of an iteration of the Eqn 1:

2\2

In =< +

,2] 2

v0*i - 37 1* (1 + JWi)J > (i)

The time, t\, is then used to determine the velocity at the instant of static line extension. V^, from Eqn 2.

2) Time, t2, for suspension line extension can be found by an iterative solution of Eq. i 9* and the related velocity Vi g - vs was calculated from Eqn 10.

3) The time, tj)t, was found from Eqn 17.

4) The filling time, tf, of the T-7A cargo parachute was determined by the method of Ref 3 and the related computer solution for tf was obtained from Eqn 18.

Fqn 4. 5) The opening force, P0, was calculated from

6) The opening time, t0, was found from Eqn 5.

7) The rate of des'cent, Ve, was determined from the equilibrium condition (Eqn 6).

8) Total down time, tip, was determined from Eqn 7.

24

1. Cargo Out of Aircraft Canopy and Suspension Lines Pulled From Pack by Static Line

•- HESITATOR

3. Suspension Lines Tight 4. Canopy Free to Open

. Canopy Alignment With Trajectory Angle

6. Canopy Filled

PiS 5. T-7/> Cargo Parachute Deployment Sequen

2b

ce

B. Results

The results of the performance calculations are presented in Table 7.

2b

J

i

&, o

co o H H M H 1 O O < <

> K K Sj <

^ W PH

p ü pg Q

< r ■■■; o

H o K a < «: O a Pi < Ü r~- Pd I 'X H w K

P-*

• p. -^ P •i^

■p -, OO in rH H a) vn ir. rH ^t- OO ^r Cf

CO tn CO O CO r- o VJO r- vo co cr 1 r-4

rH OO in 1 H CO ^J- 11 rH OJ --*

.c Ä

^ p. ^ •» p ' x c c c o V. •P 4 >

cd >

cd >

0) 8' a> rH rH rH W

B? * W W

0) V-* CU CU P ß C o

(S3 a

tSJ o

IS) p, — • x o -

60 rn CU 0) b0 bO P <U EH CO ß c

■H «-P '«-' TH Tt

p p p ^■%

d OJ OJ rH CO 5 rH OJ o N- ■3

rH CM 00 CT

EH 0) ^t- ^- ON in rH rH VO OJ CO CO OJ CT ■P to

• • • * • • 1*

CO h- VC U3 m -* ro OO cn CO CC' ts ^F -3- ^r J* it -^~ -* •=1- 0") OO oo V

• X o 4H a> (u "' O (0 K-P «-»

O «> vp vo in OJ o rH cn vo vn p^_ oo ^t tn tn ^r rH o o ^t rH o o m OJ

• • • • • • • • • • 0 1 43 in oo OJ OJ OJ -^• CO OJ OJ -3- oo OJ OJ

•p -P •p

«in P.-^

O o in

• X o <M CU CU 0) <u co K-P »--

o o in

r-i

o o o o

VO ^ * st in m f- rH CM OO ^f vo ai cn H Q it

li * s 00 <M o% r- !l

co OJ o^ N- li r- OJ tn. r- • • • * ü 9 • • • • • < 50 rH rH o o rH rH o o rH H o o

P. ^- 0) • X o CU CU

■a «in 0) CD •Ö ■Ö 3 ay Pt m 3 3 -p K-P —' ■p +J

TH

-P .p ^-v rj H o m oo a) in o ■P r- VO 00 o rH rH

• • • oo

• rH < rH

• t— in

• • < OJ • 00 • vo

• IT

* -P CO Al H rH rH ai rH H r-\ 01 rH rH H a>

ta at cu

**■"" . CU 10 cd 0)

0) m a CU \o * • it

a • OJ

• OJ

• OJ

• OJ • o • O

• O • O

• H KS) -P 0)

K <H (0 rH rH rH rH rH cn oo OO OO H in in in IT

0) cn CO no on CU m no oo oo CU 00 oo m or PS *■"* K VI

.—. m OJ m a\ m cn OJ -=t o o cn r-- o • • • • • • • • • • • i

> -P to rvi vo a> O-! ro r- H oo in o in CO cn on h- rH cn oo 00 OJ cn -3- a; 'OJ

«H HI H ai rH H o.: •H r-i OJ *~-^ co 4-»-* o O o o o o O o o o O o

o 259 VO (T\ c\i m vo tn CM ITi vo cn OJ LT fc> PS R ÊH

rH rH rH rH r-l rH

—«■ 1

:J7

VII. G-13 CARGO PARACHUTE

The cargo parachute type G-13 is a static line deployed hemispherical parachute for light loads. Its important parameters are listed below.


D0 = 32 ft - hemispherical canopy

Wb = 500 lbs

Wc = 23.89 lbs

Wp = 33.89 lbs

(CuS)b = 7.125 ft2

A-21 cargo container dimensions:

Length, L = 30 in Width; W = 30 in Height, H = 20 in

CDA-21 -1.14 (Ref 2)

(CDS)C =3.92 ft2 (uninflated canopy)

Canopy Material, cotton muslin, 4.25 oz/yd2, MIL-C-4279 Type II Nominal Porosity = 153- 253 ft3/ft2-min


P' =400 lbs - Type I of Spec. MIL-C-4232

Ls = 30 ft

Lx = 15 ft

£* = 12$ at rated breaking strength

CD0= 0.75

K = 1.3

28


The deployment system is exactly like the one described in the preceding section related to the T-7A parachute (Pig 6).


1) The deployment and opening sequence was assumed to take place In a near horizontal condition.

2) The snatch force was negligible compared to the opening force for the static line deployment.

sidered. 3) Effects of the skirt hesitator were not con-

4) The extended skirt equations were used in the filling time calculation.


1) The time, ti, for static line extension is determined from an iteration of Eqn 1. This time is then used to determine the velocity at the instant of static line extension, Vd, from Eqn 2. The time, t2- for suspension line extension can then be found by a trial and error solution of Eqix 9. Finally, the velocity of the system at the beginning of the filling process, Vs, was determined from Eqn 10,

2) The deployment time, tD-t-, was found from Eqn 17.

3) The filling time, tf, was determined by the method of Ref 3, and in view of assumption 4, the related computer solution for tf was obtained from Eqn 3.

4) The opening force, Pn, was calculated from Eqn 4.

5) The opening time, t0, was found from Eqn 5.

6) The rate of descent, Ve, was determined from the equilibrium conditions [Eqn 6).

Eqn 7. 7) The total down time, trp, was determined from

E. Results

The results of the performance calculations are presented In Table VI.

29

1« Cargo Out of Aircraft 2. Canopy and Suspension Lines Pulled From Pack by Static Line

3. Suspension Lines Tight 4. Canopy Free to Open

5. Canopy Filled

Fig. 6 G-13 Cargo Parachute Deployment Sequence

30

H >

EH

B

O C o m

c o

■H >P

> o H W

0 c o N

• ft -^ V * *

lKr°

1(8 a

P.

U 0 sjfc o ro N— Kfz.

01 I a a. c

-P

o o o

fl

H c •H

s

11s

ft -^

*n a> a> a> EH fei K -P ^

-p

ft

-p

o o IT»

vo

0

-p

O Sn CD CD a» o ro « -P w

8 «

o -p

ft ^ • X o

Vi <D —

EH w

in H

cvl

0 rH

PC

-P P

■P

vo M-

c

I rH H

rH

& "I CJ CM

J) ■Pd)

. ro \ CD > -P ra

a

a ro

o ooo Cb ^ UP I

o *

cd ft

Q O

o f ro) H

^

31

c o

■H -P Rj t> 0) H W

0) c o N

faO c

■H ■d B

5

cc •01 a c\i| roi

P

vo CM

O try

CO CN

00

■P

O o If»

H

I OJ

vo on

-p

O o LPi

cc

x:

c o ■H -P cd >

rH W

CD C o

C-J

C

ON

8i M coj nil ^

in OJ

m

c

$

o m

m

OJ rH

CM

mi in|

~H Oi

CO -=1-

0J •St

l>- o

■=t

n a) a>

rH

PC

vo. H

OJ

O

o

o cm

OJ

H OJI CU

o

ON oN

&

o mi

ml

o CVI OJ

-p

O O o

o OJ

0) ■Ö "3

-P •H -P rH <

a)

cd 0)

r-l 'jj K

on o

in on

CO o>

OJ

ovl OJ

vo o

vo CO

rH 0O| CT)

cri

a, on

M

rn on

cvi ao

o

vo CVJ O)

O cvi

-J \ L °

VIII. G-12D CARGO PARACHUTE (PLATFORM LOAD)

When the G-12D cargo parachute is used in connection with cargo platforms, its principal parameters are as follows:


D0 - 64 ft - circular flat canopy

Wb = 2,200 lbs

Wc = 76.79 lbs

Wp = 109.5 lbs (inc. wt. of risers - 4.75 lbs)

(CpSJb =76.8 ft2

Platform dimensions: L = 8 ft, W = 3 ft

^platform -1'2 <Ref 2>

(Cjß)c = 7.146 ft2 (deployment bag)

Bag dimensions:

Length, L - 40 In Width, W = 24.5 in Height, V. = 15 In

CDbag - 1.05 (Ref 2)

Canopy Material, nylon, 2.25 oz/yd2, MIL-C-7350 Type I Nominal Porosity = 90-165 ft3/ft2-min


P; = 1,000 lbs - Type 17 of Spec. MIL-C-7515

Ls = 51 ft


LR = 5 ft, 5 in - Type X, Class R - MIL-W-27265

£'riser = 2®^ at âted breaking strength

CD0= 0.75

K = 1.4

32


The G-12D parachute with a platform load is extracted from the aircraft by a standard 15 ft extraction parachute, reefed with a 260 in. reefing line. (See Section XI) As the cargo platform leaves the aircraft ramp the extraction force is transferred from the platform to the deployment bag of the main canopy, thus initiating a suspension lines first deployment sequence (Pig 7).


1) The initial velocity, V0, is assumed tc be the velocity of the platform as it leaves the aircraft, and not the aircraft velocity. This is a necessary assumption since the platform velocity relative to the aircraft varies considerably with operating conditions.

2) ^fhe release time, t = 0, is assumed to be when the platform leaves the aircraft ramp. The elapsed time for the extraction parachute opening sequence has been calculated in Section XI and can be included as an additive term prior to cargo exit from the aircraft. In addition to this, the time necessary for the cargo to traverse the distance inside the aircraft, under the influence of the extraction parachute drag, must be considered.

3) The deployment and opening sequence was assumed to take place in a near horizontal parachute attitude.


l) The suspension line extension time, t2, was determined fron» Eqn 9 and since there is no static line, t-L = 0. Therefore:

-Dt = t,

The drag area—mass ratio terms of Eqn 9 are:

J^ - based on platform characteristics

Jc - the sum of the G-12D deployment bag and extraction parachute characteristics

2) The velocities of the platform and parachute required for snatch force calculations were determined from Eqns 10 through 13.

3) The snatch force was calculated from Eqns 14, 15, and 16.

.33

1. Extraction Parachute Force Transferred to Bridle of G-12D Parachute Assembly

EXTRACTION CHUTE

DEPLOYMENT "BAG

SUSPENSION LINES

CARGO

2. Suspension Line Deployment

MAIN CANOPY

Line-Stretch: Canopy is Extracted from Deployment Bag

4. Canopy Begins to Pill

5. Canopy Pilled

Pig 7. G-12D Cargo Parachute Deployment Sequence - Plat' form Load

34

- , ■ —

4) The filling time, tf., was determined by the method of Ref 3 and a computer solution for tf was obtained from Eqn 18.

5) The opening force was found from Eqn 4.

6) The rate of descent, Ve, was determined from the equilibrium condition (Eqn 6).

7) The total down time, try, has been calculated from Eqn 7, but it should be viewed with some doubt since the altitude loss during opening may be significant.

E. Results

The results of the performance calculations are presented in Table VII.

35

S 9 o

CO 1-3 Ü H £ EH K CO O H & « EH

n a O Pi

H < H K 1 > <

E

CH

HU

TE

< O O H S ■=*

gj § § Pn o PH O K O W K Pi <

O

HU

TE

12D

O 1

§ ° < Pi

. p, ,-. «H X % ■a P

p a> a> ^ r <f> in V£ CO H co >* •* N rH rf> o Ch o * •> 1 • » i «t •« * T •

ll <N U3 i~i r-

r-1

o \o H r* 11

rH

rs vo o vc i-i M rH i-H rH rH

Ä

•s ft •» *» ß • x «r* c c 0 <M OJ *fc: o o *H OJ 00 v-' ■H ■H P Kfc P P cd > OJ

> aj > OJ

OJ o ro oo --H- o in H CO CO CO o H ^J c*- CM rH rH C^ CM ^j- ■=t rH O^. s- VO^ u\ w 03 -■—• Ü Ü H CM w o> 00 co CO H vo m r-t a

PC Ifc • •4 •t •> • « •k •% •i •V • -j

0) CO OJ VO o QJ t-- rH m a\ 03 t-- H in c/ c rH rH CM c rH ■H H d H rH rH

o o a. *-»

• X u M <H m D M bO ß a) EH OJ ß ß •H PSP -— H TH

«3 C

3 C

•o ß

o EH OJ

CM t>- ro UP. 00 C7\ m O oo VO 00 H m • CTi • in • • 00 • VD * • •

■P IS -=t" CM rH o o CO t- K ■3" CM rH H IT in in in m ■si- ^t ^1" ^J" ^t ^t ^J-

• £~ <M a> 0 a) o en «p -—

<-^ u

o <s> ,p 03

00 oo OA H r~- 00 ^t- 0\ ^ o CM LO H CO CO -3- ^D t- 00 oo in h- r- O^l • • • * • • • * • • ft

•p

X"' IT en CM CM p <M

■m CT) OJ CM p IM

m 00 CM CM

<M ft ^-.

O <M 0J d) O o

O O

O in

0J CH 03 «P ^

in

rH

O

o ; vo ** "~ r*" f- CM in rH r- 00 ^t rH CM CO ^)- 00 oo

!l 1- m vo o CO o\ II *t CT\ CM ON II

CM CO o CO P £ 4 • • m • • • • c *

£

•»

03 ^t CO CM H *t CM CM rH ST,

^* CM CM rH

ft *-« OJ • X o V 0)

■O <M aj a; • 1 -o 3 (DP 03 ;\ 3 P

p

C£P *-- 4- P

,-» P P H

(5 a) IT VO r~ VO H O O O CO rH Oi VO ^r CM < H C- m .=t «C Of a) vo CM a) vc m P 03 • • » ♦ • • • « « • «

0) in a)

1— H ID 03 a]

H 0) 03 «3

r-i

sTo cr rr\ o\ CT^ ^" =t =t ^t- ^t äT ■=t if o • • • • a> • m * • (D 9 • 9 • rH

►^ <H 03 o o n O rH on 00 oo ro !-1 00 00 00 CO

0) or oo on m a> 00 m or,> oo OJ m o-, 0" oo K '— K K

-^. o<~ VO CO CO in CM CO in rH N- rr vo . o • • • • • « • • • • • •

. 03\0 o in o in H r^- CM a) oo 0\ VO CM > P 03 (T ro CT; CM o> m CO CM C\ en CO OO

<i-i H H OJ rH H CM rH H CM %«•* |n 03

"S^ O O o o o o O o o o O O 0 2 03 vo o^ CM in vo o\ CVJ in VO o> CM in

> Jgg rH rH rH H rH rH

SM __

36

IX. G-12D CARGO PARACHUTE (A-22 Container)

The G-12D argo parachute is also used In connection with the A-22 cargo container. Is this combination the performanc characteristics of the parachute are slightly different from those observed with the platform, as presented in the preceding section. The typical parameters are:


l) Main Canopy

D0 - 64 ft - circular flat canopy

Wb = 2,200 lbs

Wc = 76.79 lbs

Wp = 109.5 lbs (including risers)

Canopy Material, nylon cloth, MIL-C-7850, Type I, 2,25 oz/yd2 Nominal Porosity = 90~:65 ft3/ft2-min

(CDS)b = 16.31 ft2

A-22 container dimensions:

Length, L = 52 in Width, W = 43 in Height, K = 50 in

CDA_22 =1-05 (Ref 6)

(CDS)C - 7.146 ft2 (deployment bag)

Bag dimensions:

Length, L = 40 in Width, ¥ = 24.5 in Height, H = 15 in


P1 - 1,000 lbs - Type IV of Spec. MIL-C-7515

Lq - 51 ft

L± = 15 ft

37

—

B.

c' = 20$ at rated breaking strength

LR = 5 ft, 5 in - Type X, Class R ~ MIL-W-27265

£'riser = 2^ at rated breaking strength

CDo = °-75

K = 1.4

2) Pilot Parachute - Drawing No. 53E 6803

D0 - 5.66 ft - octagonal canopy

Z = 8

Lg - 5.5 ft - MIL-C-7515 Type II

Lx - 15 ft

LR = 9.25 ft

CD0= 0.75

Deployment System

After the parachute-load assembly is released from the aircraft, the pilot chute is deployed from its pack by a static line. The pi"1 )t parachute extracts first the suspension lines of the main parachute from its deployment bag and then the main canopy. The deployment bag is then separated and the canopy is free to 'inflate (Pig 8).


l) The calculations are limited to ehe cases of near horizontal deployment.

neglected. 2) The pilot parachute fi'.lling time has been

D. Governing Eq\T*tlons

l) The cargo is assumed to free fall, acted upon only by its own weight and drag while the static line and pilot parachute are deployed. The time for this occurrence is obtained from a modified form of Eqn 1 of the Appendix, where the length L^ is the sum of the static line length (15 ft), the pilot chute suspension line length (5.5 ft), and the pilot parachute riser length (9.25 ft). The Jc term is

38

STATIC LINE

PILOT CHUTE >V»-PACK

PILOT CHUTE

DEPLOYMENT BAG

• CARGO

1. Pilot Chute Deployed 2. Suspension Lines Out

3. Main Canopy Out Canopy Opens and Separates* Prom Deployment Bag

Pig 8, G-12D Cargo Parachute Deployment Sequence - A-22 Cargo Container

39

the sura of the (1-12D deployment bag and the pilot parachute characteristics.

2) The deployment velocity of the main canopy is determined from Eqn 2, using the time calculated in i) above, and neglects the small velocity change and time increment during the filling time of the pilot chute.

3) The snatch velocities, snatch force, main canopy filling time, opening force, and equilibrium characteristics are then calculated by the standard methods outlined earlier.

E. Results

The results of these calculations are presented in Table VIII.

40

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41

X. G-11A CARGO t-ARACHÜTE

The G-11A cargo parachute Is normally used in conjunction with a load platfom. The significant parameters of this parachute operation are listed below.


D0 = 100 ft - circular flat canopy

Wb = 3500 lbs

Wc = 133.7 lbs

Wp = 193 lbs (inc. wt. of risers - 38.64 lbs

(CbS)b = 76.8 ft2

Platform dimensions:

Length, L = 8 ft Width, W = 8 ft

C-n , .„ =1.20 (Re* 2) ^platform v '

(C-QS)C = 12.25 ft2 (deployment bag)

Bag dimensions:

Length, L = 48 in Width, W = 35 in Height, H = 12 in

Canopy Material, nylon, 1.6 oz/yd2 - MIL-C-7020 Type II Nominal Porosity = 70-176


P» =550 lbs - Type III of Spec. MIL-C-5040

Ls = 35 ft

Lp = 20.5 ft

LR = 60 ft webbing - Type XVIII of Spec. MIL-V. -27265 Class R

£' -- 35$ at rated breaking strength

£'riser = 21^ at rated breaking strength

42

B.

GDo= 0.73

K = 1.4

Deployment System

The platform load Is extracted from the aircraft using a standard 15 ft diameter extraction parachute with a 260 in. reefing line. As the load exits the aircraft the extraction parachute force is transferred to the bridle of the G-11A assembly. The main canopy deployment bag is separated from the load, paying out the risers and suspension lines in a lines first deployment. When the canopy skirt leaves the bag, two reefing cutters are armed. The remainder of the canopy is extracted from the deployment bag breaking the tie that connects the apex of the canopy to the deployment bag. After a period of two seconds from cutter arming, the reefing line is severed in two places and the canopy continues its inflation process (Pig 9)•


1) The initial velocity, V0, is that of the cargo platform, and not necessarily the aircraft speed.

2) The release time, t = 0, is assumed to be when the platform leaves the aircraft rarnp. The elapsed time for the extraction parachute opening sequence has been calculated in Section XI and can be included as an additive term prior to cargo exit from the aircraft. In addition to this, the time necessary for the cargo to traverse the distance inside the aircraft, under the influence of the extraction parachute drag, must be considered.

3) The deployment and opening sequence takes place in a near horizontal condition.

4) The filling procedure, for the period where the inlet of a reefed canopy grows from the reefed diameter to.fully open, is identical to that of an unreefed parachute over the same filling period.


1) The extraction time, until tho platform crosses the aircraft ramp is given in Section XI. For this calculation, t = 0 occurs when the platform leaves the aircraft.

2) The suspension line extension time, t<^, is given by Eqn 9, where the term Ls includes the riser line

43

1. Deployment Initiated DEPLOYMENT BAG

2. Line Stretch

*/— BREAK TIE SEPARATES

REEFING LINE

3. Main Canopy Reefed

SEVERED REEFING LINE

4, Canopy Disreefed

5. Canopy Pilled

Pig 9. G-11A Parachute Deployment Sequence

44

length and the term Jc contains drag area and mass terms of both the deployment bag and the extraction parachute In its fully inflated condition.

«voc + ''c ' (CDoSojext 2(mc + mext)

3) The velocity terms necessary for the snatch force calculations are determined from Eqns 10 through 13, assuming the deployment velocity term, V^, equal to the initial platform velocity, Y0, at exit from the aircraft.

4) The snatch force was then calculated from Eqni 14, 15, and 16.

5) The total filling time of the Ö-11A parachute system was determined by the following method.

First, the filling time of the unreefed G-11A canopy was obtained from the method ol Ref 3, and a computer solution of Eqn 18. Then, the time elapsed while the inlet area increases from the reefed area (S^ = rtDr2/4) to fully open was determined by using an experimentally determined curve of instantaneous inlet area versus time for the unreefed canopy (Pig 10).

Assuming that the reefed and unreefed canopies have identical filling procedures during this period, the calculated value represents that portion of the filling time from disreef to fully open. Adding the two second reefing time yields the value for the total filling time. This method, then, assumes that the reefing cutters are armed at about the time of snatch force occurrence.

Eqn 4. 6) The opening force, F0, was calculated from

7) The rate of descent, Ve, was determined from the equilibrium condition (Eqn 6).

8) The total down time, t>p, has been calculated from Eqn 7, assuming equilibrium conditions exist during a fall of 1500 ft. However, the altitude loss during opening may be significant and the total time must be viewed with caution.

E. Results

The results of the performance calculations are presented in Table IX.

45

(•«MCMOaMH»^

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

i

J

/

/

/

/

r

^-"

-. -

0 Q2 04 0.6 OB 1.0 T

Fig 10. Ratio of Inlet Area to the Total Area as a Function of the Dimensionless Time, T

46

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43

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47

XI. EXTRACTION PARACHUTES

Extraction parachutes are used to extract load platforms out of the cargo compartment of the aircraft. As a characteristic feature, it can be assumed that these parachutes are so small and inflate so rapidly that the velocity of the relatively heavy load does not vary during the period of parachute inflation. This condition is usually character- ized as infinite mass condition.

Extraction parachutes of 15 ft, 22 ft, and 28 ft, nominal diameters, are under consideration. The 15 ft canopy is used both reefed and unreefed and the calculations have been performed for both cases.


l) 15 ft Ringslot parachute - unreefed

W . ■ 6.06 lbs Wp - 8.06 lbs

Canopy Material, nylon cloth MIL-C-7350 Type I, 2.25 oz/yd2 Nominal Porosity = 90-165 ft3/ft2_rain

(CDS)C = 1.425 (deployment bag)

Bag dimensions:

Length, L = 18 in Width, W = 10 in Height, H = 3.5 in

On. = 1.14 (Ref 2) ^bag x '


P' = 1,000 lbs - Type IV of Spec. MIL-C-7515

Ls = 15 ft

LgX= 60 ft


£" = 28$ at rated breaking strength of 12,000 lbs

^total = 17$

CD0= 0.55

xK = 1.05 (infinite mass) (Ref l)

48

~——■"■

2) 15 ft RJngslot parachute - reefed

Unless note . here, the parameters are those noted in l) above.

Effective diameter, D0 «_ = 12.0 ft

Lr = 260 in

3) 22 ft Rlngslot parachute

Wc = 19.3 lbs Wp = 27.5 lbs

Canopy Material, nylon cloth, MIL-O-7350, Type I, 2.25 oz/yd2 Nominal Por'osity = 90-1G5 ft3/ft2-min

(QDS)C - 1.425 (deployment bag)

Bag dimensions:

Length, L = 18 in Width, W ■ 10 in Height, H = 3.5 in

CDbag = ia4 (Ref 2)


P' = 1500 lbs - Type V of Spec. MIL-C-7515

Ls = 22 ft

LeX= 60 ft - 6 ply

c1 = 25$ at rated breaking strength

£M = 28$ at rated, breaking strength of 40,000 lbs

Adapter Web length = 5 ft, 6 ply

Atotal = 17$

CD0= o.c-:

xK - 1.05 (Ref l)

4) 28 ft Ringslot parachute

Wc = 22.55 lbs Wp = 36.55 lbs

Canopy Material, nylon cloth, MIL-C-7350, Type I 2.25 oz/yd2 Nominal Porosity - 9O-I65 ft3/ft2-min

49

B.

Bag c'imensions:

Length, L = 23 in Width, W = 14 in Height, F = 10 in

%ag - LI* (Ref 2)


P' = 2,000 lbs - Type VI of Spec. MIL-C-7515

Ls = 28 it

Lex= 60 ft - 8 ply

£ = 30$ at rated breaking strength

£" = 28# at rated breaking strength of 52,000 lbs

Adapter Web length - 9.0 ft, 8 ply

Atotal = 17#

CDo= °-55

xK = 1.05 (Ref 1)

Deployment System

The extraction parachute assembly is supported in the rear of the cargo section on a bomb shack]e. Upon T ease the' deployment bag swings aft and is subjected to the air- stream behind the aircraft. The aerodynamic drag on the deployment bag extends the 60 ft extraction line to its full length at which time the canopy deploys, lines first, and inflates.

The payload in the aircraft is released at a predetermined extraction force and moves aft through the cargo compartment. As it passes over the exit ramp of the aircraft a mechanism transfers the extraction force from the cargo to the bridle of the main recovery canopy, and after this time, the extraction parachute functions much like a pilot parachute (Pig li).

C Assumptions Used in Calculations

l) The deployment and opening sequence occurs in a near horizontal condition.

50

■JJTWW*!!'"«'" mwuWIliN i IUJRIM

LULLUIII ii / / LUSLLH Tzar BOMBS HACKLE MAIN RECOVERY PARACHUTE!

I CARGO

"frrrrn

¥

l.

^r'rö^y7TT^rr77T77^

Aircraft Ca^go Compartment

EXTRACTION PARACHUTE

EXTRACTION LINE

•AIRCRAFT RAMP

2. Bomb Shackle Releases Deployment Bag

-^±±±LLLlJMlLni±LLL

3. Load Moves Through Cargo Compartment

// / IK 11 m I ,n f ([(I

T7TTrrm7fnTfr^~~u** TRANSFER

4. Load Exits Aircraft and Extraction Force Initiates Deployment of Main Canopy

Pig 11. Extraction Parachute Deployment Seq uence

51

2) The filling times and opening forces are calculated on the basis of infinite mass relationships.


l) The time for extraction line extension Is determined from Eqn 1 where:

Ll - Lext = 6o ft

2} The deployment bag velocity at extraction line extension is given by

V.

•n,i " jcvotl + r

3) The time for suspension line extension, tg, is given in Eqn 9, where Ls includes the length of the adaptor web.

4) The velocity of the canopy at time t2 is given by Eqn 11.

5) With this information, and realizing that the aircraft flies at a constant speed V0, which in this case is VT,2> the snatch force can be calculated from Eqns 14, 15 and

6) The filling time for the infinite mass case is given by the equation

8 D o P 7* To

(Ref 4)

7) The opening force is calculated from Eqn 4 utilizing a constant infinite mass xK factor of 1.05.

8) The steady state rate of descent and velocity are not calculated for the extraction parachutes, since their functioning is essentially completed with the deployment of the main recovery parachute.

E. Results

The results of the performance calculations for the 15 ft, 22 ft, and 28 ft extraction parachutes are presented in Tables X through XIII.

52

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XII. CONCLUSION

An attempt has been made to calculate the transient and steady state performance characteristics of a number of conventionally used man-carrying, cargo, and extraction parachutes. In view of the n^^rous assumptions, the pre- dictions should be consideraa as approximations, based on currently available solutions.

It is recommended that this report be reviewed and r./ised as better analytical methods and experimental data become available.

57

!

XII. REFERENCES

1. Performance of and Design Criteria for Deployable Aerodynamic Decelerators, Ä3T>-TR-6l-579, December, 1963.

2. S. P. Hoerner: Fluid-Dynamic Drag. Published by tue Author, 1958.

3. Rudi J. Berndt: Experimental Determination of Parameters for the Calculation of Parachute Filling Times, AFFDL, USAF, Annual Meeting WGLR-DGRR, Berlin, September, 1965.

4. United States Air Force Parachute Handbook, WADC- TR-55-265 (ASTIA Doc. No. AD 1±00367, December, 1956.

5. Ralph H. Puddycomb: Human Free-Fall Trajectories, FTC-TDR-64-10, June, 1964.

6. H. G. Heinrich and S. K. Ibrahim: Determination of the Minimum Sized Parachute Required for Stabilization of the A-22 Cargo Container, ASD- TR-61-326, July, 1961.

7. H. G. Heinrich: Chapter III - The Physical Process of Parachute Inflation, Presented at the Summer Course on Aerodynamic Deceleration at the University of Minnesota, July, 1965.

8. U. S. Standard Atmosphere, 1962

58

--—

APPENDIX

GOVERNING EQUATIONS

This section presents the general equations used for the preceding calculations. In many cases in the main text these equations have been altered slightly for adapta- bility to a specific system. The altered equation number in the text is then shown with a lower case "a .

The equations shewn in this Appendix are numbered as they appear in the main text, where an attempt has been made to maintain chronological order. However, since several systems have been considered, some deviations necessarily exist.

The governing equations for the extraction parachutes have been set down in Section XI, and since these canopies have identical deployment and filling characteristics, they have not been repeated in this Appendix.

1. Static line extension time, t]_. (Ref l)

This time was found by an iteration of the equation

where

Li 4TT7 + [Vi - -q ln ^ + Jiî)]2)

Li - length of static line

Jl - pfCnS^/anb+c

rab+c ~ mE3S °f suspended load plus complete parachute system

The velocity at this Instant is given by:

Vo vd " VI,1 - j^tj + 1

2. Pilot parachute filling time. (Ref 7)

(1)

(2)

If a pilot parachute is employed, it may be deployed by a spring action or static line. In either case, the filling time may be calculated using:

2D,

tfn = 3irVo(9/70 - C/3)

59

(8)

'"um w ■ -"«

■ »4.

The opening force of the pilot parachute is very- small compare! to the main canopy force, and has not been calculated.

3. The suspension line extension time, to. (Ref l)

The time for suspension line extension is found from an iteration of the equation

L3 = j- in(i + jbvdt2) - 1 m(1 + Jcvdt2) (9) where

and

/ Jb = P(CDS)b/2mb

J0 - p(CDS.)c/2mc

4. The time, tot.» Is '°he time from release to the instant which the deployment begins, tj_, plus the time for suspension line extention, t2. Therefore, one may write

^Dt = *i + ^2 *

If a pilot parachute is an integral part of the system, its pertinent times must be included in Eqn 17.

5. Component velocities. (Ref l)

The velocities of the primary and secondary bodies, load and parachute, respectively, can be determined from:

(17)

and

V

1,2 JbVdt2TT

11,2 == JcVd + 1

VII,2(rel) : VI,2 " VII,2

V 1,3 VII,3=VI,2=Vs

(10)

(11)

(12)

(13)

6. Snatch force calculations. (Ref l)

The snatch force was calculated by the method of Ref 1, from which

60

i/mumusmmiiiimmm*m ipmn in iiaiiiaiiu

where

P ■ P + P 3 c (14)

2 2 V + V p « £ V «^ II»2 11,3 Fc ■ 2 vcDS'c ' 2 (15)

and

P = J"ofe,2(rel)1zr'

£ (16)

The various velocity parameters in the equations above were found in the preceding section.

7. Main canopy filling time, tf. (Ref 3)

For canopies opening under finite mass conditions the filling time was determined from computer solutions of the following equations:

a) 10$ flat extended skirt canopies.

'=0.25 5.271T^ + 2.597T + 0,2587

M " Ptf [S/M ~ M _ TN . PTT dT (3)

RV^ + 2 LN(N

ln R Tj + TH

where

M = sum of system and included air mass

W\ = ~ + pD 3(0.009l69T + 0.00006'!75)

W. = sum of parachute and suspended load weights

N = rate of change of included air mass with respect to dimensionless time, T = 0.009l69pDQ3

P = sum of initial drag areas of vehicle and canopy .= 0.00647 (CnS)max + (CDs)b where (Cj)S )max ~ maximum canopy drag area and (cDS)b = drag area of suspended load.

R = sum of initial masses of system and the included air = W

* + 0.00006478pD3

61

S = rate of change of canopy drag area with respect to dimensionless time, T = 0.1445 (CuS)max

b) Circular flat canopies.

rT=0.3

D_ = t M LRVS

1.87^T2 + 2.96T + O.OS66 "

+~ZL Jl (*L in M T\ + Il\ dT (18) 2 \N M¥ R ' F /.

where W -

M = — + pD 3 (0.020624T + 0.0000264)

N - O.020624pDQ3

F - 0.003733 (CDS)max + (CDS)b

Wt 3 R = _i + 0.000264pD J o O

s = 0.12237 (cDs)max

8. The opening time is, by definition of Ref 1, the tifue from the release to the time the canopy is fully inflated.

tQ = tDt + tf (5)

9. The maximum opening force for all the parachutes was calculated by the method of Ref 4 with

where

Fo - CDoS0qsxK (4)

a) Cj) S0 is the drag area of the fully inflated canopy

b) qs = ^pVs2

c) K is a dimensionless factor

d) x denoted the relationship between actual opening shock P0 and the constant force Fc, x = F0/Pc

10. The rate of descent, or the equilibrium velocity, for the parachutes was determined from force equilibrium expressed as

62

—-*m»

V TU total J^Doâvo^

(6)

where w"tot _J. is the surn of parachute weight and suspended load weigb'1, and pave Is the average density between parachute opening altitude and landing zone elevation.

11. The total down time, trp, was determined from

1500 tm = tg + vc (7)

where the release altitude is 1500 ft above ground.

63

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DOCUMENT COHTROL DATA • R&D (Sacuritr claaattlcafion at titlm. body ot mbmttwct and indauing annotation mumt ba mntirmd mttmn ütm ovmtatt import im mimmaUtmd)

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University of Minnesota Kinneapolis, lärm. 551*55

V.*. SCfSBl SECURITY C LAMIPICATION

Unclassified 2 6 CROUP

n/a 3 REPORT TITLE

Calculated Values of Tranr' ..nt and Steady State Performance Characteristics of Man-Carrying, Cargo, and Extraction p-rachutes

4. DESCRIPTIVE NOTES (Typ» ol «port and Inclusive tßataa)

Final Report April 6$ - April 66 S. AUTHORfSJ (Laat initial)

Haak, Eugene L. Hovland, Richard V.

6. REPORT DATE

November 1966 3«. CONTRACT OR «RANT NO. AF33 ( 615 )~255U

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13. ABSTRACT

Opening shock, snatch forces, opening times, rates of descent, and down times of a number of man-carrying, cargo, and extraction parachutes are calculated on the basis of analytical equations and certain other assumptions. Comparison of the calculated data with full scale experimental values are somewhat limited, but show reasonable agreement when available. This report represents a first step in an attempt to catalog full scale experimental values from which, eventually, more exact analytical methods can be derived»

DD ,Ä 1473 Unclassified Security Classification

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Parachutes May-carrying parachutes Cargo parachutes Extraction parachutes Dynamics of opening ?tate of descent Analytical methods

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UNCLASSIFIED AD NUMBER LIMITATION CHANGESOpening; shocks, snatch forces, opening times, rates of descent, and. down times of a number of man-carrying, cargo, and extraetior parachutes