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The Durachute Vacuum Sealed Rescue Parachute

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									   The Durachute Vacuum Sealed Rescue Parachute

                                 Dipl.-Ing. Heiko Froehlich
                                       Project Manager
                                       Autoflug GmbH
                                     Industriestrasse 10
                                     D-25462 Rellingen
                                          Germany


ABSTRACT                                          qualified and introduced to the US Navy
The paper describes a new technology for          for the use in the P-3 aircraft and the US
parachute vacuum packing and sealing by           Air Force is planning to replace their bail-
the example of the Durachute aircrew              out parachutes with the Thinpack. Dura-
emergency bailout parachute, that will be         chute is the name for the civil application
in service for the German Aircraft C-160          of the Thinpack.
Transall and BR-1150 Breguet Atlantic.
                                                  The German Forces are just about to re-
The Durachute is the civil name of the            place their BA-22 parachute, that is used
Thinpack parachute that has been intro-           in the C-160 Transall and the BR-1150
duced to the US Navy.                             Breguet Atlantic aircraft with a modified
                                                  Durachute system, additionally equipped
The Durachute canopy and the suspen-              with a canopy release and a Cypres Auto-
sion lines are vacuum packed and envi-            matic Activation Device. Autoflug GmbH,
ronmentally sealed to protect it from the         located in Rellingen/Germany, is the
elements and extend its life. The patented        SIMULA representative for Europe and is
sealing technology provides a long repack         responsible for the German military qualifi-
cycle of more than 5 years and a canopy           cation, as well as for the service and main-
shelf life of 27 years, which significantly       tenance of all Durachute systems in
reduces maintenance time and cost. Due            Europe.
to the vacuum packing the parachute as-
sembly achieved a low weight and small            This paper describes the parachute design
volume and is especially suitable for a           goals, the design concept, the qualification
seat integrated application.                      in the USA and Germany and the concept
                                                  of the seat integrated parachute.
INTRODUCTION
The development of the Thinpack para-             PARACHUTE DESIGN GOALS
chute was initiated under a research con-         The goals of the US Navy research pro-
tract of the US Navy in the early 90s.            gramme have been:
SIMULA International, located in Phoe-            - Reducing the repack expenditure with
nix/USA, awarded the contract for the de-            the help of a vacuum packed canopy
velopment of a newly designed emergency              and an extension of the repack cycle to
bailout parachute system to replace the              more than five years. Regarding the
NB-8 parachute of the US Navy. The main              high number of parachutes in the US
goals for the parachute design have been             Navy (17.000 emergency bailout para-
a repack cycle of more than five years, an           chutes) and a repack cycle of 660
environmentally sealed canopy, a one-                days, the repack cycle extension to
size-fits-it-all harness and a reduced               more than five years significantly re-
weight compared to the used parachutes.              duces the maintenance time and costs.
                                                  - Providing an improved harness that fits
SIMULA has developed a system which                  to all crewmembers from 3 to 97%ile
meets the required objectives and more-           - A light weight parachute system of less
over makes substantial improvements in               than 17 pounds (7,7 kg). The NB-8 has
other areas such as quickness to don,                a weight of 25 pounds.
comfort and canopy performance. The               - A parachute canopy with a descent
Thinpack parachute system has been                   rate of less than 24 ft/sec (7,3 m/sec)


                                          Page 1 of 4
    with a 265 lb suspended mass and a              The sealed canopy is attached to short
    maximum opening velocity of 150 kt.             risers on the harness by means of proprie-
-   The initiation of the parachute deploy-         tary hardware specifically developed for
    ment shall not require any additional           this system. This hardware permits the
                                                    sealed canopy to be treated as a replace-
    action beyond pulling the ripcord.
                                                    able module of the system. The flexible
                                                    envelope and modular design permit an
PARACHUTE DESIGN CONCEPT                            alternate canopy to be substituted into the
The canopy is packed in a deployment                existing system. The system is suitable for
bag and this bag, together with the sus-            either round or ram air canopies.
pension lines and parts of the two risers, is
vacuum-sealed into a flexible, low-                 The pilotchute is packed inside the con-
permeability envelope. Vacuum-sealing               tainer, but outside the sealed envelope. It
eliminates problems caused by variations            provides the force necessary to tear open
in the external air pressure, and, within the       the sealed envelope and extract the can-
envelope, lowers the concentration of re-           opy. The pilotchute is attached to the de-
actants deleterious to nylon. Vacuum-               ployment bag through a bridle consisting
sealing also allows the system volume to            of four separate lines. Each of these four
be reduced, as is apparent in picture 1.            lines passes through the sealed envelope
                                                    near a tear initiator and is attached to a
                                                    bridle line inside the envelope. These four
                                                    cords converge to a single cord for extract-
                                                    ing the deployment bag. The four separate
                                                    tear initiators ensure that regardless of the
                                                    orientation of the jumper, there will be an
                                                    efficient load path between the pilotchute
                                                    and at least one tear initiator. The system
                                                    is designed such that the force developed
                                                    by the pilotchute at a bailout speed of 90
                                                    knots is at least four times the peak
                                                    extraction force. Picture 2 shows the entire
                                                    system stretched out just prior to para-
                                                    chute inflation.



               Picture 1:
      The Thinpack parachute (left)
    compared to the Navy NB-8 (right)




                             Picture 2: Sealed Parachute System



                                            Page 2 of 4
The harness and the container are an in-          a cycle of 6 months, what even increases
tegral assembly. This design simplifies the       the potential costs savings from using
donning and reduces weight. The length            sealed parachutes compared to the US
adjustment in the harness occurs entirely         Navy.
on the front and is in the main lift web of
the harness. The harness design is a solid
saddle configuration. The total weight of         In addition to an extended repack cycle of
the sealed parachute system is 7.7 kg             5.5 years, the sealed parachute will have a
                                                  recommended service life of 27.5 years,
                                                  approximately twice the service life of the
REPACK CYCLE                                      existing units.
The system has a recommended repack
cycle of 5.5 years. The combination of a          DEPLOYMENT RELIABILITY
low-permeability envelope and vacuum              Both, static and dynamic tests were per-
packing ensures that degradation of the           formed to demonstrate the deployment
nylon canopy fabric is virtually stopped.         reliability and have shown that the sealed
                                                  parachute can be expected to deliver
To demonstrate that the recommended               highly reliable and consistent openings.
5.5-year repack cycle is justified, a model
was created to calculate the amount of
water vapor and oxygen permeating                 QUALIFICATION
through the envelope material. The model          The Thinpack has been mutually qualified
was run using external conditions of 90           by SIMULA and the US Navy. The para-
percent relative humidity and 23 °C. After        chute system has first been tested accord-
5.5 years, the partial pressure of oxygen         ing to the FAA TSO C23d requirements
within the envelope is only 25 percent of         and the test procedures spelled out in SAE
its normal atmospheric pressure, and the          AS8015B. Those tests were comple-
relative humidity inside the envelope has         mented by tests according to some special
risen to only 23 percent from a starting          military requirements. Both FAA and US
value of 15 percent. The total pressure           Navy      have    certified   the     Dura-
within the envelope is only 0.27 atmos-           chute/Thinpack parachute system.
pheres after 5.5 years.

In addition to the modeling, three systems        GERMAN MILITARY QUALIFICATION
were subjected to a series of environ-            The German military qualification is pres-
mental stresses including shock tests, vi-        ently in progress, prepared by Autoflug. It
bration, rain, high temperature/humidity,         is planned to simplify the qualification pro-
acceleration, temperature/humidity shock,         cess by taking the existing FAA and US
sand and dust, pressure/altitude cycling,         Navy qualification and compare it to the
depressurization, and salt fog. These sys-        requirements of the German military para-
tems passed all of the exposures except           chute qualification. Only those points that
the package drop portion of the shock test.       are not covered by the FAA or the US
One system developed a vacuum leak                Navy certificate have to be approved in a
following the eighteenth drop. The failed         delta qualification.
system was subsequently used in an ex-
traction test and performed perfectly. Even       One critical issue was the flammability of
a complete loss of vacuum from the                the parachute system, since German regu-
sealed envelope does not interfere with           lations require for parachute container and
successful deployment.                            harness       the     same      flammability
                                                  characteristics as for personal crew
The US Navy currently operates on a re-           equipment. Such equipment has to
pack cycle of 660 days and thus the num-          withstand a flame temperature of 900°C
ber of repacks required on each system            over 15 sec. No other parachute
will be reduced to one-third of the current       qualification regulation contains such a
number. The US Air Force repacks on a             requirement. For the acceptance of the
cycle of 120 days, the German Forces on           used materials it had to be shown that the
                                                  quality of other, flame resistant materials


                                          Page 3 of 4
sistant materials are worse in terms of               a water activated parachute release. The
strength and life time and a modification of          Parachute Survival Equipment is made
the Durachute by using such materials                 for high altitude emergency bailout
would decrease the quality. Moreover it               (25,000 feet above ground level). The
was expected, that the FAA qualification              E-2C aircraft configuration e.g. is
have to be renewed, as these modification             equipped with an oxygen system, an
can be considered as major design                     automatic activation device, a vacuum
change. However the parachute is in use               sealed life raft and a survival kit. Custom-
in the US Navy with the same inflammable              ized adaptations are possible.
materials, it was finally accepted by the
German authorities.
                                                      CONCLUSION
The certification of the German Durachute             The Thinpack/Durachute emergency bail-
is expected for May 2003.                             out parachute system has demonstrated
                                                      the feasibility of a vacuum-sealed para-
                                                      chute concept. As a viable alternative to
SEAT INTEGRATION                                      standard rescue parachutes the system
Due to the small volume of the sealed                 presents many advantages, e.g. an ex-
parachute the Durachute can be fully in-              tended repack cycle of 5.5 years and a
tegrated into fixed-wing and helicopter               longer life time of 27 years, causing sub-
crew seats. Provisions for the integration            stantial reductions of maintenance time
of the Durachute have been completed                  and costs. The system has a low weight
for the E-2C Hawkeye, the EH-101's crew               and a small volume, that makes it suitable
seats and other helicopters.                          for the integration into aircraft crew seats.

The Durachute replaces the seat and
back cushion of the crew seats with a                 REFERENCES
combined seat and parachute harness,                  Lance C. Labun, Eric Smith and Ken
as shown in picture 3. After releasing the            Sego, Development of an Environmentally
parachute from the seat, the crew mem-                Sealed Bailout Parachute, US SAFE
ber is equipped with the parachute and                Symposium 1992
survival kit. This allows easier and faster
egress.
                                                      BIOGRAPHIES

                                                      Dipl.-Ing. Heiko Froehlich, Project Man-
                                                      ager, Autoflug GmbH, Industriestrasse 10,
                                                      D-25462 Rellingen
                                                      Phone: (+49) 4101-307257,
                                                      E-Mail: h.froehlich@autoflug.de

                                                      Mr. Heiko Froehlich is project manager in
                                                      the sales department of Autoflug and since
                                                      two years involved in several parachute
                                                      projects. He is responsible for the German
                                                      military qualification of the Durachute. He
                                                      is an aerospace engineer and has 8 years
               Picture 3:                             of experience as Technical Officer in the
    Seat integrated Durachute and                     German Air Force.
  Pilot equipped with Durachute and
          Survival Equipment

The Durachute can be equipped with an
automatic activation device (e.g. Cypres)
for automatic parachute deployment and



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