THE GLIDING FEDERATION OF AUSTRALIA INC
BSE Canopy and Perspex Theory Work Book
Student Name: ________________
Mentor/Tutor Name: ________________
UNCONTROLLED WHEN PRINTED
Revision 1.0
This issue of <Document Name> replaces the one issued in <Previous Release Date>
GFA Document ID: TWB007
Copyright © The Gliding Federation of Australia Inc, 21/04/16
BSE Canopy and Perspex Theory Work Book, TWB007
REVISION RECORD
Prepared
Approved
Version
Date
Peter Cesco
Vice President
1.0
21/04/16
Précis of changes – New
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 2 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
ABOUT THIS WORKBOOK
This workbook is intended to be used to enable improved understanding of specific theory aspects of
Sailplane maintenance delivered by experienced sailplane inspectors. It is intended that this manual will
be completed after theory training has been presented as part of an airworthiness training course.
It should be used in conjunction with the Gliding Federation of Australia’s Manual Of Standard
Procedures (MOSP) and any relevant aircraft documentation.
This workbook is a working document, reinforcing the information presented.
Each student has their own copy of the workbook.
This THEORY workbook is not intended to be a pass/fail document, but is intended to be used as part of
a knowledge and skill building exercise in a specific topic area
This unit has been designed to provide you with some of the necessary skills and knowledge to be able to
operate and think your way through the technical skills of identifying and selecting the correct fastener or
fastening systems used in sailplanes.
The module is not exhaustive and is should not be used instead of correct technical documentation or
better knowledge. The module is designed to be done by you in your own time.
You are encouraged to seek information from more experienced sailplane inspectors, aircraft LAME
sources and/or specialist knowledge where it can be found.
Sailplane maintenance requires effective human intervention to places the aircraft back on the flight line
in a serviceable and useable manner after maintenance, and should not be rushed.
You will also be issued with an assessment feedback document to allow you to give your feedback on
both the module applicability and improvements, and your mentor/tutor/trainer. Please complete this
honestly as it is your chance to assist us in maintaining the standards necessary.
The single best thing you can bring to ensure a quality airworthiness system is an enquiring mind.
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 3 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
CANOPIES
INTRODUCTION
Sailplanes have a number of important parts, canopies are one of these. They are an important part of
the performance characteristics of a sailplane, cost a considerable amount of money and can, if not
maintained correctly contribute to poor visibility in critical conditions.
Airflow inside a canopy contributes to a canopies anti fogging ability and a clear vision panel gives the
ability to have some vision should this occur.
A canopy and its frame are very easily damaged, especially when it is remembered that the canopy is
generally used to effect entry and exit from a sailplane.
But most importantly the Perspex used in a canopy needs to be looked after or it will craze, discolour and
render safe lookout nearly impossible in critical situations.
Canopies comprise a Perspex portion which is surrounded and supported by a canopy frame, they all
have a clear view panel, most have hinges that connect to one side, although some have a gas strut and
open upwards. There is also generally a canopy jettison system incorporated into the canopy frame.
Reference GFA Basic Sailplane Engineering
As you approach the review of the status of the canopy you will need to consider the following:

Has the canopy been cleaned properly before each flight? look carefully for scratches.

Has the canopy been covered to protect it from UV light when it was waiting for the launch?

Are the securing screws/bolts secure and not loose?

Are there any cracks? especially in the Perspex and around the clear vision panel.

Is the mechanical attachment to the canopy frame secure?

Is the canopy jettison system in working order and functioning?

Is a yaw string attached?

Where am I going to store the canopy so it will not be damaged after it is removed and the aircraft
fuselage is undergoing an inspection.
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 4 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
ACTIVITY 1
Review and identify the activities needed to conduct an initial review of an aircraft canopy.
Describe how you would conduct the following actions:
a.
Identify the general condition of the canopy
________________________________________________________________________
________________________________________________________________________
b.
Where and how would you place a canopy that has been removed from an aircraft for a
form 2 inspection?.
________________________________________________________________________
________________________________________________________________________
c.
Describe what you would look for on the frame of a canopy?.
________________________________________________________________________
________________________________________________________________________
d.
What would you look for initially regarding the canopy jettison system.
________________________________________________________________________
________________________________________________________________________
e.
What would you use to clean and polish the canopy?.
________________________________________________________________________
________________________________________________________________________
.
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 5 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
DAILY AND ROUTINE CARE OF A CANOPY.
INTRODUCTION
It is important that canopies are taken care of on a regular basis. This includes cleaning and polishing,
use of canopy covers, not lifting with the clear vision panel, locking when left or moving the glider and not
wearing hats with pins and badges on.
CLEANING THE CANOPY
Canopies should be cleaned each day they fly with clean water and a mild soap. A clean chamois or sponge is
generally best but it is essential that it has no grit on it as this will scratch the canopy and undo all your
good work. It is also important to dry the Perspex off with a clean chamois so that dirty splotches are not
left on the canopy to impede the pilot’s vision.
Do not use any gasoline or alcohol based products to clean the Perspex as these may have an effect on
the Perspex by causing crazing or softening as well as being a personnel safety and fire risk.
Generally do not use silicon based cleaners on canopies as these may interfere with repairs to fibreglass
or fabric if needed in the future.
POLISHING THE CANOPY
It is the pilot’s and glider maintenance engineer’s best interest to polish the canopy at least annually to
rejuvenate the Perspex and remove static electricity. There are a number of quality perspex polishes that
will do both of these things. Static electricity causes dust particles to cling to the canopy and reduces
visibility, particularly when looking into the sun and, as a serious risk to visibility, should be minimised if
possible.
It is also important not to polish in one spot for too long as this may soften the Perspex by generating heat
and distort the visual qualities of the canopy.
Canopy covers reduce the temperature in the cockpit, reduce the risk of minor scratches and reduce the
ultraviolet rays that go into the cockpit. A good quality canopy cover is snug fitting and clean, if it is not it
will allow dirt to get under it and scratch the canopy.
Reference GFA Basic Sailplane Engineering
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 6 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
ACTIVITY 2
Daily and routine care of a canopy
Discuss the following items:
a.
Identify the best cleaning agents for a canopy, and how would you use them?.
________________________________________________________________________
________________________________________________________________________
b.
Discuss why you would polish a canopy and explain what you need to consider when
doing so?
________________________________________________________________________
________________________________________________________________________
c.
Why do we use canopy covers, what do we need to be careful of with a new canopy
cover?
________________________________________________________________________
________________________________________________________________________
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 7 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
PERSPEX
INTRODUCTION
Canopies are made of Perspex, so it stands to reason that we should understand something about this
material and how to use it, or work with it.
Repairing Perspex is a time soaking process, and needs to be carefully considered and special care
taken. The result of a hasty repair will often be poor visual qualities; if these are bad enough the canopy
will need to be replaced.
CUTTING PERSPEX
A fine toothed saw, with a minimum of 14 teeth per inch should normally be used. Finer saws should be
used as the thickness becomes less.
Sawing should be done at least at 20 degrees Celcius, this will minimise the chances of chipping or
cracking.
DO NOT force the blade through the Perspex, allow it to cut at its own rate and ensure the cut surface is
finely polished to remove the possibility of cracks propagating from the notches.
CRACKS AND STOP DRILLING CRACKS IN A CANOPY.
Perspex is prone to cracking in areas of stress, such as around the clear vision panel if people lift the
canopy from there. These cracks will continue to grow and eventually render the canopy unserviceable
unless something is done to stop it.
As soon as a crack in the Perspex is identified it should be ‘stop drilled’, this involves identifying the end
of the crack and drilling a small hole just beyond that point. The crack will affect the area just in front of it
and so the hole needs to ensure this stressed area is not left to continue the crack after the drilling is
complete. As a general rule a 3mm hole should be drilled, however very small cracks may have smaller
holes.
This ‘stop drilling’ needs to use a specially ground drill to ensure that no extra stress is exerted on the
Perspex, extra stress may start more cracks. It is also very important that the drill is allowed to do the
work and to use only a light pressure to minimise any increase of stress.
PERMANENT REPAIRS
Stop drilling will not stop a crack that can have movement between the two sides of the crack, in this case
a permanent repair should be affected.
Small fine cracks can sometimes be permanently repaired by placing a small amount of perspex solvent
in the crack and letting it move into the crack by capillary action.
If this method of repair is not suitable, the crack will need to be repaired by cutting a V shape using a
scraping action, ensure the resulting area is very clean and use tape to retain the Perspex cement and
protect the remainder of the canopy from runs. Then, using Acrifix 92, fill the V area, making sure there
are no air holes left at the bottom.
SOLVENTS AND GLUES
Perspex suppliers will be able to supply suitable proprietary Perspex solvents. These solvents should only
be used in well ventilated areas using gloves and close fitting safety glasses as they may be toxic and
dangerous to use. Read and follow instructions on the container.
Acrifix 92 is the glue generally used in Perspex repairs.
Acrifix 92 uses UV light to cure, and so must be left under a UV light or in sunlight to complete the repair.
It will naturally shrink as it cures and it may be necessary to fill the V area after the initial cure.
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 8 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
Acrifix cures clear and the only evidence of a repair will be any air bubbles that were allowed to form.
LEVELLING AND POLISHING A PERMANENT REPAIR.
After 24 hours of curing use a scraper to reduce the build up to the surrounding level of the Perspex.
Polish the area starting with a 600 grit paper and finish with a very fine polish. The Micro-mesh method is
probably the best.
SCRATCH REMOVAL.
Small amounts of scratching can be removed by using canopy scratch remover, this slightly abrasive
polish grinds the material away until the scratches are gone. It is important not to use too much pressure
when doing this as you may overheat the local area and warp it out of shape, also, if it is too localised you
may cause a visual discrepancy because of the unevenness of the surface.
Significant scratching will require more work. The best method is to use the Micro-mesh system which
sands the surface to remove deeper scratches. The system starts with 1,500 grit paper and finishes with
12,000 grit.
POLISHING PERSPEX.
There are a number of quality Perspex polishes available, these will minimise static electricity and give a
consistent clear vision. They can be mechanically used but will quickly overheat the canopy if left in one
place for more than a few seconds. It is generally best to carefully hand polish canopies to minimise the
potential for canopy damage from this activity.
PERSPEX ATTACHMENT TO CANOPY FRAMES.
Your role as a form 2 person is to ensure that the Perspex is attached securely.
Securements of Perspex to canopy frames are usually in two types:
d.
metal frames generally use securing screws or bolts. Check the Perspex is not loose in
the frame and no screws or bolts are loose, if there are any screws or bolts loose,
GENTLY tighten them ensuring you do not overtighten as this will cause stress and crack
the perspex.
e.
Composite frames are bonded on and debonding can often be indicated by cracks in the
frame or gaps between the frame and Perspex.
Reference GFA Basic Sailplane Engineering
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 9 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
ACTIVITY 3
Perspex
Discuss the following items:
a.
Describe what you would use and how you would cut a piece of Perspex.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
b.
2. How and why would you stop drill a canopy.?
________________________________________________________________________
________________________________________________________________________
c.
What would determine that you need to do a permanent repair on a canopy?
________________________________________________________________________
________________________________________________________________________
d.
When would you use a Perspex solvent?
________________________________________________________________________
________________________________________________________________________
e.
Discuss the difference between scratch removal and polishing Perspex.
________________________________________________________________________
________________________________________________________________________
f.
What would you look for when checking for Perspex security on a canopy frame?
________________________________________________________________________
________________________________________________________________________
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 10 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
CANOPY JETTISON SYSTEMS
INTRODUCTION
Most sailplanes have a canopy jettison system. Some will be specific canopy jettison systems, others,
typically older designs will be incorporated in the normal canopy opening system.
Regardless of the type, it is important and required that the jettison mechanism is serviceable and
working at each annual inspection.
DISABLING CANOPY JETTISON SYSTEMS.
Occasionally it may be deemed prudent to disable the canopy jettison system. A reason for this may be to
fly a small person who may not be able to reach the controls, but may be able to reach and accidentally
activate the canopy jettison system.
In this case the canopy jettison disablement would be removed immediately after the flight.
The general rules around disabling Canopy Jettison Systems are:
1. The disablement must be entered in the Maintenance Release
2. The aircraft cannot be flown with parachutes
To prevent inadvertent operation by placing a soft wire that can be broken in a jettison system is
acceptable, providing the person installing the wire checks does a function test to ensure the soft
wire can be broken. Suitable Fuse wire is acceptable for this function.
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 11 of 12
BSE Canopy and Perspex Theory Work Book, TWB007
ACTIVITY 5
Canopy Jettison Systems.
Discuss the following items:
a.
How and why might you disable a canopy jettison system?
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
b.
At a form 2 is the canopy jettison system required to be operational?
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Version 1.0
Date of Issue: 21/04/16
Uncontrolled if Printed
Page 12 of 12