Posted for John Smith
<john@jjts.net.au>:
> I have posted on the forum a while back what I had done at that time. Below,
> is an update on thatŠ along
with what I'm doing now.
>
> If its helpful to anyone out there, that's good. If you're entirely happy
> with what you're doing,
please still read on as you may well be able to
> provide some valuable insight as to perhaps why nothing else needs to be
> done around
"the Legacy Canopy".. or perhaps those that have experienced
> flight with the canopy open what IAS did you fly the aircraft
at? Did you
> leave flaps and gear extendedŠ and so on, so you can help others understand
> how they might be able safely
return for a landing with a canopy open.
>
>
> Current status
>
> Alarm
> * I have two micro switches installed
in series to indicate an issue with
> the canopy
>> * One is under the internal closure handle and unless the handle is in
the
>> close position within ~1mm, the switch will not close
>> * The other is within the pilot side cockpit opening joggle at the
back of
>> tyne opening, and unless the canopy is seated to within 1 2mm, the switch
>> will not close
>> * Thus if
either the canopy is not seated or the internal handle is not in
>> closed position, or if there is failure of the switches or wiring, an
alarm
>> condition is identified
> * I used to have this alarm showing up on my annunciator panel top RHS of my
> panel pretty
useless to be honest when cockpit is flooded with light
> * I am fortunate to have dual EFIS units, so all it took was to run another
>
wire to the EFIS system, and programme the EFIS to display a large red
> flashing warning "ALERT CANPY" both pilot side and co-pilot side.
This
> accompanied with a "BEEP BEEP" happening in the headsets. See attached
> picture of how the visual alarm
appears.
>> * If I didn't have EFIS, I would have installed a very bright LED warning
>> light pilot side and co-pilot side top of
panel, along with a very loud
>>buzzer
>> or horn
> Normal Procedures
> * My Run-Up and Line-Up checks include "CANOPY
CLOSED, LOCKED, ALARMS OUT"
> Emergency Procedures
> * I have acknowledged that there MAY be an issue with controllability, but I
>
don't plan to wait to find out for sure. So I have adopted (with the same
> priority as EFATO procedures) a procedure which says "IF CANOPY
OPENS AT ANY
> POINT PRIOR TO TAKE-OFF => ABORT DO NOT PROCEED AIRBORNE" Beyond that,
> and not knowing if
this would work: "IF CANOPY OPENS IN FLIGHT AFTER
> TAKE-OFF MAINTAIN 140KTS, LEAVE FLAPS / GEAR EXTENDED, CLIMB TO 500ft
> BEFORE
POSITIONING FOR APPROACH TO LAND NOT BELOW 100kts"
>
> In my opinion, no Legacy should fly without the above or put another
way,
> I can't see the downside for essentially a few micro switches and
> recognition of some very simple procedures. I'm sure that many
will argue
> that the alarm as described above is not helpful but take a look at the
> picture and ask, is it more likely than not that
you would notice this red
> flashing warning as you line up and / or commence a take-off roll? UNLESS
> take-off is done
without any reference to instruments - but assuming that
> was the case, and canopy is not locked, it presumes both Run-UP and Line-UP
>
checks have also been ignored tends to suggest a different problem all
> together.
>
> But at the same time, I absolutely
recognise that there will be times when
> no amount of alarms, warnings, procedures won't protect but on balance, I
> find it hard to
argue that they won't reduce risk.
>
>
> What I'm doing now
> * Over the last month or so, I have been working up a number
of ideas for an
> automatic secondary latching or restraint mechanism. In some cases, pretty
> much to the point where CAD drawings could
be put together and DXF files fed
> into a CNC machine. But not so fast. Each idea needs to be screened
> against all the obvious net
benefit, reliability, simplicity, operability
> (latter must be from perspectives of a pilot, passenger and rescuer). I'm
> used to the
term HAZOP (hazard and operability assessment) sounds fancy /
> complex but its pretty straightforward (identify failure modes,
operability
> issues etcŠ rank as a function of likelihood or probability etc.). However,
> it does rely on a group of informed
persons contributing to make sure that,
> as far as is practicable, nothing is missed and the best solution is
> uncovered
> * The
geometry and structure of the canopy and hull make for some
> challenges, as does also managing retrofitting something to a shiny
>
completed machine but I'm sure it can be done
> * I have as it happens physically seen the SS spring steel device used on a
> VariEze
it may ultimately be the best solution but right now, my concern
> is over a "rescuer" begin able to quickly find, reach and then operate
the
> spring steel tab under difficult conditions. Beyond this idea, I have thus
> far explored ideas ranging from inertia reel seat belt
devices attached to
> the top of the canopy, electric solenoid operated pins that self latch but
> require power to open (self contained
battery!), pneumatic solenoid
> equivalents, and mechanical linkage variants! All have their pro's and
> con's but my "spec"
if you like is essentially this:-
>> * Must automatically latch when the canopy is lowered (as some have
>>suggested
>>
like a car bonnet safety latch)
>> * Must be obvious and easily operated and released by pilot, passenger or
>> rescuer
>>
* Must have alternative emergency opening capability (this is the scenario
>> where the auto latch does it trick when you put the plane away
after a fly,
>> and you come along some other day and the normal external release has
>> failedŠ..)
>> * Goes without
saying that any device needs to be as simple as it can
>> practically be, and should ideally be relatively easily accommodated
within
>> the geometry / structure of the Legacy so it doesn't become a deterrent for
>> folks to install / retrofit to an already
completed aircraft
> * I need to do a bit more work around some designs / drawings for the above
> ideas, and then I'd be in a position to
share those with the objective and
> working collaboratively to find a solution the more brains and pounds of
> experience we can bring
to bear the better!
> * BUT who knows the conclusion drawn from looking at secondary latch ideas
> may very well be that the risks and
consequences of installing a secondary
> latch outweigh the perceived benefits => "do nothing". At least the election
> can be a better
informed election. As some say, or words to effectŠ. "If you
> know why you do or don't do something, it might helpŠ..
> * However, the
process of dialogue throws up some quite different ideas /
> approaches / possibilities
>> * Fred Moreno and a colleague have pondered
whether damped gas struts that
>>may
>> offer the potential to stop the reported oscillating canopy scenario (most
>>
recently observed with VH-ALP)
>> * Is it possible that IF the canopy opens in flight, it only lifts a small
>> amount and is stable
(as some have observed and experienced) IF the ball is
>> centered; may be, just may be, if there are rapid power changes and / or
the
>> ball is not way off centre - does the slip invite the air flow to come up
>> under the canopy and push it up
higher (and drop if slip is removed)?
>> * A recent post reports a canopy rises when full power is applied (and I
>> presume
therefore nowhere near becoming airborne?) - may be all Legacy
>>owners
>> need to go out and check that for their aircraft this
does occur, because if
>> does, wellŠ pretty much the obvious
>> * Some report no issues if the canopy opens in flight - which
surely begs
>>the
>> question why do some? So don't we need to try and fathom out why this
>>might
>> be what have some done, but others not?
>
> Anyways I'd like to hear from anyone who wants to work
together to share
> and develop / assess ideas for a secondary latch (or not as the case may
> be!) and develop sound (perhaps experience
based?) emergency procedures. May
> be we can split it up a group looking at latches? A group looking at
> emergency
procedures / how to fly safely with a canopy open? Any
> volunteers?
>
>
>
> Cheers,
>
> John
> VH-XTZ
>
> John N G Smith
> Tel / fax: +61-8-9385-8891
>
Mobile: +61-409-372-975
> Email: john@jjts.net.au
>
>
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