Seems to me lock wiring the ballast dump system might be an
unapproved mod. unless the manufacturer has scheme to do it such as
where exactly and how it is done with the correct diameter
lockwire,0.025" or 0.032"?
We can play the stupid trivia game all day. All for lack of TRUST
that a pilot will obey a placard. You are forced to trust him or her
to obey the other placards.
BTW successful cultures tend to be high trust cultures. You don't
want to live in a low trust culture (aka the third world). Why the
authorities are hell bent on making this a low trust culture (or
defending its values) is beyond me.
I guess checking the dump vents are clear ought to be part of the DI.
There's only one vent into each fuel tank on the BD-4 and they aren't
interconnected. How many powered aircraft have two in the light aircraft field?
I agree it would be a good idea there too.
Mike
At 11:12 PM 4/25/2016, you wrote:
One should be careful on this matter. Please think again. I seem
to recollect a case in America with an FRP sailplane years ago where
the vents on the wing surface to the water tanks were taped over and
a flight in wave conditions was undertaken. Also the tank outlets
were closed and so the tanks were thus sealed . This did not present
any problems on ascent to some serious altitude (something like 15
to 20,000 feet). On ascent the excess higher pressure in the tanks
caused the tape at the vents to lift sufficient to bleed the air out
of the tanks via the vents progressively. The problem came on long
descent from high altitude where the air pressure differential at
the vents pushed the tape hard to the surface and prevented partly
or wholly the air flowing back into the tank. The result was that
towards the end of the descent both wing tanks, leading edge to
spar, collapsed due to the large and crushing pressure differential.
Many sailplanes have wing undersurface tank outlets where a tapered
plug sits into a tapered seat built into the wing shell. Higher
interior air pressure as compared to exterior pressure, such as in
the long descent situation above, will push the plug into the taper
improving the seal.
There is a good argument for duplicated vents to each tank with the
vent outlets in different locations, given that a vent may become
blocked say due to mud wasps.
The vents are there for a reason, because venting unwanted pressure
differential is good.
Regards, Roger Druce
On 23/04/2016 8:15 PM, Justin Couch wrote:
On 23/04/2016 2:30 AM, Jim Staniforth wrote:
Can a pilot tape over the dump holes to reduce noise, or is that a
breach of contract?
I'm pretty sure some tape over the holes would be fine - plenty of
gliders with underwing dump valves have a little mylar or rubber
flap over them for fairing purposes - our club DG1000 does. I've
seen tape plenty of times over the Jantar dump outlet too for the same reason.
I can't say for 100% coverage, but the flight manuals of gliders
that I've read state that the tanks should be left open if flying
without water. Obvious reason for this is to prevent the pressure
change splitting the wing open at altitude. A bit of tape won't
hold much pressure behind it so the manufacturers instructions are
still being obeyed anyway.
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