Technical issues and guidesNOTE: This page was originally hosted at http://www.woodleydowns.demon.co.uk/TechnicalIssues.htm, but that site no longer exists. This is a copy from the http://web.archive.org/ site.
Please help everyone by passing on your good and bad technical issues.
Email me firstname.lastname@example.org (E-MAIL INVALID!)
A number of people have changed their wooden duck billed wooden peg mouth throttle for ones suitable for use with full face crash helmets. So far I have seen a couple (mine included) build by Dave Bremner, which are made quite small out of aluminium alloy on a sliding system. Works well but the end of the outer cable sleeve tends to allow the inner cable to bend and causes sticking throttles. Also it gets dirty easily, and being fairly lightly sprung will easily become gritty and tight to operate. Washing in Silicon lubricant removes the dirt very well. A few others have a similar but larger sliding version which works well but is tighter to get inside the helmet chin guard. Are there any other versions out there. I believe that a design is being worked on in Sweden for future new mosquitoes.
I find that the mouth throttle outer cable easily gets bent during pre-flight writhing at the junction with the alloy longitudinal tubing, and turns the throttle on someway and then sticks at this point. I have sheathed the existing outer cable sleeve with Polythene tubing (greenhouse drip feed tubing), and then a short length of polythene camelbak tube, but have yet to actually fly with it. When I removed the heat shrink wrap from around the outer cable and alloy tube next to the throttle switch, the outer cable had actually spread apart from bending, causing friction.
The current status of costs to obtain an endorsement from the BHPA to fly flphg's has led to some confusion. You have to pay a small fee to get the training pack and then another small fee to do the exam once you have flown the hours etc.
Brian Sanderson has provided some info on how a parachute should be attached. See Brians WEB home page for more info.
Listed below are pilots thoughts on the potential problems related to
the ignition on/off switch on the Mosquito harness.
thanks for contributions to;
Alain Levy, Peter Hook, Richard Sheppard, David Bremner, Roger Fenn
On my last flight (at the Mossie Fly-in last August) I tripped on take-off and nosed in very hard. Unfortunately I failed to spit out the throttle - OK my fault, but when it all happens that fast you don't always react quick enough. However, my point is that due to the fact that I couldn't find the Damn switch the engine revved at full throttle with only half a prop and the result was a bent prop shaft, amongst other things! So I would very
much like to create a better system. I had in mind a push-pull switch, still in the end of the side tube, with a large diameter button (just bigger than the side tube) which you
could push in very easily to kill the engine. (I too have had difficulty finding the current switch before landing). This would also be easy to operate in gloves for switching back on again in flight. Also, I want to add a little electronic wizardry inside the tube which
would cut the engine on impact (triggered by large G forces). Maplins do a little unit which is triggered by a 5 G force.
I too have had the pleasure of looking for pieces of Prop in a field!, and boy do they go a long way. In my case it was because I had been writhing around trying to start the
engine, and had moved the hand throttle open, which meant that the engine fired and threw me forward throught the A frame. I have talked to a number of electronics wizards about an automatic switch to close the circuit if the revs rise above a certain value (just above tickover), but haven't progressed it any further because of the number
of technical problems invloved (no Info on ignition system from Andy, costs). This would not have helped in your case. I like the idea of a push/ pull switch, which could be a throttle control as well. If the plunger was fully in, then the ignition is off - which means that in a rush you just push hard against the plunger. To start the engine, the plunger would be pulled out to a clicked position. When in flight, the plunger could be pulled out. The plunger would need to be large and smooth to allow use with gloves, but
not be possible to pull out accidentally by getting caught on the harness fabric etc. Where can I get such a switch which combines mechanical and electrics?. My suggestion for the switch design - can anyone make it? (NOTE: image no longer available)
I ALWAYS fiddle to find and operate the switch (especially with gloves) to cut off the engine before landing. How do you manage? Has anybody thought/designed/bodged up a "jumbo switch" to fit on the control bar (or even the upright?) linked with some "curly telephone wire" to the front of the Mozy. Any suggestion welcome?
I have managed to switch off whilst trying to find the zipup tag at 500'
(managed to restart)!. If the switch was any longer It would get in the way.
The problem with switch extenders is that you would tend to catch it when you DIDNT want to - I already have enough trouble with the hand throttle catching on the upright during the start-up sequence. Both these areas could do with looking at, but I can't think of anything very constructive yet.
It used to be possible to get switch extenders for the switches on the dashboard of a mini made of rubber. Would this help? If so I suppose you could try a motor accessory shop to see if they still sell them.
Now... what about a plug arrangement that would cut the ignition when
you Yank out your 'chute. (this is something that concerns me).
I like you also have problems with the ignition switch. I usually just pull the choke on which always cuts the engine and leaves it in a better condition for air starts (In theory anyway - practice proves otherwiswe!) I know this isn't ideal in case of emergencies. Maybe packing the switch out so it doesn't sit so deep in the plastic cup would help.
BTW I had a few problems extending the stingers after folding them up. The
string seemed to get caught in the throttle/choke assy area. Do you have this
hassle? I took the retracting string off for now so the legs stay out when I
zip the harness up.
Mosquito with Radne raket 120
After running perfectly, when started up the engine would idle at around 6000 rpm. Fortunately the propellor was not fitted at the time.
Investigation eventually found that the exhaust manifold had come loose at its connection with the engine body. One of the nuts had unscrewed itself completely and the other bolt had become slightly loose.
Mosquito with Radne raket 120
Some people have had problems when using a radio when the engine is running at anything above idle. This has been resolved by either of 2 methods.
1)Use a microlight helmet with build in headset. This is excellent for sound quality, but is quite heavy to use in the prone position, and expensive to buy. Generally microlight helmets are open face which may not be preferred by some pilots flying headfirst (prone). Chris Creasey uses this arrangement, but has a special set of eastic bands attached to the helmet to keep his head up and stop it aching.
2)Use an in the ear speaker system. I have one which is normally used by secuity gaurds, bouncers etc and works well, whilst allowing me to use my existing full face carbon/kevlar helmet without modification. You do need to put an ear plug in the other ear for long flights to reduce the background noise.
When flying in the prone position, it is possible to get discomfort from a heavy helmet. This can be completely removed by using self adhesive velcro on either side of the helmet, to which is attached both ends of a cord. A roller slide is attached to this cord, and a piece of 4mm diameter elastic is then run up to the hang point, where another yachting roller allows the cord to go back down to a cleat on the side of the Mosquito harness. This cleat can be used to adjust the tension of the cord in flight, depending on your angle of dangle and engine power setting.
From Brian S- referring to Mosquito
After several engine falterings after take off I find the following seems to
work. Squeeze the bulb and tickle the carb until the bubbles and fizzes from the
sight glass end. Continue squeezing a little longer until the tickler fizzes.
Continue until the fizzing stops.
From Brian S- referring to Mosquito
Hip padding might help the comfort level (anybody tried that?), or is the back
strap perhaps too tight? Will try easing it off a bit next time. Stirrup in
rearmost position digs in to instep. Might be more comfortable without the
stirrup, but then feet might cause harness to contact moving parts? Why do
harnesses have stirrups anyway? The longer engine to carabiner strap has eased
the angle of dangle problem, but not by a hugh amount. I still like my foam
padding on the chest and shoulder straps.
From Brian S - referring to Mosquito
I got into the harness with no real difficulty today, holding on to the uprights
and stepping in. It would be easier if the zip opened further, but that might
weaken the harness too much? The nose anchor length is critical here. Too short
and I overbalance forwards. Too long and the anchor might pull out.
Froam Brian S - referring to mosquito
Honing my `getting out in wind technique I make a right mess of the first
attempt. Equipment: tent pegs in harness pocket, cord from nose loosely wound
down a nose wire, pliers in back pocket (in case of a carabiner jam). First go I
try to peg the nose before getting free of the harness. This eventually results
in the nose going down, then getting it back up I dont notice a rear wire is
inside the side bar. It gets its plastic protection stripped as I raise the nose
and a leg gets deformed at the bolt.
Next time is much better. The trick is to undo the petrol then the back strap,
then the carabiner. Step out easily and only now secure the nose. The limiting
cords can then be undone. Or is there a better way?
I have modifyied the mosquito pull start to also enable kick starting in the air, which allows a faster short pull making starting easier.
On the plastic blanking plug at the front of the pull cord tube has been attached a lightweight yachting roller. the existing pull cord has had added to it (attached via a coppper swage), an additional cord which runs back down the outside of the tube. Part of the way along the lenght of this new cord is attached a loop of cord, reinforced by plastic tubing to allow entry of the heel of the foot. The end of the new cord is swaged onto a long length of 5mm elastic shock cord, which goes around another roller attached via a leg bolt to the mossy body. The shock cord is attached to the eye passing throught the mossy longitudinal tubes. This allows the shock cord to stretch enough to allow hand pull starting, yet keeps all the new cord nice and tightly out of the way.
This system works well, and is particularly useful if your engine is a pig to start (like mine).
I have not tried this on the ground, but imagine that it would work equally as well, as long as you were already lying down in the prone poition.
It is amazing how little effort is required to kick start compared with using your hand in the awkward flying position.
NOTE: Linked images no longer available
Thanks for the hint. Since then I've experimented and devised one of my own which uses a small yacht pulley loosely attached (with string) to the knob
where you put the choke handle, and attached a foot loop to the handle itself. The blue cord goes through the pulley of course and you use the
heel to kick into life. I haven't looked back since because starting is so easy now particularly just before take off - you can hold the glider steady
and completely avoid a deployment and heart attack all at once! I have to thank you for the inspiration though, I'd never have thought of this on my
NOTE: Linked images no longer available
swedish Aerosports have created a new plastic air intake silencer box, which is a bladder shaped container, ending with an intake dust filter.
Quite a few were sold at the Telford show. This is what Andy Buchan has to say about it.
"I flew with the intake silencer - it seemed to take out a lot of the
crackle and I did not need ear defenders. Those on the ground said that it
was quieter, but I have not yet heard it from below."
It has to be permanently fitted onto the carb', and becomes a problem to fit in the old style carrier bags, which were a very tight fit around the mossy unit.
Anyone else out there using this or any other air intake filter/silencers?.
From Andy Buchan - Mosquito agent
With the air density changes in winter you may need to have the mixture
screw further out to richen the tickover mixture - try 1 1/2 turns out, it is
usually 1 1/4 turns, but can vary between engines. A too weak mixture is
hard to start, a too rich mixture can run rough when slow.
The following detail is specific to Mosquito mounted with the radne Raket 120. However it is probably identical to most other units using this engine.
First of all remove the 4 allen key head bolts from the red pull start housing.
Pull the housing away from the engine gently, bringing the rope tube along with you.
Using an allen key and socket spanner, loosen and remove the allen key bolt and nut that go through the housing and alloy pulley.
Gently pull the pulley away from the housing, bringing with you the black plastic spring housing which is behind the pulley wheel.
Ensure that the spring does not come out of the plastic housing, it will burst out violently, and may cut you, and if it is the new one then it may be damaged itself.
Place the new spring, within its new plastic housing that it comes in, plastic side to the pully wheel. Ensure that the centre piece of the spring is fully into the cut out on the inside centre edge of the pully wheel.
If you are renewing the pull start cord at this point then you need to do the following;
cut the cord to the same length as before, and tie the pull start handle to the cord. Thread the cord down the plastic tube, and around the pulley. Poke the cord into the pulley wheel, and through the large cut out in the centre of the pulley. Tie a simple granny knot right at the end of the cord, and push the knot back to hide it within the cut out section.
Wind the cord onto the pulley tightly, without kinks, as far as you can.
Carefully bring the pulley and spring back up to the outer red housing, and ensure that the spring case fits into its wedge shaped opening.
Replace the centre allen key bolt and nut, ensuring that the brass washer, goes on with its flat side against the pulley surface. Tighten the nut, which should still allow the pulley to turn completely freely.
Using the small cut out on the outside edge of the pulley to locate the cord into, wind the pulley once or twice, to tension the cord. This can be seen by the pull handle being tight up against the bung end of the plastic tube, and when pulled, it recoils back again.
Now replace the red housing onto the engine body, be very cautious at this point. You will see that there are 2 spring loaded arms fitted to the engine casing, these are what the pull start actually pushes against. You need to ensure that they are free, and not trapped against the pulley. To do this, use a small screwdriver to flick them out, as you gently press the red housing up against the engine. If you are gentle you will know that this has worked because the red housing and the engine will butt flat against each other. To double check hold the housing to the engine, and pull the starter cord slightly and you will hear the spring arms clicking as you release the sord and allow the pulley to recoil.
Replace and tighten the four allen head bolts, tightening them evenly.
First thing I found when flying power was I could not see how much
fuel was left in my tank.
May be this will not matter as I get more experience, however I
bought a small round mirror from Halfords, about two inches dia and
The mirror is made from a plastic material and therefore quite safe
and can be drilled through with ease.
I drilled a series of 1mm holes around the circumference and sewed
the mirror to the back of my glove.
No part of the mirror can fall away into the propeller.
I can adjust the mirror position to see most parts of the glider etc
but find it most useful in viewing the fuel level.
I leave the prop off while running up the engine. That way no one can get
hurt. Of course be careful not to over rev. Note - Chris Creasey and Dave Thomas now all do this also.
I'm surprised at all this talk of fancy kill switches and have to
agree with Johan. I regard the kill switch as pretty much redundant
and only ever really use the choke whenever I cut the engine. A
simple method I have occasionally used (because I hate the mouth
throttle and have never used one) is to clip a piece of thin line to
the ring on the choke and the other end, with a ring, goes over the
right thumb. It allows plenty of freedom during take off, the
transistion from upright to bottom bar is fine and if it falls off
after take off it's short enough to go nowhere. The length is fairly
important, not too short or too long. The idea was born from the
fact that I don't use a mouth throttle and wanted a way of killing
the engine in an emergency. It's a little more sophisticated than
described because I have a small piece of velcro on the right glove
at the base of the thumb. Another idea I've toyed with is a temporary
fastening to the bottom bar (a weaklink type attachment)so a bit of
push out closes the throttle. If you watch a pilot's actions after
spitting the throttle they then push out to slow the glider
momentum ..this second version uses this effect.
At the end of the day whatever you do has to work and in my case
doubly so because I have no throttle to spit!
The ignition switch on a Raket works by earthing the generator coil to cut
off. This means that if you have a break in the wires to the switch the
engine will be live - beware!
On simons idea of having a fuel cut off - both the Mossie and Bug have quick
release fuel line couplings, it would be just as easy to disconnect these as
to activate a fuel cut off, and has the advantage of only being one thing to
forget to connect / turn on when rigging!
In my experience aborted takeoffs are well worth practicing. It is easy to
go for it to such an extent that you will not give up until after you are
eating dirt. Two problems with this - one it hurts and two, it is all to
easy to persist with a bad launch and get into the air all crossed up, wing
down, no airspeed etc and perform the well know flphg manoeuvre of large low
level wing over followed by making onlookers run for their lives and smiting
the ground mightily. Practicing running up to takeoff speed and then
aborting is a useful exercise and requires getting used to the transition
from accelerating to decelerating - it is very easy to let the glider
overrun you and fall over. For this reason I would suggest that such
practice should be carried out incrementally working up from very slow to
faster speeds to get the feel of it. The biggest problem with aborting a
launch however is the mental change of gear. The way round this is to put
the thought of aborting if required into your mind as a concious one
immediately prior to starting your run.
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