Dave B

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  1. Dave B added a post in a topic transponder   

    As I believe your Becker ATC2000 is about the same as my Microair 2000, I would recommend removing that 3¼ Slip indicator, and use a reducer plate in it's place to mount the transponder. Then use an add-on Slip indicator mounted on the bottom of the Airspeed indicator.


    Edit on 27 June: My mistake, I confused it eith other 2½ units, and also just noticed the slip indicator ia 2½ also.
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  2. Dave B added a post in a topic Made it to Idaho   

    Ya know, I'm always tickled when one of our Military Types (active or retard) gets a chance to scarf up on a flying dream.

    Keep truckin!!

    Ret. Army Chopper Jock, now flyin LSA/Experimental
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  3. Dave B added a post in a topic EGT Temps   

    I use this pdf to cross check my limits, both aircooled and liquid cooled. Resize, print, and tape to the panel....


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  4. Dave B added a post in a topic EGT Temps   

    And another. Back to basics, but great info....

    Fuel Systems Jan 2010

    Actual engine failures are rare. Almost all so called "engine failures" are
    returned to service without ever working on the engine itself. It's the
    systems which support the engine that usually fail and fuel systems fail
    more often than all other things combined. Most of those failures can be
    easily prevented and this article will show you how.

    RON and MON are two slightly different methods used to determine gas
    octane. European countries use the RON method only. Our American
    pumps have a label on them which shows that the advertised octane was
    calculated as RON plus MON divided by two. If your engine manual says
    to use 91 RON then you can use American 87 octane gas since its the
    same thing as 91 RON.

    Aviation fuel is often called 100LL. It is 100 octane but the low lead part
    is misleading. It does have less lead than aviation fuel once had years
    ago but it still has much more lead than any automotive gas. That lead is
    hard on our type engines because it fouls plugs and causes rings to
    stick if we use it on a regular basis. A few gallons of aviation fuel once
    in a while doesn't really matter much but I still avoid it as much as I can.

    Some "experts" claim that the volatiles evaporate out of gas so fuel
    goes "stale" fast. There is a tiny bit of truth in that but it certainly
    happen very fast. How long does gas have to sit in your car or lawn
    mower before you notice any difference? In my plane 3 or 4 weeks
    certainly doesn't cause any problems and I have gone twice that long
    with only a very minor difference in performance ... and I even premix
    the oil with my fuel. Don't get too paranoid about "stale" gas.

    Gas picks up small flakes of rust and dirt as it is pumped hundreds of
    miles through underground pipe lines. Slugs of water are inserted into
    the pipeline between different shipments and some of that gets mixed
    with the gas as it travels through the pipe. Large storage tanks at your
    local pipeline terminal always have some water and crap in them. Even
    the truck that delivers gas to your local gas station may contribute and
    of course water and crap in the gas station tank gets stirred up when the
    tank is filled. Gas companies try to filter the gas and most even have a
    filter right at the gas pump nozzle but some water and crap ALWAYS
    gets to our tanks. A lot of fuel problems happen shortly after refueling
    from a new source and even airports can have contaminated fuel.

    Some pilots filter the gas going into the tanks on the plane with chamois
    cloth, felt or a Mr. Funnel. It doesn't matter what you use or how careful
    you are to avoid condensation in the tank sooner or later there will be
    water and crap in your tank so you should plan for your fuel system to be
    able to handle some of it.

    The Mikuni pulse pumps are designed to suck fuel up to the engine and
    can easily handle the 3 or 4 feet of vertical lift needed with our engine
    and tank locations. Faucet recommends mounting electric pumps below
    the fuel tank because they can NOT produce much suction.

    Many people think that an electric fuel pump will provide an extra margin
    of safety. That's okay but make sure that you understand what you are
    doing or you can wind up LESS safe. Dual pumps can be used safely
    but you need to do it correctly.

    If you use pumps in series each pump must provide enough fuel
    pressure by itself in case the other pump fails. The second pump can
    boost the pressure of the first pump so high that the carb inlet needle
    valve can't close and then fuel will squirt out of the float chamber vent.
    prevent that you need a pressure regulator ... but then you depend on
    that ONE regulator to stay in the air. Wasn't your orginial concern that
    you depended on ONE fuel pump? Pumps in series usually add more
    potential problems than they remove. I do NOT recommend series use.

    For parallel use we usually use the Facet 40104 or 40105 4PSI pump
    when the pump is in the wings and the Facet 40106 6PSI pump when
    the pump is mounted low in the plane so that the carb sees the correct
    pressure. NONE of those models have a check valve built in so any
    time there is more pressure at the outlet port than is being created by
    the electric pump fuel will be forced backwards through the pump. If
    the electric pump gets turned off then a large part of the fuel flow from
    the Mikuni pump will flow backwards through the electric pump.

    With engines mounted high and fuel pumps mounted low even with no
    pumps running there is one PSI pressure on the pump outlet port for
    every 37 inches in height just from the head pressure of the fuel in the
    line up to the carb. For this discussion call that 1 to 2 PSI head pressure
    at the electric pump outlet when all pumps are off.

    Fire up the engine and the Mikuni will add 4 to 7 PSI on top of that head
    pressure to give about 5 to 9 PSI total at the electric pump outlet. The
    electric pump can only pump 6 PSI so fuel from the Mikuni can flow
    backwards through the electric pump at high engine speeds EVEN

    Electric pumps can force fuel backwards through the Mikuni pump too if
    it has grit in the internal flapper valves. Reverse flow can cause fuel
    starvation and other problems like unexpected fuel transfer to a different
    tank depending on how the pumps are connected.

    McMaster-Carr sells a good check valve to prevent reverse flow. Part
    # 7775K51 only takes 1/3 of a pound of pressure to open and it has a
    Viton seat which is rated for gasoline but you need two # 44555K131
    barbed adapters to install one in our fuel line. I strongly recommend a
    check valve on each pump outlet anytime there is more than one pump
    in the fuel system. I also recommend a fuel filter on each pump inlet so
    if one filter stops up the other pump can still provide fuel.

    If you provide a seperate fuel tank dip tube and fuel filter for each pump
    you can have two completely independent fuel systems as long as the
    two systems don't connect together except on the carb side of the check
    valves. There you can use a 4 port manifold, a cross fitting or two tees to
    provide for one line from the electric pump check valve, one line from the
    Mikuni pump check valve and two lines to the carbs.

    Two stroke engines use the piston to suck the air/fuel mixture from the
    carb through the intake manifold into the crankcase each time the piston
    moves toward the combustion chamber. As the piston moves away
    from the combustion chamber the mixture in the crankcase is pushed
    from the crankcase into the combustion chamber through the transfer
    port. This creates a small vacuum and then a small pressure inside the
    crankcase which we call a PULSE. A connection through the crankcase
    wall is connected to a chamber inside the fuel pump by a piece of
    tubing so the fuel pump diaphram can be moved by these pulses.

    Condensate forms when warm fuel/air vapor hits the cooler pulse line.
    If that condensate can not drain back into the engine it will collect in the
    pulse line or the fuel pump pulse chamber. Fluid trapped in a pulse line
    will weaken the pulse at the pump. Fluid trapped in the pump restricts
    the diaphram movement. Either one means less fuel gets pumped.

    Rotax drills a tiny drain hole in the Mikuni pumps which they supply with
    their engines. That hole is located at the pulse port connection to drain
    both the pump pulse chamber and the pulse line if the pump is mounted
    right side up and lower than the engine pulse connection. Click on the
    link below to see how to drill that hole. Some models have the hole in a
    90 degree brass fitting at that location.


    I don't do that because the hole weakens the pulse and the hole may
    get plugged with crap. I mount the pump right side up but above the
    engine pulse connection so that any fluid will drain out into the pulse line
    and the pulse line will drain back into the engine. Do NOT bolt the pump
    solid to the engine. Use mounting which isolates the pump from vibration
    and engine heat.

    Long pulse lines, leaks in the pulse line and thin wall tubing which can
    expand and contract with the pulses also weaken the pulses. Weak
    pulses move the diaphram less so less fuel is pumped. Pulse lines
    must be less than 18 inches long so the pump must be located near the
    engine pulse connection. You can use the engine pulse connection on
    the other cylinder to help keep the pulse line short on Hirths but Rotax
    only has one engine connection.

    It's not easy to do all that so some plane manufacturers take the easy
    way out and then problems develop over time after condensate builds
    up in the fuel pump or pulse line.

    I recommend the large round Mikuni pump since it can pump up to nine
    gallons (35 liters) an hour ... but that is only when they are installed
    correctly. Remember that they will pump less if they have installation
    problems. Both outlets come from the same internal chamber so cap
    off one outlet or tee the two outlets together if you only need one outlet.

    Its VERY rare to hear of any problem with a correctly installed Mikuni
    pump. They have been used on many brands of ATVs, cycles, jet skis
    and snomobiles for many years. They don't use electrical power and
    they have few moving parts. Those parts are replaced during a low cost
    rebuild which is so easy that anyone can do it.

    I think they are more reliable than electric fuel pumps so I use a Mikuni
    which I replace or rebuild every two or three years and I don't have any
    other pump on my plane. If I was concerned I would install a second
    Mikuni pulse pump for a backup. Hirth engines have a pulse connection
    for each cylinder and there is no reason that you can't use a seperate
    pulse pump on each connection. Rotax engines are limited to one pulse
    pump since they have only one pulse connection. Do NOT try to use two
    pulse pumps on the same engine pulse connection. That will cause both
    pumps to recieve weaker pulses and any pulse line problem will affect
    both pumps.

    Be a little leary of fiberglass and other composite fuel tanks. Every once
    in a while we hear about a tank which partially disolved because it could
    not handle ethanol or some other fuel additive. I suspect the wrong resin
    was used to make those tanks.

    I don't care what you use to filter your fuel or how careful you are there
    WILL be crap and water in your fuel tank. Your first line of defense is to
    leave a little room at the bottom of the tank where the crap can settle out
    without getting into the fuel lines.

    I don't like holes anywhere in a fuel tank except at the top. Sooner or
    later holes in the sides or bottom will leak no matter what you do. The
    dip tubes described below use a hole in the top of the tank so there are
    no leaks. If you already have a hole in the side or bottom of your tank
    you should use part #FTG-12240 from Wicks Aircraft. Those grommets
    are made of Viton instead of black rubber so they will stand gasoline
    service much better.

    With no drain on the bottom, you need some other way to get the water
    and crap out of the tank. A siphon hose will do that but I use a piece of
    1/4"OD stainless or aluminium tubing long enough to reach the bottom
    of the tank through the filler opening with enough extra for me to hold as
    I guide the probe to the low spots in the tank. 1/4"ID Tygothane tubing
    goes over the probe and connects to a squeeze bulb so I can suck out
    trash and water. I don't do it everytime I add fuel but I do make it part
    my regular maintaince routine. Do it after the crap and water has had
    time to settle to the low spots.

    Only planes capable of inverted flight need flexible lines inside the tank.
    Flexible lines can be a real pain in the butt and may collapse from the
    vacuum needed to suck fuel out of the tank. Do NOT try to use them.
    Do NOT use screens or filters inside the tank. They will get clogged
    sooner or later and you will have a hard time cleaning or replaceing them.

    A clear Fram G1 filter at the pump inlet will protect everything plus it's
    cheap, eazy to inspect and easy to replace. If you install it with the
    on the bottom and the outlet on the top it even tells you when its getting
    clogged up. When its new fuel fills the bottom part but the top part stays
    full of air. As the bottom part of the filter element gets clogged the fuel
    automatically rises to get through the unrestricted partt. Replace it when
    the fuel covers the entire element.

    The fuel line connection to the tank should be a metal dip tube which
    goes through the top of the tank and ends about 1/2" above the bottom
    of the tank to keep it above any water and trash in the tank. Do NOT let
    dip tubes lay against the bottom or sides of the tank. That can seal off
    the open end or let vibration rub a hole in the tank. Fuel will corrode
    copper or even brass but aluminium or stainless steel will work fine.
    Very large engines might need as large as 3/8 OD X .035 tubing for
    dip tubes but 1/4 OD X .032 will easily handle 5 or 6 gallons per hour.

    If the tank doesn't have any connections on top install a stainless steel
    panel mount coupling through the top of the tank. McMaster-Carr
    #5182K375 fits 1/4 OD tubing. It is like a normal tubing coupling except
    it has a threaded section in the middle so it can be inserted through a
    hole and mounted solidly in place by a nut. If you install a 7/16 viton,
    nylon, or PTFE washer as a gasket outside the tank it will seal fumes.
    McMaster-Carr #90295A186 is nylon. Use a metal flatwasher between
    the gasket and mounting nut to protect the gasket. The tubing nut and
    ferrule inside the tank are not used so that the dip tube can be removed
    later. The tubing nut and ferrule outside the tank will hold the dip tube
    place, seal around it and allow removal of the dip tube. There is a small
    shoulder inside the coupling which needs to be drilled out with a 1/4 inch
    bit before the tubing will slide all the way through.

    Most tanks have a small filler opening so here are some tricks to help
    install connections. Large drill bits make a sloppy hole in soft plastic so
    drill a small hole then use a tapered hand reamer to enlarge the hole to
    the correct size. Don't forget to deburr the hole. Drop a string down
    through the diptube hole then fish the string out through the filler
    Remove everything from the coupling body then push the string through
    the coupling. Tie a weight on the end so the string can't pull out of the
    coupling and drop the coupling in the filler opening. The string guides
    the coupling to the diptube hole as you pull it out. Install a viton, nylon
    PTFE gasket with a stainless flat washer on top to protect the gasket.
    Use Locktite when you tighten the mounting nut. Put both pieces of the
    ferrule and the tubing nut loosely on the top of the coupling and slide the
    dip tube through the coupling to the bottom of the tank. Pull it back up at
    least 1/2 inch before you tighten the tubing nut.

    A hand pump primer connected to the fuel pump suction line can leak
    air into the fuel system if the primer goes bad. I use a seperate 1/4"OD
    dip tube just for my primer to avoid that.

    A cheap fitting to use for vents in the top of tanks is a metal valve stem
    for tubeless truck tires from an automotive parts store. They have a nut
    for solid mounting in the top of the tank but throw the rubber seal away
    and use a viton, nylon or PTFE washer as a gasket. Remove and
    discard the valve core before you slide Tygothane tubing over the fitting.
    If you route that vent line below the bottom of the tank fuel will not leak
    out if you flip the plane over. If you extend the vent line out the bottom
    of the plane it will keep fumes and any slosh overflow out of the cockpit.
    I stick a fuel filter on the open end. It keeps bugs out and its my spare
    fuel filter on cross country flights. Any vent built into the filler cap
    be sealed off to prevent leakage and fumes when the tank is vented
    this way.

    New tanks and lines usually have construction crap left in them which
    often causes problems on the first flight. Clean and flush them out
    before you trust them.

    Some installations with more than one wing tank use a smaller header
    tank installed lower than the wing tanks. Fuel drains out of the wing tanks
    into the header tank which is then used as the main fuel tank. Header
    tanks often have serious problems with leaks so I recommend only an
    all metal tank with threaded connections welded in place for every
    opening needed. It should also include a welded connection for a drain
    valve to drain the water and trash which will collect there. Since the fuel
    uses only gravity to drain down into the header tank each wing tank must
    have a connection on the bottom and that connection often leaks. You
    should be aware that the vent used on the header tank must extend up
    as high as the vents on the wing tanks to prevent overflow. Without that
    vent, fuel may not drain into the header tank because air trapped in the
    header tank will try to work its way up to the wing tanks through the wing
    tank drain lines.

    Saint-Gobain is a very large company that includes several subsidary
    companies, factories and/or divisions. Combined they manufacture
    many different kinds of plastic tubing known by several brand names
    includeing Chemfluor, Fluran, Norprene, Pharmed, Tygon, Tygothane,
    Versilic and others.

    Tygon is probably the best known brand name but remember that there
    are many different types of Tygon tubing. Most types are NOT suitable
    for our application so be sure to check the formulation number. There
    are also other companies and they each have their own brand names of
    tubing made with different chemical compounds.

    Years ago some manufacturers tried to identify their products with
    different colors so that buyers could tell a supplier to "Give me 30 feet
    of the green stuff". When the "orange stuff" proved to be a better
    product or more popular competitors quickly colored their brand orange
    too. It quickly got to the point where color tells you absolutely nothing
    about what the tubing can safely handle.

    Today there are hundreds of different types of tubing available so we
    need to understand and correctly use some industry terms. Do NOT
    tell a manufacturer that that his product will be used with "gasoline",
    or "ethanol" because those mean three completely different things to him
    and none of them accurately describe what we really use to him. We use
    a 10% ethanol 90% gasoline mixture. Be certain that he understands that
    so he can recommend the correct product.

    We need a product that lets us easily see air bubbles inside the tubing.
    You will see several words used to describe how well you can see
    through the tubing. "Translucent" means that you can see light on the
    other side but you probably won't see details like air bubbles. "Opaque"
    means you can't even see light through it. We need "transparent" or
    "clear". Sometimes a color is opaque and sometimes its like the tinting
    on your windshield. Its there but you can still see through it fairly well.

    We need a product thats flexible. If the minimum bending radius is
    more than four or five times the tubing OD then it may get kinked shut
    in our application.

    We need a product thats soft enough to seal easily on some of our
    fittings so it needs to be less than about 90 on the Shore "A" durometer
    scale. It also needs to withstand hose clamp pressure so it needs to be
    more than about 60 on the same scale.

    We need a product thats able to stand a strong vaccum. Mikuni fuel
    pumps can suck hard to get fuel up to them through clogged filters.

    We need a product that remains stable, resists UV well and lasts at
    least 4 or 5 years without getting brittle enough to crack or break with
    age and vibration. Most get brittle and crack after a year or two.

    My choice is clear Tygothane which is Tygon formulation C-210-A. I
    left some on my plane for over 5 years with no problems and it was still
    as flexible as when new. I finally replaced it only because the additives
    in gasoline had stained it brown on the inside so it was getting hard to
    see air bubbles. Tygothane is sold by Lockwood Aviation, Mark Smiths
    Tri-State Kite Sales and McMaster-Carr sells it as Part #5549K47 for
    1/4ID X 7/16OD. Part #5549K31 for 1/8ID X 1/4OD. They also have
    other sizes.

    A friend has had simular good results for 3 years with Tygon formulation
    F-4040-A but it has a couple of drawbacks. Its tinted yellow so its not
    quite as clear. Its too soft for metal hose clamps or twisted safety wire.
    It doesn't handle vacuum quite as well and its not made in a heavy wall
    size so its not as good for pulse line or pump suction line.
    McMaster-Carr sells it as Part #5552K25 for 1/4ID X 3/8OD and
    #5552K23 fot 1/8ID X 1/4OD.

    Heavy wall tubing should be used for the impulse line and on the suction
    side of the fuel pump or vacuum may cause those lines to collapse.
    The lines on the outlet side of the pump and the vent lines can be a
    thinner wall thickness if you want.

    Suction lines should maintain a steep slope all the way from the fuel
    tank to the fuel pump so route the tubing to avoid haveing high spots
    and low spots. Tiny amounts of water in the fuel can accumulate to
    fill low spots and small air bubbles can accumulate into one very large
    air bubble to fill high spots. A large slug of water or a large air bubble
    can cause problems.

    Automotive type worm gear hose clamps often let air leak into suction
    line connections because the small size we need doesn't form a circle
    very well. McMaster-Carr sells nylon double snap grip clamps which
    work well. Part #9579K63 is typical but get the right size. They also
    sell spring steel wire formed into a circle as "constant tension spring"
    clamps. Part #5324K61 is typical but get the right size. They also sell
    a band tightened by a nut and bolt. Part #5412K48 is typical but get
    the right size.

    If all else fails wrap two turns of safety wire around the tubing and twist
    it tight but don't cut into the tubing.

    There is a lot of discussion about fuel filters. Some Cessna pilot
    "experts" claim that any small stuff which goes through the gasolator
    screens they use is so small that it goes through their fuel pumps, carbs
    and engines with no problem. Obviously that has worked for them for a
    long time but you need to remember the differences in planes and

    Their engines are much larger so they use larger jets in their carbs while
    our smaller jets are easier to clog up. The main problem is that our fuel
    pumps depend on internal flapper valves being able to seal properly up
    to 100 times a second. Grit that gets through screens can keep those
    flapper valves from sealing shut properly. Most of us install a fuel
    just before the fuel goes into the fuel pump to protect the pump and carb.

    Purolator (and others) make a filter with a glass sediment bowl that you
    can take apart to replace the filter and clean out the bowl. It works fine
    on the pump output and there is no problem with them there.
    Unfortunately we need a filter on the pump intake and there is suction
    there. You may have already noticed that suction is harder to seal than
    pressure if you had a hard time keeping air bubbles from leaking into
    your suction line connections. The seal at that filter bowl was NOT
    designed to handle suction and if you try to use it on the suction side of
    fuel pumps it WILL suck air into your fuel system. Many UL pilots have
    known this for years and avoid them but sometimes a newbie will try to
    use one then post that he has a problem with bubbles in the suction line.

    Some internet "experts" claim that filters should not be used on the
    suction side of pumps and use those posts as "proof". You should
    remember that many of the "experts" use wing tanks to gravity feed
    fuel to a lower engine. Their fuel doesn't need to be sucked up to the
    engine so they are not familar with our fuel pumps or the suction needed.
    They claim that the bubbles are "vaporizeing" out of the fuel because a
    high vacuum is needed to suck fuel through a filter.

    It is true that a high vacuum in fuel lines or high temperatures can cause
    "vapor lock" when fuel vaporizes but that is NOT what is happening here.
    The vacuum used normally isn't much more than we generate when we
    suck on a hose to siphon gas and the bubbles are present even when
    the temperature is below freezeing. Its real easy to prove that those
    bubbles are simply air leaking into the suction line. Replace the glass
    bowl filter with any different type of filter and there are no more air
    bubbles in the suction line.

    These same "experts" have claimed that our other filters leak air into
    suction lines. Thats not true. The ONLY reports of air leaks are those
    glass bowl filters and tubing connections which use the wrong clamps.
    I did see one report where vibration unscrewed one brand of so called
    "high performance" fuel filter. They are a metal cylinder which screws
    apart so you can replace the very small filter element. I do NOT
    recommend them because the elements are too small.

    Some fuel filters use a sintered bronze element. That element has a
    very small surface so it doesn't take long for them to get cloged up.
    I do NOT recommend them.

    It's hard to beat the plain old pleated paper type fuel filters which have
    been used in cars, boats, cycles and many other applications for years.
    I highly recommend them. The Fram G1 is large and clear with
    connections that fit our 1/4"ID tubing. Get them from Mark Smiths
    Tri-state Kite Sales or from Lockwood Aviation as part #414-3636 if
    you can't find them locally.

    Some "experts" claim that ethanol in the fuel absobs water and that
    water will clog up paper filters. It is true that ethanol absorbs water but
    neither gasoline, ethanol, water or any combination of them will clog up
    paper filters. Anyone with a paper filter and a squeeze bulb can easily
    suck any or all of it through the filter. Think about the millions of paper
    fuel filters used in cars for years.

    You should trap excess water and trash in the fuel tank before it ever
    gets to the filter anyway. Cessna "experts" should think of our fuel tank
    as our big gascolator where water and trash settle out. We just use a
    filter at our fuel pump intake instead of a screen inside our "gascolator".

    Some "experts" claim that its better to use a gascolator because filters
    will clog up. The reason filters clog up is because they are doing their
    job by keeping stuff out of our pumps and carbs. Rather than clean a
    screen we replace filters. As long as we replace filters when they need
    replacement there is never a problem.

    A squeeze bulb will only pump fuel to refill the carb bowls and lines
    which have drained down while the plane was sitting. It will NOT squirt
    fuel into the intake manifold to help the engine start like a hand pump
    primer. It will NOT enrichen the mixture to help cold engines run
    smoother like a choke. Some people have had so much trouble with
    squeeze bulbs that they refuse to use them. Squeeze bulbs should be
    replaced once a year to minimize problems like splitting, leaking,
    shedding rubber particles into the fuel or failure of their built in check
    valves. I do NOT recommend them.

    Our "choke" is actually just a seperate fuel path inside the carb which
    allows fuel to flow through a seperate jet. That enrichens the mixture to
    help cold engines run smoother but it doesn't "prime" the engine or fill
    the carb bowls and fuel lines. I don't use mine at all.

    A hand primer pump squirts a little fuel into the intake manifold every
    time you pump it. Proper use eliminates any need for a squeeze bulb
    or the choke. It does take a little experience to learn how many times
    to pump it before starting the engine and when to pump it to keep the
    engine running while the carb bowls and fuel lines refill and the engine
    warms up a little. I recommend them highly.

    I mounted my primer near my right shoulder when I'm seated in the
    plane to keep all fuel behind the pilot. That keeps the primer lines
    short and lets me reach across and pump it with my left hand to use
    it as an emergency fuel pump. I can also reach it from outside the
    plane to prime the engine as needed when starting the engine.

    To start my plane I lean in to make sure the throttle is all the way back
    and the kill switches are in the "run" position. I position myself so that
    my left leg is against the front of the right main tire. If the engine were
    to rev up the plane may run over a chock but it can't run up my leg
    before I can kill the engine. I look over the wing to watch fuel move
    through the primer line as I pump the primer. Once it reaches the carb
    I give it a couple more pumps to squirt fuel into the engine. The exact
    number of pumps depends on my past experience with the plane and
    the current temperature. I look to be certain that the area near the
    pusher prop and the area in the prop blast are clear then yell "Clear
    prop". Last I lean in and hit the starter. It may take another pump or two
    to keep the engine running until it warms up. It doesn't take long to learn
    when to pump it.

    I'm a firm believer in KISS (Keep It Simple Stupid) so I won't put one
    on my plane but some people like to have a fuel pressure gauge or a
    light that comes on when fuel pressure drops below 2 PSI. Thats okay
    as long as you understand what you are really seeing.

    You need to see the pressure right at the carb inlet. If you just tee into
    the fuel line there and run a line down to a gauge mounted on the panel
    you will see the head pressure of the fuel in that line added to the actual
    pressure at the carb. You need a 10 PSI gauge but normal gauges are
    not very accurate near the ends of their scales and can not survive
    vibration very long. You have also added the potential problem of fuel
    leaks and fire in the cockpit. Electronic sensors for an EIS or a
    pressure switch for an indicator light installed near the carb inlet solve
    those problems but are they really useful?

    If trash blocks the carb inlet needle valve or the main jet the engine will
    starve for fuel but the light will never even flicker because there will
    be normal pressure at the carb inlet.

    If air is leaking into the pump suction line the pump will pump air bubbles
    into the fuel lines. The light will never even flicker as small bubbles
    through the carb inlet valve and get vented because the pressure in the
    the fuel line stays normal. If there is enough air in the fuel line to
    the pressure in the fuel line then you won't get much advance warning
    from the light before the engine quits.

    The most common problem is crud building up in the fuel filter. How
    fast that happens depends on how much crud is in the fuel and how
    much filter surface area the fuel filter has. Refueling with heavily
    contaminated fuel can clog a small brand new filter very shortly after
    takeoff. Normal fuel usually takes over 100 hours of flying before
    problems ever start. Once the fuel filter can not pass as much fuel as
    the engine is useing the fuel level in the carb bowl starts to drop which
    opens the float needle valve more. The PRESSURE in the fuel line
    starts to drop as the needle valve opens more because the fuel FLOW
    is restricted by the fuel filter instead of the float needle valve.
    the fuel PRESSURE drops below 2 PSI and the light comes on. Notice
    that the engine is still getting some fuel and that fuel FLOW may be
    enough for the engine to run for hours. The light tells you that the fuel
    PRESSURE has dropped below 2 PSI but thats all it can tell you. You
    have no way of knowing why. You have no way of knowing how long the
    engine can continue to run. You need more information before you can
    make a decision about what to do.

    NEVER base a decision to make an emergency landing on an idiot
    light alone. That light should only be used to tell you to check the EGT
    gauge. The EGT will tell you if your engine is getting enough fuel or not
    so base your decisions on the EGT instead of an idiot light.

    Heres why. As previously explained when the fuel system can't deliver
    as much fuel FLOW as the engine is useing the level in the float bowl
    starts dropping. As that level drops the jets deliver less fuel so the
    mixture starts getting lean and the EGT starts to climb. As long as the
    EGT is normal you have no reason to make an emergency landing. If
    the EGT is high you should look for a landing site but also reduce
    throttle to see if the EGT will drop to normal when the engine uses less
    fuel. If the EGT drops to normal you can limp a long way to a better
    landing site at reduced throttle so you don't really need to make an
    emergency landing right away.

    If the float level drops too far the engine will start surgeing. That is a
    short increase in RPM and power when the mixture gets very lean as
    the engine runs out of fuel. Once the mixture gets too lean to ignite the
    engine coasts to a stop unless it gets another shot of fuel to run or
    surge again. The prop windmills for some time after the fuel is gone.
    That keeps the fuel pump working so its common for the engine to
    surge several times before it quits completely. Now you have a real
    emergency but you may still be able to limp to a better landing spot if
    you can use the hand primer to help the fuel system deliver enough
    fuel and/or reduce the throttle so the engine doesn't use as much fuel.

    Most fuel problems show up first at full throttle because the fuel system
    works the hardest then. Get in the habit of checking for high EGT during
    all full throttle operations such as climbout. When you start to see that
    happen, its time to replace your fuel filter and check the rest of your fuel

    The pressure gauge, idiot light or EGT will not give any warning of a
    sudden serious fuel system failure so you should fly like the engine
    could quit at any time and practice emergency landings so you will be
    ready for a real one.

    Fuel injection requires a high pressure fuel pump. Most of those pumps
    need a return line to be run from the pump back to the fuel tank because
    they use a built in pressure relief valve as a form of pressure regulator
    for the outlet port. When the pressure at the outlet port rises higher than
    the set point of the pressure relief valve the pressure relief valve opens
    to divert fuel from the outlet port to the return port until the pressure at
    the outlet port drops back down to the set point.

    That means that the fuel flow into the fuel pump is much greater than the
    fuel flow required by the engine alone. The return line from the pump
    back to the tank and the suction line from the tank to the fuel pump inlet
    port must be big enough to handle the maximum fuel flow that the pump
    can produce. Note that the fuel filter in the suction line must be able to
    handle the larger flow also. The line from the fuel pump outlet port to the
    fuel injection can be much smaller since that flow is only the amount
    actually used by the engine but that line must be able to handle the high
    pressure that is at the fuel pump outlet port.

    You should NEVER attempt the first takeoff until you are absolutely
    certain that your new fuel system will provide enough fuel under all
    conditions. Tie the plane down and run it at full throttle to be certain
    it won't starve for gas during takeoff and check closely for leaks. Always
    be prepared for the engine to quit on takeoff.
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  5. Dave B added a post in a topic EGT Temps   

    Here's another handy one. The link dosen't seem to work, so I'm pasting it here....

    Engine and Prop Adjustments JAN 2010

    Picking the right combination of engine, reduction unit and prop is
    discussed in a different article. This article tells you how to adjust the
    engine and prop correctly after they are installed. Its also a good guide
    to things you should check on a used plane and before you first start a
    new engine.

    A lot of problems can be traced back to inaccurate instruments. It is very
    common for tachs to have large errors. Borrow a Tiny Tach or an optical
    prop tach and compare readings to check your tach over the whole range.
    It is impossible to correctly adjust the prop with a bad tach. Be certain
    that your EGT and CHT gauges read correctly. Useing the wrong type of
    thermocouples or wire for them is a common mistake. It's also real easy
    to enter wrong numbers or settings for electronic displays. See my article
    on thermocouples for more information.

    Check for water or crap in the carb bowls. Make sure carbs are mounted
    square with the engine since a tilted carb can cause one cylinder to run
    hotter than the other on some engines. Cracks in the carb mounting
    sockets can cause lean mixtures so replace them if they are brittle.
    Check for adaquate fuel flow to the carbs. Any time you notice higher
    than normal EGT or if the plane won't reach normal full throttle RPM
    install a new fuel filter before you waste a lot of time looking for other
    problems. See my article on fuel systems for more info.

    Each carb has an idle jet, a needle jet with a jet needle and a main jet.
    All have tiny numbers on them which tell you the size. Check to be sure
    they are the factory recommended jets and the jets are the same in both
    carbs because its common to find that a previous owner has installed
    different jets. The factory recomendations are almost never wrong so
    its very important that the factory jets are used during testing.

    Check that all throttle cables are routed to drain out any water inside the
    cable outer jacket. Water collecting in a low spot can cause corrosion
    or freeze in the winter to lock the cable in one position.

    Pull the throttle all the way back against the lower throttle stop. Where
    the cable enters the top of the carb there is an adjustment that is covered
    by a rubber boot. Slide the rubber boot up the cable to get it out of the
    way then gently pull upwards on the outer jacket of the cable. There
    should be a tiny amount of free movement before you feel the inner cable
    start to move the slide upwards. That tiny amount of free play is critical
    be sure that the cable is not holding the slide up off of the idle speed
    adjustment screw. If you have trouble feeling it you can remove the air
    filter and look inside the carb throat to watch the slide move. Loosen the
    lock nut and turn the adjustment screw until you have that tiny amount of
    free play if needed. Lock the adjustment and work the throttle back and
    forth a few times to be sure the cable outer jacket ends are fully seated
    in their sockets correctly then pull the throttle all the way back against
    lower throttle stop. Double check that the amount of free play is still
    correct at the top of the carb before you reinstall the rubber boot.

    Push the throttle all the way forward against the upper throttle stop and
    look in the carb throat. The slide should go up far enough so that it does
    not block any of the carb throat opening. Its okay if it goes up just a
    extra but if it goes up too much it will bind and put a strain on the
    cable. You should install some sort of upper throttle stop to prevent that.

    Dual carbs must be mechanically matched or one cylinder will have a
    higher EGT than the other and/or you can not get a smooth idle. Pull the
    throttle back against the lower throttle stop. Where the cables enter the
    tops of the carbs there are adjustments that are covered by rubber boots.
    Slide both boots up the cables to get them out of the way. Loosen the
    locknuts and turn both adjusment screws down two turns. That makes
    sure that the cables are not holding the slides up off of the idle speed
    adjusting screws.

    Remove the air filters and use the smooth ends of drill bits as round
    feeler gages to check the clearance between the bottom of the slide and
    the bottom of the carb throat on each carb. Pick a drill bit that will
    slide into the smaller of the two openings and use it to adjust the idle
    speed screws on both carbs until both openings are the same. Your
    carbs are now mechanically matched. To keep them matched you must
    ALWAYS turn the idle speed screw on both carbs the same amount
    when makeing idle speed adjustments. NEVER adjust just one idle
    speed screw.

    Make sure the throttle is pulled all the way back then go back to the cable
    adjusters on top of the carbs. Screw them out to take out ALMOST all of
    the free play. You check that by feeling how much you can lift the outer
    jacket before you feel resistance. It takes a delicate touch but you need
    just a tiny amount of free play to make sure that the slides are not held up
    by the cables when the throttle is pulled all the way back. If the free
    is not the same on both carbs then one slide will start to rise before the
    other so this adjustment is critical. Tighten the locknuts and work the
    throttle back and forth a few times to be sure that all the cable outer
    jacket ends are fully seated in their sockets correctly. Double check
    that the free play is still correct on both carbs then slide the rubber
    over the adjustments. If you have done it correctly both slides will start
    to move upwards at the same time and the bottom of both slides will be
    flush with the top of the carb throat just before you reach full throttle.

    Set the throttle wide open and check that both slides go up far enough
    so that they don't block any of the carb throat openings. Its okay if they
    go up just a little extra but if they go up too much they will bind and put
    a strain on the throttle cables. You should install some sort of upper
    throttle stop to prevent that.

    Because the jet RPM ranges overlap you should make the idle speed
    adjustments first and work up to higher RPMs. If any large adjustments
    are made it will be necessary to repeat the idle adjustment procedure to
    fine tune all adjustments. Make sure a clean air filter is installed before
    makeing adjustments.

    There is an AIR MIXTURE adjustment screw which will fine tune the
    amount of air at idle speeds only. The IDLE SPEED screw limits how
    far the slide can come down to close off the air flow. If you aren't sure
    which screw is which you can see the end of the idle speed screw
    sticking out inside the carb air inlet if you remove the air filter. A
    above the slide pushes the slide down against that screw.

    To prevent engine shake and gearbox chatter our engines need an idle
    speed of around 2000 RPM so warm up the engine and adjust the idle
    speed screw for about 2000 RPM. Remember to turn BOTH idle speed
    screws the same amount to keep the carbs matched if the engine has
    dual carbs.

    Adjust each air mixture screw to get the highest RPM at that idle speed
    setting. 1/8 of a turn on adjustment screws can make a big difference so
    keep the adjustments small. You will have to go back and forth between
    dual carbs a couple of times to get the best possible idle because they

    As the mixture gets better the idle speed will increase so adjust both idle
    speed screws the same amount then fine tune the mixture screws again.
    Keep at it until the engine idles smoothly at the lowest speed which has
    minimum engine shake. Check the cable adjuster on top of both carbs
    after you finish to make sure there is still the same tiny amount of free
    play on each carb.

    Be aware that it's easy to get an arm cut off by the prop and anything you
    drop may go through the prop. I usually tie a short safety rope around my
    waist and the base of the wing spars so that I have to stretch way out to
    reach the adjusting screws. That way I can't forget and move toward the
    prop. Fortunately you won't have to do this again until you notice an idle

    Now you need to know how the factory recommends that your engine be
    used. For Rotax engines download the operators manual at


    The figures used below are for the Rotax 503 so look at page 10-1. If
    you have a different engine you need to change those figures to match
    your engine manufacturers recommendations. If you have a fixed pitch
    prop all you can do is hope that it is the correct prop but all the other
    below will still apply.

    The Rotax manual lists a "takeoff speed" of 6800 RPM for no more than
    5 minutes and a "cruising speed" of 6500 RPM with no time limit.

    Its common practice for aviation engines to have a normal operations
    limit and a higher takeoff limit so what Rotax should have said was "The
    engine can be safely operated at 6800 RPM for five minutes but you
    must reduce the throttle to 6500 RPM or less after that."

    The RPM that a given engine/prop combination can reach is greatly
    influenced by the air speed and any disturbance of the air flow into the
    prop. During discussions you will hear several terms used so you need
    to understand those terms.

    During static testing the plane is tied down. There is no airflow into the
    prop so the engine can not reach full RPM.

    During the actual takeoff the plane does not reach full speed. There is
    reduced airflow into the prop so the engine can not reach full RPM.

    During climbout the plane does not reach full speed. There is still
    reduced airflow into the prop so the engine still can not reach full RPM.
    In addition the use of flaps or even the planes design may block or
    disturb at least part of the airflow into a pusher prop.

    If you set the prop so that the engine turns 6800 RPM during the actual
    takeoff your engine will seriously over rev once you build up more speed
    and/or finish the climbout. To prevent that you should adjust the prop to
    allow 6800 RPM at full throttle during straight and level flight. This
    you the maximum airspeed and keeps your engine below the maximum
    factory recommended RPM during all phases of your flight.

    Rotax describes 6500 RPM as "cruise speed" but if you actually cruise
    at 6500 RPM your engine won't last very long. Its a general rule of thumb
    to cruise at the RPM where your engines power curve produces 75%
    power for best life. For the 503 thats around 5200 RPM.

    Engines are expensive and pilots are cautious so many of them try to
    adjust their prop to give lower full throttle RPMs thinking that will be
    easier on the engine. That actually works an engine harder because
    the prop becomes a bigger load than the engine was designed to
    handle. The ignition timing, port timing and carbs are all designed to
    work best with the engine loaded just enough to reach the max full
    throttle RPM specified by the manufacturer. If you really want to be
    easier on your engine simply give it less throttle after the prop has
    been adjusted correctly. Loading the engine down so it can't reach
    the maximum RPM at full throttle is called "over prop" or "lugging".
    It puts an extra strain on all engine and reduction unit moving parts
    which will shorten their life.

    The first step is to adjust the prop to a pitch where you will have a safe
    first test flight. We know that the prop load will be reduced once air is
    flowing into the prop at high speeds so the engine will turn faster in
    The amount depends on the type of prop, diameter, pitch, etc. To
    prevent exceeding the max RPM in the air we need to first adjust the
    prop for about 6300 RPM at full throttle while the plane is tied down.
    The exact final adjustment will be determined by flight tests later.

    Tie the plane down and monitor the EGT and CHT temperatures as you
    slowly apply throttle. If the RPMs exceed 6300 before you reach full
    throttle, stop and add more pitch to the prop. If you reach full throttle
    RPMs stay below 6300 stop and reduce pitch on the prop. If the EGT
    exceeds 1150 stop and find out why before continuing tests. If the CHT
    exceeds 430 stop and let the engine cool down before continuing tests.
    Maybe you need to think about adding some more cooling capacity.
    Note that the operators manual lists maximum EGT as 1200 and
    maximum CHT as 480 on page 10-1 but we want to stay below those
    figures during our early tests.

    This is also a good time to watch for surprises like leaks, fuel starvation,
    and overheating problems. It's better to find them now than find them in
    the air.

    Prop adjustments and carb adjustments will affect each other so read
    this whole section before any test flights and make all the adjustments
    in the sequence given below.

    During the first phase of first test flights the pilot needs to determine
    full throttle engine RPM that is reached during straight and level flight.
    should also monitor EGT and CHT closely the entire flight because they
    may try to exceed the maximum allowed until the plane has been fully
    checked out and the prop is correctly adjusted. After each flight make
    small adjustments on the prop until the engine turns very near 6800 RPM
    at full throttle during straight and level flight.

    During the second phase of flight tests the pilot needs to check the
    needle jet and jet needle operation by flying for a couple of minutes at
    each of several engine speeds between about 3000 RPM and 5500 RPM.
    There will be variations but all EGT readings must be in the normal range.
    If most of those engine speeds show a high EGT try moving the clip
    down on the needle to provide more fuel for the whole mid range.
    Repeat test flights until you find the clip position which works best over
    the whole mid range.

    You may find a small range of engine speeds which have a high EGT
    while all the other mid range speeds are normal. Avoid running in that
    small range of engine speeds until all other adjustments are completed.
    An incorrect prop or prop adjustment is almost always the reason.

    During the third phase of flight tests the pilot needs to check the main
    jet operation by watching the EGT during full throttle operation in straight
    and level flight. If the EGT gets too high reduce throttle until it cools
    down. You MAY need a larger main jet but if the engine could not turn
    near 6800 RPM during the test the real problem was the prop pitch.
    Adjust the prop and try another test flight.

    You may have to tinker a little more with the needle clip to get the EGT
    correct over the entire mid range after you have fine tuned your prop.
    That may mean some minor compromises but try to keep the EGT as
    close to ideal as possible over the most used RPM ranges. Double
    check that the final adjustments will not let the EGT run above 1150 or
    below 1000 at any RPM.

    Remember that air temperature and altitude will have an effect too. I
    have to adjust my needle one notch every spring and fall to keep mine
    set correctly but four thousand feet of altitude change doesn't change
    my EGT enough to matter.

    There are four paths fuel can follow to get through the carb. The first is
    the choke. Our choke is not an air flow restriction like on cars. Our
    is a manual "on" or "off" lever which opens a path for a tiny amount of
    extra fuel to flow into the throat of the carb to enrichen the mixture for
    better starting. Always turn it off after the engine warms up enough to run

    There is some interaction and overlap between the three main fuel paths
    but generally speaking, the IDLE JET will control all of the fuel flow at
    speeds. The JET NEEDLE is attached to the carb slide and it moves
    into and out of the NEEDLE JET. That combination controls almost all
    of the fuel flow in the lower midrange, most of the fuel flow in the upper
    midrange and some of the fuel flow above that. The MAIN JET provides
    the additional fuel needed from the upper midrange to full throttle.

    Way too often people jump in and start changeing jets attempting to cure
    some problem that isn't really caused by the jets at all. The factory isn't
    stupid ... they choose the jet sizes for a good reason and it is very rare
    for them to be wrong. Before you even think about any jet changes you
    should double check that the prop is adjusted as described above to
    provide the correct load on the engine. Maybe your tach reads wrong.

    Many jet changes are done by misguided people attempting to get more
    speed by adding pitch to the prop. You might get away with a little bit of
    extra pitch but if you get weird EGT temperatures or weird fluxuations in
    RPM in a narrow RPM range you have gone too far with it and jet changes
    won't help much because the engine is overloaded.

    If you were able to get a significant speed increase with too much pitch
    you will be much better off to use a slightly shorter prop with that pitch
    your engine can reach the correct RPM.

    Some other things to keep in mind before you tinker with jets.

    IDLE JET If you were ever able to correctly adjust the idle mixture then
    there is no reason at all to change the jet size. Blow the trash out of it
    replace it with the same size.

    NEEDLE JET If the midrange EGT temperatures were ever correct
    there is no reason at all to change the jet size. It might have the hole
    enlarged from wear against the jet needle. Blow the trash out of it or
    replace it with the same size.

    JET NEEDLE If the midrange EGT temperatures were ever correct
    there is no reason at all to change the needle size. It might get bent, it
    might get worn in the taper area, it might get worn in the clip grooves on
    top or the clip may need adjusting. Replace it with the same size.

    NEEDLE CLIP If the mid range EGT temperatures were ever correct
    the most it will need is adjustment one notch up or down to allow for
    seasonal changes in air density.

    MAIN JET If the full throttle EGT temperatures were ever correct there
    is no reason at all to change the jet size. Blow the trash out of it or
    replace it with the same size.

    Go over all the adjustments above because parts wear together and
    cables stretch during their early life. After you get the engine broken in
    good it will produce more power and that might mean changes.

    After you are more familar with the plane you might consider this trick.
    The prop is still producing a certain amount of thrust at idle speed. That
    means more "float" distance and longer roll outs which can really matter
    in short field landings. After correct adjustment as described above I
    back the idle speed screw out a little for a very slow idle. I use a little
    of throttle to bring the engine speed back up so the engine doesn't shake.
    On final I can pull the throttle all the way back for a steeper but slower
    glide. The forward speed of the plane helps the prop windmill fast
    enough to prevent engine shake and the prop has a large amount of drag
    instead of a small amount of thrust. As the plane slows down on rollout
    I add just enough throttle to prevent engine shake. It can make a big
    difference in short field landings and more experienced pilots may prefer
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  6. Dave B added a post in a topic EGT Temps   

    Great! So where do you post all these archived jewels so we can find them later?

    Glad this one is of use.

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  7. Dave B added a post in a topic EGT Temps   

    This article may help....


    Tuning the 2 stroke.

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  8. Dave B added a post in a topic N844RS repair   

    Me Too!!

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  9. Dave B added a post in a topic G loading for MkIV Flyer   

    Good, honest explanation of the 'system' we work with!
    Thank you!

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  10. Dave B added a post in a topic Heading for New Home   

    Looks great!

    Is there enough space around the air filter to keep it from contacting the cowl during vibs and max power? Check for dents around the filter. Really bad for the carb mounts.

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  11. Dave B added a topic in Avidfoxflyers General Hangar   

    Parking Brake Valve find
    Just wanted to share a find on eBay for a parking brake valve....


    Only 7 left. Specs and parts available on the Cleveland site. 60-15a.

    DaveCleveland-Parking-Brake-Valve A.pdfCleveland-Parking-Brake-Valve.pdf
    • 1 reply
  12. Dave B added a post in a topic Maybe Spring   

    Glad to bring it up, Randy. Just trying to head off a problem. A friends P40 had the same issue, and we're having to replace those 'expensive' boots, and trim out more.

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  13. Dave B added a post in a topic Maybe Spring   

    Hi Randy.
    That's nicely done, and looks good. But I'd like to indicate a possible problem with the fit of the cowl around the air filter.

    During your test runs, up to full power, watch for creasing on the top and bottom of the filter, caused by the cowl and rocking of the engine in it's mounts. This will lead to cracking of the carb boots, which is really bad for the engine. This rocking contact with the cowl may be especially noticeable with a rough idle.

    More trimming might be necessary.

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  14. Dave B added a post in a topic request performance information   

    Any chance you could carefully rename the 2nd page (middle) to allow download it as a jpg file? Page 1 and 3 download fine, but pg 2 comes up as 'index' and won't download.


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  15. Dave B added a post in a topic Avid Construction Manual   

    ADs still not downloading correctly. A possibility..... Only use letters in the file name, ie: ADs instead of AD/s or AD's.

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