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Thread: Cessna 305A Birddog

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    Cessna 305A Birddog

    Does anybody have a opinion on the use of the electric fuel pump in the Cessna Bird Dog for Take offs and Landings? My ship tends to run a little rough with the boost pump on while on the ground- I prefer not to use it for landings.
    Thanks!

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    mvivion's Avatar
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    Quote Originally Posted by Skytrucker View Post
    Does anybody have a opinion on the use of the electric fuel pump in the Cessna Bird Dog for Take offs and Landings? My ship tends to run a little rough with the boost pump on while on the ground- I prefer not to use it for landings.
    Thanks!
    Why is it equipped with an electric fuel pump? In most cases, itís because if your engine driven pump were to fail at a critical time, the electric backup pump might save your airplane and maybe your life. In these cases, the gravity feed may not be sufficient to produce full power if the engine driven pump were to fail. And, on takeoff, things get mighty busy if the engine rolls back....how fast can you find that switch?

    So, electric pump on for takeoff and landing. The takeoff part is obvious. The landing? What if that landing approach turns into a go around?

    Im not familiar with a Bird Dogs systems, so take this for what itís worth.

    But, if it runs rough on the ground, turn the pump off while on the ground...or does the operators manual call for it to be on during ground ops?

    MTV

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    wireweinie's Avatar
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    Quote Originally Posted by mvivion View Post
    Why is it equipped with an electric fuel pump?

    MTV
    Original military equipment.

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    Life's tough . . . wear a cup.

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    In all the time I flew L19s towing signs, the only thing I used the boost pump for was to prime it. Never used it on TO or landing.


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    skywagon8a's Avatar
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    Quote Originally Posted by Skytrucker View Post
    Does anybody have a opinion on the use of the electric fuel pump in the Cessna Bird Dog for Take offs and Landings? My ship tends to run a little rough with the boost pump on while on the ground- I prefer not to use it for landings.
    Thanks!
    Is this a two speed pump or just on/off? The Cessna 185 has a two speed pump which is used only for starting and during engine failure emergencies. It is not used for normal take offs.
    The reason your's is running rough with the pump on is because the extra pressure is enriching the mixture. I left the pump on low once after starting in the 185 while I was out in the boonies where it would have been impossible to walk home. When I took off the pump shifted to high (throttle position switch), the engine ran so rough it scared me. I never left the pump on again.
    N1PA
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    mvivion's Avatar
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    Quote Originally Posted by wireweinie View Post
    Original military equipment.

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    moist, so why did Cessna and the military feel a pump was necessary?

    MTV
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    skywagon8a's Avatar
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    Mike,
    Rated fuel flow must be satisfactory during the most adverse attitude with minimum fuel on board. It is likely that without a pump being installed there would be insufficient fuel flow.
    N1PA

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    You need the pump to prime it. The L19 (305) has a PS5 pressure carburetor and needs fuel pressure to work. Without the boost pump, no fuel gets to the engine. Iíve seen check lists that say use the electric pump for take off, and Iíve seen ones that say leave it off for take off.

    It is equipped with a pressure regulator, bypass valve and relief valve. Maybe the OP has the pressure regulator set to high. Should be about 12 psi if I remember correctly.

    Main reason we never used them on the banner planes was that the drive seal was bad and it would leak fuel out the drain when the electric pump was on. Maintenance on banner planes always leaves a lot to be desired.


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    skywagon8a's Avatar
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    Quote Originally Posted by dgapilot View Post
    You need the pump to prime it. The L19 (305) has a PS5 pressure carburetor and needs fuel pressure to work. Without the boost pump, no fuel gets to the engine.
    That explains a lot. The PS-5 pressure carburetor requires a fuel pump to provide inlet pressure for proper operation. This means the engine will have a driven pump which in turn calls for a standby pump which in this case is also used to supply starting pressure.
    N1PA

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    WhiskeyMike's Avatar
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    I have a Bird Dog and have been double checking all the PS5C and fuel pressure info. The pressure should be the same with or without it on, pretty much. The manual say use it. If it makes it run rough, then the pressure is too high or the mixture is set wrong - or the diaphragm is about to fail and it will all go quiet. You can download the PS5C manual online and it is full of good info. For example, you must let the carb sit full of gas for 24 hours before it will operate properly, and you must check the mixture with the pump on. There are 2 mixture adjustments - for idle and cruise ops. They say the PS5C is sensitive to altitude and temperature changes, so if it got cold lately.... PS I operated 5 banner tow and Skywriting Bird Dogs out of Lawrence MA. Did you ever fly with us?
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    mvivion's Avatar
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    Quote Originally Posted by skywagon8a View Post
    That explains a lot. The PS-5 pressure carburetor requires a fuel pump to provide inlet pressure for proper operation. This means the engine will have a driven pump which in turn calls for a standby pump which in this case is also used to supply starting pressure.
    And that would suggest that the electric pump needs to be on for takeoff and landing, in case the engine driven pump fails, not just for prime to start.

    MTV

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    WhiskeyMike's Avatar
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    Quote Originally Posted by mvivion View Post
    And that would suggest that the electric pump needs to be on for takeoff and landing, in case the engine driven pump fails, not just for prime to start.

    MTV
    Yup, I forgot to add that. Same as a Cherokee or anything else with engine and aux electric pump - not to be confused with high pressure setting on O-520 injected engines.

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    Quote Originally Posted by WhiskeyMike View Post
    I have a Bird Dog and have been double checking all the PS5C and fuel pressure info. The pressure should be the same with or without it on, pretty much. The manual say use it. If it makes it run rough, then the pressure is too high or the mixture is set wrong - or the diaphragm is about to fail and it will all go quiet. You can download the PS5C manual online and it is full of good info. For example, you must let the carb sit full of gas for 24 hours before it will operate properly, and you must check the mixture with the pump on. There are 2 mixture adjustments - for idle and cruise ops. They say the PS5C is sensitive to altitude and temperature changes, so if it got cold lately.... PS I operated 5 banner tow and Skywriting Bird Dogs out of Lawrence MA. Did you ever fly with us?
    No, flew down in NJ for Aerial ADs and a couple other companies. That was back in the 1980s when I was young and foolish!


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    WhiskeyMike is right on with the operation compared with IO-520's. Pump is to be run for takeoff and landing and anytime you are below about 1000 ft. Its really only needed if the engine pumps fails,so if your lucky??
    Also if you do have much trouble with the stock system Air Repair has an STC to convert to an all gravity system.

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    BC12D-4-85's Avatar
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    FM: https://www.aeroclubprealpivenete.it...9-Bird-Dog.pdf

    Read about the fuel system. My first instructor in Fairbanks flew them in SE Asia.

    Gary

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    WhiskeyMike's Avatar
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    There's lot of talk about diaphragm failure, and recently one L-19 went in the trees - I think near East Texas/Arkansas border. Despite all that, the word on-line is that the PS5-C is used on a lot of engines like early Bonanzas and is highly reliable. Sometimes they idle rough, but all in all, I think they work better than MA-4-5's on big bore Continentals. And there is zero carb ice with this sort of "central fuel injection." For my money they run better, smoother, more powerful and economical. That said, you have to look after both an engine driven and an electrical pump. If you consider the AD's and SB's on MA-4/5 etc over the last few years, venturis, floats etc. I think it's about even for cost and reliability. You also have the option of Stevie Noyes' conversion to Lycoming O-540/250HP with three blade prop. Nothing's for free. Thank you moderator for putting up with this thread on superb.org. Its rainy and windy in Massachusetts, and I won't see my Bird Dog until next week in Texas. I confess I like it much better than my Huskies, even though it is slower, not as zippy etc, but neither one of them will ever be a light PA-18 - King of the skies. There's only one "best."
    Last edited by WhiskeyMike; 10-31-2019 at 03:04 PM.
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    Thank you to everybody who posted a reply to this thread! I could not imagine better! I ran the 305 up to-day before the wx moved in , and determined that it must be a error in the fuel pressure gauge, and the electric pump was set too high. There is more to tell ,but it will have to wait till I get done fixing her.
    You all are great,Thanks
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    aktango58's Avatar
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    Quote Originally Posted by WhiskeyMike View Post
    Yup, Same as a Cherokee or anything else with engine and aux electric pump
    Well, not exactly.

    This is why it it important to read your POH.

    Example: my Maule requires both engine driven gear pump and electric fuel pump to be installed and working. The only time you need to have the electric pump on is an emergency.

    185 we would use it to prime, as with 206. But most high wing birds I have flown the electric pump is an emergency pump, and don't turn it on for take off and landing. Cherokees are another story
    I don't know where you've been me lad, but I see you won first Prize!

  19. #19
    mvivion's Avatar
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    Quote Originally Posted by aktango58 View Post
    Well, not exactly.

    This is why it it important to read your POH.

    Example: my Maule requires both engine driven gear pump and electric fuel pump to be installed and working. The only time you need to have the electric pump on is an emergency.

    185 we would use it to prime, as with 206. But most high wing birds I have flown the electric pump is an emergency pump, and don't turn it on for take off and landing. Cherokees are another story
    Well, you’re right about consulting your POH or Flight Manual Supplement. Many if not most early Cessnas (170, 172, 175) with O-360 conversions are equipped with engine driven and electric pumps. In those aircraft, the fuel lines from fuel selector to gascolator is of a diameter that gravity won’t provide sufficient fuel to run the engine at full lope.

    So, electric pump on for takeoff and landing. Some of these aircraft have been modified with larger diameter line and both pumps removed by field approval.

    But, read the fine print for YOUR installation.

    MTV

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    WhiskeyMike's Avatar
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    AKTango58. ""Well not exactly." Point taken. Yes, of course, I didn't mean to mislead the least informed among us. It was a general comment, and I retract it. Your mileage may vary. Read your POH, and by the way, make certain it is the CORRECT POH and up to date in case the plane has been modified. For example. I took and old Citabria in trade for a Stearman and left Ohio headed for Allentown, Queen City PA. The POH said 36 (+/-) gallons total. Pretty much regulation Citabria tanks, but I got suspicious as the sun went down and the gauges too. Something reminded me of old Champion CItabrias having more like 24 gallons, even though the POH in the plane said 36 (+/-). By now it was really dark and I was getting really concerned. By good fortune, the lights went on at a strip beneath me, and I immediately, entered the pattern and landed. Next morning I triple checked and yup, small tanks with fumes left. That'll remind you to "trust but verify."

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