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Thread: C90 in a PA-17 Vag

  1. #11

    Default Re: C90 in a PA-17 Vag

    Quote Originally Posted by d.grimm View Post
    There is formula in the FAR's that specifies fuel flow
    in relation to horsepower. The FAA inspector had to watch
    while I did the test for my fuel tank Field Approval. Mine flowed
    Enough for 160 HP.
    I thought it had to do with a certain endurance, not fuel flow. As I say I don't have a ref.

  2. #12

    Default Re: C90 in a PA-17 Vag

    I see where you are going with that now. As I remember
    the 0-200 STC for the J-3 from Univair requires a wing tank
    with 6 gallons of the nose tank considered unusable.
    The high angle of attack it can achieve doesn't give the required
    head pressure at high angles of attack. I can see the same thing happening
    in a high powered Vagabond with only a nose tank.
    When I did my fuel flow test I asked if it had to be at the
    Stall attitude, they didn't require it, maybe because the flow rate was so high.

  3. #13

    Default Re: C90 in a PA-17 Vag

    For gravity feed fuel systems the minimum head is usually described in inches rather than a specific pressure. The TCDS for the C85 states a ridiculous 19 inches when using a Stromberg carburetor. As I recall the C90 powered PA-18 Vagabond prototype did have a PA-16 wing installed with the 18 gallon fuel tank.

  4. #14

    Join Date
    Dec 2007
    Upstate New York

    Default Re: C90 in a PA-17 Vag

    Goodness, Brett. Where do you get some of this stuff? "Back in the Day", there was a whole crop of "Aviation Journalists" that made stuff up, and propagated all KINDS of "inverted" (inVENTed?) rumors to make themselves APPEAR "in the know" to Joe Public. A "C-90 powered PA-18 Vagabond prototype"??? Huh? Don't just read something and "believe it", necessarily. There's TONS of "incorrect information" in the writings of even the most revered Writers of the Day. This continues into the present! Pick up any copy of "Piper Owner"... and you'll find SOMETHING that just "isn't right" (Gilbert will testify...there's a couple Bloopers in the article about The Red Lady) Why, some people even believe that there is a Piper Drawing to put the A-65 Drawing on the PA-15. No there wasn't...The PA-15 with a Continental was a PA-17! Also...The "twin engined PA-22"... was a JOKE, son!

    Oh, and... you said "For gravity feed fuel systems the minimum head is usually described in inches rather than a specific pressure." Gosh! you mean "inches" [of mercury, or water. or Jello] isn't a finite unit of measure!?! It isn't a "specific pressure", you say??? It most certainly IS, My Friend. It's "fractional", when compared to PSIG (and another thing...saying "pounds" may mean something "specific" to YOU, but are you meaning "how much the 'pounds' of air in your tire WEIGHS? You are mixing metaphors unless you "specify" what pounds you mean. The air in a tire is PRESUMED to mean "pounds per square inch, gauge" but it DOES have an actual "weight by volume", as well -but WHO CARES? Its unsprung weight anyway). Oh yeah..."inches" (if you specify "of WHAT") is a valid measurement of PRESSURE. "Head". That's SHORT FOR "head PRESSURE". Inches (or something) is used when you are dealing with smaller amounts than you can practically READ on a "pounds gauge". How would you READ "1/28 of a pound per square inch, gauge" on a hundred pound "pressure" gauge? or a ten pound gauge. MOST of the English speaking World would be reading "inches", or some other "scale" (OF SPECIFIC PRESSURE) that might be "relevant" to the reading in question... like "atmospheres", "Fnewtons" or maybe "Henweighs". In fact, "they" MAKE "gauges" that directly read in "inches" (specify "of what" HERE). Then let us not forget that one of the FIRST "measuring devices ever inverted by those that wanted to be "precise" was...the "manometer"! Know what THAT "read pressure in" ? (ans. yep... INCHES (of water). Of course, in order to actually be able to USE that "reading", you had to correct for Standard Atmospheric Conditions, or your reading would be different than the same reading in Tibet.

  5. #15

    Default Re: C90 in a PA-17 Vag


    The C90 powered PA-18 Vagabond information is from Clyde Smith, Jr. and Roger Pepperell. I have discussed this subject with both of them at length. The "prototype" I refer to (and perhaps prototype is not the right word) is NX4526H, s/n 15-304 on which Piper installed a C90-8 engine on August 17, 1948. This aircraft was destroyed on March 3, 1949 when it got away after being hand propped, ran into a telephone pole and a transformer fell on it. Some of the factory records indicate this was being developed as the model number PA-18, which was used for the Super Cub after the C90 powered Vagabond project was abandoned. I believe Clyde is now a Vintage DER for fabric Pipers and I highly recommend speaking with him concerning approval for a C90 installation on the Vagabond.

    As far as "inches", I presume the figures given for minimum head on the Type Certificate Data Sheets for the A and C series Continental Engines (WHICH specifically state INCHES when referring to gravity system) are the minimum differences between the height of the lowest fuel level in the fuel tank, and the height of the float level in the carburetor, at some given aircraft attitude (aircraft leveled, or maximum pitch?). Of course this will RESULT in a specific fuel pressure when the float valve is closed, but this specific minimum pressure is not given in the TCDS for gravity fuel systems. A specific MAXIMUM pressure is given. I don't believe the "head - inches minimum" is referring to measuring pressure in inches of a liquid (of mercury, or water. or Jello... JELLO????) in a liquid column instrument like a manometer or barometer.

    "The actual pressure available from a gravity feed system is about one PSI for each forty inches of head of fuel (as measured in distance from the surface of the fuel in the tank to the point of discharge into the carburetor)." From:http://www.kellyaerospace.com/articl...essory_AMT.pdf
    Last edited by BrettL; 02-20-2012 at 02:16 PM.

  6. #16

    Default Re: C90 in a PA-17 Vag

    Additionally the PA-18 Vagabond was planned to have a 1325 lb gross weight. Reading my notes, I think the PA-16 wing installation was either planned for the PA-18 Vagabond, or we were speculating at some point that NX4526H might have had wing serial numbers 16-3-L and -R, but I found a note from Clyde that his records shows wings 15-302-L and 15-304-R. So no wing fuel tank, unless there was some change made at the time the C90 was installed that was not recorded in the records Clyde has.

  7. #17

    Default Re: C90 in a PA-17 Vag

    This is great stuff and I always had heard of the "PA18". Do you know if any records exist or better yet engineering drawings? This might make a 1320 lb Vagabond a slam dunk. Terry Bowden, Vintage DER is currently working on
    a 0-200 installation in a Vagabond and I shared a couple one time STC's with him. I'll pull up the records on N4526H and see what's interesting there.

  8. #18

    Default Re: C90 in a PA-17 Vag


    I believe Roger Pepperell found and published one engineering drawing for the PA-18 Vagabond in his book. I don't remember any details of it other than it was the fuselage (perhaps stress analysis?). I doubt that the PA-18 Vagabond data would be of any value in substantiating field modifications or STCs as it was never certified, and the testing with the C90 was done completely under experimental airworthiness. I recommend you contact Clyde Smith, Jr. as he is the source for most of this information. He is also the person to talk to about the gross weight increase, as well as the engine installation approvals.

    I'd love to have a copy of N4526H - 15-304's records too. I had intended to order them at Oshkosh last summer (where you can get them for free), but I forgot to take the info with me. Please let me know if you find anything referencing PA-18 or an 18- serial number in those records, or if I could get a copy of them from you (split the cost?).

    Last edited by BrettL; 02-20-2012 at 11:56 AM.

  9. #19

    Default Re: C90 in a PA-17 Vag

    Quote Originally Posted by JohnW View Post
    Why, some people even believe that there is a Piper Drawing to put the A-65 Drawing on the PA-15. No there wasn't...The PA-15 with a Continental was a PA-17!
    Drawing 11530 "PA-15 Complete Airplane". Probably because Piper internally considered the PA-15 and PA-17 the same airplane model as evidenced by all the fuselage and wing numbers being "15-" whether they were used for a -15 or -17. I don't think you'll ever find a fuselage or wing with a "17-" number on it. The "POWER PLANT (CONTINENTAL ENGINE)11828" was added to drawing 11530 as revision C on 5-3-48 by "J.C.B.". Drawing 11830 "PA-17 Complete Airplane" was completed on 4-30-48 by "J.C.B." and checked by "H.R.K." on 5-3-48. Draw your own conclusions.

    However, you are correct in stating that a PA-15 with a Continental A65 is a PA-17, as despite revision C to drawing 11530, the Continental A65 is not approved on type certificate A-800 for the PA-15.
    Attached Images Attached Images
    Last edited by BrettL; 02-20-2012 at 02:07 PM.

  10. #20

    Default Re: C90 in a PA-17 Vag

    Quote Originally Posted by JohnW View Post
    Also...The "twin engined PA-22"... was a JOKE, son!
    Is this the JOKE you're referring to?: http://1000aircraftphotos.com/Contri...David/8788.htm

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