"You are... what you are." Aeronca 11AC Chief

Discussion in 'Home Builders and Sport Pilots' started by Lois, Jan 13, 2022.

  1. Lois

    Lois Filing Flight Plan

    Joined:
    Jan 7, 2022
    Messages:
    28

    Display name:
    Lois
    Any 11AC owners out there?

    “You are what your record says you are.” –Bill Parcells

    If true, I suppose a corollary is that if you have Poly Fiber covered wings, you are what your “CAA Approved Airplane Flight Manual” says you are. Once you have everything tuned up and rigged correctly there probably isn’t a whole lot of room for “improvement.”*

    A friend bought a 1946 Aeronca 11AC “Chief”-- well, most of one. It flunked the test in AD 2000-25-02 (spars) rather badly.

    “Probable Cause: The pilot's inadequate preflight planning, which resulted in a takeoff over maximum gross weight from a turf runway of insufficient length in high density altitude conditions, the airplane’s resulting inability to attain a climb rate, and subsequent collision with trees.” Read the official report.

    New wings were built and fitted, and “Chef’s” (inside joke) new weight is 787 lbs. balancing at (+14.92). It’s A-65-8 is ~ 750 hours SMOH. It spins a Sensenich w72ck42. Compression reads 71 to 77. It has the six original gauges / instruments so readings had to be estimated, they were plotted on a spreadsheet and “smoothed” into a curve.

    Taking off from asphalt, 760 ft AMSL, 10 to 30*F , at 1250 lbs., informal test flights were conducted at altitudes between 3,000 and 6,000 feet into a < 10 mph wind, with numbers crunched to give true airspeed on a standard day.

    11AC 1250 lbs.
    A-65-8 (max rpm 2300)
    W72CK-42 (max rpm 2300)
    Rate of Climb ~ 400 fpm (at S.L. losing about 1% per 450 ft)
    2300 ~ 2285 actual rpm gives ~ 90 mph burning ~ 4.9 gallons per hour at 3000 ft
    2150 ~ 2135 actual rpm gives ~ 80 mph burning ~ 3.7 gallons per hour at 3000 ft
    2000 ~ 1985 actual rpm gives ~ 70 mph burning ~ 3.0 gallons per hour at 3000 ft

    * So, I weigh 135-ish, and I could easily fly this with my sister, daughter, or best friend (it’s not real wide) local and be well under gross. Or fly it at gross choosing between full baggage and half the aux tank or some baggage and 23 gallons. But if two linebackers want to buy a plane… Nope, especially if they need to lug their gym-bags.
     
  2. Lowflynjack

    Lowflynjack En-Route

    Joined:
    Oct 28, 2014
    Messages:
    3,221

    Display name:
    Jack Fleetwood
    I never owned one, but flew one for a few years. It was a lot of fun. It cruised at 85mph and that was it. It did have the upgrade to 75hp. I loved slipping that plane to land... so much fun. Hand-propping it could be easy or it could be a challenge, depending on what mood it was in. The original wood-look paint on the panels is one of the best parts.

    [​IMG]

    [​IMG]
    [​IMG]
     
    Lois and Terry M - 3CK (Chicago) like this.
  3. Lois

    Lois Filing Flight Plan

    Joined:
    Jan 7, 2022
    Messages:
    28

    Display name:
    Lois
    LOL, thanks for the photos. Other than the "smiley face" and tablet holder, it's exactly the same interior. The exterior is red and white but in exactly the same scheme down to the accents on the wheel fairings.

    In 2022, the difference between an A-65 and an A-75 is minimal. Maybe nothing more than bigger carburetor jets to spin a 2" shorter prop 300 rpm faster. (The Continental Rebuild Manual shows the two power curves superimposed up to 2300 rpm, the A-75 just "goes to '11'... well, it is one more isn't it?"*) CM stopped making A-65 parts eighty years ago. Unless you have original or very NOS, the O-170-3 / A-75 parts have the extra oil passages and newer style rings.

    It's a time machine, a beautiful example of exactly what it is. (JMO)

    *Gratuitous 'This is Spinal Tap' reference.
     
  4. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    8,255

    Display name:
    Dan Thomas
    IIRAc, the carb venturi was also slightly larger to pass more air.

    The engine was built until 1966. My A-65 is a 1946 model, 76 years old this year. CMI could hardly have discontinued parts for it 80 years ago. It was first built in 1938, 84 years ago.

    But parts are scarce and expensive. 1966 is still a long time ago.
     
  5. Lois

    Lois Filing Flight Plan

    Joined:
    Jan 7, 2022
    Messages:
    28

    Display name:
    Lois
    You are correct, the venturi is removable... Which gets us here...
    The A-65 was made until 1966... But in 1941 when it was standardized as the Army's O-170-3 a number of improvements to the internals were made. More drillings for oil passage, a different piston ring arrangement, different bearings. All of which could be easily retrofit into 1938-42 production engines. Once Aeronca, Piper, Taylorcraft, and the Army itself started buying O-170-3s in mass quantities, Continental stopped making those parts particular to the "original" civilian A-65.

    The O-170-3 is an "improved" A-65 not an A-75, but since all the new parts made since 1942 have been made to the O-170-3 / A-75 specs, an A-65 probably already has A-75 internals, it just isn't set up to run at 2600 rpm.
     
  6. Tools

    Tools Line Up and Wait

    Joined:
    Aug 6, 2020
    Messages:
    524

    Display name:
    Tools
    I got one, mostly restored. Hope to resume work in the next six months.

    everything is completely redone and covered, up through poly brush. metal stripped and ready for paint. Haven’t touched the doors, nose bowl, wheel pants or seat yet.

    Looking forward to flying one!
     
  7. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    8,255

    Display name:
    Dan Thomas
    Sometimes the only difference is the prop, pitched lower and sometimes of smaller diameter to let the engine rev up to the new redline, thereby raising the HP.

    When the Cessna 172R came out in 1996, the IO-360 was limited to 160 HP. It quickly became obvious that 160 HP wasn't going to cut it for the increased gross weight, so Cessna got approval to issue a new prop, new tach (new markings), and an AFM revision to spin the engine up to 180 HP.
     
  8. Lois

    Lois Filing Flight Plan

    Joined:
    Jan 7, 2022
    Messages:
    28

    Display name:
    Lois
    True. FWIW Sensenich's 'Wooden Propeller Application Guide' lists the same x42 (std) and x44 (cruise) pitch for the A-65 (72" dia) and A-75 (70" dia).
     
  9. Pilawt

    Pilawt Final Approach

    Joined:
    Sep 19, 2005
    Messages:
    8,776

    Display name:
    Pilawt
    That's something like what Piper did with the early Cherokee 140. They were building a full four-seat Cherokee 150 at the time, so to put the new two-seat trainer model a peg lower in the catalog (despite the same engine and nearly the same airframe) they limited the O-320 to 2450 rpm (140 hp), instead of the 150's 2700 rpm/150 hp, and MGW was reduced to 1950 lb. After only a year the 140's prop was repitched and the redline moved back up to 2700 rpm, and MGW increased to match the PA-28-150's 2150 lb, all to accommodate the new, optional snap-in rear seats ("2+2 Cruiser" option).
     
  10. DFH65

    DFH65 Pattern Altitude

    Joined:
    Jun 29, 2013
    Messages:
    2,396

    Display name:
    DFH65
    Did my TW training in an 11CC almost bought that airplane. I am a bigger guy instructor wasn't small we never had full fuel onboard. The 85 makes the Chief and the Champ respectable performers. 65 horses is just barely enough to fly. The Champ I fly now has a 65 and in the summer I am usually glad we have a 5000 foot grass runway. :)
     
  11. skyking3286

    skyking3286 Pre-takeoff checklist

    Joined:
    Sep 29, 2012
    Messages:
    179

    Display name:
    skyking3286
    2009 10-10 Flt Chief at Sunset with Glastar waiting_.JPG

    Present owner since 1989. . . Prop size Sensenich recommends is the climb prop. Cruise doesn't really gain anything and with 65 horsepower you need the climb help.
     
    Last edited: Jan 15, 2022
    SkyDog58, Daleandee and Lois like this.
  12. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    8,255

    Display name:
    Dan Thomas
    It's the right color, too.
     
  13. Lois

    Lois Filing Flight Plan

    Joined:
    Jan 7, 2022
    Messages:
    28

    Display name:
    Lois
    Gorgeous.
     
  14. pfarber

    pfarber Pre-takeoff checklist

    Joined:
    Jun 20, 2021
    Messages:
    221

    Display name:
    pfarber
    So could you redo these number with a real person?