Cessna 182 speed and fuel burn

Discussion in 'Hangar Talk' started by cass-cove, Sep 3, 2014.

  1. cass-cove

    cass-cove Filing Flight Plan

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    I recently bought a 1975 C182P. It has a zero timed engine with only 190 hours on it. It runs great and seems to have loads of power for what it is.

    I found another thread on fuel burn for the 182:
    http://www.pilotsofamerica.com/forum/showthread.php?t=61014

    which was helpful and interesting but did not quite answer my questions. I have been monitoring my fuel burn fairly closely. I'm doing a lot of touch and goes, climbing and descending and short flights so I would assume my burn would be a bit higher, but found that I am consistently burning 10.5 to 11.5 GPH.

    That is all fine, but I am really confused about speed/performance. My plane seems to be flying very slow compared to the speed I should be flying based on the cruise performance chart. I have tried flying at various altitudes and numerous MP and RPM combinations but it seems that basically no what I do, the plane will not fly over 115 knts (this is all for carefully trimmed level flight in smooth air). I have typically tried to fly at various MP/RPM settings which would give me around 60% HP, which should give me approximately 130kts. These settings along with my recorded fuel burn fall right in line to give me the 130kts in the charts, but my plane just cruises at 110 and will not go over about 115kts in smooth and level flight.

    I thought possibly the IAS was incorrect, but I have checked it against my foreflight speed (then calculating for a tail/head or cross wind) and IAS and foreflight are nearly exactly the same. Always getting the 110kts on IAS and about the same on foreflight.

    I have made sure my cowls are closed (which seem to affect speed by maybe 2 or 3kts), that I'm trimmed properly, numerous experiments with EGT (which I normally set to about 50ROP), etc. etc.

    My thoughts on what is going on (because I do think my airspeed indicator is correct):
    1. MP gauge is incorrect so I'm flying at a significantly lower MP that I think I am (a user on the forum I linked above wrote: "I was at 8500ft, wide open throttle at 21mp, 2300 rpm". When I am at that altitude and if I did the same settings, I would probably only be at half throttle)
    2. Very old ADF/GPS and possibly a couple other antennas have been added over the years. This seems like very limited drag but could this be affecting speed?

    Given all my setting experiments (EGT, RPM, MP, trim, Cowl, etc) and average fuel burn of about 11, everything I'm doing supports IAS of 130kts, but I'm not getting that. Why????? Ideas, thoughts, etc. would be very most appreciated!

    Thank you!!!
     
  2. MooneyDriver78

    MooneyDriver78 En-Route

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    Check your POH for what the numbers are suppose to be at 8000', go up and set the RPM to 2400 or whatever RPM(s) is listed in the table for 8000', go full throttle, compare to POH: MP, FF, airspeed... you will need to adjust altitude if not standard conditions.
     
    Last edited: Sep 3, 2014
  3. poadeleted20

    poadeleted20 Deleted

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    130 KTAS on under 11 gph is not happening with a 182. The fuel burn you're seeing is appropriate for a lower speed, and a higher speed would result in a higher fuel burn. You need to go back and check the calibration on all the instruments and systems involved, including MP, tach, fuel flow gauge, airspeed indicator, and pitot and static systems.
     
  4. kayoh190

    kayoh190 Administrator Management Council Member PoA Supporter

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    I have the POH for a 182R that I used to fly, and the cruise airspeeds given are true, not indicated. I can't imagine it'd be different for yours. 115 IAS is about 130 TAS at 8000' PA, which at least in the ballpark.

    It's not really the same plane, but for the record, the 21" and 2300 RPM show 138 KTAS and 12.1 gph at 8000' PA and standard temp.
     
    Last edited: Sep 3, 2014
  5. Topper

    Topper Pre-takeoff checklist

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    I regularly see 142-143 knots true airspeed. I am top of the green at 7500 (maybe a little lower mp, throttle firewalled). I burn about 15gal per hour in a 1979 182Q that is a couple hundred hours past TBO.

    Jim
     
  6. CTLSi

    CTLSi Ejection Handle Pulled

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    First, IAS is not how cruise and max speed are expressed, those numbers are KTAS...

    Second, make sure to take into account Density Altitude. Performance is a function of DA. So is ceiling and max operating altitudes.
     
  7. cass-cove

    cass-cove Filing Flight Plan

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    Jim: this is helpful. What is your RPM? I can hit top of green at about 1/2 to 2/3 throttle. It's starting to feel like my MP gauge is inaccurate.
     
  8. AggieMike88

    AggieMike88 Touchdown! Greaser! PoA Supporter

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    The original "I don't know it all" of aviation.
    I fly a 1975 C182P.

    The highlighted is accurate for me, but only at lower altitudes. As I climb, I loose MP as expected, about 1" per 1000 ft. Between 5000 and 6000 ft MSL, my throttle is all the way forward

    Cass; you might need to qualify the quoted statement with what altitude you're at when you are "top of green at 1/2 to 2/3 throttle" to helps understand what you see.

    If you suspect your MP or tach is malfunctioning, I'd encourage having it looked at ASAP. Bringing them back within spec will make operating your aircraft easier, and reduce the chance you're doing harm to your engine.


    FYI; keep this in mind if the price to replace or overhaul your MP/Tach gets up there in price: http://buy-ei.com/portfolio/cgr-30p-overview/

    Our club just got a very economical quote from a local avionics shop to install this into our 182P. Covers lots of features we want/need and does it in one very useful package.
     
  9. Norman

    Norman En-Route Gone West

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    What Ron said in post #3.

    If that doesn't work you may have a rigging problem. Wings out of proper rig will slow you down.

    Link to a shop that does rigging. That may give a better explanation.

    http://www.cessnarigging.com/
     
  10. cass-cove

    cass-cove Filing Flight Plan

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    I was agreeing with the statement "I am top of the green at 7500..." but did not write that. Sorry it was not clear. Thanks so much for your feedback.
     
  11. AggieMike88

    AggieMike88 Touchdown! Greaser! PoA Supporter

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    The original "I don't know it all" of aviation.
    I know of John and his work. And his shop is in my home area. There is good reason he has earned the nomiker "The Cessna Whisperer"
     
  12. Topper

    Topper Pre-takeoff checklist

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    The rpm stays at the top around 2450. Mp is 26-26 on take off and I never pull back if I am climbing to a cruise altitude of 5500 or more. It will naturally come into the green. My best speed is always with the prop fully forward.

    If I am staying low and maneuvering or hoping to a close airport, I will pull the power back into the green.

    Jim
     
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  13. kayoh190

    kayoh190 Administrator Management Council Member PoA Supporter

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    It certainly seems that way. But look on the bright side - 10.5 gph! :D
     
  14. N53KL

    N53KL Pre-takeoff checklist

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    I do not wish to dispute any posters here. I can only offer what I have experienced.

    I have owned my '76 C182P for the last 11 years. I flight plan and get 130kts TAS at all altitudes up to 10,000'. The only difference is fuel flow. That ranges between 12.5 to 10.5 GPH. As a "flatlander" (mostly sea level) I usually fly my 100nm+ legs at an average of 5000'. I consistantly see 130kts and 11GPH at that altitude.

    based on your posts, you seem to be a pretty savvy aviator so I predict that something is not right with your aircraft if you are 15kts slow all the time. From what you have stated, it sounds like you are producing plenty of power. If so, either aerodynamic or instrument indication issue.

    I suggest you plan out a triangular course and take GPS groundspeed readings on each leg. You can compare this to the winds aloft forecast and compute a ballpark TAS figure. Use the math, not the guages to determine this what your TAS is. If you still see 115kts, you can eliminate the instrument indication and concentrate on the aerodynamic issue. Just a humble suggestion but in troubleshooting, you start with eliminating the easiest and least complicated and work upward ;).

    Honestly, you should be realizing the 130kts number in your Skylane.

    Kevin
     
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  15. poadeleted20

    poadeleted20 Deleted

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    I think your feeling is correct. As I said before, get your instrumentation checked.
     
  16. poadeleted20

    poadeleted20 Deleted

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    Unless you're flying from an airport at 4000 MSL or so, that's way too low for full throttle MP on takeoff. At SL, you should be pulling right near 30 inches, and 1 inch less for every 1000 feet above that. If you're not seeing that, something's wrong somewhere.
     
  17. Topper

    Topper Pre-takeoff checklist

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    I meant 26-27, and Ron may be right that it is higher. I am at 1500 feet and lately the da has been 3-4k. I should look at it more often, but I know the feel and if something is wrong. I will pay more attention next time I fly it. Been logging time in a 310 preparing for my multi ride on Friday if the weather holds.

    Jim
     
  18. Norman

    Norman En-Route Gone West

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    John's earned the title. I've done my fair share of rigging over the years but John makes me look like a rookie.
     
  19. Jeff Oslick

    Jeff Oslick En-Route

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    The main problem here is the OP's lack of conversion from IAS to TAS.

    No wheel pants also costs speed, don't know what the OP has going on there.

    Bad flap and flight control rigging can cost a couple knots too.
     
  20. onwards

    onwards Pattern Altitude

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    Says who? my 182 consistently does 135KT with no winds at <11GPH at 6500ft.

    Of course, it's a P-Ponk... :rofl:
     
  21. Norman

    Norman En-Route Gone West

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    Agreed, but so can the cams on the rear spar attach points if they are set to lower the trailing edge.
     
  22. N747JB

    N747JB Final Approach

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    I suspect the MP gauge, at 8500 ft you should be at full throttle, with 21 +/- MP, set the RPM as you wish.:D
    What is your rate of climb solo?
    I'd definitely get it checked, I don't get 130 knots true at 60% power, it's usually closer to 70% power in my Q model, my speeds are generally 2-5 knots less than book, typical of most Cessnas I've flown.;)
     
  23. denverpilot

    denverpilot Tied Down PoA Supporter

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    Ours averages 11.5 GPH over four years mostly at altitudes above 8500. We are a little slower than most 182s with stall fences on top a droop tips. No 182 I've ever flown makes Cessna book numbers. Usually 2-4 knots slower. Ours is 5.

    The tach is the first thing I'd check. Easy to do with a sodium light at the airport at night. 60 Hz. Pick a speed divisible by 60. See if the prop looks like it stopped in the light.
     
  24. Jeff Oslick

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    I have done it many, many times. I've flown many times in the 12,000' to 14,000' range leaned out to as low as 9.2 gph at 13,500' getting 137 KTAS. Pretty close to standard temps. This is in Pponk (275 hp) 182. A little lower burning a little more fuel in a stock 182 and getting 135 KTAS is not a problem at all. Once you're above 10,000, just lean it out, you can't hurt anything running lean at that low a power setting.

    Jeff
     
  25. Jeff Oslick

    Jeff Oslick En-Route

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    After new paint, fairings and a rigging job we did get book numbers when we still had the stock O-470U engine.
     
  26. onwards

    onwards Pattern Altitude

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    Oh yea, the P-Ponk is awesome.

    When I flew to Santa Fe from Concord - about 800nm - I did it in a straight shot, no stopping, under 5:40h takeoff to touchdown, and landed with well more than an hour's reserve. You can do your own calculations, or if you don't feel like it, I can tell you I averaged ~140KT with am average burn of ~10GPH for the entire trip, which was mostly at 115 and 135 msl.
     
  27. Jeff Oslick

    Jeff Oslick En-Route

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    The problem I have is that I get perfectly fine TAS performance, but headwinds *always* find me.
     
  28. rednksurfer

    rednksurfer Filing Flight Plan

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    the above posts are all wrong and do not take into account the RB factor. If you will go to the prop and grasp both sides of the prop, pull about 5 inches you will be able to turn the prop while it is disengaged from the gear and that will allow you to wind the big rubber band tighter for a much faster flight experience.
    Jim
     
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  29. James331

    James331 Ejection Handle Pulled

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    New paint makes you look faster, not go faster :D


    But yeah, for the OP be sure you're not confusing IAS with TAS, check your rigging and make sure you're not needing tons of trim to fly hands off, also be sure the plane will fly straight and level hands off, minimal trim and same amount of fuel in each tank, I've also found doing some nice coordinated stalls is a good way to check trim, if she's always wanting to drop one wing that can be a sign.
     
  30. Henning

    Henning Ejection Handle Pulled

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    Far too many factors to address without inspecting the plane and flying it.
     
  31. Dr. O

    Dr. O Pattern Altitude

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    Just a comment - pattern work always has a lower fuel burn than cruise.

    Borrow someones GPS, even a car or sport GPS, and see what your ground speed is compared to IAS and then calculate what your TAS should be.
    Do runs with the wind, against the wind, and across the wind. Also get the wind data for that time from the nearest reporting station.
    You can calculate your TAS with those numbers and get an idea if your ASI is correct.

    MP gauge should match the reported barometer setting at the airport - with the engine off.. If it is close on the ground it is more likely than not it is close in the air. If you have an airplane portable GPS you can look at the GPS altitude offset while on the ground against your altimeter - and then do the same at various altitudes in flight and quickly determine if the altimeter is right.

    At that point only your tachometer needs checking - and as the guys point out a mercury or incandescent light at night will tell you that.

    Now fuel burn - are you filling the plane and calculating it against watch time - or taking it off the fuel flow meter? The only accurate way is a full tank. Take off on the other tank, switch in the air, do a timed run on the test tank, switch back, land and refill the test tank.
     
  32. denverpilot

    denverpilot Tied Down PoA Supporter

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    I trued out at 139 knots today at 9,500 on a cold day burning 11.5 GPH over the 12 hours to Vegas and back ... Which is pretty standard for our 182 P model with the STOL kit and a bit of drag from the stall fences on top.
     
  33. denverpilot

    denverpilot Tied Down PoA Supporter

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    P.S. that's flogging it for all its worth at 9500 with WOT and 2450 RPM, "top of the green" even though the green is generally meaningless on the 182P.
     
  34. Henning

    Henning Ejection Handle Pulled

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    You can fly a 182 WOT and Max RPM all day and never flog it.:rofl: The 182 engines, either of them, are seriously derated engines.
     
  35. denverpilot

    denverpilot Tied Down PoA Supporter

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    Yeah I should have put "flogged" in quotes. Hahaha.

    Was only pulling 16" MP going over the pass westbound WOT. That's better than in summer!

    Next airplane needs a turbo. Haha. Or two engines and a very light load. :)

    And for anyone who doesn't quite "get it" yet about mountain flying, I had a good idea what the winds were going to do on Corona/Rollins from prior experience in there. There were pireps for moderate turbulence west of BJC and that's completely normal. You're in the downhill rotor there, big time.

    So I pointed the thing west and tightened the belts expecting the bumps. Got the bumps and a downer that knocked 1000' off my altitude at Vy with WOT. Knew that was the "usual" spot for that behind the mountain to the northwest. Wait... Patience. Enjoy the wing rocking. Couple of "potholes" that banked the airplane about 30 degrees one way and then 20 the other. Thump thump. Well below Va so just ride it out. The glider kids in Boulder do this on purpose too, and they're usually on-tow trying to get to the ridge lift side of it, but they often have to release and plow forward without the tow plane.

    Take up the 45 angle toward the low spot in the pass and wait... In another mile if you get another downer or can't climb, it's bail out time and it'll be obvious...

    And then the upper, just past Eldrora Ski Area like clockwork, as you get into the upwind side of the wave. Sometimes it works, sometimes it doesn't. Yesterday was a "works" day. Wheeee... Totally smooth and I'm going up 2000 fpm with the throttle almost to idle. Went right through my target of 12,500 on up to 13,500 for about 60 seconds while I got the nose down and kept the power back until it settled down.

    Just let the speed bleed back down and then set WOT again and make damn sure you're gaining speed and not losing altitude.

    Funny thing was I'm sure DEN TRACON was getting a kick out of watching my altitude go nuts and knew I was seeing what could be done. They had asked me about the ride through there. Told them the usual moderate turbulence and wave from the foothills to Eldora and then smooth. I think they put out my report of additional moderate as another Urgent PIREP, but there wasn't anything particularly urgent about it. Either you can make it over or you can't.

    Had another local pilot stomp on KAPA Ground when he heard I was headed NW to Corona Pass... He keyed up and said "there's multiple PIREPS for moderate turbulence west of Metro (!)..."

    I just replied that we knew that. He was trying to be nice and save my butt if I was unfamiliar with the pass. Controller says, "ohhhh-kay" and gave me my takeoff clearance for 10 again. Heh.

    Don't mind the guy saying something at all, really. If you haven't been through Corona/Rollins a whole lot, you really shouldn't be playing up there with those kinds of reports. I knew it was a "see if it behaves closer to the ridge but have a way out at all times" type of pass crossing yesterday.

    With all the lovely high pressure and not a massive pressure differential between the west and east sides of the Divide, I'd have probably attempted to cross again today, but time got late and with the sun setting near 16:30 and sooner in the mountain canyons, I went around the long way. Couldn't get out of Vegas early enough, plus the time zone change... and I simply won't fly the mountain valleys without daylight in an underpowered aircraft. Too damn much stuff that may rise up and smite thee.

    It's nice when it turns into a massive up elevator, but it doesn't always manage to do that. Gotta have a bail out plan and stick to it.
     
    Last edited: Nov 23, 2015
  36. Jim Rosenow

    Jim Rosenow Line Up and Wait

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    Apologies for hijacking the thread, but are you willing to put a ballpark figure on 'very economical'? Thanks!

    Jim
     
  37. kgruber

    kgruber En-Route

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    Toss the wimpy nose wheel off, and gain 5 knots to any of the claims above.

    Cessna 180. Too bad you can't buy a new one. Someone should STC a nose wheel removal on the "new" 182.
     
  38. James331

    James331 Ejection Handle Pulled

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    All straight tail 182s should do that.
     
  39. Henning

    Henning Ejection Handle Pulled

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    My local speedo shop charges me $25 to calibrate a mechanical tach. If it needs a drive bearing add $5. Maybe 1 in 100 needs one.
     
  40. kgruber

    kgruber En-Route

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    They "should," but none can keep up with the same year 180.:yes: