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Thread: Advice and techniques for running at reduced power settings

  1. #11
    Green Goggles's Avatar
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    Quote Originally Posted by Hank View Post
    Goggles,

    My Owners Manual recommends 20"/1950 RPM for low-speed loitering and flightseeing. But I don't like the way the plane handles there. I often run 2300 down low, and put the throttle wherever I need it airspeed-wise. Food runs to the next county are 23/2300; flightseeing can be anywhere from 16-20" & 2300.

    Bill, my C holds 52 gallons, burns a pretty steady 9 gph [good for 5½ hours], and won't run LOP without lots of vibration. 201's do it nicely if your injectors are balanced, but carbs are difficult to get there even with slightly reduced throttle and partial carb heat. I probably average ~140 knots groundspeed, indicating around 140 mph at 6000-8000 msl.
    Awesome info, Hank, thank you. I always like to hear how other Mooney owners operate their aircraft.
    I am going to begin doing some expermentation with different settings and see what works for me.

    My C also holds 52 gallons. I do all of my flight planning on 10 gal/hour.
    My bladder has never allowed me a flight much longer than 3 hours, and I suspect it never will.

  2. #12

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    Although I now own a Be 36TC and like it, I still have a soft spot for Mooneys. My first plane was the "70 M20C Ranger, and I just felt like I had a better or more advanced plane for my needs then than something like a C 182 which is another very popular plane in my area.
    I only had the C for a few years and moved up to the "77 M20J, 201, for the better avionics and a little more climb and speed. It had great King KX 175 B radios which are great and reliable and simple to operate. The KX 155s in my Bonanza are good to , but not quite so obvious to operate.

    My normal practice is to refuel after a flight, before leaving the plane. It saves the time and trouble of doing it right before your next flight and takes away the temptation to take off with less than full fuel if there is some delay in getting topped up when you get ready to go.
    So flying the 201, you come in and top off. The you really don't need to worry about fuel range next time on any normal flight. It burns less than 10 gal per hour and holds 64 gal. That is sure a nice asset to have. My cruise flight planning was 155 knots ,as I recall, and often would work out a little faster.

    I have mostly flown 4 airplanes in my time. Range in time for each was, about 6 hours, about 5 hours, about 3:45 and 2:10 til empty. There is some careful planning and a bit of edge of seat flying when you get planes with shorter range.
    I think the real comfort level is 3 hours.

    The worst airplane that I know of for lack of fuel range is a Polikarpov, the little Russian open cockpit WWII fighter. It has only about an hour of fuel. One year Dave Morse was flying one at Midland CAF. The photos guys wanted to get some shots of this new and rare bird. Normally you'd go outside the airport area and maybe spend a half hour or 45 min in formation getting such shots, then come back to land. No big deal, but for this plane you really had to plan and be carefull. It was a quick 5 min flight to the photo area, perhaps 30 min max for pictures and then straight back to land, no delays can be done.

    Hank, if you are indicating 140 mph at 8000 feet that is pretty fast. If you use the rule of thumb of 2% more true airspeed for each 1000 feet of altitude above sea level, then that would be an additional 16 mph so your true is 156 mph, which seems pretty good for a C.
    If you are wondering, a good 201 really will go 201 moh in level flight, I have done it, but that is full power at about 7500 feet, not normal cruise. And I have had mine over 19,000 feet when light, did lot's of flights at 15,000 or so to get over the mountains.
    Last edited by Bill Greenwood; 10-12-2012 at 03:09 PM.

  3. #13
    Hank's Avatar
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    Bill--

    Here's a photo indicating 135 mph at 11,000 msl. Just don't look at the groundspeed visible on the GPS, it's too depressing.

    Well, the system won't let me attach. The window comes up blank, then I refresh it and have to sign in again, and it goes blank. Repeated twice, no luck.

    Indicated airspeed = 135 mph [~165 mph true]
    Altitude = 11,060 msl [setting ~29.98]
    VSI = <50 fpm descent
    GPS groundspeed = 114 knots [~131 mph]
    — Hank
    1970 M20-C

  4. #14

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    Hank, if you have an indicated airspeed of 135 at a pressure altitude of 11,000 that seems pretty fast to me for a C. Using the standard of 2% more of true airspeed per 1000 above sea level thus add 22 mph and you have 157 mph true.
    That's not counting temp correction . Standard temp at sea level is 59* F or 15*C. At a standard lapse rate of 3 1/2* F per 1000 feet that is 39* so if you were warmer than 20* at 11,000 you have a true airspeed that is even a little bit faster than 157.
    What was your power setting then, and or % power?

  5. #15
    Hank's Avatar
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    Bill--

    Double-check your math. 11,000 msl = 22%; 135 x 1.22 = 164.7 mph.

    OAT was 63ºF at the time, and I've forgotten how to compensate for that in speed. The far side of the panel is not in the photo, but it was most likely 2500 RPM and as much MP as I could get. I typically run WOT in the climb, then pull back enough to make the needle move to create a little mixing turbulence in the carb before I start to lean.

    My Owner's Manual says I should have 20.2" available at 10,000 msl, 23ºF, giving 71% power at 2500 [so 63º is 4% less, or 67% power] with speed between 161 and 164 mph depending on weight [gross = 161; 375 below gross = 164]. Summer in the South is warm even at altitude; I was coming back to WV from the beach at the beginning of August.

    I'm getting book speed, or durn close to it. Guess the "speed loss" from the 3-blade prop is canceled out by the 201 windshield. Is it not normal to achieve book performance? It also says 9.0 gph at that altitude/power setting. Pulling back to 20.0" costs 1 mph at both weights and reduces fuel flow to 8.8 gph. My block average for five years is right at 9, so I'm doing something right.

    "Life is too short to fly slow." At least when I'm going somewhere; slow flight and flightseeing both have their places, too. I bought this plane to go places, and I've gone south to Miami, east to the ocean and west to Yellowstone; still working on the "north" part.

    But the OP was asking about low power, as in flightseeing. I use 2300 RPM, set power as needed for the speed you want. Recently, 16-18"/2300 kept me right at the top of the white arc, giving people plane rides. I took 15 people up on 8 rides that day--climb out at WOT/Max RPM, pull throttle way back, set 2300, trim trim trim, adjust throttle for ~115 mph indicated at 1000-1200 agl. The handling isn't too sluggish, and I fit in with the Cessnas doing the same thing. but then again, I was pulling back before leveling off, too.

    It's a versatile plane, learn to fly the whole envelope. Lots and lots and lots of fun! Even more fun to share the experience!
    — Hank
    1970 M20-C

  6. #16

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    Hank, I think your math is better than my mental calculation. I just took 2% times 11 and came out with plus 22 mph when it should have been plus 22%, or as you say 164.7 mph.

    Now as far as a correction for non standard temp, the warmer the temp where you are actually flying, then the faster your true airspeed. Your 63* is much warmer than I think standard of about 20* at 11,000 feet so you are actually faster than 164 mph.
    I thought that was pretty fast for a M20 C from what I recall,but you didn't say before that you had the 201 windscreen which I'd guess will add about 5 mph.

    I don't have my E6B with me now to calculate it.
    Last edited by Bill Greenwood; 10-18-2012 at 05:03 PM.

  7. #17
    Hank's Avatar
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    Bill--

    Standard temp at 10,000 is 23ºF; subtract 3 for another thousand feet makes it 20ºF like you said, or 43ºF above standard. My whiz-wheel is at home, but about all I use it for anymore is figuring speed correction for winds. I'll have to get it out and play.

    Do you agree with many people who say the 3-blade losed 3-5 mph, just like the 201 windshield adds it? I always figured they canceled each other out.

    Hmmm, still can't attach a picture. "Manage Attachments" brings up an empty, blank window.
    Last edited by Hank; 10-19-2012 at 11:17 AM. Reason: Tried to attach photo, no luck
    — Hank
    1970 M20-C

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