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Service ceiling of the Bearhawk LSA

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  • Service ceiling of the Bearhawk LSA

    Can anyone give the service ceiling of a Bearhawk LSA at a gross weight of 1320 pounds.

    I live in the west side foothills of the Sierra Nevada near Yosemite and often fly east over the range, hence the question. I like to cross at 13,500' or a bit more.

    Thanks for any help with this question.

    wil

  • #2
    Wayne Massey did some climb testing with his LSA, loaded to 1164 lbs (that's 156 lbs below gross weight). I'm pretty sure he was single-pilot for this exercise. Still, the results were pretty impressive. His test flight showed the initial rate of climb was over 1700 FPM, and his LSA was still climbing at 488 FPM (measured) between 13,000 to 14,000 ft. Here's the link to that thread.

    If we extrapolate his performance using a linear rate that continues the same slope as the decline from 9K to 14K feet, it looks like the service ceiling (at his slightly reduced weight) would be around FL200 (20,000 ft MSL). But the assumption might not be 100% accurate, so let's just say it's probably very close to the floor of Class A airspace. Still VERY impressive!

    Based on your scenario, I'd be pretty comfortable with the LSA having adequate performance to clear the 13,500 ft mountains. It took Wayne about 12 minutes (and change) to climb from 6,000 ft to 14,000 ft, and he was still climbing faster at that altitude than my similarly powered (O-200) Champion 7ECA will climb at Sea Level...!

    My 7ECA, by the way, has a service ceiling of about 9,000 ft, with an initial ROC (SL and max GW) of around 450 fpm. (Damn, I wish I hadn't actually figured that out! Makes my 7ECA feel kinda "puny"... But it also explains why all the new orders seem to have opted for the O-235 Lycomings when that engine was offered as a low-cost "upgrade" option, a few serial numbers after my airplane...)

    Hope that helps.
    Last edited by JimParker256; 11-12-2016, 04:41 PM.
    Jim Parker
    Farmersville, TX (NE of Dallas)
    RANS S-6ES – E-LSA powered by 100 HP Rotax 912ULS

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    • #3
      It's always worth considering the aircraft's ability to deal with persistant downdrafts too.

      Mountain wave is pretty common, and 500 ft/min down flow is an every-day occurance when it's windy above the mountains.
      Even 1000 ft/min isn't hard to find, both of those can persist for minutes at a time if you are crossing at right angles to the mountain range. In other words, you could lose several thousand feet of altitude in an underpowered plane.
      The best (worst?) I've see was ~4000 ft/min on a seriously windy day, which fortunately lifted me from 6,500ft to 9,500ft in the space of about 45 seconds before I flew clear of the airflow. Better up than down!

      I would consider a 500 ft/min climb performance as a practical service ceiling limitation in mountainous terrain, on a fair weather day. I used to hit that limit at gross weight in a 150hp C172 at about 11,000ft. But that's just my opinion, of course you can get higher, but then you're totally at the mercy of the mountain wave.
      Last edited by Battson; 11-30-2016, 03:28 PM.

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      • #4
        If you compare the Bearhawk LSA to any other plane in its class, it has the best performance. More or less 100 HP and same gross weight - you will not find anything better. If you wanted better climb ability at altitude, a light Patrol would be a step up in capability. But the LSA with a strong 100+ HP engine and right prop sounds like it will do what you want. Mark

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        • #5
          Hi Wil,

          If I may, Battson makes a very important point, service ceiling at a given hight should be define by 500ft/m climb at Wo (Gross) anything else is an understatement. Cl_max, and consequently AoA Cl of the airfoil should harness the power/wait ratio of the craft at a given altitud.

          IMHO, a question of safety merits a "pilot's" answer, and I'd say from the data (Disclaimer, have not flown a Patrol or LSA), you are marginal on the service ceiling (as defined before) on this airplane with the power ratio of an O-200, assuming the numbers given on the link from JimParker. I've only flowed your area once on a 172 XP (175) , and we could not get over from RP8 to RP27. The plan was to go to Hungtington Lake then D-TO RP27... down drafts at around the lake area... just heading almost NE of the lake... we could not get a good climb. It was a frosty X-mass eve and with 2h of gas and my petite GF (I was closer to 80kg at the time than the ~90kg today ) what looked like an easy fly became a glad that was over... Now I have flown that particular airplane further south where there was a little less margin (listed service ceiling of 14000 ft) and the mountains we where going over and the airplane had performed well. Guess you can make your own mine up, but that margin was thin and we took advantage of a planned and perfect day to get over... otherwise I would have never dared to even consider... IMHO.




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          • #6
            While 500 ft/min would be nice, i believe the definition for our type aircraft is 100 ft/min at Vy.

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            • #7
              Originally posted by jim.mclaughlin924 View Post
              While 500 ft/min would be nice, i believe the definition for our type aircraft is 100 ft/min at Vy.
              Yes you are right, service ceiling is ususally defined at the altitude above which an aircraft is unable to sustain a certain rate of climb. 100 ft/min is a typical value.

              To reiterate my post, I wasn't disagreeing with the definition, I just think it would be prudent to assume a higher rate of climb for moutain operations. That way you have a safety factor. Flat land flying is a totally different proposition to moutain flying.

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              • #8
                If I may, let me clarify my answer some what to make sure I don't miss out in pointing out my intent. Service Ceiling is a Pilot's self declaration base on know performance metrics from an aircraft. It's up to the pilot to determine if the airplane (as a tool) will meet their needs. I was using a real life example of a know (certified type) to prove that.

                Ok, now, on a homebuilt airplane, you can have a reference for a discreet airplane, as weight/power ratio varies and so does propeller choices (efficiency.) In the of the test ran by Massey, it's a great staring point to set expectations on what can be expect from the type aircraft, but it's up to the builder/pilot to determine how that discreet platform will perform given the variables in the configuration and weight through the build process.

                As to the test from Massey, I would have hoped for a weight/balance sheet at W_o, static pull test (ft/lbs,) and data of propeller used to further enrich the great performance numbers of the BH LSA is able to produce, IMHOP.

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