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  • #16
    Just a thought... The EAA has a new publication ("EAA Flight Test Manual and Test Cards" - under $20 for EAA members) that is an excellent guide for what to do during Phase 1 test period. The book shows how to gather the information to create a POH, including the formulas for "normalizing" the data. Anyone building a plane should give serious consideration to using this manual, and developing a POH that would answer the questions FOR THAT SPECIFIC AIRPLANE. There is a webinar on their site that talks about the process, and Vic Syracuse (one of the presenters) makes the comment that every homebuilt is different – even RV-12s built from identical kits, following identical instructions can have performance differences (rigging, alignment, etc.). How much more so with a project like a Bearhawk? I would not "bet my life" on someone else's numbers, even if they had built the exact same model with the same engine and prop...
    Last edited by JimParker256; 04-15-2020, 10:28 AM. Reason: Updated with link to EAA.org publication...
    Jim Parker
    Farmersville, TX (NE of Dallas)
    RANS S-6ES – E-LSA powered by 100 HP Rotax 912ULS

    Comment


    • #17
      I think there are too many variables in engine/prop/tire size/pilot technique to come up a "standard" set of performance numbers. There are enough numbers quoted here on this forum, along with the published specs on the kit website, to get a decent idea of performance.

      I think with a similar engine (360 or 540), it will TO and land at least as short as a comparable Maule. It will out climb a Maule (equal motor) with equal load because most BH's are lighter, and cleaner aerodynamically. Cruising speed is similar.

      For me, it is a better Maule than an actual Maule. Especially if you keep it light. BH's have a better useful load.

      And they are experimental which is a gigantic plus for me. It might be a negative for others.

      So I would look at a Maule, drop 100-300 lbs off the empty weight. Higher gross weight than all but the newest Maules. It climbs better.

      That was how I looked at it, and it still works for me. If a Maule would work for you, so will a BH. It will just do it all a bit better.

      Comment


      • #18
        Originally posted by svyolo View Post
        I think there are too many variables in engine/prop/tire size/pilot technique to come up a "standard" set of performance numbers. There are enough numbers quoted here on this forum, along with the published specs on the kit website, to get a decent idea of performance.

        I think with a similar engine (360 or 540), it will TO and land at least as short as a comparable Maule. It will out climb a Maule (equal motor) with equal load because most BH's are lighter, and cleaner aerodynamically. Cruising speed is similar.

        For me, it is a better Maule than an actual Maule. Especially if you keep it light. BH's have a better useful load.

        And they are experimental which is a gigantic plus for me. It might be a negative for others.

        So I would look at a Maule, drop 100-300 lbs off the empty weight. Higher gross weight than all but the newest Maules. It climbs better.

        That was how I looked at it, and it still works for me. If a Maule would work for you, so will a BH. It will just do it all a bit better.
        It's generally both faster in cruise and slower in stall than a maule as well.

        Comment


        • #19
          I also wanted to see performance numbers before I bought my Patrol kit. I watched every Bearhawk takeoff or landing video I could find but they weren't all that helpful as you generally have no idea what the wind, elevation and temperature are or if the pilot was trying to use as little runway as possible or what the pilot's skill level is. I finally got a ride in a Patrol and saw first hand that it was more capable than any of the other planes I was considering and decided to build one.

          I intended to make my own performance charts but the truth of the matter is that it would be quite an undertaking for most airplane owners to do that. Trying to get data for different temperatures would be one thing. But of course you would want calm winds so the data means something. Then figuring in days of the right temps with the right wind conditions and flyable weather at the same time you are off work. Maybe in a year you could cover the temperatures that occur at your home base. But that covers one one elevation. Plus you have to do it all at different weights.
          Rollie VanDorn
          Findlay, OH
          Patrol Quick Build

          Comment


          • JimParker256
            JimParker256 commented
            Editing a comment
            But there are well-known formulae for adjusting (normalizing) your data. Yes, you'll need to do the testing at one fairly consistent weight (just as your "certified" plane's charts are mostly set up for max gross weight). But that EAA book is supposed to have the information needed to take a smaller set of measurements, then reverse-plot the results. My book is (hopefully) sitting at the PO, so I'll confirm that when I have it in hand.

            By the way, since my '65 Citabria 7ECA had absolutely no POH whatsoever, I took some rudimentary measurements, then used that data (and the standard formulae / "rules of thumb" that are easily found on the internet) to modify the performance charts for a later-model 7ECA that had a larger engine (O-235 vs. O-200). In the process, I was pretty conservative with the numbers – always rounding to the more conservative value. It's certainly not perfect, but it's a lot better than nothing. I hope the EAA book will help refine that, by showing me what performance tests need to be done to create better data.

        • #20
          I might suggest to those who own airplanes to start playing a silly game with yourself.

          Before each takeoff guess how long your take-off roll will be and use runway lights (they are 200' apart) to measure actual performance.

          Its okay to guess wrong, but over time you will get very very good at GUESSING. If you did five takeoffs today, you would get the third takeoff distance guess to within 40 feet I bet.

          Well, at that point, a guess is not a guess, rather its a data based prediction, which is moving towards a POH distance chart. Are you cheating at the game when a guess is based on truthful information?

          The point I'm making is that you will get to know your takeoff distance within a small tolerance while factoring in a plethora of variables. You may also start experimenting with techniques and turn the game into a game of "Can I get off in X amount of feet." These are the first steps I think to going to a "just for fun" STOL demonstration event.

          BTW, a 5 pound bag of all purpose flour is real handy for putting temporary marks on a runway. Using the 200' runway lights its easy to pace things off. You'll get your marking easily within -/+5% without using a tape measure. This works well for marking a target line to practice spot landings as well.

          BTW #2, Knowing your distance to cross a 50 barrier is a bit mysterious to me. I've read where the GPS altitude might be a fair piece of data to use. I would not use a barometric altimeter due to lag and internal resistance. Seems like I read once that in the 1940's on calm days they used helium balloons on a 50' string staged next to the runway.
          Brooks Cone
          Southeast Michigan
          Patrol #303, Kit build

          Comment


          • JimParker256
            JimParker256 commented
            Editing a comment
            That's pretty much what I was doing with the Citabria. After a while, I got pretty decent at using the lights / runway markings (painted stripes) to estimate my takeoff point.

            Then I went to a grass field – no centerline stripes, and no runway lights... Hmmm. Had to do some thinking. There's a trick to estimating runway length whereby you fly the length of the strip a 60 knots (69 mph for me), and count the seconds it takes from one end to the other. Multiply the seconds by 100 ft, and you've got the approximate runway length. (Try it - it's pretty accurate.)

            It took about 15 seconds to fly the length of the runway, so it would be about 1500 ft. Plenty long enough for me to land on. But could I take off again? (Remember – 100 hp Citabria with no flaps, so pretty sucky performance numbers.) My usual "on pavement" takeoff run was about 600 ft, and grass would add somewhere between 20% (firm) to 50% (slightly soft) to that distance (per the "aviation rules-of-thumb"). So maybe 900 ft to get off the ground. There were no trees at the end of the runway, just a 5-6 foot fence that was maybe 50 ft from the end of the runway. With appx 1500 ft, that should not be an issue.

            Sure enough, the landing went as expected - except the distance was quite a bit shorter than it normally was on pavement (because of the drag of the grass, I assume?). The field was pretty firm (that's Texan for "hard as a rock"), so my 900 ft takeoff roll estimate should be easily do-able. When I took off, I used the "get to 70% of takeoff speed by halfway down the runway, else abort the takeoff and you'll barely stop before the end of the runway" rule-of-thumb. "Rotation" speed for that Citabria is around 52-53 mph indicated, so I needed to be seeing ~40 mph indicated by halfway down the strip. There was a building at mid-field that would serve perfectly as the mid-field marker. And as it turns out, I was off well before that point.

            Fun stuff!

          • JimParker256
            JimParker256 commented
            Editing a comment
            Forgot to mention that the climb rate on the old Citabria is so anemic that even though I get off the ground in ~600 ft or so, I can barely make it to the height of the tower (roughly 55-60 ft) by the midpoint of our 7,002 ft runway! So for Brooks' question about "knowing your distance to clear a 50-foot barrier", it is generally true that most control towers are about 50-60 feet tall. If you can see the ground on the other side of the tower, you're above the tower. (Assuming relatively level ground, of course.) That's the best way I know to obtain "real-world" takeoff to 50-ft measurements.

          • Battson
            Battson commented
            Editing a comment
            A truly current pilot can eyeball this to within about 20ft. When you're committing to a spot which has bounders at one end, and a river at the other, which is about 150ft long, you need to know immediately (in your head) the aircraft weight, performance, and spatial requirements.

        • #21
          Originally posted by Daywalker View Post
          Mountainous.. say 1,000' grass/dirt (some are shorter), highest field elevation about 5,000' with a temperature of 30 deg C. roughly in the 8,000' density altitude range? Fully loaded I'm wondering if the airplane is going to have issues in this regime, or would it be fine? Has anyone got some rough numbers on how their plane performs in those conditions? I'm also considering on putting the airplane out of a farm strip eventually, and wondering on how much/little length I can get by with. Cheers.
          A pilot with any sort of proficiency should have no problem under these circumstances, given fair to moderate weather and airstrip approaches that are not too challenging.

          The landing distance fully loaded should be less than 600ft at a grass airfield 2,500 AMSL, all else being equal. So with a reasonable safety margin, of say 50% to allow for all the real-world factors, 900ft is perfectly acceptable.

          I can provide any data you like, if necessary to support this with data. Just define the situation and the data you need.

          Comment


          • #22
            Interesting topic Guys (and Girls) and I'm probably in the same mindset as 'Daywalker' was... As a recent recipient of my BH4B plans I'm still ironing out my feelings about take off and landing space required. While I rack up my hours I will be learning the tips and tricks of off airport but in the meantime my mind is running! To ask a question for an anecdotal answer let me paint a picture. I'm currently house shopping and trying to find some land to fly in and out of. For anyone who flies a BH4 with an IO540 I think a simple question for me is this;
            Assuming 75F, <1000 above sea level, unobstructed approach and a field boundary around 4-5' high.
            if you were 2 people in & light luggage (say 425lbs) and 1/2 std fuel - could a pilot, with average skill, get in or out of a 500' grass field (literally 500' from boundary to boundary) or is this a ridiculous idea for a 4 seat? We all know that there's a 100 youtube bush pilots capable but in the average real world how realistic are my hopes?
            I will likely run fat tyres and a couple of other mods which may improve short field but need to be realistic in standard trim, it may be that something slower might be a better option with my constraints so hope to find out before I notch the first tube.
            If it wasn't for Covid I would've hope to visit one of the bases for a test flight! Any thoughts would be very welcome, and thanks !

            Comment


            • robcaldwell
              robcaldwell commented
              Editing a comment
              Battson provided a very good description for developing proficiency. Refer to Post #14: https://bearhawkforums.com/forum/bea...-seminar-forum
              Last edited by robcaldwell; 08-10-2020, 10:32 PM.

            • Bcone1381
              Bcone1381 commented
              Editing a comment
              Minimum strip length = Touchdown zone length + (landing distance X 1.5) You must land inside the touchdown zone 100% of the time. DQ's don't exist if your short ...its game over.

          • #23
            Honestly there's no way I'd base an airplane at a 500ft strip. Even if it was capable of 100ft takeoffs and landings fully loaded. I would do 1000 minimum since I can quite reliably count on 500 being plenty.

            Comment


            • #24
              I agree with ZKelley2 – 500 feet would be a REALLY short runway for a Patrol. You would have to be really on your game, and absolutely spring-loaded to the go-around position on every single landing, because even the slightest little bit of extra speed, or slightest loss of headwind on short final, or ANY other less-than-perfect condition would mean you no longer have a margin for error.

              Like others have mentioned, I was always taught that when planning for the required runway length, you should use the POH distance for "landing over a 50-foot obstacle" as the "real world" ground roll distance. That allows a margin for less-than-perfect pilot technique, less than perfect engine & prop, etc. Then you add 50% to that figure for safety margin over your 50-foot obstacles...

              Typically, the POH "over 50-foot obstacle" distance for light aircraft is roughly twice the POH "ground roll" distance. If we apply that to the Patrol's claimed 250-foot takeoff ground roll, it would give us an estimated 500-foot takeoff distance over a 50-foot obstacle. (Remember, that's a VERY rough "guesstimate"...) So if there were absolutely no obstacles at either end of the runway, a 500-foot paved runway MIGHT be barely adequate. But start adding in factors for "not-so-perfect" conditions – rule of thumb says +20% for dry grass (+30% if it's wet grass), +50% for soft surface, +10% for every 10ºC above standard ISA, and +5% for every 1000 ft above Sea Level DA – and it adds up in a hurry. Given a wet, soft grass runway in the Texas summer heat, that same Patrol might well require about 1400 ft of runway length, and about 2100 ft of clearance before I got to those 50-foot trees...

              But if you think that 50% safety margin should not apply to you... and you really want to get a good "real world" assessment of your own capabilities, have someone video a series of takeoffs and landings that YOU make in an airplane in which you are reasonably competent... Have them stand even with the calculated distance the book shows for your conditions, landing at your target stop. Note how close to those "book figures" you actually come (without landing short – even once!). Then go back and do it again, crossing the threshold at 50' AGL (or whatever obstacle height you will have at your target LZ). Remember to have the person taking the video move to the new target stopping point. Then do the same for takeoff distances and obstacle clearance distances. Even if you're very, very good, I promise you'll learn a lot from that exercise...

              Doing this on a nice, long runway is NOT a very good simulation for doing it in the "real world" where a mistake could be fatal – or at least VERY expensive. The added adrenaline adds to the degree of difficulty... So, go find a nice short runway in your area and practice there. We've got a 2000-foot grass runway near me with a big hangar right at the midpoint. When I was consistently capable of landing (and stopping) the Citabria in <1000 feet every single time at my home airport, I went to that strip and tried it there. Well, I have to admit it took three attempts to be able to get the plane down and stopped before arriving even with the runway midpoint, even though I was 150 lbs below max gross. With a half-dozen more practice attempts, I was consistently able to get down and stopped with 200-250 ft to spare, but it was still amazingly higher-stress than doing the exact same thing at my home airport, where I practiced on a 7,002-foot long, 150-foot wide runway.

              And here's the kicker: The POH for that airplane says it should take 1034 ft to take off over a 50-foot obstacle, and 805 ft to land over that same 50-foot obstacle. Ground rolls should be 544 for takeoff, and 430 ft for landing. Theoretically, I should have been able to get down and stopped almost 270 feet shorter than my best attempt. And that was after a bunch of practice!

              Yeah, 500 ft seems like a REALLY short runway for a Patrol...
              Jim Parker
              Farmersville, TX (NE of Dallas)
              RANS S-6ES – E-LSA powered by 100 HP Rotax 912ULS

              Comment


              • #25
                500ft is a very short runway and probably not a good idea for all the reasons already stated.

                I will add one point. A 5' high fence at the threshold makes a very large difference in landing distance. . My strip has flat, level gopher hole infested ground leading up to one end and a 4' barbed wire fence on the other. On average, I would say landings are 200' longer over the fence. Just the thought of your gear hanging down, or a quick sink makes you clear the fence by 10' at least.

                So, a 500' strip with fences on both ends is an absolute NO, where 500' with nice hay field approaches is still not a good idea, but an improvement over the one with fences.

                When I started flying, I had a 65hp taylorcraft and a 900' strip. It was ok, but good thing there was no fence on the departure end, since I was usually only in ground effect by the 900' point with 2 people.

                Comment


                • #26
                  That's great Guys & thanks for the honesty. I've read a 1000+ landing claims across a bunch of tail draggers and this is the most useful so far!
                  Last edited by Binker; 08-14-2020, 02:08 AM.

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                  • #27
                    I haven't read the entire thread yet, but last spring on our family Bearhawk trip to UT we did a lot of pacing off distances to get an idea of performance. With density altitudes of 6,000-8,500 ft and weights of 2,350-25,000 lbs, we never used more than 800 ft for takeoff or landing. Most were around 700 ft and we weren't trying for short. At local STOL evetns around 400 ft and 2,200 lbs I've been recorded around 200-250 feet each for takeoff and landing.

                    Comment


                    • PaulSA
                      PaulSA commented
                      Editing a comment
                      12 tons! - that's impressive .....

                    • kestrel
                      kestrel commented
                      Editing a comment
                      Is the location of the comma and number of zeros important? :-/

                  • #28
                    He did it 10 times in a row! Had to in order to get that photograph with the vortex off the left wing. Best BH picture EVER!

                    Comment


                    • kestrel
                      kestrel commented
                      Editing a comment
                      That was a total chance shot. A friend did position on the side of the runway, but didn't expect the steam vortex. The steam was from a lumber kiln right on the end of the strip.

                  • #29
                    Originally posted by Mark Goldberg View Post
                    As I said earlier in this thread - pilot skill makes a huge difference in the numbers people see in their Bearhawks. I will contribute some data points even if they are not exactly the situation you describe.

                    When I lived on a paved strip with probably 2,000 ft density altitude common - I would see take off (no wind) at full gross of 450 ft. Me being an amateur pilot with skills anyone can duplicate. When light, 250 - 300 ft take offs are easy without pushing anything. My same BH in the hands of a better pilot and light - saw consistent 165 - 185 ft take offs in the STOL competitions. That was with my two blade metal prop. With the Trailblazer carbon fiber prop - the distances went down by 30% or so.

                    One more anecdotal story. One the way out to the EAA event at Arlington WA, my BH stopped for gas in Leadville CO. Density altitude was around 10,000. The airport manager told the pilot that he had only ever seen one plane take off shorter - a PA18. And that was back when it had the metal prop. And full tanks. Mark
                    Thanks for that data. Those are the conditions in which I will be flying.

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