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I've had the good fortune of spending a little time with the latest Bearhawk today and yesterday. We've accomplished a lot, and have collected a mountain of data and footage that I've only begun to process. Expect much more! The weather has delayed us and it looks like tomorrow is not going to be ideal, but here is a basic summary of what we have done so far, picking up where Rollie left off.
Day 1 (yesterday): First flights, airplane familiarization for me, a little landing practice, and some rudimentary airspeed calibration runs. Later in the day, we set the forward CG limit, or more accurately, we validated Bob's prediction of where the forward limit would be. We did this by ballasting the right front seat with 180 pounds of concrete, along with the 200 pounds of me in the left font seat. We burned the fuel down to a comfortable minimum, since it is stationed aft of the CG. At this stage, the prototype is equipped with a specially designed ballast system, which can hold up to 152 pounds of ballast in four removable chunks of steel, weighing 38 pounds each. We removed one ballast, and flew the airplane. Then we moved a second ballast up to the rear seat and flew it. This was where Bob expected the practical limit should be. The airplane felt good so we removed the second ballast entirely and flew it one last time. At that CG point I was still able to flare without needing to add power, which was what we were wanting to test for. The nose-heavy condition was very real though. The elevator deflection on final was about 5 inches at the counter balance. Thankfully this bird has 35 degrees nose up travel, as most new model B generation planes have. And it also has the profiled tail which makes a real difference in keeping the airflow attached at the hinge line. In rough numbers, each of my first four flights moved the CG forward 2% of MAC, or an inch and a half (rounding here). The last flight where we removed the ballast from the back seat moved the CG forward 1%, or .6 inches. After that validation, we reinstalled the steel ballast, fueled up, and took the airplane back home to Collin's house. The airplane sleeps there, but his strip is a little short to be doing experimental stuff, so we've been using the municipal airport down the road for these tests. Bob will use this information to make updates to the plans. It is not yet known whether production kits will use the ballast system, or whether that will just be a prototype tool.
Day 2: The goal today was to find the max gross weight and the aft limit. This naturally occurs somewhat simultaneously, because there was no way for us to fly the airplane at a more forward CG while also increasing the weight. Yesterday at our forward-most test, the CG was located at the arm of the front seats. We started the day by making a trip to Tractor Supply. The problem with ballasting up an airplane of this size is it takes a lot of weight. Who knew that this kind of flight testing was such a workout? The store was out of concrete bags but they had some nice gravel and sand tubes that weighed 60 pounds each. We actually weighed each one and wrote down the true weight, which varied from 60.5 to 63 pounds. I tied down three of these in the back seat and departed Collin's for the airport, while Collin drove the rest over to the big airport. Bob wanted us to measure the gear spread at each load, so that we could make sure they did not spread beyond his 74 inch limit, center of one tire to the other. At the first flight we were around 70 inches. We added three more bags to the back seat, for a total of 360 pounds, and flew it again. The handling was slowly changing, in my opinion for the better. I think the heavier wing loading gave it a nicer rhythm in the air when I encountered the occasional bump, and it was easier to land and taxi. Next we added 60 pounds in the center of the baggage area, and 125 more pounds under the rear seat. This put the total rear seat weight at 485 pounds, and gross airplane weight at 2685. It flew fine, so we added another 60 pounds in the baggage for a total of 120, and another 60 pounds at the feet of the rear seat. Then we refueled, adding an extra 210 pounds of gas for a total airplane weight of 3019.7. That was aft of Bob's planned limit by a quarter percent MAC. With all of that on board, the takeoff roll doubled, to around 500 feet. The rate of climb, which had usually been a solid 1500 feet per minute, eroded to a paltry 1000 feet per minute at 90 knots indicated. The gear spread had reached 72 inches, leaving a significant margin for less than perfect landings. At that weight I flew some pitch stability tests. At all speeds it still had positive static pitch stability, but at speeds over around 100mph it did not have positive dynamic stability. But it was still very flyable, and did not require a high level of pilot attention or even full-time hands-on-the-stick flying. I was able to find a high spot in the overcast to repeat the stall series and found no appreciable change to the stall characteristics vs the forward loadings. This thing flies like a Bearhawk should, it just carries more, has more room, and has just absurd thrust. The engine is rated for 315 HP, and fully loaded, here are some preliminary indicated airspeeds at 2000 feet:
19" and 1900 RPM, 6.9 GPH 110 mph IAS (leaned)
23.2" and 2450 RPM, 14.3 GPH and 145 mph IAS (leaned)
26.6" (WOT) and 2440 RPM, full rich mixture, 28.6 GPH, 158 mph IAS
At the heavy weight, the landing roll without aggressive braking (it's not my airplane) was 750-1000 feet. No doubt it could be trimmed to 500-750 just by a more ambitious pilot.
So all of that was before lunch. We decided to celebrate by eating a nice big restaurant meal, something I haven't done in 10 weeks since my home state hasn't allowed it as Missouri has.
After lunch, we had a visit from Bearhawk builder Andrew L. and his delightful family. What we were really needing was a clear enough sky that would allow me to get up to 7500 feet for some cruise performance testing. The sky looked open enough to give it a try, so I removed much of the weight to reach a mere 2660 pounds gross, which is basically four people and no bags other than the steel ballast. I figured this would be a good middle-of-the-road testing weight, and indeed it is right in the middle of our lightest flight weight so far and our heaviest. The clouds were broken up enough to make a safe climb, so I was able to get at least three readings on four headings for 140, 150, 130, and 70 mph IAS. I have not yet had a chance to crunch these to see what they were yielding in CAS and TAS but will do that next. I started doing some glide tests to collect the best glide speed for the bootstrap spreadsheet, but after 7 runs the fuel load was getting down a little, and the clouds were spreading out more than I liked, so I descended back underneath and landed for fuel. After the short hop back home to Collin's we found a mechanical problem with the tailwheel, which spelled a possible end to the flying for this week. Thankfully Collin is as good of a mechanic as you expect him to be, and he found that we were able to fix it without any new parts. Turns out the axle bearings on the tundra tailwheel are directional, and these had been installed backwards, allowing one of the races to pop out. We removed the tailwheel and cleaned it all up, flipped the bearings, and now everything is all lubed up and ready to go for tomorrow. But the forecast is for low barely VFR ceilings again. Fine for landing practice and load testing, but no good for bootstrap glides or more cruise testing. Maybe I'll be able to make some progress with video editing.
I have nearly all of these flights on video, and today Collin recorded around 25 minutes of talking about what it was like to build the airplane. Once I can get some of this edited down I'll post it on the Bearhawk Aircraft youtube channel. Collin also shared all of his build pictures, including some great details about some of the cool innovations that he, Bob, and Mark have employed to bring this beautiful bird off of the plans page an into the sky.
The airplane has exceeded my expectations, and I'm honored to have a chance to get some time in it.
So having said all of that, I have a few more days with the airplane. There are 11.3 hours on the meter, and all of Bob's safety tests are complete. What flying would you like to see, what data would you like to have, and what questions do you have for Collin or Bob?
Day 1 (yesterday): First flights, airplane familiarization for me, a little landing practice, and some rudimentary airspeed calibration runs. Later in the day, we set the forward CG limit, or more accurately, we validated Bob's prediction of where the forward limit would be. We did this by ballasting the right front seat with 180 pounds of concrete, along with the 200 pounds of me in the left font seat. We burned the fuel down to a comfortable minimum, since it is stationed aft of the CG. At this stage, the prototype is equipped with a specially designed ballast system, which can hold up to 152 pounds of ballast in four removable chunks of steel, weighing 38 pounds each. We removed one ballast, and flew the airplane. Then we moved a second ballast up to the rear seat and flew it. This was where Bob expected the practical limit should be. The airplane felt good so we removed the second ballast entirely and flew it one last time. At that CG point I was still able to flare without needing to add power, which was what we were wanting to test for. The nose-heavy condition was very real though. The elevator deflection on final was about 5 inches at the counter balance. Thankfully this bird has 35 degrees nose up travel, as most new model B generation planes have. And it also has the profiled tail which makes a real difference in keeping the airflow attached at the hinge line. In rough numbers, each of my first four flights moved the CG forward 2% of MAC, or an inch and a half (rounding here). The last flight where we removed the ballast from the back seat moved the CG forward 1%, or .6 inches. After that validation, we reinstalled the steel ballast, fueled up, and took the airplane back home to Collin's house. The airplane sleeps there, but his strip is a little short to be doing experimental stuff, so we've been using the municipal airport down the road for these tests. Bob will use this information to make updates to the plans. It is not yet known whether production kits will use the ballast system, or whether that will just be a prototype tool.
Day 2: The goal today was to find the max gross weight and the aft limit. This naturally occurs somewhat simultaneously, because there was no way for us to fly the airplane at a more forward CG while also increasing the weight. Yesterday at our forward-most test, the CG was located at the arm of the front seats. We started the day by making a trip to Tractor Supply. The problem with ballasting up an airplane of this size is it takes a lot of weight. Who knew that this kind of flight testing was such a workout? The store was out of concrete bags but they had some nice gravel and sand tubes that weighed 60 pounds each. We actually weighed each one and wrote down the true weight, which varied from 60.5 to 63 pounds. I tied down three of these in the back seat and departed Collin's for the airport, while Collin drove the rest over to the big airport. Bob wanted us to measure the gear spread at each load, so that we could make sure they did not spread beyond his 74 inch limit, center of one tire to the other. At the first flight we were around 70 inches. We added three more bags to the back seat, for a total of 360 pounds, and flew it again. The handling was slowly changing, in my opinion for the better. I think the heavier wing loading gave it a nicer rhythm in the air when I encountered the occasional bump, and it was easier to land and taxi. Next we added 60 pounds in the center of the baggage area, and 125 more pounds under the rear seat. This put the total rear seat weight at 485 pounds, and gross airplane weight at 2685. It flew fine, so we added another 60 pounds in the baggage for a total of 120, and another 60 pounds at the feet of the rear seat. Then we refueled, adding an extra 210 pounds of gas for a total airplane weight of 3019.7. That was aft of Bob's planned limit by a quarter percent MAC. With all of that on board, the takeoff roll doubled, to around 500 feet. The rate of climb, which had usually been a solid 1500 feet per minute, eroded to a paltry 1000 feet per minute at 90 knots indicated. The gear spread had reached 72 inches, leaving a significant margin for less than perfect landings. At that weight I flew some pitch stability tests. At all speeds it still had positive static pitch stability, but at speeds over around 100mph it did not have positive dynamic stability. But it was still very flyable, and did not require a high level of pilot attention or even full-time hands-on-the-stick flying. I was able to find a high spot in the overcast to repeat the stall series and found no appreciable change to the stall characteristics vs the forward loadings. This thing flies like a Bearhawk should, it just carries more, has more room, and has just absurd thrust. The engine is rated for 315 HP, and fully loaded, here are some preliminary indicated airspeeds at 2000 feet:
19" and 1900 RPM, 6.9 GPH 110 mph IAS (leaned)
23.2" and 2450 RPM, 14.3 GPH and 145 mph IAS (leaned)
26.6" (WOT) and 2440 RPM, full rich mixture, 28.6 GPH, 158 mph IAS
At the heavy weight, the landing roll without aggressive braking (it's not my airplane) was 750-1000 feet. No doubt it could be trimmed to 500-750 just by a more ambitious pilot.
So all of that was before lunch. We decided to celebrate by eating a nice big restaurant meal, something I haven't done in 10 weeks since my home state hasn't allowed it as Missouri has.
After lunch, we had a visit from Bearhawk builder Andrew L. and his delightful family. What we were really needing was a clear enough sky that would allow me to get up to 7500 feet for some cruise performance testing. The sky looked open enough to give it a try, so I removed much of the weight to reach a mere 2660 pounds gross, which is basically four people and no bags other than the steel ballast. I figured this would be a good middle-of-the-road testing weight, and indeed it is right in the middle of our lightest flight weight so far and our heaviest. The clouds were broken up enough to make a safe climb, so I was able to get at least three readings on four headings for 140, 150, 130, and 70 mph IAS. I have not yet had a chance to crunch these to see what they were yielding in CAS and TAS but will do that next. I started doing some glide tests to collect the best glide speed for the bootstrap spreadsheet, but after 7 runs the fuel load was getting down a little, and the clouds were spreading out more than I liked, so I descended back underneath and landed for fuel. After the short hop back home to Collin's we found a mechanical problem with the tailwheel, which spelled a possible end to the flying for this week. Thankfully Collin is as good of a mechanic as you expect him to be, and he found that we were able to fix it without any new parts. Turns out the axle bearings on the tundra tailwheel are directional, and these had been installed backwards, allowing one of the races to pop out. We removed the tailwheel and cleaned it all up, flipped the bearings, and now everything is all lubed up and ready to go for tomorrow. But the forecast is for low barely VFR ceilings again. Fine for landing practice and load testing, but no good for bootstrap glides or more cruise testing. Maybe I'll be able to make some progress with video editing.
I have nearly all of these flights on video, and today Collin recorded around 25 minutes of talking about what it was like to build the airplane. Once I can get some of this edited down I'll post it on the Bearhawk Aircraft youtube channel. Collin also shared all of his build pictures, including some great details about some of the cool innovations that he, Bob, and Mark have employed to bring this beautiful bird off of the plans page an into the sky.
The airplane has exceeded my expectations, and I'm honored to have a chance to get some time in it.
So having said all of that, I have a few more days with the airplane. There are 11.3 hours on the meter, and all of Bob's safety tests are complete. What flying would you like to see, what data would you like to have, and what questions do you have for Collin or Bob?
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