EAA Chapter 524 - December 2023 Presentation No less than three chapter members are currently building the same aircraft. Find out what makes this model so enticing.
Very competent video editing, given three very different presentation styles and supporting graphics. Anyone that has done a video project of this nature knows how much work was required, and the talent and skill needed to produce a video package of this nature. Lessons learned? Bearhawks are pretty cool and Chapter 524's presentation team and video editor(s) are top notch.
Carlo's scratch-built project is moving pretty quickly... since receiving his plans in Sep 2023, one wing is skinned and the other is getting close to closing out, so under a year to get the toughest part of the airplane built from plans. And that is with a significant number of mods and improvements, including wet wing, capacitance fuel level, CNC milled inspection ports (no rim inside the wing, so no knuckle-busting nutplates), and the usual optimized weldments, etc.
7:40 the issue I have always objected to, is the numbers on their website for stall speeds would require lift coefficients greater than 3, after factoring in even a small tail down-load; OR reducing the aircraft weight to its listed empty weight, plus 150-200lbs if using a believable CLmax of 1.7-1.9 for a typical partial span flap, rag and tube aircraft. I'm not knocking the design or designer. It clearly works well for countless people. But it raises alarm bells to publish nonsensical data that was clearly read off an uncalibrated airspeed indicator/pitot by someone who should know better. Or worse; derived from make believe. I highly doubt these aircraft can actually achieve, in no wind conditions, on a 59 degree day, at 0MSL, the claimed 32mph, 35mph, 36, and 38mph stall speeds they list for various models online. The dynamic pressure at 35mph is so laughably low, even ultralights have a hard time operating there. E.g. Patrol is as of today published 2,000gross weight (that by definition is the weight performance numbers are derived for). And 180ft^2 wing. 2k/180 = 11.111...lb/sqft. (22/15)x 36mph stall = 52.8ft/s Rho is 0.002377 0.5*rho(V^2) is 3.3135 lbs/ft of dynamic pressure. (Q) 11.111.../q = CLmax of 3.353. Not even with a Helio Courier could you ever achieve that CLmax! (And it came close, with full span deployable slats, and 70% span flaps. It achieved a phenomenal CL~3.0 in practice)... Run numbers backwards and use CLmax of 1.8 (Same as Super cub, Vans RV-8. Not Husky, which has better, gnarly slotted flaps). And you find a stall speed of 49mph. This is at aft-cg of course, as fwd Ch means a larger tail download that would raise stall speed to 50mph even. A far cry from 36! (Which would correspond to a gross weight of 1,073lbs. Which is exactly -77lbs BELOW its listed empty weight).😂 Even if You plug in a Clmax of 2. Same story, you cant even bring fuel with your own bodyweight and achieve those stall speeds. Use a giant (unbelievable favorable) CLmax of 2.5. Then it gives you a low fuel, solo weight that might be useful for STOL competitions. (341lbs, including pilot, oil, and fuel, 36mph stall with CLmax of 2.5). This "accusation" is evidenced by the fact people aren't using these in STOL drags. Yet many other known STOL or bush designs are showing up in droves. Including carbon cubs, Zeniths, as well as C180s. But not many bearhawks showing up, let alone winning those events. If these vitally important performance numbers are this egregiously fudged. I wonder what other, much harder to verify numbers are pencil whipped?
52% span x1/3 chord plain flap on the patrol - they are barn doors compared with the PA-18's ~35% x 1/4c. Not a rag wing airplane - flush-riveted, stressed skin, single strut with fabric control surfaces (as in most high performance aircraft through the middle of WW2). Fabric control surfaces are more structurally efficient in design speed range and the aerodynamics are virtually the same as heavier stress-skin construction. Flush riveted Riblett wing matters a lot at cruise and less at the low end, but helps a bit on controlling separation. Some builders have gone with VGs and given up a few mph on the top end, but I suspect the consensus is that VGs add predictability in less-than-ideal conditions, versus trimming the Vso number in a meaningful way. Most manufacturers quote Vso (velocity - stall in landing config for the casual reader) at something other than max gross. A 1000 lb Patrol (Bob's O-320 fixed pitch prototype) with 185 lb pilot and 2.5 gallons usable left (thus about 1200 lb at landing) will stall at 36.5 mph CAS per the flight test data. A more realistic 195 hp CS on a Patrol with a decent panel will tip the scales closer to 1200 lbs empty weight, and with 312 lbs of fuel, 400 lbs of meat, and 85 lbs of baggage, Vso is now 47.2 mph CAS at 2000 lb (max gross on wheels/skis). Could I find another 5 mph by adding slotted, double slotted, or other higher lift config? Yup. For 99.9% of missions flown, would I be happy with the weight gain, the airspeed loss, and the additional mechanical complexity, maintenance, and added failure modes? Not so much. I'm concerned with - and I suspect most folks looking at the 'hawks versus other options - is speed range. For my config (195 hp/two-bladed CS prop), I'll see Vso around 45 mph for most missions and max cruise of 150 or more if I can pay the gas bill. If I throttle back to 135, I'll see about 7.5 gallon/hr burn and about 6.5 hrs duration with reserves for just under 900 miles zero-wind range. In a nutshell, that is the value proposition, versus slogging along 40 mph slower with a max range of 500 miles, but enjoying the fantasy that I too can win a STOL competition. If STOL drag is your jam, get an airplane optimized for the job (land slow/cruise slow), then mod the shit out of it. For the rest of us that are content to get into and out of 800 foot farm and ranch strips, but still cruise at 172/182 speeds, the Bearhawks are fit to mission. After flying helos for 30 years in the military and civil world, landing super short has little novelty, but dropping in on friends in Florida or NE Ohio with farm strips after a doable day of flying without breaking the bank can be fun... Bearhawks in STOL Drag? Might see them. 13,000+ PA-18 and clones out there and something like 200 or less flown in competition. With a couple hundred 'hawks flying, we might expect to see a couple at some point. That said, I suspect you are more likely to see a Bearhawk bouncing around back-country strips with the local group of PA-18 clones, Maules, and tailwheel Cessnas.
Thank you for posting this!
Very competent video editing, given three very different presentation styles and supporting graphics. Anyone that has done a video project of this nature knows how much work was required, and the talent and skill needed to produce a video package of this nature. Lessons learned? Bearhawks are pretty cool and Chapter 524's presentation team and video editor(s) are top notch.
Wow! What a HUGE project!
Carlo's scratch-built project is moving pretty quickly... since receiving his plans in Sep 2023, one wing is skinned and the other is getting close to closing out, so under a year to get the toughest part of the airplane built from plans. And that is with a significant number of mods and improvements, including wet wing, capacitance fuel level, CNC milled inspection ports (no rim inside the wing, so no knuckle-busting nutplates), and the usual optimized weldments, etc.
7:40 the issue I have always objected to, is the numbers on their website for stall speeds would require lift coefficients greater than 3, after factoring in even a small tail down-load; OR reducing the aircraft weight to its listed empty weight, plus 150-200lbs if using a believable CLmax of 1.7-1.9 for a typical partial span flap, rag and tube aircraft.
I'm not knocking the design or designer. It clearly works well for countless people. But it raises alarm bells to publish nonsensical data that was clearly read off an uncalibrated airspeed indicator/pitot by someone who should know better. Or worse; derived from make believe.
I highly doubt these aircraft can actually achieve, in no wind conditions, on a 59 degree day, at 0MSL, the claimed 32mph, 35mph, 36, and 38mph stall speeds they list for various models online.
The dynamic pressure at 35mph is so laughably low, even ultralights have a hard time operating there.
E.g. Patrol is as of today published 2,000gross weight (that by definition is the weight performance numbers are derived for). And 180ft^2 wing.
2k/180 = 11.111...lb/sqft.
(22/15)x 36mph stall = 52.8ft/s
Rho is 0.002377
0.5*rho(V^2) is 3.3135 lbs/ft of dynamic pressure. (Q)
11.111.../q = CLmax of 3.353.
Not even with a Helio Courier could you ever achieve that CLmax! (And it came close, with full span deployable slats, and 70% span flaps. It achieved a phenomenal CL~3.0 in practice)...
Run numbers backwards and use CLmax of 1.8 (Same as Super cub, Vans RV-8. Not Husky, which has better, gnarly slotted flaps). And you find a stall speed of 49mph. This is at aft-cg of course, as fwd Ch means a larger tail download that would raise stall speed to 50mph even. A far cry from 36! (Which would correspond to a gross weight of 1,073lbs. Which is exactly -77lbs BELOW its listed empty weight).😂
Even if You plug in a Clmax of 2. Same story, you cant even bring fuel with your own bodyweight and achieve those stall speeds. Use a giant (unbelievable favorable) CLmax of 2.5. Then it gives you a low fuel, solo weight that might be useful for STOL competitions. (341lbs, including pilot, oil, and fuel, 36mph stall with CLmax of 2.5).
This "accusation" is evidenced by the fact people aren't using these in STOL drags. Yet many other known STOL or bush designs are showing up in droves. Including carbon cubs, Zeniths, as well as C180s. But not many bearhawks showing up, let alone winning those events.
If these vitally important performance numbers are this egregiously fudged. I wonder what other, much harder to verify numbers are pencil whipped?
52% span x1/3 chord plain flap on the patrol - they are barn doors compared with the PA-18's ~35% x 1/4c. Not a rag wing airplane - flush-riveted, stressed skin, single strut with fabric control surfaces (as in most high performance aircraft through the middle of WW2). Fabric control surfaces are more structurally efficient in design speed range and the aerodynamics are virtually the same as heavier stress-skin construction. Flush riveted Riblett wing matters a lot at cruise and less at the low end, but helps a bit on controlling separation. Some builders have gone with VGs and given up a few mph on the top end, but I suspect the consensus is that VGs add predictability in less-than-ideal conditions, versus trimming the Vso number in a meaningful way.
Most manufacturers quote Vso (velocity - stall in landing config for the casual reader) at something other than max gross. A 1000 lb Patrol (Bob's O-320 fixed pitch prototype) with 185 lb pilot and 2.5 gallons usable left (thus about 1200 lb at landing) will stall at 36.5 mph CAS per the flight test data. A more realistic 195 hp CS on a Patrol with a decent panel will tip the scales closer to 1200 lbs empty weight, and with 312 lbs of fuel, 400 lbs of meat, and 85 lbs of baggage, Vso is now 47.2 mph CAS at 2000 lb (max gross on wheels/skis).
Could I find another 5 mph by adding slotted, double slotted, or other higher lift config? Yup. For 99.9% of missions flown, would I be happy with the weight gain, the airspeed loss, and the additional mechanical complexity, maintenance, and added failure modes? Not so much. I'm concerned with - and I suspect most folks looking at the 'hawks versus other options - is speed range. For my config (195 hp/two-bladed CS prop), I'll see Vso around 45 mph for most missions and max cruise of 150 or more if I can pay the gas bill. If I throttle back to 135, I'll see about 7.5 gallon/hr burn and about 6.5 hrs duration with reserves for just under 900 miles zero-wind range. In a nutshell, that is the value proposition, versus slogging along 40 mph slower with a max range of 500 miles, but enjoying the fantasy that I too can win a STOL competition. If STOL drag is your jam, get an airplane optimized for the job (land slow/cruise slow), then mod the shit out of it. For the rest of us that are content to get into and out of 800 foot farm and ranch strips, but still cruise at 172/182 speeds, the Bearhawks are fit to mission. After flying helos for 30 years in the military and civil world, landing super short has little novelty, but dropping in on friends in Florida or NE Ohio with farm strips after a doable day of flying without breaking the bank can be fun...
Bearhawks in STOL Drag? Might see them. 13,000+ PA-18 and clones out there and something like 200 or less flown in competition. With a couple hundred 'hawks flying, we might expect to see a couple at some point. That said, I suspect you are more likely to see a Bearhawk bouncing around back-country strips with the local group of PA-18 clones, Maules, and tailwheel Cessnas.