Shameless update from Dale Kramer

Mercy sakes Tom give it a rest. Nobody is really interested in your analysis least of all anyone who is interested in donating to this project. They will get their info direct from the designer (dale) and will perform their due diligence with folks who specialize in these matters, certainly not from the many times dingleberry comments found in a site like this one. Your really not doing anyone a service debating this topic, its just more stiring of the crap pot.

On Wednesday, March 30, 2016 at 8:54:53 PM UTC-7, 2G wrote:
On Wednesday, March 30, 2016 at 4:34:36 PM UTC-7, Andy Blackburn wrote:
I am hesitant to reply, because you make it so not fun, but here goes. I combined your last two posts to make it easier.

I don't think you are an aeronautical engineer either by education (I am times 2 and Dale is by 3/4 of a degree) or by practice (Dale certainly is - he sold a bunch of the LSA he designed). We can quibble about what is or isn't adequate qualification for this sort of contraption. You have a science/engineering background so that will get you some ways, but aircraft design has a bit of art in it - especially for something like what Dale is trying. No one can say for sure how well it will work - which is why a scale model seems prudent. The design is unusual, based on some of the new, large brushless electric motors that are available now so it's an interesting use of evolving technologies.

On Tuesday, March 22, 2016 at 8:20:12 PM UTC-7, 2G wrote:
On Tuesday, March 22, 2016 at 4:02:40 AM UTC-7, DaleKramer wrote:
Looks like this is the kind of project that gets funded nowadays on Kickstarter, the world will be such a better place

https://www.kickstarter.com/projects...?ref=discovery

I will apologize for using the word "stinking" - I will let your attitude speak for itself.

That said, this design is problematic. For example, you list the battery weight at 25 lb. I calculate that you will need about 100 lbs of battery (batteries cannot be discharged 100% and expect any decent lifetime). And that ONLY allows by your statement, 3-4 min of hovering. This is totally inadequate for any landing I would dare attempt. This means you will need MUCH more battery capacity than you allowed for, but I will stick to this time for the rest of the analysis.

Fine -

Using freely available references, I calculated the ideal power to hover at sea level (not climb, mind you) at 131 hp with a MTOW of 1175 lb. Using a 0.75 FOM this increases to 175 hp. At a 10,000 ft density altitude this becomes 158 and 211 hp, respectively. Clearly your design is severely under powered. It gets worse when you want to climb and be able to transition from hovering to forward flight, when some of the electric motors will have to be shut down. These same references state that VTOL aircraft have a horsepower loading of less than 2: you are more than double this.

Be careful about translating between thrust and horsepower for a mix of gas-piston and brushless DC motors. They have very different characteristics and I don't believe Dale quoted HP on the electrics. Their output doesn't vary with altitude since the aren't aspirated.


I am not confused about fore and aft. The pilot is faced forward in forward flight; his position must change to an aft facing position AND rotate 90 degrees. That amounts to 2 rotations on 2 axes of 90 and 180 degrees. When, exactly does this occur, while travelling forward in level flight or while hovering? I would assume hovering because of the extreme air blast and speed brake effect. While hovering the pilot WILL be exposed to the full thrust of the main motor. The thought of attempting such a maneuver scares the hell out of me! The potential of vertigo is not just huge - it is virtually certain. Another point that went unanswered.

Look at the picture again - as the airplane pitches up 90 degrees to go into hover the pilot's seated position rotates the opposite direction, pitching his legs down 90 degrees through the bottom of the fuselage. In essence the pilot's pitch attitude remains unchanged relative to Earth frame of reference as the aircraft pitches up around him.


Andy makes excellent points about the counter-rotation and stability issues. As currently envisioned, the main motor cannot be operated at full power because the electric motors would not stabilize its torque. This problem is exacerbated when the aircraft tries to transition to horizontal flight when half the electric motors would have to be shut down. Combine an electric motor failure and you have a real problem. Notice that Dale never answered my question about thrust vectoring.

Static versus dynamic tourque. You'll get some from the friction in the propulsion system and more from dynamic application of power. Dale mentioned that canting the electric motors counteracts static torque and if they are canted properly you will get some counter-torque as you apply thrust to the all engines in unison. I can't tell you how much canting of the thrust vector is enough. Presumably there is an optimum angle and it will affect how you apply power across all propulsion systems. It's impossible for me to say whether this will represent a serious control or performance restriction.

Electric motor failure is a concern, but with 4-6 operating at least you have some redundancy since you can't autorotate.

Fly by wire? You have just become a million dollar aircraft! This is completely unrealistic. You REALLY need to consult with engineers who have ACTUALLY designed fly by wire aircraft.

My helicopter drone is fly by wire - it really depends on what you mean by fly by wire. I doubt Dale meant electronically controlled hydraulic actuators on the aerodynamic control surfaces, which would add to cost and weight. I suspect he meant engine controls, which is not a big deal since electric motors are by definition electronically controlled.

Qualifications are not important? Since the hell when? Building conventional aircraft from who knows what designs is NOT a representation of qualifications. I am approaching this whole project from the viewpoint of an unsophisticated investor; I don't particularly care what Dale does with his own money. BTW, there WERE NO aeronautical engineering schools at the time of the Wright Brothers; they invented it (they also used their OWN money!)

Dale is plenty experienced - asking for his sheepskin is a bit much. It's not like he's hiding anything. He's been transparent about his background and experience. People need not invest if senior year in college is more important to them than having designed and flown hundreds of examples of an aircraft.

Has NO ONE come forward to challenge my calculations? It has been 3 days and the only rebuttal had something weird to do about having dinner of molds.

Okay, I DID leave something out, and I admit it. I forgot to mention that horsepower from carbureted engines falls off with altitude, so that 100 hp engine will only produce 70 hp at a 10,000 ft DENSITY altitude.

Okay. Maybe get it working at sea level first. Guys in Telluride may have to wait.

Here is another factoid that you will find if you bother to check my calculations: power required is INVERSELY proportional to the square root of disk area. This is simple physics, so there is NO avoiding it! Consequently, tail squatters require A LOT more horsepower. Dale's design will require nearly THREE TIMES more horsepower than an R22 simply because of the MUCH higher disk loading - that is WHY I made such a point of the HIGH disk loading. I don't have ANY idea where Dale came up with the number of 1.3X thrust to weight, maybe it was in a dream. It seems like engineering analysis is, at best, an after thought. During my career as a design engineer I can assure you we thought of it otherwise.

I think you are confusing thrust and horsepower. 1.3 thrust to weight isn't a hot rod, but it ought to get off the ground and accelerate reasonably (about 0.3 G), or 10 ft/s/s.



Here is an interesting quote I dug up from the book by Ray Prouty (Dale, I assume that you ARE reading the reference books):

"Despite the trend for higher and higher disc loadings in the past 20 years, there does seem to be a practical upper limit. Values of more than about 10 pounds per square foot generate such high induced velocities under the rotor that it is difficult to operate from unprepared sites without filling the air full of flying sticks and stones to break one's bones. It also becomes increasingly difficult to obtain safe autorotational characteristics as disc loadings go up. These are two reasons why VTOL aircraft that depend on heavily loaded propellers for hovering have not yet become operational."

And Dale wants the pilot sitting out in the open to be pelted by those sticks and stones. Whatever...

It's already been conceded that higher disk loading is less efficient, but for a few minutes of flight, efficiency is not the main concern. As long as the electric motors and props, plus gas engine/prop can deliver enough thrust, the thing should fly. The main purpose of all these designs is to produce a VTOL aircraft that isn't limited the way conventional helicopters are with regard to cruise speed (due to retreating blade stall). That generally means compromising on the efficiency of the vertical lift parts to optimize the whole contraption for cruise speed and efficiency. Dale's design seems like a decent effort at that.

Fire away.

9B

First, you either have a degree or you don't. You say you do, I respect that. This was brought up totally out of concern for potential investors who deserve to know the qualifications of the team involved. Dale has said he is not a degreed engineer, enough said. I am not an aeronautical engineer, either (but I am not requesting public funding for anything).

HP was calculated because that is how aeronautical engineers approach the problem (I can provide references on request). I simply followed what was clearly explained in these references. HP is required to move an air mass necessary to support the helicopter in hover. Thrust would be more appropriate when dealing with engines rated for thrust (which reciprocating engines are not). I calculated HP based on readily available references by aeronautical engineers. I did make one mistake, however. I used a FOM (figure of merit) of 0.75; this is WAY TOO HIGH for a VTOL (I am surprised you didn't catch it). A realistic FOM will be no higher than 0.5, probably less. This will increase the HP required proportionally. At sea level 190 hp is required just to hover; 247 hp to achieve the 1.3x figure mentioned by Dale.

You didn't challenge any of these HP calculations, just said that thrust is different from HP. Do you agree with my calculations or not? If not, post the correct calculations. I have a spreadsheet I can send you offline.

The electric motors are countering the torque of the gas engine; if the gas engine HP drops so must the electric motors or the aircraft will begin spinning.

HP (for gas engines) decreases with density altitude. If an aircraft can ONLY be flown at sea level it is not much of an aircraft!

Failure of one electric motor means a 2nd motor must be shut down for thrust balancing (as I see it).

No mention has been made of how this thing will control lateral movement while hovering (as is necessary to land on a specific spot). The only way I see this can be done is thru thrust vectoring, which will interact with vertical balancing. To rotate the aircraft while hovering (easy to do with a helicopter) will require decreasing RPMs on either the electric motors or the gas engine, either of which will interact with hovering. This will require a computer to mix these controls and the gas engine will have to be FADEC, not something you see on 912s.

The design is very top-heavy with the gas engine at the highest point. This makes the design very sensitive to wind gusts and the potential to topple over.

I had to look at the drawings several times to figure out what was happening. Not because it wasn't there, but because 1) there were differences between several drawings and 2) the whole concept of the pilot pivoting out of the bottom of the aircraft is so foreign. I will repeat: the pilot will be exposed to high velocity prop wash during takeoff and landing. This will be VERY disorientating (I wouldn't want to fly it!). The fuselage will have 2 very large openings directly opposite of each other; making it strong enough and stiff enough to support flight loads will be extremely challenging. Getting the bottom pan to seal will also be challenging.

Dale said moving the controls was not a problem because it was fly by wire. He is an experienced aircraft builder and I assume he knows what fly by wire means.

I am not interested in skewering anybody; I just want to get to the truth of the matter. It is far better to find the faults with an idea up front and either fix them or trash can it before a lot of time and money are invested in it.

Tom


My prior reservations about engaging on this have been confirmed.

I welcome a good rational debate in the spirit of learning something new - and I am sure you think you are making salient points Tom, but what people not inside your head are seeing is this:

https://www.youtube.com/watch?v=hnTmBjk-M0c

I wish I could be more helpful, but I can see where this is going. It's a familiar road. At least I was able to clear up the nutating pilot matter. ;-)

Hope you get to build the model Dale. It's an interesting experiment worth my $100.

9B

Golly a guy named Will Schumann, was not a degreed aeronautical engineer either. Wonder why in the 80's all the wing platforms went from a straight leading edge and a tapered trailing edge to a tapered leading edge and a straight trailing edge. It was not the design work of famous engineers with university wind tunnels. Just a really smart guy who watched some soaring birds fly and realized the taper of their leading edge looked like a good design (God designed). Just saying. While I certainly am an advocate for higher education, nothing beats being sharp.


On Wednesday, March 30, 2016 at 10:36:34 PM UTC-7, Andy Blackburn wrote:
On Wednesday, March 30, 2016 at 8:54:53 PM UTC-7, 2G wrote:
On Wednesday, March 30, 2016 at 4:34:36 PM UTC-7, Andy Blackburn wrote:
I am hesitant to reply, because you make it so not fun, but here goes.. I combined your last two posts to make it easier.

I don't think you are an aeronautical engineer either by education (I am times 2 and Dale is by 3/4 of a degree) or by practice (Dale certainly is - he sold a bunch of the LSA he designed). We can quibble about what is or isn't adequate qualification for this sort of contraption. You have a science/engineering background so that will get you some ways, but aircraft design has a bit of art in it - especially for something like what Dale is trying. No one can say for sure how well it will work - which is why a scale model seems prudent. The design is unusual, based on some of the new, large brushless electric motors that are available now so it's an interesting use of evolving technologies.

On Tuesday, March 22, 2016 at 8:20:12 PM UTC-7, 2G wrote:
On Tuesday, March 22, 2016 at 4:02:40 AM UTC-7, DaleKramer wrote:
Looks like this is the kind of project that gets funded nowadays on Kickstarter, the world will be such a better place

https://www.kickstarter.com/projects...?ref=discovery

I will apologize for using the word "stinking" - I will let your attitude speak for itself.

That said, this design is problematic. For example, you list the battery weight at 25 lb. I calculate that you will need about 100 lbs of battery (batteries cannot be discharged 100% and expect any decent lifetime). And that ONLY allows by your statement, 3-4 min of hovering. This is totally inadequate for any landing I would dare attempt. This means you will need MUCH more battery capacity than you allowed for, but I will stick to this time for the rest of the analysis.

Fine -

Using freely available references, I calculated the ideal power to hover at sea level (not climb, mind you) at 131 hp with a MTOW of 1175 lb. Using a 0.75 FOM this increases to 175 hp. At a 10,000 ft density altitude this becomes 158 and 211 hp, respectively. Clearly your design is severely under powered. It gets worse when you want to climb and be able to transition from hovering to forward flight, when some of the electric motors will have to be shut down. These same references state that VTOL aircraft have a horsepower loading of less than 2: you are more than double this.

Be careful about translating between thrust and horsepower for a mix of gas-piston and brushless DC motors. They have very different characteristics and I don't believe Dale quoted HP on the electrics. Their output doesn't vary with altitude since the aren't aspirated.


I am not confused about fore and aft. The pilot is faced forward in forward flight; his position must change to an aft facing position AND rotate 90 degrees. That amounts to 2 rotations on 2 axes of 90 and 180 degrees.. When, exactly does this occur, while travelling forward in level flight or while hovering? I would assume hovering because of the extreme air blast and speed brake effect. While hovering the pilot WILL be exposed to the full thrust of the main motor. The thought of attempting such a maneuver scares the hell out of me! The potential of vertigo is not just huge - it is virtually certain. Another point that went unanswered.

Look at the picture again - as the airplane pitches up 90 degrees to go into hover the pilot's seated position rotates the opposite direction, pitching his legs down 90 degrees through the bottom of the fuselage. In essence the pilot's pitch attitude remains unchanged relative to Earth frame of reference as the aircraft pitches up around him.


Andy makes excellent points about the counter-rotation and stability issues. As currently envisioned, the main motor cannot be operated at full power because the electric motors would not stabilize its torque. This problem is exacerbated when the aircraft tries to transition to horizontal flight when half the electric motors would have to be shut down. Combine an electric motor failure and you have a real problem. Notice that Dale never answered my question about thrust vectoring.

Static versus dynamic tourque. You'll get some from the friction in the propulsion system and more from dynamic application of power. Dale mentioned that canting the electric motors counteracts static torque and if they are canted properly you will get some counter-torque as you apply thrust to the all engines in unison. I can't tell you how much canting of the thrust vector is enough. Presumably there is an optimum angle and it will affect how you apply power across all propulsion systems. It's impossible for me to say whether this will represent a serious control or performance restriction.

Electric motor failure is a concern, but with 4-6 operating at least you have some redundancy since you can't autorotate.

Fly by wire? You have just become a million dollar aircraft! This is completely unrealistic. You REALLY need to consult with engineers who have ACTUALLY designed fly by wire aircraft.

My helicopter drone is fly by wire - it really depends on what you mean by fly by wire. I doubt Dale meant electronically controlled hydraulic actuators on the aerodynamic control surfaces, which would add to cost and weight. I suspect he meant engine controls, which is not a big deal since electric motors are by definition electronically controlled.

Qualifications are not important? Since the hell when? Building conventional aircraft from who knows what designs is NOT a representation of qualifications. I am approaching this whole project from the viewpoint of an unsophisticated investor; I don't particularly care what Dale does with his own money. BTW, there WERE NO aeronautical engineering schools at the time of the Wright Brothers; they invented it (they also used their OWN money!)

Dale is plenty experienced - asking for his sheepskin is a bit much. It's not like he's hiding anything. He's been transparent about his background and experience. People need not invest if senior year in college is more important to them than having designed and flown hundreds of examples of an aircraft.

Has NO ONE come forward to challenge my calculations? It has been 3 days and the only rebuttal had something weird to do about having dinner of molds.

Okay, I DID leave something out, and I admit it. I forgot to mention that horsepower from carbureted engines falls off with altitude, so that 100 hp engine will only produce 70 hp at a 10,000 ft DENSITY altitude.

Okay. Maybe get it working at sea level first. Guys in Telluride may have to wait.

Here is another factoid that you will find if you bother to check my calculations: power required is INVERSELY proportional to the square root of disk area. This is simple physics, so there is NO avoiding it! Consequently, tail squatters require A LOT more horsepower. Dale's design will require nearly THREE TIMES more horsepower than an R22 simply because of the MUCH higher disk loading - that is WHY I made such a point of the HIGH disk loading. I don't have ANY idea where Dale came up with the number of 1.3X thrust to weight, maybe it was in a dream. It seems like engineering analysis is, at best, an after thought. During my career as a design engineer I can assure you we thought of it otherwise.

I think you are confusing thrust and horsepower. 1.3 thrust to weight isn't a hot rod, but it ought to get off the ground and accelerate reasonably (about 0.3 G), or 10 ft/s/s.



Here is an interesting quote I dug up from the book by Ray Prouty (Dale, I assume that you ARE reading the reference books):

"Despite the trend for higher and higher disc loadings in the past 20 years, there does seem to be a practical upper limit. Values of more than about 10 pounds per square foot generate such high induced velocities under the rotor that it is difficult to operate from unprepared sites without filling the air full of flying sticks and stones to break one's bones. It also becomes increasingly difficult to obtain safe autorotational characteristics as disc loadings go up. These are two reasons why VTOL aircraft that depend on heavily loaded propellers for hovering have not yet become operational."

And Dale wants the pilot sitting out in the open to be pelted by those sticks and stones. Whatever...

It's already been conceded that higher disk loading is less efficient, but for a few minutes of flight, efficiency is not the main concern. As long as the electric motors and props, plus gas engine/prop can deliver enough thrust, the thing should fly. The main purpose of all these designs is to produce a VTOL aircraft that isn't limited the way conventional helicopters are with regard to cruise speed (due to retreating blade stall). That generally means compromising on the efficiency of the vertical lift parts to optimize the whole contraption for cruise speed and efficiency. Dale's design seems like a decent effort at that.

Fire away.

9B

First, you either have a degree or you don't. You say you do, I respect that. This was brought up totally out of concern for potential investors who deserve to know the qualifications of the team involved. Dale has said he is not a degreed engineer, enough said. I am not an aeronautical engineer, either (but I am not requesting public funding for anything).

HP was calculated because that is how aeronautical engineers approach the problem (I can provide references on request). I simply followed what was clearly explained in these references. HP is required to move an air mass necessary to support the helicopter in hover. Thrust would be more appropriate when dealing with engines rated for thrust (which reciprocating engines are not). I calculated HP based on readily available references by aeronautical engineers. I did make one mistake, however. I used a FOM (figure of merit) of 0.75; this is WAY TOO HIGH for a VTOL (I am surprised you didn't catch it). A realistic FOM will be no higher than 0.5, probably less. This will increase the HP required proportionally. At sea level 190 hp is required just to hover; 247 hp to achieve the 1.3x figure mentioned by Dale.

You didn't challenge any of these HP calculations, just said that thrust is different from HP. Do you agree with my calculations or not? If not, post the correct calculations. I have a spreadsheet I can send you offline.

The electric motors are countering the torque of the gas engine; if the gas engine HP drops so must the electric motors or the aircraft will begin spinning.

HP (for gas engines) decreases with density altitude. If an aircraft can ONLY be flown at sea level it is not much of an aircraft!

Failure of one electric motor means a 2nd motor must be shut down for thrust balancing (as I see it).

No mention has been made of how this thing will control lateral movement while hovering (as is necessary to land on a specific spot). The only way I see this can be done is thru thrust vectoring, which will interact with vertical balancing. To rotate the aircraft while hovering (easy to do with a helicopter) will require decreasing RPMs on either the electric motors or the gas engine, either of which will interact with hovering. This will require a computer to mix these controls and the gas engine will have to be FADEC, not something you see on 912s.

The design is very top-heavy with the gas engine at the highest point. This makes the design very sensitive to wind gusts and the potential to topple over.

I had to look at the drawings several times to figure out what was happening. Not because it wasn't there, but because 1) there were differences between several drawings and 2) the whole concept of the pilot pivoting out of the bottom of the aircraft is so foreign. I will repeat: the pilot will be exposed to high velocity prop wash during takeoff and landing. This will be VERY disorientating (I wouldn't want to fly it!). The fuselage will have 2 very large openings directly opposite of each other; making it strong enough and stiff enough to support flight loads will be extremely challenging. Getting the bottom pan to seal will also be challenging.

Dale said moving the controls was not a problem because it was fly by wire. He is an experienced aircraft builder and I assume he knows what fly by wire means.

I am not interested in skewering anybody; I just want to get to the truth of the matter. It is far better to find the faults with an idea up front and either fix them or trash can it before a lot of time and money are invested in it.

Tom


My prior reservations about engaging on this have been confirmed.

I welcome a good rational debate in the spirit of learning something new - and I am sure you think you are making salient points Tom, but what people not inside your head are seeing is this:

https://www.youtube.com/watch?v=hnTmBjk-M0c

I wish I could be more helpful, but I can see where this is going. It's a familiar road. At least I was able to clear up the nutating pilot matter. ;-)

Hope you get to build the model Dale. It's an interesting experiment worth my $100.

9B

On Wednesday, March 30, 2016 at 10:36:34 PM UTC-7, Andy Blackburn wrote:
On Wednesday, March 30, 2016 at 8:54:53 PM UTC-7, 2G wrote:
On Wednesday, March 30, 2016 at 4:34:36 PM UTC-7, Andy Blackburn wrote:
I am hesitant to reply, because you make it so not fun, but here goes.. I combined your last two posts to make it easier.

I don't think you are an aeronautical engineer either by education (I am times 2 and Dale is by 3/4 of a degree) or by practice (Dale certainly is - he sold a bunch of the LSA he designed). We can quibble about what is or isn't adequate qualification for this sort of contraption. You have a science/engineering background so that will get you some ways, but aircraft design has a bit of art in it - especially for something like what Dale is trying. No one can say for sure how well it will work - which is why a scale model seems prudent. The design is unusual, based on some of the new, large brushless electric motors that are available now so it's an interesting use of evolving technologies.

On Tuesday, March 22, 2016 at 8:20:12 PM UTC-7, 2G wrote:
On Tuesday, March 22, 2016 at 4:02:40 AM UTC-7, DaleKramer wrote:
Looks like this is the kind of project that gets funded nowadays on Kickstarter, the world will be such a better place

https://www.kickstarter.com/projects...?ref=discovery

I will apologize for using the word "stinking" - I will let your attitude speak for itself.

That said, this design is problematic. For example, you list the battery weight at 25 lb. I calculate that you will need about 100 lbs of battery (batteries cannot be discharged 100% and expect any decent lifetime). And that ONLY allows by your statement, 3-4 min of hovering. This is totally inadequate for any landing I would dare attempt. This means you will need MUCH more battery capacity than you allowed for, but I will stick to this time for the rest of the analysis.

Fine -

Using freely available references, I calculated the ideal power to hover at sea level (not climb, mind you) at 131 hp with a MTOW of 1175 lb. Using a 0.75 FOM this increases to 175 hp. At a 10,000 ft density altitude this becomes 158 and 211 hp, respectively. Clearly your design is severely under powered. It gets worse when you want to climb and be able to transition from hovering to forward flight, when some of the electric motors will have to be shut down. These same references state that VTOL aircraft have a horsepower loading of less than 2: you are more than double this.

Be careful about translating between thrust and horsepower for a mix of gas-piston and brushless DC motors. They have very different characteristics and I don't believe Dale quoted HP on the electrics. Their output doesn't vary with altitude since the aren't aspirated.


I am not confused about fore and aft. The pilot is faced forward in forward flight; his position must change to an aft facing position AND rotate 90 degrees. That amounts to 2 rotations on 2 axes of 90 and 180 degrees.. When, exactly does this occur, while travelling forward in level flight or while hovering? I would assume hovering because of the extreme air blast and speed brake effect. While hovering the pilot WILL be exposed to the full thrust of the main motor. The thought of attempting such a maneuver scares the hell out of me! The potential of vertigo is not just huge - it is virtually certain. Another point that went unanswered.

Look at the picture again - as the airplane pitches up 90 degrees to go into hover the pilot's seated position rotates the opposite direction, pitching his legs down 90 degrees through the bottom of the fuselage. In essence the pilot's pitch attitude remains unchanged relative to Earth frame of reference as the aircraft pitches up around him.


Andy makes excellent points about the counter-rotation and stability issues. As currently envisioned, the main motor cannot be operated at full power because the electric motors would not stabilize its torque. This problem is exacerbated when the aircraft tries to transition to horizontal flight when half the electric motors would have to be shut down. Combine an electric motor failure and you have a real problem. Notice that Dale never answered my question about thrust vectoring.

Static versus dynamic tourque. You'll get some from the friction in the propulsion system and more from dynamic application of power. Dale mentioned that canting the electric motors counteracts static torque and if they are canted properly you will get some counter-torque as you apply thrust to the all engines in unison. I can't tell you how much canting of the thrust vector is enough. Presumably there is an optimum angle and it will affect how you apply power across all propulsion systems. It's impossible for me to say whether this will represent a serious control or performance restriction.

Electric motor failure is a concern, but with 4-6 operating at least you have some redundancy since you can't autorotate.

Fly by wire? You have just become a million dollar aircraft! This is completely unrealistic. You REALLY need to consult with engineers who have ACTUALLY designed fly by wire aircraft.

My helicopter drone is fly by wire - it really depends on what you mean by fly by wire. I doubt Dale meant electronically controlled hydraulic actuators on the aerodynamic control surfaces, which would add to cost and weight. I suspect he meant engine controls, which is not a big deal since electric motors are by definition electronically controlled.

Qualifications are not important? Since the hell when? Building conventional aircraft from who knows what designs is NOT a representation of qualifications. I am approaching this whole project from the viewpoint of an unsophisticated investor; I don't particularly care what Dale does with his own money. BTW, there WERE NO aeronautical engineering schools at the time of the Wright Brothers; they invented it (they also used their OWN money!)

Dale is plenty experienced - asking for his sheepskin is a bit much. It's not like he's hiding anything. He's been transparent about his background and experience. People need not invest if senior year in college is more important to them than having designed and flown hundreds of examples of an aircraft.

Has NO ONE come forward to challenge my calculations? It has been 3 days and the only rebuttal had something weird to do about having dinner of molds.

Okay, I DID leave something out, and I admit it. I forgot to mention that horsepower from carbureted engines falls off with altitude, so that 100 hp engine will only produce 70 hp at a 10,000 ft DENSITY altitude.

Okay. Maybe get it working at sea level first. Guys in Telluride may have to wait.

Here is another factoid that you will find if you bother to check my calculations: power required is INVERSELY proportional to the square root of disk area. This is simple physics, so there is NO avoiding it! Consequently, tail squatters require A LOT more horsepower. Dale's design will require nearly THREE TIMES more horsepower than an R22 simply because of the MUCH higher disk loading - that is WHY I made such a point of the HIGH disk loading. I don't have ANY idea where Dale came up with the number of 1.3X thrust to weight, maybe it was in a dream. It seems like engineering analysis is, at best, an after thought. During my career as a design engineer I can assure you we thought of it otherwise.

I think you are confusing thrust and horsepower. 1.3 thrust to weight isn't a hot rod, but it ought to get off the ground and accelerate reasonably (about 0.3 G), or 10 ft/s/s.



Here is an interesting quote I dug up from the book by Ray Prouty (Dale, I assume that you ARE reading the reference books):

"Despite the trend for higher and higher disc loadings in the past 20 years, there does seem to be a practical upper limit. Values of more than about 10 pounds per square foot generate such high induced velocities under the rotor that it is difficult to operate from unprepared sites without filling the air full of flying sticks and stones to break one's bones. It also becomes increasingly difficult to obtain safe autorotational characteristics as disc loadings go up. These are two reasons why VTOL aircraft that depend on heavily loaded propellers for hovering have not yet become operational."

And Dale wants the pilot sitting out in the open to be pelted by those sticks and stones. Whatever...

It's already been conceded that higher disk loading is less efficient, but for a few minutes of flight, efficiency is not the main concern. As long as the electric motors and props, plus gas engine/prop can deliver enough thrust, the thing should fly. The main purpose of all these designs is to produce a VTOL aircraft that isn't limited the way conventional helicopters are with regard to cruise speed (due to retreating blade stall). That generally means compromising on the efficiency of the vertical lift parts to optimize the whole contraption for cruise speed and efficiency. Dale's design seems like a decent effort at that.

Fire away.

9B

First, you either have a degree or you don't. You say you do, I respect that. This was brought up totally out of concern for potential investors who deserve to know the qualifications of the team involved. Dale has said he is not a degreed engineer, enough said. I am not an aeronautical engineer, either (but I am not requesting public funding for anything).

HP was calculated because that is how aeronautical engineers approach the problem (I can provide references on request). I simply followed what was clearly explained in these references. HP is required to move an air mass necessary to support the helicopter in hover. Thrust would be more appropriate when dealing with engines rated for thrust (which reciprocating engines are not). I calculated HP based on readily available references by aeronautical engineers. I did make one mistake, however. I used a FOM (figure of merit) of 0.75; this is WAY TOO HIGH for a VTOL (I am surprised you didn't catch it). A realistic FOM will be no higher than 0.5, probably less. This will increase the HP required proportionally. At sea level 190 hp is required just to hover; 247 hp to achieve the 1.3x figure mentioned by Dale.

You didn't challenge any of these HP calculations, just said that thrust is different from HP. Do you agree with my calculations or not? If not, post the correct calculations. I have a spreadsheet I can send you offline.

The electric motors are countering the torque of the gas engine; if the gas engine HP drops so must the electric motors or the aircraft will begin spinning.

HP (for gas engines) decreases with density altitude. If an aircraft can ONLY be flown at sea level it is not much of an aircraft!

Failure of one electric motor means a 2nd motor must be shut down for thrust balancing (as I see it).

No mention has been made of how this thing will control lateral movement while hovering (as is necessary to land on a specific spot). The only way I see this can be done is thru thrust vectoring, which will interact with vertical balancing. To rotate the aircraft while hovering (easy to do with a helicopter) will require decreasing RPMs on either the electric motors or the gas engine, either of which will interact with hovering. This will require a computer to mix these controls and the gas engine will have to be FADEC, not something you see on 912s.

The design is very top-heavy with the gas engine at the highest point. This makes the design very sensitive to wind gusts and the potential to topple over.

I had to look at the drawings several times to figure out what was happening. Not because it wasn't there, but because 1) there were differences between several drawings and 2) the whole concept of the pilot pivoting out of the bottom of the aircraft is so foreign. I will repeat: the pilot will be exposed to high velocity prop wash during takeoff and landing. This will be VERY disorientating (I wouldn't want to fly it!). The fuselage will have 2 very large openings directly opposite of each other; making it strong enough and stiff enough to support flight loads will be extremely challenging. Getting the bottom pan to seal will also be challenging.

Dale said moving the controls was not a problem because it was fly by wire. He is an experienced aircraft builder and I assume he knows what fly by wire means.

I am not interested in skewering anybody; I just want to get to the truth of the matter. It is far better to find the faults with an idea up front and either fix them or trash can it before a lot of time and money are invested in it.

Tom


My prior reservations about engaging on this have been confirmed.

I welcome a good rational debate in the spirit of learning something new - and I am sure you think you are making salient points Tom, but what people not inside your head are seeing is this:

https://www.youtube.com/watch?v=hnTmBjk-M0c

I wish I could be more helpful, but I can see where this is going. It's a familiar road. At least I was able to clear up the nutating pilot matter. ;-)

Hope you get to build the model Dale. It's an interesting experiment worth my $100.

9B

My apologies: I thought you were actually interested in discussion the technical details of the design. I guess by your non-response my calculations are correct...

On Wednesday, March 30, 2016 at 10:02:46 PM UTC-7, wrote:
Mercy sakes Tom give it a rest. Nobody is really interested in your analysis least of all anyone who is interested in donating to this project. They will get their info direct from the designer (dale) and will perform their due diligence with folks who specialize in these matters, certainly not from the many times dingleberry comments found in a site like this one. Your really not doing anyone a service debating this topic, its just more stiring of the crap pot.

I am SO GLAD that you know what EVERYBODY else is thinking! Now we can just go to you to settle all controversies. BTW I HAD given it a rest until I thought that Andy was actually interested in the technical aspects. Maybe you should tell Andy to give it a rest also. Oh, I guess you just want critical commenters to take a rest. Maybe you can follow this up with a lecture on the First Amendment...

Sorry Tom - it was devolving into points that were narrower and narrower and mostly not relevant to the fundamental issues, seemingly so you can avoid conceding any points made by others.

There are some legitimate technical issues to figure out. I just don't see anything inherent in this that says the thing can't fly, and believe me helicopters of any type are full of issues. Might the thing benefit from more horsepower? Maybe. Might it kick up dust if you fly it off dry dirt and a bed of twigs? Probably. Will it hover at 10,000 MSL on a hot day? I'd bet a number of helicopters have trouble with that. Will it autorotate? Nope, but it has extra motors. Enough? Maybe, maybe not. Might it be a bit tippy with the motor up front? I think it might, but thinking that doesn't make it an insurmountable problem or Dale a charlatan.

When I worked on helicopters as an engineer at NASA Ames I saw all kinds of crazy crap that clever people made work, some with PhDs in Aero, some who were mechanics. It is the trying that drives progress. I give Dale credit for trying.

Major snip...

My apologies: I thought you were actually interested in discussion the
technical details of the design. I guess by your non-response my
calculations are correct...


They may be or they may not be, and if you're designing such a craft as Dale
Kramer is attempting, I've no doubt you can find qualified people to look over
your shoulder. This is America, have at it!

Given the original topic of this thread (which I took as a "Hey guys! Lookit
this...and oh by the way, here's how you can kick in some money if you're
sufficiently interested in funding further experimentation." sort of post),
"your calculations" seem to have become something of a
terribly-important-to-you sub-focus...probably more important to you than to
many/most of the original intended audience.

I offer this opinion as a degreed aerospace engineer having little
personal/user interest in hybrid VTOL flight, "hybrid" in this context meaning
capable of (some) verticality but of primarily "fixed-wings-based" horizontal
capability. Given today's materials, I simply don't see "serious practicality"
on any near horizon for it...similar in that sense to (say) man-powered
flight. Nevertheless, both are technically interesting (to many, including
me); both have been successfully performed; both will (probably) continue to
be investigated and perhaps even advanced (maybe even in my lifetime). And if
you somehow or other engage my interest sufficiently, I might even be
motivated into "calculation checking" beyond merely noting something I've
missed seeing anyone else note, i.e. that the "main prop atop" configuration
is arguably inherently stable in descending, vertically-oriented, flight
simply by the expedient of momentarily lessening "lower down" thrust. That's
not to suggest the physics of such flight are simple, but to rather suggest
the "balancing a pencil upon one's fingertip" analogy previously noted herein
is more appropriate for a rear-exhaust rocket than a "top-biased descender."

Respectfully,
Bob W.

On Thursday, March 31, 2016 at 10:20:59 AM UTC-7, BobW wrote:
Major snip...

My apologies: I thought you were actually interested in discussion the
technical details of the design. I guess by your non-response my
calculations are correct...


They may be or they may not be, and if you're designing such a craft as Dale
Kramer is attempting, I've no doubt you can find qualified people to look over
your shoulder. This is America, have at it!

Given the original topic of this thread (which I took as a "Hey guys! Lookit
this...and oh by the way, here's how you can kick in some money if you're
sufficiently interested in funding further experimentation." sort of post),
"your calculations" seem to have become something of a
terribly-important-to-you sub-focus...probably more important to you than to
many/most of the original intended audience.

I offer this opinion as a degreed aerospace engineer having little
personal/user interest in hybrid VTOL flight, "hybrid" in this context meaning
capable of (some) verticality but of primarily "fixed-wings-based" horizontal
capability. Given today's materials, I simply don't see "serious practicality"
on any near horizon for it...similar in that sense to (say) man-powered
flight. Nevertheless, both are technically interesting (to many, including
me); both have been successfully performed; both will (probably) continue to
be investigated and perhaps even advanced (maybe even in my lifetime). And if
you somehow or other engage my interest sufficiently, I might even be
motivated into "calculation checking" beyond merely noting something I've
missed seeing anyone else note, i.e. that the "main prop atop" configuration
is arguably inherently stable in descending, vertically-oriented, flight
simply by the expedient of momentarily lessening "lower down" thrust. That's
not to suggest the physics of such flight are simple, but to rather suggest
the "balancing a pencil upon one's fingertip" analogy previously noted herein
is more appropriate for a rear-exhaust rocket than a "top-biased descender."

Respectfully,
Bob W.


Excellent points Bob.

I was thinking more that half the thrust was via electric motors down low and half was from the main reciprocating motor that put a lot of weight up high, but only half the thrust at the stable "on top" location, so it's a bit of a mix that could influence the dynamics of the transition from vertical to horizontal flight. I agree the balancing a pencil analogy really isn't proper for a number of reasons.

VTOL is an heroic act, pretty much no matter how you go about it.

Andy

On Thursday, March 31, 2016 at 3:14:00 PM UTC-5, Andy Blackburn wrote:
On Thursday, March 31, 2016 at 10:20:59 AM UTC-7, BobW wrote:
Major snip...

My apologies: I thought you were actually interested in discussion the
technical details of the design. I guess by your non-response my
calculations are correct...


They may be or they may not be, and if you're designing such a craft as Dale
Kramer is attempting, I've no doubt you can find qualified people to look over
your shoulder. This is America, have at it!

Given the original topic of this thread (which I took as a "Hey guys! Lookit
this...and oh by the way, here's how you can kick in some money if you're
sufficiently interested in funding further experimentation." sort of post),
"your calculations" seem to have become something of a
terribly-important-to-you sub-focus...probably more important to you than to
many/most of the original intended audience.

I offer this opinion as a degreed aerospace engineer having little
personal/user interest in hybrid VTOL flight, "hybrid" in this context meaning
capable of (some) verticality but of primarily "fixed-wings-based" horizontal
capability. Given today's materials, I simply don't see "serious practicality"
on any near horizon for it...similar in that sense to (say) man-powered
flight. Nevertheless, both are technically interesting (to many, including
me); both have been successfully performed; both will (probably) continue to
be investigated and perhaps even advanced (maybe even in my lifetime). And if
you somehow or other engage my interest sufficiently, I might even be
motivated into "calculation checking" beyond merely noting something I've
missed seeing anyone else note, i.e. that the "main prop atop" configuration
is arguably inherently stable in descending, vertically-oriented, flight
simply by the expedient of momentarily lessening "lower down" thrust. That's
not to suggest the physics of such flight are simple, but to rather suggest
the "balancing a pencil upon one's fingertip" analogy previously noted herein
is more appropriate for a rear-exhaust rocket than a "top-biased descender."

Respectfully,
Bob W.


Excellent points Bob.

I was thinking more that half the thrust was via electric motors down low and half was from the main reciprocating motor that put a lot of weight up high, but only half the thrust at the stable "on top" location, so it's a bit of a mix that could influence the dynamics of the transition from vertical to horizontal flight. I agree the balancing a pencil analogy really isn't proper for a number of reasons.



Andy

"VTOL is an heroic act, pretty much no matter how you go about it."
12-year olds with drones do it every day, thanks to cheap flight controllers containing super-cheap gyros and accelerometers. I can teach a caveman to fly one of those in 10 min.
Herb

Ture - I have a closet full of FAA-licensed drones - and others. All the modern cheap GPS, accelerometers and brushless motors have been a revolution. Making it all human scale and reliable and safe under all the possible failure modes (especially loss of a motor when you can't auto-rotate) and hanging the aircraft off of whirling machinery is where the heroism comes in. The V-22 had lots of problems and is still a bit of a nightmare. That Moeller flying car with ducted fans everywhere was a mess. There were many others in all shapes and forms. Each had its own unique way to kill you. Dale's approach simplifies many things but also has its own unique new challenges.

Andy