Shameless update from Dale Kramer

On Thursday, March 17, 2016 at 4:19:30 PM UTC-7, DaleKramer wrote:
On Thursday, March 17, 2016 at 6:31:51 PM UTC-4, bumper wrote:
If you used tilting ducted fans, instead of a tilting seat, it would not be as innovative. The ducts would also add drag in horizontal flight compared to folding props. But, if I understand correctly, ducted fans are much less prone to the vortex ring problem.

For this transitional design I think ducted fans would weigh too much, reduce my top speed too much and cause too many structural problems. Tilting fans is what I am trying to avoid ... synchronization issues, tilt mechanism weights, complexity ... I am trying to have a design that people can relate to as 'somewhat' of a conventional airplane shape during cruise.

Dale,

I'm no engineer, but have experienced vortex ring effect caused by too fast a descent into one's own downwash with models, both helicopters and quad-rotors.

I'm guessing vortex ring will be the major design obstacle you'll need to overcome. Consider that in a crosswind, and while maintaining position over the ground descending, the prop wash from the front prop and wing tip props will be moving laterally, so even though they are not positioned in line with, their disturbed air can still conflict with the rear props.

With a limited time envelope to descend and land, there may be considerable pressure on the pilot to descend expeditiously if hand flying. Would this be automated in some manner, or with say a green safe to land "descent profile" indication below a given safe altitude and allowable descent rate, etc.. If, for some reason, the pilot has to abort a landing, say due to wind conditions or surface irregularities, would a vertical take off after a partial descent be possible?

You are on the right track testing with a model, as that should show up any issues.

On Friday, March 18, 2016 at 12:08:46 AM UTC-4, bumper wrote:
Would this be automated in some manner, or with say a green safe to land "descent profile" indication below a given safe altitude and allowable descent rate, etc. If, for some reason, the pilot has to abort a landing, say due to wind conditions or surface irregularities, would a vertical take off after a partial descent be possible?

You are on the right track testing with a model, as that should show up any issues.

Yes there will be automation of some flight maneuvers, after all this could not even be attempted if I was not relying on the multirotor controller for automation of heading and attitude during hover. Adding automated features beyond that is somewhat trivial, especially since I plan to have all control done with 'fly by wire'.

However, I am a firm believer in having a design that is as close to humanly flyable under as many failure modes as possible so I just don't want to start automating things too quickly.

This is a great thread and has given me much to consider, however I am going to have to start concentrating on getting people to pledge on the Kickstarter campaign. If it that campaign fails, I will have to find another way of building the 1/4 scale. So, I will have to slow down the posting here and get my brain into another gear now

DaleKramer wrote on 3/18/2016 5:38 AM:
This is a great thread and has given me much to consider, however I
am going to have to start concentrating on getting people to pledge
on the Kickstarter campaign.

The thread got me to pledge $100. I'm looking forward to seeing the
charge on my credit card next month, which will signal you got the
funding you seek.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

Eric,

Thanks for the support!

Dale

On Thursday, March 24, 2016 at 7:07:15 AM UTC-7, DaleKramer wrote:
Eric,

Thanks for the support!

Dale

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.

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.

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...

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

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

On Thursday, March 24, 2016 at 7:07:15 AM UTC-7, DaleKramer wrote:
Eric,

Thanks for the support!

Dale

This thing crashed this week - pilot walked away, but it was a total writeoff.

http://elytron.aero/#page-home

9B

On Wednesday, March 30, 2016 at 11:26:24 AM UTC-7, Andy Blackburn wrote:
On Thursday, March 24, 2016 at 7:07:15 AM UTC-7, DaleKramer wrote:
Eric,

Thanks for the support!

Dale

This thing crashed this week - pilot walked away, but it was a total writeoff.

http://elytron.aero/#page-home

9B

Glad no one was hurt. Their odds for success don't look good.