Streamlining my Helicycle landing gear

StanFoster

Active Member
Chris- Heres a question for you. I have a nice online density alitude calculator that you punch in your altitude, temperature, barometric pressure, and dew point to arrive at your true density alitude.

My quick research showed me a density altitude chart that had an almost linear line from 0 feet to 12000 feet density altitude as far as the correction factor for airspeed. It showed that every 500 feet of density altitude gain, there is a speed multiplier of 1.0083. So if one day I had a data run showing 110 mph.... and I go repeat the exact settings the next day .......but the density altitude is 500 feet higher, I should expect to see 110 mph X 1.0083......or 110.91 mph. Do you agree with the difference?

Of course with the weather warming up now... I could collect all my data without my fairings on these colder days......then install the fairings and be testing them on higher density alitude days...and be thinking the fairings are adding many more mph...when in fact most of that would be because of density altitude.

I in the beginning was wanting to take my recordings on days with the same temperature.....but I thank you for your inputs that have heightened my awareness of also including barometric pressure and humidity as well.

I still will try to only compare data with and without the fairings taken on days with the density altitude very similar.....and still use the calculator to fine tune it.

This is teaching me a lot about data gathering.

Stan

StanFoster

Active Member
My rivets arrived......the fairings are done and off to the painters.

Hopefully they will be ready for me to put on when I get back from Bensen Days.

Meanwhile.....I will be doing some data runs....as many as I can before I put the fairings on. All runs will have be corrected for density altitude...then the true airspeed entered on my graphs.

Should be a fun time ahead.

Stan

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ckurz7000

Senior Member
Stan, you're right about correcting the airspeed. But density altitude also affects engine power and all aerodynamic quantities such as rotor lift and drag. It is difficult to use mathematical means to correct for all of these effects properly. Much better to stop them even from entering your test by sticking to the same density altitude.

You are looking for an increase in airspeed of the order of a couple of precent. Therefore you need to be accurate in your methodology to much better than a few percent or else you won't be able to "see" it.

Greetings, -- Chris.

StanFoster

Active Member
Chris- I understand that density altitude effects power, but in my case I disagree with the idea of flying high off the ground just so I am at the same density altitude. I know I will be very busy keeping the collective exactly on my degree setting, keeping the yaw string straight, watching my GPS readings, and all the flight instruments as well. I have no doubt that I will be in a shallow climb or descent which will introduce a lot more error into my data. Don't you agree that my method of flying at 50 feet agl will eliminate this problem? I have no doubt it will! The ground itself will have my subconscious flying the helicopter very level, not even a doubt! ................................Flying at altitude just doesn't work for me. So, this tells me that my most accurate data will be to record it on days with the same or very nearly the same density altitude, fly level runs at 50 feet agl, average my GPS readings downwind and upwind. No math corrrections or very miniscule ones, no climbing or descending errors, and no speed errors from trying to guess what my ASI is reading as its needle oscillates........................................I will of course have data from different density altitude days, but will just focus on identical or near identical density altitude days.............Don't you agree this will be the most accurate comparison of data with what equipment I have? I feel I will introduce very little error if I simply fly at 50 feet agl on very similar density altitude days, and average very meticulous GPS speeds. That's about all I can do! Stan

Intrepid175

Newbie
This has been a very interesting read gentlemen. Makes me wonder how anyone with an experimental aircraft comes up with any kind of accurate performance data. How do the certified aircraft manufacturers generate their performance charts? Are they the result of hours upon hours of test flying, or do they generate some kind of base line and then mathematically interpret the rest?

Best of luck with this Stan and fly safe!
Steve R.

ckurz7000

Senior Member
Hi Stan,

yes, I agree that flying at a constant 50 feet at days that have the same density altitutde conditions is best. I only wanted to make you aware of something that you already are.

Looking forward to the data, -- Chris.

ckurz7000

Senior Member
...How do the certified aircraft manufacturers generate their performance charts? Are they the result of hours upon hours of test flying, or do they generate some kind of base line and then mathematically interpret the rest?...

Hi Steve, as I am personally in the middle of the flight test phase of an aircraft to be certified, I can tell you exactly how this is done: it is hours upon hours of meticulous planning, flying, analyzing, adapting and flying again.

For example, you need performance data for all weights, CG positions and altitudes you plan to fly the aircraft. Say you want to test at the lowest, highest and a mid range value for all three variables. Then you have to do the flight testing at least 27 times. Each time you are required to average 6 attempts. In order to get 6 good data points you might have to fly 10 attempts. So there alone you have 270 times you need to fly the same thing. And that's for only one performance data such as cruise performance.

Further more, you need suitable weather to do the tests. If there is more than, say 5 km/h of wind you can't really do a take-off or landing test flight. If there is appreciable thermal activity, you can't fly cruise or climb performance test flights, and so on.

When you do airspeed calibration tests you have to hold altidude to 100 feet, fly absolutely straight and level at a specific heading +/- 2 degrees and indicated airspeed (+/- 1 knot) with the yaw string centered, and all of that for at least 10 seconds, so that all the readings can stabilize. You do this for at least three different headings, and this gives you a calibration point for a single airspeed. About 15-20 such points make up a complete calibration curve. And when you learn that your static ports aren't placed just right and IAS deviates from CAS for more than 5% you land, drill different static ports and start over again.

It really teaches you accurate flying.

But then there are some pulse raising test also. We have to determine minimum safe rotor speed and the corresponding minimum G-loading.

We also have to establish a height-velocity curve for the ArrowCopter. And this entails finding the minimum speed /altitude combination at which a safe landing can be performed with the engine off. So you really have to turn the engine off (idling is not enough) and slowly inch your way toward the point where a safe landing cannot be performed anymore.

It's a whole different way of flying but very educational.

-- Chris.

StanFoster

Active Member
Chris- I love your flying at the same density alitude method...and I would totally embrace that if I knew I was flying level. My flying skills will be challenged enough maintaining the collective pitch on the number, keeping my yaw string straight, the GPS, and scanning the instruments. I will be like a one eyed cat watching half a dozen mice!

However..... I will be so pig headed....and at least try it. Your way would be the most accurate if I could maintain level flight.

Stan

StanFoster

Active Member
Heres an airfoil analysis sent to me from Nicolas. The top light green is the profile of the airfoil I am going to be installing.

The dark blue line is the graph of my airfoil if I streamline the leading edge also.

If I have measurable success on the rear fairing...I know I will go for even better performance by doing the leading edge as well.

It wont be as difficult except I need to learn to work better with fiberglass.

Stan

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StanFoster

Active Member
Another data run was charted yesterday.

First of all.....I tried flying a consistent density altitude which was too high to fly by looking at the ground. I tried my best to keep my altimeter pegged . I could not get a consistent GPS reading with less than a 3-4 mph variance, showing I was in a shallow climb and descent...sometimes actually flying level. Down on the deck.....my GPS reads within 1 mph. So, I am not able at this time to fly a consistent altitude watching the laser pointer...GPS, yaw string...and other flight instruments....and maintain a consistent altitude like I can when I let the ground control my reflexes! So, its a waste of time plotting data that is just trying to guess if I am flying level or not.

My data for yesterday was at a much higher density alitude. I had been runnng at a -250 feet DA. Yesterday was 1920 DA with the 75 degree temps...barometric pressure of 30.18 and a dew point of 34 degrees.

My top end readings were increased to 114 mph actual average GPS groundspeed. The wind was non existent but I still flew due north...then due south and averaged my speeds.

My previous top end of 112 mph recorded at -250 DA. Yesterdays 1920 DA had me flying at a 2170 foot higher DA. My 114 top end readings coincide when mathematically adjusted for the higher DA I was flying at.

So far my data seems to be very consistent. I fly down on the deck and let my GPS speed stabilize to within 1 mph....and I fly a while making sure it is consistent.

More data runs to come at apparently wild DA swings for my area. We are having near record highs for today also.

Note- I am flying with my full doors on which streamlines my cabin. I am going to not take my doors off until I get plenty of data with my fairings on.

However....I am gathering data now at near record temperatures and Aprils temperatures will more than likely be lower.

Stan

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StanFoster

Active Member
I am now collecting new data as my half doors are on now. This weather is unusually warm and off the full doors came.............My fairings are at the monster Truck painter, Mark Stevenson. However he is doing a monster truck show out in Vegas this next week. When I get back from Bensen Days, he will paint them. They will be white with burgundy stripes. Can't wait to gather more data with the half doors and without the fairings. Then, when I feel I have enough data, I will install the fairings and collect new data. Stan

choppergabor

Newbie
Yaaaaaaaaaaaay. Did you know that a nice looking painting increases the speed of your helicycle? It is true! btw 3 more days

All_In

Gold Supporter
Way cool, keep us posted.
Inquiring minds wish to know.

StanFoster

Active Member
John- Nice chatting with you on the phone. My fairings are being spray painted today. I was very pleased how my painter knows how to prep aluminum properly. They are primed and the rivets on the top side have vanished! I will tape the fairings off Monday and have him shoot burgundy stripes on them, then he will clear coat them. I should have the fairings installed next week end, in about 1 week! That sounds better than "in about 2 weeks". Meanwhile, todays mission is to gather more speed data as I am now flying with my summer "half" doors. I will be landing and taking off from my house today a lot. Barbara and I love working in our yard together. Having my Turbinator right nearby for occasional escapes of ecstacy is simply "priceless". Stan

StanFoster

Active Member
My fairings are getting their white paint sprayed on today....so I went out and did some more data runs. I have the half doors on for summer and recorded the barometric pressure...dew point...temp...and adjusted it for DA> I might have time to put the fairings on next weekend and see how they perform. A couple of pictures of my friends by my Turbinator.

I stopped at a few friends homes and visited a little while. The alfalfa was record height for still being March. There is actually a farmer who planted some corn and it is up already. Usually they dont plant around here till at least April 15th. Most are still waiting....because it can still frost. There is no crop insuance for replanting if you plant before April 7th.

Stan

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All_In

Gold Supporter
Let's hope there is no frost!

Liked the pictures buddy and look forward to the final results!

How cool is that you can just drop in on friends!!!!

StanFoster

Active Member
John- I was out doing an on the deck high speed run when I flew right over a friends house. He was out waving me in, so I circled back, did a high recon, then a low recon, and set it down next to his evergreens. He came out with his camera and said, first helicopter to land at his place! I was goind right at 112 mph when I went over his house, and he hardly had time to get out in the open and wave me in. I am going to have my data runs complete just a few more flights. So far my data adjusted for DA has my figures consistent. Stan

StanFoster

Active Member
Fairings are installed

Fairings are installed

I have my fairings installed and I am very pleased with my painter. I know what skills not to attempt. You can not see any of the outside rivets.

I put a bed of white silicone on each of the internal webs....siliconed the leading edge lips...and the inside of each strap. Then they were rivited on. The silicone will prevent any torsional movement and they feel very solid. Anytime you have a curve involved...it braces itself.

I am thinking of putting the word "Turbinator" vertically down the rear fairings.

No test flights for a few days until the silicone cures. I have to put some white paint on my flush rivets that are holding them on.

There are a lot of fun hours on these ....and I thought in the beginning that I might make these for others....but it would not be economically feasible.

Stan

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Vance

Gyroplane CFI
She looks great Stan!

She looks great Stan!

She no longer has skinny legs.

The bars are a nice touch that adds an integrity that I did not expect.

I look forward to the testing.

Thank you, Vance

Doug S.

PRA # 41505
Stan
I like it... they look great.
The wheels won't interfere with them will they?
I would hate to see them get scratch by accident.

Can't wait to see the results... Great job!
Doug S.

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