Performance Calculation of Gyros

Jazzenjohn

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I've used it and it works OK for me. I usually play around with the rotorblade numbers to better reflect my actual RRPM's. On my light single place with Dragon Wings I use the clean 8H-12 profile and I set the effective blade pitch to around 4.8 degrees which gets me closer to the RRPM's I actually see. Dragon Wings are twisted so the blade pitch varies from root to tip. It suggests my lowest rate of descent is at about 35 MPH and my best glide is around 50 MPH which seems about right. The climb rate and max speed it shows for my gyro are both well above where I believe they should be at the fastest speeds, maybe because my gyro is especially draggy. They seem closer, but still a little high, at normal (for me ~50 mph) flying speeds.
 

Aviator168

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Is a the descent rate a compound number? Like the rotor is viewed as in constant descent. How is it translated to the verticle component?
 

Jazzenjohn

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If you're asking whether the descent rate is for a vertical descent, then no it is for best glide rate descent. If you're asking how the number is derived within the program, that question is way past my ability to answer. You could try Chuck Beaty or the author of the program Jukka Tervamaki.
 
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Vance

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It models The Predator pretty well except for the glide ratio.

It shows less than three to one and it is not unusual to see four to one on my GPS.
Correction: I was reading the numbers wrong. The glide ratio is actually showing high in the calculations getting into the high fives. I seldom see more that 4.5 to one but it is usually with about a ten knot head wind.

My calculated rate of descent appears low to me at just under 1,000 feet per minute at 50kts and it is generally closer to 1,200 to 1,400 feet per minute at 50kts and north of 1,400 in a near vertical descent..
 
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XXavier

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It models The Predator pretty well except for the glide ratio.

It shows less than three to one and it is not unusual to see four to one on my GPS.
Correction: I was reading the numbers wrong. The glide ratio is actually showing high in the calculations getting into the high fives. I seldom see more that 4.5 to one but it is usually with about a ten knot head wind.

My calculated rate of descent appears low to me.
The horizontal component of the glide ratio, as calculated by GPS, is an 'absolute motion' with reference to the ground, and not to the mass of air you're flying in. That may be the reason for a difference, the glide ratio (with reference to the ground) being smaller with a headwind and larger with a tailwind...
 

Vance

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The horizontal component of the glide ratio, as calculated by GPS, is an 'absolute motion' with reference to the ground, and not to the mass of air you're flying in. That may be the reason for a difference, the glide ratio (with reference to the ground) being smaller with a headwind and larger with a tailwind...
That is why I mentioned the wind.
I learned about the effects on the wind on gliding distance a long time ago.
I was gliding in to SMX from 12,800 feet and 15 nautical miles away. That would take better than a seven to one glide ratio.
I made it easily with a tail wind.

I tell my clients to figure three to one so they can select a landing zone within reach and I like to simulated engine outs into the wind.
She glides further with the engine shut down.
 
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ventana7

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I found an easy way to figure glide ratio and get a sight picture of where I would land in an engine out. I get over the numbers at exactly 500' AGL and cut the power. Proceed with your engine out landing and mark the spot where you touch down. Most runways are painted with 120' long white stripes separated by 80' spaces so 200' per white line but you can measure yours to be sure or take an aerial photo and count how many to the 1000' markers. Knowing you were at 500'AGL and where you landed makes it easy to figure the glide ratio.

The next step is more important. Take another lap again at 500'AGL and see where on your windshield your landing spot is. You could even put a dot at that place on the windshield. That will be the sight picture of where you will touch down from any height. You might want to factor in a delay in your reaction to pitch to best glide and also how much more you might glide with a stoped prop rather than the windmilling prop in your test. Then of course figure in the wind at the time of your engine out.

Rob
 

Vance

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A spinning prop creates a lot of drag. How much further does she glide with engine completely shut down?
I have not measured the difference in The Predator because I generally teach engine out landings with the engine at idle.

It is quite noticeable and might amount to a 15% reduction in drag.

I have a Lycoming IO-320 and a 68 inch three blade propeller so it is likely more noticeable on my aircraft.

I have noticed it on the Cavalon. I would not attempt to quantify the difference.

Same goes for the RAF and Modified RAF.

Same with the MTO Sport.

I don’t have enough time in a Calidus to have an opinion. A Calidus seems to glide particularly well.

When the engine goes quiet I am usually pretty busy.

I try not to create an emergency to teach emergency procedures.
 

C. Beaty

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All things that fly, from bugs to blimps fly through an air mass that to them is stationary and if there’s wind, the Earth’s surface is moving. Cover the surface with a great green blanket and the pilot would never know if there’s a wind unless he had navigational instruments.

For an aircraft circling a free floating balloon, there is no such thing as an upwind or downwind turn. Tether the balloon to the ground and our old nemesis, the downwind turn returns but then we’re flying by ground reference.
 

Vance

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In my opinion winds are a ground reference term and affect an aircraft in relation to the ground.

The landing zone is on the ground.

From a practical standpoint how far over the ground an aircraft can go is more important than the glide ratio in relation to the air mass.

Landing is a ground reference event and in my experience a downwind landing in a gyroplane is more challenging than landing into the wind.

When the engine goes quiet I would like to know which way the air mass is moving in relation to the ground to predict my ability to reach the landing zone and the landing itself.
 

Jean Claude

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I've used it and it works OK for me. I usually play around with the rotorblade numbers to better reflect my actual RRPM's. On my light single place with Dragon Wings I use the clean 8H-12 profile and I set the effective blade pitch to around 4.8 degrees which gets me closer to the RRPM's I actually see.
For a better works of Jukka's calculations, do not uses "Clean 8H12", but "Rough 8H12", then ajust the blade pitch for the Rrpms you actually see
(probably becomes< 4 degrées
 

Jazzenjohn

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That does seem a bit better Jean Claude, thanks. It puts the blade pitch nearer 4.2 degrees to get a RRPM to nearer what I see, and drops the top speed down to a more realistic number. All in all I think it is a pretty great little calculator, especially to use by inputting different values to see what changes it makes. I think it might get even closer if I could use the airframe drag as more of a variable as it is probably worse than the open cockpit setting. (What I really should do is get off my lazy ass and clean up the airframe a bit...)
 

fara

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A simple way to get fairly accurate numbers that I have used
You need to first and foremost calibrate your airspeed and get a good chart of CAS. Then you need to have a proper vertical speed indicator or sensitive altimeter with a proper static port location.
You can find the proper position by using tufts taped on your gyroplane's body and flying and noticing undisturbed areas on air where tufts seem to be straight back without any flailing around in coordinated flight. This is where a static port placement would be good. Having that all done, you fly at you suspected/expected best glide speed at safe altitude in dead calm smooth conditions without turbulence. Smooth wind is not turbulent so this doesn't mean no wind. It does not matter if you are flying in headwind or tailwind, just smooth wind without turbulence. At the suspected/expected best glide speed, turn your engine off (obviously be high enough over a landing spot like an airport n case engine won't start again). Then establish a constant and steady glide at that speed. Once steady, start a stop watch and simultaneously notice altitude. In exactly 60 seconds, note altitude again. That gives you your descent rate in Feet Per Minute (FPM).

Example:
Lets say you lost 1000 FPM. That is 11.36 MPH
Lets say this was at suspected/expected best glide speed of 50 MPH (that's 4400 feet per minute)

50/11.36 = 4.4
OR
4400/1000 = 4.4

You can repeat this in different headings one after the other 120 degrees or 90 degrees roughly apart and average the results

That's a simplified way. Technically you should use True Airspeed (TAS). A good approximation would be to add 2 MPH for each thousand feet of altitude to your Calibrated Airspeed (CAS).

A good way to calibrate your airspeed using GPS method that is an acceptable method by FAA is described in KitPlanes magazine article.
 
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Vance

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She looks underpowered to me.

When I purchased The Predator she had a 135 horsepower Lycoming O-290 and a two blade 66 inch propeller.

My wife and I were flying near a maximum takeoff weight of 1,400 pounds on a hot windy day out of the Santa Paula airport.

The airport is in a narrow valley and when the Santa Anna winds blow it become very turbulent.

We would get stuck in the rotors that would overcome our ability to climb at 300 feet per minute and reduced our climb to about 20 feet per minute.

I was also limited to around 6,000 feet MSL, marginal for the area I fly.

I found the situation disquieting and replaced the O-290 with 160 horsepower Lycoming IO-320 and a 68 inch three blade propeller.

The Predator went from climbing out at 300 feet per minute on a hot day at gross to 700 feet per minute under the same conditions.

For me a 500 foot per minute would be the minimum rate of climb that is acceptable.

Use the program to recognize what density altitude will do to your performance.

I don’t understand the desire to have a marginally powered gyroplane.

Try adding 16% horsepower and see what it does for you.

I am not able to read the temperature from you screen shot, try 100 degrees f.
 

DarDow101

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kewl program. I don't know if these numbers reflect the real world but it is interesting to play around with the numbers



GyroCalcWin.png
 

Aviator168

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She looks underpowered to me.

For me a 500 foot per minute would be the minimum rate of climb that is acceptable.
What is confusing to me is the "rate of climb" curve. It does not look that bad. Keep in mind it is an ultralight, so 200 to 300 ft/min is good enough.

BTW. The temperature I used is 60, about 15 at sea level.
 
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