combatpigg

My Feedback: (3)

From the 2 charts that I posted earlier, I come up with 25,200 rpm down wind and 23,900 up wind.
What does your Private Pilots Handbook come up with................?

Lownverted

My Feedback: (4)

I'll say it one more time, and type slower so you get it.

I'm not debating that there is a change in RPM upwind vs. down wind. That can be explained by any number of things, diving longer, or from higher, coming on/off the pipe you name it. What it's not caused by is THE WIND! The private pilots handbook, physics & common sense all tell me that. That's ok, you keep arguing in circles though.

Saying the engine has an easier time pulling the model downwind tells me all I need to know about your grasp of reality.

combatpigg

My Feedback: (3)

I've looked at hundreds of Wavoscope charts and never once have I seen the rpm increase on the upwind leg.
According to your way of thinking there should be an equal chance of this happening.
The truth is, I've never seen it happen...ever.
You will probably see less of this effect with large diameter, low pitch props..maybe this is your only point of reference because you aren't a speed pilot yet..?
Take a look for yourself at Raptor's audio passes and let me know if you find any up wind passes that are of equal or greater rpm to what his plane registers down wind.

airraptor

My Feedback: (66)

Quote from CP

"I've looked at hundreds of Wavoscope charts and never once have I seen the rpm increase on the upwind leg.
According to your way of thinking there should be an equal chance of this happening.
The truth is, I've never seen it happen...ever.
You will probably see less of this effect with large diameter, low pitch props..maybe this is your only point of reference because you aren't a speed pilot yet..?
Take a look for yourself at Raptor's audio passes and let me know if you find any up wind passes that are of equal or greater rpm to what his plane registers down wind."

CP do you know anything about how sound travels thru the air? How wave scopes work? how they should be used to get the best results?


Inverted,
dont worry about PIG. I agree with you inverted and so do many people in the forums. look how many POSTS CP has and you will understand. AGIAN this video cant be used to get a good measurment of speed. each pass was different. I DID NOT know i was being filmed that day. So if i would have know CP would be on here babling nonsense i would have flown a better flight path upwind and down wind with both = distance from the mic so to get a better reading from this tuning tool. Most of the time i dont waste my time with CP but this thread i will lol. There are a lot of guys that spew out information (myself included sometimes) that is just plain wrong. CP your just wrong here because your basing your info of of a wavescope reading from a video lol. Somewhere in here someone said you have/had telemetry in planes so tell the truth and did the RPM change when flying into the wind? ALSO CP a model plane and real plane are close in the sense that some are piston powered and have props. so with that does a real plane gain engine rpm when its flying into the wind? also if so how does the engine know its flying upwind verses downwind?????????


CP just give up on try to prove your right here ok.

Lownverted

My Feedback: (4)

CP,

I can see you don't really understand how measuring doppler shift works. The plane is traveling more slowly up wind relative TO YOU, but the airspeed is the same up or downwind regardless. Therefore the Doppler shift is less, so mph and by virtue of how it's measured, the rpm will show less. That's why Doppler is only good for ballpark numbers and generalities.

I have a Jibe F5d that will do 200+ mph all day long verified many ways. Looking at the data from the ICE logging controller, the rpm is the same up or downwind, no matter how much wind there is. What changes is ground speed and how it looks to me. I've looked at this many times.

The fact that you looked at 100's of doppler's shows you are putting waaaay too much faith in them and believing what they tell you blindly. Stop, think about things for a second and see if you can understand. The Doppler trends you are using as evidence are lying to you.

combatpigg

My Feedback: (3)

I've looked at doppler of my low pitched packages [1cc engine with 4x4 prop] that fully unload after the first dive and stay at that level both upwind and down wind, so that blows your theory up about how doppler is read by Wavoscope.
You can't have it both ways, even if the truth about what you WANT to believe is inconvenient for you to accept.

F5D electric as a comparison....?
Epic fail.

Lownverted

My Feedback: (4)

Fine stay ignorant. Lemme guess, you believe in the downwind turn and belong to the flat earth society too right?

The only epic fail here is your tunnel vision and refusal to accept that you are plain and simply wrong. It doesn't blow anything out of the water. Doppler is UNRELIABLE and only a good generalization at best. Your argument is flawed because you think there is a difference in RPM upwind vs down. This is fundamentally untrue, and can be backed up by even the most basic of textbooks.

Airspeed is airspeed regardless of wind. An engine (or motor) sees the same load regardless of wind, or what direction it's coming from. RPM has nothing to do with wind. You can't grasp this simple concept, so there is no use beating dead horse.

Do yourself a favor and take a ride with a full scale pilot on a windy day. Trim the plane for straight and level and fly as many up wind and down wind legs as you want and note the airspeed, rpm and if he's got a Garmin on board, ground speed.

airraptor

My Feedback: (66)

see what i mean inverted he is so blinded by the doppler he cant even understand what he is saying. He just said the RPM stayed the same once the engine unloaded both upwind and down wind. Earlier he was arguing that the engine lost rpm upwind and gained rpm downwind.

PIG your are cracking me up now lol.

Lownverted

My Feedback: (4)

You are of course right, he's arguing in circles. I don't know what I was thinking trying to educate a troll.

FWIW, I looked at the doppler files from the same flight as the ICE data specifically for this very reason. It sounds like it's turning more RPM down wind vs. up. Same on my Nelson powered Q-40. I don't have RPM logging capability on that, but I do have a pitot system to check against radar and doppler.

Red

combatpigg

My Feedback: (3)

dude, when you delivered your Class Validictorian speech at GED Tech, how many times did you say "lol"...?

Lownverted

My Feedback: (4)

Typical misdirection when you have no valid argument.

combatpigg

My Feedback: (3)

You are willing to say anything now..even as far as saying that Doppler is unreliable.
Guess what.? I use both onboard speed recording and Wavoscope and they have always been in agreement with each other. A couple times the onboard unit gave a wildly bogus readout, otherwise I've got complete confidence in these 2 systems, especially used in tandem.
If Wavoscope can't accurately count rpm [frequency], then it can't carry out the rest of the operations that give mph.

combatpigg

My Feedback: (3)

GIGO. The guy's a compulsive liar and you're his attorney / side kick.

Lownverted

My Feedback: (4)

CP,

The errors in measuring mph and rpm with doppler are well know and documented, I won't bother arguing them anymore. HINT: It's measuring from a ground based reference, therefore measuring ground speed, not airspeed. Therefore all mph and rpm calcs are suspect at best. Same with radar, gps etc. I suspect we are at a stalemate here, and I'm willing to accept that.

I'm all ears and willing to listen. Would you please explain to me how an engine will rev higher down wind than up wind. I'm will to change my point of view. Convince me. This is what i'm really interested in.

combatpigg

My Feedback: (3)

Gravity applies a force that makes the plane gain speed and it takes the strain off the propellor/engine to pull the plane.

The only reason why this happens is because of the external power that is taking some load off the engine.

Flying downwind applies external power to make the plane gain speed. The engine doesn't care whether the external power is coming from gravity or from the wind. I suspect that most prop/engine/plane set ups aren't real sensitive to the subtle change in load at full throttle, but I don't spend time analyzing set ups like that.
Q40s are propped to "ignore" changes in load so that they give the best average speed on the course. They unload quickly after takeoff and sound the same the rest of the heat. They aren't propped for optimum speed like the examples I'mtalking about. You might as well tell me all about your sprint car while we're talking about 1/4 mile dragsters.

iron eagel

Actually Doppler is a pretty good measurement system, because it uses a time reference as it basis for calculations. Given the clock rates of today's CPU most computers can do fairly accurate measurements because there time reference is pretty exact. Now as far as the ground based measurements, radar and gps it is fairly easy to compensate for the ground vs airspeed aspect.
I'll give you an example using the measurements Combatpigg got from his Doppler readings.

With the two speeds of 140 and 170 indicated by Doppler I would put money on the actual airspeed indicator (if it had been available) would have been reading about 155 (plus or minus the 9 mph error that the Doppler program has for accuracy) and (plus or minus the x mph) that the airspeed indicator had for accuracy. Keep in mind how this stuff is done for the world book of records.
By taking the average of the two ground based measurements it is possible to extrapolate the actual airspeed, so therefore Doppler, radar and GPS can make accurate measurements of airspeed.

Don't believe me send the question to "Mythbusters".

FYI, I do know how test and measurement systems work, I used to run a Mil Spec Calibration laboratory back when we still made stuff in this country.
Besides unless the test systems you are using are calibrated by standards traceable to the NBST or NIST as it is called today all of the data is "for indication only", and not to be considered reliable.



.

airraptor

My Feedback: (66)

CP i think you are just messing with us no one could really believe that an engine gains( sees less of a load) power flying downwind. you got us very funny. I put lol in to let you know i am not trying to piss you off.

Eagle no one is really arguing the doppler just Combat pig stating that an engine will have more power applied to the engine by flying down wind and that an engine losses power going upwind.

CP if you are not joking then i have lost all faith in anything you say.


HOW does a Q-40 engine "ignore" changes in load

combatpigg

My Feedback: (3)

The Q40 is propped for best compromise of acceleration and speed, but not for the absolute highest speed that is possible. It's just like the gear analogy in a transmission, the lower gear makes the engine less sensitive to changes in load.
You can see this play out dramatically with AMA Fast Combat planes that you "prop up" to go for max speed. They will only tolerate flat level passes and will immediately die if you try to do a loop, no matter how well the needle is set.

NoOneFlysAtMyClub

My Feedback: (32)

People, people people........................

OS .32??????????????

Lownverted

My Feedback: (4)

You do understand that the airspeed a plane sees is the same regardless of wind right, and that only ground speed changes? The wind only helps in relation to your point of view, not the airplanes.

Lownverted

My Feedback: (4)

[quote]ORIGINAL: iron eagel


[quote]ORIGINAL: Lownverted



I isolated part of your quote above.

Actually Doppler is a pretty good measurement system, because it uses a time reference as it basis for calculations.

This is exactly why its not accurate! Airspeed from the aircraft itself is the only true measurement. Doppler is referencing a moving object from a ground reference. You are measuring ground speed, not airspeed. How can you possibly compensate for airspeed without a reference from the plane? The very basis for the measurement is flawed. Now I agree that it's good for guesstimates and generalities, but as you yourself pointed out, the 9mph margin of error will also affect the RPM readings that CP takes for gospel.

CP is basing his theory that an engine gains RPM down wind vs. up wind because of gravity and magically less wind. This is 100% wrong if you understand the relationship of airspeed & ground speed. If you don't understand this relationship, then there is no point in this discussion.

Lownverted

My Feedback: (4)

HAHAHAHAHHAHAHAHAHHAHAHAHAHAHA You should analyze physics a bit before you attempt anything else.

combatpigg

My Feedback: (3)

How much HP does it take to go from 155 mph to 170..? [with a 8x7]
It's a significant amount [almost 1 HP] and it isn't being furnished by the engine. The engine only has enough power to do 155 on it's own in calm air.
There are no free lunches in energy exchange and the engine acts like a watt meter in this case as it registers the energy boost with a measurable jump in rpm. It takes 2.6 HP to do 155 mph with a 8x7 and it takes 3.5 HP to go 170.
The external power is sent through the airframe, through the prop and the engine looks like "The Hero" because it was able to spool up in response to this invisible boost...but never forget the fact that the engine ON IT's OWN POWER never could have reached that level of power without outside help.
Works just the same way as in a vertical dive. People who know better can see power getting back fed into the machine from Mother Nature's stored energy.

Lownverted

My Feedback: (4)

Wrong, wrong wrong.

The difference in the GROUND speed is the wind. Not extra magic force. The plane is going the same AIRSPEED both ways.

Seroiusly, get a clue. There is no magic gain in HP.

combatpigg

My Feedback: (3)

On a clean, light, relatively small plane [designed for .20 power]...8x7, 8x8 will be good to start with. You might hit 120 mph with a Top Flite P-51 [.20 sized] and 130 mph with a 32 inch span delta.