RE: How to Correct Measured Thrust for Density Altitude?
It makes me to think how velocity is being measured and also to use the formula, please correct if I'm wrong. I have no actual efficiency and nozzle pressure data but for someone who is determined I believe they can get this data from different ways... Sample efficiency = 60%. Based on approx 700 deg C EGT, Tt = 700 + 273K = 973K NPR = 4 Value for following constant: Specific heat of air at constant pressure, cp = 1.0 kJ/kg-K = 1kN-m/s^2-kg-K 1kN = 1000kg-m/s^2 cp = 1000 m^2/s^2-K gama = 1.4 Ve^2 = 2 * 1000 m^2/s^2-K * 973 K * 0.6 * (1 - (1/4)^(1.4-1)/1.4) Ve = 618 m/s or 1383 mi/hr The higher the temperature, efficiency and NPR the higher the exhaust velocity
Posted on: 9/18/2012 9:58 AM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11232465

RE: How to Correct Measured Thrust for Density Altitude?
If we look at how prop and turbine wheel is being spin I believe it's more about air velocity and mass is used to transfer energy then maintain. If I can find out that the differences between net velocity at almost the same temperature and rpm are negligible I can conclude that ratio of Thrust is equal to the ratio of density. T1/T2 = density1/density2 or T2 = T1 * (density2/density1)
Posted on: 9/17/2012 3:59 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11231579

RE: How to Correct Measured Thrust for Density Altitude?
[quote]ORIGINAL: Dr Honda [quote]ORIGINAL: rctech2k7 I agree, it’s really complicated to determine parameters of an engine, because it takes time and some guts to analyze thermodynamics process. To be practical I just used value on the output side of an engine and get comparison between the test... it again. [image]http://www.grc.nasa.gov/WWW/k-12/airplane/Images/turbth.gif[/image] BTW, rctech2k7
Posted on: 9/17/2012 3:42 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11231561

RE: How to Correct Measured Thrust for Density Altitude?
That sounds great, my little programming skills was out of date. Also looking forward for the solution of this thread. Negative about the second question. John
Posted on: 9/16/2012 7:10 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11230519

RE: How to Correct Measured Thrust for Density Altitude?
[quote]ORIGINAL: TimD. [quote]ORIGINAL: rctech2k7 Tim, maybe you are referring to this one: [image]http://www.grc.nasa.gov/WWW/k-12/airplane/Images/thsum.gif[/image] Explanation is located on: http://www.grc.nasa.gov/WWW/k-12/airplane/thsum.html John [/quote] Nice rctech2K7 ! What would need to be done is all parameters and DATA SETS need to be put into an Excel spreadsheet and write the program
Posted on: 9/16/2012 3:55 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11230324

RE: How to Correct Measured Thrust for Density Altitude?
Tim, maybe you are referring to this one: [image]http://www.grc.nasa.gov/WWW/k-12/airplane/Images/thsum.gif[/image] Explanation is located on: http://www.grc.nasa.gov/WWW/k-12/airplane/thsum.html John
Posted on: 9/15/2012 11:37 AM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11229408

RE: How to Correct Measured Thrust for Density Altitude?
Actually on the above formula, you don't need to measure velocity manually, if you have Thrust data you can get information about the velocity. The only difference is the mass flow rate but you can assume they have constant flow rate or you may consider fuel flow rate if you would like.
Posted on: 9/15/2012 11:34 AM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11229400

RE: How to Correct Measured Thrust for Density Altitude?
[/image] BTW, rctech2k7 is a short for RCTech2007. Rctech was taken when I signed up but since
Posted on: 9/14/2012 7:14 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11228859

RE: Alternative uses for turbine engines
This is a clever idea, I can use this to dry our runway fast when wet because last time I flameout because of water. http://www.youtube.com/watch?v=9NGZgumxe04
Posted on: 9/12/2012 7:41 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11226794

RE: How to Correct Measured Thrust for Density Altitude?
Hopefully I got the formula that he’s looking for… If you are confused try this simple step by step. Thrust if a force and it’s also a product of mass flow rate and velocity of a moving gas from exhaust nozzle considering engine on a test stand. This formula can be derived from Newton's Law of Motion or Force = mass x acceleration. Acceleration (a) is a rate of change in velocity, at constant rate, a = (final minus initial velocity)/time, when started from rest initial velocity is zero. Therefore a = velocity/time. Subs to "a" in Force T = m * velocity/time. This can written as T = (mass/time) * velocity. Same thing when using change in momentum per unit time which is [(mass * velocity)final - (mass * velocity)initial]/time, initial velocity = 0 To make it short we can use Thrust Force T = (mass flow per unit time) * velocity Mass = density * Volume, while Volume = Area * Distance of displacement, Now using rate: mass flow rate = density * Volume flow rate where Volume flow rate = Area * Distance/time, distance per unit time = velocity Substitute those above expression to get Force (T) T =density * Area * velocity * velocity can be written simply as: T = density * A * velocity ^2 This means that density has constant effect to Thrust while expo on velocity. Using at least two data from test reading you may get T1 and T2 with functions as stated above, let's try another same maximum velocity where V2/V1 = 1, we can get [b]T2 = T1 *(density2/density1)[/b] It can be used to determine new Thrust given with old Thrust T1, old and new density at same exhaust velocity.
Posted on: 9/12/2012 7:05 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11226757

RE: How to Correct Measured Thrust for Density Altitude?
Let me try if I can help… Considering Thrust (T)= mass flow rate * exhaust velocity T = density * volume flow rate * velocity T = density * A * (D/t) * velocity T =density * A * velocity ^2 Consider test stand thrust T1 = density1 * A1 * velocity1 ^2 and test 2 thrust, T2 = density2 * A2 * velocity2 ^2 Same engine, Area A1 = A2 therefore T2/T1 = density2 * velocity2^2/( density1 * velocity1^2) T2 = T1 * [ density2 * velocity2^2/( density1 * velocity1^2)] [b]T2 = T1 * (density2/density1) * (velocity2/velocity1)^2[/b] If T1 = T2 then density1 * velocity1^2 = density2 * velocity2^2
Posted on: 9/12/2012 10:48 AM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11226268

RE: Am I the only one who flies pattern with no mixes in their plane ??
Well, it’s all depends on your preference, rules, etc… You might be gifted with more skills, if it’s true then you could fly better with those features. It’s an advancement although it’s also depends on the type of airplane and flying style considering you fly from small to large scale including turbine jets which require more flying condition… My suggestion is if your radio has feature and it will be useful and better for you go ahead use it. Full scale pilots are very well educated, skillful and specialized for their job but they use high end features of their aircraft too. It’s there primarily for safety. Other than that, mechanical and human factor can affect performance especially when high workload and stress are involved. Scientist, engineers and tech are working hard on this to keep away from any error... And for me, it’s really far better if it’s there regardless of its function that during the urgent time that we need it’s available…
Posted on: 9/11/2012 6:49 AM by Author "rctech2k7" in the forum "RC Pattern Flying"
http://www.rcuniverse.com/forum/fb.asp?m=11224907

RE: Futaba GYA351 setup help?
Hi everyone, I heard the gyro that was also mentioned here GYA352. I’ve got one recently from this link: http://www.keimod.com/shop/product_info.php?products_id=337 I just finished installing this gyro few days ago on my hornet however still working on to get the right gain control as I setup initially on lower gain to check of any hunting as I increase the speed. Here’s the test flight: http://www.youtube.com/watch?v=VFwdTy175Oo I setup the gyro in the two horizontal stabilizer as Elevon mode to get the advantage of 2-axis at the tail plane since main wings controls are directly from the receiver. I used the GYRO program mix on the transmitter where I can assign gain value. On the initial test flight I used separate 3-position switch so I can assign emergency off, low gain (5%) and high gain (20%). I took off using low gain, maintain at normal flight and increase to high gain when full flaps were deployed. I’m going to increase gain slightly and use flaps setting to provide gain value for the gyro. This aircraft is very stable without gyro due to the location of CG but I reduced its natural stability to increase maneuverability at lower power and speed. I’m still planning to maintain much portion of its natural stability and semi-stabilizing because it helps me with lots of parameters including airspeed condition. Although these days there are telemetry system that can helps us and the aircraft to relay her condition in the air. Thanks everyone for this informative thread…
Posted on: 9/7/2012 11:41 AM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11220872

RE: Arming Auto Spoiler...
[quote]ORIGINAL: invertmast Either way, its a very unique way of activating a surface. I have plans to do a similar action on my F-14's spoilers once the prototypes are up and flying well, but I had plans on using a wheel RPM sensor to pop the spoilers. [/quote] That’s another landing sensing device where a steady signal to the actuator is an advantage, however during when the aircraft goes back in the air for any reason the spoiler still extended while the wheels are running unless full power is applied. I believe it can be solve easily by the sensitivity of your sensor. The issue I found with Switch as a sensing device is the vibration on the runway. Here’s how the switch is absorbing impact that could create on and off signal. http://www.youtube.com/watch?v=Kb74CpQQRDA It can cause to deplete air in the pneumatic tank. The solution I’m considering instead of time delay is to use capacitor to hold voltage in the relay coil and since capacitor can cause high current on the initial switching a series inductor in the switch can reduce transient current while the capacitor is charging, although mechanical way or spring in the sensor might solve the issue... Similar to your sensor we need time to delay but not too long because we also need lift when aircraft goes back in the air. I’m adding Auto Retract that most of is suggesting when full power is applied as a safety for both Manual and Auto. Also fail-safe device similar to gear retracts to deactivate at low air pressure.
Posted on: 8/24/2012 1:57 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11204755

RE: Arming Auto Spoiler...
Lots of good idea from here… Actually, this jet is very stable and stick on the runway after touchdown but she likes speed in which spoiler/speedbrake might be helpful from unexpected gust on touchdown though spoilerons or spoilers on wings would work better. Also landing for me is the most busiest part, wings are still flying, steering needs to be in tracked in which I have no time to click for this device other than mixing it on the wheel brakes. This device can be setup to more condition or mixes, in which a very helpful throttle condition to deactivate at full power can be integrate. Thanks for all your input…!
Posted on: 8/22/2012 2:52 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11202489

Arming Auto Spoiler...
Almost done with auto spoiler system for my hornet’s speedbrake… This can be done in many ways, this one uses single channel for the control of manual operation and same signal that operates simple controller circuit or relay. [image]https://lh3.googleusercontent.com/-NLsv180jt9E/UDUXCQWsQnI/AAAAAAAAAIM/gqbXEaZTV7o/s540/Switch.jpg[/image] [image]https://lh6.googleusercontent.com/-9VCK40yTLwc/UDUS_ycxbpI/AAAAAAAAAHE/5KWzIT3giNo/s912/Auto%2520Spoiler%2520Diagram3.jpg[/image] [image]https://lh5.googleusercontent.com/-Qn0Y71jmUL0/UDUS_1WYSTI/AAAAAAAAAHQ/gWD-TEltDRo/s912/DSC00026R2.jpg[/image] [image]https://lh5.googleusercontent.com/-0o7mQRgYIVc/UDUS_04070I/AAAAAAAAAHM/G1UQv86fnBY/s912/DSC09862R1.jpg[/image] [image]https://lh5.googleusercontent.com/-RAZv814IcNw/UDUTAbjW3hI/AAAAAAAAAHY/QjKrFE2Rm60/s912/DSC09866R1.jpg[/image]
Posted on: 8/22/2012 10:51 AM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11202270

RE: One Pound residual thrust too high for an 18 pound Tams 1/8th F-16?
Half pound difference is considerably big enough for your jet's landing speed but it's useful when landing at high alpha where you might need more power on final. If you can increase your wing camber during final would be the best otherwise stick on using angle of attack to increase drag and slow her down.
Posted on: 8/11/2012 2:21 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11189605

RE: Where do I put my gyro?
It’s been days already since last updates I’ve got… Yeah mr_matt, that’s what I’m talking about… I agree that a wise man always finds a reason to respect his opinion... Keep up the good works and I appreciate all the inputs here...! The most important thing is we can locate the gyro in the best way in favor or convenient for us as it was written here… Very much stated at the closing remark of David...
Posted on: 7/17/2012 7:30 AM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11158531

RE: Where do I put my gyro?
My mistake, I didn't read that he wants to keep gyro away from carbon fiber unless to use a metal bracket under it. As I was understood from the latest comment it pertains to use conductive plate similar to metallic plate or carbon fiber. Now I have to explain, anyway I posted a fair statement about the conductive plate that it can protect, not help or cause interference depending on the situation. For example if we have existing conductive part of our airframe, this means that it has nothing to do with radio signal. If the area is big then there's nothing wrong if we install gyro or any new electronics close to the area, except with antenna or radio Rx unless tested of free radio interference. Size and distance of the plate determines the resonance frequency that the interfernce may cause. Larger the area metal plate, including carbon fiber most likely to dissipate signal and interference energy. On metallic materials may dissipate or bounch when energy are absorb caused by charges, dicharges or induce voltage... My apologize HarryC and thanks for comment!
Posted on: 7/13/2012 8:10 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11154491

RE: Where do I put my gyro?
I just gave that point to FB as my opinion about his understanding due to the way I see his application of the plate. I also gave balance information with regards to the reality of the plate except for their differences and it's not my invention, I learned that decades ago from electromagnetics...
Posted on: 7/13/2012 5:56 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11154360

RE: Where do I put my gyro?
I forgot, when moving CG back: Because of its nature, high wing loading and the ability of the gyro to compensate, airspeed must not fall below its safe limit. For that reason I believe the recovery from stall would be harder also...
Posted on: 7/12/2012 4:16 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11153106

RE: Where do I put my gyro?
[quote]ORIGINAL: BarracudaHockey [quote]ORIGINAL: rctech2k7 ''the gyro is the center of its rotation'' shortest very well explanation... [/quote] hehe thanks! I worked on a few bits and baubles in the Navy that used these gyro thingys ;) [/quote] It's helpful cause I'm trying to figure out the simplest way to explain it, hopefully it's clear now. That's
Posted on: 7/12/2012 3:31 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11153070

RE: Where do I put my gyro?
Another good reason for installing a gyro on a particular axis is to make it unstable, for example: pitch. Move CG aft slightly so that the aircraft can become more maneuverable, lesser stab load, shorter takeoff, etc. then install gyro to regain stability.
Posted on: 7/12/2012 3:21 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11153058

RE: Where do I put my gyro?
"the gyro is the center of its rotation" shortest very well explanation... With regards to carbon fiber and metal plate, FenderBean has a point due to electrical properties of the materials... In order for a conductive plate to work as a shield from electrical interference it must be grounded. Due to the size of the plate compare to the size of micro electronics it becomes the target of interference. But since it's not properly grounded it may work in two ways, either to dissipate that energy or becomes a device use to catch that energy and bounce it to nearby device which maybe harmful to very sensitive signal on the ckt. Shielding is very helpful if installed properly to protect a certain device but in most cases we don't need it. If the equipment is noise sensitive then the manufacturer will provide its own shielding for their equipment. There's nothing wrong if we provide one for our gyro a long as it's common grounded with gyro and may not interfere radio signal path.
Posted on: 7/12/2012 2:52 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11153023

RE: Where do I put my gyro?
I’m not sure if I can help to explain a little bit more. Consider the horizontal line where we used to calculate for CG and aerodynamic center of our aircraft. We can use any point along the line as a reference for pitch rotation to calculate and come up the same moment even if the point is outside the aircraft...
Posted on: 7/12/2012 5:51 AM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11152363

RE: Where do I put my gyro?
To answer OP, for me is to use one axis primarily on ailerons, second is depending or your requirements. For takeoff you might need directional stability but not in the air for banking turns. For pitch sensitive aircraft you might need one otherwise better to have natural stability for now...
Posted on: 7/10/2012 9:48 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11150927

RE: Where do I put my gyro?
FenderBean, your post became heated discussion, don’t worry about that, it’s not a wrong answer, you can say that as I can also say that it’s in the center of lift somewhere in the center of wings and the fuse. Let’s say center of roll and pitch axis. However, the things they've said are right, wherever we go on the line of axis it’s all the same angle or slope, the rate that the angle is changing are the same all throughout the axis. The only difference they have is the arc generated. The arc length is longer as it goes away from the reference point or center but the rate of change with respect to the center are the same, meaning directly proportional. Reference point and intersection of more than one axis could be anywhere cause each axis can rotate independently with the other axis on its dimension... So far I’m still learning with this micro tech gyros but IMO it detects rotation about an axis that is used to maintain orientation.
Posted on: 7/10/2012 9:23 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11150897

RE: Flying in adverse weather conditions
I agree, energy is what it makes an aircraft better on high wind which mostly mixed with gust. On the ground we can see our jet stands against wind and gust because of the weight specially when loaded with fuel. Since most jets has lesser surfaces and drag, they can stand higher wind strike limited to structural capability, landing speed and the amount gust IMO. Another factor is stability, jets are naturally stable compare to other models because of the CG location. However artificial or electronic stabilizer I believe are now available. But without other means massive nose heavy aircraft are better.
Posted on: 6/22/2012 8:21 PM by Author "rctech2k7" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=11128395

RE: Why this is the best hobby in the world
Welcome doc to this wonderful hobby which for me also is the best hobby and recreation... Glad to know a medical related person likes also this hobby, I'm a technically inclined person with engineering background... This hobby doesn't stop there, it's also part of science. It's continuously developing technology and a masterpiece of generations... Just like equipment you used in hospital, very sophisticated now a days... As a former athlete it's also my vitamins to keep my blood stream at high energy level during busy days. This hobby compose of many fields of technology, science and engineering. It's a never ending flow of experience and knowledge. This hobby connects me to many people at different walks of life and most especially to our Creator. This hobby can be related to many aspect of our transportation specially aerospace where it has a very complex application. Not just about technology but the beauty of nature, when we look to the sky and around us. The linkage between the airplane and pilot, the beauty of apperance in the sky while holding energy, pride and joy of owner, builder and designer...
Posted on: 6/21/2012 3:48 PM by Author "rctech2k7" in the forum "Beginners"
http://www.rcuniverse.com/forum/fb.asp?m=11127042

RE: If you could only have FIVE airplanes, what would they be?
I usually maintain and fly 2 airplanes and if it's 5 then 3 would be additional and not existing. 1. Skymaster - Xtreme Jet F-18 Hornet 2. CMP Cessna 182 Skylane 3. PZ Icon A5 or light model that can be used for FPV, AV, AP and test plane. 4. F-15, F-16 or another F-18 (not existing) 5. 747 airliner (not existing)
Posted on: 6/8/2012 3:31 PM by Author "rctech2k7" in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=11111631