rctech2k7

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Very informative guys, it reminds me of a frictionless banking turn... The normal (perpendicular) force (N) acted on the surface bottom of an aircraft has 2-components (vertical and horizontal). Vertical component is the cosine of banking angle while horizontal is sine of that angle. It leaves the vertical equation as follows:

Weight = N * cos (angle)

Therefore:

N = (1/ cosine angle) * W

karl hibbs

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http://www.bvmjets.com/images/Enclosure1.pdf

highhorse

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With respect, you are incorrect sir. Mr Gladwin has it spot on with regard to a LEVEL turn of x degree bank always equals y G's. That is one thing every aviator is taught in his first ground school and there are literally thousands of references available in this regard.

alasdair

David Gladwin is correct about the Physics of turning, IF the turns are dead level and correctly banked and properly balanced, as when flying full size aeroplanes with precision, as he was trained to do.
A hooligan flying a model jet is not so constrained, and so may pull almost any 'g' he likes when he changes flight direction abruptly.

I have fitted a few of my jets with instrumentation, including Eagle Tree's pressure based system linked to a G meter that records constantly, and also a GPS position recorder that will also output speed (as a differential of position).
|I found that the GPS based readouts were unreliable in manoeuvres, but were OK in long straight sections of flight if bank angle was kept reasonable (but a roll messed up the GPS completely).
One problem with Eagle Tree equipment was in finding a reliable static pressure source to drive the altimeter and airspeed indicator.   Total pressure from a pitot is easy enough but neither the cabin pressure nor the pitot head supplied were accurate enough.
For example, in a high speed full throttle pass my EagleTree airspeed was about 100 mph and height was -80 feet.  That height was patently not  true, as by eye the model was 10 feet ABOVE the runway, and GPS readings suggest that the actual airspeed was nearer 120 mph (averaging upwind and downwind GPS speed).
I am still looking for a reliable static source, as I believe that the units are very accurate, if fed reliable pressure information.

My CARF Lightning powered by a Booster 160 had a Weatronic RX fitted  (on 35 MHz) which included a built in GPS. Its twin aerial system had a far more reliable GPS lock-in that seldom lost signal, and its speed readout on a fast pass was 170 mph (averaged up and down wind). A big loop reached 1500 feet (in military airspace with ATC permission). No G meter was fitted but I am glad the wing tube resembles a scaffolding pole!

Tony Iannucelli

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Flying the Chinese stuff I guess you'd call it. An Evader, an F-16, a StrykerQ, a Projeti, and some others. With most of them, split esses are the norm. Using the low reading Eagle Tree I get between 4-7 Gs on all three axis. I've broken 1,000 feet with the Stryker (with the permission of the Tower). They fly really well. There really is no need to spend thousands of dollars any more for me. Trust me, the same rush is available for a couple of hundred bucks. And because they are small, the challenge is greater.

So, do tell, the 3D helis must be pulling 50gs........

blhollo2

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This just proves my "theory" that these planes can handle more "G's" and stress than most people think. Its really amazing when you put this information in perspective thanks!

FILE IFR

Airplanes is missing the point of a turn being a COORDINATED turn.

He's going by the old 'Bank-n-Yank' way of turning an airplane.

Airplanes400

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Thanks blhollo,
That's the basic point I was trying to show ... That our R/C planes and jets go through more G forces than we realize, and the readings I got from the meters demonstrate it. None of us can say for sure if our planes are in a 50°, 60°, or 70° angle of bank from our perspective, so that would only be a guess on anyone's part, or if in fact, the plane stayed at the same altitude during the turn. In all liklihood, they never do.

Regardless of all this, the end result is that our planes sustain more stress than we realize, and the meters prove it.

chuckk2

I'm not surprised at the higher than expected "G" readings encountered in R/C aircraft.
Compared to full scale aircraft, the typical R/C model has larger control surfaces, more deflection available, and a higher power to weight ratio.

Neglecting compressibility, a 1/8 scale R/C model at 100mph might be compared to a full scale A/C at 800mph.

An example of a high performance full scale aircraft might be an F-15A fighter in the late 70's. Pilots were routinely going over the desired "G" forces, resulting in such things as engine flame-outs,
antennas on the vertical stabilizers breaking or falling off, and even entire vertical stabilizers cracking at the base and falling off. To this day, even on the later F-15 versions, major structural repair
is often needed during overhaul. Repeated high G forces are believed to be the major cause.
The "G" sensors mounted in the "belly" of F-15As were often "tripped" when a plane returned, and the trip level was about 8G.

cfircav8r

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The F-16 has the "Falcon up" program that tracks G loads and configuration to maintain a proactive approach to stress. You will see many added structural "patches" depending on the age and stresses encountered. Fourth generation fighters are for the most part limited by the airframe, but fifth generation fighters are mostly limited by the pilot, depending on configuration.

rctech2k7

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I forgot the horizontal component of N on banking curve which is expressed in N * sine (angle) equal to centripetal force (Fc).

Fc = m *v^2 / radius of turn

This centripetal force is directly proportional to the square of velocity and inversely proportional to the radius of turn.

Fc = N * sine (angle)

Therefore;

N = m *v^2 / (radius of turn * sine (angle))

On the first equation: N = W/cos(angle), as angle of bank approaches to 90-deg, N load is becoming critical as it increases rapidly.

The third equation which derived from equating 1 and 2:

v^2 = r * g * tan (angle)
where: g = gravitational constant

It implies that, when velocity (v) increases, radius of turn must increases otherwise angle of bank must increase and therefore result in increase of load factor at constant radius of turn. This is what I believe explaining by Airplanes400


And this is what I believe trying to implied by David Gladwin, the ratio of N and the weight of an aircraft is higher at higher angle of bank and 1 at zero angle. This is proved by equation of a right triangle with hypotenuse N and constant adjacent leg of Weight (W). As the angle of bank increases N is also increases as opposite leg increases and W is constant. Using right triangle formula, cosine (angle) = W/N.
Reciprocating the formula,

N/W = 1/cosine of angle

Is a load factor or the ratio of lift acceleration to gravitational constant (g), where N = total lift generated by an aircraft at angle of bank and W = weight

icepilot

I have used some Eagle Tree products, they are inexpensive and work well, I might try one of their G-meters just out of curiosity!

stoneenforcer

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thanks for posting.