MANUVERING SPEEDS

[EDMO 1078]

Twin Soob's....cool

I'm the same,keep a stable approach speed

then flare is all out the window

DAR/FAA Question: In order to pass the airworthiness inspection, all instruments have to be marked?

Well, I can mark my never excede speed (red line) my flaps operating range (white arc), and my caution range (yellow arc), and the upper part of my green arc - but not knowing stall speeds before testing, how can one mark the lower end of the ASI without flight testing first?

Guestimate, and correct later???

NOTE: mine is scratch-built - not factory standard.

ED in MO

Edited 11 May 2012 by Ed In Missouri

[John_L_Seagull 0]

Stall speed can be calculated

stall speed = 3.7 * square root of wing loading

This would be for straight and level flight in cruise of coarse,

steep turns would increase the stall factor

[EDMO 1078]

Stall speed can be calculated

stall speed = 3.7 * square root of wing loading

This would be for straight and level flight in cruise of coarse,

steep turns would increase the stall factor

This would be clean, I guess? What about varing degrees of flaps? Is this at gross weight? Should be less at lighter weights?

Lots to consider here.

Thanks for formula. but it don't compute in my mind: Wing Loading of 9, square root = 3 x 3.7 = 11 aprox mph stall?

What if your wing loading was 6?

Wouldn't the Coefficient of lift have to be used in this calculation? It can vary from 1.3 clean to above 2.0 flapped.

And how about Reynolds numbers in the formula? Lift slope? planform, etc?

Seems to me, that there are a lot of variables in calculating stall speed: Don't see how one formula can fit all.

Ed in MO

Edited 12 May 2012 by Ed In Missouri

[John_L_Seagull 0]

Yes clean,in level flight

The formula to calculate stall speed is:

V = √( 2 W g / Ï S Clmax )

V = Stall speed m/s

Ï = air density KG/m^3

S = wing area m^2

Clmax = Coefficient of lift at stall

W = weight KG

The formula accounts for altitude being input,of the appropriate air density figure

The term stall speed is misleading though,

because speed really has very little to do with when a wing will stall

Stall's occur because of angle of attack

Stall speed, as calculated with the above formula only works for straight and level flight

The wing will stall at a much higher speed, if the plane is maneuvering such as a steep turn as this will cause G-loading which in way increases the planes weight

If you know the G-loading,

then you can factor that into the stall speed formula with increasing the gravitational G constant

either way,it can be calculated

Edited 13 May 2012 by John_L_Seagull

[EDMO 1078]

Yes clean,in level flight

The formula to calculate stall speed is:

V = √( 2 W g / Ï S Clmax )

V = Stall speed m/s

Ï = air density KG/m^3

S = wing area m^2

Clmax = Coefficient of lift at stall

W = weight KG

The formula accounts for altitude being input,of the appropriate air density figure

The term stall speed is misleading though,

because speed really has very little to do with when a wing will stall

Stall's occur because of angle of attack

Stall speed, as calculated with the above formula only works for straight and level flight

The wing will stall at a much higher speed, if the plane is maneuvering such as a steep turn as this will cause G-loading which in way increases the planes weight

If you know the G-loading,

then you can factor that into the stall speed formula with increasing the gravitational G constant

either way,it can be calculated

John, can you translate that into American? What is the "^"? (Nevermind that question: I know it must mean you couldnt print a little 2 or 3 for squared or cubed.) Old flyers dont use sillymeters - only drug dealers and foreigners use Kg.

I would be glad to put this to use if you can put it into our terms.

I know engineers and scientists also use those terms, but most of us are just flyers.

Thanks.

But I garantee, that if I started telling how many Kilos I could put in my plane, the Federales would be all over me!!!

Ed in MO

Edited 13 May 2012 by Ed In Missouri

[John_L_Seagull 0]

only drug dealers and foreigners use Kg.

I guess I would fall under the later category then of being a foreigner, as I'm from Canada

we gave up the standard system ... oh,roughly 30 some years ago

I'll see if I can translate it for you

[EDMO 1078]

I guess I would fall under the later category then of being a foreigner, as I'm from Canada

we gave up the standard system ... oh,roughly 30 some years ago

I'll see if I can translate it for you

We had to start to endure it about then - forced to it for trade purposes. Ended up having to pack a set of American tools and a set of metric tools in my truck because it had both kinds of bolts in it. I think my French cousins, (and others) really stuck it to us on that!

Now my plane has two sets, with a Jap engine and AN bolts in the rest!!!

I was a machinist - used to working in thousanths, and ten-thousanths of an inch. Metrics were a pain to convert!

It is a foreign system to us old-timers.

I experienced being a foreigner in your country many times starting some years ago:

I couldn't set the thermostat in my first motel room because is was Celcious - couldn't find anyone to translate it to Farenheiht for me either.

This is life, and we just have to make the best of it. Lesson: Carry conversion tables when traveling!!!

I could not find a number in my books to use for density of air at sealevel, 59 degrees F, if that is still standard day. Isn't that part of the formula - got to look at it again. If not, then disregard.

If that 3.7 formula you first gave is V= meters per second, then maybe I can convert that instead of the 11 mph that I thought was wrong. 11 m/s = Back to calculator.... OK - came up with 24.6 mph, and that is reasonable.

Thanks, ED in MO

Edited 14 May 2012 by Ed In Missouri

[John_L_Seagull 0]

Yup metric smeckret

I started school on standard and finished on metric lol

sure glad we still use standard barometric pressure in Aviation up here at least

rather than the kilo-pascals like on the news lol

yes sir,

59 degrees Fahrenheit(15 Degrees Celsius) @ barometric pressure 29.92 @ sea level

A perfect day

The first formula was a standard formula,

looking now I see I forgot to add that it was in MPH and oz/sqft

Here it is again>

stall speed = 3.7 * square root of wing loading

speed in mph

wing loading in oz/sqft

that may help eh!

Oh,BTW

That other formula

Just use "lb/ft^3" for density altitude rather than KG/m^3

the rest of the formula is relatively easy to convert to standard

Just do each other calculation in standard,

and use the above standard (lb/ft^3) calculation for Air Density ;0)

[EDMO 1078]

Yup metric smeckret

I started school on standard and finished on metric lol

sure glad we still use standard barometric pressure in Aviation up here at least

rather than the kilo-pascals like on the news lol

yes sir,

59 degrees Fahrenheit(15 Degrees Celsius) @ barometric pressure 29.92 @ sea level

A perfect day

The first formula was a standard formula,

looking now I see I forgot to add that it was in MPH and oz/sqft

Here it is again>

stall speed = 3.7 * square root of wing loading

speed in mph

wing loading in oz/sqft

that may help eh!

Oh,BTW

That other formula

Just use "lb/ft^3" for density altitude rather than KG/m^3

the rest of the formula is relatively easy to convert to standard

Just do each other calculation in standard,

and use the above standard (lb/ft^3) calculation for Air Density ;0)

OK - will work on all this for a while. Then make my red line guesstimate. Thanks for all the input.

I still have flashbacks to Physics 101, and all the Newtons, and other terms I cant remember, and my brain goes into shock!

Ed in MO

Edited 14 May 2012 by Ed In Missouri

[SuberAvid 617]

Nobody ever said that "Old pilot are smart pilots": Maybe old pilots sometimes cannot comprihend things that the young pilots are taught, like Va, Vb, Vc, and all those alphabet things that we older pilots have to say in longhand American.

I just read Barnaby's article in the new Sport Aviation mag, and I totally don't understand how a manuver or wind gust can overstress a plane at a lower weight and not at a higher weight. I follow all of his articles with intense interest, but am lost on this one. Looks like to me that if you are at max gross, then any strain on the wings could put you in danger faster than if you are lighter.

Can someone smarter than me explain this to where I can understand it?

Ed in MO

Hi Ed,

I know you recieved a lot of answers explaining this as the weight relates to angle of attack and stall speed but I read this article too and it tended to give one the impression that it is better to fly heavy in turbulence. What seemed to be left out of the discussion was the WEIGHT side of the equation. Sure the G forces are higher when you are light but the force on the wing may or may not be.

I don't claim to be anywhere near a smart a Barnaby or most other folks on this forum but I do know from physics that Force = Mass X Acceleration (F= MxA). In straight and level flight the lift force on the wing has to equal the weight of the airplane and in that case is equal to Mass x the acceleration of Gravity (W=M x g). Since gravity is constant, increasing the weight of the plane is equal to increasing the mass, so if a plane weighs 500 pounds the wing has to lift 500 pounds at 1g. If the wing is designed for 4g then the wing can lift 4 x 500 = 2000 pounds. If we increase the weight to 1000 pounds the wing can still handle 2000 pounds but this is only equal to 2g. So if we hit turbulence when the plane is light, it will cause greater acceleration forces (higher g's) but that still may not equate to higher loads on the wing than a heavier plane with lower acceleration forces (g loads). The impression from the article was I think unintentional, that a heavier loaded airplane would be safer in turbulence because it would be subject to lower acceleration forces. As we can see, this is not a silver bullet for us because it can only handle much lower acceleration forces because the other factor in the equation (mass) is already higher.

[EDMO 1078]

This is not the first article I have read regarding the cautions of gust loads with light aircraft, especially ultralights.

I believe that some of it is because they are not built as strong as the heavier ones?

ED in MO

[lv2plyguitar 172]

_{So leni if the vno is 85 what happens if I am crusing at 105.  is the danger only if I enter a maneuver at that speed?   I was doing 105 up the mat river valley the other night.}

[SuberAvid 617]

_{So leni if the vno is 85 what happens if I am crusing at 105.  is the danger only if I enter a maneuver at that speed?   I was doing 105 up the mat river valley the other night.}

Jeff,

 

Remember that the plane only feels the relative speed, which is the airspeed, not the speed over the ground that your GPS is showing. 

[C5Engineer 1170]

When did we become the RV forum....lol...?? .Here's my calculation...If the wings came off then you were going to fast!! I've also been in a situation where I slowed to 55mph indicated and was praying the wings stayed on. As far as experimentals go I think Avids and Kitfoxes are built like a brick shithouse. Correct me if I'm wrong but I believe there has NEVER been a strutural failure of either. This is the reason you don't see BRS chutes in them. I can tell you that Mountain wave turbulence at 11,500 feet in a fully loaded Avid SUCKS!! I was burying my VVI at 2000fpm up and down on an almost perfectly timed cycle for 45 minutes over the mountains in Northern CA. It was too late to do much about it by the time I realized what was happening and I didn't have the fuel to turn around and go back the way I came. Finally on one of the updrafts I poured the coals to it and busted out at 12,499 ft in smooth as glass air. Didn't pull the power off the firewall for another 75 miles to stay up there. Finally got into the Sac valley where I landed with a pounding headache and spent the night. Last time I ever do that little stunt!