# How many G's?

mlprior
Science 09 Jul '08 18:50
1. 09 Jul '08 18:50
When you are traveling at an airspeed of about 180 knots (or say 300 km/hr) for our calculation purposes, and you enter a 60 degree angle of turn. How many g's are you in?
Assuming you are holding altitude and airspeed constant through a 360 degree turn.

This is something that I think about often....
2. Wheely
Instant Buzz
09 Jul '08 19:46
Originally posted by mlprior
When you are traveling at an airspeed of about 180 knots (or say 300 km/hr) for our calculation purposes, and you enter a 60 degree angle of turn. How many g's are you in?
Assuming you are holding altitude and airspeed constant through a 360 degree turn.

This is something that I think about often....
I counted five but I might have missed one or two.
3. sonhouse
Fast and Curious
09 Jul '08 20:302 edits
Originally posted by mlprior
When you are traveling at an airspeed of about 180 knots (or say 300 km/hr) for our calculation purposes, and you enter a 60 degree angle of turn. How many g's are you in?
Assuming you are holding altitude and airspeed constant through a 360 degree turn.

This is something that I think about often....
S
I don't think its quite worded right. The equations for centripital force (the outward force) needs the radius of the turn, which you can probably derive from the given data, at least I think it can, but 'you enter a 60 degree turn' doesn't sound like enough data. So you can make an assumtion or two to get the radius I think. For instance, you make a 60 degree change of direction but how many seconds does that take? And is it a 60 degree turn or a 360? If you know the radius of the turn, you can think about this:
You are at some point in time going to reach the 90 degree point, so that represents stopping in one dimension and starting to move in another dimension, stopping the forward flight and starting a left to right acceleration. Does that make sense? Thats why you need the radius or the time it takes to do that. If you start into a turn and do 90 degrees in one second and you are going 300 Km/hr (83 meters per second) then you are effectively stopping in one second, or 83 meters per second per second which is about 8 G's. If it takes 10 seconds to make the same turn, then you are doing 1/10th of that or 0.8 G.
See why you need more information? (1 G is 9.8 meters per second per second which you can round off to 10 for sure to make the calc easier, so 83/9.8 is 8.5 G's, assuming the change takes place in one second.
If it takes 2 seconds then it's just 8.5/2 or 4.25 G's so you really need that time)
4. 09 Jul '08 20:40
Originally posted by sonhouse
I don't think its quite worded right. The equations for centripital force (the outward force) needs the radius of the turn, which you can probably derive from the given data, at least I think it can, but 'you enter a 60 degree turn' doesn't sound like enough data. So you can make an assumtion or two to get the radius I think. For instance, you make a 60 deg ...[text shortened]... d.
If it takes 2 seconds then it's just 8.5/2 or 4.25 G's so you really need that time)
I can always count on you, Sonhouse to make things so much more complicated than they actually are.
ðŸ˜‰

I could specify a little more in this way. The angle of the wing to the horizon is 60 degrees. You are doing a turn around a point in space starting at north and ending up again at north (360 degrees). Your airspeed indicates 300 km/hr.
Does that help?
5. sonhouse
Fast and Curious
09 Jul '08 22:24
Originally posted by mlprior
I can always count on you, Sonhouse to make things so much more complicated than they actually are.
ðŸ˜‰

I could specify a little more in this way. The angle of the wing to the horizon is 60 degrees. You are doing a turn around a point in space starting at north and ending up again at north (360 degrees). Your airspeed indicates 300 km/hr.
Does that help?
It doesn't matter, you can always analyze it in terms of how many seconds does it take to turn 90 degrees, thats the key. That's not exactly rocket science, just freshman physics.
6. 09 Jul '08 22:34
Originally posted by mlprior
When you are traveling at an airspeed of about 180 knots (or say 300 km/hr) for our calculation purposes, and you enter a 60 degree angle of turn. How many g's are you in?
Assuming you are holding altitude and airspeed constant through a 360 degree turn.

This is something that I think about often....
Without calculation, I think 2 g would be reasonably.

With calculation: 1/cos(60) is exactly 2. I wonder if this is right.
7. sonhouse
Fast and Curious
09 Jul '08 23:16
Originally posted by FabianFnas
Without calculation, I think 2 g would be reasonably.

With calculation: 1/cos(60) is exactly 2. I wonder if this is right.
Like I said, if it takes one second to change angles by 90 degrees at 300Km/hr, it's 8.5 G's. If ten seconds, 0.85 G's. Not exactly Phd level stuff here.
8. forkedknight
Defend the Universe
10 Jul '08 18:40
Originally posted by mlprior
I can always count on you, Sonhouse to make things so much more complicated than they actually are.
ðŸ˜‰

I could specify a little more in this way. The angle of the wing to the horizon is 60 degrees. You are doing a turn around a point in space starting at north and ending up again at north (360 degrees). Your airspeed indicates 300 km/hr.
Does that help?
The angle of your wings to the horizon doesn't really tell you how fast you are turning; you could be sliding laterally on the air as well.

You really do need how many degrees/second or radius of the turn to tell you what centripetal acceleration you are experiencing.
9. 11 Jul '08 04:41
Originally posted by FabianFnas
Without calculation, I think 2 g would be reasonably.

With calculation: 1/cos(60) is exactly 2. I wonder if this is right.
You are absolutely correct Fabian!

A 60 degree turn will pull a load factor of 2 g.

Load factor = lifft/weight = 1/cos(bank angle) = 1/cos(60)

Exactly as you stated!

ðŸ˜‰
10. 11 Jul '08 05:55
Originally posted by mlprior
You are absolutely correct Fabian!

A 60 degree turn will pull a load factor of 2 g.

Load factor = lifft/weight = 1/cos(bank angle) = 1/cos(60)

Exactly as you stated!

ðŸ˜‰
Yezz!

But I don't understand where "an airspeed of about 180 knots" or "through a 360 degree turn has to do with anything...? That confused me and therefore I didn't know if my answer was right in this situation...

But 1/cos(angle) does work in various situations:
Bicycle or mtorcyckle turn, where you 'bank' in relation to your turn.
Various attractions at the amusement parque.
Even when you run through narrow corridors at the office. Well, 60 degrees 'banking' perhaps is not very usual, but the same formula applies.

What about USS Enterprice in StarTrek banking 60 degrees in open space to make an areodynamically correct turn...?
11. sonhouse
Fast and Curious
11 Jul '08 06:30
Originally posted by FabianFnas
Yezz!

But I don't understand where "an airspeed of about 180 knots" or "through a 360 degree turn has to do with anything...? That confused me and therefore I didn't know if my answer was right in this situation...

But 1/cos(angle) does work in various situations:
Bicycle or mtorcyckle turn, where you 'bank' in relation to your turn.
Various attra ...[text shortened]... n StarTrek banking 60 degrees in open space to make an areodynamically correct turn...?
This does not seem right to me. If you are driving around a bank of 60 degrees, you say the load is 2 G's but it still seems velocity dependent. If you are going 2 Km/hr you would get a lot less G load than if you are going 200 Km/hr. If the 2 G load is correct it looks like it takes 17 seconds to complete 360 degrees.
12. 11 Jul '08 06:35
Originally posted by sonhouse
This does not seem right to me. If you are driving around a bank of 60 degrees, you say the load is 2 G's but it still seems velocity dependent. If you are going 2 Km/hr you would get a lot less G load than if you are going 200 Km/hr. If the 2 G load is correct it looks like it takes 17 seconds to complete 360 degrees.
Not if you're right on the wings. If so then the velocity doesn't matter.
The same rule apply to a supersonic attacker, a Concorde in Mach 1.5, a lightweight 2 hp engined hobby flyer, a deltawinged airglider, or even a bumblebee.
13. sonhouse
Fast and Curious
11 Jul '08 06:52
Originally posted by FabianFnas
Not if you're right on the wings. If so then the velocity doesn't matter.
The same rule apply to a supersonic attacker, a Concorde in Mach 1.5, a lightweight 2 hp engined hobby flyer, a deltawinged airglider, or even a bumblebee.
How is it different driving around a banked turn at 60 degrees and flying through a banked turn at 60 degrees?
14. forkedknight
Defend the Universe
11 Jul '08 14:32
Originally posted by sonhouse
How is it different driving around a banked turn at 60 degrees and flying through a banked turn at 60 degrees?
The motocycle analogy makes a lot more sense to me as to why you could get the centripetal force based on the angle. If you maintain a 60 degree angle to the ground, it will take a determinate lateral force based on gravity to maintain that angle.

If you're going 2 km/hr while leaning over to 60 degrees, you will turn MUCH faster than if you are going 200 km/hr, but the centripetal force will be the same.

Translating that to an aircraft, I was having difficulty determining the physics needed to maintain a perfect radius at a precise altitude. From experience, I know that angling the wings to the ground does not necessarily cause the plane to turn at all -- instead you will keep the same heading and start sliding sideways (and downward) through the air. I can see that if you were also to keep the same groundspeed (not airspeed) and the same altitude, your angle of turn would determine the centripetal acceleration.

In conclusion, realistically, it would not be feasibile to "try this at home" and get precise results.
15. shavixmir
Guppy poo
11 Jul '08 21:06
Originally posted by mlprior
This is something that I think about often....
Really?

The only time I think about G's is when I'm down on a girl.