Speed and rate of turn

[ISaidRightTurns]

I was running out of a holding pattern today. My canned clearance is H130 S250 kts. I started bending this one 75 towards the arrival and he just wasn't turning fast enough. Someone said if you resume his speed, he will turn faster. Then I can just give him a crossing restriction for what I need.

Doesn't make sense to me. If an a/c speeds up, will it turn tighter, at least get over to an assigned heading. This of course assumes the pilot is doing something other than standard rate. I've never flown anything that big, so I have no clue what a turn rate would be. 1/2 SR?

 

[Yellow Snow]

Yep constant rate of turn = tighter radius at higher speeds. Three degrees per second in standard rate means much more bank at 200 than at 90

 

[ISaidRightTurns]

But if he was in a 1/3 or 1/2 stanadard rate turn at 250 kts, and told to resume, think most heavy pilots would increase the rate of turn?


Like I said, doen't make sense to me.

 

[TonyC]

But if he was in a 1/3 or 1/2 stanadard rate turn at 250 kts, and told to resume, think most heavy pilots would increase the rate of turn?


Like I said, doen't make sense to me.

It probably doesn't make sense to you because you're thinking about it all wrong. You're thinking rate of turn, and the pilot is most likely thinking 30 degrees of bank. Slow him down and the same 30 degrees of bank will get you a better rate of turn. If your object is to change his heading quickly, slow him down.




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[gern_blanston]

...constant rate of turn = tighter radius at higher speeds. Three degrees per second in standard rate means much more bank at 200 than at 90

Higher speed at constant rate = higher bank angle not tighter radius.

But if he was in a 1/3 or 1/2 stanadard rate turn at 250 kts, and told to resume, think most heavy pilots would increase the rate of turn?

Most modern jets don't even have any indication on the panel of what their rate of turn is. Most flight directors use 25 degrees of bank for turn cues, so if the guy's following the flight director, he's probably in a 25 degree bank. Speeding him up will slow down his rate of turn and increase the radius of his turn.

 

[EagleRJ]

What altitude was this at? Most pilots will select 1/2 bank mode above 30,000' or so to increase stall margin, and most modern autopilots will do it automatically.

On autopilot, most aircraft will be banked 25-27 degrees at terminal area altitudes, and slowing them down will reduce their radius of turn. Their rate of turn will improve a little too.

 

[Yellow Snow]

What I think I was trying to say was increase the speed you get steeper bank and tighter turn. If i am mistaken (probably) please explain so I can get it. Not in jets yet so I don't fully understand all the aero involved but I understoood (possibly incorrectly) that higher speed with constant rate made tighter radius turns due to larger bank angles.

 

[TonyC]

What I think I was trying to say was increase the speed you get steeper bank and tighter turn. If i am mistaken (probably) please explain so I can get it. Not in jets yet so I don't fully understand all the aero involved but I understoood (possibly incorrectly) that higher speed with constant rate made tighter radius turns due to larger bank angles.

The method of propulsion is irrelevant. In order to maintain the same RATE OF TURN (heading change per time) while increasing airspeed, the bank angle must be increased. The turn radius will also be increased. Think of this: If the rate of turn is 180 degrees per minute, it will take 2 minutes to fly a complete circle. If you travel at a slow speed, the circle will be small. If you travel at a fast speed, the circle will be large. Small circle, small turn radius. Large circle, large turn radius.


Now, to keep the turn RATE constant as airpseed increases, one must increase the bank angle. Since pilots will typically be flying a bank angle (which, as some have correctly pointed out may be limited by the autopilot at altitude) instead of a turn rate, the way to change TURN RATE is to change airspeed.



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[Yellow Snow]

Ahh I see. Well that is simple I got it now. Thanks!

 

[gern_blanston]

What I think I was trying to say was increase the speed you get steeper bank and tighter turn. If i am mistaken (probably) please explain so I can get it. Not in jets yet so I don't fully understand all the aero involved but I understoood (possibly incorrectly) that higher speed with constant rate made tighter radius turns due to larger bank angles.

Rate, bank, and radius are all completely different animals that all come together when you go around a corner.
Exaggerating works great for demonstrating this kind of stuff. Here's a demo: Go find a parking lot somewhere and walk a standard rate turn. 2 minutes to do a 360 walking at 4 knots and you're gonna carve a circle with a radius of, say, 127 feet. If you are flying that circle with a plane (probably better use a slow-flying model!) the bank angle is gonna be miniscule. Now, go drive a standard rate turn in your car at 50 knots. Your radius is gonna be nearly 1600 feet. If you're flying, your bank angle's gonna' be a bit steeper. Imagine what it'd be like travelling at SR-71 speed. Anybody calculate the g-loading to make a standard-rate turn work at 1800 knots?!? If you could do it, the radius would be 30 nautical miles and the bank angle would be close enough to 90 that the difference is negligible. So as you increase speed while holding your turn rate, your bank angle and your turn radius have grown substantially, but you're still doing a 'standard-rate' turn.