Max Rate turn vs. Min Radius Turn
I'd be utterly astonished if the Cessna 152 had a +6g normal limit. I last flew the Cessna 150 about 40 years ago and recall that the ultimate load limit (the point at which it fell apart) was around that value. 6.6 g, was it?
Flying at CLmax (buffet nibble), full power and at the normal G limit will give the max turn rate / min turn radius in a light aeroplane; anything else will reduce performance. But trying to sustain more than about +4 g without training and a g-suit will probably induce g-loc and possible death.
Flying at CLmax (buffet nibble), full power and at the normal G limit will give the max turn rate / min turn radius in a light aeroplane; anything else will reduce performance. But trying to sustain more than about +4 g without training and a g-suit will probably induce g-loc and possible death.
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Prepare to be utterly butterly astonished........
Cessna 152 - Wikipedia, the free encyclopedia
Look under 'variants' - specifically the 'aerobat' version
Wikipedia is hardly conclusive but its the best I can find at short notice. I know for sure 'cause its placarded in G-BHEN (the aircraft I usually fly) and stated quite clearly in the POH - not that I have been anywhere near that!
As I understand, to be categorised as aerobatic under FAA certification requirements, the aircraft must be capable of +6, -3 limit (not ultimate) loads....so it is.
Cessna 152 - Wikipedia, the free encyclopedia
Look under 'variants' - specifically the 'aerobat' version
Wikipedia is hardly conclusive but its the best I can find at short notice. I know for sure 'cause its placarded in G-BHEN (the aircraft I usually fly) and stated quite clearly in the POH - not that I have been anywhere near that!
As I understand, to be categorised as aerobatic under FAA certification requirements, the aircraft must be capable of +6, -3 limit (not ultimate) loads....so it is.
Last edited by Simon150; 18th Jan 2009 at 21:30.
Thanks for that..... 
!! I remember the +4.4 g limit for the things I flew, with a fail limit of 150%, equating to +6.6 g.
I would very strongly dissuade anyone from trying to fly a sustained +6 g descending max rate turn on the buffet nibble in a Cessna 'Aerobat' though!
Even if the aircraft could manage it, the pilot would probably lose consciousness quite quickly. Not something you would want to happen in a descending max rate turn.....
Nope - we're all equals!
!! I remember the +4.4 g limit for the things I flew, with a fail limit of 150%, equating to +6.6 g.I would very strongly dissuade anyone from trying to fly a sustained +6 g descending max rate turn on the buffet nibble in a Cessna 'Aerobat' though!
Even if the aircraft could manage it, the pilot would probably lose consciousness quite quickly. Not something you would want to happen in a descending max rate turn.....
Beagle and rapiddescent, we mere mortals are on a lower plane than you chaps
Last edited by BEagle; 19th Jan 2009 at 09:11.
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Beagle and rapiddescent, we mere mortals are on a lower plane than you chaps
Nope - we're all equals!
Nope - we're all equals!
The text book answer (Australia - civil) is/was min radius/max rate to be flown at Va and max "g", but recognising that power to sustain would in all likely hood not be available.
Beags, you are quite right in that your 150 had a g limit less than 6, the Aerobat version was beefed up for the aerobatic role.
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The reasons
The max rate/ min radius is to be considered in level fligth only.
Rate of turm is indirectly proportional to airspeed, and directly proportional to angle of bank. That is simply put, the higher you airspeed the lower is you rate of turn, and the higher your angle of bank, the higher your rate of turn.
Radius of turn is directly proportional to airspeed and indirectly proportional to angle of bank. Put simply once again, the higher your airpseed, the larger is your radius of turn and the higher your angle of bank, the lower your radius of turn.
In order to achieve your lowest airspeed, in level flight, you must be configured with gear up, and full flap. You must then roll into the turn and apply full power,(to lower your stall speed further). Remember he stall anlge is the same for your configuration. When you are immediately at the critical angle, and holding it, in level flight, you will then be at max rate and min radius.
It is all very elementary, but can be made as complex as you want, the basic facts however, are always right!!
best wishes.
Rate of turm is indirectly proportional to airspeed, and directly proportional to angle of bank. That is simply put, the higher you airspeed the lower is you rate of turn, and the higher your angle of bank, the higher your rate of turn.
Radius of turn is directly proportional to airspeed and indirectly proportional to angle of bank. Put simply once again, the higher your airpseed, the larger is your radius of turn and the higher your angle of bank, the lower your radius of turn.
In order to achieve your lowest airspeed, in level flight, you must be configured with gear up, and full flap. You must then roll into the turn and apply full power,(to lower your stall speed further). Remember he stall anlge is the same for your configuration. When you are immediately at the critical angle, and holding it, in level flight, you will then be at max rate and min radius.
It is all very elementary, but can be made as complex as you want, the basic facts however, are always right!!
best wishes.
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When you are immediately at the critical angle, and holding it, in level flight, you will then be at max rate and min radius.
It is all very elementary, but can be made as complex as you want, the basic facts however, are always right!!
It is all very elementary, but can be made as complex as you want, the basic facts however, are always right!!
Rate of turn is, as you say, a function of AOB/V.
But radius of turn, contrary to what you say, is a function of V^2/AOB.
In consequence, as has already been explained by BEagle and myself, the speed for maximum rate of turn is higher than the speed for minimum radius. And it's not possible to have a sensible discussion on this topic without considering limit load factors and also power available. Which makes it not quite so elementary.
Last edited by Islander2; 21st Jan 2009 at 14:57.
If you absolutely positively want to turn 180 degrees in the minimum distance you have to do a hammerhead.
Beags,but which one uses least airspace ?
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It is elementary
Lads, it is ever so elementary.
Limit turns, are dependent on the particular aircraft. A higher g loading does not mean a higher rate of turn. At least thats what I was taught thanks to Her Majesty. First rule, If you want to out turn someone my boy, min speed, max bank, max power, sit in stall buffet.
On a more practical note for you boys who havent flown an aircraft that goes faster than 700kts, full flap, min speed, max bank, and max g up the point of stall. Max rate and Min Radius are one and the same. Check your books.
The basics are the same, the rules dont change, keep it simple and you will never go wrong!
Best of Luck!! And keep trying!!
Limit turns, are dependent on the particular aircraft. A higher g loading does not mean a higher rate of turn. At least thats what I was taught thanks to Her Majesty. First rule, If you want to out turn someone my boy, min speed, max bank, max power, sit in stall buffet.
On a more practical note for you boys who havent flown an aircraft that goes faster than 700kts, full flap, min speed, max bank, and max g up the point of stall. Max rate and Min Radius are one and the same. Check your books.
The basics are the same, the rules dont change, keep it simple and you will never go wrong!
Best of Luck!! And keep trying!!
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Max rate and Min Radius are one and the same. Check your books.
"The speed for maximum rate of turn is that which corresponds, on the minimum radius of turn graph, to the point where a tangent from the origin just touches the minimum radius curve. Fig 3 shows that, at any given altitude, this speed is higher than the speed for minimum radius."
Lads, it is ever so elementary .... Best of Luck!! And keep trying!
Edited to correct for finger trouble: somewhat obviously, minimum radius of turn graph was mis-written as minimum rate of turn graph. Apparently, that makes me "a clown". Ah well, c'est la vie!
Last edited by Islander2; 22nd Jan 2009 at 08:52.
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Check again
Check your books again my lad, you should perhaps check context.Yes they are my lad.
ps: I think you may have the wrong graph. It may have changed on the last 40 years, but I wouldn't think so!
pps: I have never seen a "minimum rate of turn" graph????
You clown!
ps: I think you may have the wrong graph. It may have changed on the last 40 years, but I wouldn't think so!
pps: I have never seen a "minimum rate of turn" graph????
You clown!
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Check your books again my lad
You clown!
Last edited by Islander2; 22nd Jan 2009 at 08:40.
Point of interest for a European jet trainer,SL,wt 8000lbs,maxpwr/wt ratio .47; max ROT @8g 300kts =28.5deg/sec,radius 320 mtrs,instantaneous at load limit.
Sustained ROT @2.8G, 160 kts,rate of turn18 deg/sec,radius 275 mtrs,level.Any subsequent reduction in speed will reduce G/bank angle/ROT TO 1/0/0, with subsequent increase in radius..Chart doesn`t give any benefit for flaps,but it will decrease radius slightly..
Sustained ROT @2.8G, 160 kts,rate of turn18 deg/sec,radius 275 mtrs,level.Any subsequent reduction in speed will reduce G/bank angle/ROT TO 1/0/0, with subsequent increase in radius..Chart doesn`t give any benefit for flaps,but it will decrease radius slightly..
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Flap
The use of full flap generally only applies to light trainers, as with most high performance machines, the extension of flap will lower the max g limit, generally by about 40%.. We used full flap for the manouvere in the P3.(Orion). The Canberra was clean for the manouvere.
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Simon 150 - you mentioned doing the maths. Some time ago I did just that for a "typical light aircraft", assuming a limiting g of 4.4g clean and 2.2g with flap down. The graphs illustrating the results were most illuminating for me. In particular, max rate (level turn of course) is indisputably achieved at full power clean. But if you want min radius, it doesn't make much difference whether flaps are up or down. I have found that fact useful for scenario based training.
If you like, I'll PM you the spreadsheet with graphs attached. (If I can attach files to a PM that is - if not, send me an email address.)
If you like, I'll PM you the spreadsheet with graphs attached. (If I can attach files to a PM that is - if not, send me an email address.)
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The use of full flap generally only applies to light trainers, as with most high performance machines, the extension of flap will lower the max g limit, generally by about 40%.
a) post #9 referred to a 32% reduction in max g limit with flap lowered in a Beech Bonanza; and
b) post #23 linked to the data for the Cessna 150/152 family, showing the Aerobat to have a 42% reduction in max g limit with flap lowered.
So we can reasonably conclude that the extension of flap in maximum performance manoeuvres isn't particularly good advice for either GA aeroplanes or high performance machines!
And, since you're so insistent that we check our books in order to come around to your "it is ever so elementary" yet incorrect assessment, here's a couple for you to go to bed with:
i) Aerodynamics for Naval Aviators by H.H.Hurt, which is the aerodynamics text for US Navy aviators, and which takes seven pages to explain the complexities of maximum performance tactical turning, in the process considering lift limits, strength limits and power limits and
ii) Flightwise (Volume 2 - Aircraft Stability & Control) by Chris Carpenter, who was Head of Aerodynamics at the Royal Air Force College Cranwell in the 1980s, which takes nine pages to deal with the same complexities.
Hardly 'elementary'!
If I could give you a steer (unlikely, I know, from one of 'you boys who haven't flown an aircraft that goes faster than 700kts'), I would point yet again to your incorrect paraphrasing of the relevant formulae. The fact is that turn radius is a function of V^2/tanAoB and turn rate is a function of tanAoB/V. It is mathematically impossible for V=minimum radius to be the same as V=max rate! This is covered more than adequately in the two texts quoted above but, should your preference be for a more academically-rigorous book, I would point you in the direction of Introduction to Flight by John D Anderson.
Last edited by Islander2; 25th Jan 2009 at 21:18.