Matronics Email Lists :: View topic - Angle of Bank vs Stall Speed

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Angle of Bank vs Stall Speed

Matronics Email Lists Forum Index -> Kolb-List

View previous topic :: View next topic

Author Message

kuffel(at)cyberport.net
Guest

Posted: Wed Apr 28, 2010 12:55 pm Post subject: Angle of Bank vs Stall Speed

Sent this two hours ago.  So far it hasn't appeared on the list.   My paranoid side says there must be censorship of my ideas somewhere.

  

 -----------------------------------------------------------------

  

 Sigh.  My conscience won't let me ignore this.



pj, boyd,  Dana:



Dang it, ignore what I say, fly the maneuver and see for  yourself.  Go to 

altitude, reduce power if you wish, enter a 30 degree  bank and hold 

absolutely constant airspeed for 180 degrees and then roll  level.  Repeat at 

5 miles/knots slower.  Repeat again until you  are as close to Vso as your 

ability to hold a constant airspeed  allows.  You will not stall.



For more details as to why this is true  review my messages in the thread 

linked by Jason:



[url=]http://forums.matronics.com/viewtopic.php?t=38477&highlight=descending+turn+stall[/url]



Now:



<<  If the turns are less than 30 deg and the g load less than  1.5,,     you 

may be ok.   if the turn  is  60 or more deg bank and g load 2 or above >>



<< In a  coordinated turn, the stall speed increases as a function of the 

bank angle  >>



These out of context statements are exactly the misconception  which kills 

pilots every year.  I know, it almost killed me during my  primary training. 

I know, base to final turn accidents are a major source of  aircraft 

fatalities every year.  They are true *if you maintain  (approximately) a 

constant vertical component for your lift vector.*   The only way to do this 

is to increase your total lift, in other words  maintain constant altitude, 

in other words increase your load  factor.



But don't believe me, go out and fly the maneuver yourself at  altitude.



Look at the AIM diagram we have all had drummed into our  subconscious.  As 

the angle of bank increases, the total lift increases  to keep the vertical 

component the same.  Now with your hands block out  all but the first 

airplane.  Rotate the entire  manual.  This  is the case of a constant 

airspeed in a turn.  Some of the lift is now  used to make the turn and less 

lift is available to oppose gravity and you  will *start* to descend faster. 

But since the total lift is unchanged so is  the stall speed.  In other 

words, stall speed increases with load  factor, not angle of bank.



But don't believe me, go out and fly the  maneuver yourself at altitude.



<<  Take a 45 degree bank, for  example.  In a normal, coordinated, level 

turn, you pull 1.41G.   If you put your aircraft into a 45 degree bank and 

hold 1G, the vertical  component of lift will be only 0.707g; thus you'll 

have a downward  acceleration of 0.3g, or 9.4 ft/s/s, or 566 fpm/s.  This 

means that  after one second, your rate of descent will have increased by 566 

fpm.   After four seconds, you're descending at 2264 fpm, which is a pretty 

steep  dive, and you WILL pull more than one g pulling out of it. >>



The  math here is wrong.  After one second you are descending at 9 feet/sec,  

2 seconds you are now at 19 ft/sec, 3 seconds = 28 ft/sec, 4 sec = 38 ft/sec  

or so.  In addition it ignores the vertical component of drag which is  

significant.



But don't believe me, go out and fly the maneuver  yourself at altitude.



The above statements as well as the "death spiral"  of Boyd's CFI are the 

result of misunderstanding the context of what I and  others are trying to 

fix.  The problem is the turn from base to  final.  Most pilots initiate a 

bank of about 30 degrees.  Half way  through the turn they see they are 

overshooting the runway.  What they  should do is increase their angle of 

bank to 45 degrees or even briefly 60  degrees at constant airspeed to finish 

the turn.  Instead, because  "increased angle of bank means increased stall 

speed" (in a different  context) has been fixated in their minds they try to 

fudge the situation  with rudder and/or tightening up (pulling on the stick) 

instead.  This  brings them to experience the other four fundamentals of 

flight: stall,  spin, crash and burn.  What we must fixate instead is 

"constant  airspeed = constant load factor = constant stall speed".



But don't  believe me, go out and fly the maneuver yourself at altitude.



Now just  because I have an evil nature let me mention one more context 

besides turns  at low altitude for landing.  This should start another thread 

in the  Seafoam mode.  The concept of constant airspeed control is also  

paramount in mountain search and rescue reversing turns and box canyon  

escapes.  What I teach is no change in power, smoothly increase your  climb 

rate and bank until you reach your desired bank and airspeed, say Vs1  + 10. 

Maintain this bank and airspeed until you have reversed  direction.  You will 

now be in a decent but at a higher altitude,  smoothly pullout and you are 

now going in the opposite direction at roughly  your starting altitude and 

airspeed.  This method allows the pilot to  concentrate on airspeed control 

and situational awareness without the  distraction of power control.  The 

reduced airspeed during the turn  also creates a very small radius of turn.



But don't believe me, go out  and fly the maneuver yourself at altitude.



Let me finish with an  irrelevant appeal to authority.  Every, and I mean 

every, CFI with whom  I've had the above discussion and then taken flying has 

adopted my emphasis  on constant airspeed control for maneuvering close to 

the ground.



But  don't believe me, go out and fly the maneuver yourself at altitude.



Good  luck and have fun,



Tom Kuffel, CFI

EAA Flight Advisor  



    [quote][b]

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Thu Apr 29, 2010 12:21 am Post subject: Angle of Bank vs Stall Speed

At 04:39 PM 4/28/2010, The Kuffels wrote:



 

  	  Quote: 	
		  For more details as to why this is true review my messages in the thread 

 linked by Jason:



 [url=??]http://forums.matronics.com/viewtopic.php?t=38477&highlight=descending+turn+stall[/url] 	


 I did.  I stand by what I said there, as well as in this thread.



  	  Quote: 	
		  << In a coordinated turn, the stall speed increases as a function of the 

 bank angle >> 	


 Correct.



  	  Quote: 	
		  true *if you maintain (approximately) a 

 constant vertical component for your lift vector.*  The only way to do this 

 is to increase your total lift, in other words maintain constant altitude, 

 in other words increase your load factor. 	


 Correct.  Note that if you don't maintain "a constant vertical vertical component for your lift vector", you will accelerate downward (or upward, as the case may be, though that's not what we're talking about).



  	  Quote: 	
		  ...This is the case of a constant 

 airspeed in a turn.  Some of the lift is now used to make the turn and less 

 lift is available to oppose gravity and you will *start* to descend faster. 

 But since the total lift is unchanged so is the stall speed.  In other 

 words, stall speed increases with load factor, not angle of bank. 	


 Correct.  "You will *start* to descend faster."  And if you maintain 1G in a banked turn, you will *continue* to accelerate downward.



  	  Quote: 	
		  <<  Take a 45 degree bank, for example.  In a normal, coordinated, level 

 turn, you pull 1.41G.  If you put your aircraft into a 45 degree bank and 

 hold 1G, the vertical component of lift will be only 0.707g; thus you'll 

 have a downward acceleration of 0.3g, or 9.4 ft/s/s, or 566 fpm/s.  This 

 means that after one second, your rate of descent will have increased by 566 

 fpm.  After four seconds, you're descending at 2264 fpm, which is a pretty 

 steep dive, and you WILL pull more than one g pulling out of it. >>



 The math here is wrong.  After one second you are descending at 9 feet/sec, 

 2 seconds you are now at 19 ft/sec, 3 seconds = 28 ft/sec, 4 sec = 38 ft/sec 

 or so.  In addition it ignores the vertical component of drag which is 

 significant. 	


 What math do you say is wrong?  Sounds like you're agreeing with me, as I said after one second you're descending at 9.4 ft/s, etc.  You rounded the numbers off but they're approximately the same as mine (after four seconds, 38 ft/s is 2280 fpm).



 The vertical component of drag is zero at the start, and then yes, it becomes significant.  However, it doesn't affect the math, because regardless of the drag, you _have_ to accelerate downward as described above or you won't maintain 1G.



  	  Quote: 	
		  ...Half way through the turn they see they are 

 overshooting the runway.  What they should do is increase their angle of 

 bank to 45 degrees or even briefly 60 degrees at constant airspeed to finish 

 the turn.  Instead, because "increased angle of bank means increased stall 

 speed" (in a different context) has been fixated in their minds they try to 

 fudge the situation with rudder and/or tightening up (pulling on the stick) 

 instead... 	


 Both are the wrong thing to do.  Increase the bank angle in coordinated turn and you risk an acelerated stall;  add rudder for a skidding turn and you risk stalling the inside wing.



  	  Quote: 	
		  What we must fixate instead is 

 "constant airspeed = constant load factor = constant stall speed". 	


 Constant load factor = constant stall speed, yes.  Constant airspeed has nothing to do with it.



 Don't get me wrong; i understand (or I think I understand) the technique you're advocating:  steepen the turn but don't pull back, instead letting the airplane fall off into a descent.  But saying that you're OK if you maintain a constant airspeed is fixating on one aspect of the problem, and can get a pilot into trouble.  Fly at 1.3Vs and enter a 60 degree coordinated turn and you either get an accelerated stall, or end up in a dive which also requires more than 1G to pull out.



 "But don't believe me," do the math yourself.



 -Dana



 P.S.  A conventional pitot tube airspeed indicator is only accurate when the pitot tube is aligned with the airflow.  At high AOA, the airspeed indicator will read less than the actual airspeed, i.e. you're actually going faster than you think you are... which may explain why you're not stalling even when the indicated airspeed is less than the stall speed corresponding to the load factor corresponding to the bank angle.  



 "But don't believe me," do the math yourself.

 

 --

  Life is a sexually transmitted disease.    [quote][b]

slyck(at)frontiernet.net
Guest

Posted: Thu Apr 29, 2010 2:25 am Post subject: Angle of Bank vs Stall Speed

Good stuff Tom.  Can't say I've studiously done exactly what you describe but sounds 100%.In my younger and bolder days, on occasion I used a method to bleed altitude that I would not recommend:

not S turning, not slipping, not the Kolb dive...

I would, on a high final, deliberately stall the old crate, or pretty close to it.  Sure would lose a lot of altitude

and the wings would stay nice and level.  Then I'd toss a touch of throttle at it and squeak it on nice and short.

Obviously this would be solo.  Gusty conditions would be a no no, as would hedgerows or any extraneous

turbulizers.  Very exhilarating.  Last time I did it for funsies was on a near zero day in a field near where a neighbor

was operating a McCulloch J2 gyrocopter.   I siloed it a touch too aggressively and bent a few tubes

and cracked the windshield.  It needed a new one anyway.  Only landing I did that short after that was

with a power failure in a neighbor's champ on take off with nothing good ahead.  (wires and houses)

Silo descent to plowed ground aside the runway.  Zero roll out.  No damage. Old neighbor never asked me to fly his

areoplane again though.

I wouldn't try it in my Kolb.  Too old.   Back might break.

BB





On 28, Apr 2010, at 4:39 PM, The Kuffels wrote:

 	  Quote: 	
		  Sent this two hours ago.  So far it hasn't appeared on the list.  My paranoid side says there must be censorship of my ideas somewhere.

 

-----------------------------------------------------------------

 

Sigh.  My conscience won't let me ignore this.



pj, boyd, Dana:



Dang it, ignore what I say, fly the maneuver and see for yourself.  Go to 

altitude, reduce power if you wish, enter a 30 degree bank and hold 

absolutely constant airspeed for 180 degrees and then roll level.  Repeat at 

5 miles/knots slower.  Repeat again until you are as close to Vso as your 

ability to hold a constant airspeed allows.  You will not stall.



For more details as to why this is true review my messages in the thread 

linked by Jason:



[url=]http://forums.matronics.com/viewtopic.php?t=38477&highlight=descending+turn+stall[/url]



Now:



<< If the turns are less than 30 deg and the g load less than 1.5,,     you 

may be ok.   if the turn is  60 or more deg bank and g load 2 or above >>



<< In a coordinated turn, the stall speed increases as a function of the 

bank angle >>



These out of context statements are exactly the misconception which kills 

pilots every year.  I know, it almost killed me during my primary training. 

I know, base to final turn accidents are a major source of aircraft 

fatalities every year.  They are true *if you maintain (approximately) a 

constant vertical component for your lift vector.*  The only way to do this 

is to increase your total lift, in other words maintain constant altitude, 

in other words increase your load factor.



But don't believe me, go out and fly the maneuver yourself at altitude.



Look at the AIM diagram we have all had drummed into our subconscious.  As 

the angle of bank increases, the total lift increases to keep the vertical 

component the same.  Now with your hands block out all but the first 

airplane.  Rotate the entire  manual.  This is the case of a constant 

airspeed in a turn.  Some of the lift is now used to make the turn and less 

lift is available to oppose gravity and you will *start* to descend faster. 

But since the total lift is unchanged so is the stall speed.  In other 

words, stall speed increases with load factor, not angle of bank.



But don't believe me, go out and fly the maneuver yourself at altitude.



<<  Take a 45 degree bank, for example.  In a normal, coordinated, level 

turn, you pull 1.41G.  If you put your aircraft into a 45 degree bank and 

hold 1G, the vertical component of lift will be only 0.707g; thus you'll 

have a downward acceleration of 0.3g, or 9.4 ft/s/s, or 566 fpm/s.  This 

means that after one second, your rate of descent will have increased by 566 

fpm.  After four seconds, you're descending at 2264 fpm, which is a pretty 

steep dive, and you WILL pull more than one g pulling out of it. >>



The math here is wrong.  After one second you are descending at 9 feet/sec, 

2 seconds you are now at 19 ft/sec, 3 seconds = 28 ft/sec, 4 sec = 38 ft/sec 

or so.  In addition it ignores the vertical component of drag which is 

significant.



But don't believe me, go out and fly the maneuver yourself at altitude.



The above statements as well as the "death spiral" of Boyd's CFI are the 

result of misunderstanding the context of what I and others are trying to 

fix.  The problem is the turn from base to final.  Most pilots initiate a 

bank of about 30 degrees.  Half way through the turn they see they are 

overshooting the runway.  What they should do is increase their angle of 

bank to 45 degrees or even briefly 60 degrees at constant airspeed to finish 

the turn.  Instead, because "increased angle of bank means increased stall 

speed" (in a different context) has been fixated in their minds they try to 

fudge the situation with rudder and/or tightening up (pulling on the stick) 

instead.  This brings them to experience the other four fundamentals of 

flight: stall, spin, crash and burn.  What we must fixate instead is 

"constant airspeed = constant load factor = constant stall speed".



But don't believe me, go out and fly the maneuver yourself at altitude.



Now just because I have an evil nature let me mention one more context 

besides turns at low altitude for landing.  This should start another thread 

in the Seafoam mode.  The concept of constant airspeed control is also 

paramount in mountain search and rescue reversing turns and box canyon 

escapes.  What I teach is no change in power, smoothly increase your climb 

rate and bank until you reach your desired bank and airspeed, say Vs1 + 10. 

Maintain this bank and airspeed until you have reversed direction.  You will 

now be in a decent but at a higher altitude, smoothly pullout and you are 

now going in the opposite direction at roughly your starting altitude and 

airspeed.  This method allows the pilot to concentrate on airspeed control 

and situational awareness without the distraction of power control.  The 

reduced airspeed during the turn also creates a very small radius of turn.



But don't believe me, go out and fly the maneuver yourself at altitude.



Let me finish with an irrelevant appeal to authority.  Every, and I mean 

every, CFI with whom I've had the above discussion and then taken flying has 

adopted my emphasis on constant airspeed control for maneuvering close to 

the ground.



But don't believe me, go out and fly the maneuver yourself at altitude.



Good luck and have fun,



Tom Kuffel, CFI

EAA Flight Advisor 



 	  Quote: 	
		  



href="http://www.matronics.com/Navigator?Kolb-List">http://www.matronics.com/Navigator?Kolb-List

href="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/contribution

jbhart(at)onlyinternet.ne
Guest

Posted: Thu Apr 29, 2010 2:50 am Post subject: Angle of Bank vs Stall Speed

From: "The Kuffels" <kuffel(at)cyberport.net>

Date: Wed, 28 Apr 2010 14:39:28 -0600

 	  Quote: 	

Sigh.  My conscience won't let me ignore this.

........

 	  Quote: 	

Tom,

Sounds like you are advocating flying a powered aircraft much like flying a 

glider or sailplane.  Sailplane instructors emphasize coordinated turns and 

constant speed and never mention constant altitude.  When I started flying 

sailplanes, one of the things I had to unlearn was the desire to maintain 

altitude through out a turn, and learn to fly at constant speed.  You are 

correct in that I never fell into a spin while thermalling while flying at 

constant speed no matter how steep the bank or the speed.  

With an engine as the energy source, one can easily recover any altitude lost after a constant speed turn.  I believe it is a less stressful way to fly on both the pilot and the machine, since one does not have make power changes during a turn to maintain constant altitude.

Thanks.

Jack B. Hart FF004

Winchester, IN

kuffel(at)cyberport.net
Guest

Posted: Thu Apr 29, 2010 9:49 am Post subject: Angle of Bank vs Stall Speed

Sigh.  My conscience won't let me ignore this.



pj, boyd, Dana:



Dang it, ignore what I say, fly the maneuver and see for yourself.  Go to 

altitude, reduce power if you wish, enter a 30 degree bank and hold 

absolutely constant airspeed for 180 degrees and then roll level.  Repeat at 

5 miles/knots slower.  Repeat again until you are as close to Vso as your 

ability to hold a constant airspeed allows.  You will not stall.



For more details as to why this is true review my messages in the thread 

linked by Jason:



http://forums.matronics.com/viewtopic.php?t=38477&highlight=descending+turn+stall



Now:



<< If the turns are less than 30 deg and the g load less than 1.5,,     you 

may be ok.   if the turn is  60 or more deg bank and g load 2 or above >>



<< In a coordinated turn, the stall speed increases as a function of the 

bank angle >>



These out of context statements are exactly the misconception which kills 

pilots every year.  I know, it almost killed me during my primary training. 

I know, base to final turn accidents are a major source of aircraft 

fatalities every year.  They are true *if you maintain (approximately) a 

constant vertical component for your lift vector.*  The only way to do this 

is to increase your total lift, in other words maintain constant altitude, 

in other words increase your load factor.



But don't believe me, go out and fly the maneuver yourself at altitude.



Look at the AIM diagram we have all had drummed into our subconscious.  As 

the angle of bank increases, the total lift increases to keep the vertical 

component the same.  Now with your hands block out all but the first 

airplane.  Rotate the entire  manual.  This is the case of a constant 

airspeed in a turn.  Some of the lift is now used to make the turn and less 

lift is available to oppose gravity and you will *start* to descend faster. 

But since the total lift is unchanged so is the stall speed.  In other 

words, stall speed increases with load factor, not angle of bank.



But don't believe me, go out and fly the maneuver yourself at altitude.



<<  Take a 45 degree bank, for example.  In a normal, coordinated, level 

turn, you pull 1.41G.  If you put your aircraft into a 45 degree bank and 

hold 1G, the vertical component of lift will be only 0.707g; thus you'll 

have a downward acceleration of 0.3g, or 9.4 ft/s/s, or 566 fpm/s.  This 

means that after one second, your rate of descent will have increased by 566 

fpm.  After four seconds, you're descending at 2264 fpm, which is a pretty 

steep dive, and you WILL pull more than one g pulling out of it. >>



The math here is wrong.  After one second you are descending at 9 feet/sec, 

2 seconds you are now at 19 ft/sec, 3 seconds = 28 ft/sec, 4 sec = 38 ft/sec 

or so.  In addition it ignores the vertical component of drag which is 

significant.



But don't believe me, go out and fly the maneuver yourself at altitude.



The above statements as well as the "death spiral" of Boyd's CFI are the 

result of misunderstanding the context of what I and others are trying to 

fix.  The problem is the turn from base to final.  Most pilots initiate a 

bank of about 30 degrees.  Half way through the turn they see they are 

overshooting the runway.  What they should do is increase their angle of 

bank to 45 degrees or even briefly 60 degrees at constant airspeed to finish 

the turn.  Instead, because "increased angle of bank means increased stall 

speed" (in a different context) has been fixated in their minds they try to 

fudge the situation with rudder and/or tightening up (pulling on the stick) 

instead.  This brings them to experience the other four fundamentals of 

flight: stall, spin, crash and burn.  What we must fixate instead is 

"constant airspeed = constant load factor = constant stall speed".



But don't believe me, go out and fly the maneuver yourself at altitude.



Now just because I have an evil nature let me mention one more context 

besides turns at low altitude for landing.  This should start another thread 

in the Seafoam mode.  The concept of constant airspeed control is also 

paramount in mountain search and rescue reversing turns and box canyon 

escapes.  What I teach is no change in power, smoothly increase your climb 

rate and bank until you reach your desired bank and airspeed, say Vs1 + 10. 

Maintain this bank and airspeed until you have reversed direction.  You will 

now be in a decent but at a higher altitude, smoothly pullout and you are 

now going in the opposite direction at roughly your starting altitude and 

airspeed.  This method allows the pilot to concentrate on airspeed control 

and situational awareness without the distraction of power control.  The 

reduced airspeed during the turn also creates a very small radius of turn.



But don't believe me, go out and fly the maneuver yourself at altitude.



Let me finish with an irrelevant appeal to authority.  Every, and I mean 

every, CFI with whom I've had the above discussion and then taken flying has 

adopted my emphasis on constant airspeed control for maneuvering close to 

the ground.



But don't believe me, go out and fly the maneuver yourself at altitude.



Good luck and have fun,



Tom Kuffel, CFI

EAA Flight Advisor

jbhart(at)onlyinternet.ne
Guest

Posted: Thu Apr 29, 2010 1:56 pm Post subject: Angle of Bank vs Stall Speed

Kolbers,



Viewed Richard Pike's recommended video yesterday evening.  For those of you 

with out a high speed Internet connection, I recorded the data, and here it 

is. C 172 flying at a constant 65 ias making full 360 degree coordinated 

turns.



Bank     Lost     Decent

Angle  Altitude    Rate

(deg)   (feet)    (fpm)

 15      879       600

 30      450       650

 45      390       900

 60      350      1500



The video displayed the instrument panel.  The rate of decent did not 

increase during the turn.  The stall horn came on during the 45 degree bank 

but there was no buffeting.  There was some buffeting during the 60 degree 

bank, but no stall horn.



Also the performed some 180 emergency turn arounds by setting their 

altimeter to zero at 100 feet agl.  They flew the airport runway at 100 ft 

agl and initiated a climb at over the runway and climbed to 600 feet agl and 

pulled the throttle.  They could not get back to the airport using a 15 

degree bank.



Good video!



Jack B. Hart FF004

Winchester, IN

kuffel(at)cyberport.net
Guest

Posted: Thu Apr 29, 2010 8:30 pm Post subject: Angle of Bank vs Stall Speed

Dana said:

  

 <<    << In  a coordinated turn, the stall speed increases as a function of the 

bank  angle >>

 

Correct.  >>

  

 Not correct.  This is only true in the special circumstance of  maintaining altitude, ie increasing total lift, aka load factor.  The  emphasis on this without equal emphasis on the special circumstance is *why*  pilots in the stress of landing still stall by trying to increase their rate of  turn with rudder alone (uncoordinated flight) and/or pulling back (increasing  load factor).  The certain antidote to this error is constant airspeed  during landing maneuvers.

  

 Once again, go up in the air and test my statements.  I don't dispute  holding a constant airspeed in a turn will increase your rate of decent.   But we are not talking about turns which last for minutes or even more than a  few seconds.   I strongly dispute the notion that any technique other  than constant airspeed and coordinated flight independent of (less than  aerobatic) bank angle is the proper way to avoid problems during the turn  from base to final, particularly in situations of no or steady power or  practicing same, which should be almost always.

  

 Boyd said:

  

 <<  I had given an example of a steep bank turn to emphasize the  situation.

And my definition of 1 g plus   is 1.01g and  above.   I am probably taking

things to  literally.  >>

  

 Not really.  I wasn't worried about 1 g +/-  10% or so.  The problem is the emphasis on bank angle materially increasing  stall speed (I call double a material increase) without equal emphasis that the  real cause is via increased load factor, and that this doesn't apply in a  descending turn has resulted in pilots killing themselves year after year in the  turn to final.  And the absolutely, positively sure way to not increase  load factor in this turn is constant airspeed.

 

<<   Any time you turn a plane there is  going to be more energy required.  And

you can trade the energy needed  to turn by unloading the wings momentarily

and remain at a literal 1g  .   But as soon as the plane returns to a steady

state and you  remain in a turn,  greater than 1g will be required. >>

  

 This is not true.  The lift vector on the  wings has no idea what the gravity vector is doing.  Go up and set a bank  angle of 20 degrees and constant airspeed.  You will find yourself in a  steady state turn of 1 g.  What will also happen is your rate of  decent will increase.  But this decent is not in a vacuum.  The  increase in your decent is actually slowed by the air such that several full  circles are easily possible..  I've demonstrated this many times for  people, even disbelieving fellow CFIs. (Are CFIs really people?)  Now  when doing the same thing at 60 degree bank things get real exciting very  soon, even at only 1/4 circle, which may be Dana's point.  But my point is  this fact doesn't apply to the problem, its cause or the proper solution to  avoid it.

  

 Tom Kuffel

    [quote][b]

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Fri Apr 30, 2010 3:37 am Post subject: Angle of Bank vs Stall Speed

This always turns (pardon me) into such a lively discussion about angles, constant speeds and gee loads and then somebody finally says something like,



"What will also happen is your rate of decent will increase"

 



and we get to the true crux of the matter. Something had to give among all these constants and it seems to be that the ground will come up at a faster rate to smite thee. How about that. 

 I read somewhere that there was a sign in the Curtiss Flying School office that said, "Flying is simple, to go up pull back on the stick. To come down, pull back farther". That was around 100 years ago and seems to be, amazingly enough, still true today.

 



Rick

 

On Thu, Apr 29, 2010 at 11:25 PM, The Kuffels <kuffel(at)cyberport.net (kuffel(at)cyberport.net)> wrote:

 [quote]       Dana said:

  

 <<    << In  a coordinated turn, the stall speed increases as a function of the 

bank  angle >>

 

Correct.  >>

  

 Not correct.  This is only true in the special circumstance of  maintaining altitude, ie increasing total lift, aka load factor.  The  emphasis on this without equal emphasis on the special circumstance is *why*  pilots in the stress of landing still stall by trying to increase their rate of  turn with rudder alone (uncoordinated flight) and/or pulling back (increasing  load factor).  The certain antidote to this error is constant airspeed  during landing maneuvers.

  

 Once again, go up in the air and test my statements.  I don't dispute  holding a constant airspeed in a turn will increase your rate of decent.   But we are not talking about turns which last for minutes or even more than a  few seconds.   I strongly dispute the notion that any technique other  than constant airspeed and coordinated flight independent of (less than  aerobatic) bank angle is the proper way to avoid problems during the turn  from base to final, particularly in situations of no or steady power or  practicing same, which should be almost always.

  

 Boyd said:

  

 <<  I had given an example of a steep bank turn to emphasize the  situation.

And my definition of 1 g plus   is 1.01g and  above.   I am probably taking

things to  literally.  >>

  

 Not really.  I wasn't worried about 1 g +/-  10% or so.  The problem is the emphasis on bank angle materially increasing  stall speed (I call double a material increase) without equal emphasis that the  real cause is via increased load factor, and that this doesn't apply in a  descending turn has resulted in pilots killing themselves year after year in the  turn to final.  And the absolutely, positively sure way to not increase  load factor in this turn is constant airspeed.

 

<<   Any time you turn a plane there is  going to be more energy required.  And

you can trade the energy needed  to turn by unloading the wings momentarily

and remain at a literal 1g  .   But as soon as the plane returns to a steady

state and you  remain in a turn,  greater than 1g will be required. >>

  

 This is not true.  The lift vector on the  wings has no idea what the gravity vector is doing.  Go up and set a bank  angle of 20 degrees and constant airspeed.  You will find yourself in a  steady state turn of 1 g.  What will also happen is your rate of  decent will increase.  But this decent is not in a vacuum.  The  increase in your decent is actually slowed by the air such that several full  circles are easily possible..  I've demonstrated this many times for  people, even disbelieving fellow CFIs. (Are CFIs really people?)  Now  when doing the same thing at 60 degree bank things get real exciting very  soon, even at only 1/4 circle, which may be Dana's point.  But my point is  this fact doesn't apply to the problem, its cause or the proper solution to  avoid it.

  

 Tom Kuffel

     	  Quote: 	
		  



get="_blank">http://www.matronics.com/Navigator?Kolb-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	


[b]

_________________
The smallest miracle right in front of you is enough to make you happy....

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Fri Apr 30, 2010 4:07 am Post subject: Angle of Bank vs Stall Speed

At 12:25 AM 4/30/2010, The Kuffels wrote:

  	  Quote: 	
		  Dana said:

  

 <<    << In a coordinated turn, the stall speed increases as a function of the 

 bank angle >>



 Correct.  >>

  

 Not correct.  This is only true in the special circumstance of maintaining altitude, ie increasing total lift, aka load factor. 	


 I see your point, but... it's correct if you're maintaining altitude, but it's _also_ correct for a constant rate of descent, i.e. no vertical acceleration... which isn't happening in your 1g turn.



  	  Quote: 	
		    The emphasis on this without equal emphasis on the special circumstance is *why* pilots in the stress of landing still stall by trying to increase their rate of turn with rudder alone (uncoordinated flight) and/or pulling back (increasing load factor).  The certain antidote to this error is constant airspeed during landing maneuvers....  I don't dispute holding a constant airspeed in a turn will increase your rate of decent.  But we are not talking about turns which last for minutes or even more than a few seconds.   I strongly dispute the notion that any technique other than constant airspeed and coordinated flight independent of (less than aerobatic) bank angle is the proper way to avoid problems during the turn from base to final, particularly in situations of no or steady power or practicing same, which should be almost always. 	


 OK.  I'm not saying your technique isn't valid; I'm just speaking as an aeronautical engineer precisely defining the situation.  In aero engineering most flight conditions, other than stability and control calculations, are analyzed steady state, which your 1G increasing rate of descent gliding turn is not.  Letting the airplane slide (not slip; by "slide" I mean keeping the ball centered) out of a turn by letting the nose drop is indeed a good way to manage a gliding turn.  Reducing the load factor also maintains energy since you're not holding high AOA which causes drag and slows you down even more.



 I simply take exception to the notion that all will be well if you maintain constant airspeed.  You say that avoidance of steep bank angle kills pilots who, trying to avoid an accelerated stall, instead spin out of a skid, and that's true, but it's only one side of the problem.  On the other side, believing that all will be OK if you only maintain a constant airspeed can also get you into trouble... if a pilot does a 60 degree bank at 1.3Vs and _doesn't_ back off on the stick and let the nose drop, he _will_ experience an accelerated stall, which can be just as bad as the stall out of a skid.



 So:  Stall speed is a function of load factor, not (necessarily) bank angle.  Load factor IS a function of bank angle, but only in coordinated, level or constant vertical speed, flight.



 -Dana



 

 --

  Puritanism: the haunting fear that someone, somewhere, may be happy.    [quote][b]

by0ung(at)brigham.net
Guest

Posted: Fri Apr 30, 2010 7:47 am Post subject: Angle of Bank vs Stall Speed

This is not true.  The lift vector on the wings has no idea what the gravity vector is doing.  Go up and set a bank angle of 20 degrees and constant airspeed.  You will find yourself in a steady state turn of 1 g.  What will also happen is your rate of decent will increase.  But this decent is not in a vacuum.  The increase in your decent is actually slowed by the air such that several full circles are easily possible..  I've demonstrated this many times for people, even disbelieving fellow CFIs. (Are CFIs really people?)  Now when doing the same thing at 60 degree bank things get real exciting very soon, even at only 1/4 circle, which may be Dana's point.  But my point is this fact doesn't apply to the problem, its cause or the proper solution to avoid it.  

   

Tom Kuffel   	  Quote: 	
		   	
  

Tom  you said “Now when doing the same thing at 60 degree bank things get real exciting very soon, even at only 1/4 circle,”   ok would you like to explain in further detail just how ex citing and in what way?  

   

Boyd   

       [quote][b]

kuffel(at)cyberport.net
Guest

Posted: Fri Apr 30, 2010 3:53 pm Post subject: Angle of Bank vs Stall Speed

Hi Boyd, 

<<  Tom   you said “Now when doing the same thing  at 60 degree bank things get real exciting very soon, even at only 1/4  circle,”    ok would you like to explain in further  detail just how ex citing and in what way?  >>

 Sure.  In any 1 g turn the amount of lift used  to make the turn is then not available to resist the force of earth's  gravity.  This means you will increase your rate of descent.  In  shallow bank turns the effect is small and not very apparent even after a full  circle.  At 60 degrees however the rate of descent increases to a dramatic  amount by at least a half circle, sometimes sooner depending on aircraft  aerodynamics and your personal definition of exciting.

  

 But this is not the situation which kills  pilots.  Here we are talking about the descending quarter circle turn to  final.  Half way through the turn the pilot sees he is overshooting the  runway path.  What he should do is concentrate on maintaining the same  airspeed, briefly increase his angle of bank, even up to 60 degrees if needed,  and smoothly roll out.  Doing this maintains a 1 g turn, ok a 1.1 g turn on  rollout if one wants to quibble, which does not increase your stall speed for  all practical purposes.  You are at the increased bank angle for at most  1/8 of a circle.

  

 But because "increased bank angle means  increased stall speed" is buried in the back, dark recesses of our training too  many pilots try to save the situation by fudging the turn, either with rudder  (uncoordinated flight) or by pulling back (increased load factor).

  

 My solution to this problem is the following basis  for landing approaches.  Opposite the approach end of the runway reduce  power and set configuration (flaps and trim) to your desired approach  speed.  Maintain this speed *constantly* until at least you are established  on final.  Turns should normally be 20 - 30 degrees of bank.  On turn  to final the bank can be increased as described above for the time needed  to complete the turn.  This is guaranteed to not produce a stall or  breathtaking rates of descent.

  

 Within this framework there are lots of variables  such as adjusting power or adjusting airspeed along the back side of the power  curve after being established on final.  But from the start of the approach  descent until at least established on final the sure and certain way to  avoid an unintended stall is constant airspeed control.

  

 Again, go out to altitude and try some  example quarter circle turns for yourself.  Even at speeds  unreasonably close to Vso you won't get even a nibble of a stall at angles of  bank below aerobatic flight.  Or come visit us in Whitefish and I'll  demonstrate in an airplane easier to stall than a Kolb.

  

 Best,

  

 Tom

  

    [quote][b]

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Sat May 01, 2010 3:14 am Post subject: Re: Angle of Bank vs Stall Speed

...But because "increased bank angle means increased stall speed" is buried in the back, dark recesses of our training too many pilots try to save the situation by fudging the turn, either with rudder (uncoordinated flight) or by pulling back (increased load factor)....



Tom is correct here and I believe that the primary reason for the last part, "pulling back (increased load factor)" is the more common and due largely to the pilot's noticing the increased descent rate when banking steeper and his natural response to halt the higher descent rate. If the approach trajectory is higher then the increased descent rate would not be so "scary" and thus less likely to elicit the "pulling back" response resulting in increased load factor and higher stall speed. 



This brings me to one of the reasons that over the years I've adopted the practice of always (whenever possible) making a high approach and kill altitude only after I'm on stable short final. With my Slingshot this is very easy to accomplish. When I was flying an Allegro with rather high aspect ratio wings, it was a lot more difficult to get down in a short distance, but achievable though to a lessor degree.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

by0ung(at)brigham.net
Guest

Posted: Sat May 01, 2010 7:53 am Post subject: Angle of Bank vs Stall Speed

 	  Quote: 	
		  >>>>>>>>>>>>>>>>>   

Tom  
	


   

But this is not the situation which kills pilots.  Here we are talking about the descending quarter circle turn to final.  Half way through the turn the pilot sees he is overshooting the runway path.  What he should do is concentrate on maintaining the same airspeed, briefly increase his angle of bank, even up to 60 degrees if needed, and smoothly roll out.  Doing this maintains a 1 g turn, ok a 1.1 g turn on rollout if one wants to quibble, which does not increase your stall speed for all practical purposes.  You are at the increased bank angle for at most 1/8 of a circle.  

   

I guess there is still one other option  not yet discussed.……    ,go ahead and   overshoot the centerline, stay at your current angle of bank  and speed,   make the turn to final a 100 to 105 deg turn and angle back to the centerline,  then straighten up when on center.  At the base to final turn you should be 400 to 500 ft agl and plenty of time and altitude for another few deg of turn.  

During ppl training I did exactly what you recommend,  and that is when my cfi deemed it necessary to do an extended lesson on accelerated stalls.    

   

Or come visit us in Whitefish and I'll demonstrate in an airplane easier to stall than a Kolb.  

   

That is the best offer I have heard all day.  Hope you are not surprised when I take you up on that.   Is my waypoint in the gps still good?  

   

Boyd  

    

       [quote][b]

Display posts from previous:

	Matronics Email Lists Forum Index -> Kolb-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum