Canyon Turns

"Marc Lattoni" wrote

Today we did canyon turns, not at 30, not at 45 but more than 45
degrees. Sort of standing the airplane on its wingtip as we turn.

Yep! We fought this battle for about two weeks last year.
There were two groups, one was the slow down and use flaps
with a shallow angle of bank and the other group (me) quoting
the aerodynamic textbook solution of flying at maneuver speed
and using about 75 degrees angle-of-bank.

Quoting from "Aerodynamics For Naval Aviators":

"The aerodynamic limit of turn radius requires that increased
velocity be utilized to produce increasing load factors and
greater angles of bank"

"The maneuver speed is the minimum speed necessary to develop
aerodynamically the limit load factor and it produces the
minimum turn radius within aerodynamic and structural limits."

Bob Moore

On Thu, 11 Mar 2004 14:47:43 GMT, Robert Moore
wrote in Message-Id:
:

There were two groups, one was the slow down and use flaps
with a shallow angle of bank and the other group (me) quoting
the aerodynamic textbook solution of flying at maneuver speed
and using about 75 degrees angle-of-bank.

On 4/21/2000 John T. Lowry, PhD (author of: Performance of Light
Aircraft ISBN 1-56347-330-5) said:

Message-ID:
Actually the best turnaround bank angle (least altitude lost per
degree turned) is slightly above 45 degrees. See Performance of
Light Aircraft p. 295. Rogers neglected the inclination of the
flight path angle. For GA aircraft the extra angle beyond 45
degrees is, admittedly, negligible. For a Cessna 172, flaps up, I
get 45.4 degrees for the best turnaround bank angle. Now for that
flamed-out jet fighter ...

And on 1 Nov 1999 07:11:02 -0700:
Message-ID:
Best turnaround bank angle phi (least altitude loss per angle
turned through) for a gliding airplane is given by:

cos(phi) = (sqrt(2)/2)*sqrt(1-k^2)

where k = CD0/CLmax + CLmax/(pi*e*A)

where CD0 is the parasite drag coefficient, CLmax is the maximum
lift coefficient for the airplane's flaps configuration, e is the
airplane efficiency factor, and A is the wing aspect ratio. I know
most ng readers hate those darned formulas, but that's the way the
world works.

For GA propeller-driven airplanes, k is a small number (0.116 for
a Cessna 172, flaps up) and so the best turnaround bank angle is
very closely the 45 degrees cited by Rogers and, much earlier, by
Langewiesche (Stick and Rudder, p. 358). For the above Cessna, for
instance, it's 45.4 degrees. For a flamed-out jet fighter,
however, things are considerably different.

The formulas above, along with formulas for the banked stall
speed, for banked gliding flight path angle, and for the minimum
altitude loss in a 180-degree turn, can all be found in my recent
book Performance of Light Aircraft, pp. 294-296. The following
seven pages then treat the return-to-airport maneuver, from start
of the takeoff roll to contact with the runway or terrain, in
excruciating detail. Including wind effects, the typical
four-second hesitation when the engine stops, etc.

See also:

Message-ID:

Larry Dighera wrote

Message-ID:
Actually the best turnaround bank angle (least altitude lost per
degree turned) is slightly above 45 degrees.

Note that all of Lowery's discussions deal with minimizing altitude
loss during a "loss of power return to the field". This is not the
same as minimizing turn radius in a canyon where altitude loss may
not be a factor and where power is still available to maintain air-
speed during the high-g turn.

Once again, I did not post post anything about a "return to the field"
but simply quoted a highly respected aerodynamics text with regard to
minimizing turn radius.

Bob Moore

"Robert Moore" wrote in message
. 8...
Larry Dighera wrote

Message-ID:
Actually the best turnaround bank angle (least altitude lost per
degree turned) is slightly above 45 degrees.

Note that all of Lowery's discussions deal with minimizing altitude
loss during a "loss of power return to the field". This is not the
same as minimizing turn radius in a canyon where altitude loss may
not be a factor and where power is still available to maintain air-
speed during the high-g turn.

Once again, I did not post post anything about a "return to the field"
but simply quoted a highly respected aerodynamics text with regard to
minimizing turn radius.

Bob Moore

Hi Bob;
There's a difference between a fighter turning at Vc (corner velocity) and a
Canyon Turn. Corner provides both maximum turn rate and minimum turn radius
ONLY if maximum available radial g is applied! Below corner the fighter is
aerodynamically limited at the Cl line, and above corner limited by the max
available load factor out to the limit LF.
A Canyon turn isn't a constant altitude turn against a maximum g like a
fighter turning at it's Vc. It's in fact, partly an unloaded turn through
the vertical plane if airspeed has to be bled, or decreasing in altitude
through the steepest part of the bank angle used if initiated below cruise.
These are the subtle differences between these two turns.
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please replace
the z's with e's.
dhenriquesATzarthlinkDOTnzt

My apologies for coming in late, if this has already been mentioned. How
about a chandelle or wing-over?
http://www.skyjackmotorsports.com/IAC24/aresti.html

On Thu, 11 Mar 2004, Casey Wilson wrote:

My apologies for coming in late, if this has already been mentioned. How
about a chandelle or wing-over?
http://www.skyjackmotorsports.com/IAC24/aresti.html

Cool Aresti diagrams, but... if you're really, honestly in need of a
canyon turn, you're unlikely to have the excess airspeed you need to pull
a wingover or chandelle off, and if you're turning away from rising
terrain you might not have the altitude needed to trade for the needed
airspeed either...

Sparky Imeson's "Mountain Flying Bible" points this out at least three
times; he's in favour of the 60-degree bank, with flaps up to full as
appropriate, and power as needed. Personally, doing these turns in a 172N
starting at ~80 KIAS, I've gotten the plane turned around inside the long
dimension of a high school running track that was below us - that's about
200-250ft, give or take.

Let me just throw out a plug for Mr. Imeson's great book, while I'm at it.
I've only had my copy of the "Mountain Flying Bible" for six months, but
it's already got a well-thumbed look to it. I keep my copy on the kitchen
table, and review bits and pieces when I've got a spare five minutes, in
addition to more regular reviews. (http://www.mountainflying.com/ is his
website; Amazon has his books too.)

Brian - PP-ASEL/Night -

I second you on Sparky Imeson's book, also on the low probability that, in a
relatively low-powered airplane like the 172, that you'd have enough
airspeed or altitude for a fancy canyon turn when you need it.

There is a speed (dependent on gross weight, density altitude, and flaps
configuration) called the "Banked Absolute Ceiling Speed" Vbac and a
corresponding angle, "Banked Absolute Ceiling Angle" PHIbac. If you have
those written down for a few likely cases (e.g., max gross wt., 12000 ft,
flaps up; two or three other combinations) and keep your airspeed above Vbac
and your bank below PHIbac, you can turn level. Of course that may not be a
very short radius turn (that radius should be written down in your cheat
sheet also). So you have to stay out of canyons of width narrower than twice
that turn radius.

For how to calculate all this stuff, see the Maneuvering chapter of
Performance of Light Aircraft.

John

--
John T Lowry, PhD
Flight Physics
5217 Old Spicewood Springs Rd, #312
Austin, Texas 78731
(512) 231-9391

"Brian Burger" wrote in message
ia.tc.ca...
On Thu, 11 Mar 2004, Casey Wilson wrote:

My apologies for coming in late, if this has already been mentioned.
How
about a chandelle or wing-over?
http://www.skyjackmotorsports.com/IAC24/aresti.html

Cool Aresti diagrams, but... if you're really, honestly in need of a
canyon turn, you're unlikely to have the excess airspeed you need to pull
a wingover or chandelle off, and if you're turning away from rising
terrain you might not have the altitude needed to trade for the needed
airspeed either...

Sparky Imeson's "Mountain Flying Bible" points this out at least three
times; he's in favour of the 60-degree bank, with flaps up to full as
appropriate, and power as needed. Personally, doing these turns in a 172N
starting at ~80 KIAS, I've gotten the plane turned around inside the long
dimension of a high school running track that was below us - that's about
200-250ft, give or take.

Let me just throw out a plug for Mr. Imeson's great book, while I'm at it.
I've only had my copy of the "Mountain Flying Bible" for six months, but
it's already got a well-thumbed look to it. I keep my copy on the kitchen
table, and review bits and pieces when I've got a spare five minutes, in
addition to more regular reviews. (http://www.mountainflying.com/ is his
website; Amazon has his books too.)

Brian - PP-ASEL/Night -

"Brian Burger" wrote in message
ia.tc.ca...
On Thu, 11 Mar 2004, Casey Wilson wrote:

My apologies for coming in late, if this has already been mentioned.
How
about a chandelle or wing-over?
http://www.skyjackmotorsports.com/IAC24/aresti.html

Cool Aresti diagrams, but... if you're really, honestly in need of a
canyon turn, you're unlikely to have the excess airspeed you need to pull
a wingover or chandelle off, and if you're turning away from rising
terrain you might not have the altitude needed to trade for the needed
airspeed either...

Sparky Imeson's "Mountain Flying Bible" points this out at least three
times; he's in favour of the 60-degree bank, with flaps up to full as
appropriate, and power as needed. Personally, doing these turns in a 172N
starting at ~80 KIAS, I've gotten the plane turned around inside the long
dimension of a high school running track that was below us - that's about
200-250ft, give or take.

Thanks for the book tip, Brian. First, about the mountain flying. All
my experience has been in the Southern Sierra Madre, south of Mt. Whitney,
generally, although I've poked the nose over a few other ranges and
ridgelines. Maybe I'm too conservative, but I don't fly "up" a canyon blind.
I have to pretty much know what's up there before I let the ridgelines get
above the wings. Same thing going down-canyon -- I've got to know where it
opens up.
As far as the chandelle and wing-over, I was looking for opinions. Now
you piqued my interest in horsing the club's 172S into a 60-degree-bank turn
with full-flaps. I don't remember doing that with flaps. I've got a date
with my CFII next week. I wonder if the club has parachutes....
Just to pick a nit... the straight sections of the high school track
(presuming it is around a football field) is closer to 400 feet. Still a
darn tight turn, though.

Before you try this you should know that the load rating for your 172 with
the flaps down is 2.0G and the load factor in a level 60deg turn is 2.0g.

Mike
MU-2


"Casey Wilson" wrote in message
...

"Brian Burger" wrote in message
ia.tc.ca...
On Thu, 11 Mar 2004, Casey Wilson wrote:

My apologies for coming in late, if this has already been mentioned.
How
about a chandelle or wing-over?
http://www.skyjackmotorsports.com/IAC24/aresti.html

Cool Aresti diagrams, but... if you're really, honestly in need of a
canyon turn, you're unlikely to have the excess airspeed you need to
pull
a wingover or chandelle off, and if you're turning away from rising
terrain you might not have the altitude needed to trade for the needed
airspeed either...

Sparky Imeson's "Mountain Flying Bible" points this out at least three
times; he's in favour of the 60-degree bank, with flaps up to full as
appropriate, and power as needed. Personally, doing these turns in a
172N
starting at ~80 KIAS, I've gotten the plane turned around inside the
long
dimension of a high school running track that was below us - that's
about
200-250ft, give or take.

Thanks for the book tip, Brian. First, about the mountain flying. All
my experience has been in the Southern Sierra Madre, south of Mt. Whitney,
generally, although I've poked the nose over a few other ranges and
ridgelines. Maybe I'm too conservative, but I don't fly "up" a canyon
blind.
I have to pretty much know what's up there before I let the ridgelines get
above the wings. Same thing going down-canyon -- I've got to know where it
opens up.
As far as the chandelle and wing-over, I was looking for opinions.
Now
you piqued my interest in horsing the club's 172S into a 60-degree-bank
turn
with full-flaps. I don't remember doing that with flaps. I've got a date
with my CFII next week. I wonder if the club has parachutes....
Just to pick a nit... the straight sections of the high school track
(presuming it is around a football field) is closer to 400 feet. Still a
darn tight turn, though.

On Thu, 11 Mar 2004 14:47:43 GMT, Robert Moore
wrote:

"Marc Lattoni" wrote

Today we did canyon turns, not at 30, not at 45 but more than 45
degrees. Sort of standing the airplane on its wingtip as we turn.

Yep! We fought this battle for about two weeks last year.
There were two groups, one was the slow down and use flaps
with a shallow angle of bank and the other group (me) quoting
the aerodynamic textbook solution of flying at maneuver speed
and using about 75 degrees angle-of-bank.

Quoting from "Aerodynamics For Naval Aviators":

"The aerodynamic limit of turn radius requires that increased
velocity be utilized to produce increasing load factors and
greater angles of bank"

"The maneuver speed is the minimum speed necessary to develop
aerodynamically the limit load factor and it produces the
minimum turn radius within aerodynamic and structural limits."

Bob Moore

I have been taught two ways of making Canyon Turns.
In New Zealand I was shown a maximum performance turn. First make a
note of horizontal references then roll over 60deg, applying full
power and pull hard on elevator with both hands. The stall warning
goes off all time. It works well but I could not pull hard enough to
get stall warning to operate (C172).

The alternative way was shown to me in the USA.
Apparently called a Texas Turn, this involved reducing throttle to
idle then pitch up until in 'White Arc'. Immediately apply full flap
then full power then full rudder. Some pull on elevator but
controlling airspeed.

The former causes lots of 'G' whilst the latter has almost no 'G' and
you turn in about one wingspan, very impressive.

It has been suggested that the latter could induce a spin. I've not
had anybody confirm but it appears to be something like a 'Wingover'
maneuver but I'm not into aerobatics! Any comments?



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