60TO1 RULE (FORMULAS)
 What
is the 60to1 rule and why should you use ıt ?

 It's
a technique for establishing predictable pitch
change and lead point for intercepting courses
orarcs. Listed below are three good reasons for
using this rule.
 It
allows the pilot to compute the pitch change
necessary when establishing an altitute during
the control and performance concept (establish
pitch ,trim,and crosscheck) of altitute
instrument flying .
 It
reduces the pilot workload and increases
efficiency by requiring fewer changes and less
guesswork.

 When
Do You Use The 60to1 Rule ?

 Here
are examples of the types of pilot problems that
can be readily solved by applying the 60to1
rules.
 You're
in level flight and flying 400 ktas airspeed and
you want to establish a rate of climb or descent
of 1000 feet per minute (feet/minute). What pitch
change will give you the desired rate of climb or
descent.?
 You're
80 DME at DME ,at FL 310 to inbound to YAA VOR
,and you want to cross YAA vor at 5000 feet. When
should you start your descent and What pitch
change should you make to do that ?
 You're
climbing at 3000 feet/min at 250 kıas. Wpitch
change will be necessary to level your aircraft
at FL 350

 How
to Work With the 60to1 Rule

 The
60to1 rule gives us a mathematical equation to
help you figure out all these questions ,but
ıt's almost impossible to turn these calculation
and fly at the same time.You need to use these
formulas before you fly. Find out what your turn
radius is at cruise airspeed up high and at
appoach airspeed down lower , find out what a 1°
pitch chance will do to your VVI ,and remember
those number. Take your appoaches out prior to
flıght and write in your lead radial and VVI's
right on the IAP .

 Mathematical
Data Supporting the 60to1 Rule

 Let's
relate this to a VOR station .We know that the
formula for the circumference of circle = 2p r.
Therefore ,the circumference of a 60 NM circle
around our VOR is
 C=
( 2 ) ( 3.14 ) ( 60 )
 C=
376.99 NM for a 60 radius circle.
 Because
there are 360° in a circle ,we can determine the
length of a 1° arc
 376.99/360
= 1.0472 or approximately 1 NM per degree at 60
NM
 Because
1 NM = 6,076 feet or approximately 6000 feet ,we
can therefore say
 1°
= 6000 feet at 60 NM This relationship is true
not only in the horizontal plane ,but also in the
vertical plane .If wwere make a 1° dive than we
would have descended 6000 feet
 (
1 NM ) after traveling 60 NM .Though the magic of
algebra ,we can break this down to 100 feet per
NM for a 1 °dive or picth change.

 VVI
Versus Pitch change .

 We
know now how to calculate the altitute gained or
lost for each degree of pitch change over a
gıven distance . Throw in a time factor using
True airspeed ( TAS ) expressed in NM and we can
relate this pitch change to a change in VVI .
 Let's
convert to speed to NM / MIN ,since the 60to1
rule is based on True air speed (TAS ) experssed
in NM / MIN.
 NM
/ MİN can be obtained easily from either TAS or
the Indicated mach Number
 (
IMN ) as follows.
 ***
Directly from TAS :
 TAS/60
=NM/MIN
 EXAMPLE
: 420 TAS/60 =7 NM/MIN
 ***
From IMN :
 IMN
x 10 = NM / MIN
 Example
: 0.7 mach x 10 = 7 NM / MIN
 If
you don't have a TAS indicator or an IMN , TAS
can be compute from indicated airspeed ( IAS ) .
TAS increases over IAS at the rate of 2 percent
per 1000 feet altitute imcreas . so use the
equation :
 TAS
= IAS + ( 2 %per 1000 feet )x (IAS)
 Example
: FL 200 ; 270 KIAS
 TAS
= 270 + ( 2 %. x 20 ) ( 270 ) = 270 + (0.40 ) x
(270) = 378 KTAS
 Another
easy but less accurate formula ( best between
10.000 feet and FL 350)
 TAS
=FL/2 + IAS
 example
: FL 200 , 270 KTAS
 TAS
=200/2 + 270 = 100+ 270 = 370 KTAS

 NOTE : These
basic expression of TAS and NM / MIN will be used
often in future discussions.

 If
one degree equals 100 feet per NM ,then our VVI
can be calculated by :
 VVI
= NM / MIN x100 feet
 Example
: For 0.6 mach and a 1° pitch change :
 IMN
x 10 = NM / MIN
 0.6
x 10 = 6 NM / MIN
 VVI
for 1° pitch change = NM / MIN x 100 = 6 x 100 =
600 feet / NM
 Example
2 : for 420 KTAS and 2 ° pitch change :
 TAS/60
= NM/MIN
 420
KTAS/60 =7NM/MIN
 VVI
for 1 ° pitch change = NM / MIN x 100
 VVI
for 2 ° pitch change = 2 x NM / MIN x 100 = 1400
feet /mın

 Descent
Gradient s for Approach or Enroute Descent

 Let's
look at a real world you on airway VA 16 north
east bound to Istanbul and
 ATC
direct you to cross the YAA VOR at 12.000 feet .
According the first calculation you are 25 NM
from YAA VOR , and cruısing at FL 270 with mach
0.75 What descent gradient is requıred and what
VVI should you expect ?
 First
you need to know what your descent gradient has
to be. You can find the descent gradient by
applying the 60to1 relatıonship of 100 feet
per NM. To lose
 15.000
feet in 25 NM you will need a descent gradient of
600 feet/nm or about a 6° pitch change. Here is
the math.
 descent
gradient = 100 of feet / Distance in NM = 150/25
= 6
 Now
you what descent gradient is required, you can
compute what your VVI should be if you make a
pitch change of 6° while flying at .75 mach . In
thıs case your VVI will be 4500 feet /min to
begin with. If you hold 0.75 mach all the way
down ,the Vvı will work.
 IMN
x 10 = NM / MIN
 0.75
x 10 = 7.5 NM / MIN

 VVI
= angle ( NM / MIN * 100 ) = 6 ( 7.5 * 100 ) =
4500 feet / min

 If
you maintain an IAS throughout the descent .as
many of us do, then your TAS will decrease as you
get lower altitute. VVI required to maintain the
6° descent gradient will slowly decrease as you
descend. IF you hold 4500 feet / min all the way
down to 12.000 feet ,yıu will get down early.
The most important part of the quation ( which
remains constant no matter what speed you are
flying ) is the descent gradient. You must
descend at 600 feet / min ( or about 6°) in
order to make to altitute restriction at the YAA
VOR.

 Climb
Gradient

 As
you might suspect, computing a climb gradient is
really no different than the enroute descent
calculations, but let's run an example to see how
it's done. Let's say you are getting ready to fly
a Standard Instrument Departure (SID). You look
at the plate and see that you will need a climb
gradient of 350 FEET/NM to 10,000 feet. So, we
need to climb out at 3.5° angle. Our best climb
air speed is 200 KIAS. The airport is 3,000 Feet
MSL.
 ****
First we need to
calculate our TAS. In this case, 200 KIAS at
3,000 feet MSL works out to 212 KTAS and 200 KIAS
at 10,000 feet MSL is 240 KTAS. Dividing each of
these by 60 will give you your speed in NM/MIN at
3,000 and 10,000 feet respectively.
 At
3000 feet MSL
 TAS
= IAS + ( 2% per 1000 feet ) = 200 + ( 3 * .02 *
200 ) =200 + 12 = 212 KTAS
 NM
/ MIN = TAS / 60 = 212 / 60 = 3,5 NM / MIN
 At
10.000 feet MSL
 TAS
= IAS + ( 2% per 1000 feet ) = 200 + ( 10 * .02 *
200 ) =200 + 40 = 240 KTAS
 NM
/ MIN = TAS / 60 = 240 / 60 = 4 NM / MIN
 **** Next
calculate your VVI. Immediately after takeoff ,
your VVI will be 1,225 feet / min
 As
you climb (and your TAS increases ) , your VVI
will slowly increases to approximately
 1.400
feet /min . There are couple of tecniques to deal
with the change in TAS. One tecnique
 is
to use the higher VVI ( 1,400 feet / min )
throughout the climb. Another way to figure a
target VVI is to use an average true airspeed (
for example , using your TAS at 6.500 feet
MSL)better yet use groundspeed instead of TAS 
using groundspeed accounts for the wind.
 At
3.000 feet MSL
 VVI
= Angle ( NM / MİN * 100 ) = 3.5 ( 3.5 * 100 ) =
1.225 feet / min
 At
10.000 feet MSL
 VVI
= Angle ( NM / MİN * 100 ) = 3.5 ( 4.0 * 100 ) =
1.400 feet / min
 Next
:
 We
are going to discuss some formulas about
calculating a Visual Descent point (VDP)
Precision Glide path , Turn radius ,Lead point
(SURF IN SKY magazine August 2000)

