BY ORDER OF THE SECRETARY OF THE AIR FORCE AIR FORCE ...

AFMAN 11-217V1 3 JANUARY 2005 207
may not take the obstacle height and distance from the SID and determine
a “new” climb gradient for the SID. To do so may expose you to other
obstacles that are not depicted. USAF aircraft must meet the published
climb gradient or 200 feet per nm, whichever is higher, with all engines
operating – not a new gradient that you have calculated.
9.8.4.1.1.3.2. Climb Gradient Table. Military SIDs provide information
about both obstacle and ATC climb gradients. Typically, all climb
gradient information is placed in a climb gradient table published on the
SID. An asterisk generally denotes a minimum climb gradient (*) and a
“dagger” (†) symbol generally denotes an ATC climb gradient. It is
important to understand how to properly use the information presented in
the climb gradient table.
9.8.4.1.1.3.3. Climb Rate vs. Climb Gradient. The unit of measurement
used actually describes climb rates in feet per minute (like VVI). Because
the table’s climb rate is based on feet per minute, it assumes a constant
groundspeed. During climbout, you rarely hold a constant groundspeed
(affected by TAS, winds, acceleration, pilot technique, etc.), so the climb
rates in feet per minute are actually not very useful. Instead of a “climb
rate,” what you really need to know is the required “climb gradient”
expressed in feet per nautical mile or percent gradient. The table provides
the information you need, but you need to know how to pick it out.
9.8.4.1.1.3.4. CAUTION: Flying the VVI values represented in the climb
gradient table does not guarantee obstacle clearance. In order to properly
ensure obstacle clearance, you must compare your aircraft’s climb
performance to the required climb gradient (not the climb rate).
9.8.4.1.1.4. Determining the Climb Gradient in Feet Per Nautical Mile. By
applying the “60-1 Rule” (described in AFMAN 11-217, Volume 3,
Supplemental Information.), the number that appears in the "60 knot” block of
the climb gradient table is the required gradient in feet per nautical mile. If
there is no “60” block, just divide the “120” block by two or divide the “180”
block by three, etc.
9.8.4.1.1.4.1. Conversions. With your climb gradient in feet per nautical
mile, you can now convert to other units of measurement in order to assess
your aircraft’s required performance. Here are some of the common
conversions:
9.8.4.1.1.4.2. Feet Per Nautical Mile to Percent Gradient. To convert feet
per nautical mile to percent gradient, divide the gradient in feet per
nautical mile by 60 to convert to percent gradient. For example, if your
required climb gradient is 300 ft/NM, divide by 60 to convert to percent
gradient. In this case, 300 divided by sixty equals five, so your required
climb gradient is 5%. Just reverse the process to convert percent gradient
to feet per nautical mile.
9.8.4.1.1.4.3. Feet Per Minute to Percent Gradient. If you are using a