AN ILS PROCEDURE TURN APPROACH TO MARTHA'S VINEYARD
  By Mel Beckman [75226,2257] uploaded to CompuServe FSFORUM

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   Here's a step-by-step for shooting the ILS approach at Martha's
Vineyard, coming from anywhere.  In the real world, a controller
probably would give you "vectors", or headings to fly, to get you lined
up for the approach. However, the IFR system is designed so that
approaches can be flown with no voice controllers contact (your comm
radio could fail, after all), and in such situations, a common way to
fly the approach uses a process called the "course reversal" or
"procedure turn."  Here's how to do it f or Marth's Vineyard:

  1. Dial the Martha's Vineyard VOR frequency (108.7) into the NAV2
radio, and the ILS frequency (108.8) into NAV1.

  2. Fly directly to the VOR from whatever your departure point. The
procedure for flying directly to a VOR is easy: turn the "V" knob on
NAV2 until you get a "TO" flag on the VOR's OBI and the needle is
centered.  Then fly whatever heading you read on the top of the OBI.  If
the needle drifts to the right, turn a few degrees to the right until
the needle is centered again.  Likewise if the needle drifts to the
left.  This is called "tracking" a VOR radial.

  3. As you get close to the VOR ground station, the needle will get
more sensitive, and you'll need to make smaller corrections.  You'll
want to start a gradual descent to 2000 feet as you get near the
station. When you're very close to the ground station, the needle will
swing all the way to one side.  Just hold your heading and wait until
the "TO" flag changes to FROM.  At that point you've just passed over
the station and you're ready to start the procedure turn manuever.  You
should now be at 2000 feet for the Martha's Vineyard approach.

  4. The checklist for a procedure turn is "The Six Ts" -- Turn, Twist,
Track, Time, Throttle, Talk:

    T1: Turn to the outbound heading, in this case 056 degrees.

    T2: Twist the OBI to the outbound heading (set the NAV2 OBI to 056
degrees).

    T3: Track the outbound radial.  Do this just like you did flying the
radial in to the station, making left/right corrections as indicated by
the needle.  You'll initially have to correct by at least 15 degrees to
get the needle centered, but then you can turn back onto the outbound
heading.

    T4: Time.  Start your stopwatch.

    T5: Throttle back to approach speed.  In the 172, you'll bring the
engine back to about 1700 RPM.  When the airplane slows to less than 100
knots, put down 10 degrees of flaps.  You'll eventually reach a speed of
about 90 knots.

    T6: Talk to the approach controller and tell him you've begun the
approach procedure.

   5. Continue tracking the outbound radial for one minute, then turn 45
degrees TO THE RIGHT, to a heading of 101 degrees, and hold that heading
for one minute.  Ignore the VOR needle, it's going to become uncentered
until you've completely turned around.  You make all turns at "standard
rate" -- only steep enough to tilt the turn coordinator to it's little
mark next to the L or R.  

   6. During this minute of waiting, set up your ILS receiver: make sure
the 108.8 frequency is dialed in to NAV1, and set the OBI on NAV1 to 236
degrees (the inbound course).  This last bit doesn't effect the radio at
all (it's ignored when ILS frequencies -- those ending in 2, 4, 6, or 8
-- are dialed in) -- you're just setting it as a memory aid for
yourself.  During this phase a pilot also reviews various other
checklists, but you can forgo that for now.

   7. After one minute has elapsed, make a 180 degree turn TO THE LEFT,
to a heading of 281 degrees.  This turn should take exactly one minute
at standard rate.

   8. Fly the 281 degree heading until the NAV1 vertical needle (called
the localizer needle) begins to move toward the center.  Gradually turn
to the inbound heading (236 degrees, which you've set into the NAV1 OBI
as a reminder) so that the localizer needle is centered about when you
get on that heading.  This takes a bit of practice.

   9. When the outer marker light starts blinking and beeping (the "O"
light), you're on final approach and ready to descend.  Just put the
landing gear down, and ease the yoke forward a bit, and you'll start a
descent of about 500 feet per minute almost automatically (putting the
gear down aerodynamically nudges you into a descent).  At the outer
marker you'll also notice that the horizontal ILS needle, called the
glideslope, is centered, so the two needles form a cross.  Your
objective from this point on is to keep those needles centered.

  10. You'll be descending to the Minimum Descent Altitude, or MDA,
which at Martha's is probably 200 feet (Microsoft didn't print it in
their approach chart).  During the descent, make very tiny left/right
corrections to keep the localizer needle centered.  Adjust your power to
keep the glideslope needle centered: if the needle starts drifting up,
add a little power; if it drifts down, remove a little power.  Don't try
to "fly" the airplane up and down to "catch" the needle -- you'll just
start uncontrolla ble airspeed oscillations.  You want to maintain an
airspeed of 90 knots, and you do that by bringing the nose up if you get
to fast, or putting it down if you get too slow.  This (controlling
altituted with power and airspeed with the yoke) seems kind of
backwards, I know, but it is how you keep everything smooth and stable.

  11. When you reach the MDA altitude, if you have the airport in sight,
you can land.  Otherwise the Federal Aviation Regulations require that
you fly the "missed approach" procedure.  But for your purposes, you'll
have the most fun actually landing!

   Eleven steps.  It's not so bad.  You'll have to make three or four
runs before you get everything precise enough to make it all work out.
But don't give up -- it's an incredibly satisfying achievement to
perform a successful instrument approach.  And if you can do it in MS
Flight Simulator, you can do it in a real aircraft!

  -mel