Busted IFR Checkride

Bob Moore wrote in
. 8:

Andrew Sarangan wrote

If you have a crosswind, you can't maintain a racetrack shape if you
want to do standard rate turns. That is why we double the wind
correction on the outbound. The goal is to make standard rate turns
on both ends of the holding pattern, not to keep the outbound
parallel to the inbound.

Gee...thanks for the explanation Andrew, and to think that for all of
these years, for a one minute pattern, I've been teaching that one
should *triple* the drift on the outbound leg. We taught it that way
at PanAm long before the FAA changed the AIM as follows.

From AIM 5-3-7

(c) Compensate for wind effect primarily by drift correction on the
inbound and outbound legs. When outbound, triple the inbound drift
correction to avoid major turning adjustments; e.g., if correcting
left by 8 degrees when inbound, correct right by 24 degrees when
outbound.



Bob Moore


OK, now I'm confused. If you triple the correction, wouldn't the inbound
turn be less than standard rate? What am I missing here?

Andrew Sarangan wrote

OK, now I'm confused. If you triple the correction, wouldn't the inbound
turn be less than standard rate? What am I missing here?

Well...ignoring the turns for the moment, using the same drift
correction for the outbound leg as used on the inbound leg (with
an opposite sign of course) would result in parallel tracks. This
is one times the inbound drift (1x). Now, for a one minute pattern,
there are two standard rate turns, each requiring one minute to
complete. The distance blown off during each of the turns is the
same as one would be blown off during one of the one minute strait
legs, requiring an ammount of drift correction on the outbound leg
for each of the turns equal to the ammount used for the one minute
strait leg. All adds up to be three times (3x) the inbound drift
correction.

Yes, even the old AC 61-27C, Instrument Flying Handbook had it wrong.

Bob Moore

Bob Moore wrote

Well...Now after spell checking.."amount and straight"

Bob Moore

In article ,
Bob Moore wrote:

Andrew Sarangan wrote

OK, now I'm confused. If you triple the correction, wouldn't the inbound
turn be less than standard rate? What am I missing here?

Well...ignoring the turns for the moment, using the same drift
correction for the outbound leg as used on the inbound leg (with
an opposite sign of course) would result in parallel tracks. This
is one times the inbound drift (1x). Now, for a one minute pattern,
there are two standard rate turns, each requiring one minute to
complete. The distance blown off during each of the turns is the
same as one would be blown off during one of the one minute strait
legs, requiring an ammount of drift correction on the outbound leg
for each of the turns equal to the ammount used for the one minute
strait leg. All adds up to be three times (3x) the inbound drift
correction.

Yes, even the old AC 61-27C, Instrument Flying Handbook had it wrong.

Bob Moore

The only problem with that is it assumes that tripling the wind
correction angle triples the drift correction. For small angles, that's
a reasonable approximation (it's saying that sin(x) = x), but it falls
apart for big ones.

In a 90 kt spam can, a direct 25 kt crosswind requires a 15 degree WCA
inbound, which would mean a 45 degree WCA angle outbound. You don't
often see a 25 kt crosswind on the runway, but it's not uncommon at 3000
AGL where you might be holding. A jet holding at 180 kts will need half
the WCA you do at 90 kts.

So, yes, triple is better than double, but even better in a slow
airplane is asking the controller for longer legs! 2 minute legs will
let you fly double the inbound WCA on the outbound leg, and 3 minute
legs will make it even easier. Even easier than that is to ask for 5 or
even 10 DME legs, assuming you're so equipped (gotta love GPS).