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rkaplan
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Posted: Tue Jan 24th, 2006 02:53 am |
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When flying a full instrument approach including a procedure turn, most approaches require you to stay within 10 miles of the final approach fix for the procedure turn. A small minority reduce this distance, typically to 5 miles.
The Garmin 430/530 do not distinguish between 5nm vs. 10nm procedure turn areas. Instead the GPS charts all procedure turns to begin at about 2nm from the FAF and end at about 4nm from the FAF. This often leads to a rushed approach with too little time to lose altitude.
It is perfectly OK to continue your procedure turn further out. The distance from the FAF is displayed on the Garmin 430/530. You will find that if you begin your procedure turn at about 5nm and finish it about 7-8nm then you will have lots more time to lose altitude, establish a crosswind correction heading, run your GUMPS check, and all-around feel more prepared for the approach. This can easily make the difference between landing vs. a missed approach, especially with a non-precision approach to a relatively short runway in actual instrument weather.
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Richard Kaplan, CFII
rkaplan@flyimc.com
http://www.flyimc.com
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Hi_thin_scattered
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Posted: Tue Jan 31st, 2006 02:22 pm |
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It's worth mentioning that 5-mile procedure turns are limited to IAPs that are authorized for Approach Category A airplanes only.
A related issue is the holding pattern icon in a 500/530 for the hold-in-lieu course reversal or the missed approach hold. Although the icon correctly displays the alignment of the holding pattern, it does not correctly display the actual size of the holding pattern.
Some pilots are of the mistaken impression (including some Garmin-authorized CFI-I's) that you must remain within the Garmin oval when holding. That is all it is; i.e., Garmin's icon. It bears no relationship to the authorized holding pattern airspace, which varies by altitude and authorized holding speed.
So, the pilot should use timing or charted distance to determine when to turn inbound.
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rkaplan
Administrator
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Posted: Tue Jan 31st, 2006 03:13 pm |
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Hi_thin_scattered wrote: Some pilots are of the mistaken impression (including some Garmin-authorized CFI-I's) that you must remain within the Garmin oval when holding. That is all it is; i.e., Garmin's icon. It bears no relationship to the authorized holding pattern airspace, which varies by altitude and authorized holding speed.
That is indeed a helpful point. It can get confusing though because Garmin's icon does change for a timed hold vs. a hold with a charted distance and the size of a timed hold icon does change with groundspeed.
____________________
Richard Kaplan, CFII
rkaplan@flyimc.com
http://www.flyimc.com
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Hi_thin_scattered
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Posted: Tue Jan 31st, 2006 04:52 pm |
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The high-end LNAV platforms all have the design engineers' ideas of what a holding pattern should be. If in fact, they observe the time or distance limitations (those high end units will track the pattern with positive course guidance) there is almost certainly no-harm, no foul, because the aircraft will very likely remain within the FAA protected pattern (FAA Order 7130.3A).
I've played with it at jet speeds (230 knots, say at 12,000') and the Garmin icon is far too small.
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rkaplan
Administrator
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Posted: Tue Jan 31st, 2006 05:24 pm |
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Hi_thin_scattered wrote: I've played with it at jet speeds (230 knots, say at 12,000') and the Garmin icon is far too small.
That may well be the best explanation of all.
For piston airplanes I do not think there is any harm from following the holding pattern icon. Doing it any other way adds more workload, only questionably adds to accuracy, and does not add anything to safety I can see.
The procedure turn depiction though is another story -- I think if you begin the procedure turn as early as Garmin plots it then often a pilot will be too rushed to get down vertically.
____________________
Richard Kaplan, CFII
rkaplan@flyimc.com
http://www.flyimc.com
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Hi_thin_scattered
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Posted: Tue Jan 31st, 2006 06:16 pm |
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rkaplan wrote: Hi_thin_scattered wrote: I've played with it at jet speeds (230 knots, say at 12,000') and the Garmin icon is far too small.
That may well be the best explanation of all.
For piston airplanes I do not think there is any harm from following the holding pattern icon. Doing it any other way adds more workload, only questionably adds to accuracy, and does not add anything to safety I can see.
I have no quarrel with making it an optional technique. But, a friend of mine was critizied by a Garmin-trained CFI-I for timing instead of turning to remain within the icon oval.
The procedure turn depiction though is another story -- I think if you begin the procedure turn as early as Garmin plots it then often a pilot will be too rushed to get down vertically.
Not to mention crowding a stepdown fix within the procedure turn area, where one is charted.
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