B: Re: OT // C90 crash in NC; NTSB Prelim published
BobsV35B at aol.com
BobsV35B at aol.com
Sun Feb 17 11:47:14 EST 2008
Good Morning John,
After reviewing the preliminary report, I am even more convinced that the
better plan for that approach and the reported conditions would have been to
execute the approach with the mind set that it was going to be a circling
I probably would have done a classic Dive and Drive, so that I would be in
position for a straight in if the opportunity presented itself, but my plans
and organization would be on setting up for the circle.
Either the dive and drive or the electronically generated glide path would
have been OK as long as the level off was started soon enough such that the
circling MDA was not violated.
I think it would have been foolish to be flying that approach in a King Air
at 120 knots. The King Airs that I flew tended to like about 105 knots. I am
not sure if the newer ones like to be faster, but 120 knots is getting too
close to C category for my comfort. Category B allows circling with one mile
visibility and that seemed to be a sure bet that day.
The problem might have been the lower cloud deck at three hundred feet. That
is even more reason to stay level at the circling MDA and look things over.
If it didn't look good on the first trip around the field, it would be
perfectly acceptable to make another circle as long as adequate visual references to
the airport were available and the circling limits (Including the lateral
area limitations) were not violated.
The circling MDA is only twenty feet higher than the straight in. It seems
to me that it well worth giving up that twenty feet to gain the extra time and
safety at the MDA while circling to find a safe approach path to the runway.
It is my idea of a classic situation where the circling approach should have
been the plan and the straight in only considered if conditions were much
better than expected.
The safety of flying level at the MDA while one thinks things over is
something that most pilots do not fully appreciate.
I need time to think! Don't most people find that extra time useful?
628 West 86th Street
Downers Grove, IL 60516
Brookeridge Air Park LL22
In a message dated 2/17/2008 9:54:05 A.M. Central Standard Time,
johncollins at carolina.rr.com writes:
The GPS RWY approach at Mount Airy is interesting
The rate of descent from JODRI to the threshold is just over 390 ft/NM.
According to the preliminary NTSB report, the weather was 2 1/2 miles, rain,
broken at 300, overcast at 600. On the approach, the last radar return on
final showed the aircraft at 2000 ft, 1 NM from the MAP. Assuming he crossed
the FAF JODRI at 3200, it would mean that he averaged 300 ft/NM to the 1 NM
point, so it is unlikely he got to minimums and stabilized prior to the MAP
and would not likely have been in a position to land, even he was able to
see the runway, without circling.
If he had a WAAS GPS and followed the vertical guidance, the GS would have
gotten him to the MDA about 1.2 NM from the threshold, but he would have had
little time to spot the runway and make a straight in landing. If he was
flying the approach at 120 Kts, he would have had to maintain just over 780
ft/min descent rate.
I think a dive and drive at 1000 ft per minute would have worked better,
with a level off starting 100 ft before the MDA, that might have given him
about 2 NM to find the runway. I personally don't like descending that
fast, but for this type of approach, one must be aware of the higher than
normal descent angle to the runway and either slow down or descend more
rapidly if they expect to be able to land straight in.
One other point, if this approach was flown with a WAAS GPS coupled to the
autopilot for vertical, the vertical GS would not appear until just past
EFOLE, only 1 NM from the FAF, or only about 30 seconds at 120 Kts. This
might not provide sufficient time for setting up the autopilot in order to
capture the GS. If I were planning on using the WAAS advisory GS, I would
activate vectors to final at EDLIF and intercept the GS at 4000 ft.
John D. Collins
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