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"Best forward speed" approaches



 
 
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  #1  
Old August 31st 03, 09:39 PM
Ben Jackson
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Default "Best forward speed" approaches

A few questions about fast (by spamcan standards) approaches in busy
terminal environments:

1) Is there any point in practicing any "best forward speed" approaches
besides the ILS?

2) How fast is fast enough? Obviously 120kts is better than 90kts
(maybe 1.5m less time after you turn onto the localizer), but does the
additional 20-30 seconds saved by going 130-140kts make a difference?

3) Do you fly these in a different flap/gear configuration or just use
more power?

4) Do you try this even when expecting to break out at minimums (with
less time to slow down)?

--
Ben Jackson

http://www.ben.com/
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  #2  
Old August 31st 03, 10:48 PM
Craig Prouse
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"Ben Jackson" wrote:

3) Do you fly these in a different flap/gear configuration or just use
more power?


Flying a C182, I use no-flap configurations for approaches at 120 knots or
greater. In fact, I cannot necessarily maintain 120 knots in level flight
with 10 flaps.

When I was working out approach power settings for my airplane, I was
looking for configurations where I could get anywhere from level flight to
800 FPM descent with power changes exclusively. I also learned that I
didn't like flying approaches with 20 flaps due to buffeting. This helped
me set some bounds on my approach airspeeds.

With 10 flaps and power virtually idle (10"), I get about 800 FPM down at
90 KIAS. So that's about as slow as I will fly an approach.

With flaps up and power up around 21" or 22", I can maintain level flight at
120 KIAS. So that's about as fast as I will fly an approach.

I have flown down a glideslope at 140 KIAS, but I wasn't able to achieve
that airspeed until I got going downhill, after ATC had been griping at me
for a couple minutes about how he was going to pull me off the approach if I
didn't stay ahead of the 757 behind me. I think all I really gained was
higher workload by trying to accelerate the extra 20 knots at glideslope
intercept. I don't think there's a lot to be gained by flying the descent
legs faster than you can fly the level legs. It just makes you like one of
those annoying people on mountain roads who go 90 MPH downhill but sputter
up the next grade at 50 MPH.

  #3  
Old August 31st 03, 10:58 PM
Brad Z
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Default


"Ben Jackson" wrote in message
news:N1t4b.316097$o%[email protected]
A few questions about fast (by spamcan standards) approaches in busy
terminal environments:

1) Is there any point in practicing any "best forward speed" approaches
besides the ILS?


Requests for best forward speed seem to come at approaches at
less-than-major airports on some degree of frequency. So I suppose its
possible that you may find yourself flying into a satellite airport with a
VOR approach with two charter flights behind you.


2) How fast is fast enough? Obviously 120kts is better than 90kts
(maybe 1.5m less time after you turn onto the localizer), but does the
additional 20-30 seconds saved by going 130-140kts make a difference?


It does if it prevents the aircraft behind you going 140 from catching up on
you. In reality, I don't think controllers expect much more than 120kts
best forward speed from the spamcan crew. 140kts is nice, 70 is not.



3) Do you fly these in a different flap/gear configuration or just use
more power?


Depends on the plane, the runway, and wind conditions. More often than not,
I fly precision approaches with no flaps, or maybe 10degrees. For a best
forward speed approach, I use the same configuration with a couple more
inches (or 100s of RPM) of power. Power back to idle and a good slip at DH
is usually enough to slow it down for landing. I try not to change the flap
settings past the FAF.


4) Do you try this even when expecting to break out at minimums (with
less time to slow down)?


If its 200 & 1/2, and people are flying misses ahead of me, I'd probably
elect to stack the odds in my favor. If I felt that a 120kt approach would
be less stable and more likely to result in a missed, I would exercise my
PIC authority and fly at the speed I was most comfortable to fly the
approach.



--
Ben Jackson

http://www.ben.com/



  #4  
Old September 1st 03, 12:17 AM
Roy Smith
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Default

(Ben Jackson) wrote:
1) Is there any point in practicing any "best forward speed" approaches
besides the ILS?


It doesn't hurt, but as a practical matter, the only time you'll get
"best speed" requests is at a busy airport with lots of jet traffic, and
in that case, it's almost certain that they're flying an ILS.

2) How fast is fast enough? Obviously 120kts is better than 90kts
(maybe 1.5m less time after you turn onto the localizer), but does the
additional 20-30 seconds saved by going 130-140kts make a difference?


In a typical spam can, 120 kts sounds plenty fast to me. I remember one
day, the controller asked for "best speed" and I decided to have some
fun (we were in visual conditions) and flew the ILS as fast as I could
get the thing going, which was probably about 150 KIAS. Turned out I
was following a Citation, and was gaining on him. The controller had to
tell me to slow it down again.

3) Do you fly these in a different flap/gear configuration or just use
more power?


In most light planes, anything that's likely to be fast enough for the
controller to appreciate will probably be above the white arc, so flaps
up. Some people like to fly ILS's that way anyway in spam cans. I'd
probably keep the gear down, but that's a judgement call.

4) Do you try this even when expecting to break out at minimums (with
less time to slow down)?


Not me. Try it some day in VFR conditions. Fly the glide slope (or
VASI) down to 200 AGL at 120 KIAS with the flaps up, then try to land
and see how much runway you use up.
  #5  
Old September 1st 03, 12:30 AM
Paul Tomblin
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In a previous article, Roy Smith said:
4) Do you try this even when expecting to break out at minimums (with
less time to slow down)?


Not me. Try it some day in VFR conditions. Fly the glide slope (or
VASI) down to 200 AGL at 120 KIAS with the flaps up, then try to land
and see how much runway you use up.


The airports where you're likely to get "keep your speed up" are, as you
said, also ones that are likely to have ILSes. They're also likely the
ones that have nice long runways. 8000 foot runways are plenty of room
for me to slow down an Archer from 130 knots at 200 AGL.

--
Paul Tomblin , not speaking for anybody
ALL programs are poems, it's just that not all programmers are poets.
-- Jonathan Guthrie in the scary.devil.monastery
  #6  
Old September 1st 03, 02:26 AM
David Megginson
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Default

Roy Smith writes:

1) Is there any point in practicing any "best forward speed" approaches
besides the ILS?


It doesn't hurt, but as a practical matter, the only time you'll get
"best speed" requests is at a busy airport with lots of jet traffic,
and in that case, it's almost certain that they're flying an ILS.


You can get the request any time you have aircraft with different
approach speeds and the controller packs things in a little too tight.
Besides, while my home airport has two ILS approaches and lots of jet
traffic, the most common preferred runway is 25, which has only NDB
and LOC(BC) approaches.

Not me. Try it some day in VFR conditions. Fly the glide slope (or
VASI) down to 200 AGL at 120 KIAS with the flaps up, then try to land
and see how much runway you use up.


You use *lots* (I've done it a few times under the hood, and once, at
110 kt, in IMC). Fortunately, you often find a 10,000 ft runway on
the end of an ILS, so there's lots to use. With an ILS on a 5000 ft
runway and a low ceiling, I'd say 'unable' to a request to approach
faster than 90 kt.


All the best,


David
  #7  
Old September 1st 03, 03:14 AM
Ben Jackson
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Default

In article ,
David Megginson wrote:

You use *lots* (I've done it a few times under the hood, and once, at
110 kt, in IMC). Fortunately, you often find a 10,000 ft runway on


I haven't done the math, but it seems like if you float down half a 2
mile runway after zooming down the ILS you're not going to be clear any
sooner that if you'd flown the ILS more slowly but made the first turnoff.

Are controllers allowed to let the trailing aircraft get closer to
the end of the runway (with you on it) than they were to you while
you were in the air on the glideslope?

--
Ben Jackson

http://www.ben.com/
  #8  
Old September 1st 03, 03:31 AM
Newps
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Ben Jackson wrote:

I haven't done the math, but it seems like if you float down half a 2
mile runway after zooming down the ILS you're not going to be clear any
sooner that if you'd flown the ILS more slowly but made the first turnoff.


Yes you will. Nothing balls up a sequence like somebody doing 90 knots
over the ground.



Are controllers allowed to let the trailing aircraft get closer to
the end of the runway (with you on it) than they were to you while
you were in the air on the glideslope?


Three miles is the separation unless visual separation is used. If
visual is used there is no separation minima other than don't let them
hit. If the trailing plane is a single than 3000 feet is what's needed,
and you do not have to be off the runway. If it's a twin then it's 4500
and you still don't have to be off the runway. If it's a jet, or some
others like most King Airs, you have to be off the runway.

  #9  
Old September 1st 03, 04:28 AM
Peter R.
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Default

Roy Smith wrote:

Not me. Try it some day in VFR conditions. Fly the glide slope (or
VASI) down to 200 AGL at 120 KIAS with the flaps up, then try to land
and see how much runway you use up.


On my last IFR proficiency lesson (my first lesson since obtaining my
instrument rating last March), the instructor had me fly the ILS at 110
knots until about DH, then slow it down and do a short field landing at
60 knots in a C172. I was able to do it and land in a few hundred feet,
but I'll be danged if I can do it again without floating/ballooning.

More practice, I suppose.

--
Peter








  #10  
Old September 2nd 03, 02:41 AM
Steve S
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Default


"Newps" wrote in message
.net...


Ben Jackson wrote:

I haven't done the math, but it seems like if you float down half a 2
mile runway after zooming down the ILS you're not going to be clear any
sooner that if you'd flown the ILS more slowly but made the first

turnoff.

Yes you will. Nothing balls up a sequence like somebody doing 90 knots
over the ground.



Except a 90 kt approach with a 20 kt headwind resulting in a 70 kt
groundspeed

Steve S


 




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