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Date: Thu, 20 Nov 2008 19:50:23 -0500
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Subject: RE: [LML] Re: Preferred Decent Angle (LIVP) for Arrival (using Chelton)
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Thread-Topic: [LML] Re: Preferred Decent Angle (LIVP) for Arrival (using Chelton)
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From: "Chuck Jensen" <cjensen@dts9000.com>

Lorn, easy enough to ask for a block to a lower level for descent.  If =
the airspace is clear, you can then descend at a more economical 300-400 =
fpm.  This efficiently converts potential energy (altitude) into =
increased speed and/or reduced power generation for the same speed.  If =
you are high up and do a 2000 fpm descent, you are effectively wasting =
most of the energy you expended climbing to the higher altitude....it's =
like slamming on the brakes of your car when you are doing 70 mph hour =
versus coasting are little cost to a lower speed---both will get you =
there and you'll come to a stop, but the cruise descent is much more =
efficient.

And, as noted, you can cancel IFR and advise that you are descending to =
some altitude.  ATC has their business to take care of...and we have =
ours.

Chuck Jensen


-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net]On Behalf Of
Lorn H Olsen
Sent: Saturday, November 15, 2008 10:07 AM
To: lml@lancaironline.net
Subject: [LML] Re: Preferred Decent Angle (LIVP) for Arrival (using
Chelton)


Jeff,

When I flew a C340 I did most of my descents at 1,000 fpm, when =20
possible. Ask ATC for lower when you are ready to descend. Most of the =20
time they will give you the lower altitude. Sometimes, they are not so =20
agreeable. Last month I was told to be "at or below" an altitude that =20
would have required a 6,000 fpm descent. When I said that I couldn't =20
do that, the controller ask me to do a 180. In this particular case, I =20
told the controller that I knew a trick and cancelled IFR.

I know that if you can't maintain a 500 fpm climb, you need to report =20
that to ATC. I believe that is the same for the descent.

In my 320, I set my 396 to descend me at 400, 500 or 1,000 fpm =20
depending on winds aloft. Sometimes I want to stay at 16,000 feet =20
longer for the tailwind. Sometimes I want to make use of the potential =20
energy for the speed. I change the descent profile on most of my =20
flights.

Your question of "what is the most common descent angle" is like =20
asking, "what is the most common wind aloft". If possible you should =20
change your descent rate based upon; 1) How hard is the rate to =20
change? 2) How busy is the arrival airport?, 3) How controlling are =20
the arrival controllers? and 4) How long do you want to stay at =20
altitude?

Now for my curiosity, how easy is the descent rate to change on the =20
Chelton. On my 396 I have about 11 keystrokes to get to the VNAV rate.

Lorn

> From: "Jeffrey Liegner, MD" <liegner@embarqmail.com>
> Date: November 14, 2008 7:09:41 PM GMT-05:00
>
> When anticipating a descent into the arrival airport, often ATC and =20
> I don't agree on the best solution.  They have their traffic =20
> separation issues and sector hand off requirements, so I =20
> understand.  But this leads to the question of what is the most =20
> common descent angle that pilots are programming into their Cheltons.
> .
> .
> Thanks.
>
> Jeff L

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