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0. 12:10 AM - Make A List Contribution - It's Your Personal Squelch Button... (Matt Dralle)
1. 08:35 PM - Re: Can we talk 685's? (stratobee)
2. 11:19 PM - Re: Can we talk 685's? (Keith S. Gordon)
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Subject: | Make A List Contribution - It's Your Personal Squelch |
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Subject: | Re: Can we talk 685's? |
Anyone?
--------
Adam
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=387346#387346
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Subject: | Re: Can we talk 685's? |
I'd like some more meat on the 685 and/or the 680FPL. I know all the usual
stuff - how it needs a lot of rwy fully loaded, how the engines will ruin y
ou etc, etc.
But what I would like to know more about is real world operation etc:
1.What's the certified ceiling?
2. What can you expect the burn at 20K plus and 55%, 45%, TAS?
3. Do they all come with 322gal tanks or is that an add on?
4. Are cylinders etc plentiful and easy to get hold of?
5. How terrible is the Skydrol system? Does it run the pressurisation as we
ll?
6. Any significant AD's?
7. They seem to have come with a few different engines ranging from 390hp t
o 450hp - any particular one to avoid?
8. What is the difference between the 685 and the 680FPL?
OK. Back from my trip and will offer what information I still remember fro
m the 685 and 680FLP days -- but my disclaimer is that it's been way too lo
ng since I've been around either, so I'll hope Sir Barry, Bill Leff and Mil
t Concanon will do some fact checking on this.
1. The service ceiling on the 685 is FL250. The 680 has a service ceiling
in excess of FL280 but that's not a fair comparison. For a Part 23 piston
airplane the service ceiling is where a 50 foot per minute climb can not be
sustained. The 685, being the same airframe as the 690 Turbo Commander ha
s its service ceiling set by Part 23 structural requirements for turbine ai
rplanes.
2. Don't remember for sure, but at about 65% power I remember 45 gph block
fuel flow. Can't tell you what the lower power settings would be.
3. 322 is standard fuel on the 685. The 680FLP will have 225. (223 useabl
e)
4. Cylinders? Don't know. If you do everything exactly right on the 685,
you'll only replace 3 cylinders a year.
5. Skydrol is very toxic, expensive and an excellent paint stripper. Thank
you for asking. It also has good fire retardancy and that's why it's used
in high pressure systems.
On the stock AC680-FLP the 3000 psi system runs the cabin supercharger; the
pressure is reduced to 1000 psi for the utilities (Gear, flaps, brakes, no
sewheel steering). The Achilles heel of the AC-680-FLP are the 3000 psi h
ydraulic (Skydrol) pumps. They were hard to find 15 years ago. I can onl
y imagine they're no less difficult to find now.
The 685 has the 1000 psi, Mil-H-5606 (red fluid) hydraulic system and cabin
pressurization is via bleed air from the turbochargers.
6. The 685, being the Turbo Commander airframe, is subject to the recurring
spar corrosion inspection unless one does the spar strap to get rid of the
AD. I don't know of any 685s that did that because the spar mod is more e
xpensive than the cost of the entire airplane -- maybe 2 entire airplanes.
7. The stock AC680-FLP has the Lycoming IGSO-540 engine. 380hp, mechanical
supercharging. This engine was only installed on the 680-F series Aero Co
mmanders. The MR. RPM conversion changes that engine to a Lycoming IO-720
with after market turbochargers, producing 400 hp with turbo normalizing.
Some MR. RPM conversions included a switch to 5606 hydraulic fluid. Bleed
air pressurization eliminates the cabin supercharger on the RPMs.
The AC-685 comes with the Continental GTSIO-520-K producing 435 hp. (Same
engine that Cessna uses on the CE-421 and CE-404 but with the good manners
to only extract 375 hp from it; 435hp is a lot of power to pull out of 520
cubic inches.) This is a turbo charged engine, not supercharged by a mecha
nical supercharger as the AC-680 has.
8. Let's see ... how to do this:
AC-680-FLP
Same airframe as the AC-680-FL -- a stretched version of the AC-500B, reall
y, but with some structural enhancements to allow it to weigh up to 8500 lb
s.
3000 psi Skydrol hydraulic system
pressurization via cabin supercharger
Good runway performance; will generally allow full fuel and 4 seats filled.
Could be pressed into bush service.
AC-685
Same airframe as the 690 Turbo Commanders
1000 psi 5606 hydraulic system
pressurization via tapping bleed air off the turbo chargers
Poor runway performance; full fuel will allow one or two seats filled
Quiet. Comfortable for long duration flights. Belongs on civilized airpor
ts with long runways.
Being based on Part 23 certification requirements for a turbine powered air
plane, the flight manual is modern, very complete and provides more perform
ance information than any of the piston powered Commanders.
If you're obsessed with range, the 685 is your airplane -- but only if it's
just you and one or two skinny super models. 1500 nm might be possible if
you're willing to pull it back to less than 190 to 200 KTAS. I don't have
any data to tell you what fuel burn would be at ultra long range cruise sp
eed. However, there are two things to consider:
To maintain pressurization at FL200 you may have to run more power than wha
t an ultra-long range power setting might be, and, too low a power setting
at initial weight at top of climb will cost in terms of TAS due to the angl
e of attack you'll need to keep the plane in level flight.
I'd think initial cruising in the mid-to-high teens is more conducive to ul
tra long range fuel flow.
Adam, I hope I answered most of your questions. I only wish I had fuel flo
w data vs. TAS to give you, because that's the key to your choice of airpla
nes.
Let us know what your thoughts are.
Keith S. Gordon
(aka Wing Commander Gordon)
Life is not simple anywhere. Probably less so elsewhere.
KHND RNAV Lead
FAASTeam Lead Rep, Las Vegas
NBAA Access Committee
Las Vegas Airspace Users' Council, NBAA Rep
Las Vegas RNAV Optimization Work Group, NBAA Rep
Las Vegas Class B Redesign Committee, NBAA Rep
-----Original Message-----
From: CloudCraft / K.S.Gordon <cloudcraft@aol.com>
m>
Sent: Mon, Nov 5, 2012 6:09 pm
Subject: RE: Commander-List: Can we talk 685's?
Adam,
Too much to discuss via a smartphone that requires everything to be retyped
5 times.
When I get home to a full sized keyboard I'll do my best to answer your que
stions if nobody else has by then.
~KG~
Keith S. Gordon
on the fly
stratobee <adam@adamfrisch.com> wrote:
I'd like some more meat on the 685 and/or the 680FPL. I know all the usual
stuff - how it needs a lot of rwy fully loaded, how the engines will ruin y
ou etc, etc.
But what I would like to know more about is real world operation etc:
1.What's the certified ceiling?
2. What can you expect the burn at 20K plus and 55%, 45%, TAS?
3. Do they all come with 322gal tanks or is that an add on?
4. Are cylinders etc plentiful and easy to get hold of?
5. How terrible is the Skydrol system? Does it run the pressurisation as we
ll?
6. Any significant AD's?
7. They seem to have come with a few different engines ranging from 390hp t
o 450hp - any particular one to avoid?
8. What is the difference between the 685 and the 680FPL?
Any experiences greatly appreciated.
--------
Adam
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=386982#386982
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=EF=BD=EF=BDM4=EF=BD=EF=BD=EF=BDx=EF=BD=EF=BD=EF=BD
=EF=BDw=EF=BDr=EF=BD=EF=BD=EF=BD=EF=BD
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