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Can we talk 685's?

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stratobee

Joined: 28 Dec 2010
Posts: 159
Location: Los Angeles

Posted: Mon Nov 05, 2012 5:25 pm Post subject: 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 you 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 well like in the 680FP?

6. Any significant AD's? Wing spar?

7. Parts easy to come by? Does it share a lot of stuff with the 690?

8. They seem to have come with a few different engines ranging from 390hp to 450hp - any particular one to avoid?

9. What is the difference between the 685 and the 680FPL?



Any experiences greatly appreciated.

_________________
Adam

cloudcraft(at)aol.com
Guest

Posted: Mon Nov 05, 2012 6:09 pm Post subject: 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 questions if nobody else has by then.

~KG~


Keith S. Gordon

on the flystratobee <adam(at)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 you 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 well?

6. Any significant AD's?

7. They seem to have come with a few different engines ranging from 390hp to 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

stratobee

Joined: 28 Dec 2010
Posts: 159
Location: Los Angeles

Posted: Mon Nov 05, 2012 7:13 pm Post subject: Re: Can we talk 685's?

Thanks Keith - look forward to it.



The reason I have an interest is of course firstly that it's a Commander, but secondly because I have this obsession with long range. And 322 gals - if one could pull back and get somewhere around 30gals total up high - would be very interesting. I'm guessing, but that should possibly give more than 1500nm range, maybe even more.

_________________
Adam

stratobee

Joined: 28 Dec 2010
Posts: 159
Location: Los Angeles

Posted: Thu Nov 08, 2012 8:35 pm Post subject: Re: Can we talk 685's?

Anyone?

_________________
Adam

cloudcraft(at)aol.com
Guest

Posted: Thu Nov 08, 2012 11:19 pm Post subject: Can we talk 685's?

 	  Quote: 	
		  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 you 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 well?

    6. Any significant AD's?

    7. They seem to have come with a few different engines ranging from 390hp to 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 from the 685 and 680FLP days -- but my disclaimer is that it's been way too long since I've been around either, so I'll hope Sir Barry, Bill Leff and Milt 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 has its service ceiling set by Part 23 structural requirements for turbine airplanes.

   

   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 useable)

   

   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, nosewheel steering).   The Achilles heel of the AC-680-FLP are the 3000 psi hydraulic (Skydrol) pumps.   They were hard to find 15 years ago.  I can only 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 expensive 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 Commanders.  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 mechanical 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, really, but with some structural enhancements to allow it to weigh up to 8500 lbs.
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 airports with long runways.  

   
Being based on Part 23 certification requirements for a turbine powered airplane, the flight manual is modern, very complete and provides more performance 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 speed.   However, there are two things to consider:

   

   To maintain pressurization at FL200 you may have to run more power than what 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 angle 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 ultra long range fuel flow.

   

   Adam, I hope I answered most of your questions.  I only wish I had fuel flow data vs. TAS to give you, because that's the key to your choice of airplanes.

   

   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

         

    

         

    

        --

nico(at)cybersuperstore.c
Guest

Posted: Fri Nov 09, 2012 4:45 am Post subject: Can we talk 685's?

I reposted Keith's response on our Facebook page: www.facebook.com/commanderflight

 

Thanks, Keith.

 

 

From: owner-commander-list-server(at)matronics.com [mailto:owner-commander-list-server(at)matronics.com] On Behalf Of Keith S. Gordon

Sent: Thursday, November 08, 2012 11:19 PM

To: commander-list(at)matronics.com

Subject: Re: Can we talk 685's?



 

 

 	  Quote: 	
		  

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 you 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 well?

6. Any significant AD's?

7. They seem to have come with a few different engines ranging from 390hp to 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 from the 685 and 680FLP days -- but my disclaimer is that it's been way too long since I've been around either, so I'll hope Sir Barry, Bill Leff and Milt 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 has its service ceiling set by Part 23 structural requirements for turbine airplanes.



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 useable)



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, nosewheel steering).   The Achilles heel of the AC-680-FLP are the 3000 psi hydraulic (Skydrol) pumps.   They were hard to find 15 years ago.  I can only 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 expensive 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 Commanders.  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 mechanical supercharger as the AC-680 has.



8.  Let's see ... how to do this:



AC-680-FLPSame airframe as the AC-680-FL -- a stretched version of the AC-500B, really, but with some structural enhancements to allow it to weigh up to 8500 lbs.
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-685Same 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 airports with long runways.  
Being based on Part 23 certification requirements for a turbine powered airplane, the flight manual is modern, very complete and provides more performance 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 speed.   However, there are two things to consider:



To maintain pressurization at FL200 you may have to run more power than what 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 angle 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 ultra long range fuel flow.



Adam, I hope I answered most of your questions.  I only wish I had fuel flow data vs. TAS to give you, because that's the key to your choice of airplanes.



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



 



 



--

stratobee

Joined: 28 Dec 2010
Posts: 159
Location: Los Angeles

Posted: Fri Nov 09, 2012 4:58 am Post subject: Re: Can we talk 685's?

Thanks Keith - really appreciate it!

_________________
Adam

cloudcraft(at)aol.com
Guest

Posted: Fri Nov 09, 2012 7:01 am Post subject: Can we talk 685's?

At your service.

 ~KG~

    

  

     

  

    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

     

  

     

  

    --

moe-rosspistons(at)hotmai
Guest

Posted: Fri Nov 09, 2012 1:42 pm Post subject: Can we talk 685's?

Hi Adam,



While I certainly do not profess to know nearly as much a Keith about the aircraft, here are a couple of observations based on flying about 1,000 hours in my 680F(p), which is very  similar to the 680FLP.  The 680FLP is longer than the 680F(p). The engines are the same (IGSO540).  The New York Air Brake skydrol pumps can be overhauled at a cost of about $ 4,000.00 each.  If you purchase a plane which uses Skydrol try to find one which has been painted with Jet Glow.  Jet Glow is very skydrol resistant, and although I have experienced a couple of leaks since having it painted with Jet Glow none of the paint came off, even after sitting for about a week when it was wet.  Every other paint comes off if you don't wash it down within about 1/2 hour with alkey.  Skydrol is much less toxic now than it was in previous times, as they changed the formulation several times a few years ago.  

The useful service sealing on the 680F(p) is 22,000 feet as the plane must be depressurized at that altitude.  The plane likes 16,000 to 18,000 feet from a speed, handling, fuel consumption standpoint.

Regards,

Me  

[quote] Subject: Re: Can we talk 685's?

 From: adam(at)adamfrisch.com

 Date: Fri, 9 Nov 2012 04:58:17 -0800

 To: commander-list(at)matronics.com

 

 --> Commander-List message posted by: "stratobee" <adam(at)adamfrisch.com>

 

 Thanks Keith - really appreciate it!

 

 --------

 Adam

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=387357#387357

cloudcraft(at)aol.com
Guest

Posted: Fri Nov 09, 2012 2:14 pm Post subject: Can we talk 685's?

 	  Quote: 	
		  The New York Air Brake skydrol pumps can be overhauled at a cost of about $ 4,000.00 each.  If you purchase a plane which uses Skydrol try to find one which has been painted with Jet Glow.  Jet Glow is very skydrol resistant, and although I have experienced a couple of leaks since having it painted with Jet Glow none of the paint came off, even after sitting for about a week when it was wet.  Every other paint comes off if you don't wash it down within about 1/2 hour with alkey.  Skydrol is much less toxic now than it was in previous times, as they changed the formulation several times a few years ago.  	


     Mo,

 

 Thanks for posting your experience.  Great stuff.  

 

 Question: Are you field overhauling your New York Airbrake hydraulic pumps or sending them to an O/H shop.   If rebuilding in the field, where do you get the kits and if sending to a shop, who are you using?

 

 I expect Morris Kernick is the most important resource on the subject.

 

 Also glad to hear Jet Glow holds up to Skydrol.   Last AC-680-FLP I visited had its paint peeling on the right side due to a gear actuator leak and a leak at the reservoir.

 

 ~KG~

  

     

  

    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

     

  

     

  

    --

moe-rosspistons(at)hotmai
Guest

Posted: Fri Nov 09, 2012 4:11 pm Post subject: Can we talk 685's?

Keith,



Thanks for waking me up on this post as there was a mistake in it.  The pumps were ONLY about $ 2,000.00 each ($  4,000.00 for ship set).  It has been several years (thank goodness) since having these rebuilt.  Once, I used Thunder Airmotive, Sun Valley, CA. (818) 683-0050 and while the bird was at Commander-Aero in OH. we did a spare.  The guys at Thunder once did a repair and test for only $ 434.00, however that was nine years ago.

Also, since Solutia Technical Service took over Skydrol they are really great to deal with, and once did a complimentary fluid check for me after an overheating problem.  They advised that we filter the fluid by placing a new filter in my Skydrol mule and running it through the mule filter at least twice. The overheating problem was due to the filter in the tank being clogged (as diagnosed over the phone by Morris).   We have been unable to locate the supplier of parts for a field overhaul, but haven't searched in several years.

Regards,

Moe

To: commander-list(at)matronics.com

Subject: Re: Re: Can we talk 685's?

From: cloudcraft(at)aol.com

Date: Fri, 9 Nov 2012 17:14:20 -0500



   

  

     	  Quote: 	
		  The New York Air Brake skydrol pumps can be overhauled at a cost of about $ 4,000.00 each.  If you purchase a plane which uses Skydrol try to find one which has been painted with Jet Glow.  Jet Glow is very skydrol resistant, and although I have experienced a couple of leaks since having it painted with Jet Glow none of the paint came off, even after sitting for about a week when it was wet.  Every other paint comes off if you don't wash it down within about 1/2 hour with alkey.  Skydrol is much less toxic now than it was in previous times, as they changed the formulation several times a few years ago.   	


     Mo,

 

 Thanks for posting your experience.  Great stuff.  

 

 Question: Are you field overhauling your New York Airbrake hydraulic pumps or sending them to an O/H shop.   If rebuilding in the field, where do you get the kits and if sending to a shop, who are you using?

 

 I expect Morris Kernick is the most important resource on the subject.

 

 Also glad to hear Jet Glow holds up to Skydrol.   Last AC-680-FLP I visited had its paint peeling on the right side due to a gear actuator leak and a leak at the reservoir.

 

 ~KG~

  

     

  

    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

     

  

     

  

    --

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