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Descent Power Quandry...

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rsrandazzo(at)precisionma
Guest

Posted: Mon Jun 25, 2007 7:54 pm Post subject: Descent Power Quandry...

Commanders!



As we prepare to put N414C back in service- I've started reviewing the

manuals and documents to ensure I have good data on various power settings.

I've run into a quandary that I thought some of you (milt!) might have some

experience with- and could thus provide some advice!



In the AFM- the originally published "descent power" called for setting the

props to 2800 RPM and selecting either 28" or 25" depending upon whether you

wanted to come down at 1000 or 2000 fpm respectively.



Tucked in the back of the AFM- I've found a bulletin from Teledyne

Continental dated 07DEC88 (thus post-dating the AFM, obviously) that

suggests avoiding high RPM and low MP, while also avoiding low RPM and high

MP combinations in order to avoid torsional vibration to the gearing/drive

train.



All of this makes perfect sense- except that there are hand written notes on

the bulletin that leave me scratching my head as to the "correct" method to

use for descent power....  (The note reads: "For descent reduce RPM between

1700 + 1400")



I called TCM seeking guidance- and they wouldn't even acknowledge that

they'd ever made my engines- never mind trying to help me find someone who

could help me.  <insert various insults to their parental lineage and

general genetic make-up here>  I called RAM- and their guy was nervous about

giving me any specific power settings (obviously- the 520L/N/M is quite

different) but he was able to tell me that on RAM engines they generally

recommend that the pilot slow the RPM considerably below cruise RPM before

descending.... 



So- you 685 drivers (and geared engine guru's)-  help me interpret what I

should be doing to manage these engines appropriately during a normal

descent?



I'm an airline guy- so I'm used to engine and energy management- and I'm not

a chop+drop guy.  I'm very comfortable managing engines that are

"procedural" by nature- but in order to succeed I really need to know which

procedure to use!  



Thanks, everyone!  Looking forward to some feedback!



Robert S. Randazzo

N414C's current custodian...

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CloudCraft(at)aol.com
Guest

Posted: Mon Jun 25, 2007 8:16 pm Post subject: Descent Power Quandry...

In a message dated 25-Jun-07 20:55:00 Pacific Daylight Time, rsrandazzo(at)precisionmanuals.com writes:

  	  Quote: 	
		  In the AFM- the originally published "descent power" called for setting the

props to 2800 RPM and selecting either 28" or 25" depending upon whether you

wanted to come down at 1000 or 2000 fpm respectively. 	


 Dear Current Custodian of N414C,

  

 The above power settings for descent look pretty good, but it's been so long since I was the custodian of N414C that I don't recall.

  

 I will say that 2800 RPM and 25" is not unreasonable as far as a MAP/RPM combination for a this engine.  

  

 I bet that you'll find that the current state of N414C's pressure vessel will help determine what MAP you use on descent: you may need the higher power at altitude to hold the cabin, so any other theories will be out the window ... or outflow valve to be more correct.

  

 I used to just hold cruise power and reduce MAP one inch per 5000' if coming down from the high teens, planning the descent with a decceleration segment to slow and configure for further descent.    The Reno basin may not give you that luxury and you may have to "dirty up" to get down after crossing the ridge lines.

   

 Now, Robert, if you'll excuse me and if I can wander off course for a moment to the discussion about the AC-680FL(P) O.E.I. performance, the -FLs were never scary to me with one engine inoperative.  The FL(P)s due to their higher weights, were.  However, I seldom operated at maximum weights because I was not flying cargo.

  

 The MR. RPM conversions certainly provided some fuel economy and freedom from gear boxes but I and many others felt that the potential of the IO-720 never made it to the prop -- or the prop never produced the potential thrust.

  

 Was because of the need for inter-coolers?  Were the props poorly matched to the engine?  I don't know but I was always disappointed in teh O.E.I. performance of the long body MR RPM conversions.

  

 I still think they're a terrific airplane and I'd still buy one if I were foolish enough to own an airplane.  

   

 N47RR has been discussed on this net many times and I would hope that Harry Merritt would log in with his comments -- I think Harry was the last one on this list who had it before it went to eBay.   It has damage history.  It's been repaired.  I was impressed with the airplane when I looked at it a few years ago here in Las Vegas, before it got dropped on the floor.  I thought it was one of the better MR RPM ships I'd seen.

  

 Wing Commander Gordon



See what's free at AOL.com. 

  [quote][b]

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rsrandazzo(at)precisionma
Guest

Posted: Tue Jun 26, 2007 9:50 am Post subject: Descent Power Quandry...

WCG-

  

 Ah- now did I know N414C  was in your stable as well as Milt's?  Maybe you mentioned that and I've  since forgotten.  (uh oh...)

  

 I flew J-32s for a  thousand plus hours- I learned to be very wary of negative torque loading- so I  don't find the 520Ks to be a mystery- and I was comfortably using 28"25" and  2800RPM without sensing any torque loading...  I think I'll stick with that  unless I find compelling evidence otherwise.

  

 Energy management around  here just means having to do some of that piloting sh*t.  I can mitigate  having to use my piloting skills by planning ahead, however!  Or  sometimes coercing ATC by using the phrase "unable."  (They love that one,  don't they?)

  

 I'm expecting we'll see  414C back in the air in mid-July...  Just in time for the seasonal high in  fuel prices...

  

 Rob

  

  



   From: owner-commander-list-server(at)matronics.com  [mailto:owner-commander-list-server(at)matronics.com] On Behalf Of  CloudCraft(at)aol.com

Sent: Monday, June 25, 2007 21:16

To:  commander-list(at)matronics.com

Subject: Re: Descent  Power Quandry...

 

  In a message dated 25-Jun-07 20:55:00 Pacific Daylight Time,  rsrandazzo(at)precisionmanuals.com writes:

  	  Quote: 	
		  In the AFM- the originally published "descent power" called for    setting the

props to 2800 RPM and selecting either 28" or 25" depending    upon whether you

wanted to come down at 1000 or 2000 fpm    respectively. 	


 Dear Current Custodian of  N414C,

  

 The above power settings for descent look pretty  good, but it's been so long since I was the custodian of N414C that I don't  recall.

  

 I will say that 2800 RPM and 25" is not  unreasonable as far as a MAP/RPM combination for a this engine.   

  

 I bet that you'll find that the current state of  N414C's pressure vessel will help determine what MAP you use on descent: you may  need the higher power at altitude to hold the cabin, so any other theories will  be out the window ... or outflow valve to be more correct.

  

 I used to just hold cruise power and reduce MAP  one inch per 5000' if coming down from the high teens, planning the descent with  a decceleration segment to slow and configure for further  descent.    The Reno basin may not give you that luxury and you  may have to "dirty up" to get down after crossing the ridge  lines.

   

 Now, Robert, if you'll excuse me and if I can  wander off course for a moment to the discussion about the AC-680FL(P) O.E.I.  performance, the -FLs were never scary to me with one engine inoperative.   The FL(P)s due to their higher weights, were.  However, I seldom  operated at maximum weights because I was not flying  cargo.

  

 The MR. RPM conversions certainly provided some  fuel economy and freedom from gear boxes but I and many others felt that the  potential of the IO-720 never made it to the prop -- or the prop never produced  the potential thrust.

  

 Was because of the need for inter-coolers?   Were the props poorly matched to the engine?  I don't know but I was always  disappointed in teh O.E.I. performance of the long body MR RPM  conversions.

  

 I still think they're a terrific airplane and I'd  still buy one if I were foolish enough to own an airplane.   

   

 N47RR has been discussed on this net many times  and I would hope that Harry Merritt would log in with his comments -- I think  Harry was the last one on this list who had it before it went to  eBay.   It has damage history.  It's been repaired.  I was  impressed with the airplane when I looked at it a few years ago here in Las  Vegas, before it got dropped on the floor.  I thought it was one of the  better MR RPM ships I'd seen.

  

 Wing Commander  Gordon



   See what's free at AOL.com.  

 	  Quote: 	
		  



href="http://www.matronics.com/Navigator?Commander-List">http://www.matronics.com/Navigator?Commander-List

href="http://forums.matronics.com">http://forums.matronics.com



	




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CloudCraft(at)aol.com
Guest

Posted: Tue Jun 26, 2007 10:03 am Post subject: Descent Power Quandry...

In a message dated 26-Jun-07 10:51:10 Pacific Daylight Time,  rsrandazzo(at)precisionmanuals.com writes:

  	  Quote: 	
		     I'm expecting we'll see    414C back in the air in mid-July...  Just in time for the seasonal high    in fuel prices...

	


 

 You won't want to miss the Summer fuel gouge!

  

 I.O.U. the trend monitors from N414C.  I've given up the  storage locker, moved all the junk into my garage and am buying gasoline with  the money I'm saving.

  

 Next I have to do some box diving and find the trends.  I will  scan to .pdf files and send you a sampling of the engine / flight data from my  time in your airplane.

  

 BTW, I flew it in 1997/1998, based at Lee's Summit, MO in the  summer and Richards Gebaur (now closed) in the winter.  

  

 It was leased by McKinley Communications in Blue Springs, MO, who  was the P.R. firm Twin Commander hired to start and run an owners'  association.  They hired me full time to fly them on their business trips  and to run the Twin Commander Flight Group.

  

 Dick MacCoon (MR RPM) owned the airplane and it was to be the  conformity article for the Orenda conversion program.  

  

 The Orenda program flopped, MR RPM put the airplane(s) up for sale  and McKinley Communications had a going away party for  me.



See what's free at AOL.com. 

  [quote][b]

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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rsrandazzo(at)precisionma
Guest

Posted: Tue Jun 26, 2007 11:14 am Post subject: Descent Power Quandry...

WCG-

  

 Now- see?  I DO  remember that now....  Must need more memory. Mine is getting  full.

  

 Rob

  



   From: owner-commander-list-server(at)matronics.com  [mailto:owner-commander-list-server(at)matronics.com] On Behalf Of  CloudCraft(at)aol.com

Sent: Tuesday, June 26, 2007  11:03

To: commander-list(at)matronics.com

Subject: Re:  Descent Power Quandry...

 

  In a message dated 26-Jun-07 10:51:10 Pacific Daylight Time,  rsrandazzo(at)precisionmanuals.com writes:

  	  Quote: 	
		     I'm expecting we'll see    414C back in the air in mid-July...  Just in time for the seasonal high    in fuel prices...

	


 

 You won't want to miss the Summer fuel gouge!

  

 I.O.U. the trend monitors from N414C.  I've given up the  storage locker, moved all the junk into my garage and am buying gasoline with  the money I'm saving.

  

 Next I have to do some box diving and find the trends.  I will  scan to .pdf files and send you a sampling of the engine / flight data from my  time in your airplane.

  

 BTW, I flew it in 1997/1998, based at Lee's Summit, MO in the  summer and Richards Gebaur (now closed) in the winter.  

  

 It was leased by McKinley Communications in Blue Springs, MO, who  was the P.R. firm Twin Commander hired to start and run an owners'  association.  They hired me full time to fly them on their business trips  and to run the Twin Commander Flight Group.

  

 Dick MacCoon (MR RPM) owned the airplane and it was to be the  conformity article for the Orenda conversion program.  

  

 The Orenda program flopped, MR RPM put the airplane(s) up for sale  and McKinley Communications had a going away party for  me.



   See what's free at AOL.com.  

 	  Quote: 	
		  



href="http://www.matronics.com/Navigator?Commander-List">http://www.matronics.com/Navigator?Commander-List

href="http://forums.matronics.com">http://forums.matronics.com



	




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n395v

Joined: 10 Jan 2006
Posts: 450

Posted: Sat Jul 07, 2007 8:34 am Post subject: Re: Descent Power Quandry...

Start with 25/2800 then adjust as need/conditions feel/dictate.



You will feel or hear it if it ain't right and soon will get to know what settings not to use.

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_________________
Milt

rsrandazzo(at)precisionma
Guest

Posted: Sun Jul 08, 2007 8:10 pm Post subject: Descent Power Quandry...

Milt-



Thanks- that was what I was hoping to hear.  



How's your airplane search going?



Rob 



--

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