---------------------------------------------------------- Commander-List Digest Archive --- Total Messages Posted Fri 04/13/07: 16 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:59 AM - Servo Failure (Steve) 2. 08:07 AM - Re: Sun-N-Fun (WINGFLYER1@aol.com) 3. 08:46 AM - Re: Servo Failure () 4. 09:37 AM - Re: Servo Failure (MASON Chevaillier) 5. 11:28 AM - Pressure Carbs (Bill Kirkwood) 6. 12:16 PM - Re: Pressure Carbs (Harry Merritt) 7. 01:02 PM - Re: Pressure Carbs (steve) 8. 01:58 PM - Re: Servo Failure (John Vormbaum) 9. 03:39 PM - Re: Servo Failure (Robert S. Randazzo) 10. 04:57 PM - Re: Sun-N-Fun (N560WM@aol.com) 11. 04:59 PM - Re: Re: Servo Failure (Steven) 12. 05:42 PM - Re: Re: Servo Failure (John Vormbaum) 13. 07:21 PM - Re: Re: Servo Failure (Steven) 14. 07:48 PM - Re: Re: Servo Failure (Robert S. Randazzo) 15. 08:42 PM - Re: Re: Servo Failure (John Vormbaum) 16. 11:21 PM - Re: Re: Servo Failure (Robert S. Randazzo) ________________________________ Message 1 _____________________________________ Time: 06:59:53 AM PST US From: "Steve" Subject: Commander-List: Servo Failure Had an odd failure the other day I thought I would share, mainly because it was a failure mode I hadn't ever thought of and if I had I might have recognized it (maybe not). It might help another 500 series driver someday. We replaced a couple bladders (and found out from filling the airplane twice parked two different directions it holds 150 gallons, not 156). Also recalibrated the gauge with 20 gallons aboard. (twice). I'd like to think I've got fuel management pretty well figured for this aircraft, but for our work there is sometimes a lot of climbs and descents, but overall it's never varied much from predicted. First trip out from replacing bladders was about 4.5 hours. We were at 7500' or so W.O.T. & L.O.P. Rougher than hell as usual dropping into 'happy valley' here back home. Pulling throttles back as we descend. Gas (pumps) Mixture (up) Gear (down) props still to go and getting close to turning about a four mile final (there's a mountain in the way of a shorter final). Something ain't right. Feels an awful lot like fuel starvation. Now we're in the real serious bumps down low, and of course the gauge is bouncing off empty and you figure maybe you blew your math, and the gauge was wrong all along. Definately feels like we're loosing an engine but at this point getting knocked around like we were and in the descent for landing, its hard to tell yet exactly which one. Beans, we loose one engine from fuel starvation, that means we're about to lose another and this is a piss poor place to be loosing it, just a big tree covered hill between me and the airport. Quit descending, and went for some height, waiting to stow one one if it asked to be and trying to tell just what was going on. With a couple inches of throttle travel the right engine has no juice, but we're going to make the airport long as the left one keeps running which we're not at all sure of. Long story short, the past two rebuilds on the fuel servo from two different shops we believe to be not very good. I had exactly the fuel I thought I had. Turns out (if we understand it right) there was mechanical wear internally to the servo that stuck wide open throttle fuel levels at near idle throttle settings. So when power came back on the lever, the fuel remained full tilt and essentially flooded the engine to the point of killing it. Couple things: I wasn't ever in the trouble I thought I might be. Never needed to firewall it, raise the gear, flaps. If I did, there was a good chance the right engine would have cleared itself after a bit and recovered to develop full power in short order. A lot of my focus has been identifying failed engines on departure, in a climb. Its a different critter to identify a failed engine in a descent. Even harder if it's only partly failing going downhill in moderate turbulence. This engine was probably controllable by using the mixture control, but it would be asking a lot to have made that quick a diagnostic and remedy on the fly during final. My last trip was 5 hours and I roughly figured I'd put 120 gallons back into the thing to fill it. It was good to see it took 118. I hope this posting was appropriate. I'm always interested in failure modes, and perhaps one or two others might take something interesting from the above and file it away..... Steve ________________________________ Message 2 _____________________________________ Time: 08:07:43 AM PST US From: WINGFLYER1@aol.com Subject: Re: Commander-List: Sun-N-Fun Pat, I hope to be at sun-n-Fun . I will be staying in Sarasota with friends and driving up. But would be glad to attend. Thanks Gil Walker N-6819-Q. 615-373-5703 ************************************** See what's free at http://www.aol.com. ________________________________ Message 3 _____________________________________ Time: 08:46:03 AM PST US From: Subject: Re: Commander-List: Servo Failure Very interesting Steve. THANKS. R. Mansfield N91ES ---- Steve wrote: > > Had an odd failure the other day I thought I would share, mainly because it > was a failure mode I hadn't ever thought of and if I had I might have > recognized it (maybe not). It might help another 500 series driver someday. > > We replaced a couple bladders (and found out from filling the airplane twice > parked two different directions it holds 150 gallons, not 156). Also > recalibrated the gauge with 20 gallons aboard. (twice). I'd like to think > I've got fuel management pretty well figured for this aircraft, but for our > work there is sometimes a lot of climbs and descents, but overall it's never > varied much from predicted. > > First trip out from replacing bladders was about 4.5 hours. We were at 7500' > or so W.O.T. & L.O.P. Rougher than hell as usual dropping into 'happy > valley' here back home. Pulling throttles back as we descend. Gas (pumps) > Mixture (up) Gear (down) props still to go and getting close to turning > about a four mile final (there's a mountain in the way of a shorter final). > Something ain't right. Feels an awful lot like fuel starvation. Now we're in > the real serious bumps down low, and of course the gauge is bouncing off > empty and you figure maybe you blew your math, and the gauge was wrong all > along. Definately feels like we're loosing an engine but at this point > getting knocked around like we were and in the descent for landing, its hard > to tell yet exactly which one. Beans, we loose one engine from fuel > starvation, that means we're about to lose another and this is a piss poor > place to be loosing it, just a big tree covered hill between me and the > airport. Quit descending, and went for some height, waiting to stow one one > if it asked to be and trying to tell just what was going on. With a couple > inches of throttle travel the right engine has no juice, but we're going to > make the airport long as the left one keeps running which we're not at all > sure of. > > Long story short, the past two rebuilds on the fuel servo from two different > shops we believe to be not very good. I had exactly the fuel I thought I > had. Turns out (if we understand it right) there was mechanical wear > internally to the servo that stuck wide open throttle fuel levels at near > idle throttle settings. So when power came back on the lever, the fuel > remained full tilt and essentially flooded the engine to the point of > killing it. > > Couple things: > > I wasn't ever in the trouble I thought I might be. > > Never needed to firewall it, raise the gear, flaps. If I did, there was a > good chance the right engine would have cleared itself after a bit and > recovered to develop full power in short order. > > A lot of my focus has been identifying failed engines on departure, in a > climb. Its a different critter to identify a failed engine in a descent. > Even harder if it's only partly failing going downhill in moderate > turbulence. > > This engine was probably controllable by using the mixture control, but it > would be asking a lot to have made that quick a diagnostic and remedy on the > fly during final. > > > > My last trip was 5 hours and I roughly figured I'd put 120 gallons back into > the thing to fill it. It was good to see it took 118. > > I hope this posting was appropriate. I'm always interested in failure modes, > and perhaps one or two others might take something interesting from the > above and file it away..... > > Steve > > > > > ________________________________ Message 4 _____________________________________ Time: 09:37:04 AM PST US From: "MASON Chevaillier" Subject: Re: Commander-List: Servo Failure sc, tnx, this shud be a help to all. mason >From: >To: commander-list@matronics.com >Subject: Re: Commander-List: Servo Failure >Date: Fri, 13 Apr 2007 11:45:54 -0400 > > >Very interesting Steve. THANKS. > >R. Mansfield >N91ES > > >---- Steve wrote: > > > > Had an odd failure the other day I thought I would share, mainly because >it > > was a failure mode I hadn't ever thought of and if I had I might have > > recognized it (maybe not). It might help another 500 series driver >someday. > > > > We replaced a couple bladders (and found out from filling the airplane >twice > > parked two different directions it holds 150 gallons, not 156). Also > > recalibrated the gauge with 20 gallons aboard. (twice). I'd like to >think > > I've got fuel management pretty well figured for this aircraft, but for >our > > work there is sometimes a lot of climbs and descents, but overall it's >never > > varied much from predicted. > > > > First trip out from replacing bladders was about 4.5 hours. We were at >7500' > > or so W.O.T. & L.O.P. Rougher than hell as usual dropping into 'happy > > valley' here back home. Pulling throttles back as we descend. Gas >(pumps) > > Mixture (up) Gear (down) props still to go and getting close to turning > > about a four mile final (there's a mountain in the way of a shorter >final). > > Something ain't right. Feels an awful lot like fuel starvation. Now >we're in > > the real serious bumps down low, and of course the gauge is bouncing off > > empty and you figure maybe you blew your math, and the gauge was wrong >all > > along. Definately feels like we're loosing an engine but at this point > > getting knocked around like we were and in the descent for landing, its >hard > > to tell yet exactly which one. Beans, we loose one engine from fuel > > starvation, that means we're about to lose another and this is a piss >poor > > place to be loosing it, just a big tree covered hill between me and the > > airport. Quit descending, and went for some height, waiting to stow one >one > > if it asked to be and trying to tell just what was going on. With a >couple > > inches of throttle travel the right engine has no juice, but we're going >to > > make the airport long as the left one keeps running which we're not at >all > > sure of. > > > > Long story short, the past two rebuilds on the fuel servo from two >different > > shops we believe to be not very good. I had exactly the fuel I thought I > > had. Turns out (if we understand it right) there was mechanical wear > > internally to the servo that stuck wide open throttle fuel levels at >near > > idle throttle settings. So when power came back on the lever, the fuel > > remained full tilt and essentially flooded the engine to the point of > > killing it. > > > > Couple things: > > > > I wasn't ever in the trouble I thought I might be. > > > > Never needed to firewall it, raise the gear, flaps. If I did, there was >a > > good chance the right engine would have cleared itself after a bit and > > recovered to develop full power in short order. > > > > A lot of my focus has been identifying failed engines on departure, in a > > climb. Its a different critter to identify a failed engine in a descent. > > Even harder if it's only partly failing going downhill in moderate > > turbulence. > > > > This engine was probably controllable by using the mixture control, but >it > > would be asking a lot to have made that quick a diagnostic and remedy on >the > > fly during final. > > > > > > > > My last trip was 5 hours and I roughly figured I'd put 120 gallons back >into > > the thing to fill it. It was good to see it took 118. > > > > I hope this posting was appropriate. I'm always interested in failure >modes, > > and perhaps one or two others might take something interesting from the > > above and file it away..... > > > > Steve > > > > > > > > > > > > ________________________________ Message 5 _____________________________________ Time: 11:28:55 AM PST US From: "Bill Kirkwood" Subject: Commander-List: Pressure Carbs Did I hear someone say that overhauling pressure carburetors was relatively inexpensive? The last quote I got was $2500! ________________________________ Message 6 _____________________________________ Time: 12:16:19 PM PST US From: "Harry Merritt" Subject: Re: Commander-List: Pressure Carbs ps5 2,500.00 ps7 4000.00 ----- Original Message ----- From: Bill Kirkwood To: commander-list@matronics.com Sent: Friday, April 13, 2007 2:28 PM Subject: Commander-List: Pressure Carbs Did I hear someone say that overhauling pressure carburetors was relatively inexpensive? The last quote I got was $2500! ________________________________ Message 7 _____________________________________ Time: 01:02:26 PM PST US From: "steve" Subject: RE: Commander-List: Pressure Carbs Bill, I would have to get to my other laptop but I have a PS5 that for sale that needs rebuilding and the quote I got a few months ago was at best guess about 1800 from a reputable house. I will check it tomorrow and let you know. Steve G. _____ From: owner-commander-list-server@matronics.com [mailto:owner-commander-list-server@matronics.com] On Behalf Of Harry Merritt Sent: Friday, April 13, 2007 2:13 PM Subject: Re: Commander-List: Pressure Carbs ps5 2,500.00 ps7 4000.00 ----- Original Message ----- From: Bill Kirkwood Sent: Friday, April 13, 2007 2:28 PM Subject: Commander-List: Pressure Carbs Did I hear someone say that overhauling pressure carburetors was relatively inexpensive? The last quote I got was $2500! href="http://www.matronics.com/Navigator?Commander-List">http://www.matronic s.com/Navigator?Commander-List href="http://forums.matronics.com">http://forums.matronics.com ________________________________ Message 8 _____________________________________ Time: 01:58:28 PM PST US From: "John Vormbaum" Subject: Re: Commander-List: Servo Failure Steve, Count yourself fortunate that you were safe the whole time. I'm sure I would NOT have recognized that failure mode at all...and it would be extra tough to diagnose in bumps, on a descent, when you think you might have to land short. One thing I do differently in my 500B is to NOT use the fuel boost pumps on approach, even though I was initially trained to. I've heard a couple of stories of not-great fuel systems where the pumps allowed an engine to flood & die when the power was pulled back. Have you checked to see if the pumps have any effect on the engines under low power settings? Just my $0.02 and probably not related to your servo issue in any way. Cheers & glad you got down safely, /John ----- Original Message ----- From: "Steve" Sent: Friday, April 13, 2007 6:58 AM Subject: Commander-List: Servo Failure > > Had an odd failure the other day I thought I would share, mainly because > it was a failure mode I hadn't ever thought of and if I had I might have > recognized it (maybe not). It might help another 500 series driver > someday. > > We replaced a couple bladders (and found out from filling the airplane > twice parked two different directions it holds 150 gallons, not 156). Also > recalibrated the gauge with 20 gallons aboard. (twice). I'd like to think > I've got fuel management pretty well figured for this aircraft, but for > our work there is sometimes a lot of climbs and descents, but overall it's > never varied much from predicted. > > First trip out from replacing bladders was about 4.5 hours. We were at > 7500' or so W.O.T. & L.O.P. Rougher than hell as usual dropping into > 'happy valley' here back home. Pulling throttles back as we descend. Gas > (pumps) Mixture (up) Gear (down) props still to go and getting close to > turning about a four mile final (there's a mountain in the way of a > shorter final). Something ain't right. Feels an awful lot like fuel > starvation. Now we're in the real serious bumps down low, and of course > the gauge is bouncing off empty and you figure maybe you blew your math, > and the gauge was wrong all along. Definately feels like we're loosing an > engine but at this point getting knocked around like we were and in the > descent for landing, its hard to tell yet exactly which one. Beans, we > loose one engine from fuel starvation, that means we're about to lose > another and this is a piss poor place to be loosing it, just a big tree > covered hill between me and the airport. Quit descending, and went for > some height, waiting to stow one one if it asked to be and trying to tell > just what was going on. With a couple inches of throttle travel the right > engine has no juice, but we're going to make the airport long as the left > one keeps running which we're not at all sure of. > > Long story short, the past two rebuilds on the fuel servo from two > different shops we believe to be not very good. I had exactly the fuel I > thought I had. Turns out (if we understand it right) there was mechanical > wear internally to the servo that stuck wide open throttle fuel levels at > near idle throttle settings. So when power came back on the lever, the > fuel remained full tilt and essentially flooded the engine to the point of > killing it. > > Couple things: > > I wasn't ever in the trouble I thought I might be. > > Never needed to firewall it, raise the gear, flaps. If I did, there was a > good chance the right engine would have cleared itself after a bit and > recovered to develop full power in short order. > > A lot of my focus has been identifying failed engines on departure, in a > climb. Its a different critter to identify a failed engine in a descent. > Even harder if it's only partly failing going downhill in moderate > turbulence. > > This engine was probably controllable by using the mixture control, but it > would be asking a lot to have made that quick a diagnostic and remedy on > the fly during final. > > > My last trip was 5 hours and I roughly figured I'd put 120 gallons back > into the thing to fill it. It was good to see it took 118. > > I hope this posting was appropriate. I'm always interested in failure > modes, and perhaps one or two others might take something interesting from > the above and file it away..... > > Steve > > > __________ NOD32 2186 (20070413) Information __________ > > > __________ NOD32 2186 (20070413) Information __________ > > > ________________________________ Message 9 _____________________________________ Time: 03:39:43 PM PST US From: "Robert S. Randazzo" Subject: RE: Commander-List: Servo Failure John- Interesting you mention not operating the fuel pumps on descent. I've heard mixed messages as well. Would be fascinated to hear the opinion of "more experienced" commander pilots. Robert -----Original Message----- From: owner-commander-list-server@matronics.com [mailto:owner-commander-list-server@matronics.com] On Behalf Of John Vormbaum Sent: Friday, April 13, 2007 13:58 Subject: Re: Commander-List: Servo Failure --> Steve, Count yourself fortunate that you were safe the whole time. I'm sure I would NOT have recognized that failure mode at all...and it would be extra tough to diagnose in bumps, on a descent, when you think you might have to land short. One thing I do differently in my 500B is to NOT use the fuel boost pumps on approach, even though I was initially trained to. I've heard a couple of stories of not-great fuel systems where the pumps allowed an engine to flood & die when the power was pulled back. Have you checked to see if the pumps have any effect on the engines under low power settings? Just my $0.02 and probably not related to your servo issue in any way. Cheers & glad you got down safely, /John ----- Original Message ----- From: "Steve" Sent: Friday, April 13, 2007 6:58 AM Subject: Commander-List: Servo Failure > > Had an odd failure the other day I thought I would share, mainly because > it was a failure mode I hadn't ever thought of and if I had I might have > recognized it (maybe not). It might help another 500 series driver > someday. > > We replaced a couple bladders (and found out from filling the airplane > twice parked two different directions it holds 150 gallons, not 156). Also > recalibrated the gauge with 20 gallons aboard. (twice). I'd like to think > I've got fuel management pretty well figured for this aircraft, but for > our work there is sometimes a lot of climbs and descents, but overall it's > never varied much from predicted. > > First trip out from replacing bladders was about 4.5 hours. We were at > 7500' or so W.O.T. & L.O.P. Rougher than hell as usual dropping into > 'happy valley' here back home. Pulling throttles back as we descend. Gas > (pumps) Mixture (up) Gear (down) props still to go and getting close to > turning about a four mile final (there's a mountain in the way of a > shorter final). Something ain't right. Feels an awful lot like fuel > starvation. Now we're in the real serious bumps down low, and of course > the gauge is bouncing off empty and you figure maybe you blew your math, > and the gauge was wrong all along. Definately feels like we're loosing an > engine but at this point getting knocked around like we were and in the > descent for landing, its hard to tell yet exactly which one. Beans, we > loose one engine from fuel starvation, that means we're about to lose > another and this is a piss poor place to be loosing it, just a big tree > covered hill between me and the airport. Quit descending, and went for > some height, waiting to stow one one if it asked to be and trying to tell > just what was going on. With a couple inches of throttle travel the right > engine has no juice, but we're going to make the airport long as the left > one keeps running which we're not at all sure of. > > Long story short, the past two rebuilds on the fuel servo from two > different shops we believe to be not very good. I had exactly the fuel I > thought I had. Turns out (if we understand it right) there was mechanical > wear internally to the servo that stuck wide open throttle fuel levels at > near idle throttle settings. So when power came back on the lever, the > fuel remained full tilt and essentially flooded the engine to the point of > killing it. > > Couple things: > > I wasn't ever in the trouble I thought I might be. > > Never needed to firewall it, raise the gear, flaps. If I did, there was a > good chance the right engine would have cleared itself after a bit and > recovered to develop full power in short order. > > A lot of my focus has been identifying failed engines on departure, in a > climb. Its a different critter to identify a failed engine in a descent. > Even harder if it's only partly failing going downhill in moderate > turbulence. > > This engine was probably controllable by using the mixture control, but it > would be asking a lot to have made that quick a diagnostic and remedy on > the fly during final. > > > My last trip was 5 hours and I roughly figured I'd put 120 gallons back > into the thing to fill it. It was good to see it took 118. > > I hope this posting was appropriate. I'm always interested in failure > modes, and perhaps one or two others might take something interesting from > the above and file it away..... > > Steve > > > __________ NOD32 2186 (20070413) Information __________ > > > __________ NOD32 2186 (20070413) Information __________ > > > __________ NOD32 2187 (20070413) Information __________ ________________________________ Message 10 ____________________________________ Time: 04:57:23 PM PST US From: N560WM@aol.com Subject: Re: Commander-List: Sun-N-Fun I will be going to Sun and Fun, what dates you all planning on? Andy ************************************** See what's free at http://www.aol.com. ________________________________ Message 11 ____________________________________ Time: 04:59:49 PM PST US From: "Steven" Subject: Re: Commander-List: Re: Servo Failure John, I notice a slight richen-ing of the mixture at idle with the pumps on, but I am usually agressively leaned on the ground. I learned some time ago that I liked ground leaning, and if you were going to do it at all, more is better. Kind of hard to forget you're leaned during a take-off roll if pushing the handles up results in no noise. Pumps also go on pre-takeoff, although I'm carrying a little more power than arrival, but again I've not noticed anything irregular. Worst case scenario has been a hurried arrival and turn-off a runway, with pumps left on. I'll notice a lumpier idle than normal and at lower RPM. Steve Welebny Col-East, Inc. Subject: Re: Servo Failure From: John Vormbaum (john@vormbaum.com) Steve, Count yourself fortunate that you were safe the whole time. I'm sure I would NOT have recognized that failure mode at all...and it would be extra tough to diagnose in bumps, on a descent, when you think you might have to land short. One thing I do differently in my 500B is to NOT use the fuel boost pumps on approach, even though I was initially trained to. I've heard a couple of stories of not-great fuel systems where the pumps allowed an engine to flood & die when the power was pulled back. Have you checked to see if the pumps have any effect on the engines under low power settings? Just my $0.02 and probably not related to your servo issue in any way. Cheers & glad you got down safely, /John ________________________________ Message 12 ____________________________________ Time: 05:42:41 PM PST US From: "John Vormbaum" Subject: Re: Commander-List: Re: Servo Failure Yeah, I lean aggressively on the ground too....best thing in the world for the engines. I also use my boost pumps on takeoff. I have turbos too, so the pumps go on over 15,500' too. I'm just not a big fan of them on final approach. ----- Original Message ----- From: "Steven" Sent: Friday, April 13, 2007 5:01 PM Subject: Re: Commander-List: Re: Servo Failure > > John, I notice a slight richen-ing of the mixture at idle with the pumps > on, but I am usually agressively leaned on the ground. I learned some time > ago that I liked ground leaning, and if you were going to do it at all, > more is better. Kind of hard to forget you're leaned during a take-off > roll if pushing the handles up results in no noise. > > Pumps also go on pre-takeoff, although I'm carrying a little more power > than arrival, but again I've not noticed anything irregular. > > Worst case scenario has been a hurried arrival and turn-off a runway, with > pumps left on. I'll notice a lumpier idle than normal and at lower RPM. > > Steve Welebny > Col-East, Inc. > > > Subject: Re: Servo Failure > From: John Vormbaum (john@vormbaum.com) > Date: Fri Apr 13 - 1:58 PM > > Steve, > > Count yourself fortunate that you were safe the whole time. I'm sure I > would > NOT have recognized that failure mode at all...and it would be extra tough > to diagnose in bumps, on a descent, when you think you might have to land > short. > > One thing I do differently in my 500B is to NOT use the fuel boost pumps > on > approach, even though I was initially trained to. I've heard a couple of > stories of not-great fuel systems where the pumps allowed an engine to > flood > & die when the power was pulled back. Have you checked to see if the pumps > have any effect on the engines under low power settings? Just my $0.02 and > probably not related to your servo issue in any way. > > Cheers & glad you got down safely, > > /John > > > __________ NOD32 2186 (20070413) Information __________ > > > __________ NOD32 2186 (20070413) Information __________ > > > ________________________________ Message 13 ____________________________________ Time: 07:21:03 PM PST US From: "Steven" Subject: Re: Commander-List: Re: Servo Failure I'd be interested in other's opinion, but the only difference I can see between pumps on and pumps off could be a slight rise in pressure to the servo with the pumps on at idle, or a slight rise in pressure to the servo if the engine's pumps were set lower than the boost pump pressure at other RPM. At idle (no boost pump) I see the lowest fuel pressure of the engine pump. Add a couple hundred RPM and the pressure kicks up and stays put. Once out of a dead idle, I'm not sure I notice any difference in performance of the engine which stands to reason and is backed up by the EGT. Since the servo is working with a lot of differential pressures, at a dead idle the boost pump IS enough to enrichen the mixture a bit because the idle mixture was set based on the lower engine pump only pressure. I'm theorizing here that the extra boost pump fuel pressure at extreme low idle is throwing the balance of the servo's idle mixture off, but only a little and only near dead idle when set off engine pump only. I suppose the amount of 'extra' pounds of fuel pressure with a boost pump at idle could be unique to each aircraft, or maybe not at all. I'll have to play with the thing next time out, but higher than about 1200 RPM or so, maybe lower, I didn't see any difference boost on or off. Any of that sound legit? Steve W ----- Original Message ----- From: "John Vormbaum" Sent: Friday, April 13, 2007 8:42 PM Subject: Re: Commander-List: Re: Servo Failure > > Yeah, I lean aggressively on the ground too....best thing in the world for > the engines. I also use my boost pumps on takeoff. I have turbos too, so > the pumps go on over 15,500' too. I'm just not a big fan of them on final > approach. > ----- Original Message ----- > From: "Steven" > To: > Sent: Friday, April 13, 2007 5:01 PM > Subject: Re: Commander-List: Re: Servo Failure > > >> >> John, I notice a slight richen-ing of the mixture at idle with the pumps >> on, but I am usually agressively leaned on the ground. I learned some >> time ago that I liked ground leaning, and if you were going to do it at >> all, more is better. Kind of hard to forget you're leaned during a >> take-off roll if pushing the handles up results in no noise. >> >> Pumps also go on pre-takeoff, although I'm carrying a little more power >> than arrival, but again I've not noticed anything irregular. >> >> Worst case scenario has been a hurried arrival and turn-off a runway, >> with pumps left on. I'll notice a lumpier idle than normal and at lower >> RPM. >> >> Steve Welebny >> Col-East, Inc. >> >> >> >> >> Subject: Re: Servo Failure >> From: John Vormbaum (john@vormbaum.com) >> Date: Fri Apr 13 - 1:58 PM >> >> Steve, >> >> Count yourself fortunate that you were safe the whole time. I'm sure I >> would >> NOT have recognized that failure mode at all...and it would be extra >> tough >> to diagnose in bumps, on a descent, when you think you might have to land >> short. >> >> One thing I do differently in my 500B is to NOT use the fuel boost pumps >> on >> approach, even though I was initially trained to. I've heard a couple of >> stories of not-great fuel systems where the pumps allowed an engine to >> flood >> & die when the power was pulled back. Have you checked to see if the >> pumps >> have any effect on the engines under low power settings? Just my $0.02 >> and >> probably not related to your servo issue in any way. >> >> Cheers & glad you got down safely, >> >> /John >> >> >> >> >> >> __________ NOD32 2186 (20070413) Information __________ >> >> >> >> >> __________ NOD32 2186 (20070413) Information __________ >> >> >> > > > ________________________________ Message 14 ____________________________________ Time: 07:48:05 PM PST US From: "Robert S. Randazzo" Subject: RE: Commander-List: Re: Servo Failure Steven- In THEORY (which is an economist's way of saying, "this is someone elses idea but if it works you should give me credit for it") the fuel boost pumps on our commanders are there to provide positive fuel flow from the tank to the Engine Driven Pump. The EDP should meter fuel upline from there based on it's demand calibration- but the main fuel pumps are primarily to ensure you have positive fuel pressure from the tank source to the engine. So in THEORY what you describe is true... You should see no difference in performance with the fuel pump LOW or OFF- because the tank based pump isn't the one providing the performance calibration... Set to HIGH I'm guessing you will see a performance change because it appears that the HIGH setting is strictly an override mode so it likely invalidates the normal metering process (dislaimer: I'm outside my knowledge band in HIGH mode...but this performance change is what I see when setting my pumps to HIGH when testing them pre-flight.) Just my opinion... Robert S. Randazzo -----Original Message----- From: owner-commander-list-server@matronics.com [mailto:owner-commander-list-server@matronics.com] On Behalf Of Steven Sent: Friday, April 13, 2007 19:23 Subject: Re: Commander-List: Re: Servo Failure I'd be interested in other's opinion, but the only difference I can see between pumps on and pumps off could be a slight rise in pressure to the servo with the pumps on at idle, or a slight rise in pressure to the servo if the engine's pumps were set lower than the boost pump pressure at other RPM. At idle (no boost pump) I see the lowest fuel pressure of the engine pump. Add a couple hundred RPM and the pressure kicks up and stays put. Once out of a dead idle, I'm not sure I notice any difference in performance of the engine which stands to reason and is backed up by the EGT. Since the servo is working with a lot of differential pressures, at a dead idle the boost pump IS enough to enrichen the mixture a bit because the idle mixture was set based on the lower engine pump only pressure. I'm theorizing here that the extra boost pump fuel pressure at extreme low idle is throwing the balance of the servo's idle mixture off, but only a little and only near dead idle when set off engine pump only. I suppose the amount of 'extra' pounds of fuel pressure with a boost pump at idle could be unique to each aircraft, or maybe not at all. I'll have to play with the thing next time out, but higher than about 1200 RPM or so, maybe lower, I didn't see any difference boost on or off. Any of that sound legit? Steve W ----- Original Message ----- From: "John Vormbaum" Sent: Friday, April 13, 2007 8:42 PM Subject: Re: Commander-List: Re: Servo Failure > > Yeah, I lean aggressively on the ground too....best thing in the world for > the engines. I also use my boost pumps on takeoff. I have turbos too, so > the pumps go on over 15,500' too. I'm just not a big fan of them on final > approach. > ----- Original Message ----- > From: "Steven" > To: > Sent: Friday, April 13, 2007 5:01 PM > Subject: Re: Commander-List: Re: Servo Failure > > >> >> John, I notice a slight richen-ing of the mixture at idle with the pumps >> on, but I am usually agressively leaned on the ground. I learned some >> time ago that I liked ground leaning, and if you were going to do it at >> all, more is better. Kind of hard to forget you're leaned during a >> take-off roll if pushing the handles up results in no noise. >> >> Pumps also go on pre-takeoff, although I'm carrying a little more power >> than arrival, but again I've not noticed anything irregular. >> >> Worst case scenario has been a hurried arrival and turn-off a runway, >> with pumps left on. I'll notice a lumpier idle than normal and at lower >> RPM. >> >> Steve Welebny >> Col-East, Inc. >> >> >> >> >> Subject: Re: Servo Failure >> From: John Vormbaum (john@vormbaum.com) >> Date: Fri Apr 13 - 1:58 PM >> >> Steve, >> >> Count yourself fortunate that you were safe the whole time. I'm sure I >> would >> NOT have recognized that failure mode at all...and it would be extra >> tough >> to diagnose in bumps, on a descent, when you think you might have to land >> short. >> >> One thing I do differently in my 500B is to NOT use the fuel boost pumps >> on >> approach, even though I was initially trained to. I've heard a couple of >> stories of not-great fuel systems where the pumps allowed an engine to >> flood >> & die when the power was pulled back. Have you checked to see if the >> pumps >> have any effect on the engines under low power settings? Just my $0.02 >> and >> probably not related to your servo issue in any way. >> >> Cheers & glad you got down safely, >> >> /John >> >> >> >> >> >> __________ NOD32 2186 (20070413) Information __________ >> >> >> >> >> __________ NOD32 2186 (20070413) Information __________ >> >> >> > > > __________ NOD32 2187 (20070413) Information __________ ________________________________ Message 15 ____________________________________ Time: 08:42:00 PM PST US From: "John Vormbaum" Subject: Re: Commander-List: Re: Servo Failure Also Robert, keep in mind that you're flying a Continental-powered Commander, so you have low & high boost pump settings. Us Lyc-powered guys only have "on" and "off" :-). And Steve, the theories sound good. I wonder what effect the failure of an engine-driven pump would have on the fuel pressure? Is the servo self-regulating or is the EDP always the first link in the fuel pressure management process? Being just the guy who pushes the levers around in the cockpit, I'm probably light on the more esoteric points of the IO-540's systems. Perhaps it's time to rectify that. I'm going to dig around and see if I can find any articles or other documentation on boost-pump-related engine floodings on approach. I've seen ONE story along those lines related to Commanders, but I don't remember which model the author was flying. I want to assume a 500A or 685 because of all the Bonanza-specific issues I've heard about with the hi/lo boost pump settings & engine floodings, but I don't know that the Lycs are immune to similar occurence. /J ----- Original Message ----- From: "Robert S. Randazzo" Sent: Friday, April 13, 2007 7:50 PM Subject: RE: Commander-List: Re: Servo Failure > > > Steven- > > In THEORY (which is an economist's way of saying, "this is someone elses > idea but if it works you should give me credit for it") the fuel boost > pumps > on our commanders are there to provide positive fuel flow from the tank to > the Engine Driven Pump. The EDP should meter fuel upline from there based > on it's demand calibration- but the main fuel pumps are primarily to > ensure > you have positive fuel pressure from the tank source to the engine. > > So in THEORY what you describe is true... You should see no difference in > performance with the fuel pump LOW or OFF- because the tank based pump > isn't > the one providing the performance calibration... Set to HIGH I'm guessing > you will see a performance change because it appears that the HIGH setting > is strictly an override mode so it likely invalidates the normal metering > process (dislaimer: I'm outside my knowledge band in HIGH mode...but this > performance change is what I see when setting my pumps to HIGH when > testing > them pre-flight.) > > Just my opinion... > > Robert S. Randazzo > > -----Original Message----- > From: owner-commander-list-server@matronics.com > [mailto:owner-commander-list-server@matronics.com] On Behalf Of Steven > Sent: Friday, April 13, 2007 19:23 > To: commander-list@matronics.com > Subject: Re: Commander-List: Re: Servo Failure > > > I'd be interested in other's opinion, but the only difference I can see > between pumps on and pumps off could be a slight rise in pressure to the > servo with the pumps on at idle, or a slight rise in pressure to the servo > if the engine's pumps were set lower than the boost pump pressure at other > RPM. > > At idle (no boost pump) I see the lowest fuel pressure of the engine pump. > Add a couple hundred RPM and the pressure kicks up and stays put. Once out > of a dead idle, I'm not sure I notice any difference in performance of the > engine which stands to reason and is backed up by the EGT. > > Since the servo is working with a lot of differential pressures, at a dead > idle the boost pump IS enough to enrichen the mixture a bit because the > idle > mixture was set based on the lower engine pump only pressure. I'm > theorizing > here that the extra boost pump fuel pressure at extreme low idle is > throwing > the balance of the servo's idle mixture off, but only a little and only > near > dead idle when set off engine pump only. > > I suppose the amount of 'extra' pounds of fuel pressure with a boost pump > at > idle could be unique to each aircraft, or maybe not at all. I'll have to > play with the thing next time out, but higher than about 1200 RPM or so, > maybe lower, I didn't see any difference boost on or off. > > Any of that sound legit? > > Steve W > > > ----- Original Message ----- > From: "John Vormbaum" > To: > Sent: Friday, April 13, 2007 8:42 PM > Subject: Re: Commander-List: Re: Servo Failure > > >> >> Yeah, I lean aggressively on the ground too....best thing in the world >> for > >> the engines. I also use my boost pumps on takeoff. I have turbos too, so >> the pumps go on over 15,500' too. I'm just not a big fan of them on final >> approach. >> ----- Original Message ----- >> From: "Steven" >> To: >> Sent: Friday, April 13, 2007 5:01 PM >> Subject: Re: Commander-List: Re: Servo Failure >> >> >>> >>> John, I notice a slight richen-ing of the mixture at idle with the pumps >>> on, but I am usually agressively leaned on the ground. I learned some >>> time ago that I liked ground leaning, and if you were going to do it at >>> all, more is better. Kind of hard to forget you're leaned during a >>> take-off roll if pushing the handles up results in no noise. >>> >>> Pumps also go on pre-takeoff, although I'm carrying a little more power >>> than arrival, but again I've not noticed anything irregular. >>> >>> Worst case scenario has been a hurried arrival and turn-off a runway, >>> with pumps left on. I'll notice a lumpier idle than normal and at lower >>> RPM. >>> >>> Steve Welebny >>> Col-East, Inc. >>> >>> >>> >>> >>> Subject: Re: Servo Failure >>> From: John Vormbaum (john@vormbaum.com) >>> Date: Fri Apr 13 - 1:58 PM >>> >>> Steve, >>> >>> Count yourself fortunate that you were safe the whole time. I'm sure I >>> would >>> NOT have recognized that failure mode at all...and it would be extra >>> tough >>> to diagnose in bumps, on a descent, when you think you might have to >>> land >>> short. >>> >>> One thing I do differently in my 500B is to NOT use the fuel boost pumps >>> on >>> approach, even though I was initially trained to. I've heard a couple of >>> stories of not-great fuel systems where the pumps allowed an engine to >>> flood >>> & die when the power was pulled back. Have you checked to see if the >>> pumps >>> have any effect on the engines under low power settings? Just my $0.02 >>> and >>> probably not related to your servo issue in any way. >>> >>> Cheers & glad you got down safely, >>> >>> /John >>> >>> >>> >>> >>> >>> __________ NOD32 2186 (20070413) Information __________ >>> >>> >>> >>> >>> __________ NOD32 2186 (20070413) Information __________ >>> >>> >>> >> >> >> >> > > > __________ NOD32 2187 (20070413) Information __________ > > > __________ NOD32 2186 (20070413) Information __________ > > > __________ NOD32 2186 (20070413) Information __________ > > > ________________________________ Message 16 ____________________________________ Time: 11:21:07 PM PST US From: "Robert S. Randazzo" Subject: RE: Commander-List: Re: Servo Failure John- Good "Head's Up." (and good memory, too!) I wasn't aware that the 685/TCM powered commanders have different pumps. Learn something every day! Anyone familiar with the 685 have good fuel pump management techniques? I've gotten a range of opinions from folks who don't really have much direct experience with them- so I'd love to hear experienced opinions. Robert S. Randazzo -----Original Message----- From: owner-commander-list-server@matronics.com [mailto:owner-commander-list-server@matronics.com] On Behalf Of John Vormbaum Sent: Friday, April 13, 2007 20:41 Subject: Re: Commander-List: Re: Servo Failure --> Also Robert, keep in mind that you're flying a Continental-powered Commander, so you have low & high boost pump settings. Us Lyc-powered guys only have "on" and "off" :-). And Steve, the theories sound good. I wonder what effect the failure of an engine-driven pump would have on the fuel pressure? Is the servo self-regulating or is the EDP always the first link in the fuel pressure management process? Being just the guy who pushes the levers around in the cockpit, I'm probably light on the more esoteric points of the IO-540's systems. Perhaps it's time to rectify that. I'm going to dig around and see if I can find any articles or other documentation on boost-pump-related engine floodings on approach. I've seen ONE story along those lines related to Commanders, but I don't remember which model the author was flying. I want to assume a 500A or 685 because of all the Bonanza-specific issues I've heard about with the hi/lo boost pump settings & engine floodings, but I don't know that the Lycs are immune to similar occurence. /J ----- Original Message ----- From: "Robert S. Randazzo" Sent: Friday, April 13, 2007 7:50 PM Subject: RE: Commander-List: Re: Servo Failure > > > Steven- > > In THEORY (which is an economist's way of saying, "this is someone elses > idea but if it works you should give me credit for it") the fuel boost > pumps > on our commanders are there to provide positive fuel flow from the tank to > the Engine Driven Pump. The EDP should meter fuel upline from there based > on it's demand calibration- but the main fuel pumps are primarily to > ensure > you have positive fuel pressure from the tank source to the engine. > > So in THEORY what you describe is true... You should see no difference in > performance with the fuel pump LOW or OFF- because the tank based pump > isn't > the one providing the performance calibration... Set to HIGH I'm guessing > you will see a performance change because it appears that the HIGH setting > is strictly an override mode so it likely invalidates the normal metering > process (dislaimer: I'm outside my knowledge band in HIGH mode...but this > performance change is what I see when setting my pumps to HIGH when > testing > them pre-flight.) > > Just my opinion... > > Robert S. Randazzo > > -----Original Message----- > From: owner-commander-list-server@matronics.com > [mailto:owner-commander-list-server@matronics.com] On Behalf Of Steven > Sent: Friday, April 13, 2007 19:23 > To: commander-list@matronics.com > Subject: Re: Commander-List: Re: Servo Failure > > > I'd be interested in other's opinion, but the only difference I can see > between pumps on and pumps off could be a slight rise in pressure to the > servo with the pumps on at idle, or a slight rise in pressure to the servo > if the engine's pumps were set lower than the boost pump pressure at other > RPM. > > At idle (no boost pump) I see the lowest fuel pressure of the engine pump. > Add a couple hundred RPM and the pressure kicks up and stays put. Once out > of a dead idle, I'm not sure I notice any difference in performance of the > engine which stands to reason and is backed up by the EGT. > > Since the servo is working with a lot of differential pressures, at a dead > idle the boost pump IS enough to enrichen the mixture a bit because the > idle > mixture was set based on the lower engine pump only pressure. I'm > theorizing > here that the extra boost pump fuel pressure at extreme low idle is > throwing > the balance of the servo's idle mixture off, but only a little and only > near > dead idle when set off engine pump only. > > I suppose the amount of 'extra' pounds of fuel pressure with a boost pump > at > idle could be unique to each aircraft, or maybe not at all. I'll have to > play with the thing next time out, but higher than about 1200 RPM or so, > maybe lower, I didn't see any difference boost on or off. > > Any of that sound legit? > > Steve W > > > ----- Original Message ----- > From: "John Vormbaum" > To: > Sent: Friday, April 13, 2007 8:42 PM > Subject: Re: Commander-List: Re: Servo Failure > > >> >> Yeah, I lean aggressively on the ground too....best thing in the world >> for > >> the engines. I also use my boost pumps on takeoff. I have turbos too, so >> the pumps go on over 15,500' too. I'm just not a big fan of them on final >> approach. >> ----- Original Message ----- >> From: "Steven" >> To: >> Sent: Friday, April 13, 2007 5:01 PM >> Subject: Re: Commander-List: Re: Servo Failure >> >> >>> >>> John, I notice a slight richen-ing of the mixture at idle with the pumps >>> on, but I am usually agressively leaned on the ground. I learned some >>> time ago that I liked ground leaning, and if you were going to do it at >>> all, more is better. Kind of hard to forget you're leaned during a >>> take-off roll if pushing the handles up results in no noise. >>> >>> Pumps also go on pre-takeoff, although I'm carrying a little more power >>> than arrival, but again I've not noticed anything irregular. >>> >>> Worst case scenario has been a hurried arrival and turn-off a runway, >>> with pumps left on. I'll notice a lumpier idle than normal and at lower >>> RPM. >>> >>> Steve Welebny >>> Col-East, Inc. >>> >>> >>> >>> >>> Subject: Re: Servo Failure >>> From: John Vormbaum (john@vormbaum.com) >>> Date: Fri Apr 13 - 1:58 PM >>> >>> Steve, >>> >>> Count yourself fortunate that you were safe the whole time. I'm sure I >>> would >>> NOT have recognized that failure mode at all...and it would be extra >>> tough >>> to diagnose in bumps, on a descent, when you think you might have to >>> land >>> short. >>> >>> One thing I do differently in my 500B is to NOT use the fuel boost pumps >>> on >>> approach, even though I was initially trained to. I've heard a couple of >>> stories of not-great fuel systems where the pumps allowed an engine to >>> flood >>> & die when the power was pulled back. Have you checked to see if the >>> pumps >>> have any effect on the engines under low power settings? Just my $0.02 >>> and >>> probably not related to your servo issue in any way. >>> >>> Cheers & glad you got down safely, >>> >>> /John >>> >>> >>> >>> >>> >>> __________ NOD32 2186 (20070413) Information __________ >>> >>> >>> >>> >>> __________ NOD32 2186 (20070413) Information __________ >>> >>> >>> >> >> >> >> > > > __________ NOD32 2187 (20070413) Information __________ > > > __________ NOD32 2186 (20070413) Information __________ > > > __________ NOD32 2186 (20070413) Information __________ > > > __________ NOD32 2187 (20070413) Information __________ ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message commander-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Commander-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/commander-list Browse Digests http://www.matronics.com/digest/commander-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.