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#11
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Emergency Procedures
In article TKdug.77158$ZW3.34119@dukeread04,
"Jim Macklin" wrote: If the engine is turning, it has oil pressure. Yes, but is there not a minimum RPM below which the governor has no effect? |
#12
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Emergency Procedures
That's true. Also, knowing that the prop and governor are
using engine oil, apply that if you have a zero engine oil pressure indication, if the prop work-so is the engine oil pump and there is some oil pressure and volume. Still, a precautionary landing is advised, but don't panic and cause more problems with a shutdown or off airport landing. In a single-engine airplane, the prop will go to low pitch, high rpm and operate as a fixed pitch if you do not have pressurized oil from the governor and it won't be supplied unless the engine oil pump is working. In a multiengine airplane, the first indicator of a failure may be the affected prop feathering. If my aunt had been born with different plumbing, she'd have been my uncle. -- James H. Macklin ATP,CFI,A&P "Roy Smith" wrote in message ... | "Jim Macklin" wrote: | If the engine is turning, it has oil pressure. | | Only if it has oil. | | Still, I teach pulling the prop all the way back. It may work, it may not, | but it sure can't hurt. |
#13
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Emergency Procedures
When the prop is on the high or low pitch stops, which
should be indicated by the green arc on the tach and with power applied. With a single engine, doing a run-up at say 2000 rpm, the governor can reduce rpm to perhaps 1700 rpm. The prop control is full forward and the prop is on the low pitch stop as you begin the run-up. Pulling the prop control back moves the prop towards the high pitch stops. Most pilots seem to think cycling the prop is just to circulate fresh warm oil. Give the system a moment to have the rpm stabilize to see what is happening. On a multiengine run-up, doing the feather check, pull the prop back to the feather dent and the prop should stabilize at the bottom of the green arc, probably about 2000 rpm on a piston engine. Let it run there a moment to see that it does get to the full governed range and does not feather until you pull the control through the detent, then it should begin to feather. I've seen many airplane misrigged, that would feather before the detent or would not reach the minimum governor range even though a typical quick test would be seen as "normal" by many rated pilots. -- James H. Macklin ATP,CFI,A&P "john smith" wrote in message ... | In article TKdug.77158$ZW3.34119@dukeread04, | "Jim Macklin" wrote: | | If the engine is turning, it has oil pressure. | | Yes, but is there not a minimum RPM below which the governor has no | effect? |
#14
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Emergency Procedures
On Sat, 15 Jul 2006 14:55:09 -0600, Tim Auckland wrote:
It's a technique I was taught during my commercial license training as a way of adjusting drag when doing the "180-degree power-off precision landing". My guess is that it's not included in emergency checklists beacuse once the engine stops, you loose oil pressure, and the propellor will go to the fine-pitch position anyway on a single-engine plane. Which makes virtually no difference from the coarse setting to stopped as far as drag. It's not something you can rely on in an emergency. Yes it is if the prop is wind milling. If the prop stops it'll have about the same drag or maybe a bit less than it did in corase pitch while wind milling. It's one of those; nothing to lose and a bit to gain by doing. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com Current return address does not work...have to fix it. Tim. On Sat, 15 Jul 2006 14:06:18 -0500, Mitty wrote: I was checking out in a Civil Air Patrol 182T the other day and the check airman pulled the power on me. No big deal, but then he demonstrated how the glide improved when the propeller was pulled to low RPM. No one had ever showed that to me before. Question is: In retrospect it seems obvious that there will be less resistance when the prop is closer to a feathered position. Buy why don't I see this as part of emergency checklists for airplanes with constant speed props? What am I missing here? Roger |
#15
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Emergency Procedures
john smith wrote:
In article TKdug.77158$ZW3.34119@dukeread04, "Jim Macklin" wrote: If the engine is turning, it has oil pressure. Yes, but is there not a minimum RPM below which the governor has no effect? Yeah, but at best glide (provided the engine hasn't siezed up) it will windmill way above this point at best-glide speeds. |
#16
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Emergency Procedures
Jim Macklin wrote:
Pulling the prop control back moves the prop towards the high pitch stops. Most pilots seem to think cycling the prop is just to circulate fresh warm oil. Give the system a moment to have the rpm stabilize to see what is happening. Leave it there a moment? Hmmm, when I transitioned to the Bonanza, my first constant speed prop aircraft, I was told by the very experienced CFI not to let the RPMS drop too much during this pre-takeoff item or it would place a high load on the engine (I believe his analogy was like shifting a car into 4th gear while driving at 25 miles per hour). Not true? -- Peter |
#17
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Emergency Procedures
In article ,
"Peter R." wrote: Leave it there a moment? Hmmm, when I transitioned to the Bonanza, my first constant speed prop aircraft, I was told by the very experienced CFI not to let the RPMS drop too much during this pre-takeoff item or it would place a high load on the engine (I believe his analogy was like shifting a car into 4th gear while driving at 25 miles per hour). At the power setting for runup I can't see it being a problem. On the radials on the B-17 and B-24 part of the check was to bring the prop controls to the low RPM position to check the low RPM pitch stop. We wanted to see the RPM hold at 1200. |
#18
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Emergency Procedures
If the MAP is around 20 inches, you can run the prop back to
minimum rpm without having any problem. On a multiengine aircraft, you can cruise at minimum governed rpm and high MAP [within the limits shown in the POH] without harm to the engine. You don't do a feather check or a prop check at full throttle at sea level. I'm not talking about slamming the control full range, but taking a few seconds so dynamic forces are not excessive. I don't have a Bonanza manual handy today, but the P58 Baron has a tach range of 2000-2700, run-up at 2000 rpm [less than full throttle] and the feather check at 1500 rpm. The multiengine aircraft can run at the 2000 rpm setting indefinitely, as long as the limitations on the MAP are not exceeded. The P58 Baron shows a recommended cruise setting of 30 inches and 2200 rpm. At 2000 rpm the engine won't be as smooth. In the limitations or cruise section of the POH, there is usually a chart that shows permissible rpm vs. MAP for continuous operation. You don't need to rush these tests and you don't do them at full power. -- James H. Macklin ATP,CFI,A&P "Peter R." wrote in message news | Jim Macklin wrote: | | Pulling the prop | control back moves the prop towards the high pitch stops. | Most pilots seem to think cycling the prop is just to | circulate fresh warm oil. Give the system a moment to have | the rpm stabilize to see what is happening. | | Leave it there a moment? Hmmm, when I transitioned to the Bonanza, my | first constant speed prop aircraft, I was told by the very experienced CFI | not to let the RPMS drop too much during this pre-takeoff item or it would | place a high load on the engine (I believe his analogy was like shifting a | car into 4th gear while driving at 25 miles per hour). | | Not true? | | -- | Peter |
#19
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Emergency Procedures
Peter R. wrote:
Leave it there a moment? Hmmm, when I transitioned to the Bonanza, my first constant speed prop aircraft, I was told by the very experienced CFI not to let the RPMS drop too much during this pre-takeoff item or it would place a high load on the engine (I believe his analogy was like shifting a car into 4th gear while driving at 25 miles per hour). Not true? There's no advantage to letting it hang at low RPM's. What you DO want to do is make sure it comes all the way back up to the same "initial" RPM you started the exercise with. |
#20
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Emergency Procedures
Right on. In the big radials, the feathering was done with
a feathering button that powered a feather pump, so there was no issue of feathering with the prop control. But in the light twin, the prop lever control rpm and when it is moved through a detent, the governor dumps the oil and the prop feathers. But you can set the engine to an idle of about 1000-1200 rpm and then feather the engine and let the prop go all the way. But at idle the engine won't feather because the stops will prevent the prop from feathering. You do a feather check at 1500 rpm because that assures the stops are retracted with enough rpm to allow the blades to get into the feather range. You can run on the detent ass long as you wish, but unless you want the engine to shake, shudder and need to have the prop unfeather during the start attempt, don't let the rpm drop below 1,000 rpm during the feather test. If you have unfeathering accumulators it is a one shot deal to get started...with the prop control still in feather, prime and engage then starter, when you start to get a little oil pressure and the engine is firing, move the prop control full forward and hope you have enough oil pressure from the governor to move the prop blades out of feather. This is an emergency technique, much better to have a mechanic use blade boards to manual turn the blades out of feather. -- James H. Macklin ATP,CFI,A&P "Dale" wrote in message ... | In article , | "Peter R." wrote: | | | | Leave it there a moment? Hmmm, when I transitioned to the Bonanza, my | first constant speed prop aircraft, I was told by the very experienced CFI | not to let the RPMS drop too much during this pre-takeoff item or it would | place a high load on the engine (I believe his analogy was like shifting a | car into 4th gear while driving at 25 miles per hour). | | | At the power setting for runup I can't see it being a problem. | | On the radials on the B-17 and B-24 part of the check was to bring the | prop controls to the low RPM position to check the low RPM pitch stop. | We wanted to see the RPM hold at 1200. |
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