CS Prop When do You

[dogman]

When do you go Full High rpm When on approach?
Do you adjust your prop pitch when you are decending or in the patteren?

I have peolple do different things just wondered what most do.

 

[SkyHog]

When do you go Full High rpm When on approach?
Do you adjust your prop pitch when you are decending or in the patteren?

I have peolple do different things just wondered what most do.

I do it when I do my GUMPS, at midfield downwind. I double check it with the gear on final (Red, Blue, Green, Runway's clean!).

That way, if I'm on final, and the prop is not full, I know I missed my GUMPS, and I check again that the gear is down.

I probably do it wrong.

 

[Jim Chumley]

When do you go Full High rpm When on approach?
Do you adjust your prop pitch when you are descending or in the pattern?

I have people do different things just wondered what most do.

Dog...

Good question. I have always used GUMP or other acronym to make sure my settings were correct while on downwind. On a recent Arrow checkout, the young instructor wanted me to wait on setting the prop to full forward until short final. In my gut, I resisted the instruction. I feel that barring an unfortunate situation where I might cause engine/prop damage, i want the housekeeping items taken care of before short final.

I will be interested in the learned responses you get from this post.

Jim

 

[BCMCF]

I start pushing the prop forward when I need to slow the plane down for the approach. Usually I do it on downwind or just outside the outer marker. By the time I've joined the glideslope, the prop is full forward, and it's just about there on base for a visual.
My plane doesn't bleed off speed too well while in a desent without screwing in the prop.

 

[Let'sgoflying!]

I don't do it til the power is low enough to put the prop outside the governable range.
I can get everything forward in a jif should I need it in an emergency, and there must be some slight adverse effect to wind the prop up on every landing.

 

[Ryan Ferguson]

When do you go Full High rpm When on approach?
Do you adjust your prop pitch when you are decending or in the patteren?

I have peolple do different things just wondered what most do.

I'd suggest, in the interest of kindness to your airport neighbors, one of the following two methods:

1) Don't adjust the prop to low pitch/high RPM until after you land.
2) On the approach, wait until you're out of the governor's range before bringing the props up.

#1 means that, yes, you'll need to remember to bring the props back to high RPM if you initiate a go-around. I think a pilot of average skill should be able to do this without a problem.

Personally, I rarely bring the props forward prior to the rollout. I also bring the props back to 2500RPM (without reducing manifold pressure - read John Deakin's columns at AVWeb about that topic) a few hundred feet up, on climbout. Makes for a much lower noise signature.

Best,

Ryan

 

[Jim Chumley]

I don't do it til the power is low enough to put the prop outside the governable range.
I can get everything forward in a jif should I need it in an emergency, and there must be some slight adverse effect to wind the prop up on every landing.

Dave, your view expresses the first hint of logic behind the practice. I remain unconvinced, however, that a delay (in the preparation for landing process cited by Dog) of pushing the prop control forward has any real benefit, mechanically or from a safety standpoint.

But, if it's your airplane, you can do it - it's OK with me. And if I borrow your airplane, I'll do it your way. However, I still haven't heard a convincing argument against setting the prop during the downwind segment of the landing process.

Jim

 

[sshekels]

I was always tought that short final was the place to set it. The reasoning was "being nice to the neighbors"

S.

 

[Dave Siciliano]

This is another issue that has been bantered around a lot where there is more than one way to safely deal with matters.

I can certainly see where newer pilots should have a set procedure and should have everything done early, so, if a go-around is required, everything is set up.

You will find that bringing the mixtures, and props forward, immediately cools cylinder temps and in TC aircraft, we let cylinder head temperature management govern a lot of things. So, my procedure is a little different.

On an instrument approach, one philosophy is to have everything in a landing configuration at the FAF or ILS intercept and fly a stabilized approach. Other folks don't put in flaps until the field is made. The more important thing, seems to be to do things the same way every time. On the P-Baron, we use approach flaps. So, at FAF, I would be at 2500 rpm, leave the mixtures where they were in cruise, 23" of MP and approach flaps. When I break out, I would put in full flaps and land.



My go around procedure is Mixture, prop, throttle, positive rate, then clean up (gear and flaps).



VFR I leave the mixture and proper where they were in cruise (normally 2200 rpm, LOP on mixtures, throttle to 23" and approach flaps. Go around procedure is the same as above.

Best,

Dave
Baron 322KS

 

[Jim Chumley]

I probably do it wrong.

Nick, that makes two of us. I think I have learned something here this morning. The noise issue has a large bearing on the practice of leaving the prop(s) alone until landing or short final.

Thank you Ryan, for being most informative. I am converted.

Jim

 

[azure]

I'd suggest, in the interest of kindness to your airport neighbors, one of the following two methods:

1) Don't adjust the prop to low pitch/high RPM until after you land.
2) On the approach, wait until you're out of the governor's range before bringing the props up.

#1 means that, yes, you'll need to remember to bring the props back to high RPM if you initiate a go-around. I think a pilot of average skill should be able to do this without a problem.

After nearly forgetting a couple of times, I've settled on method #2. I usually do two GUMPS checks, the first on downwind after bringing the gear down but before reducing MP. At this point I verify fuel selector, gear down, adjust the mixture for go around (full rich except at high DA), verify landing light on, and touch the prop control to remind myself to get it on the next GUMP. After reducing MP out of governor range (usually abeam touchdown zone), on the second GUMPS I bring the prop forward.

Personally, I rarely bring the props forward prior to the rollout. I also bring the props back to 2500RPM (without reducing manifold pressure - read John Deakin's columns at AVWeb about that topic) a few hundred feet up, on climbout. Makes for a much lower noise signature.

Why without reducing MP? I was taught to pull out the MP, prop, and mixture controls (in that order) to bring the MP, RPM, and fuel flow gauges down to top of green on climbout.

Liz

 

[wsuffa]

This is another issue that has been bantered around a lot where there is more than one way to safely deal with matters.

I can certainly see where newer pilots should have a set procedure and should have everything done early, so, if a go-around is required, everything is set up.

You will find that bringing the mixtures, and props forward, immediately cools cylinder temps and in TC aircraft, we let cylinder head temperature management govern a lot of things. So, my procedure is a little different.

On an instrument approach, one philosophy is to have everything in a landing configuration at the FAF or ILS intercept and fly a stabilized approach. Other folks don't put in flaps until the field is made. The more important thing, seems to be to do things the same way every time. On the P-Baron, we use approach flaps. So, at FAF, I would be at 2500 rpm, leave the mixtures where they were in cruize, 23" of MP and approach flaps. When I break out, I would put in full flaps and land.



My go around procedure is Mixture, prop, throttle, positive rate, then clean up (gear and flaps).



VFR I leave the mixture and proper where they were in cruise (normally 2200 rpm, LOP on mixtures, throttle to 23" and approach flaps. Go around procedure is the same as above.

Best,

Dave
Baron 322KS

I do pretty much what Dave does, except I leave flaps out until the field is made (exception: on a slam-dunk approach I may use 10-20 degrees of flaps first to avoid exceeding the max-gear-down speed on my plane).

Prop forward slightly increases drag and helps manage engine temperatures on the descent.

 

[Ed Guthrie]

Dave, your view expresses the first hint of logic behind the practice. I remain unconvinced, however, that a delay (in the preparation for landing process cited by Dog) of pushing the prop control forward has any real benefit, mechanically or from a safety standpoint.

Wander out under the mid-field downwind position at your favorite airport, pull over on the side of the road and listen to the next 1/2-dozen or so planes as they pass overhead. Absolute certainty that you'll hear a goodly portion of the C/S prop pilots slam the prop control full forward at mid-field downwind resulting in a huge prop speed surge/over speed.

But, if it's your airplane, you can do it - it's OK with me. And if I borrow your airplane, I'll do it your way. However, I still haven't heard a convincing argument against setting the prop during the downwind segment of the landing process.

If you pay the prop & engine maintenance bills you tend to develop Dave's method (prop up gently after power is reduced so far that the prop is what I call "off the governor").

 

[Greg Bockelman]

I don't do it til the power is low enough to put the prop outside the governable range.

Ditto what Dave said.

 

[poadeleted20]

I'm with Dave -- I hit the props as part of my final "commit to land" right-to-left checks (flaps-full, mixtures-a/r, props-forward, throttles-set, gear-checked down) after turning final in the traffic pattern or when leaving DH/MDA on an instrument approach. Before that, they remain at the approach (typically 2500 RPM) setting. Note that mixture doesn't always go full forward, say, at Rock Springs WY on a warm day.

 

[dogman]

I have been taught to the same as most of you GUMPS on final, prop full in, Mixture set, and ready for go around. But I am flying the Ch. Six now and seems to not want to slow down. So I have been playing with it on down wind or long final to increase rpm seems to help slow down and start descent.

Usually down wind 100mph TPA 17MP. Prop still at cruise setting lets say 2300rpm. Then abeam numbers 15MP 1 notch flap the darn thing just keeps flying and very slow descent. I like to fly a fairly tight patteren so if I loose power I have hope of making the field. So I have tried increasing prop to say 2500rpm on DWind and seams to slow down and start a better rate of descent. I also felt like I had better speed and rate of descent management. Is there anything wrong with this??

Or should I just leave the prop alone and abeam decrease MP more.????

 

[Bob Bement]

I like to leave the prop at cruise until on short final and then put it and the carb heat all the way in. If I have to make a go around I'm ready for it. This has seemed to work for me for about ten years in my 182. So I guess i will stay with it.

 

[sere]

I would also add that with the Arrow Jim to change it to GUMPCS. The C is cowl and the S is seat belt secure. I also do two GUMPCS like others here. We need to go fly together soon Jim C.

Larry

 

[Ryan Ferguson]

Why without reducing MP? I was taught to pull out the MP, prop, and mixture controls (in that order) to bring the MP, RPM, and fuel flow gauges down to top of green on climbout.

This is a topic that can spark a 'religious' debate, so I'll try to present the information simply and with as little bias as possible.

In my experience as a flight instructor, aircraft owner, and ferry pilot, most folks, through no fault of their own, are 'taught' poorly when it comes piston powerplant management. There are so many ways to move all those multicolored knobs/levers, and nearly all combinations work - they don't have any immediate noticable consequence to the pilot. Poor powerplant management is largely evident in a reduction of engine longevity and increase in mx bills in the long run. As such, renter pilots may never be aware of the cause and effect nature of their actions, i.e. when the levers/knobs are moved to the wrong positions at the wrong times. After all, they're not responsible for the maintenance and overhaul bills (and maybe some just don't care.) And CFIs may not know or care either; most don't own airplanes, and most were taught by those who came before, who might also not have actually ingested any data on the subject. But I guarantee all aircraft owners do care, and in my view owners are the ones who take it upon themselves to learn more about managing piston engines. It is surely a more complicated and technical process than managing any turboprop/shaft or turbofan engine I've ever flown.

The first caveat I have to throw into the mix, prior to going any further, is that every engine's different. What I'm advising applies to 'most' normally aspirated Continental and Lycoming engines used in typical GA airplane installations. However, there are exceptions.

The second caveat with which you must be aware is that the AFM or POH may not always directly agree with some of these 'facts.' Most engines on the market today, particularly brand A & B engines, were certified decades ago. Guidance on power settings for takeoff climb, cruise, etc. is sometimes vague and murky; other times it's directly 'wrong;' and sometimes it's about it right. That's just the way it is, and the manufacturers aren't going to reverse course after all this time and endorse new ways to operate their engines, despite test-stand evidence which clearly indicates better ways to do things. That could start a legal liability nightmare; it'll never happen.

With all that outta the way...

There's this old "oversquare" myth that's still alive today, which suggests that operating with the manifold pressure at a higher " of Hg. setting than RPM can damage the engine. I.e., don't use 28" and 2500 RPM, use "25 squared." Ugh, just the mention of it makes me feel grouchy. Almost any POH will include power settings that include "oversquare" combinations of MAP and RPM. This is the first data you should show to your CFI if he/she tells you to reduce manifold pressure on the climbout to some setting lower than fully open. (If he/she can show you an actual limitation on METO - maximum except takeoff power - accept that.)

So we've gotten this idea that it's somehow easier on the engine to reduce MAP during initial climbout. That's actually not the case for most naturally-aspirated engines. One of the most important tenets to understand about piston powerplant management is that internal temperatures and pressures are what's important, not necessarily the power setting. Of course, temps and pressures are largely derived from power settings, so they're important. But it's the results, not the cause, that we're most interested in.

Problem is, powering back in the climb is not good for our theoretical generic normally-aspirated engine. These powerplants are designed to run "extra rich" with wide open throttle settings. By bringing the throttle all the way forward, you allow this to occur, usually via a second fuel inlet which increases fuel flow. The reason for this is twofold; first, you provide more fuel to the engine, which via slower compression events, leads to cooler CHTs and lower internal pressures (particularly important during climbout due to the higher AOA and lower indicated airspeeds involved.) Second, and probably more importantly, you prevent detonation, the number one enemy of all engines at high power settings (for emphasis, see the Reno Air Races.)

In other words, when you bring MAP back but leave the RPMs up at 2700 during takeoff, you're taking air and fuel away from an engine thirsty for both. You're defeating the fuel-enrichening feature mentioned above, and you're increasing temps and pressures inside the engine. If you have a properly calibrated digital engine monitor, you can verify this for yourself.

Reducing RPM from 2700 to 2500RPM only costs 5-15HP in most GA engines and tremendously reduces noise. Won't do all that much for temps and pressures.

Another excellent Deakin tip is to note EGT right at takeoff and adjust mixture to keep it there during the climb. You CAN'T hurt the engine this way. So I've always taught that after rotation, pull the props back to 2500RPM at 500 feet or so, and just keep tweaking the mixtures back to match takeoff EGT. When you reach 75% power (usually around 23 or 24") and dropping you can start thinking about tweaking them back further.

So, in normally-aspirated piston airpolanes, I leave throttles fully forward all the way to cruise altitude. There's no better way to do it, in terms of engine care and longevity. Going partial power just doesn't do anything good at all for your hot little bucket of bolts trying to thrash itself apart with every stroke. Give it all the air and fuel it wants in the climb, and your repair bills will go down. For heaven's sake, the WORST thing you can do is reduce MAP AND fuel-air mixture during the initial climb. Don't do that. (This is assuming near sea-level ambient pressures and standard or higher temps. If you're taking off out of a high elevation airport, you may not be able to hurt the engine regardless of how you feed the fuel and air - below 65% power, it's mostly a matter of not running too rich, which can foul plugs and cause some other relatively minor, nuisance related problems.)

The real question at the end of the day is, "Why do we learn to do it the wrong way?" When I first starting flying airplanes with constant speed props, I was told to reduce power to 25-25 on the climbout. No one knew why, but that's just what we did. When the size of my wallet started depending on the health of my two IO-320s, I started looking into the subject a bit more. Glad I did... these engines have been trouble-free for years with compressions in the high 70s. (Of course, the fact that they're products of Charlie Melot's shop in Zephyr Hills doesn't hurt matters either.)

-Ryan

 

[John J]

I also go with Dave's suggestion. I go through the GUMPS as I enter the airport area either IFR or VFR. I do another series of "Three in the Green" as I get close to the end of the runway. I then "ease the prop control in" for I think about all those counter weights on the crankshaft. The final is flown at 17 to 17.5 inches and the RPM stays behind the govenor at 2300. It works out well.

John

 

[mmthomas]

During my instrument training, my instructor advised me not to push the prop forward at all during the approach--not even when going missed. His theory was that in a missed approach the plane will climb perfectly well at 500 fpm with the prop set at cruise RPM and with the plane at approach speed. This worked fine during my training, but afterwards I reverted to pusing the prop forward as part of my pre-landing checklist, largely because that's what my 1967 Cessna 182 owner's manual recommends. Now, however, I'm wondering whether I should follow his advice, be kinder to my neighbors, and reduce my maintenance costs .

 

[gismo]

I'd suggest, in the interest of kindness to your airport neighbors, one of the following two methods:

1) Don't adjust the prop to low pitch/high RPM until after you land.
2) On the approach, wait until you're out of the governor's range before bringing the props up.

#1 means that, yes, you'll need to remember to bring the props back to high RPM if you initiate a go-around. I think a pilot of average skill should be able to do this without a problem.

Personally, I rarely bring the props forward prior to the rollout. I also bring the props back to 2500RPM (without reducing manifold pressure - read John Deakin's columns at AVWeb about that topic) a few hundred feet up, on climbout. Makes for a much lower noise signature.

Best,

Ryan

I agree with all of that, especially in a twin. Rather than trying to fuss with the prop (and mixture) controls between 300 AGL and touchdown, I've simply committed to pushing everything forward on any aborted landing (and any takeoff for that matter). I don't like to run the engine RPM up on approach, and until I reach 200-300 AGL I'm going too fast (blue line) with too little flaps (approach) to close the throttles far enough to hit the fine pitch stops. I also found that my engines are happier if I don't go full rich in the pattern so I typically land with the props at cruise RPM and the mixtures somewhat lean of full rich. I use the extra time to check the gear and runway traffic on short final.

 

[gismo]

I like to leave the prop at cruise until on short final and then put it and the carb heat all the way in. If I have to make a go around I'm ready for it. This has seemed to work for me for about ten years in my 182. So I guess i will stay with it.

Personally, I'd leave the carb heat on until I either landed or had reached full power on an abort. On a humid day, you can ice up a 182 carb awfully quickly and the closed or nearly closed throttle of short final/flare is the worst case scenario for ice.

 

[gismo]

The real question at the end of the day is, "Why do we learn to do it the wrong way?" When I first starting flying airplanes with constant speed props, I was told to reduce power to 25-25 on the climbout. No one knew why, but that's just what we did. When the size of my wallet started depending on the health of my two IO-320s, I started looking into the subject a bit more. Glad I did... these engines have been trouble-free for years with compressions in the high 70s. (Of course, the fact that they're products of Charlie Melot's shop in Zephyr Hills doesn't hurt matters either.)

My NSHO is that new pilots are taught this way (pull the throttle and prop to 25^2 etc) is that because it's easy to teach, seems to make sense, and mostly because that's what the CFI was taught by his CFI. All too few instructors seem to take the time to learn the details of proper engine management (at least while they're still teaching) and thus pass on all sorts of nonsense through many generations of CFI's and students.

When most CFI's strive to learn their trade as well as you obviously have Ryan, this problem may become a thing of the past. I'm not holding my breath though.

 

[Ryan Ferguson]

My NSHO is that new pilots are taught this way (pull the throttle and prop to 25^2 etc) is that because it's easy to teach, seems to make sense, and mostly because that's what the CFI was taught by his CFI. All too few instructors seem to take the time to learn the details of proper engine management (at least while they're still teaching) and thus pass on all sorts of nonsense through many generations of CFI's and students.

When most CFI's strive to learn their trade as well as you obviously have Ryan, this problem may become a thing of the past. I'm not holding my breath though.

Aww, coming from you that is a REAL compliment. I'm honored.

Lance, speaking of good CFIs, you've always impressed me (and others) with your aviation knowledge and humility. You'd make a great flight instructor! Have you ever thought about taking the plunge? You could do some real good out there.

 

[Skip Miller]

My NSHO is that new pilots are taught this way (pull the throttle and prop to 25^2 etc) is that because it's easy to teach, seems to make sense, and mostly because that's what the CFI was taught by his CFI. All too few instructors seem to take the time to learn the details of proper engine management (at least while they're still teaching) and thus pass on all sorts of nonsense through many generations of CFI's and students.

I discount none of the above but also add that it is a safe setting for relatively high power on almost any aircraft with a c/s prop. Start off learning the generics and then fine tune the specifics later. I agree that not many bother with the fine tuning at a later time though.

TD has opined that proper rpm/mp settings were more than a good idea on the large radial engines. I'll bet that is the origin of the lore.

-Skip

 

[gismo]

Aww, coming from you that is a REAL compliment. I'm honored.

Lance, speaking of good CFIs, you've always impressed me (and others) with your aviation knowledge and humility. You'd make a great flight instructor! Have you ever thought about taking the plunge? You could do some real good out there.

I probably will someday when I have more time. Right now i couldn't put in enough time to make it work. I do like to teach though so maybe when I retire in another 5-10 years?

 

[Dave Siciliano]

What a wonderful observation Ryan. And very deservedly so for Lance.

Might I also add he would be a wonderful advanced instructor!! Knows the fundamentels real well, but also stands out on advanced aircraft and systems!!

Best,

Dave

 

[jdwatson]

When do you go Full High rpm When on approach?
Do you adjust your prop pitch when you are decending or in the patteren?

I have peolple do different things just wondered what most do.

I have 3 GUMPS checks for the traffic pattern. Depending on how fast I slow down, I usually get the prop full on my base leg GUMP by then the prop governor is no longer controlling the prop. That way I avoid making too much noise on the ground.

 

[poadeleted20]

During my instrument training, my instructor advised me not to push the prop forward at all during the approach--not even when going missed. His theory was that in a missed approach the plane will climb perfectly well at 500 fpm with the prop set at cruise RPM and with the plane at approach speed.

In most cases this is true as long as you control your throttle hand so you don't overboost the engine (bigger problem with turbo'd engines than normally aspirated). However, the best idea is to read the book and do what it says. There can be a number of reasons to either leave the prop alone or to push it up, and you want to do what's best for the particular plane you're flying -- there is no single correct answer for all types.

 

[spiderweb]

Thanks, Ron--that is what I was looking for.

 

[bbchien]

I agree Lance would make an excellent CFI...but his accountant would probalby have a field day yelling at him, too.

It has been quite a while since I've had to adjust power on final. My props go to full forward at MDA whether IFR or VFR. It's not better or worse than any other way...just the way I do it. We're not carrying much power at that moment, unless it's a miss in real IMC...at which point my hide becomes more important than my machinery.