Yellow Arc RPM

[201er]

"Caution: avoid continuous operation between 1500 and 1950 RPM with power settings below 15" Hg manifold pressure."

This is what it says in the POH and there is a yellow arc reminder on the RPM gauge. If this isn't enough, the plane rumbles to remind me if I venture into this range. So for now, I've been staying away entirely from operating in that range but what I've found is that it's right where I want to be during landing approaches. If I could hold the power at roughly 1700RPM during my pattern, I could make the whole thing go without reducing throttle till final. Since I'm not sure what "continous operation" is supposed to mean I've enitrely avoided throttling to the point where I get 1500-1950RPM for now until I can figure it out. What this forces me to do is to keep the power in to develop 2000RPM for the first part of descent in pattern and then I go directly to full idle (cause anything more puts me in the yellow). The trouble is that at idle it starts sinking again too much and I go back to 2000. If I could just use something in between it would make my life a whole lot easier.

Am I over thinking this? Do you use 1500-1950 RPM in the pattern? What is the problem with this kind of operation anyway? Is there a good solution?

PS sorry for so many questions all at once. I'm just discovering so much all at once because I've been doing a lot of flying this weekend.

[jetdriven]

you are over thinking the problem.  It takes ~15" MP and in our J, the prop is still at 2200 RPM when descending for landing.  Use the power it takes to maintain a 3:1 glide ratio.  It should be above that yellow arc.

[Cruiser]

This is from memory so the actual numbers may be slightly different...........

Normally reduce the power (with the RPM and mixture full forward) to 17" when descending to enter the pattern at an uncontrolled airport. This brings the RPM to around 2200,

At pattern altitude, downwind for landing, hold the altitude until the speed drops to extend the gear. When the gear extends it should slow to around 97kts and you will trim up (the nose wants to drop). You can reduce the power to 15". Let the plane settle into a stable descent, adding flaps (take off position) will require additional trim up and slow to about 90 kts. Full flaps requires additonal trim and slows to about 80kts. Once the plane is stabilized, additional trim up and or power adjustments to final speed and descent rate on short final.

IF you set the power at around 17" this will keep the RPM above the yellow arc until you reduce power to land.

[201er]

Well that's mainly the point I'm asking about, the "reduce power to land" stage. On final, going full idle doesn't give me as good of a descent control. 2000RPM+ doesn't give enough descent. It feels like just right would be somewhere in the yellow arc. So do you guys go from 2000+ to idle directly or do you fly some of the landing descent (not from altitude, just talking in the pattern) in the yellow range?

[Cruiser]

On short final put the power where ever you need it.

The yellow arc is for continuous operations, I don't think a minute or two on short final qualifies.

[201er]

I interpreted continous operation as anything but trasnitioning through that RPM. So for instance throttling back from 2000 to idle is transient whereas holding it for a few minutes in yellow arc is continous?

I'm still unsure of WHY it's bad to be there so it's difficult for me to decide if it's ok or not to operate in yellow arc and for how long.

[Shadrach]

It's likely a "bad idea" to be there because of engine/prop harmonics at that RPM and power level. Does it feel like it's shaking? I'd not over think it, the engine is not going to come off during a few minutes of pattern work, however, I'd not run it there for extended periods. YMMV...

I have a different "avoid continuos" on my engine/prop combo and I occasionally venture into it while in the pattern, but never "continuously"...

[Hank]

When I'm in the pattern at an untowered field [like home], I put the prop & mixture full forward, slow to 90 mph, add T/O flaps, drop gear, and put the throttle wherever it needs to be to maintain the proper glide. I control speed and glide with the yoke and throttle, but don't really look at the gages way over on the right panel. Airspeed is in front of me, and I look mostly out the windshield or at A/S. Seems like 15" or so will hold 90 mph, TO flaps and a descent. Time is usually pretty short--90 seconds? Operation there is hardly "continuous" and unlikely to do anything; my field is short [3000'], so I'm can't power up to keep RPMs high if I want to actually land the plane.

[RJBrown]

Prop should be full forward while landing. Do not use the prop control in the pattern. Engine power is controlled in relation to manifold pressure. I fly 15" manifold pressure gear up level flight. Drop the gear, flaps to take off and get proper decent. Minor throttle adjustment to maintain glideslope.

Continuous operations is just that. The time from downwind to touchdown is too short to be considered continuous. 

[201er]

Huh? Throttle directly controls RPM in low power settings like during landing. Prop is full forward anyway, but there's not enough power to reach max RPM.

[RJBrown]

"Huh? Throttle directly controls RPM in low power settings like during landing. Prop is full forward anyway, but there's not enough power to reach max RPM."

That statement reflect power setting as done in a fixed pitch airplane. Setting power is done by using the MP gauge not the tach. RPM can change by changing attitude even without a power change. At 15" nose over and the tach goes up pull back and the RPM will drop. MP will stay constant. Power will stay constant. RPM reading is MEANINGLESS.

Throttle position or power level reflects in MP you don't look at the tach you look at the MP gauge. MP gauge is the power measurement gauge. At low power the RPM will be less than at high power but the number is meaningless. The only time you set power settings by the tach is if you are flying a trainer of some sort that does not have a constant speed prop. Once you fly a real plane you use the MP gauge to set throttle position. You are mixing your old 172 training where it is meaningless.

 Try this: trim for say 90 knots level flight. It will be about 15" of MP. Your trim will be at about the take off position. That will be your stabilized approach speed. when you drop the gear without any other adjustment you won't change your speed but you with initiate your decent.

Where you do this depends on what type of approach you are flying. Flying an ILS at 90 knots you will be straight and level as you get to the glideslope. Once you reach the glideslope, from below, you can drop the gear and then follow the glideslope down without any other change. As you get closer to landing you can roll in flaps. the flaps will slow you but allow you to stay on glideslope without reducing power. Set up right you will be ready to land or go miss with out any re trimming.

In a pattern approach I fly downwind straight and level 90 knots 15" MP. Even with the end of the runway I drop the gear and start down.  Roll in take off flaps slows you a bit. Over the fence is 80 knots 500FPM decent and right on glideslope. At that point you are ready for both a landing and a missed approach. To land you reduce power and flare. To go around you simply push in the power. You are already trimmed for it. Once a positive climb is achieved bring up the gear. Once at pattern altitude reduce to the same 15" MP and you are going around the pattern at the same 90 knots.

Never looked at the tach other than to verify engine operation.  At my home airport I take off and land with take off flaps. There is 10,000 feet of runway and no need to use full flaps. With the trim set to the take off position I land or go around.

If you have an auto pilot with altitude hold set power to 15" watch the auto pilot trim to level flight. Once 15" and level flight look at the trim position it will be at, or almost at , take off position. No coincidence at all.

 Land by the numbers and you will be able to CONSISTANTLY land. Fly YOUR plane find the exact numbers that work for you. Use those numbers and your landings will gain a consistency you never imagined.

One of the advantages of flying by the numbers as I suggest is you get into a very repeatable way of landing. If you use the gear to start the decent you will never land gear up. To come down the gear must be down. On an ILS the gear down starts you down. In the pattern parallel the approach end of the runway you drop the gear, dropping the gear starts you down.

 In my Mooney at 15" and 90 knots it won't land without the gear down.

I NEVER look at the tach while landing why would I ? I have a better tool to show power, the Manifold Pressure Gauge. I have no idea nor do I care what the tach reads while landing. I KNOW were my power is though.

At a power setting RPM changes with load. You saw this in the 172 you learned in. At cruise setting pull back and as the load increases the tach will drop. Same throttle setting push the nose over and watch the tach climb. Throttle DOES NOT DIRECTLY set RPMs it direclty sets MANIFOLD PRESSURE.  Power setting and load set RPMs.

I don't mean to be rude or abrupt be you need to get your mind out of that 172 and into your Mooney. Find the MP gauge it is there to use. It IS your power setting gauge.  

[201er]

Helpful advice about the pattern but I still don't see your point about MP vs RPM. What I understand is that when the "RPM below the prop-governing range, you have a fixed-pitch prop." (John Deakin). So when the throttle is back a ways (like in the pattern), throttle does directly control RPM just like a 172.

How do you go about landing with trim in takeoff position? I've been finding myself needing to trim nearly all the way back to get the plane slow enough on short final and touchdown.

[jetdriven]

201er, RJ, you both are right.  I have found that MP below 17" is pretty much useless.  The difference between 16" and 15" depends on density altitude, piston ring sealing, etc.   It is also a large change, But 1800 or 2000 RPM  to land on the guage always works.  The 201 has a rather unique characteristic, below 110~MPH or so, the prop is on the low pitch stop and it "is" a fixed pitch prop.  So in that range, treat it like one. 

[tony]

201er, I fly exactly as Randy has described. As I enter the pattern I'm pulling back the power to 20 inches of manifold pressure. Abeem the numbers, mixture and prop full forward with 15 inches of manifold pressure, gear down, two pumps of flaps and you should be trimmed for 100 mph, turn base one more pump of flaps and trim for 90mph, turn final and add the last pump of flaps, manifold pressure at 12inches and trim for 80mph. I really have no idea at this point what the tach gauge reads nor do I care. The yellow arch’s are meant for cruise, not low power settings. These are for resonants as Ross described. I have a three bladed prop and the STC moves the yellow archs to down by a third because the beat frequency is higher. I think you are being a bit over cautious.  If you are concerned, I would recommend you call your prop manufacture and clarify it for you.

[Jeff_S]

I have the Horizon digital tach which gives me a nice little yellow light when the the prop/MP combination falls into the yellow range. Other than powering up for the run-up, I don't recall EVER seeing that little yellow light come on in normal operations.

My J was my transition from fixed-pitch to variable-pitch prop and it confused me at first, but based on reading and experimenting I found I only need four settings. Max prop on takeoff. Reduce to 2600 for climbout. Reduce to 2500 in cruise. Reduce to 2400 if I want to slow my descent, but otherwise, have at 2400 for the pattern. Everything else is managed with throttle controlling MP. Easy, and never a yellow zone in sight!

[201er]

Wow, I've been doing practically the opposite of you. Except for descents and landing, the throttle stays full the entire flight and I control power with the prop knob and mixture.

[Shadrach]

201er,

Two things:

1) I believe that your current SOP for Take off, cruise and decent to landing are fine. My throttle stays forward until I need to slow down. That would be because of redline, or coming into the pattern, which I will happily do at 150 to 160KIAS and still be where I need to abeam the numbers.

2)Just to pick nits, there is no RPM range truly outside the range of the governor. There are however airspeed and power combinations that are outside the range of the fine pitch (prop control full forward) stops. Thought of another way, you can almost always reduce RPM by pulling the prop control back, but you will not always to be able to go red line going forward.  I cycle my prop on taxi during taxi between 1200 and 1000rpm. I do not do a 1700 rpm run up. 

 

[Hank]

It's really pretty simple:

WOT/Prop Fwd for Takeoff & Climb. Lean as desired in the climb [target EGT] or stay full rich.

Low cruise = 23/23; mid-alt cruise = 23 or 24"/2400; high cruise = WOT/2500 [your IO-360 will be different]

Descent = trim down, no changes; enrichen mixture to maintain cruise EGT as you descend. This helps make up for high fuel flow/low groundspeed during the climb. If it's too bouncy, pull some power out.

IFR Approach = your power settings for 90 knots [16"/2400, clean; add ~2" with T/O flaps for me]; Descent = drop gear 1½ dots above glideslope], no power changes.

VFR Approach = reduce power to 14-16", hold level altitude to decelerate; by downwind, T/O flaps, Full Rich and Full Prop; adjust throttle to hold 90 mph. Drop gear to begin descent, then simply use pitch to hold speed and wiggle the throttle if needed to adjust altitude and hold the proper glide, add more flaps if high or fast. My placard warns about holding the red RPM range below 15", but sometimes I'm there to land because there are trees on the approach and the wind is always different.

The key is to practice with your plane and learn YOUR power settings. Take someone to do the writing for you while you work the levers around the pattern, there's no time to write yourself. The power settings we are posting work for our individual planes, and should be viewed as guidelines. Then practice with your own numbers, and keep them for reference until you learn them well.

If you are worried about running your prop in the restricted band from VFR downwind to touchdown, talk to your A&P--there is no risk to your engine at low power settings for 1 or 2 minutes, just don't cruise there. Your POH should have a slow cruise setting [mine is 20"/1950 for 138 mph at altitude, with almost 8 hours endurance; handling is a little different there].

[John Pleisse]

Hanks numbers are dead on. 201'r...the operative words in the POH and on the placard are "continuous operation"...just use your noggin.

[N33GG]

I second the vote for Hanks information.  Well stated Hank.

My only additional comment is if you are landing at an airport that is a high elevation, you may not want full rich mixture, or your engine may die on the runway after landing.  Should be clear to all of us expert pilots, but we sometimes get into our procedures to the point that we forget to deviate if we are not used to landing at high elevations.  Please note that I would never make such a mistake...  :-)

[Hank]

George--

Make that "if you are landing at an airport with high density altitude, you may not want full rich mixture." My one visit to KRAP [what an identifier!], seems like field elevation is about 3300, but that afternoon ATIS said density altitude was ~6500' and to adjust your engine mixture for high altitude operation  per your POH. Worried me, coming in to land--my POH [er, "Owner's Manual"] doesn't high DA landings. . . . .

Glad your numbers match mine so well, since we have the same model! :-)

[Hank]

201er--

Don't get too lost in the numbers. Once the prop lever is full forward, your power control is the throttle. Yes, RPM will vary as it moves back and forth, but don't look at the tach to tell your power--look at the Manifold Pressure gage [mine MP is above the tach]. While all three levers are used in conjunction to set power, it is common to refer to MP/RPM for various flight regimes and to MP only when at low power such as power-off descents and landing. Fly with it for a while, spend some time with a good CFI, and it will start making sense. I had to have 15 hours when I transitioned from Brand C as a new pilot, and I learned for another year or more afterwards.

[N33GG]

Hank:

Yep, high density altitude is correct!

[flyboy0681]

Wow, the only thing I've taken away from this is that if you ask a dozen people how they set power, you get a dozen entirely different answers.

When I started flying my J I must have read everything there was to read about power settings and no two articles were the same.

 

I guess it boils down to using whatever you are comfortable with. As for me, I just follow the POH.

[Shadrach]

yup, and I'll throw this into the mix flyboy. I never go full rich on descent or in the pattern... I see no need to do so.  If I need to go around, I'll just push both knobs in. I've only had to go around twice and it's never been a dramatic situation, though I understand that it can be...  I do enrichen in decent, but only to keep the combustion event in the combustion chamber and out of the exhaust (those of you that pull the throttle back while in LOP cruise should know what I mean).  I almost always land full flaps, unless the wind is >20kt X-wind component.

Oh and just to stir the pot, I abhor the crab and kick crosswind landing method...