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RV-10 takeoff Power settings

AviatorJ

Well Known Member
I?m curious what others are using throughout takeoff and initial climb.

My home field is 1,200 MSL and at full throttle, forward prop I?m pushing 28? and 2680 RPM. I?m off the field in 500 ft, I shallow out around 500 agl and aim for 115 knots. At 1,000 agl I pull back squaring at 25?/2500. During climb out I adjust these settings to keep CHTs under wraps.

My RV-10 seems to have more power than the RV-10 I did transition training and more effective power through probably less drag than the 182 that I received my hp endorsement on.

It all works, just wondering if I?m being too aggressive.
 
My climb out consists of full power until 1500 agl. I then reduce power to 25/2500. I maintain 120kts in the climb and always keep the CHTs under 400. I lean in the climb to 1300 deg egt, which is usually close to the takeoff egt. I also continue to increase power setting in the climb, not exceeding 25”. I generaly cruise above 9000ft. LOP. I always cruise at 2400rpm and full throttle.
 
Justin, I would suggest adjusting your prop so your reaching the max 2700 RPMs. 20 RPM makes a difference, especially at high altitude airports. I found 120 kits seems to be a nice climb speed (both for cooling and vertical speed) after clearing the airport and proper obstacle clearance. I prefer keeping the prop around 2600-2650 on the climb. I keep the throttle full on climb out until reaching cruise altitude, then set mixture/prop accordingly for your cruise. Remember, your manifold pressure will be naturally reduced as you climb. Also, just old school rules, I don?t mess with throttle, prop, boost pump, etc. on the initial climb until at least 1000 feet plus AGL. This way if something burps, your at a safer altitude to respond to it.
 
Why on earth do people persist with this 25/25 OWT.

If you knew its origins, you would laugh. If I told you, it would make you think I was taking the <insert naughty word>.

So in summary, the engine is slightly worse off for you doing this. Is it critical, no, but it is real.

The most efficient climb-cruise-descent profile is achieved like this.

1. Takeoff at WOT/2700/full rich. At higher fields you may need to lean to about 1300dF (based on mags not EI's)
2. Climb WOT/2700/ Target EGT (1300 in these planes) and at Vz which is 120-125KIAS
3. Cruise WOT / 2300-2500 (pick a smooth spot, many use about 2300-2400) and appropriately LOP. That is 10-20dF at higher levels, 25-40 mid levels and 50-80 at sea level to say 3000'. A well executed Big Mixture Pull will be fine at any level.
4. descent .....nose over, maybe remove a few hundred RPM, back the throttle off to remain out of the yellow arc.......Mixture leave well alone unless there is any sign of stumbles, then only tweak it enough to smooth them out. Land, ICO at the hangar or ramp. If you really cant do the lean landing, go full rich and then lean again for taxi.

The engine is rated at full power all day long. 25/25 was borne out of old WWII pilots who became instructors and they had to find a power reduction from METO in their old warbirds......there was not one, so when they found a recommended cruise climb of 25/2500 (marketing blurb not engineering based) they had discovered what was missing. That was it!

I know it sounds too silly to be true, but my friend and training partner John Deakin lived back in those days and lived through it. Probably in the engine articles on Pelicans Perch he will have written about this OWT. If not, here it is now.

Hope that is helpful. :)
 
I always thought the throttle had only two positions, takeoff and land.

I go to above 1,500? at 2700 rpm and bring the prop back to 2,500. Climb is 130 Knots to cruise altitude. Mixture comes back at 5,000? density altitude to about 13 gph. At cruise, usually above 15,000 for long legs (depending on winds) prop to 2,300 rpm and lean to peak and then richen to peak speed. The throttle never leaves full forward.

(On descent I hand to admit to pulling the throttle a bit to avoid the over speed nag.)
 
Bruce,

Why do you reduce to 2500 RPM at 1500' ? You probably know it but that is reducing your available power for climb. It is also harder on the engine, by a small amount.

I would suggest the 5000' action is much harder on the engine. You should check it out in terms of how far ROP you are, the red box principal is worth considering. Target EGT climbs manage this a lot better. https://www.advancedpilot.com/redbox.html
https://www.advancedpilot.com/tech.html Download the target EGT file.

Cruise above 10k' you might as well go fast if you want. Thats about 75-100dF ROP and no problem there at those powers.
 
Being a good neighbor -- noise control

I have no argument with the WOT/2700 operation for aircraft efficiency --- but, I live in a heavily populated, noise-sensitive area --- I try to minimize my noise footprint by reducing power and RPM as soon as practical--- and climb to a higher altitude slower.
We do have a few individuals that leave their prop screaming at high RPM and their presence is certainly apparent.

Just saying --

Ron
 
Ron, if noise is the issue, leave the throttle and mixture forward. Break ground, reduce to 2600, that first 100 rpm drop gets rig of a huge amount of noise. Once you are through 1500' go back to 2700.

This does everything it should and nothing it shouldn't.

Hope that helps.
 
Here?s a simple way to think about it. If you had a fixed pitch prop on the front of the RV-10 you probably wouldn?t pull the power back. So, noise considerations aside (and temps of course), why pull it back with the constant speed?

The engine is rated for 2700 rpm?s all day long. As a matter of fact, during certification they run them at full rated power, with all of the temps maxed for 150 hours straight!

Especially when breaking the engine in, keep the manifold pressure high if you must pull the prop back. It seats the rings better and faster.

Vic
 
Since there is obviously a lot of passion regarding correct power settings for climb I won't get mixed up in that, but hopefully people will at least keep noise signature in the back of there mind. It is a much bigger problem than most of us are willing to admit. Particularly on RV's without mufflers.
 
I appreciate all the responses.

I took off yesterday kept it all forward up to around 2000 AGL before the engine temps started getting a bit high. I'm going to keep testing it out to see what works best, but I'm going to stop being paranoid about the squaring of the engine.
 
I appreciate all the responses.

I took off yesterday kept it all forward up to around 2000 AGL before the engine temps started getting a bit high. I'm going to keep testing it out to see what works best, but I'm going to stop being paranoid about the squaring of the engine.

High? If you climb at 125KIAS it should not get high. Or is it a new engine?
 
I took off yesterday kept it all forward up to around 2000 AGL before the engine temps started getting a bit high.

Go back to the NACA research on air cooling, and you'll find a little gem...cooling requirement is proportional to mass flow. For those of us not wearing lab coats, it translates to cooling requirement is proportional to RPM, because our engines are volumetric air pumps.

Now take a look at the 540 power charts. Over on the left you'll find a limit line for manifold pressure vs RPM. The whole chart assumes best power mixture. I've taken the liberty of highlighting the limit line in red, and the notations in green. You can pull RPM back to 2500 at full throttle (>29") with no danger at all, while leaned to best power. 2300 would be the absolute limit at sea level manifold pressure....and this is the chart for a K-model, generally assumed to be among the most detonation prone of the Lycomings.

IO540K%20Power%20Chart%20w%20notes.jpg


Bruce, Why do you reduce to 2500 RPM at 1500' ? You probably know it but that is reducing your available power for climb. It is also harder on the engine, by a small amount.

No, it is not harder on the engine. Inertia stress goes with the square of piston speed, so here reducing RPM from 2700 to 2500 reduces that stress by 14%. At the same time, power is reduced by approximately 7.5%.

So Justin, if a bit lower CHT is your goal, I'd recommend the approach Bruce mapped out. I do pretty much the same, although with the lower typical CHT of the angle valve I begin leaning to maintain constant EGT much earlier than 5000. You want to try 2500/WOT and target EGT for climb. If I assume fixed timing, I'd guess Bruce's "lean to best speed" is just a little rich of peak.
 
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Dan, you are taking only one element.

ICP increases with 2500/2700.

I would say however, both elements are in real terms not that serious.

No, it is not harder on the engine. Inertia stress goes with the square of piston speed, so here reducing RPM from 2700 to 2500 reduces that stress by 14%. At the same time, power is reduced by approximately 7.5%.

Dan, the power is reduced by 7.5%, but the ICP increases by (rough guess) 4%, while the inertial change affects some items, they are not the items that suffer relative to their ability.

Pick ya poison. But this is a futile argument.

What is not futile is that if you assume a desire to climb to a height in a given time or at a given IAS, the longer you subject the engine to higher ICP and with reduced cooling airflow this is harder on the engine.

Smarter people than us have proven this.
 
Dave, I agree, except I reduce the RPM to 2500 at 500 agl, for noise. Significant sound reduction from 2700 to 2500. Otherwise same as you. I use this for our IO390 powered RV14A or my D95A Travel Air.
 
Dan, you are taking only one element.

First three paragraphs, in order, are cooling demand, cylinder pressure, and inertia.

ICP increases with 2500/2700.

Yes Dave. The big chart says the dreaded high ICP is well within limits...not that it matters, because it is rapidly decreasing with every additional foot above sea level. Inertia, on the other hand, does not.

Returning to cooling demand, which seems to be the OP's interest...

Smarter people than us have proven this.

Cooling demand is proportional to mass flow, i.e. RPM in the case of a normally aspirated 540. I'll show you mine. You show me yours ;)

Cooling%20Demand%20-%20NACA%20787.jpg


Cooling%20-%20Taylor%20annoted.jpg
 
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Dan,

We can agree on what you posted, that is not in dispute at all.

However, climbing to altitude, at reduced rpm (power) if you wish to have climb time as a constant, involves higher angle of attack and lower airspeed.

Yes the peak pressure reduces with lowering MAP (except in a turbo of course), but it is always going to be higher for all given altitudes, so you subject the engine to higher forces for longer all the while having less cooling air.

At the end of the day the effects are subtle and not of significant margin, but when you get your cooling together (as you so eloquently do and advise) you are better off using 2700 and getting to TOC sooner and with more cooling airflow.
 
However, climbing to altitude, at reduced rpm (power) if you wish to have climb time as a constant, involves higher angle of attack and lower airspeed.

Straw man argument. Nobody does it.

Fly your usual cruise climb IAS at WOT after a pull to 2500. Lean in the climb, target EGT method, rather than full rich "for cooling". Report back.
 
Why on earth do people persist with this 25/25 OWT.

If you knew its origins, you would laugh. If I told you, it would make you think I was taking the <insert naughty word>.

So in summary, the engine is slightly worse off for you doing this. Is it critical, no, but it is real.

The most efficient climb-cruise-descent profile is achieved like this.

1. Takeoff at WOT/2700/full rich. At higher fields you may need to lean to about 1300dF (based on mags not EI's)
2. Climb WOT/2700/ Target EGT (1300 in these planes) and at Vz which is 120-125KIAS
3. Cruise WOT / 2300-2500 (pick a smooth spot, many use about 2300-2400) and appropriately LOP. That is 10-20dF at higher levels, 25-40 mid levels and 50-80 at sea level to say 3000'. A well executed Big Mixture Pull will be fine at any level.
4. descent .....nose over, maybe remove a few hundred RPM, back the throttle off to remain out of the yellow arc.......Mixture leave well alone unless there is any sign of stumbles, then only tweak it enough to smooth them out. Land, ICO at the hangar or ramp. If you really cant do the lean landing, go full rich and then lean again for taxi.

The engine is rated at full power all day long. 25/25 was borne out of old WWII pilots who became instructors and they had to find a power reduction from METO in their old warbirds......there was not one, so when they found a recommended cruise climb of 25/2500 (marketing blurb not engineering based) they had discovered what was missing. That was it!

I know it sounds too silly to be true, but my friend and training partner John Deakin lived back in those days and lived through it. Probably in the engine articles on Pelicans Perch he will have written about this OWT. If not, here it is now.

Hope that is helpful. :)

As I experiment in my 10, i am finding that at 8000? and WOT (2400) i am having to be around 100* Lop or more to get the economy fuel flows that i want. This causes a rougher running engine with a very occasional miss. I have instead pulled the throttle back to get to a point where i am 40* Lop. Curious how others are setting up for a 165 kt speed with 10.5 to 11 gph flow.

Larry
 
To achieve well lean of peak, smooth running, you need to adjust your injector nozzles so all cylinders reach peak egt at the same fuel flow.
 
To achieve well lean of peak, smooth running, you need to adjust your injector nozzles so all cylinders reach peak egt at the same fuel flow.

I have. 5 of the cylinders are a .2 spread and the last is another .2 from that range. It was the best I could do. Unfortunately, I can't get that last cyl in line. It is either .3 richer or .3 leaner than the base line average across the other 5.

I guess I wouldn't call it rough, just not as smooth as 50 lop or richer. It was mostly the occassional miss (every couple of minutes) that bothered me.
 
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Riching up to peak speed

When I richen to peak speed at cruise, I use my Dynon to first lean until all EGT drop and note the fuel flow spread (GAMI number that Dynon has as part of its lean routine ) just for interest. It has been reasonably consistent since it was new, around .2 to occasionally.5 GPH. If it ever changes a bunch, will look for the cause.

After stable at cruise on autopilot I note the TAS and richen about 1/3 turn. Wait a couple of minutes and recheck TAS. It does not respond quickly. After a couple of iterations I only richen 1/4 turn. After a bit the TAS will drop a touch, so go a bit leaner.

Takes a while, but cruise is boring and there ain?t many exciting things to do. Every hour or so I may lean it up a bit and do it again out of boredom.

It generally gets me 2-4 knots and a bit more fuel, but the -10 does long legs, about my bladder limit.
 
Since there is obviously a lot of passion regarding correct power settings for climb I won't get mixed up in that, but hopefully people will at least keep noise signature in the back of there mind. It is a much bigger problem than most of us are willing to admit. Particularly on RV's without mufflers.

Scott, has Van's done any noise testing with the same aircraft, with and without mufflers?
Just curious what the quietest results are.

(My neighbors continually comment on how quiet my FP -9 is on takeoff and when entering the pattern and I do not have mufflers. Probably because I have to reduce power way back to get it slowed down in the pattern.
 
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