climb power

[Shadrach]

55 minutes ago, RescueMunchkin said:

What are the pros and cons of full throttle climb from sea level? I was taught 25/25 and trim for 500fpm climb once clear of obstructions and have been using it to be easier on the engine (I'm never in a rush when flying).

What kind of engine?  What happens to your EGTs and CHTs when you "pull back"?

I flew with a forum member who was in the habit of throttling back for climb in his 1963 C model. EGTs immediately elevated a considerable amount and CHTs started started to do the same but slower. This does not seem to be the case for all O360 powered Mooneys.  Some owners insist that reduced throttle is the only way to control temps.

All of the NA injected Lycomings have tuned intakes. They are designed to maximize volumetric efficiency at max throttle. I don't recall operating one that benefited from  reduced power climb operations. 

[RescueMunchkin]

I was taught the 25/25 when I trained in an M20G with the O-360. My current plane is a M20F with the IO-360.

I've not really paid much attention to the EGTs or CHTs in 24-25/25 climb other than to validate they aren't getting high enough to be concerning.

My POH also says to climb at 26/26, but I (maybe incorrectly) assume that running 24-25inMP would be gentler on the engine despite it taking longer to get to cruise altitude.

[jetdriven]

It is not gentler on the engine, in fact, I would say that it’s worse. You spent a longer period of time in your climb at a very rich mixture which trashes the oil and the piston ring lands, and put carbon everywhere else too. And then also the climb takes longer. It’s further down range and it also often runs warmer because airplanes climb because of excess horsepower so when you reduce horsepower certain amount it all comes at the expense of  climb. There’s an acquaintance of ours who runs the air race classic in her 182 and she’s probably done a dozen of them. Now the engine is  past TBO and she’s doing the race this year too. If all that full bore low altitude max power leaned to a hundred rich peak a lot of times is so bad for it,  Imagine how long it would’ve lasted otherwise. 

[EricJ]

When I went to A&P school one of the old salt instructors, who'd been maintaining GA airplanes for many decades, had owned an FBO, etc., asked me how I was running my engine.   I told him generally WOT all the time, and either full-forward on the prop or 2500 rpm.    He said, "Good.  Keep all the pressures up."    That seemed like a really good way to summarize it.

 

[PeteMc]

5 hours ago, RescueMunchkin said:

What are the pros and cons of full throttle climb from sea level?

A few decades ago John Deakin (maybe it was George Braly) did some tests and found that obviously they reached altitude and cruise speed faster with everything in (or at max allowable power) with no impact on the engine.  I believe some math also showed the small increase in power from his original climb practice was greatly offset by reduced time  to altitude and cruise speed.  So ultimately better for the engine.

You need to keep an eye on the cylinder temps and in some circumstances you may need to reduce your climb rate for more airflow or actually reduce power.  And a lot of pilots will level off and pull the power back right away, but you not at cruise speed yet.  He emphasized that you leave the power in for a short time until you reach your typical cruise speed.  Then start tweaking for the % power you want. 

 

[Fly Boomer]

20 minutes ago, PeteMc said:

And a lot of pilots will level off and pull the power back right away, but you not at cruise speed yet.  He emphasized that you leave the power in for a short time until you reach your typical cruise speed.  Then start tweaking for the % power you want. 

When I took the class, I remember this coming from John Deakin.  He said "Okay, now that we have reached our cruising altitude, what's the first thing we do?"  Most of the class said "reduce power", but Deakin said the answer was "nothing".  Or if you must do something, wind the clock.

[Hank]

26 minutes ago, Fly Boomer said:

When I took the class, I remember this coming from John Deakin.  He said "Okay, now that we have reached our cruising altitude, what's the first thing we do?"  Most of the class said "reduce power", but Deakin said the answer was "nothing".  Or if you must do something, wind the clock.

Level off and accelerate, then once IAS is fairly steady, start leaning and watch it move up again.

[PeteMc]

43 minutes ago, Fly Boomer said:

I remember this coming from John Deakin.

So it was John.  I remember discussing it back in the AVSIG days when he was first experimenting with the full power climb. 

[PT20J]

9 hours ago, RescueMunchkin said:

What are the pros and cons of full throttle climb from sea level? I was taught 25/25 and trim for 500fpm climb once clear of obstructions and have been using it to be easier on the engine (I'm never in a rush when flying).

That’s actually a good question.

If the engine has no time limit on operating at maximum continuous power, it won’t cause any immediate damage. However, engine life is a function of power and the best way to get past TBO is to run at lower cruise powers. So, does using higher climb power in a normally aspirated engine shorten its life? Probably not. The available WOT manifold pressure (and thus power) drops about an inch every thousand feet as you climb anyway. So, you really aren’t running at high power for a significant portion of the engine’s life.

But, if you do reduce climb power, reduce it all the way back to about 75%. Fuel systems are usually set up to provide an overly rich mixture at high power settings for cooling and increased detonation margin. The mixture enrichment system is mechanically linked to the throttle and only works at WOT or nearly so. So if you pull the manifold pressure back just a little, you may defeat the enrichment feature.

[Shadrach]

6 hours ago, PT20J said:

However, engine life is a function of power and the best way to get past TBO is to run at lower cruise powers.

Engine life is a function of many, many factors. Power level is just one and is likely not nearly as consequential as others. 

It would be nice to have some test bed data on a sample of engines run for 2000hours at various power levels under the same conditions with a post hoc analysis of the internals to determine wear.  My guess is the differences would be minuscule 

[M20F]

I dial back to 2600, it’s quieter and it climbs at the same rate. 

[Pinecone]

11 hours ago, PeteMc said:

So it was John.  I remember discussing it back in the AVSIG days when he was first experimenting with the full power climb. 

I was around those days also.  Some wild discussions.  And many people telling them their engines would be trash in 10s of hours.

[Stubby]

I flew with an instructor just last year that recommended 25/25 on climb. The instructor's reasoning was noise abatement and it's easier on the engine. My normal procedure is WOT all the way to cruise. I'm usually at 25" within a couple of minutes anyways and getting that first 1000' below me seems more important than whatever (if any) hours reducing the power would add to my engine. As far as engine damage goes, I worry more about the time spent full rich rather than time spent at full power.

[Paul Thomas]

I also dial it back to 2,600 because that's what the POH states and I like that it's quieter; I also thought it was better for the engine. I do keep WOT and lean to target EGT every 1,000 feet or so.

[PT20J]

4 hours ago, Shadrach said:

Engine life is a function of many, many factors. Power level is just one and is likely not nearly as consequential as others. 

It would be nice to have some test bed data on a sample of engines run for 2000hours at various power levels under the same conditions with a post hoc analysis of the internals to determine wear.  My guess is the differences would be minuscule 

If it were true that power had no effect on engine life then why would Robinson derate engines in its helicopters and why would Lycoming and all the airframe manufacturers recommend cruising at 75% or lower power? And why would Mike Busch cruise at 65% or below. For a while John Deakin was experimenting with running his turbonormalized Bonanza LOP at 80%+ but I understand that he decided it wasn’t such a good idea. The fact that something isn’t prohibited does not mean it’s a good idea.

[PT20J]

Reducing rpm to 2600 on a 200 hp IO-360 costs 8 hp according to the Lycoming power charts. 

8 hp = 4400 ft-lb/sec = 264,000 ft-lb/min

So, if your plane weighed 2640 lbs, the rate of climb would be reduced by 100 fpm. 

[EricJ]

34 minutes ago, PT20J said:

Reducing rpm to 2600 on a 200 hp IO-360 costs 8 hp according to the Lycoming power charts. 

Assuming constant torque vs rpm over the region of interest, which isn't a bad assumption on these engines, it's easy to estimate the reduction in power just by scaling rpm.   In other words:
 

(2600/2700)*200hp = 192.59 hp.   So a loss of 7.4 hp, or about 4%.    It's not a lot, but you'll definitely notice it in a long climb or on a hot day.

[PeteMc]

3 hours ago, Stubby said:

I flew with an instructor just last year that recommended 25/25 on climb. The instructor's reasoning was noise abatement and it's easier on the engine.

I do agree with the noise abatement for some areas. 

 

[RescueMunchkin]

Maybe I'm in a minority here, but I have to deal with staying under Class C shelves when I depart, so I have to either pull back throttle or go blasting balls to the wall at 1500 ft MSL for several miles, which does not seem to me to be good for fuel economy or the engine.
I think when I'm ready to climb up to cruise altitude in the future, I'll try the full throttle method, but when doing this, are you guys also leaving mixture full rich until stabilized at cruise altitude?  In most of my 25/25 climbs, I've been pulling mixture back to ~150 degrees ROP

[jetdriven]

2 hours ago, PT20J said:

If it were true that power had no effect on engine life then why would Robinson derate engines in its helicopters and why would Lycoming and all the airframe manufacturers recommend cruising at 75% or lower power? And why would Mike Busch cruise at 65% or below. For a while John Deakin was experimenting with running his turbonormalized Bonanza LOP at 80%+ but I understand that he decided it wasn’t such a good idea. The fact that something isn’t prohibited does not mean it’s a good idea.

Robinson derates their engines to improve altitude performance.   They can still make the rated HP to 5000.  It’s not for longevity.  
Lycoming recommends 75% power and less because you can lean it there.  You can run it at a higher power setting but it goes pretty quickly to full rich which is pretty awful fuel specifics.  65% is pretty much the most efficient power setting for airplanes.  It sells airplanes.  
 

https://www.timtuckershelicopterworld.com/post/unlocking-the-mysteries-of-robinson-s-derated-engines

[PT20J]

13 minutes ago, jetdriven said:

Robinson derates their engines to improve altitude performance.   They can still make the rated HP to 5000.  It’s not for longevity.  
Lycoming recommends 75% power and less because you can lean it there.  You can run it at a higher power setting but it goes pretty quickly to full rich which is pretty awful fuel specifics.  65% is pretty much the most efficient power setting for airplanes.  It sells airplanes.  
 

https://www.timtuckershelicopterworld.com/post/unlocking-the-mysteries-of-robinson-s-derated-engines

Good points, and I don’t disagree. Still it defies logic that you can run continuously at max power and get the same life as 65%. Higher speed, temps and pressures. 

[EricJ]

25 minutes ago, RescueMunchkin said:

Maybe I'm in a minority here, but I have to deal with staying under Class C shelves when I depart, so I have to either pull back throttle or go blasting balls to the wall at 1500 ft MSL for several miles, which does not seem to me to be good for fuel economy or the engine.
I think when I'm ready to climb up to cruise altitude in the future, I'll try the full throttle method, but when doing this, are you guys also leaving mixture full rich until stabilized at cruise altitude?  In most of my 25/25 climbs, I've been pulling mixture back to ~150 degrees ROP

Just keep leaning to maintain the takeoff EGT, or typical takeoff EGT.    e.g., if you takeoff in high DA, leaning to your usual takeoff EGT is a reasonable thing to do, then maintain it during climb.    You won't go excessively rich to the point of losing power this way.

[hammdo]

My takeoff EGTs are between 1270° and 1295° - that is what I lean too after about 3000 MSL or if DA is high… then look to keep CHTs in line…

-Don

[PeteMc]

1 hour ago, RescueMunchkin said:

Maybe I'm in a minority here, but I have to deal with staying under Class C shelves when I depart, so I have to either pull back throttle or go blasting balls to the wall at 1500 ft MSL for several miles, which does not seem to me to be good for fuel economy or the engine.

Doubt it would be an issue for the engine.  But even if you do pull back to clear the CBA, just like any other long climb, there is no reason you can't put the power back in.

 

[Shadrach]

7 hours ago, PT20J said:

If it were true that power had no effect on engine life then why would Robinson derate engines in its helicopters and why would Lycoming and all the airframe manufacturers recommend cruising at 75% or lower power? And why would Mike Busch cruise at 65% or below. For a while John Deakin was experimenting with running his turbonormalized Bonanza LOP at 80%+ but I understand that he decided it wasn’t such a good idea. The fact that something isn’t prohibited does not mean it’s a good idea.

If derating the angle valve IO540 from 300hp to 245hp is so meaningful for longevity, then why are the TBO’s identical? Surely the power plant making 23% more power should have a shorter TBO?