1st Power Reduction in the Climb

[oldShar]

There can be multiple reasons for having Takeoff power higher than METO and requiring a reduction after takeoff.
--- a common reference is to overheating by overstressing the engine and the cooling system
=== often forgotten is oversizing the prop to squeeze out more efficiency in takeoff, which could stress the prop;
but another biggie (from a bygone era) is concern over noise pollution --- reducing power (especially on the long props) to reduce noise over the population centers that want excuses to close down airports.

Some of the power reductions could be political contributions by manufacturers to both advertise spiffy performance and be PC to the pounders who locate on the runway extended centerline (similar to car manufacturers that bias speedometers to keep actual speeds below speed-demon desires for high speed indications)

 

[Sac Arrow]

Any limitation you may have is one of power, and not necessarily a specific MP and RPM limitation. Deakin's point is you can still stay within that power limitation full throttle, full RPM if you lean sufficiently, as in lean of peak past the detonation box.

But unless you really know what the f*** you're doing, you're still best off following POH procedures and limitations.

 

[Ted]

But unless you really know what the f*** you're doing, you're still best off following POH procedures and limitations.

 

[coloradobluesky]

People think they know where lean of peak is, and they don't. Cooking turbcharged engines. A lot of pilots burning things up trying run lean of peak. Be careful out there. Watch the CHT's. I dont like to get any closer that 50 degrees to the max. So if the max is 500, I dont want to go higher than 450. If you stay below 65% power, you will have a safety buffer and most likely make TBO. All it takes is ONE overheating event. One thing melts and away goes everything. Follow the manual. Talk to some mechanics. Talk to other users of you model aircraft, especially ones that have been doing it a long time.

 

[Checkout_my_Six]

yup....

 

[Fearless Tower]

Hey, what do you know.....you some kind of engine guy????

 

[Henning]

On CS Prop airplanes, the procedures usually include reducing power during the climb after takeoff and also reducing prop RPM.

My first CS Prop airplane I transitioned into was the DA-40 and this was the practice. Thinking about it this morning, I recall that I opted to not make any changes until I thought we had reached a safe altitude, which was about TPA or sometimes just after pushing the nose over to not bust the Bravo shelf.

My rationale was that changes could induce a powerplant failure and if it's working fine now, leave it alone. This is counter-intuitive to the fact that the engine is working hardest at this setting and that pressure and temperature are the biggest enemies to a happy engine.

Are there merits to delaying the power reduction? How about carry that thought to the extreme and reduce power immediately after leaving ground effect? How about at Vr?

The whole 'power change hazard' is an OWT. Even if your plane is in such bad shape that the control linkages fall off, the default conditions will keep you going, the trick is landing WOT, you want to be way LOP and control your power in bursts with the mag switch like they did the old Rhone Gnome rotary engines.

It's really no big deal where you make your power reduction. If you want to fly the max power profile all the way to altitude, the plane will handle it without complaint, just monitor and manage your CHTs.

Personally my first power reduction, which may be as low as 250' depending on terrain and target altitude, is done with mixture levers and I grab back for the fuel flow that I know will land me about 15°LOP at that altitude, and I let it climb like that WOT/Redline RPM and monitor my CHTs. At cruise altitude I pull back the prop for cruise RPM (in the 310 I used 2450 because she ran her smoothest there) and then I trim back mixture until the engines start falling off, give enough back to make her pull and gain her throat, and that's where it stays until approach.

In a single I would not reduce power until I had a landing made.

 

[Jaybird180]

The whole 'power change hazard' is an OWT. Even if your plane is in such bad shape that the control linkages fall off, the default conditions will keep you going, the trick is landing WOT, you want to be way LOP and control your power in bursts with the mag switch like they did the old Rhone Gnome rotary engines.

It's really no big deal where you make your power reduction. If you want to fly the max power profile all the way to altitude, the plane will handle it without complaint, just monitor and manage your CHTs.

Personally my first power reduction, which may be as low as 250' depending on terrain and target altitude, is done with mixture levers and I grab back for the fuel flow that I know will land me about 15°LOP at that altitude, and I let it climb like that WOT/Redline RPM and monitor my CHTs. At cruise altitude I pull back the prop for cruise RPM (in the 310 I used 2450 because she ran her smoothest there) and then I trim back mixture until the engines start falling off, give enough back to make her pull and gain her throat, and that's where it stays until approach.

In a single I would not reduce power until I had a landing made.

...or somewhere in the ballpark

 

[James331]

Read the POH and the pilots manual for the engine, follow that. I'm inclined to listen to the folks who put the dang thing together over all these talking heads.

 

[Ted]

Hey, what do you know.....you some kind of engine guy????

Well I obviously don't know as much as people who read Deakin and treat it as gospel.

 

[Checkout_my_Six]

Well I obviously don't know as much as people who read Deakin and treat it as gospel.

you do know Deakin knows more than the OEMs?....right?

 

[Turningfinal]

you do know Deakin knows more than the OEMs?....right?

There are quite a few scenarios where I would take the advice of Mike Busch or John Deakin over the OEMs.

 

[Checkout_my_Six]

There are quite a few scenarios where I would take the advice of Mike Busch or John Deakin over the OEMs.

I'm sure you'll get what you paid for....

Ok....joke time.

A lawyer, a dentist, and a 777 captain walked into a bar.....they came out with an APS seminar.

Ya Mike is OK.....he got RCM religion and that's good.

 

[Hank S]

I think you misread that. I meant passing through 500 ft. in the climb

No, I understood. You climb long, slow and hot to altitude. I keep WOT from the departure end of the runway to the destination, when it's time to slow down.

Last night I was vectored for the ILS, and I kept speed up until I was level on the localizer, waiting for the glideslope to come down.

 

[Henning]

...or somewhere in the ballpark

Right, you grab for the number on the fuel flow because it will indicate first, then you watch the EGT respond, and trim it when it settles. Sounds more complicated than it is, and actually, once you know what the numbers are, they are pretty static and very little trimming occurs.

 

[jesse]

Right, you grab for the number on the fuel flow because it will indicate first, then you watch the EGT respond, and trim it when it settles. Sounds more complicated than it is, and actually, once you know what the numbers are, they are pretty static and very little trimming occurs.

It's really pretty easy to do after you do it a few times. In the Malibu I switch the analyzer to the TiT view, pull the mixture to the fuel flow I expect will be right, and then adjust slightly to get the TiT where I want. Then I switch to the CHT view on the number 5 cylinder and confirm the temperatures on it are dropping. Takes me about two or three seconds.

 

[Henning]

It's really pretty easy to do after you do it a few times. In the Malibu I switch the analyzer to the TiT view, pull the mixture to the fuel flow I expect will be right, and then adjust slightly to get the TiT where I want. Then I switch to the CHT view on the number 5 cylinder and confirm the temperatures on it are dropping. Takes me about two or three seconds.

People tend to make it a more difficult process than it is, and if you don't have a good fuel flow, you're handicapped.

 

[ZeroPapaGolf]

Some engines, mine included (Lycoming O-360 A1F6D), have a setting that enriches the mixture with full throttle for additional cooling in the climb. It is a mistake to pull the throttle back before cruise altitude. Always full throttle for the climb. But that's just some engines. Other engines may require different procedures.

That is also the case with the TIO-540. The documentation from Lycoming speaks very strongly against using anything but full power for takeoff and climb for this reason.

 

[gismo]

Perhaps a silly question, but what engines do/don't? I've heard that advice before from Deakin, but in my IO-470 powered Baron, when I'm taking off from Phoenix or even here in Norfolk in the middle of the day in the hot summer months (OAT above 100F), shallowing the climb and pulling the throttles back is the ONLY way I can keep CHTs below 400F.

Do the IO-470s lack the full throttle enriching, or is it just a factor of the feature not being able to do enough at that OAT?

Unless your baffles are in bad shape, chances are your full power FF is a little too low. Before and after I upgraded my IO470s to IO520s I've had no problem with full power climbs other than the need to keep the IAS at or above Vy after a minute or two on hot days which isn't much of a problem because I normally climb at Vy+ 15 to 25 anyway.

And if set up per the TCM SB, the mixture does get leaner an IO470 when you pull the throttle back to 25 inHg and reducing RPM from 2625 to 2500 raises peak cylinder pressure. Neither is likely to be an issue with an IO470 as they have significant detonation margins but IMO full throttle and max RPM are likely no more stressful than the common practice of a deliberate power reduction early in the climb.

If you have an engine monitor you might check what your EGTs do when you pull the throttle back to 25 inHg at low altitude. If you do this while climbing you'll have to look quickly as the mixture is getting richer as you go higher.

 

[Aaronk25]

Unless your flying high hp lyc turbo like in the Navajo its darn tough to get 100ll to detonate. Yes you can run Chts way high climbing at 30rop full power but I got a $100 bill that says 99% of you CAN'T get the engine to detonate/auto ignite if your at or below the mfg recommended Chts regardless where the mixture is.

In fact a 200hp IO-360, 25d timing with 8.7 -1 compression won't detonate/pre-ignite even burning 91 no-ethonal auto fuel, given its flown outside the red box. I know some experimental guys who have thousands of gallons of auto fuel under there belt in this higher strung engine.

Point is backing of the power when burning 100ll isn't helping anything or hurting but geeze what a critical phase of flight, wouldn't a person want to gain as much altitude as quickly as possible?


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[Cpt_Kirk]

Point is backing of the power when burning 100ll isn't helping anything or hurting but geeze what a critical phase of flight, wouldn't a person want to gain as much altitude as quickly as possible?

That would be using common sense in the airplane and would be perfectly reasonable unless restricted in the POH. That's not allowed on here.

 

[PPC1052]

Unless your flying high hp lyc turbo like in the Navajo its darn tough to get 100ll to detonate. Yes you can run Chts way high climbing at 30rop full power but I got a $100 bill that says 99% of you CAN'T get the engine to detonate/auto ignite if your at or below the mfg recommended Chts regardless where the mixture is.

In fact a 200hp IO-360, 25d timing with 8.7 -1 compression won't detonate/pre-ignite even burning 91 no-ethonal auto fuel, given its flown outside the red box. I know some experimental guys who have thousands of gallons of auto fuel under there belt in this higher strung engine.

Point is backing of the power when burning 100ll isn't helping anything or hurting but geeze what a critical phase of flight, wouldn't a person want to gain as much altitude as quickly as possible?


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Is detonation the only concern with running your engine too hot? I am no expert on this.

 

[Sac Arrow]

Is detonation the only concern with running your engine too hot? I am no expert on this.

Of course not. If the CHT's get too hot, cracked and/or warped cylinders can result. Aluminum is happiest when kept under 400 degrees.

 

[Fearless Tower]

Is detonation the only concern with running your engine too hot? I am no expert on this.

No, excessive heat can result in damage or reduced longevity of cylinders. Lycs handle heat a little better than Continentals.

 

[ZeroPapaGolf]

I say you can go oversquare by 5. Like 25" and 2000rpm. Nothing wrong with square though. 2500rpm 25" is ok.

You will notice if you are running 2500rpm, 25" and you reduce throttle to 18" as you reduce rpm from 2500 to 2000rpm the manifold pressure goes UP from 18" to 20".

I guess you've never flown a turbocharged plane. 40"/2400rpm would blow your mind.

 

[mkosmo]

I guess you've never flown a turbocharged plane. 40"/2400rpm would blow your mind.

One of the many rules of thumb in aviation that I find absolutely insane but so many preach as gospel.

 

[Henning]

No, excessive heat can result in damage or reduced longevity of cylinders. Lycs handle heat a little better than Continentals.

Now a days with third party cylinders, that's a crapshoot anymore.

 

[Henning]

I guess you've never flown a turbocharged plane. 40"/2400rpm would blow your mind.

True, but typically they are 6.5-7.5:1 compression ratio engines.

There is a bit of validity in what is behind it, but it is taught in a simplified statement which of itself is invalid.

Due to the relationship of HP=time (RPM) * torque (Inner Cylinder Pressure), if power (TAS) is to stay constant, if you reduce RPM, you have to increase the pressure on the piston, this is represented in Manifold Pressure in most HP recips. To increase the pressure on the piston and reducing RPM increases the thermal efficiency of the fuel, but for every fuel there comes a point where it will spontaneously combust at a high enough pressure when in the presence of an oxidizer. Supercharged engines run a much higher manifold pressure to attain the same ICP due to the reduction in mechanical compression ratio of the pistons. In the end they are both 285hp engines at 2700RPM. The turboed engine just carries it to altitude. Now even more efficient than a Turbo Supercharged configuration is a Turbo Normalized one, where the turbo engine maintains the 8.5:1 pistons, and uses the turbo to maintain 30" MP for the same torque/ICP as 43" in the turbo, allowing it to run cooler both at the turbo, and in the charge air, allowing even greater altitude and more margin from detonation.

So there s a relationship with MP/RPM that down low and running hard, if you 'over square' even a NA engine hard enough, especially the ones with 9:1 and higher CR, you can get yourself into a condition where you can get into those spontaneous combustion realms which is the basis of 'detonation'.

That's the real reason you want to keep CHTs below 380°, your not in detonation territory with a stable 380°.