how soon after take off.....

[D SQDRN 97th IOTC]

do you throttle back from full power to climbing power?

and does it depend on what you are in?

[IO540]

The SOP with a piston is to climb with all 3 forward until top of climb, then trim to cruise speed, and when that is reached, set power for cruise.

There are various refinements, applied when climbing to reasonable altitudes e.g. transition to a +500fpm cruise climb (engine leaned for cruise) if that gives adequate engine cooling. One can even apply the Deakin constant-EGT method where one leans to keep a specific cylinder at a constant EGT all the way up; that gives you a constant CHT all the way up and fuel savings.

One has to transition to some sort of cruise climb anyway at about 12k ft otherwise the engine will be too rich.

[Shunter]

When I learnt in a 152 with 2 POB it was a case of full power for the climb. That's a bit overkill most of the time in the 177 so I tend to throttle back to 25 square about 1000agl and that gives a nice 700fpm @ 95kt.

Have a look in your POH, they're usually quite informative.

[Runaway Gun]

Definitely not before 500ft. A fair proportion of engine failures happen when changing the power, so it's best to think of a possible 'worst case' scenario.

[foxmoth]

The SOP with a piston is to climb with all 3 forward until top of climb

True for many types, but not all by any means (especially mixture if operating hot and high), many types you bring the power back for noise even if not for engine considerations - check the POH for the type you are flying!

[Tall_guy_in_a_152]

The SOP with a piston is to climb with all 3 forward until top of climb
Probably true for traditional Lycomings and Continentals, but not modern units like Rotax which are higher reving.

It's a few years since I was current in a DA20, so cannot recall the numbers, but the revs were reduced at 500 feet.

[gcolyer]

In a conventional single I only throttle back when I am ToC.

If I am flying the PA32 I will lean up and reduce manifold pressure after a couple of hundred feet and cruise climb to ToC. I know it does not tell me to do that in the POC but it does save on the fuel burn. I do the same in a twin.

[waldopepper42]

Depends entirely on what's appropriate for type. In the Slingsby, I would reduce MAP and RPM and lean at c.1500'. In the Extra, it's pretty much as soon as stable in climb (c.200')!

[moonym20]

I think that mostly applies to standard training aircraft with fixed pitch props.

in the likes of a cessna T210 if i remember rightly SOP only allows for 5 minutes at max power setting before resetting throttle/prop for a climb power setting (26/26 160lbs ff ... i think :O)

[IO540]

I tend to throttle back to 25 square

Does the POH suggest this? Presumably this is at full rich otherwise you might get into the detonation region.

A fair proportion of engine failures happen when changing the power

I think that is an OWT, but it has been doing the rounds of pilot forums for years.

This debate could get into engine management issues, all over again :)

[Runaway Gun]

An OWT? Not sure what that is, but I guess it means an unsubstantiated statement? Fair enough - I cannot prove it, just what I had passed onto me, and I figured it couldn't hurt to follow. Just a Professional Rumour :)

[SATCO Biggin]

Depends on type and POH advice but in the Yak52 as soon as possible to save fuel.:eek:

[Chilli Monster]

If it's a fixed pitch 160/180HP lycoming then it gets left fully forward until top of climb as IO says. However, anything bigger, with a Variable pitch prop then reduce not before 500ft when established in the climb.

The "All 3 fully forward until top of climb" statement really concerns me - both the IO360, IO540 and I'm pretty sure the TIO-540 (the 3 piston engines I mainly fly) all have a "Max RPM limit" of 5 mins. This, plus noise abatement, means I come back to 25/2500 (IO360 & IO540) and 30/2500 (TIO-540) once above 500ft and established in the climb.

[Insane]

What happened to the simple "Top Of Green" for the Climb?

[Shunter]

I tend to throttle back to 25 square

Does the POH suggest this? Presumably this is at full rich otherwise you might get into the detonation region.
Yes. Cruise climb is listed as 23-25", 2500rpm. For the same speeds, 23" gives 500fpm, 25 gives 700fpm. POH states to begin leaning as you climb through 3000ft.

[IO540]

OWT - old wives tale.

both the IO360, IO540 and I'm pretty sure the TIO-540 (the 3 piston engines I mainly fly) all have a "Max RPM limit" of 5 mins

Not mine (IO540-C4D5D)

[Chilli Monster]

I stand corrected - mine's a C4D5D too which has max cont 2575. (The Arrow I still own has the max figure placarded though)

However - I think I'll stick to throttling back in the climb. That 92l per hour figure on the digital flowmeter when everything goes forward really un-nerves me ;)

[Basil Smallpiece]

Depends when and where - in the school Baron from a noise sensitive airfield we got it back to 25/25 as soon as possible; now with the ULM/Rotax I take off at firewall/58 and reduce to 24/52 at 500ft because I'm now paying for the engine servicing and I can safely fly a complete deadstick circuit from that altitude...

[bookworm]

Does the POH suggest this? Presumably this is at full rich otherwise you might get into the detonation region.

Why would 25"/2500 put you in the "detonation region" when FT/maxRPM wouldn't?

I come back to FT/2400 (2 x IO-320) at a few hundred feet and leave it there to ToC, leaning for a specific EGT or below, and monitoring CHT carefully.

Having tried it both ways, I've found that a higher power, higher airspeed regime tends to keep the CHTs lower than reduced power, lower airspeed. I think the difference between 2400 and max RPM is relatively small in terms of power, but significant in terms of noise and possibly temperatures, though I haven't been very scientific about the latter.

If I were in a single, I would consider leaving it at max RPM for rather longer.

[HAL-26]

Flying behind a 60+ year old engine most of the time (either Gipsy Major or Walter Mikron), as soon as I feel comfortable about the rate of climb, its back 100 rpm or so, to give the old ladies a bit of a rest!

[Islander2]

Why would 25"/2500 put you in the "detonation region" when FT/maxRPM wouldn't? My engine, a Continental IO-550, has full throttle mixture enrichment. I believe this to be a feature of many other aero engines, especially the 6-cylinder variants. A reduction from FT to 25" near to SL causes a significant increase in CHTs which, if the engine is poorly cooled as it is on my A36 Bonanza, could move the engine into the detonation region.

Likewise, a reduction in RPM from max to 2500 causes the CHTs to rise, other things being equal. This is not so significant as the loss of full throttle mixture enrichment and, for me, is SOP for noise considerations, but it does reduce the detonation margin.

[Chilli Monster]

I'm probably missing something here but, if you reduce the power, but leave the mixture alone - how does that cause the CHT's to rise?

[Miserlou]

When I flew the Cardinal, the climb power was set as soon as landing back was not an option or between 400 and 800'. This included leaning the mixture.

I believe the failure at change of power statement to be at least rooted in fact though may refer more to jet engines due to the air flow and pressure changes.

I do know of a couple of instances of 'failure at thrust/power reduction'.

[DubTrub]

..as soon as I feel comfortable about the rate of climb, its back 100 rpm or so, to give the old ladies a bit of a rest!
Not always a good idea, the full throttle setting ensures maximum fuel flow for cylinder cooling in the slow-flight high-power condition.

[FullyFlapped]

in the likes of a cessna T210 if i remember rightly SOP only allows for 5 minutes at max power setting before resetting throttle/prop for a climb power setting (26/26 160lbs ff ... i think )

Mine (TSIO-520) has a 5 minute limit at max grunt (310HP), then it's back to 30/25, 126 pph for normal climb, or 35/26, 162 pph for max perf climb.

FF :ok:

[S-Works]

In my Cessna I have a Rolls IO360K. Fly it fire walled and start to lean as I climb, top of the climb I set cruise and don't touch anything again until ready for the descent. I pull the throttle back an inch at a time and turn height into speed. Mixture gets fed back in slowly at the bottom of the descent.

[IO540]

That 92l per hour figure on the digital flowmeter when everything goes forward really un-nerves me

That is correct for the 100% power setting - this is an intentional setting on the fuel servo. The factory minimum spec is 83L litres/hour.

The over-rich mixture is required to keep the CHT down to a reasonable level, for an engine which is otherwise unable to dissipate the heat that's generated. This is a feature, AFAIK, of all common air-cooled Lyco/Conti engines, and is necessary if running at the certified 100% power setting.

Nobody should fly in cruise at 100% power, but your TB20 should pull about 165kt IAS at 1500ft if you left it like that for a few minutes.

Once in cruise, you can set 75% or lower power, and lean to peak EGT, or LOP.

The max rpm setting is necessary for 100% power. One isn't going to get the spec'd 100% power (itself required to achieve book values for takeoff performance) unless going to max revs.

The C4D5D safe operating area chart (you have to buy the Lyco engine manual to see this but I have a copy online) has a little nick in one corner which requires a min rpm when above a certain MP. This, apparently, is due to a stress limitation on the crank, just behind the prop flange.

The max rpm setting is also useful for reasonable altitudes. At say FL180 you will want every bit of air you can get into the engine, and the more revs, the harder it sucks.

I am not sure whether the OP posted his two-liner to start off this debate ;)

[bookworm]

My engine, a Continental IO-550, has full throttle mixture enrichment.

Yes good point, I'd forgotten about that.

The over-rich mixture is required to keep the CHT down to a reasonable level, for an engine which is otherwise unable to dissipate the heat that's generated.

I rather like a line that came from one of Peter Garrison's articles in Flying many years ago. He commented that as a fluid for engine cooling, fuel is cheaper than perfume or wine, but represented poor value compared to air. Experience with the CHT instrumentation appears to confirm that an extra 10-20 knots of airspeed is equivalent to a great deal of extra fuel flow. Of course if you really need the optimal rate of climb, you'd better fly at Vy and firewall the mixtures. But that's not a common requirement.

Many of these trade-offs are dependent on the aircraft, engine, cowling etc. I don't think there's a one-size-fits-all answer.

[chevvron]

With Rotax 2-strokes, I find pulling back the throttle not below 500ft agl on climbout 'til you see a drop in rpm, then edging it slightly forward again, does nothing to r.o.c. but does wonders for fuel consumption.

[IO540]

Experience with the CHT instrumentation appears to confirm that an extra 10-20 knots of airspeed is equivalent to a great deal of extra fuel flow. Of course if you really need the optimal rate of climb, you'd better fly at Vy and firewall the mixtures. But that's not a common requirement

I agree.

If I was doing a really long flight, the sort where you check the Shadin FOB against the plog budget at every waypoint, then I would climb at 100% power to 500ft, then set 60% power and cruise climb at that setting, leaning for peak EGT as I climb, at about 300fpm; about 120kt.

One should notify ATC if IFR and unable to hold 500fpm ;)

I have planned a direct flight to Corfu (LGKR) and will do it one day. It will need a ~20kt average tailwind though to achieve the legal FAA IFR reserve...

More commonly, one wants to climb at max fpm, to get above the cloud and ice. This does want all 3 fully forward, until power drops off to about 75%, and then (this happens at v. roughly 8,000ft) lean for about 100F ROP and adjust the pitch for an airspeed which keeps the CHT below 400F.

[Islander2]

I'm probably missing something here but, if you reduce the power, but leave the mixture alone - how does that cause the CHTs to rise?Reduction in MP from FT of course does mean lower power, but it also means loss of full throttle enrichment and therefore a reduction in the excess fuel available for cooling ... in consequence, CHTs rise significantly.

Reduction in RPM from max also reduces power, of course, but the effective timing of the combustion event is advanced, with peak ICPs at maybe 14 deg ATDC (2500 RPM) compared with, say, 17 deg ATDC (2700 RPM) ... ICPs and CHTs both rise as a consequence.

Both of these phenomena are readily demonstrable with an EDM-700 or equivalent.

[englishal]

My method is:

Fixed pitch, firewalled to top of climb
Simple complex ;) Curise climb once at 500' (25/25)
Turbo charged complex (eg Seneca), cruise climb at ~31" MP once at 500'
FADEC - reduce to 90% power at 500' and transition to cruise climb :)

But it does tend to depend on the situation, i.e. what climb gradient is needed.

[bookworm]

IO540, I think you paint a picture of a choice between two extremes. I have no difficulty achieving a reasonable RoC, airspeed, set of CHTs and more modest fuel flow by leaning for about 200 degF RoP in a cruise climb. The CHTs are actually considerably lower than in a peak EGT cruise.

[Islander2]

My method is:
Simple complex ;) Curise climb once at 500' (25/25)Which is as taught by most instructors over generations, but the vast majority of them had no idea what that power reduction does to detonation margin. With the advent of affordable multi-cylinder engine analysers, the evidence is now there for all to see.

Our naturally-aspirated engines generally have quite a large detonation margin. However, pick one of the more detonation-prone engines in an installation that's marginal on cooling air (and the Continental IO-550/A36 combination is a good example), then add-in ambient temperature>>ISA, slavish abide by the POH to climb initially at Vy (or worse still, Vx) ... and you have all the ingredients for some damaging detonation if you follow the common practice of reducing to 25/25 shortly after a low altitude take-off.

In many 6-cylinder piston aeroplanes, it really is quite bad advice.

[G-KEST]

In the interests of both noise abatement and fuel burn I reduce power in our Lycoming IO-360 powered Skybolt to 2500 RPM/25" MP at around 25 feet or less after takeoff. 25/25@25........!!!! If the engine did fail, and it has not in the 10 years of operating the aeroplane, then I have sufficient room to land ahead either on the paved runway or, if that is short, within the airfield boundary in order to ease the RFFS access and response time. Safety first - however I never taught that technique to anyone while instructing for some 39 years.

Cheers,

Trapper 69
:cool:

[englishal]

If the engine did fail, and it has not in the 10 years of operating the aeroplane, then I have sufficient room to land ahead either on the paved runway
What a bl@@dy good idea ;)

[IO540]

I have no difficulty achieving a reasonable RoC, airspeed, set of CHTs and more modest fuel flow by leaning for about 200 degF RoP in a cruise climb

Yes, this is what I referred to when I wrote

One can even apply the Deakin constant-EGT method where one leans to keep a specific cylinder at a constant EGT all the way up; that gives you a constant CHT all the way up and fuel savings.

I have used this; the CHT is about 400-420F, whereas climbing with all 3 fully forward gives me a significantly lower CHT; nearer 370F. Both are OK but IMHO the "clever" one is hardly worthwhile for usual GA messing about. I would use the constant-EGT method for an airways flight when one is climbing nonstop (hopefully) to say FL100-150.

[mm_flynn]

Interesting,
As an io-550 A36 driver with what appears exceptional cooling. I shove full throttle at the start of the take off roll and start pulling it back a bit when I start my decent. (cruise CHT 300 at 15 gph (US) 2500, 350 at 15.5 2200), dial a couple 100 rpm off at 500 feet for the neighbours and go to LOP when I get all cleaned up or my first level off point. Coming back from Venice, did the whole climb to FL140 as a LOP cruise climb (380 is where the alarms are set - 120 kts and about 500 fpm) in ISO +20 weather and had lower temperatures, better mpg but 10 minutes longer in the climb than a ROP climb.

[IO540]

I shove full throttle at the start of the take off roll and start pulling it back a bit when I start my decent

I concur and do the same, but we are talking of airways-level flights, with a non-turbo engine.

[Cusco]

In our Hershey Bar Arrer(IO 360) , I pull back to 25/25 at 500ft and further to 24/24 when I reach cruise altitude.Don't lean till I reach cruise altitude, using EGT gauge as my guide..........that's about as sophisticated as it gets.

I too have the 'don't thrash it for more than five minutes ' aphorism in the back of my head , but have no idea where it came from: it's certainly not written down anywhere.............. mebbee an old instructor drummed it into me once long ago.

Safe (and economical) flying.

Cusco;)

[Chilli Monster]

I too have the 'don't thrash it for more than five minutes ' aphorism in the back of my head , but have no idea where it came from: it's certainly not written down anywhere..............

The Arrow IV (same engine) it's actually placarded next to the RPM gauge.

[High Wing Drifter]

Cusco,

The timed limit relates specifically to turbo-supercharged engines that utilise high boost values and RPM values for take-off/go-around. The limitation is invariably in the FM/PIM/POH. For example the turbo Seneca 3 use up to 40" and 2800rpm. Pull the RPM back to 2600 with 40" for maximum continuous power (MCT).

The quoted best rate/angle of climb for the Seneca 3 is for MCT. I power back when cleaned up.

The Seneca 1, on the other hand is normally aspirated and there is no limit. But for some reason I was told to reduce to 25"/2500 after t/o during my checkout. I mean to get to the bottom of this, because as per previous posts, my understanding is this would do more harm than good!

[mm_flynn]

..but we are talking of airways-level flights, with a non-turbo engine.

Which makes maintaining max available MP even more important. Easing back on the RPM is going to be better for the engine and bystanders and less harmful on airspeed/climb rate than reducing manifold pressure - when you are going to have to open the throttle again in a few minutes as you continue to climb. For airways work, turbonormalised or normally aspirated engines able to run LOP, should just have the throttle left all the way forward until descent.

On an injected/ CS setup you can get any power down to about 50% with just mixture and prop settings.

[cblinton@blueyonder.]

This is the Bonanza theory.


The conventional wisdom is, that once obstacles are no factor, reduce RPM to 2500 and climb at full throttle. Full throttle enables the mechanical fuel enriching feature to keep CHT's cool during takeoff and climb. As always lean as necessary for high density altitude take offs and during the climb.

[Gingerbread Man]

I tend to throttle back to 25 square

Does the POH suggest this? Presumably this is at full rich otherwise you might get into the detonation region.

I was taught this a few weeks ago doing my FAA multi in a PA44. I assume the instructor wouldn't have been leading me ashtray.

[Islander2]

I was taught this a few weeks ago doing my FAA multi in a PA44. I assume the instructor wouldn't have been leading me ashtray.My experience over the past thirty years is that very, very few instructors and examiners have any real understanding of piston engine management. Mostly, they haven't got a clue, and merely perpetuate various OWTs.

Much of what I've been told to do over this time has been plain wrong, sometimes with advice that would be near certain to reduce the engine TBO.

I think there are two main reasons for this:

1. Lack of data

Until fairly recently, there has been precious little factual information available. Neither Lycoming nor Continental have produced much in the way of data-based operational guidance, and POH's have been near to useless since engine life has been way down the airframe manufacturer's priority list after marketing hype to claim superior performance and legal editing for backside protection. Kas Thomas and TBO Advisor produced some good material in the 1980's, but I don't believe it was widely read.

Then along came Busch, Deakin et al and, thanks to the www, a wealth of really good information is now available to those who care to seek it out. Most importantly, their efforts have been supported by George Braly, who has made available loads of invaluable, hard-data information from the engine test stand at GAMI, together with the advent of economical multi-cylinder engine analysers that have enabled many of us to see with our own eyes that much of what we've been taught is a load of b*ll*cks.

2. Hard-up instructors!

The economics of flight instruction, including the more advanced CPL, ME, IR, etc, dictate that instructors with experience of owning complex light aeroplanes are in a tiny minority. I believe that very few 6-cylinder engines make it to TBO without substantial top-end expenditure, and being the person that's going to pay for those expensive cylinder overhauls and replacements provides a great incentive to go the extra mile in learning how to make the cheque-writing events less frequent!

[IO540]

Islander2 is right. Most instructors in the UK haven't got a clue about engine management. In fact I have never met a single one who had a clue.

Easing back on the RPM is going to be better for the engine and bystanders and less harmful on airspeed/climb rate than reducing manifold pressure

Firstly, I have never seen evidence that lower RPM is really better for the engine. I would think it would be, as would most people. But if an engine is running at a given fuel flow, and is set to peak EGT or LOP (when the power generated is proportional to the fuel flow) the power output will be more or less fixed. So, if you drop the RPM with the RPM lever, the CSU sets the prop to a coarser pitch (in order to absorb the available power into the prop) and the stress on the crankshaft and con-rods increases. Now, which is better - lower RPM or lower stresses? I think it's a good question. A lot of engine stresses, particularly crankshaft stresses, are of dynamic origin i.e. are caused by the inertia of various parts rather than by the stresses of combustion. But if something is actually going to break, it will break through stress, not through any velocity of the component involved.

Secondly, one can't separate revs from power output, once in the airway levels. The engine is an air pump. When the inlet valves close, and the combustion starts, that process is isolated from the air pumping side, but any deficiency in the air pump means less air going in, and the need to maintain the right A/F ratio means less air = less fuel = less power. So for max power you need max revs, end of story. Particularly if the MP is down to b*gger-all, at FL160, you want max revs. A fully opened throttle just lets the air in, which is good, but if the engine can't suck, the air won't get in. If you reduce the RPM, you will get less power.

[mm_flynn]

As this is drifting well into engine management vs. when to pull power off after take-off, I thought a separate thread would make sense thread (http://www.pprune.org/forums/showthread.php?p=3491278)