Full rental power

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Johann

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Johann
So what is it?, how do you set it up?
For a specific example, let's say a Cessna 172.

I've seen it mentioned as throttle to the firewall. Now, If I'm flying, say, at 4500, I put the throttle all the way in and keep it level, it seems like the engine will go to red line, and maybe even past it. Is this not so?

Do you still lean as not to foul the plugs?

And more important, is it damaging to the airplane or is it just not wise from a fuel economy perspective?
 
Run the plane according to the POH - this whole concept of "rental power" is so stupid because it hurts everyone. Running it too hard, using too much fuel, increasing wear = increased operating costs means the school MUST charge you more or you're not going to have a plane to fly. Remember you are trusting your life to this thing, so why abuse it?
 
Johann said:
So what is it?, how do you set it up?
For a specific example, let's say a Cessna 172.

I've seen it mentioned as throttle to the firewall. Now, If I'm flying, say, at 4500, I put the throttle all the way in and keep it level, it seems like the engine will go to red line, and maybe even past it. Is this not so?

Do you still lean as not to foul the plugs?

And more important, is it damaging to the airplane or is it just not wise from a fuel economy perspective?
Click to expand...

Lean to 125°ROP and pull the throttle to red line.
 
Full rental power = highest power consistent with limitations.

In a 172, that's 65% power when leaned, and under redline. Preferably "in the green."

If you're climbing like that, particularly at slow speed, watch the CHT.
 
mrkbbd said:
Run the plane according to the POH - this whole concept of "rental power" is so stupid because it hurts everyone. Running it too hard, using too much fuel, increasing wear = increased operating costs means the school MUST charge you more or you're not going to have a plane to fly. Remember you are trusting your life to this thing, so why abuse it?
Click to expand...

It's pretty much just curiosity. I usually run at the highest setting in the POH at most.
I never took a trip long enough where a couple of knots would make a difference.
 
MAKG1 said:
Full rental power = highest power consistent with limitations.

In a 172, that's 65% power when leaned, and under redline. Preferably "in the green."

If you're climbing like that, particularly at slow speed, watch the CHT.
Click to expand...

So it would be the highest figure for cruise setting in the POH?
At lowish altitudes it goes higher than 65%, usually around 75%, so how would 65% power be better?
 
Not that I am recommending it, but full mixture, full prop, full throttle. And then start pulling the mixture back for best power... If you are over POH figures for MP/RPM then you need to get more altitude, or you are in fact running full rental power....


But, most people just run rentals at 75% per the poh, as to minimize time on the Hobbs, and maximize KTAS.
 
Johann said:
So it would be the highest figure for cruise setting in the POH?
At lowish altitudes it goes higher than 65%, usually around 75%, so how would 65% power be better?
Click to expand...

You're right. It's 75% for a 172, at least for an N model. That number does vary from model to model (but it's probably 75% for all 172s).

The reason for that is risk of detonation. Light detonation will not blow the engine up instantly, but it will accumulate damage to piston heads and rings, and cause an excess of heat that could be more serious.

Above a certain altitude, the engine will not make 75% power at the redline. That means you can safely cram the throttle to full, until you descend.
 
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mrkbbd said:
Run the plane according to the POH - this whole concept of "rental power" is so stupid because it hurts everyone. Running it too hard, using too much fuel, increasing wear = increased operating costs means the school MUST charge you more or you're not going to have a plane to fly. Remember you are trusting your life to this thing, so why abuse it?
Click to expand...
:yeahthat:

I fly a rental as if it were my own so I wouldn't know what this "rental power" is that you speak of.
 
Johann said:
At lowish altitudes it goes higher than 65%, usually around 75%, so how would 65% power be better?
Click to expand...

Ask the owner of the airplane, he/she will give you a direct, concise explanation which might include info on burned exhaust valves, $6.00/gallon avgas, etc.
 
Aeric said:
One of many reasons why I took my airplane out of leaseback a long time ago after a short time...
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I don't understand why FBOs don't charge dry tach rates for that reason. That would give a financial incentive to take it easy. You get best fuel mileage per tach hour slow.

CAP's self-funded missions are like that. They charge a dry tach rate to cover maintenance, and you're expected to return the aircraft with the fuel at the tabs. Which is nice because CAP missions are usually done at 90 KIAS at low altitude, in 182s or 206s (mostly 182s).

And they seem to always be in better shape than rentals, and some of them have significant age on them.
 
Aeric said:
Ask the owner of the airplane, he/she will give you a direct, concise explanation which might include info on burned exhaust valves, $6.00/gallon avgas, etc.
Click to expand...

Would probably say run it per the POH.
And the main reason I ask is because the POH actually has numbers all the way to 50 RPM below redline. And when putting it there (which is legal and is within the limitations, although it's not best economy), the throttle is not even almost at the firewall.

So my guess is that for an airplane like a Cessna 172, full rental power = highest power setting in the POH.
Again, my question was because I couldn't understand the whole "throttle to the firewall" thing, but I assume maybe that works with CS props for example.

I'm not going to run the thing above the limitations, I'm inside it! (and it would save me a minute at most) :hairraise:
 
Doesn't work for CS props either. Those have a redline RPM, and a "top of normal" MP. E.g., 23 inches for some 182s (that varies across models). Some turbocharged engines have a "do not exceed" MP, and really bad things happen if you do (severe detonation). If I remember right, a Cessna 206 must keep the MP below 40 inches at all times, or the fuel delivery cannot keep up with it.

You won't redline a 172 in a climb with the throttle to the firewall, even at sea level. You might, however, redline the oil temperature or CHT for a sufficiently steep climb (Vx).
 
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MAKG1 said:
I don't understand why FBOs don't charge dry tach rates for that reason. That would give a financial incentive to take it easy. You get best fuel mileage per tach hour slow.
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Two reasons. First, tach time generally is less than hobbs, so you need to charge a higher rate per hour. Though many pilots are savy enough to realize this, many are not--and if your prices look to be 15% higher to prospective students you don't get as much business.

Second, pattern work involves a lot of wear on a plane with relatively little tach time being used, so Hobbs better builds up reserves for tires, brakes, and other items that get the crap beat out of them by student pilots.

Flight clubs, on the other hand, that have experienced pilots and don't do much training, often rent by tach.
 
MAKG1 said:
Yes, but that's the altitude speaking.

You couldn't make 75% power at that airport. No way.
Click to expand...

Right if I stay on the east side I can't make 75% and if I cross the Sierra, on the return trip the first 20 minutes are climbing to 10,000'.

I do pull power for 500fpm descents rather than speeding up. I find extra speed in descents usually means a bumpy ride especially in my CT.
 
I appreciate someone making a rental aircraft available, and try to take care of it as if I owned it.
 
Johann said:
So it would be the highest figure for cruise setting in the POH?
At lowish altitudes it goes higher than 65%, usually around 75%, so how would 65% power be better?
Click to expand...

The O-320 has no problem running 100% power all day long.
 
I have never heard of Full Rental Power before, and this concept kinda bothers me.

I rent and try to treat the airplane as gently as I can. Like I would do if I owned it.

It bothers me that other renters may not be doing the same. I am trusting my life to this thing! I am very surprised that some pilots would mistreat an airplane, just because they don't own it.

It ain't a rental car!
 
I disagree with some of the sentiments. FRP might burn a lot of gas, increasing the costs for wet-rental rates overall, I disagree that running a legal max continuous power is "bad for the aircrarft". There is not some "fixed number of revolutions" in an engine before overhaul is necessary. The two things that kill 172 engines are operating temperature and disuse. Keeping the baffles and such in good shape and regular flying will make it last longer than flying it around at 50% power all the time. You can do more damage for a carb'd lycoming by keeping it at a reduce power setting in high temp situations than by leaving the black knob jammed all the way in.

Our 172 rentals typically well exceeded TBO times. Something that someone who typically "owns one" but flies it less than 100 hours a year can say.
 
So to recap full rental power is throttle wide open or RPM at redline?

And operating at 75% power according to the POH data is just "performance cruise" and definitely not bad for the engine?
 
Always treated the rentals like it was my own plane.........but would run at fairly high power. We were flying some high time stuff down here in SoCal, reportedly a couple of the 172's were still going at 3,000 hours on the mills.......and they ran fine.
 
cowman said:
So to recap full rental power is throttle wide open or RPM at redline?

And operating at 75% power according to the POH data is just "performance cruise" and definitely not bad for the engine?
Click to expand...

Well first, never exceed redline, it's red for a reason.

Second, remember that the POH is a compromise between engineering and marketing, what settings to get the best range / speed mix out of the airplane to compete with other airplanes, not what is necessarily best for the any one component. When most GA airplanes were built, they never imagined they would still be around today...

Run within the limitations set by the POH - definitely not bad for the engine is relative - the POH is written for ideal conditions, watch temps (keep CHT under 400) and lean appropriately. Also, running the engine at the top of the performance chart makes for an uncomfortable ride and only gaining 1 or 2kts, so it really isn't worth it. In a 172, 2400-2450 is probably about as high as I would cruise it (assuming a 180hp lyc with a 2700 RPM redline).
 
I have an Archer with a 180hp lyc and 2400-2450 is pretty much where I cruise it at.

There's a chart on my sun visor that rows for altitude and columns for power and gives you an RPM. I usually target it right around the 70%.
 
Johann said:
So what is it?, how do you set it up?
For a specific example, let's say a Cessna 172.

I've seen it mentioned as throttle to the firewall. Now, If I'm flying, say, at 4500, I put the throttle all the way in and keep it level, it seems like the engine will go to red line, and maybe even past it. Is this not so?

Do you still lean as not to foul the plugs?

And more important, is it damaging to the airplane or is it just not wise from a fuel economy perspective?
Click to expand...

Always lean when operating at less than 75% power...not just for the plugs (that's more of a taxiing thing) but for fuel efficiency. If you ever leave the pattern to go somewhere, you want to achieve as close to book fuel burn as possible, and that means leaning the mixture.

Bob Gardner
 
Whats the difference between a rental car and a four wheel drive?
The rental will go anywhere!

Prudence dictates that this rule should NOT be applied to aircraft rentals,
Or sooner or later some poor schmuck will be off roading after the premature power plant failure.

Fly it like you want your kid brother to drive your new car.


Sent from my iPad
 
ja_user said:
But, most people just run rentals at 75% per the poh, as to minimize time on the Hobbs, and maximize KTAS.
Click to expand...


Hobbes is usually running when he prop is spinning. No amount of power reduction is going to warp time on a Hobbes. Tach, well that's another story.
 
I run an Archer II 100 rpm below redline. I don't lean because I rarely go much higher than 2,000 AGL in it. If I lean it, I'll run the engine temps through the roof. I'd rather burn gas than ruin an engine.

Cheapest 120 kts (true) I can find right now.
 
Unit74 said:
Hobbes is usually running when he prop is spinning. No amount of power reduction is going to warp time on a Hobbes. Tach, well that's another story.
Click to expand...

I think he meant renters who are on a trip will minimize hobbs time by flying as fast as possible.
 
I faced this back when I was flying Cirruses.

Mine got operated nearly exclusively LOP.

Roughly, I could go about 172k on 13.5 gph LOP or 180k on about 18gph ROP.

4.5 gph more for 8 kts more speed that took at most 10 minutes off an average flight made absolutely no sense to me. Felt unnatural the few times I tried it to hurry a flight along.

But some Airshares owners were not pilots, and I'd be hired to fly them places. They were paying for plane and pilot by the hour, so "Full Rental Power" made sense, and I flew them that way - ROP but always at settings approved in the POH for continuous operation.

I would not fly my plane that way, but don't think it was either irrational or unsafe to do it when called for.
 
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I'd argue FRP is good for the engines. We frequently got 2-3x TBO on ours, and nobody was putting a lace doily on the mixture knob and treating it "like it was their own"

Hell, our 300k skyhawk had someone leave a half-eaten snickers bar on the back seat, melting into the new leather -- on her 4th flight.

Run em, they're made for it. :)
 
Melting said:
Whats the difference between a rental car and a four wheel drive?
The rental will go anywhere!
Click to expand...

:rofl::rofl::rofl: That's no lie, I followed the Pink Jeeps through the trails around Sedona with a Ford Escort from Hertz.:lol:
 
schmookeeg said:
I'd argue FRP is good for the engines. We frequently got 2-3x TBO on ours, and nobody was putting a lace doily on the mixture knob and treating it "like it was their own"

Hell, our 300k skyhawk had someone leave a half-eaten snickers bar on the back seat, melting into the new leather -- on her 4th flight.

Run em, they're made for it. :)
Click to expand...

I agree completely with any aircraft engine that is rated at .5hp/CI. Once you get to .75hp/CI, you have to be more cautious with a direct drive engine, that's why gear drives are advantageous as they reduce the ICP required for the HP moving them further from detonation and giving you a safety margin. ICP is the destructive force in an engine.
 
For me, Full Rental Power is = max power per the aircraft POH. If it's redline, it's redline. If it's 2400, so be it. I absolutely fly it like a rental if I'm renting wet. If I save 10 minutes on each leg of a flight, great. That's less cost I have to pay and I have no incentive to save fuel. It isn't abusing the aircraft in any way because it is approved per the manufacturer. If the FBO/rental company has other restrictions, then those take precedent.

Now, flying at full throttle when the POH stipulates a reduced power setting is abuse and shouldn't be done except in an emergency.
 
RalphInCA said:
I have never heard of Full Rental Power before, and this concept kinda bothers me.
It ain't a rental car!
Click to expand...

Ha! I used to belong to an equity club, and you should see how some pilots treated those planes! BALLS TO THE WALL was how most of them typically flew the plane.
 
I always treated rental airplanes as if they were my own. Follow the POH.
 
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