c172R climb performance

jspilot

jspilot

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jspilot
Today the FBO where I rent from switched my flight last minute into a 172R model. I was previously flying mostly 172P's. I was checked out in the R model so no big deal.

Everything checked out on pre-flight but then I took off and started to climb out. The plane was struggling to climb big time. The RPM's were reading only 2100 and I was barely getting 500 feet per minute climbing out at around 80 knots. Even when I pitched up to 70 I still barely got any improved climb. It was just me in the plane, full fuel and it's about 80 degrees here today so it's not like conditions were terrible for climbing or we were over loaded.

I did not feel comfortable and pretty soon I just made a reverse course back into the airport and landed. So my question is, is this normal for the 172R? Are they that bad of climbers or was I having some sort of an engine issue? I was not taking a chance and am fine with my choice either way.
 
jspilot said:
Today the FBO where I rent from switched my flight last minute into a 172R model. I was previously flying mostly 172P's. I was checked out in the R model so no big deal.

Everything checked out on pre-flight but then I took off and started to climb out. The plane was struggling to climb big time. The RPM's were reading only 2100 and I was barely getting 500 feet per minute climbing out at around 80 knots. Even when I pitched up to 70 I still barely got any improved climb. It was just me in the plane, full fuel and it's about 80 degrees here today so it's not like conditions were terrible for climbing or we were over loaded.

I did not feel comfortable and pretty soon I just made a reverse course back into the airport and landed. So my question is, is this normal for the 172R? Are they that bad of climbers or was I having some sort of an engine issue? I was not taking a chance and am fine with my choice either way.
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Sounds a lot like the 150 horse 172 vs 150 horse 177, thing, (full of gas the 177 has 72 pounds more fuel on board) which climbs better?
 
R model is kind of a pig comparatively. Look up your static RPMs in the book and run up to max power and see if it's making the book numbers. If it's not, then something is amiss. If it is...well...sorry about your luck. From your description, it kind of sounds to me that what you described is what you get performance wise out of an R model.
 
Arbiter419 said:
R model is kind of a pig comparatively. Look up your static RPMs in the book and run up to max power and see if it's making the book numbers. If it's not, then something is amiss. If it is...well...sorry about your luck. From your description, it kind of sounds to me that what you described is what you get performance wise out of an R model.
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Thanks. Yeah I was not getting a rough running engine or anything but compared to the P model which routinely get's 1000 feet per minute on these kinds of days, I was nervous. I have to say, the R model is nice in some ways like the updated panel, but to tell you the truth, give me a P model any day. The 160 Horsepower engine with that amount of fuel ( 53 gallons usable vs 40 gallons) is just creating a very under powered plane.
 
What are the book performance numbers for one versus the other at MGW?
 
jspilot said:
Thanks. Yeah I was not getting a rough running engine or anything but compared to the P model which routinely get's 1000 feet per minute on these kinds of days, I was nervous. I have to say, the R model is nice in some ways like the updated panel, but to tell you the truth, give me a P model any day. The 160 Horsepower engine with that amount of fuel ( 53 gallons usable vs 40 gallons) is just creating a very under powered plane.
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53 gallons of fuel is 5 more gallons than the 150 horse 177.

The 1966 172H was 145 horse with 36 gallons usable (3 gallons unusable)

1968 Cessna 177 is 150 horse with 48 gallons usable (1 gallon unusable)

1981 thru 1986 172P is 160 horse with 40 gallons usable (2 gallons unusable)

172R is 160 horse with 53 gallons usable (3 gallons unusable)

I see a trend on why which is labeled doggy (when topped off with gas).
 
The R empty weight is probably >20 pounds heavier to boot. They were certified under newer regulations, including crashworthiness, more equipment like dual vacuum pumps etc.
 
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jspilot said:
Today the FBO where I rent from switched my flight last minute into a 172R model. I was previously flying mostly 172P's. I was checked out in the R model so no big deal.

Everything checked out on pre-flight but then I took off and started to climb out. The plane was struggling to climb big time. The RPM's were reading only 2100 and I was barely getting 500 feet per minute climbing out at around 80 knots. Even when I pitched up to 70 I still barely got any improved climb. It was just me in the plane, full fuel and it's about 80 degrees here today so it's not like conditions were terrible for climbing or we were over loaded.

I did not feel comfortable and pretty soon I just made a reverse course back into the airport and landed. So my question is, is this normal for the 172R? Are they that bad of climbers or was I having some sort of an engine issue? I was not taking a chance and am fine with my choice either way.
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How hot/humid was it? What was the DA? A hot summer day can really zap the strength out of a 172. I have seen it take an otherwise fine 172 and make it climb 500fpm.
 
jspilot said:
Thanks. Yeah I was not getting a rough running engine or anything but compared to the P model which routinely get's 1000 feet per minute on these kinds of days, I was nervous. I have to say, the R model is nice in some ways like the updated panel, but to tell you the truth, give me a P model any day. The 160 Horsepower engine with that amount of fuel ( 53 gallons usable vs 40 gallons) is just creating a very under powered plane.
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That is just 78 more pounds and if it was just you in the cockpit, is insignificant. Throw in a couple of heavy passengers then yes, that extra 78 lbs would be an issue. There could have been an issue with the engine causing it to underperform or it could have been due to the atmospheric conditions at the time or maybe you took off with only one mag on after run-up. Lots of possibilities but there is nothing doggy about the R versus the P.
 
SkyDog58 said:
That is just 78 more pounds and if it was just you in the cockpit, is insignificant.......Lots of possibilities but there is nothing doggy about the R versus the P.
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That's why they put a 180 horse in the 172S which holds the same amount of fuel as the 172R?

Almost exactly the same history as the 177.

177 with a 150 horse was labeled doggie so they put 180 horse in them and the fuel capacity increased by 1 gallon.
 
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bnt83 said:
That's why they put a 180 horse in the 172SP which holds the same amount of fuel as the 172R?

Almost exactly the same history as the 177.

177 with a 150 horse was labeled doggie so they put 180 horse in them and the fuel capacity increased by 1 gallon.
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never intended to create a match up between the 2 planes. I can confirm both magnetos were firing because I actually checked that as a possible culprit. Of note, prior to switching FBO's I had nearly 80 hours in a 172 SP. The R and SP are very similar in layout but the extra 20 horsepower makes an amazing difference as the SP's always got well above 500 feet per minute even in terribly hot humid days( way worse than today,) even with me and often someone else.

To answer a question from above, the DA was normal for this time of year around here and the humidity was low so again it just came down to the plane.

The truth is the poor climbout was not the only issue that made me turn around. The RPM's reading only 2100 was coupled into the decision.
 
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jspilot said:
never intended to create a match up between the 2 planes. I can confirm both magnetos were firing because I actually checked that as a possible culprit. Of note, prior to switching FBO's I had nearly 80 hours in a 172 SP. The R and SP are very similar in layout but the extra 20 horsepower makes an amazing difference.

To answer a question from above, the DA was normal for this time of year around here and the humidity was low so again it just came down to the plane.
The truth is the poor climbout was not the only issue that made me turn around. The RPM's reading only 2100 were coupled into the decision.
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Certainly might have been something weird going on. Was the fuel flow correct? Any sign of a partially plugged injector? The R is injected...
 
bnt83 said:
Certainly might have been something weird going on. Was the fuel flow correct? Any sign of a partially plugged injector? The R is injected...
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Fuel flow was reading above the green arc but that's normal in my experience during climb out.

I remember during my calculations before the flight thinking the R number's were really bad on climb out( taking up almost 1600 feet of runway at 30 degrees Celsius vs 900 something on the P to climb to 4,000 feet. So it's again very possible that nothing was wrong and just my inexperience in the model made it felt wrong.

I'm sticking to the P model from here on out. They charge more for the R anyway and aside from a nicer radio stack, the rest of the plane is just about not worth the extra 20 per hour they want for it.
 
Remember that the IO-360 in the R is derated from the basic same engine in the SP. It will turn slower. Even slower if pitched up for a 70 kt climb.
 
How can you be properly checked out without reading the POH?

From the 172R POH:
It is important to check full throttle engine operation early in the takeoff roll. Any sign of rough engine operation or sluggish engine acceleration is good cause for discontinuing the takeoff. If this occurs, you are justified in making a thorough full throttle static runup before another takeoff is attempted. The engine should run smoothly and turn approximately 2065 - 2165 RPM with mixture leaned to provide maximum RPM.
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So, 2100 RPM is normal for this aircraft.
 
MAKG1 said:
How can you be properly checked out without reading the POH?

From the 172R POH:


So, 2100 RPM is normal for this aircraft.
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Ok excellent to read. I have to say the check out was not complete and pretty basic. I'm glad nothing was wrong and the plane is fine. I'm also still very happy I turned back and came back to land. It's honestly not worth taking the risk.

Thanks for the input, it's exactly what I was hoping to get from this thread.
 
bnt83 said:
The R empty weight is probably >20 pounds heavier to boot. They were certified under newer regulations, including crashworthiness, more equipment like dual vacuum pumps etc.
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Add another zero, seriously.

If the tanks were topped off, that's almost 300 pounds more on the same HP.

What was the temperature and pressure altitude?
 
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dmspilot said:
Add another zero, seriously.

If the tanks were topped off, that's almost 300 pounds more on the same HP.

What was the temperature and pressure altitude?
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Very true. The restart model 172s are heavy birds...now take that 180 horse and put it on one of the old skinny airframes and you have yourself a very decent performing airplane.

Henning said:
Is there an STC to bring them up to 180hp?
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The conversion involves swapping props (and the paperwork associated with that) as far as I know.
 
dmspilot said:
Add another zero, seriously.

If the tanks were topped off, that's almost 300 pounds more on the same HP.

What was the temperature and pressure altitude?
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You weren't kidding. Found two clubs online and the empty weight difference between a P and an R was 172 pounds. :hairraise:

172 pounds higher empty weight plus 78 pounds more fuel when full of gas = 250 pounds.

No wonder there is a 180 horse conversion kit listed on the type certificate for the 160 horse R models.
 
MAKG1 said:
How can you be properly checked out without reading the POH?

From the 172R POH:


So, 2100 RPM is normal for this aircraft.
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Read that POH again. The RPMs given are for static, which is with the airplane on the ground and the brakes locked. In flight the forward speed will let the fixed-pitch prop turn faster than in static. 2300 RPM in the climb would be more like it. That engine needs looking at.

Dan
 
Dan Thomas said:
Read that POH again. The RPMs given are for static, which is with the airplane on the ground and the brakes locked. In flight the forward speed will let the fixed-pitch prop turn faster than in static. 2300 RPM in the climb would be more like it. That engine needs looking at.

Dan
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The first thing one looks at when RPM are not being made is the Tach itself, that's normally where the problem lies.
 
Guys I really appreciate the insight. In all honesty, 160 horsepower is really good on lighter 172's but I'm very surprised the larger tanked 172's came with this engine. It's just honestly underpowered. Like I said, I'm sticking to the P model as it seems truthfully like a great 172 model and probably only slightly behind the SP model I use to fly.
 
jspilot said:
Guys I really appreciate the insight. In all honesty, 160 horsepower is really good on lighter 172's but I'm very surprised the larger tanked 172's came with this engine. It's just honestly underpowered. Like I said, I'm sticking to the P model as it seems truthfully like a great 172 model and probably only slightly behind the SP model I use to fly.
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I may have missed it in the string of threads above, but what was the field elevation and what altitudes were you working at?

I flight instruct in a 172P ER model (50 gal) and with two adults on a 85 degree day with high humidity, I can normally squeeze out 600-650 fpm. The airplane not being clean by any means mind you (she needs a bath!).
 
2100 RPM seems low for a 172R on climbout. 2400 RPM is red line, and at full power you should be close to it; 2300 is about normal.
 
austinglasair said:
I may have missed it in the string of threads above, but what was the field elevation and what altitudes were you working at?

I flight instruct in a 172P ER model (50 gal) and with two adults on a 85 degree day with high humidity, I can normally squeeze out 600-650 fpm. The airplane not being clean by any means mind you (she needs a bath!).
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Field elevation is 100 feet and a low humidity day. Again thanks for all the insights!
 
NWADC9 said:
2100 RPM seems low for a 172R on climbout. 2400 RPM is red line, and at full power you should be close to it; 2300 is about normal.
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Any RPM discrepancies from a mechanical tach need to be verified before being acted upon.
 
Henning said:
Any RPM discrepancies from a mechanical tach need to be verified before being acted upon.
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Easy enough to do, but a poor climb rate coupled with a reading of 2100 RPM in the climb make me suspicious of defects other than the tach.
 
Dan Thomas said:
Easy enough to do, but a poor climb rate coupled with a reading of 2100 RPM in the climb make me suspicious of defects other than the tach.
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I still want to know how hot it was. 500fpm rate of climb isn't out of line for a 172 on a hot day. And yes, it is easy enough to check the tach against a digital/optical unit or even a fluorescent or other 60 cycle light. That's why it's the first thing you do. Mechanical tachs are notoriously inaccurate, so if you have a symptom set that includes RPM, RPM needs to be verified for accuracy. No need to spend a bunch of time and money figuring out what is wrong with a 172 that is climbing 500fpm on a hot day turning 2100 when it actually is turning 2300. The answer is simple, "It's a 172 on a hot day." It's what the plane is.
 
It was 27 degrees Celsius when I took off. Not hot by any stretch.
 
Performance section of the POH will give you the climb performance data you seek. 80KIAS sounds like a cruise climb. In my S model, 85 KIAS is cruise climb speed and will yield 500FPM.
 
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