Question: 1960s 172 real world performance

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BeechSundowner

Filing Flight Plan
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BeechBum
Hi all,

Looking for some real world performance numbers on older Cessna 172s with the O-300 engine. Curious how it compares to the lycoming 320/360 series. Thanks
 
I rent out a 1960 172B with the o-300 engine. It cruises around 100kts on average but that is not where the plane is normally used. It beats the pattern really well.

It's hard to compare the 300 to the 320 or the 360. You are talking about 145hp versus a 150/160hp engine or a 180hp engine.

Dollar for dollar though the 300 is less costly in my experience.
 
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0-320 172s will do about approx 105knots, give or take a few. That's what mine did.
 
k9medic said:
I rent out a 1960 172B with the o-300 engine. It cruises around 100kts on average but that is not where the plane is normally used. It beats the pattern really well.

It's hard to compare the 300 to the 320 or the 360. You are talking about 115hp versus a 150/160hp engine or a 180hp engine.

Dollar for dollar though the 300 is less costly in my experience.
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Cheers K9. This one has the 145hp engine. Speeds is on par with what I figured. Would be using as a time builder since I sold my sundowner. Any rough guesstimate on the fuel burn per hour? POH shows much higher fuel burn than I would expect for a 172
 
Think you’re thinking the o-235, I’ve always thought they were rated 145hp.

I fly one regularly, and get about the same performance as I got out of the o-320s. Not as good a climb, but it definitely has a cruise prop, kind of chalking that shortfall to that.

No time in a o-360 172, but have flown a Cherokee 180 and 140 a lot… HUGE difference, mostly in climb, but prolly near 10 mph too.

I like the little o-300 a lot. Smooth as butter, easy starting.

I budget 9 gal/hr x/c, and 10 in the pattern or local cruising.
 
@BeechSundowner 115 was a typo. I have fixed it. Mine is a 145hp. Plan 8gph as an average for the cruise. Those years are the most underrated planes around for timebuilding.

FWIW, I had a Musaketeer that had the 0-320 and it cruises at 95kts burning 9gph.

I also have a 172RG that I rent out that has the 360. It cruises at 135kts TAS and burns an average 9.5 pgh.
 
If you are familiar with 4 cylinder high compression engines in 172's, you will love the easy starting and smooth running 6 cylinder low compression Continental.

I agree with the 100knot cruise, and have done many thousand miles at that speed. Suitable leaning gives much better mileage, and reduces plug fouling

The induction system is a notorious ice generator, any loss of RPM in cruise should immediately cuse youy to use full carb heat for several minutes, It can even build ice while taxiing in very humid conditions.

Johnson bar flaps are great, low maintenance, and instantly from any position to any other! Having had the electric motor die when landing on a short grass strip, 40 degrees down, I have never been comfortable with electric.

If it has not already been done, upgrade to Bendix brakes.

Rated for 80 octane, Mo gas without alcohol should be good, check for STC's. 10 GPH full rich, 9 leaned is my recollection from years ago. Mymaual for that plane is now in the College Park Md Aviation Museum!

I believe that will be a good plane if it is in reasonably good condition and has suitable avionics for your time building.

80% of my time in that plane was long cross country, flown to Instrument standards. My Commercial and Instrument check rides were a breeze.
 
I had a 62 with the 145 motor,never gave me a problem. For time building it can’t be beat. You can get 105 knots with a higher fuel burn.
 
The O-300 performance should be close that of the usual 150 HP Lycoming found on a vast number of post 1967 172's. Like one of the posters above noted, O-300 172's are also smooth as butter. He's likely refering the inherently low vibration and noise of the six opposed O-300 pistons cranking away compared to four in Lycoming-fitted 172's. It's really noticeable too in my experience. Slightly off topic, but the O-300 fitted 172's also had 40-degree flaps, which I personally like, although they have their critics (this is a long story, not for this thread). The 40-degree 172 flaps allow incredibly steep descents without building up significant airspeed if you find yourself too high on final or in other scenarios, most particularly if needing to make an off-field landing. The pre-1965 172 flaps were also manually controlled. I think manual flaps are superior to electric flaps on light aircraft: less to go wrong, and safer. In summary, one could argue that late 172 models did not improve over early 1960's era 172 models, despite all of Cessna's marketing glitz and gadetry.
 
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They can be pretty anemic on takeoff and climb if operated at high density altitude airports, especially when equipped with a cruise prop, as many are. Usable, of course, as long as some practical limitations are observed (light loads, early morning flights, etc.).
 
Looked at the plane and it’s in fairly good condition for a 1961 airplane. Anyone know how easy/hard these are to sell?

It’s got a new garmin IFR package with G5s, 650xi, garmin ads-b in/out, no engine monitor. Low time engine <50 hours
 
I have a 1965 with the O-300. For my mission of building time, its just fine. I burn 8 GPH.
 
Check the control wheel, see the attached Cessna Service Letter. I was lucky it broke while I was in a spin instead short final. Manual flaps, great airplane.
 

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geezer said:
The induction system is a notorious ice generator, any loss of RPM in cruise should immediately cuse youy to use full carb heat for several minutes, It can even build ice while taxiing in very humid conditions.
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And yet the carb is mounted on the oil sump just like a Lycoming's. It shouldn't ice up nearly as fast as the smaller Continentals.
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geezer said:
If it has not already been done, upgrade to Bendix brakes.
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Clevelands. Bendix hasn't made aircraft brakes for a very long time.
davela said:
Slightly off topic, but the O-300 fitted 172's also had 40-degree flaps,
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172s up to the 172N, up to 1980, had 40 degrees of flap.
 
The Geezers memory is slipping, Cleveland brakes.

The big thing back then was instant adjustment with the Jonson bar, don't remember when that went away, but hated the slow electric, with the non preselect, you had to hold the switch until the desired flaps were reached, but that same hand needed to be spinning the elevator trim. I trained my wife to hold the switch.
 
geezer said:
The big thing back then was instant adjustment with the Jonson bar, don't remember when that went away, but hated the slow electric, with the non preselect, you had to hold the switch until the desired flaps were reached, but that same hand needed to be spinning the elevator trim. I trained my wife to hold the switch.
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Electric flaps showed up in the 172 in 1965. It was a response to complaints that the flaps were too hard to extend manually. More women were becoming pilots, and I think that might have been the impetus.

And yes, the electrics were slow and sometimes troublesome. Cessna had at least three different jackscrews/clutches/limit switch arrangements. Early jackscrews were plain screws that used molybdenum grease, and later jacks used ballscrews that used a tiny bit of light oil. Mechanics didn't read the service manuals and persisted in putting the grease in the ballscrew jacks, fouling the ball tubes and causing galling of the screw, and the grease got into the limit switches and fouled them too. Bad deal on an aborted landing when you can't get the flaps up because a switch has failed because it's full of grease.

The manual flaps were great for short-field landings. One could dump the flaps, which also dumped a lot of lift and the tires then had way more traction for heavy braking. If you flick the electric flap switch up, the flaps slowly pass though 20° where the lift is highest and the weight comes off the tires and they skid and blow out. At least Cessna left the manual flaps in the real airplanes, the 180 and 185, because the pilots, working pilots, wanted them that way.
 
The jackscrew driven 172 electic flaps can deploy the flaps asymmetrically and even seriously damage a flap if things go awry. They deliver a lot of torque to the flap, without any control feedback that I am aware of except the pilot's eyeballs. So if something gets jammed, they can do damage. I've seen it on planes that made it back (but apparently they can make it back at least!). Another hazard to be aware of is that flap motors will sometimes pop their breaker (or blow a fuse if fused). This is probably due to something mechanical partially hindering the flap mechanism movement and the motor over-currenting, but it can certainly happen with operational flaps - I know because it happened to me once. The consequence is that one may be stuck with 40-degree flaps, needing to go-around, but unaware the flaps won't be retracting without an immediate clue as to why and no time to figure it out. I always make sure I know exactly where the flap breaker is on a 172 before I fly it. A go-around or take off with 40 degree flaps is actually possible, but is a pretty dramatic experience if one has never done it or is expecting it. It feels like flying a box kite (if such a thing were possible) and the climb rate does not impress.
 
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davela said:
The jackscrew driven 172 electic flaps can deploy the flaps asymmetrically and even seriously damage a flap if things go awry.
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The manual flap system can do that too, if a cable fails. Two separate systems, both controlled by the same lever. At least, though, if one flap isn't extending, you'll know it right away when the airplane starts rolling toward the dead flap.
davela said:
They deliver a lot of torque to the flap, without any control feedback that I am aware of except the pilot's eyeballs. So if something gets jammed, they can do damage. I've seen it on planes that made it back (but apparently they can make it back at least!).
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They do, and they tear things up when the flap jams, and the flap jams when one of the roller bolts tears out of one flap support. There is a service bulletin on those rollers on all Cessna singles, and one is wise to have it done. Those rollers are Torrington needle bearings with a thin, hard steel sleeve pressed over them. That sleeve can sometimes shift on the roller and starts cutting a disc out of the flap arm. The disc finally tears free and the roller cocks and jams and the flap gets twisted, the flap tracks get bent and half-torn out of the wing's aft spar. Ugly and expensive.
davela said:
Another hazard to be aware of is that flap motors will sometimes pop their breaker (or blow a fuse if fused). This is probably due to something mechanical partially hindering the flap mechanism movement and the motor over-currenting, but it can certainly happen with operational flaps - I know because it happened to me once.
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Poor maintenance, usually. Seized rollers due to inattention to them can do it. I always inspected those things before flight to make sure they were free, and on every inspection I did they got a good check. Besides that, breakers don't last forever. Their contacts get oxidized, as do their external terminals. That adds resistance which causes heating, and since these things are thermal devices, they can pop even when there is nothing wrong with the system. But in most cases, flaps that won't retract are usually suffering from gunked-up travel limit microswitches. They're not sealed and grease or oil gets into them. As I mentioned before, the wrong lube is a bad deal, and too much of even the right lube is also a bad deal. Do not lubricate them by spraying the jackscrew with LPS or anything else. Do it according to the manual.
davela said:
The consequence is that one may be stuck with 40-degree flaps, needing to go-around, but unaware the flaps won't be retracting without an immediate clue as to why and no time to figure it out.
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It's really bad in a Cessna 150. They have huge flaps and 40 degrees of extension. At gross on a warm day you are in trouble if they won't retract.
 
My thumb slipped off the button once on a go around in a 150. The button popped out of the bar. Flaps stuck at 30. Luckily it was only me in the plane. At Full power I think I got to about 150 agl all around the pattern. I didn't even have my ppl yet.
 
Dan Thomas said:
The manual flap system can do that too, if a cable fails. Two separate systems, both controlled by the same lever. At least, though, if one flap isn't extending, you'll know it right away when the airplane starts rolling toward the dead flap.

They do, and they tear things up when the flap jams, and the flap jams when one of the roller bolts tears out of one flap support. There is a service bulletin on those rollers on all Cessna singles, and one is wise to have it done. Those rollers are Torrington needle bearings with a thin, hard steel sleeve pressed over them. That sleeve can sometimes shift on the roller and starts cutting a disc out of the flap arm. The disc finally tears free and the roller cocks and jams and the flap gets twisted, the flap tracks get bent and half-torn out of the wing's aft spar. Ugly and expensive.

Poor maintenance, usually. Seized rollers due to inattention to them can do it. I always inspected those things before flight to make sure they were free, and on every inspection I did they got a good check. Besides that, breakers don't last forever. Their contacts get oxidized, as do their external terminals. That adds resistance which causes heating, and since these things are thermal devices, they can pop even when there is nothing wrong with the system. But in most cases, flaps that won't retract are usually suffering from gunked-up travel limit microswitches. They're not sealed and grease or oil gets into them. As I mentioned before, the wrong lube is a bad deal, and too much of even the right lube is also a bad deal. Do not lubricate them by spraying the jackscrew with LPS or anything else. Do it according to the manual.

It's really bad in a Cessna 150. They have huge flaps and 40 degrees of extension. At gross on a warm day you are in trouble if they won't retract.
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Great insights to know. Thanks for expanding on this subject.
 
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