After some bizarre experiences (like a very very long climb to FL65), I would like to test in flight the climb performance and service ceiling of my club’ 172 and 152. I won’t test the whole fleet of course, the goal is also to have some fun and fill my curiosity.
My point is : how do you test those in proper conditions, without tearing down the engine ?
The aircraft only have an altimeter, VSI, tachometer, oil T&P, and the small Cessna thermometer on the upper vent :)
First I would need to get clear of CAS, so some time at about 1500ft before starting the climb. Then it wouldn’t be an issue.
I think I would note every thousand feet: altitude, IAS, climb rate, RPM?, temperature
Do I just climb and maintain Vy ? Do I make steps ? Do I try a higher speed at first to better cool the engine ?
How do I lean in the climb ?
When do I stop the climb based on oil temp (I remember seeing it rise in a long climb)?
Both should reach 6,500 feet in around 15-20 minutes. Vy decreases slightly with altitude but only a few knots. Outside of tropical conditions cooling should be a non problem. Initially cruise climb to have better lookout, but above 3,000 feet Vy to get to altitude efficiently.
It’s full throttle all the way, with modest leaning above 5,000 feet. There is no sophisticated leaning technique with these carburettor engines, and in the climb difficult to detect peak RPM, but ideally lean to peak RPM and then enrich a couple of turns.
The 172 will climb on a hot day to service ceiling (have flown them across the Rockies in the summer) but will struggle in turbulence. If in turbulence level off to fly through the downdraft/sinking air, and then restore Vy in rising air – like a glider.
With a PA28 I have reached altitudes of FL95 of higher for the cruise and I have been at FL150 in one of them in the past crossing the Alps. It takes a lot of time to get there, but it is doable.
We also have both 172 and 152 in our club. But the 172 climbs much better, that is because the propeller pitch (fixed prop) is tuned for climb, easier to get our of small fields. It doesn’t cruise too fast but it climbs very well.
Maybe your club has cruise props? Check it out.
I guess one just need to time it? 20min is a good number for 8000ft in C172 but that is a very long time when you want to get there quickly, I also found changing to another +/-2000ft for VFR level while keeping cruise takes roughly +10min/-5min
I always felt disapointed trying to outclimb (e.g. airspace, terrain, clouds…) without any planing and I had to orbit few minutes but Skydemon profile seems to always get it right…
Different pitch props are permitted on fixed pitch prop powered Cessnas. The changed pitch will make a noticeable difference in climb performance. If you want to gather rate of climb data, follow this procedure:
Three pairs of reciprocal climbs using maximum continuous power and at Vy. The climbs are begun through 2000 feet, or at least 1000 AGL, or higher, as required to obtain smooth air, and continued for 3 minutes.
The C.G. is to be kept as forward as possible at all times.
As far as practical, climbs are to be conducted crosswind, wings level and maintaining a constant heading.
1. Set the test altimeter to 29.92.
2. At 1500 ASL and on a heading as close as possible to crosswind, trim the airplane at the specified airspeed and power setting.
3. Establish a stabilized climb with wings level.
4. Maintain takeoff power throughout the climb.
5. Maintain a constant heading (allow the airplane to “drift” with the wind).
6. Continue the climb for a minimum of 3 minutes. Record the altitude every 30 seconds.
. If an atmospheric disturbance is encountered or poor airspeed control occurs during this period, the climb will be repeated.
7. Repeat on a reciprocal heading using the same starting pressure altitude.
If you want exact climb data, the results of this data gathering are then corrected using the “PIW CIW” method.
Climbs longer than 3 minutes should not be necessary.
Thank you for your inputs. It took 20+minutes to climb to FL65 on an ISA+7 day, with a particular 172 that only did about 95-100kts in cruise. So not the best in the world. I remember the oil temp got close to the red line.
I normally fly another one that does 105kts true all the time. But it climbs quite slowly too.
It makes about 2400rpm at brakes release so I don’t think it is a cruise prop.
I read a POH online that says Vy is 79kts indicated at MSL decreasing to 69kts at 10,000 feet that I don’t think I will ever reach.
In terms of leaning, I will just turn the knob every 500 feet or so.
The objective is to know what is possible in terms of mountain crossing, water crossing, on top flying ….
Was it just you, or were there passengers?
That doesn’t sound like “book”, a lightly loaded 172 (not SP with 180HP) should climb, eventually, to FL125, and if one or two up, show around150- 200 fpm at this level. At FL65 it should achieve 400 fpm plus.
We were three POB of 70-75 kg each, with full fuel less an hour.
At FL65, we had about 150 f/min.
It is a F172M, 150hp.
RobertL18C wrote:
That doesn’t sound like “book”, a lightly loaded 172 (not SP with 180HP) should climb, eventually, to FL125, and if one or two up, show around150- 200 fpm at this level. At FL65 it should achieve 400 fpm plus.
Exactly. Something doesn’t sound right at all there. I don’t fly our club 172s very often, but getting to say 8500 ft is a non-event. Out of curiosity I just checked the flight profiles of the last two flights I did in the ‘Little One’, a 172M with an O-320 @ 150hp and found I got to 4000ft in 8 mins and 5500 ft in 12. Cruise climb in both cases and kept low by ATC for a couple of minutes in the second.
