Hey i get very slow when constant climb at 400 FPM to 8000 Feet.
From like 0-3000 its not so bad but then its getting worst:
And…when i fly at 8000 i fly like 100 Knots TAS.
When i go down to 3000 i fly like 120 Knots in that height …
II thought more height means i fly faster ?? (Less Winds? Less Resistance from Atmosphere, because less Air)
<Thanks for answers!
My caveman answer:
Engine need fire. Fire need oxygen. Less oxygen at higher altitude. Less molecules means plane move faster over ground even though plane think it moving slower through air.
To be serious though, this applies a little less to the C172 because of it’s power, weight, drag, and lift. The real benefit of flying this aircraft at altitude is fuel consumption.
There is also typically more wind at altitude - this can be a good or bad thing depending on direction.
Are you leaning the engine? It is the red knob next to the throttle. I’m on my phone now but can link some helpful videos later if nobody else respond.
hehe not only TAS the Ground Speed too is slower…But yea perhaps its the wind, thanks.
Nope not leaning. Must be more Upfront wind in 8000 then 4000 where i fly.
Are you in IMC? Simulated airplane performance in clouds is degraded for some reason.
Or your loading could be nearing your max performance (see previous answers)
Then that seems to be the problem
Dont know what IMC is… Plane is loaded but not to the max. Weather is fine.
I suspect a config from my Hotas now…i set a knob to the Magneto starter … could be its pressing “START” all time…sometimes then all goes dark.-i report here if that was the case.
IMC is when the weather is so bad you can’t go off VFR rules anymore
This has been reported by many others to cause electrical outage.
For high lift, lower power aircraft like the 172, the performance drop off usually doesn’t pay unless you have wind with you - 3-5k feet is probably going to be your sweet spot for cruising but depends on altitude density but you have to lean!
Lean for less fuel consume right?
No for better oxygen vs fuel ratio and therefore more power at altitude. See Wikipedia or better the C172s POH
That would be your problem right there. As you climb, you’re good with full rich up to about 3000 feet. After that you need to pull back the mixture and gradually lean to maintain max RPM. Without that, you’re basically pumping more fuel than air into your engine and it can’t breathe and therefore combust properly.
As I said in my first post, you probably need to lean your engine mixture. Here is a great tutorial by a Youtuber named PGatcomb. He does it in the 172.
nice thank you both, i know leaning just forgot these important details!
The analog version of the 172 does not directly show you TRUE airspeed (TAS). The airspeed indicator in this airplane shows INDICATED airspeed (IAS), which will be considerably less than TAS the higher you fly.
A 400 FPM climb rate at 8000 feet would not be unrealistic for this aircraft - especially if the air temperature is on the warm side. Even at full throttle, the engine produces considerably less power at 8000 feet than it does at sea level. One thing you should do is to lean the mixture control as you climb. Watch your engine RPM as you slowly pull the mixture control back - you should see RPM increase. This will give you maximum available power for your current altitude.
While air density decreases with increasing altitude, resulting in a higher TAS, engine performance decreases with altitude. On a jet aircraft TAS will increase with increasing altitude until crossover to Mach at which point in decreases slightly.
A piston aircraft doesn’t behave in quite the same way. You can check the POH performance tables, the aircraft types I used to fly as an instructor the change in TAS is not significant, either staying the same or slightly reducing, especially when not leaning properly.
According C172S POH, cruise performance at ISA, 2300 RPM:
2000 ft: 104 KTAS / 8.1 GPH
4000 ft: 102 KTAS / 7.7 GPH
6000 ft: 101 KTAS / 7.4 GPH
8000 ft: 99 KTAS / 7.1 GPH
10.000 ft: 97 KTAS / 6.8 GPH
12.000 ft: 95 KTAS / 6.6 GPH
So nothing wrong, fuel consumption is reducing with altitude though, that would be the main benefit of cruising higher.
400 ft/min at 8000 ft for a normal aspirated engine is a very healthy rate of climb and spot on compared to the POH:
If groundspeed is different then TAS it must be wind, can’t be anything else. If wind is zero: TAS = GS. Be aware that wind does not influence TAS versus IAS or climb performance. No matter the wind the aircraft would not have climbed any slower or faster. Wind only influences the groundspeed and ground track.
As @HalberQuacky says, where do you get your TAS from (original post: 100 kt versus 120 kt TAS) the steam/gauge 172 does not show TAS. Maybe you are confusing IAS with TAS?
Correctly leaned at max cruise power you should achieve the highest TAS at 8000ft in the 172.
