Poor climb performance in C-150

[DaveC]

Hi guys, looking for some advice here.

The 150 I fly has been exhibiting extremely poor climb performance (but great cruise, typically 95-105 TAS) so I've come here to look for suggestions.

I typically get 300-350 (and not just on hot days). The other day (27 degrees w/ humidity) I got 200 FPM!

Here is what I know about the aircraft:

- The plane has a Robertson STOL kit (the only things I notice is the wing fences and the smaller gaps between the ailerons when they move).
- The engine has been rebuilt recently, compression are all very high (and you can test this by trying to swing the prop.. MAGs off of course!)
- When parked, it tends to be tail heavy(Oleo is uncompressed, once some power is added it gets onto its nose, like a tail dragger almost).
- Old school Venturi installed on the right side.
- Runs rich quite often, if at full thottle w/ full mixture and apply carb heat, it runs quite rough (200-300 RPM drop). If you lean it out, it drops down to the normal 100 rpm drop
- I've heard some detonation (popping noises) if I keep it full rich, carb heat, and idle on approach. I usually leave a little bit of power (less than 1000 RPM) and lean it an inch, it stops the popping noises.

There are wheel pants available for the plane, but I was told by adding them it will affect the performance even greater (more weight). ANY tips at this point would be greatly appreciated. I routinely fly into grass/gravel strips and could really use the extra push.

Could it be that the plane is running too rich and should be leaned to peak RPM prior to T/O? I've thought of doing this but I am a little concerned about the engine quitting out (too lean) mid climb.

There used to be a school plane I would avoid at one of the local schools that would climb like this as well (maybe 100-150 fpm better). Am I just picky?

[System Message]

What is the static RPM?
Does it change when leaned
Full throttle rpm at cruise
Propellor model, length, pitch
They can have 24 or 28 degree timing depending on the cylinders.
You are not having detonation at idle
What sort of takeoff distance does it take
Do you get 2750rpm when flying?

[DaveC]

What is the static RPM?
Does it change when leaned
Full throttle rpm at cruise
Propellor model, length, pitch
They can have 24 or 28 degree timing depending on the cylinders.
You are not having detonation at idle
What sort of takeoff distance does it take
Do you get 2750rpm when flying?

I'll give you the info I know.
Static RPM changes when leaned.
Full Throttle RPM (unleaned its 2450 typically)
Full Throttle RPM (leaned 2500+)
Prop - no idea
No idea on the timing

No detonation on idle on the ground, runs fine with carb heat on, idle on ground (engine run up). Only hear the popping noise on approach, no power, unleaned, carbheat on.

Take off distance is great (probably has something to do with STOL), but climb out is terrible.
I believe 2750 rpm is red-line (correct me if im wrong), don't think you can achieve this unless you dive and windmill it to that speed.

[System Message]

If you look at the type certificate for the C-150 the allowable static rpm varies from 2320 to 2600 depending on the propellor model.
The popping should be rich mixture in the exhaust pipe
The prop may have too coarse a pitch if it can not reach full power rpm
You can easily repitch it with a bar and two strong guys and a protractor

[System Message]

Disregard that last line.

[lownslow]

...you can test this by trying to swing the prop.. MAGs off of course!

Please still treat the engine as if the mags are on when you do this. Remember: unlike just about any other switch out there, a magneto switch completes a circuit to shut the mag off. Nearly any electrical fault in the switch circuitry will cause a live mag.

The popping sounds like it may be backfiring (or more correctly afterfiring), does it go away if you add a smidge of power?

The poor climb itself just sounds like a cruise prop in action. Weird that somebody would put a cruise prop and a STOL kit on the same plane but hey, it ain't mine so whatever.

LnS.

[DaveC]

...you can test this by trying to swing the prop.. MAGs off of course!

Please still treat the engine as if the mags are on when you do this. Remember: unlike just about any other switch out there, a magneto switch completes a circuit to shut the mag off. Nearly any electrical fault in the switch circuitry will cause a live mag.

The popping sounds like it may be backfiring (or more correctly afterfiring), does it go away if you add a smidge of power?

The poor climb itself just sounds like a cruise prop in action. Weird that somebody would put a cruise prop and a STOL kit on the same plane but hey, it ain't mine so whatever.

LnS.

Absolutely.. I always take precaution.

Yes, it does go away with power.

Could very well be a cruise prop, I'll ask my AME.

[ozone]

What weight are you taking off with? I know with mine at gross I only get about 200 fpm. 150's are economical but definitely under powered. If the timing is set back to 24 degrees instead of 28degrees I do know that the power loss is very noticeable. Not sure exactly how many horses is loses tho
If you are wondering about mixture you can do a simple check to make sure your carb is set correctly. With the engine at idle slowly pull the mixture out and just before the engine cuts out you should see an rpm rise of about 25-50rpm. If you are getting more the mixture is set too rich. You will have to get your AME to set this up

[Shiny Side Up]

I typically get 300-350 (and not just on hot days). The other day (27 degrees w/ humidity) I got 200 FPM!

Have you figured out the actual density altitude you're flying at?

[DaveC]

I typically get 300-350 (and not just on hot days). The other day (27 degrees w/ humidity) I got 200 FPM!

Have you figured out the actual density altitude you're flying at?

Yeah. The density altitude on the 200FPM was around 2200 which is pretty high considering the elevation is 459 feet in Oshawa.
On a day like today (DA 1000) I would get around 300 FPM which is pretty crappy since the POH climb rate at full power ASL is 600+ FPM.

[Shiny Side Up]

Does seem pretty bad then. I usually expect the 150 to perform at 200 fpm around here on hot days, but then that's when I figure d.alt around 5-6000'.

[straightpilot]

High density altitude takeoff (not taught in Eastern Canada)

Line up on the runway. Brakes on, full power, wait for max static RPM. Lean the mixture for max RPM and then bump it in a quarter inch for cooling.

Try that and see if you get any improvement on the VSI. Also, you MUST maintain precisely your Vy for your current weight (likely at max gross in a buck fifty).

[RVgrin]

Are those climb numbers at the STOL kit's best climb rate speed, or at Vy from the POH? Have you played around to see what the plane's actual Vy is?

[DaveC]

Are those climb numbers at the STOL kit's best climb rate speed, or at Vy from the POH? Have you played around to see what the plane's actual Vy is?

I've thought about that. I went through the aircraft documents to see if there was a sheet to revise speeds but couldn't find anything. Kind of important isn't it, considering its a aerodynamic adjustment to the aircraft. I'll have another look around when I go flying tomorrow..

The STOL should only affect stall, take-off and LDG distances, right?

Haven't experimented with Vx/Vy speeds (other than Vs and approach speeds, which are considerably different). Using the standard Cessna 150 ones I've always used.

[co-joe]

I didn't know you could chose a fine or coarse (climb or cruise) fixed pitch prop, but if that's the case, you have a cruise pitch for sure. I never saw more than 90 Ktas on the 150 I flew. That would make perfect sense if indeed it is the case. I'm fairly sure she climbed at more like 500'/min initially and only got down to 200 up around the 7 - 8000' range. I took her up to 10 000' a few times by step climbing.

[straightpilot]

This might seem obvious, but if Vs has been changed by the STOL kit, Vx and Vy certainly will have changed, too!

[CFR]

Cessna produced the 150 in an Aerobat version which had a fine pitch prop on it. It cruised like a dog.

[DaveC]

Talking to the AME with regards to this airplane. It was in an accident (confirmed by a CADOR) I read awhile ago, where the PIC had an accident & damaged the wings. The new owner took it upon themselves to install a new pair of wings w/ the STOL kit on them. Ever since, the aircraft has had poor climb performance on days (even below gross) with 2 PAX. Engine and prop produce good numbers. The wings dont produce good lift - so that is why it climbs like a dog.

I've emailed Horton STOL to see what they can suggest. Thanks for the suggestions everyone.