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Old Cessna 152 question

J

johannesl

Charter Member
I know this is an old issue and some of you may not have these issues at all, but here goes. I have the Just Flight and Carenado Cessna 152s and the François-Denis GUIDEE & Yves FRANCKART Cessna 150. As has been stated in a number of places the Just Flight 152 climbs like a bat out of hell but, at least in my experience, the cruise and approach are just about spot on. On the other hand, the Carenado 152 climbs and cruises just about right but on approach it sinks like a rock and I have to add a lot of power just to make the runway. In their .cfg files they both seem to be using an O-360 with a 76" prop combination instead of an O-235 with a 69" prop. This brings me to the freeware Cessna 150 made for FS9. It seems to be using the correct O-200 and 69" prop and for the most part seems to hit all the numbers just about right all the way around. I don't know what the freeware guys did right that the payware guys didn't but it would be nice to have a 152 that works correctly all the way around. (Yes I know you can use a new paint on the 150 but that's not the point here.) I've tried editing one or both the .cfg and .air files and I can get the plane to perform in one aspect correctly but this negatively affects the performance in the other aspects. As a case in point, if I change the engine and prop to the correct ones on the Just Flight 152 I can't seem to get much more that 2100 rpm, so there must be a parameter I'm missing there that is keeping it from developing full power. Anyhow, I guess this is a long winded way of asking if anybody has or knows of someone who has modified either the .cfg and/or .air files to get these 152s to perform correctly in all aspects of flight?
 
You could try simply dropping the cfg and air files from the French 150 into your preferred 152.
Generally, the flight dynamics of the JF GA aircraft are pretty good - largely because Rob Young was often the author. It will be interesting to see if anyone has tweaked some improvements.
 
I did copy the engine and prop parts into the .cfg file, but the engine just stalls and can't be restarted. I don't know what tweeks would have to be made to get that to work. Possibly something in the .air file, but I don't know.

Just copying the files might not work either as the .cfg references back to all the textures and the placement of various items.

I know the JF Piper Warrior is pretty good as I've flown those and it's not too far off. I have more hours in a Cessna 152 than I care to admit so I know that it is way off.
 
Sorry Johan, you are right, one would need to copy the individual aircraft lines from the start of your JF cfg and then paste them over the corresponding section of the C150 cfg. Also making sure the C150 air file is renamed consistent with the JF air file.

My JF 152 is the 'FSInsider' (freeware) version and I can't recall now whether the cfg and air files are identical to the earlier JF Flying Club version of the 152. Certainly the skins are interchangeable. The only tweak I've made to the 152 cfg is to move the load station for 'baggage' further forward (closer to the pilot/co-pilot stations) as too much rear weight contributes to the climb willingness. You might try removing any 'baggage' before t/off and see how much difference this makes. I just did a quick flight and FSX loaded 50lb of baggage by default - that's a lot in a 2-seater. But otherwise, I find a bit of negative trim and throttle back to ~ 85% gives a reasonable attitude.
ps. I'm not a real-world pilot.
 
I would think in the Real world The C-150 ,having been a trainer,thousands Hard landings.Abused in flight.Stressed,Neglected ,worn out be around a long time now i would think its impossible to find any two that fly the same..bent out of rig. Warped .And more..Ditto the engines...I would think there is no new C-150 to compare to...I find Most all offered do the job in our world...
 
Depending on factors (age, condition, load, etc.) you should get between 500 - 700 fpm climb at 67 kts at full power about 2500 rpm. Changing scalar values will get you close on some of these but not all. On short final you should be about 60 kts at 1400 rpm and full flaps.
 
I've got a few hours in a real C-150 and C-152, although I'm definitely no expert on them. I got tired of dragging my Carenado C-152 in on final with full throttle, barely reaching the threshold. The plane seemed like a real dog. Its climb and cruise also seemed a little weak. It was pretty much impossible to get the plane to float, even with a purposefully very hot landing.

So in the "flight tuning" section of the aircraft cfg. I changed the "parasitic_drag_scalar" from 1.0 to 0.5. This increased the climb from 500 to 700, which I think is accurate. The max. airspeed went from 103 knots to 117 knots, which is about 7 knots too fast. The max. cruise, however, seems about right now, increasing from 93 knots to 103 knots. I think the max. cruise is supposed to be somewhere around 107 knots.

The C-152 would now float during a landing without flaps, but it still fell out of the sky with full flaps. So I reduced the flaps "drag_scalar" from 1.2 to 0.7. The landing behavior with full flaps now seems much more reasonable. Another change I made was to add the ArezOne C-152 sound, which I got at simmarket.com. Overall I'm happy with the Carenado C-152 now, although I'm sure there's still room for more improvement.

Test conditions: ASI set at "true airspeed" in FSX; plane at about 100' ASL; C-152 at gross weight (1670 lbs.); max. cruise determined at almost full throttle, 2400 rpm ( I get 2500 rpm at full throttle).
 
I thought about the drag scalars but didn't mess with those but I'll give them a try. Maybe the prop and power scalars too just to see if it gets it any closer.

By the book the max speed is 110 at sea level and max cruise is 107 at 75% power at 8000' which at that altitude, in my experience, is full throttle and about 2400 RPM. Good luck getting book numbers on a real plane though. For flight planning the book has cruise at about 100 Kts at altitude but I use 95 and end up a lot closer to my ETA. If your getting 2500 RPM (red line is 2550 on an O-235 L2C) that's not too bad.

We may get this thing figured out yet.
 
johannesl said:
I thought about the drag scalars but didn't mess with those but I'll give them a try. Maybe the prop and power scalars too just to see if it gets it any closer.

By the book the max speed is 110 at sea level and max cruise is 107 at 75% power at 8000' which at that altitude, in my experience, is full throttle and about 2400 RPM. Good luck getting book numbers on a real plane though. For flight planning the book has cruise at about 100 Kts at altitude but I use 95 and end up a lot closer to my ETA. If your getting 2500 RPM (red line is 2550 on an O-235 L2C) that's not too bad.

We may get this thing figured out yet.
Click to expand...

I've also got a few RW hours in the 152. Actually did my first solo in one in 1987 and have more recently flown too. The Carenado FDE has a good feel (compared to others) but lacks accuracy. I'm no expert either but thought I'd have a go at tweaking. Used the POH for info, for instance the CG, Datum, Engine, Fuel Tanks and various other distances were different so changed these. Modified flight tuning, flaps & propeller sections for handling & speeds. It's by no means perfect but now feels reasonable close to what I remember.

Mick
 
Thinking a little bit like an aeronautical engineer, parasite drag increases with speed and induced drag increases with lift. Since Carenado's 152 sinks more in high lift situations like approaching to land I reduced the induced drag and flap scalars and it definitely made a difference. I still need to work on it some. Changing the CG to POH values seemed to move it a bit far forward but we'll see. I haven't had time to increase the parasite drag scalar on the JF 152 to see what affect that has on climb and cruise.
 
JimH said:
So in the "flight tuning" section of the aircraft cfg. I changed the "parasitic_drag_scalar" from 1.0 to 0.5. This increased the climb from 500 to 700, which I think is accurate. The max. airspeed went from 103 knots to 117 knots, which is about 7 knots too fast. The max. cruise, however, seems about right now, increasing from 93 knots to 103 knots. I think the max. cruise is supposed to be somewhere around 107 knots.

The C-152 would now float during a landing without flaps, but it still fell out of the sky with full flaps. So I reduced the flaps "drag_scalar" from 1.2 to 0.7. The landing behavior with full flaps now seems much more reasonable. .
Click to expand...

After reading what you have done, I am gonna call my local flight school guy and see what he says about the 150/152. They have a 152 II there, and it is only marginally better than a 150 really. I think you are okay on your top speed ratings, but, it shouldn't fall out of the sky. The 152 is regarded as a very responsive plane and floats a bit more than the Skyhawk.

As for the Climb performance. If you have one person in the plane, it may climb at 700, but, may not. With two people, a local 150 will do 200-300 (granted we are in Alabama and the DA is high most of the year).
Let me ask the flight school guys there thoughts.
 
The climb rate of 700 fpm is a little optimistic as the POH has it at 715 fpm and that was done after multiple tries, by a test pilot, in optimal conditions, with a new airplane. On the other hand 200 fpm is really low. I can only recall that happening once to me and that was in a 152 that was ultimately found to have a bad engine. That flight ended with a full slip short approach from the downwind to a landing. We just have to keep tweeking the aircraft.cfg until we get what we want.
 
johannesl said:
The climb rate of 700 fpm is a little optimistic as the POH has it at 715 fpm and that was done after multiple tries, by a test pilot, in optimal conditions, with a new airplane. On the other hand 200 fpm is really low. I can only recall that happening once to me and that was in a 152 that was ultimately found to have a bad engine. That flight ended with a full slip short approach from the downwind to a landing. We just have to keep tweeking the aircraft.cfg until we get what we want.
Click to expand...


I checked a C152 POH and it shows a max. rate of climb of 715 fpm at a gross weight of 1670 lbs., at sea level and with a temperature of 15 degrees C. When I tried the Carenado C152 (after my cfg. adjustments) the plane's gross weight was 1640 lbs. and the temperature was 11.7 degrees C. The altitude was 100' AGL, which I figure to be basically sea level (It's kind of hard to flight test exactly at sea level unless you fly in Death Valley).

So, given that the Carenado C152 was 30 lbs. lighter than the POH plane, and the ambient temperature was slightly cooler, a max. ROC of 700 fpm doesn't seem to be too far off. There are so many other variables in real life, anyway, like the mixture setting, particular engine output, humidity, exact airspeed setting and ASI accuracy, plane rigging, bugs and dents on wing, wheel pants or not, whether or not your girlfriend lied about her actual weight.....
 
My buddy had a 152 that we flew out of Livermore Muni almost every Saturday that we weren't using my 140. Saturday was $100 hamburger day! His had a CESTOL kit that allowed one to land shorter but it actually increased cruise speed which went from 120 knots to 132 knots. As for landing, I never had to use more than half flaps. That was one sweet aircraft! I think he traded it for twin Beech Duke B-60 fixer-upper after I left CA.
Ted
 
txnetcop said:
My buddy had a 152 that we flew out of Livermore Muni almost every Saturday that we weren't using my 140. Saturday was $100 hamburger day! His had a CESTOL kit that allowed one to land shorter but it actually increased cruise speed which went from 120 knots to 132 knots.
Click to expand...

A C152 cruising at 132 knots with two up? I don't believe it.

Maybe you were seeing MPH?

cheers,
Lane
 
Lane Street said:
A C152 cruising at 132 knots with two up? I don't believe it.

Maybe you were seeing MPH?

cheers,
Lane
Click to expand...

I don't really care if you believe it...no skin off my nose. I wasn't flying the 152 but what I saw and what Terry said was 132. The one thing I remember about the 152 was that it could climb like a homesick angel. He said the secret was in the CESTOL.
Ted
 
Well Lane your doubt made me look up an old friend I haven't flown with in 20+ years...amazing how the mind changes the things you did and even witnessed. I had to be accurate in what I said because I don't believe in making stuff up for sensationalism. I got hold of Terry (and found we are still good friends after all these years) and lo and behold I WAS WRONG! Gulp, I said it! But it was 130 mph TAS which in that old bird is pretty dang good and it did climb like a homesick angel. He has owned two others since then that have been fitted with CESTOL. Anyway I had to make it right so here it is...
Ted
 
Lane Street said:
Ted, you're a stand up guy.

Next time you talk to your friend, ask him which kit he used.

cheers,
Lane
Click to expand...

Lane, Terry said he has a friend at Georgia Tech Research Institute who gives him kits to experiment with. They are in the process of developing this kits for business jets so that they maintain highly efficient cruise speeds and can use shorter runways. That is all I know. I don't know if they are for sale to the public but he said there are some very good RSTOL kits by a guy name Robertson available to the public who can tailor-make your kit. I never owned a STOL kit so I am afraid I am not much help there. Sorry for the earlier comment. It wasn't meant as a wisecrack but when I looked at it later it certainly could have been taken that way.
Ted
 
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