Hello Genghis
I appreciate your efforts for other PPruner’s in the past, and am happy to help you however I can.
Here are some thoughts cut from my previous writings, and some additional observations relating to your inquiry, I hope they assist you….
Next week will be the 20th year I have owned my 1975 C-150M. During this time, I have accumulated more than 2500 very trouble free hours on it. It was Horton STOL kitted when I bought it, and that was a major factor in my choosing it. I owned a 1976 C-150M prior for a short while.
In order that my comments may fall into context for you, I have an additional several thousand hours in nearly all of the other single Cessna models, excluding the 120, 188, 195 and P210. This experience is on wheels, skis, floats and amphibian floats where the type is approved on alternative configurations. I have also extensively evaluated other STOL kit installations. I offer this because comments to come will surely cause trauma, and doubt of my credibility, with some PPruners. Perhaps they will open their minds a little….
All of the following is written with respect to the Horton STOL C150M with the O-200A engine, and a 69-48 prop, unless I indicate otherwise.
I have gone to great effort to evaluate exactly what flap setting is most useful for each stage of flight in the 150. As a result of this effort, I have established my operating technique with respect to flaps. It is: 15 degrees of flap at all times while the aircraft is in motion on the ground, and during takeoff, slowly retracting to zero when obstacles cleared and 65 plus MPH. In the latter portion of the landing circuit, 20 degrees, with selection to 40 degrees when the landing is established. I do not ever use landing flap settings of less than 40 degrees, unless it is for the occasional practice for the possibility of flap motor failure.
I have never landed in crosswinds so high that I felt that a flap setting of less than 40 degrees would be any easier to control. 18 knot crosswinds are a challenge as usual, but not a problem.
My takeoffs are conducted with rotation initiated at 45 MPH indicated, and allowing acceleration to 55 MPH once clear of the ground. If heavy on a hot yucky day, I’ll let it get to 50-55 MPH before rotation. Climb out at 65 MPH. Approach is 70-65 MPH, with an over the fence speed from 60 to 50 MPH, usually carrying some power, depending on the steadiness of the wind. I have installed an airspeed indicator from a Bell 206 helicopter, which indicates down to 20 MPH. The Cessna original indicator spent too much time floating uselessly between 40 and zero during very slow flight. With 40 degrees of flap and full power, my C150 will safely fly at 23 MPH indicated for extended periods. Slight climb, and 30 degree turns are safely possible in this configuration. I avoid this type of flying on hot days to keep the CHT down though. I do have a CHT indicator to be sure. I agree that there is probably some pitot tube position error in this value, so I am not asserting it. Landing at such slow speeds is not possible though, as the tail is flying lower than the main wheels at that speed. A tail strike is assured if such a low speed, high power landing is attempted in a STOL single Cessna.
Side slipping with 40 degrees of flap in a 150 is no problem, and entirely safe. The other week I demonstrated a full flap, full rudder deflection, 180 degree turning glide approach, with the return to co-ordinated flight just before the flare. I was fulfilling the specific request of another PPrune member, who seemed to quite enjoy the experience. If you wish, I will ask her to contact you, to provide her observations directly to you. The cautions about slipping Cessnas with flaps extended is a reference to some 172’s. I’ve do it many times and they are quite safe. In a slip, there is a bit of turbulent flow over the H stab between 65 and 55 MPH, which gives a non-reassuring softness to the controls in pitch. This is very similar to what happens to a 172 at these speeds with one door removed.
A comment about gliding STOL Cessnas: though possible, they are not to glided at speeds slower than the flight manual suggests. The plane will fly safely in the glide 10 MPH slower, but come time to flare, there will be no reserve inertia, and a very hard landing is assured.
I have found during soft ground operations in single tricycle Cessnas that the selection of 10 to 15 degrees provides much improved elevator authority. This can be vital for keeping the nose wheel either completely off the ground while taxiing, or at least light. It makes a big difference for the propeller life (particularly in gravel), and nose wheel strut life between rebuild.
An overshoot with 40 degrees of flap, with subsequent climb out, is not spectacular, but can be safely accomplished. I have done it at night with a failed electrical system, and completed a circuit and landing. It is certainly my preference to retract the flaps from 40 to 20 while overflying the runway in ground affect if that is possible safely. But, if you have to climb out, you can. A speed of 60 to 70 MPH during this phase would be great, but sometimes it’s hard to get that much speed. I prefer to keep the altitude to less, and the airspeed increasing, rather than the other way around during an overshoot. I’m happy to go from 40 to 20 flap in one selection, but a pause at 20 is pretty important to let a bit of speed build up. Another pause at 10 is a good idea.
The flap position indicator in my 150 is on the left door post. It is not perfect, but it is an improvement over the earlier versions, which was right above the pilot's head (good for instructors to see though). I have devised a very presentable decal which is applied to the inside of the left wing rib aft area, which becomes exposed when the flap is extended. This simply makes 10 degree increment lines become visible as the flap extends. When you're flying left hand circuits, you spend some time looking right out in that direction anyway, so a quick glance, and your flap setting is confirmed. Should anyone wish a CorelDraw file of this decal, PM me and I'll be pleased to sent it along via email. It's installation would not require modification approval by Canadian standards.
I agree that the Later Cessna flap preselect switch of the later 150's and all 152's is pleasing to use, but they can be more demanding of maintenance though. When they go wrong, they go way wrong! I’ve had runaways. With non-pull type breakers, you cannot stop them in transit.
The original C150 flap switch is the subject of a service bulletin, which suggests its replacement with a spring to center from both position type. This is not mandatory though, and I have preferred to leave mine original. You just have to pay attention a little during retraction. You can select the flaps up and they go 40 to zero in one motion before you realize. That’s not safe in a 150, close to the ground.
The subject of the ergonomics of the flap indicator and switch of the C-150 are addressed in an article by Dr. Harold Dale, in Volume Two, Issue No.1 of the International Journal of Aviation Safety. This might be of interest to you.
I am not of the opinion that flap asymmetry in a single Cessna is a risk of any concern. If it were to happen during extension from flaps up, retracting the flaps would fix the problem. If one flap suddenly retracted from full flaps - forget it, you'd be done, unless you had lot's of altitude, and manual flaps. I’ve never heard of this happening.
A greater risk, and is has happened to me in a Cessna 180 floatplane, is a flap track breaking off. During water touch and go's (way farther from shore than I should have been) I quickly retracted from 40 to 20 while on the step, and took off again. The flap handle felt a little funny. Once airborne, I could not move the right flap at all, and the left had become a very unsafe aileron. I flew home with 20 flap out, and landed with that setting, and great care. Once on the water, the right flap hung down inboard at an odd angle. It's track had come completely out of the wing!
So, after that long, and potentially controversial text, I hope that it has been of some assistance to your research. It’s what I actually do, and know. When the time is right, I’ll be very eager to understand what you’re working on. In the mean time, feel free the PM me if more information would be helpful.
Cheers,
Pilot DAR