ground effect airspeed

[flyguy]

Anyone been able to check the difference between stall speed at a safe altitude in contrast with just as you touch down in a full stall?

I have always thought that the stall speed should be lower within say a half wingspan of the ground, but I have to say I have never been able to check it out.
Was just thinking about it. (slow afternoon, 103 outside, just had ice cream.)
Darryl

[Len Petterson]

Re: ground effect airspeed

Good Question ? If I think about it. 55 or so is my tuchdown speed, mainwheels on the ground, if it is becuase of ground effect I dont know!
Lift off speed is 45 + - wheels of the ground, grassrunway. I only land on pavment at flyinns or for other good causes, fuel, food , etc.
Stall speed nose very high and brakes at 42mph.
Len
Maybe I go to a long runway and try it out.

[jim cooper]

Re: ground effect airspeed

go to long runway (5 thousand or so) crank trim way back, come across numbers at 55 and just keep pulling back gently, adding JUST a little throttle to keep it flying. This is how I land at busy airport to clear active as soon as possible. When you start running out of runway, chop throttle and it will (should) plop down in perfect three point assuming that you are flying it about 0ne foot off runway. I THINK it should be flying then at about 45 mph. With the T Craft wing you can REALLY slow it down! I never check speed in pattern, just land as always have. You get a sense of what speed it should be when the airplane becomes familiar. SLIPPING is most important and the t -craft slips great if you totally cross the controls,IE: Wheel all the way over, opposite rudder pedal to floor.JC

[Ragwing nut]

Re: ground effect airspeed

I always full stall land a taylorcraft, or any light aircraft for that matter. Never watch the airspeed once I cross the fence , too busy paying attention to the airplane attitude. Slipping only necessary if your coming in to high

[flyguy]

Re: ground effect airspeed

I think there may be some confusion here as to my question: I am interested in the ground effect as it applies to all aircraft, not how to best land a Taylorcraft.

Today I played around some while it was dead quiet this AM. I found pretty consistently that I was hitting the deck at about 42 statute. As this 12D stalls at altitude at 43 or 44 confirmed, I am beginning to have an idea that ground effect may be a higher speed phenomenon.

Or maybe that floating down the runway 10 off the deck has nothing to do with ground effect, even if it does feel like floating across the top of something.

I read somewhere that it is caused by the modification of both the vortex off the tips and the down-flow from remainder of the wing.
Ah well, it was an interesting 'spearment Lucy.
Darryl

[Hank Jarrett]

Re: ground effect airspeed

Ground effect takes hold at about half the span of the wing (in altitude above the ground) and is a result of the downwash from the wing and tip vortex hitting the ground. It gets stronger the closer to the surface you get and since it is a percent of the down wash and vortex it grows with speed and wing loading. That's why you saw only about a 5% change and an F-104 would probably see 40 or 50 Knots down close. His stall speed is higher and his wing loading is MUCH higher. Gliders see a strong effect because the wing is soooooo LOOOOONG.
Never tried to measure the effect on my T. When I'm that close to the ground I have never looked at the ASI.
Hank

[bashibazouk]

Re: ground effect airspeed

I've got a friend who swears that Taylorcrafts speed up in ground effect. Not sure I totally agree, but the long wing and atypical airfoil do something different than other types close to the ground, for sure.

Josh

[flyguy]

Re: ground effect airspeed

I'm pretty sure your friend is right. What is likely is that at a given power setting the airspeed will be higher; but that is likely limited by the gross nose down trim required at higher power settings, so I would check it at say 2000 RPM as an example.

Good point Hank, I can understand that I think.

I can check for an increase in airspeed, compared to say 500 feet, easily enough as we have a long runway and it is pretty quiet during the week.
DC

[jim cooper]

Re: ground effect airspeed

Here we have a very simple trainer, built over 60 years ago to teach the unwashed masses how to fly. Not being an engineer or numbers nut I never really cared about ground effect on these little planes as in my humble estimation it goes under the column heading of "who gives a sh--! I DO care about slipping it as if the little 1930's underpowered engine throws snake eyes I want to be able to squeeze it in someplace without killing my ancient posterior. Good shoulder harnesses are also worth worrying about, an excellent investment (with kwik disconnect) JC

[flyguy]

Re: ground effect airspeed

Darn Jimbo, you mean I can't play like my little put-put is a Bell X-1 and I'm the chief experimental test pilot? Shucks. Chuckle.
DC