High Speed Stall

I have a Tunder Tiger Pro 0.61, can I use that to Flip? I have look at Flip already and I like this type, I have a 3D electric alredy and is wery fun to fly. I wold be happy if I can use this engine here in Sweden, I dont want to by to much, and then I must take to Thailand when I going again.

Thank you for your tip Best regards Peter

The airplane may snap to the right or left, depending on coordination (whether there's some skidding to one side or the other) and on small differences between the wings. It won't "always snap to the left." At higher speeds the P factor and torque effects are smaller and don't figure as largely as at low speeds such as a 1-G stall. You can get it to snap to the right if you have a bit of right rudder in at the time. Most snap rolls on takeoff aren't snaps at all: they're a wing-drop stall, caused by too-low an airspeed and the P-factor and engine torque. The upgoing wing might not be stalled at all, and the downgoing wing is partially stalled, on its inboard end.

Dan

I fly in Canada. I used to fly RC some with my son, and still work with him on the aerodynamics of it, and way before that I fooled with models, but got into full-scale flying in 1973. I am now a flight instructor in a College-based flight training program, and also an Aircraft Maintenance Engineer. Stalls are much more involved than being on or off. There are varying degrees of stall, and the wing may drop if it's caused to be a bit more stalled than the other. We teach this to our students in the air, working with various attitudes, airspeed and power settings. We can get the wing partly stalled and keep the nose up, experiencing the buffeting that results. In Canada the government requires a pilot to have a decent amount of skill in recovering from different stall scenarios, since too many pilots have been killed by their own ignorance in the past. When we skid around a turn at low speed in the Citabria and have the thing roll over into a spin, the airplane gets their respect real quick. They remember to keep the thing coordinated, especially when at low altitude. Go to

check section 2.8, Stalling Airspeeds. There's a good explanation of stall behavior, though no pictures of the stalling airflow. I haven't found any good pics of that yet on the 'net. Dan

Dan, What about some pics of the tuft tests? Wouldn't they show what you are looking to see and explain? Straight ones are in an unstalled portion of the wing/airfoil.

Dan we're discussing the dynamic stall of a *model* aeroplane.

Reynolds number significantly alters adhesion of boundary layer flow in models. In effect, from flow to complete separation they can literally be symptomatically on or off, and all the usual instigants can either exacerbate the incipience of or accelerate the stall, dynamic or otherwise. Read Simons on Model Aerodynamics. His Fourth Ed. is particularly improved, especially for the lay reader.

You might want to throw in a power on stall at some point later. Gives a good indication of how much reserve power you have.

Six_O'Clock_High wrote:

You need a 3D model, either electric or fuel. Contact Jim T. Graham at Hobby-Lobby International, or go to the links below. Also, you need to belong to the Profile Brotherhood. This Profile Brotherhood is what you have been looking for and will satisfy the flying wishes you have expressed.

I suspect wings are useless for 3-D flying .... they are 'stalled' most of the time. Not much air flowing over them. I suspect also that someone will build a '3-D'(whatever that is) model that had no wings, a body, engine, tail(stabilator) and a hook on the bottom to attach it to a stick to keep it vertical while launching it. Pour on the power and up you go off the hook. Hover back to the hook and back off the power. Wierd, I know.

Does any> You need a 3D model, either electric or fuel. Contact Jim T. Graham at

In all my model flying I have never seen any behavior that couldn't be explained by the same theories we use in full scale. Partial stalls, wing drops, torque and P-factor all have the same causes and effects. Wing surface roughness and misrigging, I agree, can be a bigger factor in small models, and scale speeds are much higher because of the small wing areas. Some of the models I have seen, on the other hand, are bigger than some of the smallest homebuilts, and are more forgiving than the homebuilt because the wing loading is much lower and more power is available to pull it out of trouble. The smallest homebuilt was a biplane with a 6.5 foot span, and more common types, like the Hummelbird, have an 18' span. The Pitts, I think, is around 17'. The aerodynamics that apply to these are the same as used for huge subsonic airplanes including airliners having spans of 250' or more. Bernoulli and Newton still apply. The airfoils are the same, and will deal with the air in the same way. Flutter has the same causes, and stall onset can be modified in the same ways we do with the big ones.

Dan

Stall is a function of angle of attack. At 1G and a particular weight it will occur at a particular speed every time. If the pilot pulls hard on the elevator he increases the load factor and the stall goes up by the square root of the load factor. For example, a 2G pullup raises the stall to 1.41 times the 1G stall speed. A 4G pull takes it to twice the 1G stall. Steep turns also aise the load factor. A 60 degree level turn places 2Gs on the airplane. In FS we have a number called Va, or maneuvering speed. It's used if the pilot intends to use full control deflection for some reason, such as aerobatics or really turbulent air. It ensures that the wing will stall and unload before the aircraft structure is overloaded to failure. At higher speeds the wing won't stall in level undisturbed flight because its angle of attack is very low. In highly cambered airfoils it might even be slightly negative at cruising speed. Dan

I believe that's already been done. I think they are called "helicopters".

Google up Coffin Corner and U2. At mission altitude near 80,000 feet, there were only a few MPH between stall and Mach buffet.

there were only a few MPH between stall and Mach buffet.

This tight band was what caused so many upholstery repairs to the seat in the U-2. The pilot stayed so puckered up he ate buttonholes in the fabric.

Another example is the F-104. High speed stall was a less well known phenomenon in 1957. Banking over into a tight turn even at high speed stalled the wing and the fuselage moved tangential to the arc path that would have otherwise have occurred. Put a lot of underwing stores on this bad girl like a lot of countries did with the F-104G and turning was an experience in adrenalin induced terror with simultaneous exclamation and ejection of bodily fluids/solids.

Funny you should mention that. Can't say a lot, but a winged aircraft with mechanical parts of a variety of types from a model helicopter might be capable of doing things that will make even the most jaundice RC watcher gasp. Watch the RC magazines. :o)

Er, no they don't. The root theoretical *causes* may be the same, but both the *mechanics* & *effects* can & do differ markedly in models.

Particular cases in point being those relative to mass, size and the unaltering molecular composition of the fluid in which we fly resulting in the significant influence qualifiable if not always quantifiable courtesy of Reynolds.

Speaking of effect, take the spin entry requirement and stabilisation characteristics of your *average* sports R/C model as the ideal example. Hardly representative the *average* RL GA trainer, GA lightie, homebuilt, aerobatic, ag., glider, mil or airliner type I've ever flown.

As for your preferred reference to large scale. They're unrepresentative of the average R/C model, and thus a poor example upon which to attempt validation of the point under discussion.

Whilst appreciating your job related experience and probable understanding, not being without a qualifying modicum myself, it would appear you need to familiarise yourself with R/C model aerodynamics a little more closely. A good start is the volume already suggested.

In continuation of discussion on the subject, let's stick with validation of facts specific to the salient issue, not digressive rationalisation with an objective of justifying whose ego is the 'more important'. :)

To discount the variations and anomalies of fluid dynamics relative to flight of our models as non-existant or of complete insignificance offers less than a commendable qualifying reference.

Charlie, do you speak from the position of having had THE 'personal experience'? Ehehehe.....F-104G aka 'Widowmaker' ..er "Starfighter".

The F-10x series was the inspirational stuff of my childhood. The "Starfighter" in particular sure was a pretty bird, its reputation making it all the more appealing in my youthful naivety.

I wish. I have a friend, now dead (of natural causes), who flew the F-104C in the USAF in the early '60's. He shared his experiences about flying this bird and said he NEVER had a landing in it that wasn't white knuckle, stomach in a knot. The anecdote about the "G" comes from one or more books or articles I have read over the years in Aviation Week, or Air & Space or something.