why would a rv-6 stall in a low ( alt) high speed turn, the plane stalled left wing down nose down?

Question

my friend was a 20 yr captain for a major,

Answer 1

Because an aircraft can stall at any speed if the critical angle of attack is exceeded.

Many pilots (and it would appear very experienced ones) believe that they are immune to stalls as long as they keep the airspeed up. This is fine in level flight or in steep turns with a light touch on the controls. But if you crank and bank, you can stall the wing at any speed below Va. Above Va, you can rip the wings off.

The low altitude probably sealed the deal. I've fooled around at low altitude, but I've always kept a light touch on the controls and a healthy airspeed margin. I don't do it anymore.

Answer 2

The RV-6 is a fine aircraft. The stall speed is about 50mph in 1 G flight. A aircraft will stall when the wing does not generate enough lift to support the aircraft's weight (critical angle of attack exceeded).The faster aircraft goes, the more lift the wings provide. In straight and level flight, the wings have to support the weight of the aircraft and passengers. When an aircraft maneuvers, the aircraft is subject to G forces different from the 1 G it experiences in level flight. A common example given is that it takes 2 G's to maintain a level turn at a bank angle of 60 degrees. If an aircraft's stalling speed is 60 knots in 1 G flight, it's stalling speed will be over 85 knots (barely) in 2 G flight. At 4 G's the stall speed will about double from the 1 G stall speed (what we normally refer to as stalling speed). So you see that stall speed is not the same for all flight conditions. A high speed stall can will occur when the wing can no longer support the weight of the aircraft, or more correctly, when the critical angle of attack is exceeded. Most of us small aircraft pilots think of stall occurring at certain air speeds. In reality it occurs at a certain angle of attack, that is different for different wing designs. For the high speed stall that your friend experienced in his RV-6 to have happened, he must have been pulling some G's. Was he recovering from a dive at low altitude? Or a high G pull up after a low pass? Very sorry to here about the accident.

Answer 3

All good answers so I'll just throw in one more point. The most common stall accident happens during a tight base turn to final during landing when there is actually a tailwind on base leg. The pilot will tighten up the turn as he overshoots the final approach course and the increased bank causes the nose to drop. He applies more back pressure to keep the nose up and the speed under control. While this is happening, he sees that the overshoot is getting worse so he'll apply bottom rudder to get the nose pointed at the runway. The result is that the nose actually drops even further and he incorrectly applies even more back pressure on the stick to bring it back up. This sequence continues as the situation gets worse and worse until the lower wing stalls and the airplane enters an accelerated cross controlled stall and subsequent spin. It won't even make it through one turn in the spin as it impacts the ground in a very steep nose down slighly inverted attitude. After all these years, it's still happening on a regular basis.

Answer 4

alright without getting to complicated here goes. A plane can stall at any attitude or airspeed. A plane stall when the wing reaches its critical angle of attack. The angle of attack (AOA) is measured by the angle created from the relative wind and the chord line most know this much. However fewer people know that the angle of attack actually closes back up after your flight path changes. ex. if you are flying straight and level and go into a climb your AOA changes temporarily and then after that your flight path is upward and therefore the relative wind is once again relatively level with the wing. same thing holds true with a descent so if you pitch forward you can actually stall the wing by pitching forward to the point that it exceeds it critical AOA. This is a common thing to be concerned with in aerobatic planes while performing many manuvers. so to answer a plane can stall at any airspeed and in any configuration. also keep in mind stall speed is increased by turning due to the excess load on the wings you can refer to a POH to see the significant diff. in stall speed from straight and level vs. 30 and 45 degree turns. good look and fly safe.

Answer 5

The same reason it would stall in any other configuration. The critical angle of attack was exceeded. The stall speed in a turn is much greater than in level flight.

Answer 6

The others answered correctly but I'll throw in my two cents.

To maintain level flight the wings need to provide an amount of lift in the vertical direction equal to the weight of the plane. Let's assume we're talking a 2,000 lb airplane (for purposes of this discussion I'm going to ignore the additional "weight" of tail downforce - trying to keep things simple :)

If you bank at 45 degrees the lift vector of the wings is no longer pointed straight up - it's pointed at an angle of 45 degrees to the horizon. Consequently, there's not enough lift acting in the vertical direction to support the weight of the airplane so the airplane will start to descend. In order to maintain level flight the angle of attack of the wing needs to be increased to the point where you, once again, have 2,000 lbs of lift acting in the vertical direction (the wings will be producing more than 2,000 lbs of lift to maintain altitude - you feel this as increased G-forces). Since you increased the angle of attack you're closer to the critical (stalling) angle of attack. If You bank steeper still, say 60 degrees, you'll need to apply even more back pressure to maintain level flight, further increasing angle of attack. If you continue to increase bank angle you'll have to continue to increase your angle of attack to maintain level flight to the point where you may exceed the critical angle of attack. At this point the wing stalls (and it will be at a speed considerably higher than the published stalling speed).

I've flown a Piper Archer at 100 knots (published stall speed about 55 knots), put it in a 60 degree banked turn and pulled all the way back on the yoke and stalled it at a speed of approximately 90 knots - 45 knots over the published speed. Published stall speed only applies at max gross weight in a 1G, wings level attitude. Stall is all about angle attack not airspeed. The only reason we have stall "speeds" in light aircraft is that most of them don't have an angle of attack indicator. Since there's a correlation between speed and angle of attack we use speed as sort of a "poor man's angle of attack indicator".

One way to keep yourself out of trouble when flying is to remember that the further back you're holding the yoke the closer you are to a stall - irrespective of airspeed.