Getafix wrote:
To shed some light on the initial question, in general I have found that the average rotation rate for these aircraft types is approximately 2 seconds per rotation. The average height loss is about 800 feet for the first rotation (incipient) but once developed about 200 feet per rotation, this equates to a rate of descent of approximately 6000ft/min! I have no idea what the figures are for a flat spin however.
I was a station pilot on Harvards at Dunnottar many moons ago. The very same question came up, the ROD in a flat spin. We did trials in a controlled environment. We entered the spin, kept the controls in the pro spin positions. After five or six "rotations", the spin flattened out. From here we did timed descends, with the results showing a ROD of 6000fpm+.
The recovery in the Spam is standard, with a positive "wind-up" in the recovery.
Christo Jansen van Rensburg
"To be legal, you need the law;
To be just, you need a value system"
Getafix wrote:
To shed some light on the initial question, in general I have found that the average rotation rate for these aircraft types is approximately 2 seconds per rotation. The average height loss is about 800 feet for the first rotation (incipient) but once developed about 200 feet per rotation, this equates to a rate of descent of approximately 6000ft/min! I have no idea what the figures are for a flat spin however.
I was a station pilot on Harvards at Dunnottar many moons ago. The very same question came up, the ROD in a flat spin. We did trials in a controlled environment. We entered the spin, kept the controls in the pro spin positions. After five or six "rotations", the spin flattened out. From here we did timed descends, with the results showing a ROD of 6000fpm+.
The recovery in the Spam is standard, with a positive "wind-up" in the recovery.
Hi ZAZU,
Would you have the ROD for the specific aircraft, same conditions, for a "normal" spin?
In terms of ROD, the aerodynamics (and I use the term loosely) of a flat spin are probably closer the that of a skydiver than that of a flying aircraft. The overall direction of travel is pretty close to vertical, and the ROD is basically determined by the balance of drag and gravity.
Consider a skydivers - let's say Avcommer Velocity - leaving an aircraft. The moment he jumps he is travelling forward at the same speed as the aircraft, and has zero downward velocity. He immediately starts to fall, but his forward velocity also slows due to drag in that direction. Over the next few seconds he transits from horizontal to vertical motion. After about 6-10 seconds he is falling vertically. The experienced skydivers can manoeuvre in this time - work in the slide, or during transitiion - even though the speed and direction of the relative is changing.
Now compare this to an aircraft in a stall/spin. As the aircraft enters the stall, assuming it was straight and level to begin with, the wings are no longer producing enough lift to sustain flight. The aircraft begins to fall, and until lift is restored, it will accelerate downward under gravity. And, as long as there is no power, the horizontal velocity will continue to bleed off. Once the spin develops, the horizontal velocity will bleed rapidly off due to drag. As with the skydiver, the end trajectory is downward, ROD determined by the balance of drag and gravity.
I'm not sure how to track this down, but a few years back I saw a video of a Russian jet at an airshow doing flat spins. The jet had wing tip smoke generators, and clearly showed the overall trajectory of the aircraft. Anyone remember it / have a copy?
