Once it stalls and entered the spin, forward velocity drops off to taxi speed.

(now the speculation...) If ice happened rapidly and autopilot was still in use, the aircraft would nose up to try and keep the aircraft at altitude as loss of lift and in creased drag caused settling and loss of airspeed up to the point of stall. And the sudden change from autopilot to off and the way the aircraft would be configured, would likely be a greater pitch up and faster onset of full stall, and with the asymmetrical thrust (albeit, small) from twins turning the same direction, its ripe for spin and at that point, it would be a handful to try and avoid with very little time and diminished controllability from ice.

(and then, analogy time...)
Think of it like a car traveling fast with cruise control, entering a curve and starting a skid (dust/sand/water/snow/ice) on the road, the way out is to not dump the throttle and hit the brakes, but steer into the skid, doing that on bad condition in a curve is very difficult to pull off, because you are steering in the same place you are running out of road surface. If you are not on top of it, your going to lose control. You can't "tap the brake" and then get on the accelerator smoothly, you may not have the time to hit the "cruise off" on the steering wheel. Unless you are adept at left foot braking and right foot throttling, you likely will be sitting on the side of the road in a ditch waiting for the lizard to show up.

I flew the ATR42 and ATR72 for about 800 flight hours for Simmons Airlines in the late 80s / early 90s. I have personally flown with the captain involved in the Roselawn accident. He (Orland Agulliar sp?) was an excellent pilot. This is the only accident that I know of (although certainly not the only case) where the NTSB exonerated the flight crew, and lay the cause of the accident squarely on the manufacturer Aerospatiale (a joint venture between Italy and France, now owned by Airbus). I am not an accident investigator, but I know a little bit about the Roselawn accident, and as an aviator, I can recognize a flat spin. The accident aircraft in Brazil was definitely and deeply involved in a flat spin. In order for any aircraft to spin, it first has to encounter a stall, where one wing quits developing lift (flying), and the opposite wing continues to develop lift, which usually results in a significant roll (the rate of angular roll depends on the flight characteristics of the particular aircraft). As the rolling moment begins, the nose of the aircraft will rise, and airspeed decays rapidly. If the stall goes beyond a certain point, a spin will rapidly develops, which will quickly become un-recoverable. Once in a flat spin, the rate of rotation will often very suddenly accelerate or decelerate in rotational yaw speed, with or without pilot input. The U.S. Navy F14 fighter was particularly susceptible to flat spins - however, I gather that only from what I've read. The point being, flat spins in a multi-engine aircraft are exceptionally hazardous AND prohibited maneuvers. AS others have speculated, I agree. Ice is highly suspect a causal factor in this accident. The wing on the ATR does not behave well in icing conditions When that was discovered at Simmons Airlines, the "fix" was to send all of the ATRs to the southern-most hub of American Airlines, San Juan, Puerto Rico Hope this is helpful. Must've been a terrifying ride for all those involved.

This message has been edited. Last edited by: chuck416,

quote:

Originally posted by chuck416:The accident aircraft in Brazil was defiantly and deeply involved in a flat spin.

I'm not sure I understand what you mean by the use of the word 'defiantly' in this context. Cam you explain for a non-aviator?

I'm reading it looks like it was iced up.

quote:

Originally posted by tacfoley:

I'm not sure I understand what you mean by the use of the word 'defiantly' in this context. Cam you explain for a non-aviator?

I think he meant "definitely" and didn't catch a spell-check override.

quote:

Originally posted by kkina:
^I wonder if the auto-pilot reacted to the loss of lift from the ice build-up by gradually increasing the angle-of-attack until the inevitable stall.

kkina‘s post at the bottom of page 4.

quote:

Originally posted by newtoSig765:
I think he meant "definitely" and didn't catch a spell-check override.

A common happening on the internet. A lot of defiant people.

quote:

Originally posted by tacfoley:

quote:

Originally posted by chuck416:The accident aircraft in Brazil was defiantly and deeply involved in a flat spin.

I'm not sure I understand what you mean by the use of the word 'defiantly' in this context. Cam you explain for a non-aviator?

I think he used it coorectly. Most airplanes, especially transport category(passenger planes) are designed to be inherently stable. Without pilot input they are designed to fly straight an level. In most airplanes, when they stall or when entering a spin, if you just release the control inputs you made to enter the stall or spin, the aircraft will trend towards recovery. You must maintain "contrary controls" to keep an airplane in a stall or spin.
This aircraft looked like it was defiantly resisting it's own, and the pilots inputs to recover. Despite it's design and the pilots recovery, it remained defiant in that it stayed in the spin without ever trying to right itself.

Ok, you pilot guys, serious question. Do you actually use the term "defiantly", when describing this airplane doing this or that? Because, if you do, it's ridiculous. Defiant is a human emotional state. An aircraft is a machine.

Well, defiantly makes more sense than definitely. Because, yeah, no shit it was definitely spinning. You don't need to be a descendent of the Wright brothers to see that.

I'm a pilot guy and I just explained it. Or was I not serious enough about it?

The airplanes natural tendency is to return, from displacement, to a state of equilibrium. This airplane was refusing to try and return to that state. It was resisting it's own natural tendencies, what other word would you use to describe that condition, other than defiant?

Whatever. Still sounds ridiculous to me.

That may be, but when you are fighting an airplane that wants to do what it wants, and not what you want, it makes perfect sense.

A good summary from an expert

quote:

definitely

My apologies for the confusion. Should've read "definitely". I'll change that my earlier post.

quote:

Originally posted by chuck416:

quote:

definitely

My apologies for the confusion. Should've read "definitely". I'll change that my earlier post.

Lol, and here i was defending your use of defiantly, which i thought was the perfect way to describe it.

I seriously doubt an ATR has a natural tendency to return to straight and level flight after entering a spin!

From an imminent stall where the pilot is pulling back on the stick, yes it will naturally nose down and not stall. From there? A steep spiral is pretty well guaranteed if one lets go of the controls for any length of time in straight and level flight. Spiral instability is normal.

I am curious what effect the yaw damper would have in the initial seconds.

In this accident, however the spin was initiated, there was probably nothing to be done to recover once rotation began.

A shorter version for the non pilots here, there are two issues that cause even the best designs (and this isn't the best design) to struggle in this situation.
When a plane gets iced up, the wing shape changes due to the ice build up so it's not a nice efficient airfoil shape anymore and the ice adds a lot of overall weight to the structure.

So not only is it a much heavier plane but the elevators (horizontal tail components) can't produce enough lift in the tail to make it higher than the wings that can't produce the needed lift due to losing their airfoil shape.
Getting the nose down to regain airspeed is the only way to recover, and that isn't possible.

I've been a pilot much of my life and come from an aviation orientated family. Excellent pilots make mistakes just like excellent drivers do, have you ever pulled out a little too close to an on coming car..I have...

I think a few things happened, poor cockpit management, being the primary reason. They flew into icing conditions in an aircraft known for some issues in that regard. They did not realize icing was occurring or accurately monitor how much. ATC said they noticed a 400 foot drop followed by an 800 foot climb, and then the final decent. So they are flying along with ice building up to the point that they start to loose altitude. They turn off the auto pilot, increase power and raise the nose which starts the climb. It also changes the angle of attack which with the ice build up causes a high speed stall of one or both wings, depends on a few things including how much ice each wing has. A wing drops, correction is attempted with the ailerons and a spin begins...The rest has been discussed and is on video..
This is speculation on my part, there are many possibilities but with the little information I have I think it's plausible.

60

I'm not a pilot and I don't fly much but I thought planes were sprayed with some kind of a deicing agent when conditions required it.