Flat Spins

[Dan Kent]

I'm an new Sport Pilot, and I saw under the incident thread some speculation that the recent Samba accident in the lakebed may have been due to a flat spin.

 

I'm not sure I completely understand how this might happen so I have a question:

 

I was under the impression that most modern airplane design intentionally had the nose heavy with the elevator generating downward force to keep the plane in level flight. If a flat spin occurs then wouldn't that plane have to considerable out of W&B?

 

Wikipedia led me to believe that the CG needs to be roughly aligned with the center of lift to stay in a flat spin.

 

Thanks.

[Ed Cesnalis]

Dan,

 

I don't have the answers. The video is of an inadvertent flat spin, scary!

 

[FastEddieB]

Wow, that sucked!

 

I was wondering why the engine stopped. Then it occurred to me that centrifugal force would drive the fuel outboard in the tanks, if the plane had wing-mounted tanks.

 

Then again, most fully aerobatic planes have some sort of a header tank to keep fuel flowing in cases like this.

 

In any case, I wonder why NO effort was made at a restart?

 

 

edited to add - just went to YouTube. In the comments:

 

Engine killed as part of a flat spin recovery.

 

Plane had no electric starter.

 

That explains that!

[Ed Cesnalis]

At 39 seconds into this video is the time to employ one of the lessons from Wayne Hadley. The falling leaf manuever that prevents rotation tells us that left rudder as the right wing drops prevents the rotation, prevents the spin, prevents the flat spin.

 

There are good lessons in this video that I use in my everyday flying.

 

http://www.youtube.com/watch?v=xwrfEsCiltc&feature=youtu.be

[Darrenr]

Great video thanks for sharing everyone should watch!

[sandpiper]

Dan,

 

If you stay with what you were trained to do, periodically seek additional training to improve your skills, fly regular, fly within the parameters set for your aircraft, and don't be a wiseass cowboy, then you have very little to fear from flat spins, IMHO.

 

Further, we have no idea why the Samba crashed until the NTSB speaks. All else is speculation.

 

Sure, you should become informed about these things and continually increase you knowledge but don't let it spoil your flying.

[FastEddieB]

If you are flying an airplane that has a prohibition of intentional spins, it is best to assume the manufacturer had a reason for that prohibition.

 

Spins have a lot of dynamic elements, and should be avoided unless a manufacturer has given their blessing, which would imply full testing in all conceivable loadings.

 

BTW, any kind of a spin in the pattern will be about 99.99% fatal regardless - with human reaction times and altitude required, the ground will intervene before any kind of recovery can ensue. Hence the emphasis on avoidance rather than recovery in most (non-CFI) training.

[Jim Meade]

Eddie, I'm not sure our parents and the nuns were always the best sources of information on what we should do and not do. In any event, I'd feel better if I knew why the manufacturer prohibited various maneuvers.

 

Dynamic elements may be one reason to avoid spins, but I strongly suspect that is not the only reason manufacturers ban them.

 

Where do you get the statistic that a spin in the pattern is 99.99% fatal? I've never seen those kinds of numbers. Are they from NTSB? If a person recovers from a spin in the pattern, one is not likely to report it so how is one to count that? What is a spin? Is yaw with autorotation a spin? If so, that would mean a spin entry was a spin and while that would scare us all are we sure that we could never get out of one, especially as high as I come in? (Of course, as low as some on this forum approach I will concede they probably could never recover from even a straight ahead stall )

 

I understand that your comment was deliberately hyperbolic for the sake of effect, but still, there are some people who respond better to facts than fiction.

 

I concur that we should focus on avoidance, certainly at pattern altitude levels, but we need to teach fully developed stalls per the PTS so we can't avoid some of that. So long as we do them in a coordinated manner we are OK.

 

I know one person personally who said he was in a flat spin. This guy has flown about anything with wings and has so many thousands of hours he can't count them. He was in some experimental type plane, I don't remember if it was one with a canard or not, with the builder pilot. They were up high and got it to spin and it went into a flat spin that they couldn't get out of. Descent rate was not awful, but they couldn't establish any control authority. (By now, I know you are all hanging on the edge of your seat, asking breathlessly, "what happened" and of course the old pilot says, "well, I died, of course", but that is not what happened, since the old pilot told me the story personally.) He said that as they got down to about 1,000 AGL he decided to open his door in the hope that the crash wouldn't be too severe and it might help him get out. The disrupted airflow caused by the door opening gave just enough control effect on the rudder that they were able to stop the spin and get out of it. How about that for a "come to Jesus" moment?

 

If he'd known up front about the spin characteristics of that airplane, he'd have opened the door at 5,000 feet, I bet. I'd rather know why things are said.

 

Now, if I don't know why, should I take the manufacturer's word for it? After reading that FAA piece on the Zenith (granted there is some FAA-LSA politics in there as the cognoscenti recognize)I am not inclined to just take the manufacturer's word without a touch of skepticism.

[Jim Meade]

I'm glad to hear of that outcome. I hope Fast Eddie knows that I enjoy his posts and can't resist the temptation to have some gentle fun with him but I'm not knocking him. I'll have to fly down and buy him a sweet tea or whatever obnoxious concoction Southerners drink.

[FastEddieB]

Real quick...

 

...given patterns are generally flown at 800' to 1,000', and...

 

...the average small plane may need about 1,000' to recover from a spin, and...

 

...it may take 3 seconds or so to react to a spin...

 

...I think the chances of surviving a spin from pattern altitude are essentially nil. If someone has data to contest that, I'll happily change my opinion.

 

 

 

[FastEddieB]

And if you fast forward to frame 4 of this sequence, see what you think the pilot's chances are of releasing back pressure, applying full opposite rudder and then pulling out of the resulting dive (click for full-sized image):

 

[Jim Meade]

Ah, Eddie, now we go from a statistic to an opinion. I'll kind of halfway accept that. I do not accept that the average small plane may need about 1,000 feet to recover from a spin. There are simply too many variables in that construct.

 

We should talk about planes we are flying

Are we able to employ the controls as was advised in the ag plane vidoe?

Are we *ready* to employ those techniques

What is the CG loading, weight, density altitude, wind and so forth?

 

I have to say that if one is going to make such an assertion it seems to me up to the posters to support it. Can you give us a couple of examples of small planes that take 1,000 feet to recover? How about CT's, how much do they take?

 

I take it we are all talking about the classic skidding stall on a base-final turn, which is probably at about 500 feet (the way I teach it).

 

Don't get me wrong - I'm not in favor of playing any games there - I'm just not comfortable using scare tactics and hyperbole when facts are just as terrifyingly effective.

 

[FlyingMonkey]

A BRS can make the pattern spin survivable, but you'd have to be Johnny-on-the-spot pulling that handle. Much better to avoid the situation entirely.

[FlyingMonkey]

Ah, Eddie, now we go from a statistic to an opinion. I'll kind of halfway accept that. I do not accept that the average small plane may need about 1,000 feet to recover from a spin. There are simply too many variables in that construct.

 

The most common stall/spin happens at base to final turn. In most situations you are at significantly less than 1000' at that point, maybe even 500' or less. I don't know many pilots that could react and recover from a spin in that distance. I see what you are saying, but I think for the typical pattern spin occurrence Eddie has it right.

[Ed Cesnalis]

The most common stall/spin happens at base to final turn. In most situations you are at significantly less than 1000' at that point, maybe even 500' or less. I don't know many pilots that could react and recover from a spin in that distance. I see what you are saying, but I think for the typical pattern spin occurrence Eddie has it right.

 

It is not a given that a failure to recover on base to final spin is an automatic fatality.

 

Look at this photo, right in front of my hangar. They are pointed 180 degrees from their departure heading so some rotation happened. All 4 survived with moderate injuries.

 

[Jim Meade]

The crux of the discussion is that one school of thought says that spins are awful and they will kill you and you shouldn't do them if the manufacturer says not to.

My school of thought is I want to know why the manufacturer says not to do spins. There are a number of reasons that may be the case and I want to know.

 

My contention is that when one understands fully why the manufacturer makes any statement on maneuvers and so forth, that one can apply that information to the situation and act accordingly.

 

Don't let's try to shade the discussion into the terrible inexperienced pilot judgment mistake on base-final. Let's keep it where it started - one side says do what the manufacturer says the other side says it would be better to know why the manufacturer says it.

 

Some cited the stall spin on base-final, I cited the guy who got out of a flat spin. We can all cite examples till the cows come home.

 

Let's put it another way. Do you beat your children? If you child of three years of age insists on impulsively darting into traffic do you reason with the child or do you spank them and threaten them? I bet nearly all of you will beat your child if you think that will keep them alive. That is the Fast Eddie approach to stall avoidance. I, on the other hand, believe in thoughtful, considerate reasoning. Then if the little bleeder runs into traffic I can say it wasn't my fault.

 

Are we children?

[FlyingMonkey]

It is not a given that a failure to recover on base to final spin is an automatic fatality.

 

Look at this photo, right in front of my hangar. They are pointed 180 degrees from their departure heading so some rotation happened. All 4 survived with moderate injuries.

 

Sure, I get that. But in the case pictured I bet anybody watching that airplane go down would have expected fatalities. Low energy (low enough to stall), full flaps giving more drag and thus slower descent in the spin, structural strength of the airframe, etc give more variables than can be accounted for. Sometimes people luck out, sometimes not so much.

 

One nice thing about the CT is the low speed and energy and high strength of the cockpit cell provide a better chance of surviving such an event than something like a Lancair flying a pattern with a final approach speed of 90 knots.

[Ed Cesnalis]

So your squarely on both sides of the fence? Certain death, or not certain?

[FlyingMonkey]

The crux of the discussion is that one school of thought says that spins are awful and they will kill you and you shouldn't do them if the manufacturer says not to.

My school of thought is I want to know why the manufacturer says not to do spins. There are a number of reasons that may be the case and I want to know.

 

My contention is that when one understands fully why the manufacturer makes any statement on maneuvers and so forth, that one can apply that information to the situation and act accordingly.

(snip)

 

 

Ah, sorry if I helped derail the conversation you wanted to have. I agree with you that it is VERY helpful to understand why a spin prohibition exists for an airframe. Like you, I want to know *why* that's in place, as that answer can change how I behave in the airplane.

 

In the CT POH it states that spin recovery behavior is conventional, but at the same time states that spins are prohibited. The question becomes why the maneuver is prohibited if recovery is conventional... My guess comes down to some combination of two factors:

 

1) Factory spin testing has not been done in a wide enough variety of weight CG conditions, entry speeds, attitudes, or various AoA, for the factory to be comfortable approving spins as an acceptable maneuver for the CT.

 

2) The factory does not want liability for an accident where a spin could not be recovered (even if only due to pilot technique error). If they prohibit the maneuver, then they are protected legally.

 

The problem is that getting a straight answer from any manufacturer, especially where liability and lawyers are involved, is very difficult.

[Jim Meade]

What does stalling have to do with energy? A stall occurs when the angle of attack is so high that you have airflow separation and loss of lift. You can stall at Mach 3 and have lots of kinetic energy.

 

 

 

[FlyingMonkey]

So your squarely on both sides of the fence? Certain death, or not certain?

 

I don't think I ever said certain death. I only discussed where spins tend to be least recoverable. Well, I did say that pulling the handle could make the spin survivable. I should re-phrase that to say "increase chances of survival". Does that clarify?

[FlyingMonkey]

What does stalling have to do with energy? A stall occurs when the angle of attack is so high that you have airflow separation and loss of lift. You can stall at Mach 3 and have lots of kinetic energy.

 

We were talking about stalls in the pattern. In general, these are at lower speeds and energies than an accelerated stall at cruise speeds. I try to keep my CT under Mach 2 in the pattern.

[Jim Meade]

I was objecting to the apparent linkage of stalls and low energy. Wouldn't want anyone to get the idea that if one was stalled the airplane was necessarily in a low energy state.

I doubt if the stalls one might encounter at speed in a bizjet would necessarily be called accelerated stalls, as that term is usually used in conjunction with an abrupt control surface movement. You can edge or sneak into a stall at Mach .8 just like you would sneak into a power on stall in a CT by holding the nose up. Where did I read that in a turn, an SR-71 could have one wing tip in stall buffet and one in mach buffet? Well, that's out side my scope of reference.

 

Anyway.

 

 

[Dan Kent]

Dan,

 

If you stay with what you were trained to do, periodically seek additional training to improve your skills, fly regular, fly within the parameters set for your aircraft, and don't be a wiseass cowboy, then you have very little to fear from flat spins, IMHO.

 

Further, we have no idea why the Samba crashed until the NTSB speaks. All else is speculation.

 

Sure, you should become informed about these things and continually increase you knowledge but don't let it spoil your flying.

 

Thanks John. I agree with you and am not overly concerned, just curious as it seems awefully difficult in today's modern LSA to get into a flat spin and thought I would ask the question.

[FlyingMonkey]

I was objecting to the apparent linkage of stalls and low energy. Wouldn't want anyone to get the idea that if one was stalled the airplane was necessarily in a low energy state.

I doubt if the stalls one might encounter at speed in a bizjet would necessarily be called accelerated stalls, as that term is usually used in conjunction with an abrupt control surface movement. You can edge or sneak into a stall at Mach .8 just like you would sneak into a power on stall in a CT by holding the nose up. Where did I read that in a turn, an SR-71 could have one wing tip in stall buffet and one in mach buffet? Well, that's out side my scope of reference.

 

Anyway.

 

We're on the same page, thanks.