Stalls in the Pattern

[steveinindy]

Per current regulations, airplanes with pushers or those that are determined to be spin-resistant or those that have parachutes do not need to show compliance to the spinning regulation

There is a reason why I am kicking around a stick shaker/pusher and a ballistic parachute plus easy spin/stall recovery for my design.

[WLIU]

So the AFM statement about "including spins" is a standard statement and does not mean that the aircraft was not spun in flight test. I am not privy to the Cirrus Cirrus certification data but I can tell you that Piper airplanes have the same statement in the AFM's and they were ALL spun, even the twins. That info is straight from the retired chief designer, who is my neighbor. We have had some very interesting discussions on spinning the twin engine aircraft. Anyway, the manufacturer puts that statement in the AFM so that YOU will not try to spin the aircraft. But the flight test department likely did over 100 spins before putting that statement on the panel and in the AFM.

I should note that up through 2 turns, as spin is "incipient" and only becomes fully developed after about turn 3. So the requirement is be recoverable from an incipient spin. Now spins are an interesting topic all its own and we can go on and on for a long time.

That said, I will agree that stalling and spinning below pattern altitude hardly ever has a good outcome.

Now if Steve is looking for design ideas for spin resistant AND rugged, I would suggest looking at the Velocity canard. I think that was the one that got stuck in the nose high attitude, the pilot looked at the rate of descent, and he chose NOT to use his parachute, but rather ride it down into the ocean, where it seemed to make an acceptable boat until help arrived. Very interesting episode of both aerodynamics and pilot judgement.

Best of luck,

Wes
N78PS

[rwanttaja]

So the AFM statement about "including spins" is a standard statement and does not mean that the aircraft was not spun in flight test. I am not privy to the Cirrus Cirrus certification data but I can tell you that Piper airplanes have the same statement in the AFM's and they were ALL spun, even the twins.

Cirrus spin testing is discussed on one of their web pages:

http://whycirrus.com/engineering/stall-spin.aspx

"As a footnote, when Cirrus applied for European certification, the authorities there (initially JAA, later EASA), when first evaluating the Cirrus SR20 agreed with the principles of the FAA/ELOS approach but had further questions. A series of spins were performed on their initiative. While not a complete program they reported no unusual characteristics."

Ron Wanttaja

[WLIU]

That is interesting info in that it supports the statement that Cirrus got the FAA to agree that spin testing was not required to achieve an Equivalent Level of Safety (ELOS). Flight testing is expensive and so talking the FAA out of officially requiring that work, with the required data analysis and reporting, likly shortened the project schedule a lot as well as saved $$. I can only conjecture that since the airplane is a such very conventional configuration that conventional behavior was expected, calculated, demonstrated informally, and later demonstrated formally for EASA. Engineers use "substantial equivalency" with existing designs to justify reduced work and it sounds like the FAA will buy some of that rationalization. EASA it appears was a little more skeptical, but in my business we see the europeans similarly require more engineering data than the US.

Thanks,

Wes
N78PS

[steveinindy]

Now if Steve is looking for design ideas for spin resistant AND rugged, I would suggest looking at the Velocity canard. I think that was the one that got stuck in the nose high attitude, the pilot looked at the rate of descent, and he chose NOT to use his parachute, but rather ride it down into the ocean, where it seemed to make an acceptable boat until help arrived. Very interesting episode of both aerodynamics and pilot judgement.

Interesting but mushing into the water and nearly every common crash scenario are pretty different critters so I am not sure you can judge ruggedness by a more or less controlled ditching.

I am trying to stay away from composite designs because I do not have the money to get an autoclave for curing. It is much easier for an inexperienced designer to design a crashwothy metal design and that design is able to be executed with techniques applicable to homebuilding. The composites in my design are largely used in non-structural parts (to reduce weight) and those that are designed to attenuate energy in a crash or hard landing.

[Ron Blum]

I can only conjecture that since the airplane is a such very conventional configuration that conventional behavior was expected, calculated, demonstrated informally, and later demonstrated formally for EASA.

Be careful with your conjecture. The Cirrus wing is not "conventional" (that is what makes it more spin-resistant); look at the leading edge. And, "They reported no unusual characteristics" is not the same as "We have shown compliance to all applicable regulations." I am not doubting what you're saying about Piper and their Flight Test programs, but I know first hand that Cessna and Beech did not do that ... especially with the jets (note: twins are not required to spin). Although definitely cheaper (no flight testing is required), I don't believe that the new spin-resistant regulation is a move in the direction of safety. Evidence from this thread through the AF447 fatal accident support that statement.

[Southron]

Well I got caught in a thunderstorm that was over my airport. The rain hadn't started yet but the winds were going crazy.

On Final I ALWAYS KEEP MY EYE ON THE AIRSPEED INDICATOR, a pilot would have to be crazy to judge his speed by the way the ground was passing underneath his airplane! When I flared for landing the runway was flashing under me like I was I had never seen it do before while my ASI indicated I was at my normal touchdown speed.

I put the airplane down (a Cessna 150) because the runway was plenty long. I figure I had a 50 MPH tailwind when the wheels touched the tarmac.. Just when I taxied into the ramp, the storm broke in its full fury.

MORAL OF THE STORY-DON'T STALL OUT IN THE TRAFFIC PATTERN. I AM SORRY THAT THOSE TWO INDIVIDUALS LOST THEIR LIVES.

[PA11]

But what do you do when your ASI is broken? It's not that we all need to become super pilots who fly by the seat of their pants, it's that we need to master control of the aircraft using all the communication venues the aircraft is giving us, both directly through instruments and indirectly through the other senses.

[Mayhemxpc]

We teach stalls for several reasons, perhaps the least important of these is stall recovery. One is to exercise mastery of the craft throughout its performance envelope. Another is to recognize the signs of an incipient stall and to take action before it goes past that. ASI's are just one tool, as are stall indicators. The first is only good if you know the stall speeds throughout the envelope, e.g., at 30 and 60 degrees bank and various weights (the second not being as critical in light aircraft as the former.) Stall warning indicators may not provide adequate notification. They may also momentarily sound in turbulence, which could frighten someone inexperienced with that happening. Some airplanes seem to go from mush to a sudden break and really impressive roll if the airplane is not perfectly coordinated (e.g., tricycle Maules without vortex generators.) As someone else pointed out AOAs are not a magic bullet, especially when the pilots attention is supposed to be OUTSIDE the airplane. Being aware of mushy controls, low airspeed, or any uncommanded action is critical.

I think we are mostly in violent agreement. Is there anything else that needs to be said?

Chris Mayer
N424AF