"Gldcomp" wrote in message . com...
Maybe I need to clarify this in other words.
No legislative requirement was ever established to carry parachutes because
airplanes or gliders fall appart in normal flight.

Actually, the only legislative requirement (in the US, at least) to
carry parachutes is precisely because of the possibility of airplanes
or gliders falling apart in flight. You're right, it doesn't relate
to normal flight: it relates to flight with a bank angle exceeding 60
degrees or a pitch angle exceeding 30 degrees (nose up or down). If
only normal flight is intended, there's no legislative requirement to
carry a parachute at all.

This is a common beginner's instinctive fear, expecially during a recovery
from stall, that the wings will fold and they will drop down like a rock.

Agreed.

The simple truth is that airplanes and gliders don't do that, UNLESS WE FLY
OUTSIDE THE ENVELOPE (exceed VNE, G-loads, etc), or we sabotage it in some
other fashion such as an ill-executed repair, or controls not properly
connected upon assembly.

Sort of circular definition: if everything is as it's supposed to be,
nothing happens that shouldn't. But what you said a few posts back
was,

"Gliders don't fall appart in flight by themselves like ultralights
and other
crazy flying machines. Gliders are, after all, certified aircraft."

The safety doesn't come from certification, nor from disparaging other
aircraft, nor from hiding behind legislation. It comes from
respecting the engineering limits of the aircraft. Fly your glider
normally, within its normal flight parameters and, if it was properly
engineered and maintained, it will not come apart in flight. This is
also true of "ultralights and other crazy flying machines," by which I
assume you're referring to Sparrowhawks and helicopters in that order
;-) Certification does have value: it establishes that the aircraft's
design and construction, and its operating limitations, conform to
established engineering practices. Many non-certificated aircraft
also conform to those practices, but you have to find another way to
be sure of that. In either case, you have to maintain and operate
them properly also. Properly engineered and maintained aircraft,
flown within their limits, won't fall apart in flight.


I never said one is more survivable than the other.

I didn't mean to suggest you had. I made the remark because I was
comparing fatal accident statistics. If one was more surviveable,
then my statistics would not be representative of structural failures
and midair collisions as a whole. However, I think they probably are,
in which case in-flight structural failures for any reason other than
collision are 4 - 5 TIMES more likely than in-flight structural
failures due to midair collisions.

Notice again what I said : Structural failures is NOT the reason we are
required to wear parachutes (but of course, if they do occur, parachutes
will save the pilot just as well).

Midair Collision is the reason we are required to wear parachutes.
That's all I said.



Yes, and it's not in accordance with the facts. Let's review.

1. Structural failures in flight are extremely rare, as I'm sure you'd
agree. With even more incredibly rare exceptions relating to
maintenance, they are almost always caused by operating the aircraft
outside its design limits - either in terms of airspeed or aerodynamic
acceleration loads - or by imposing excessive structural loads during
a midair collision.

2. Midair collisions account for about 1 in 5 in-flight structural
failures. The rest occur for reasons other than midair collision.
Therefore, to the extent that we need to worry about in-flight
structural failure at all, collision is not the primary thing to worry
about: operating the aircraft within its normal limits is.

3. The FAA does require parachutes for "aerobatic" maneuvers,
precisely because of the increased risk of structural failure
resulting from exceeding airspeed or aerodynamic acceleration limits.
It does not require parachutes because of midair collision risks.

4. Glider contest organizers (not legislators) require parachutes
because of the risk of midair collision in high-density thermaling
situations.

For our beginner friend, the bottom line is this:

Yes, most of us wear parachutes, and it seems like a rather
conservative but sensible safety precaution. We do it because we're
aware that soaring brings us into thermals that may have other gliders
in them, increasing the risk of midair collisions. However, this is
mostly just something to make us all feel better, because actual
midair collisions that cause the aircraft to become uncontrollable are
even more rare than the aircraft breaking up in flight for some other
reason - and that's very, very, very rare!