Overweight takeoff / flight

"Greg Esres" wrote in message
...
Still, all this is of only academic interest. The one thing that IS
known is that the control surfaces must be protected at VA, and that
won't scale UP from published Va. Agreed?

No. Just because Part 23 doesn't stipulate that at a lower weight, a lower
airspeed must be used to ensure not overstressing the airplane in
turbulence, that does not mean that the maximum speed at which you can fly
and be assured of not overstressing the airplane does not go down as weight
is reduced.

Put another way: the minimum airspeed at which a given load factor can be
achieved before stalling the aircraft is positively correlated with weight
(i.e. it goes down as weight goes down, and goes up as weight goes up).
This is *known*. The fact that it's not stated in Part 23 does not make it
any less known.

Even your control surface tangent isn't really relevant to this particular
thread since you are intentionally limiting your comments to a single
weight. Again, just because Part 23 only requires a number to be defined at
a specific weight, that does not automatically mean that the number doesn't
exist at a different weight, nor does it necessarily mean that number is the
same at a different weight.

The definition of Va in Part 23 is clear. It has nothing to do with control
surfaces and everything to do with stall speed and load factor. Just
because Va is only used again within Part 23 for some other use, that does
not change the nature of the calculation. It is commonly understood that,
even though by definition Va exists only for a specific weight, that for the
purposes of flying, one needs to adjust the "operational Va" according to
weight if one expects to remain within the certificated load limits.

Pete

"Peter Duniho" wrote in message
...

The definition of Va in Part 23 is clear. It has nothing to do with
control
surfaces and everything to do with stall speed and load factor.

Actually, it seems to depend on both. I'm all turned around
on this having scratched my head for a while. Greg is
essentially correct.

23.335 says that Va must be = Vs.sqrt(load-factor)
If we take the equality, then this is the load-factor
relationship we get assuming "Lift prop. to AOA"
and "Lift prop. airspeed**2".

23.423 (and others I'd missed) say how the control
surfaces must behave at Va and above. Designers
can set anything they want for Va as long as it
passes the control surface tests.

But since they are likely to want to minimize
complexity & weight of the control surface
mechanism, they are likely to choose Va to be
the minimum allowed by 23.335. But they don't
have to.

Greg is right. They really ought to have invented
another term for it. Va isn't the maneuvering
speed at all, and should be renamed to something
completely different.

--
Dr. Tony Cox
Citrus Controls Inc.
e-mail:
http://CitrusControls.com/

"Tony Cox" wrote in message
hlink.net...
Greg is right. They really ought to have invented
another term for it.

That's not what Greg said.

I don't see why a whole thread that is really about aerodynamics needs to be
co-opted by the terminology police. The original question was clear enough
in its intent. The OP isn't asking about how to meet FAA certification
standards. He's asking about over-gross operations and their effect on
airplane performance.

Pete

"Peter Duniho" wrote in message
...
"Tony Cox" wrote in message
hlink.net...
Greg is right. They really ought to have invented
another term for it.

That's not what Greg said.

I don't see why a whole thread that is really about aerodynamics needs to
be
co-opted by the terminology police. The original question was clear
enough
in its intent. The OP isn't asking about how to meet FAA certification
standards. He's asking about over-gross operations and their effect on
airplane performance.

Pete


Well, I'm certainly not the terminology police, and I'm
awfully reluctant to get confrontational, especially with
the holidays about to start.

But there is an important point here, and one that I'd
not appreciated before this discussion. The fact is that
under pt 23, the often-quoted Va speed isn't in fact
the speed at which you can apply full control deflection
without risk of structural failure. Va is determined by
control constraints, and by the requirement that it must
be = Vs*sqrt(n). This means that it is quite possible
(although, I'd proffer, unlikely) for the POH value of
Va to be above the value where you'd risk exceeding
the load factor.

I think this is an important safety point, unappreciated
by many (and until just recently, by me too).

Cheers & happy holidays.

--
Dr. Tony Cox
Citrus Controls Inc.
e-mail:
http://CitrusControls.com/

TC: Greg is right. They really ought to have invented another term
for it.

PD: That's not what Greg said.

GE: Greg said exactly that. He said "They really should have called
it something else, IMO."

co-opted by the terminology police.

No communication takes place without an agreed-upon vocabulary, which
is why technical disciplines define terms very precisely.

Equating "Va" to "maneuvering speed" is commonly done, but it's
sloppy. You can scale both speeds down with weight, but you can't
scale Va up.