Va and negative g's & fun non-acrobatic maneuvers

Me again,

Va seems to be only intended to protect against excessive positive
load factors. What about negative g's?

Can I find a Va for negative design load factors (-1.52 g) for the
C172SP anywhere?

Reason I am asking is that I want to try the "floating pencil" trick
next time I fly but I don't want to shove the stick fully forward for
fear of breaking something. I am not looking to induce negative g's,
only zero g's and zero lift. Any pointers on entry speed and power
settings? Is it easier to perform if you induce a gradual +1 g steep
climb similar to a departure stall maneuver, then upon hearing the
stall horn, give it good nudge forward on the stick? I've heard that
your airspeed may indicate well below stall, but again, your stall
speed does approach zero as your load factor goes to zero.

Likewise, would you prefer to pull 2 positive g's in a pull-up
maneuver or a, say, 60 deg. bank? Frankly, I am not too familiar with
the former so I might do something undesirable. Aside from my stall
speed going up to something like 68 kts. clean (Va ~ 100 kts), you'd
see your airspeed quickly dwindling while pulling up. I think it'd be
fruitless to add in power since heck, you're not maintaining altitude
and besides, you probably don't have any excess power anyway to do
that. Neither am I familiar with the mechanics of loops so it'd be
wiser to leave that alone. Perhaps the 60 deg. bank is more
reasonable to have some fun. Would you try to hold altitude with
backpressure and power or just leave the plane to dive and speed up in
the spiral, with a recovery before Vne? I think the maneuver would be
more innocuous with power-off a-la-emergency-descent style. Again,
I've never done a 60 deg. bank...so I should probably leave that alone
too until I try it with a passenger...oops..i mean CFI.

Seriously, if someone has something to suggest that's fun and safe,
within normal operating range and category, please suggest. It's a
buddy's bday soon and he wants to go up. Again, I am not looking for
doing anything aerobatic.

Alright, I can see the flames and derision coming from the mainland

May you have a peaceful week with no stress,
Alex

If you want to do this sort of thing, get some aerobatic instruction.
And do it in an acro aircraft. As you describe what you want to do,
it has a definite "Hey, watch this" ring to it. It's POSSIBLE to do
acro in a normal/utility category plane - as Bob Hoover has shown -
but you have to be VERY good if you're not going to break
anything. (Also it's illegal unless you reclassify the aircraft as
experimental, which brings a whole lot of other restrictions).

You should definitely not try ANY of this stuff unless you have
done some proper spin recovery training. A 172 is legal and safe to spin
(if loaded correctly) but if you haven't experienced a spin there
is a serious risk that you will panic. None of us wants to read about
you in an NTSB report.

That said... a 2G 60 degree banked turn is no big deal. Presumably
you have already done 45 degress (1.4G). Bank a bit further and
pull hard enough to maintain level flight. In a 172 it requires a fairly
strong pull but no huge deal (unlike the 182). Use the AI and
altimeter to keep track of what you're doing. Be VERY careful not
to bank a degree more than 60 degrees. At 70 degrees you are at
the limit of what the plane can take.

Floating in a 172 will stop the engine, and if you go even slightly
negative for more than a fraction of a second, will also cover the belly
of the plane with oil. This will not make you popular with the FBO.
As long as you push gently and stop before you hit zero G, nothing
bad will happen.

As soon as you start doing things like this you risk stalling and spinning.
You need to have an instinctive recovery action from an incipient
spin (opposite rudder), which takes a bit of practice - with a
spin-experienced instructor sitting beside you.

Get some acro training. It's loads of fun and will mean you can do
"extreme" non-acro stuff like this with no risk

John


"Koopas Ly" wrote in message
om...
Me again,

Va seems to be only intended to protect against excessive positive
load factors. What about negative g's?

Can I find a Va for negative design load factors (-1.52 g) for the
C172SP anywhere?

Reason I am asking is that I want to try the "floating pencil" trick
next time I fly but I don't want to shove the stick fully forward for
fear of breaking something. I am not looking to induce negative g's,
only zero g's and zero lift. Any pointers on entry speed and power
settings? Is it easier to perform if you induce a gradual +1 g steep
climb similar to a departure stall maneuver, then upon hearing the
stall horn, give it good nudge forward on the stick? I've heard that
your airspeed may indicate well below stall, but again, your stall
speed does approach zero as your load factor goes to zero.

Likewise, would you prefer to pull 2 positive g's in a pull-up
maneuver or a, say, 60 deg. bank? Frankly, I am not too familiar with
the former so I might do something undesirable. Aside from my stall
speed going up to something like 68 kts. clean (Va ~ 100 kts), you'd
see your airspeed quickly dwindling while pulling up. I think it'd be
fruitless to add in power since heck, you're not maintaining altitude
and besides, you probably don't have any excess power anyway to do
that. Neither am I familiar with the mechanics of loops so it'd be
wiser to leave that alone. Perhaps the 60 deg. bank is more
reasonable to have some fun. Would you try to hold altitude with
backpressure and power or just leave the plane to dive and speed up in
the spiral, with a recovery before Vne? I think the maneuver would be
more innocuous with power-off a-la-emergency-descent style. Again,
I've never done a 60 deg. bank...so I should probably leave that alone
too until I try it with a passenger...oops..i mean CFI.

Seriously, if someone has something to suggest that's fun and safe,
within normal operating range and category, please suggest. It's a
buddy's bday soon and he wants to go up. Again, I am not looking for
doing anything aerobatic.

Alright, I can see the flames and derision coming from the mainland

May you have a peaceful week with no stress,
Alex

Good response, John.
The note about the oil on the belly is the mark of someone who knows.

Get acro instruction in a Pitts, Decathlon, etc. Doing what you want in a
172, while maybe possible, is dangerous and quite honestly, a little sad.
It's like trying to race a Geo Metro. I've got nothing against the 172,
it's just not well suited for what you want. The FBO I rent from rents a
Decathlon for $10/hr more than their SP's. I'm sure you can find one for
about what you pay for the 172.

BTW - your comment "stall horn, give it good nudge forward on the stick"...
a 172SP doesn't have a stick, it has a wheel. Sticks are for acro's, a 172
isn't an acro.




"Koopas Ly" wrote in message
om...
Me again,

Va seems to be only intended to protect against excessive positive
load factors. What about negative g's?

Can I find a Va for negative design load factors (-1.52 g) for the
C172SP anywhere?

Reason I am asking is that I want to try the "floating pencil" trick
next time I fly but I don't want to shove the stick fully forward for
fear of breaking something. I am not looking to induce negative g's,
only zero g's and zero lift. Any pointers on entry speed and power
settings? Is it easier to perform if you induce a gradual +1 g steep
climb similar to a departure stall maneuver, then upon hearing the
stall horn, give it good nudge forward on the stick? I've heard that
your airspeed may indicate well below stall, but again, your stall
speed does approach zero as your load factor goes to zero.

Likewise, would you prefer to pull 2 positive g's in a pull-up
maneuver or a, say, 60 deg. bank? Frankly, I am not too familiar with
the former so I might do something undesirable. Aside from my stall
speed going up to something like 68 kts. clean (Va ~ 100 kts), you'd
see your airspeed quickly dwindling while pulling up. I think it'd be
fruitless to add in power since heck, you're not maintaining altitude
and besides, you probably don't have any excess power anyway to do
that. Neither am I familiar with the mechanics of loops so it'd be
wiser to leave that alone. Perhaps the 60 deg. bank is more
reasonable to have some fun. Would you try to hold altitude with
backpressure and power or just leave the plane to dive and speed up in
the spiral, with a recovery before Vne? I think the maneuver would be
more innocuous with power-off a-la-emergency-descent style. Again,
I've never done a 60 deg. bank...so I should probably leave that alone
too until I try it with a passenger...oops..i mean CFI.

Seriously, if someone has something to suggest that's fun and safe,
within normal operating range and category, please suggest. It's a
buddy's bday soon and he wants to go up. Again, I am not looking for
doing anything aerobatic.

Alright, I can see the flames and derision coming from the mainland

May you have a peaceful week with no stress,
Alex

Can I find a Va for negative design load factors (-1.52 g) for the
C172SP anywhere?

I think I calculated Vs for a negative AOA to be about 60 knots in a
172. That would put Va at about 74 knots.

Like many speeds in an airlane, maneuvering speed, Va, is related to
the wings-level, stall speed Vso by the square root of the g-load.
There is a positive side and a negative side.

For example, for Normal category, positive g operations, where the
design limit is +3.8-g, Va = 1.95 x Vso. (Note: this relationship
applies to CAS, so you must use the airspeed calibration figures in
the POH to move back and forth between IAS and CAS to find the actual
number you should see on the airspeed indicator).

If you know the wings-level, -1.0-g stall speed of the airplane (which
will in all likelihood be greater than the upright Vso), then you can
find the inverted Va, which will be 1.23 x the inverted Vso. Of
course, the inverted operating envelope is quite small.

As for your "trick" -- sure, it's something that can be done from a
steep climb followed by a pushover as the speed decays. But EVERYTHING
that is not bolted down in the airplane will float, not just the
pencil -- flashlights, flight bags, dirt, towbars, etc. And if the g
is too light, the engine may balk...

I'd recommend trying it with an instructor in an aerobatic airplane
instead.

Rich
http://www.richstowell.com


(Koopas Ly) wrote in message . com...
Me again,

Va seems to be only intended to protect against excessive positive
load factors. What about negative g's?

Can I find a Va for negative design load factors (-1.52 g) for the
C172SP anywhere?

Reason I am asking is that I want to try the "floating pencil" trick
next time I fly but I don't want to shove the stick fully forward for
fear of breaking something. I am not looking to induce negative g's,
only zero g's and zero lift. Any pointers on entry speed and power
settings? Is it easier to perform if you induce a gradual +1 g steep
climb similar to a departure stall maneuver, then upon hearing the
stall horn, give it good nudge forward on the stick? I've heard that
your airspeed may indicate well below stall, but again, your stall
speed does approach zero as your load factor goes to zero.

Likewise, would you prefer to pull 2 positive g's in a pull-up
maneuver or a, say, 60 deg. bank? Frankly, I am not too familiar with
the former so I might do something undesirable. Aside from my stall
speed going up to something like 68 kts. clean (Va ~ 100 kts), you'd
see your airspeed quickly dwindling while pulling up. I think it'd be
fruitless to add in power since heck, you're not maintaining altitude
and besides, you probably don't have any excess power anyway to do
that. Neither am I familiar with the mechanics of loops so it'd be
wiser to leave that alone. Perhaps the 60 deg. bank is more
reasonable to have some fun. Would you try to hold altitude with
backpressure and power or just leave the plane to dive and speed up in
the spiral, with a recovery before Vne? I think the maneuver would be
more innocuous with power-off a-la-emergency-descent style. Again,
I've never done a 60 deg. bank...so I should probably leave that alone
too until I try it with a passenger...oops..i mean CFI.

Seriously, if someone has something to suggest that's fun and safe,
within normal operating range and category, please suggest. It's a
buddy's bday soon and he wants to go up. Again, I am not looking for
doing anything aerobatic.

Alright, I can see the flames and derision coming from the mainland

May you have a peaceful week with no stress,
Alex

Actually it's the mark of someone who has been warned MANY times
by his acro instructor :-) (so far! - :-) that is ). But now I'm flying the
Decathlon - yippee! - which has inverted systems.

John

"EDR" wrote in message
...
Good response, John.
The note about the oil on the belly is the mark of someone who knows.

"Rich Stowell" wrote in message
om...
Like many speeds in an airlane, maneuvering speed, Va, is related to
the wings-level, stall speed Vso by the square root of the g-load.


I have a horrible premonition that we're about to rehash
the "Overweight takeoff" thread again.....

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

In article 1070298215.906416@sj-nntpcache-3, John Harper
wrote:

Actually it's the mark of someone who has been warned MANY times
by his acro instructor :-) (so far! - :-) that is ). But now I'm flying the
Decathlon - yippee! - which has inverted systems.

Is your slobber tube vented for cold weather operation?
Or, do you live where it stays warm?

(Koopas Ly) wrote in message . com...
Me again,

Va seems to be only intended to protect against excessive positive
load factors. What about negative g's?

Can I find a Va for negative design load factors (-1.52 g) for the
C172SP anywhere?

Reason I am asking is that I want to try the "floating pencil" trick
next time I fly but I don't want to shove the stick fully forward for
fear of breaking something. I am not looking to induce negative g's,
only zero g's and zero lift. Any pointers on entry speed and power
settings? Is it easier to perform if you induce a gradual +1 g steep
climb similar to a departure stall maneuver, then upon hearing the
stall horn, give it good nudge forward on the stick? I've heard that
your airspeed may indicate well below stall, but again, your stall
speed does approach zero as your load factor goes to zero.

It can be done from cruise speed. Pull up into a shallow climb,
then start pushing forward, increasing pressure until the pencil comes
off the panel. It'll feel like negative G's but isn't. The only stress
on the airplane occurs when you pull out of the shallow dive created
by the maneuver. You don't have to get the nose way up or down at all,
and it doesn't require abrupt, or anywhere near full, control inputs.
Kids love it.
MAKE SURE EVERYTHING IS TIED DOWN IN THE CABIN. Floating cargo
can depart through a window or it can come down hard on the pullout
and damage something.


Dan