Hurricane hunters?

Wow.

Just... wow.

What I still don't understand is how these aircraft are not overstressed,
and are able to keep control at all. I realise that this story is an extreme
example, but how about the "normal" flights? How do the planes survive?

Is it just because they are built to take the load factors?

"David Dyer-Bennet" wrote in message
...
"xerj" writes:

The site is down at the moment, but if I'm understanding it correctly, do
these guys actually penetrate hurricanes in P3s and Gulfstreams?

Do they go IMC flying into hurricane cloud???

If so, how the hell are they not constantly stalling as they are
buffetted
by the turbulence? I'm pretty sure that they'd slow down to maneuvering
speed, and I'd assume that there'd be moments when windshear would be
drastic

How the hell are these flights even technically possible??

Fascinating article on a semi-accidental penetration of Hugo in a
WP-3D (the accident was they didn't notice the storm had been
upgraded, and they probably wouldn't have chosen to make the
penetration given the actual state of the storm). With pictures.

http://www.wunderground.com/hurricane/hugo1.asp
--
David Dyer-Bennet, , http://www.dd-b.net/dd-b/
RKBA: http://noguns-nomoney.com/ http://www.dd-b.net/carry/
Pics: http://dd-b.lighthunters.net/
http://www.dd-b.net/dd-b/SnapshotAlbum/
Dragaera/Steven Brust: http://dragaera.info/

"xerj" wrote in message
...
What I still don't understand is how these aircraft are not overstressed,
and are able to keep control at all. I realise that this story is an
extreme example, but how about the "normal" flights? How do the planes
survive?

High winds do not necessarily mean high turbulence or high wind shear.

Of course, those characteristics *could* exist. But just because the wind
is whipping around at 160 mph, that doesn't mean you can't fly into it
without overstressing an airplane (any airplane).

A hurricane involves a wide variety of meterological phenomena, including
high winds, convection, rain, etc. My understanding is that the hurricane
pilots use radar to avoid the strongest convective areas where severe
turbulence and wind shear would be present.

There probably are areas within a hurricane that would tear any airplane
apart. Those who fly into them strive to avoid those areas.

Pete

I did fly through a hurricane (typhoon) at an altitude
of about 500'. Yes, it was rough! Yes, we were IMC a lot of the time.

Back in the early '50s, before wx radar, we blundered into a hurricane
in an R5C (C-46). Flew right through the eye. We were probably at
around 10,000' altitude.

It was not especially rough, but we had extreme rain that was causing
problems with the Curtiss electric props and causing the fire warning
light to light up.

It took an unbelievable anount of drift correction to stay on the A-N
range leg, and after the eye, an equally unbelievable amount in the
opposite direction. We still didn't recognize that we were in a
hurricane, till we were told after we landed.

vince norris

What I still don't understand is how these aircraft are not overstressed,
and are able to keep control at all. I realise that this story is an extreme
example, but how about the "normal" flights? How do the planes survive?

Is it just because they are built to take the load factors?

Perhaps you are not a pilot and hence are not aware that if the plane
is flown at "maneuvering speed," the wing will stall before the stress
is sufficient to cause it to break.

vince norris

Peter Duniho wrote:

Perhaps you are not a pilot and hence are not aware that if the plane
is flown at "maneuvering speed," the wing will stall before the stress
is sufficient to cause it to break.

For what it's worth "maneuvering speed" ensures only a certain degree of
safety. A strong enough gust can still overstress the airframe, with or
without a stall.

Actually, the maneuvring speed is the max speed at which full deflection
of the controls is still allowed and it is completely unrelated to
gusts. What you both mean is the max speed for tubulent air. Both speeds
are often indicated the same, but I suspect this is just to keep things
simple for the average low time spam can pilot.

The answer to why an airplane can be torn apart by a gust even when
flying below the allowed speed for turbulent air is simple: When the
gusts are strong enough, they will just "gust" you above that speed.

Stefan

"Stefan" wrote in message
...
Actually, the maneuvring speed is the max speed at which full deflection
of the controls is still allowed and it is completely unrelated to gusts.
What you both mean is the max speed for tubulent air.

Yes. I didn't see any point in further confusing the poster to whom I
replied by trying to address the terminology issue at the same time. He
clearly had a specific speed in mind that was related to gusts, but that
speed does not guarantee airframe integrity under all possible conditions.

[...]
The answer to why an airplane can be torn apart by a gust even when flying
below the allowed speed for turbulent air is simple: When the gusts are
strong enough, they will just "gust" you above that speed.

That "answer" is also incomplete. The airframe can be damaged without the
relative wind rising above the relevant certificated maximum speeds.

Pete

Stefan wrote
Actually, the maneuvring speed is the max speed at which full
deflection of the controls is still allowed and it is completely
unrelated to gusts.

Stefan...I've been fighting this common misconception here on
this newsgroup for years and the spam-can pilots just don't seem
to understand. It probably goes back to their basic instruction
and a few well intentioned but misguided magazine writers.

As you point out, maneuvering speed (Va) is related to pilot
induced loads and gust loads are related to Vno, the top of the
green arc on the airspeed indicator for small airplanes, it's Vb
for newer and larger airplanes.

There are actually two "g" envelopes for an airplane. One for
maneuver loads and another for gust loads. When overlayed, they
form the combined envelope. The gust loading envelope is required
to accomodate the most severe gust that it is anticipated that the
airplane will encounter in normal flying operations.

Although both of these loads are actual physical phenomena, the FAA
has defined them in the FARs via Part 23. The information is
scattered in several sections of Part 23, but when specifying the
gust loading requirements, nowhere is Va mentioned, and likewise,
when specifying the maneuver loading requirements, there is no mention
of Vb or Vno (the top of the green arc).

From the FAR:

Section 23.423: Maneuvering loads.
Each horizontal surface and its supporting structure, and the main wing
of a canard or tandem wing configuration, if that surface has pitch
control, must be designed for the maneuvering loads imposed by the
following conditions:

(a) A sudden movement of the pitching control, at the speed VA, to the
maximum aft movement, and the maximum forward movement, as limited by
the control stops, or pilot effort, whichever is critical.

Section 23.333: Flight envelope
(c) Gust envelope. (1) The airplane is assumed to be subjected to
symmetrical vertical gusts in level flight. The resulting limit load
factors must correspond to the conditions determined as follows:

(i) Positive (up) and negative (down) gusts of 50 f.p.s. at VC must be
considered.........

(ii) Positive and negative gusts of 25 f.p.s. at VD must be
considered...........

Section 23.1545: Airspeed indicator.
(a) Each airspeed indicator must be marked as specified in paragraph (b)
of this section, with the marks located at the corresponding indicated
airspeeds.
(3) For the normal operating range, a green arc with the lower limit at
VS1 with maximum weight and with landing gear and wing flaps retracted,
and the upper limit at the maximum structural cruising speed VNO
established under §23.1505(b).

Section 23.1505: Airspeed limitations.
(b) The maximum structural cruising speed VNO must be established so
that it is --
(1) Not less than the minimum value of VC allowed under §23.335


Quoted from Aerodynamics for Naval Aviators:

"As a general requirement, all airplanes must be capable of withstanding
an approximate effective +/- 30 foot per second gust when at maximum
level flight speed for normal rated power. Such a gust intensity has
relatively low frequency of occurrence in ordinary flying operations.
The highest reasonable gust velocity that may be anticipated is an
actual veritical velocity, U, of 50 feet per second."

Now, I ask, why, when flying in gusty conditions, do pilots slow to Va?
The airplane (by regulation) is designed to withstand the highest
reasonable gust velocity at the top of the green arc? Slowing to Va
presents a definate stall-upset possibility where the pilot is apt to
induce a maneuvering overstress during the recovery.

Bob Moore

Peter Duniho wrote:

That "answer" is also incomplete. The airframe can be damaged without the
relative wind rising above the relevant certificated maximum speeds.

I think there is a maximum gust amplitude for which the integrity of the
airframe is guaranteed. Don't know how much it is nor where that would
be defined, though. (Most probably in the FARs (USA) or the JARs
(Europe), but I'm not going to search.)

Stefan

"Stefan" wrote in message
...
I think there is a maximum gust amplitude for which the integrity of the
airframe is guaranteed.

There is, and a gust greater than that may damage the airframe. Regardless
of what airspeed one is flying.

Which is what I said.

The bottom line: there is no speed at which one can guarantee the airframe
won't be damaged. Even sitting still on the ground, it is theoretically
possible to have a strong enough wind to damage the airframe.

"Safe" flight through a hurricane involves a LOT more than just picking the
right airspeed.

Pete

vincent p. norris wrote:
I did fly through a hurricane (typhoon) at an altitude
of about 500'. Yes, it was rough! Yes, we were IMC a lot of the time.

Back in the early '50s, before wx radar, we blundered into a hurricane
in an R5C (C-46). Flew right through the eye. We were probably at
around 10,000' altitude.



My dad has a ton of C-46 time. He was in a troop carrier squadron based out of
Tachikawa, Japan during the Korean War until 1955.



--
Mortimer Schnerd, RN

VE