OT B-2 crash video

Damon Hill wrote:

Looked like they almost recovered, too. Bet there'll be a big overhaul
of flight software since that might have been frustrating their effort
to reassert control.

That's the problem with full fly-by-wire; if the computers screw up, you
can't go back to manual control.
Complete fly-by-wire makes sense for a fighter, where you want the
natural stability to be very limited to accentuate maneuverability...but
on something like the B-2 it may well be counter-productive. It was
never designed or stressed to be any sort of a aerobatic aircraft.
Even the Shuttle (to bring this back on-topic) doesn't have any sort of
manual flight regimen where the pilots can actually take full manual
control of it without the computers interpreting their control inputs
and moving the control surfaces to do what's intended.
In that case it makes sense - the Shuttle is very limited from a
natural stability point of view, and uses redundant computers to allow
it to fly inside the atmosphere from reentry on down.
On the other hand, the Shuttle never had to deal with a SAM going off in
near proximity to it and damaging its airframe with the shrapnel
-disabling some of its electronics. Combat aircraft have to deal with
that possibility.

Pat

"Reunite Gondwanaland (Mary Shafer)" writes:


Don't confuse highly-augmented flight control systems with
fly-by-wire. They're inextricably linked in many people's minds, but
they truly are entirely separate.


What was Mercury's Fly by Wire? I recall mentions of it by the PAO...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Rick Jones wrote:
Isn't the flying wing how Edwards AFB got its name - that the initial
plane(s) were very unforgiving in a stall and it wasn't until FBW that
one could "reliably" (this crash notwithstanding) fly such a thing?


I built and flew a lot of flying wing glider models; their stall
characteristics are horrible.
They're great as gliders, except for the lack of yaw stability*, but put
power on them and you are asking for trouble.
In stall, they climb straight nose-up, then backslide through the air
trailing-edge first till they end up in a nose-first dive.
Edward's YB-49 apparently did that, breaking apart as it reared up
belly-first into the airstream.
You can see a less severe version of that with the B-2 video - as the
aircraft climbs at way-too-high of a angle of attack as it leaves the
runway. A conventional design of aircraft would have lost lift and speed
way before it hit that pitch angle, and basically have gone sloshing
through the air, letting the crew pancake it back onto the runway at
worst, and letting it never completely leave the runway at best.

* They soar like gulls!
Had one get around a 20-to-1 glide ratio; (one foot drop in altitude for
every twenty feet of forward flight) ... if there'd been even mild
thermals that day it might have just vanished into the sky and ended up
somewhere in South Dakota. :-)

Pat

Derek Lyons wrote:
And they used to fly aluminum versions in the 40s and 50s without
FBW...


And the lack of FBW is why we didn't keep flying them.


Honeywell did come up with a autopilot for the YB-49 that prevented its
constant pitch and yaw hunting as it flew, but the problem was -
particularly in pitch - if you went outside of around of ten degrees of
optimal you were in a situation where the aircraft would increase its
divergence from the airstream beyond the ability of its control surfaces
to correct it, and would break up.
The B-2 solves this problem with its fly-by-wire controls allowing the
aircraft itself to monitor its pitch angle constantly, and never letting
it get fatally out of line.
The B-2's solution to the yaw problem is pretty crude when you get right
down to it; it uses the patented Northrop "Flaperlons" - ailerons that
split into upper and lower halves to serve as drag brakes on the outer
wings to cause more drag on one side of the aircraft than the other, to
keep it flying nose-first into the airstream in lieu of vertical
surfaces (see the video of the crash as they are opening pretty much
fully in an attempt to keep it flying straight) were built into the design.
Although this works, it generates a whole lot of drag; and the B-2
seems to have them opened to some extent during its whole flight
profile...which works against the drag advantages of the pure
flying-wing design.
Pilots always thought they were walking a tightrope while flying the
YB-49, and just one wrong move would get them into a situation where the
aircraft would fall apart in a matter of seconds.
This led to the case where one of the flying-wing bombers suffered a
nose gear collapse on landing, and the pilot told the firefighting team
to let it burn up... as he never wanted to have to fly it again.

Pat

"T. B." partyslammer@socalrrcom wrote in message
...
"Alan Erskine" wrote:

"Damon Hill" wrote:

dakotatelephone:

It almost appears *something* blew off the top of the plane at about the
1.58 point in the first video.

Crew ejection.

No, it's a few seconds earlier than the crew ejecting. It's just as the
front wheel lifts off the runway.


I think that's just an illusion from passing in front of some sort of
drainage grate behind teh runway.

--
Terrell Miller


"If computers get too powerful, we can organize them into a committee - that
will do them in."
- Bradley's Bromide

Pat Flannery wrote:

Although this works, it generates a whole lot of drag; and the B-2
seems to have them opened to some extent during its whole flight
profile...which works against the drag advantages of the pure
flying-wing design.

This wouldn't be the first time that a real physical object didn't
quite live up to the specs of it's paper predecessor.

D.
--
Touch-twice life. Eat. Drink. Laugh.

http://derekl1963.livejournal.com/

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

On Jun 7, 3:22 pm, Pat Flannery wrote:

Pilots always thought they were walking a tightrope while flying the
YB-49, and just one wrong move would get them into a situation where the
aircraft would fall apart in a matter of seconds.

Kind of like driving a car in that respect

Derek Lyons wrote:

Although this works, it generates a whole lot of drag; and the B-2
seems to have them opened to some extent during its whole flight
profile...which works against the drag advantages of the pure
flying-wing design.


This wouldn't be the first time that a real physical object didn't
quite live up to the specs of it's paper predecessor.


Northrop first designed them for their flying wing fighter and bomber
designs to take the place of vertical fins and rudders.
IIRC, they were first used operationally on the F-89 Scorpion, where
they served as both ailerons and airbrakes.
You can see them in the partially open position on this in-flight B-2
photo: http://www.photosfan.com/images/stea...-b2-bomber.jpg
Back on the XP-56 and XP-79B they were driven by airscoops on the wingtips:
http://jpcolliat.free.fr/north/image...ematic_top.gif
http://jpcolliat.free.fr/north/images/xp-79b_05.jpg

Pat

Neil Gerace wrote:


Pilots always thought they were walking a tightrope while flying the
YB-49, and just one wrong move would get them into a situation where the
aircraft would fall apart in a matter of seconds.


Kind of like driving a car in that respect


The stability problems get discussed he
http://www.aerospaceweb.org/aircraft/bomber/yb49/

Pat

Pat Flannery wrote:

The stability problems get discussed he
http://www.aerospaceweb.org/aircraft/bomber/yb49/

This is a interesting multi-page article about the how the whole flying
wing bomber concept flopped in its first incarnation:
http://findarticles.com/p/articles/m..._81763173/pg_1

Pat