
Enroute Airbus A380 wake flips Challenger business jet upside down - mustpax
http://flightservicebureau.org/enroute-a380-wake-flips-challenger-604-upside-down/
======
phumbe
For anyone interested, there are several great youtube videos[1-4] that show
the wakes (the wingtip vortices in particular) created by various aircraft.

This incident brings the Reduced Vertical Separation Minima (RVSM)[5] into
question. Strategic Lateral Offset Procedure (SLOP)[6] can be used used to
avoid such incidents.

[1]
[https://www.youtube.com/watch?v=E1ESmvyAmOs](https://www.youtube.com/watch?v=E1ESmvyAmOs)

[2]
[https://www.youtube.com/watch?v=dfY5ZQDzC5s](https://www.youtube.com/watch?v=dfY5ZQDzC5s)

[3]
[https://www.youtube.com/watch?v=uy0hgG2pkUs](https://www.youtube.com/watch?v=uy0hgG2pkUs)

[4]
[https://www.youtube.com/watch?v=KXlv16ETueU](https://www.youtube.com/watch?v=KXlv16ETueU)

[5]
[https://en.wikipedia.org/wiki/Reduced_vertical_separation_mi...](https://en.wikipedia.org/wiki/Reduced_vertical_separation_minima)

[6]
[https://en.wikipedia.org/wiki/Strategic_lateral_offset_proce...](https://en.wikipedia.org/wiki/Strategic_lateral_offset_procedure)

~~~
csours
Those wingtip and flap effects on 2 are gnarly! I assume that those occur near
dewpoint? or some other atmospheric conditions?

~~~
cyberferret
If you recall Boyle's Law from high school physics - Temperature is
proportional to pressure. Aircraft wings generate an intense area of low
pressure over the top of the wing (which is what essentially generates the
lift). This low pressure area is magnified when flaps and slats are deployed.

On a humid day, the lowering of the pressure over the wings can basically
force the air temperature at that point to lower and reach dew point
temperature, essentially forming temporary clouds that are whipped around by
the moving air vortices.

Once the aircraft has passed that point, the temperature generally stabilises
and conforms to surrounding air temperature, which usually dissipates the
temporary condensation.

The 'twirly' bits on the wingtips is basically spillover from the high
pressure under the wings to the low pressure above the wings, creating that
mini tornado vortex. This is also the reason that many modern aircraft have
those 'winglets' on the wingtips, to try and minimise these spillover vortices
which can cause problems for trailing aircraft, as well as induce extra drag
on the source aircraft.

~~~
Zak
Wings generate lift primarily by deflecting air downward. There is an area of
low pressure over the wing where air is taking a longer path than under the
wing, but that is only responsible for a small fraction of the lift.

~~~
nether
"Longer path" has no bearing on reality. A flat plate can generate plenty of
lift even with both sides the same. It's also hard to define "path," as the
air starts convecting well ahead of the wing in subsonic flow.

~~~
cyberferret
Sorry, but I don't subscribe to the 'flat plate' theory. There is a reason
that almost every commercial (and most military) aircraft have leading edge
slats to generate lift at lower speeds (by making the top of the wing more
convex and the bottom of the wing more concave).

If _pure_ 'flat plate' theory was valid, then all those aircraft speeding down
the runway with the leading edge of their wings canted downwards 20 or so
degrees would result in the airplanes simply being pushed towards the ground
and never lifting off...

And Boeing, Airbus et al would build planes with flat slab wings mounted at a
45 degree angle to the airflow, because that would give the maximum lift by
the 'flat plate' theory, wouldn't it?

Not that I disbelieve that a flat slab cannot generate lift - but that it is
probably a very inefficient way to generate lift compared to the standard
aerofoil shape.

[0] -
[https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Bo...](https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Boeing_727-2S7_Advanced_Champion_LAX.jpg/1200px-
Boeing_727-2S7_Advanced_Champion_LAX.jpg)

[1] -
[https://www.metabunk.org/sk/20141127-081301-jrgr5.jpg](https://www.metabunk.org/sk/20141127-081301-jrgr5.jpg)

~~~
dorfsmay
The shape of the wing makes a huge difference, so a plate or a piece of wood
wouldn't make a good wing, but it is still able to fly.

Proof? Inverted flight on low power aircraft and gliders.

~~~
cyberferret
And as I have mentioned elsewhere on here - I have flown inverted a few times,
and to do so take a tremendous amount of _forward_ pressure on the control
stick to even try and attempt to hold altitude while inverted, in order to
counteract the wings natural (slight) positive AoA and the tendency for the
wing to move towards it upper surface. In fact, most of the aircraft I have
flown would not be able to sustain inverted flight at all. The fact that full
aerobatic and military jets do, is because they (as I explained earlier)
usually don't have that curved 'fish' shape cross section, but are usually
symmetrically shaped on the top and bottom of the wing.

To whit, I've had the fortune to fly an old DH Tiger Moth biplane - on that
little baby, when you approach the stalling point, you can actually see the
the canvas on _top_ of the bottom wing bulge and contort with pressure
differential, and you can hear the sucking sounds as the airflow struggles to
'stick' to the wing. There is a little movement on the bottom surface of the
top wing too, but not as pronounced.

I'd be interested to see in this thread, who here has actually studied
aeronautical engineering, or flown actual aircraft, and who is relying on YT
videos or a pure theoretical approach to come up with these theories?

Also interestingly, I believe most of the textbooks I used at flight school
were filled with data from NASA and other US military branches with regards to
flight dynamics etc., and here on this thread we see articles from NASA
(albeit aimed at K-12 audience rather than trainee pilots) basically
disproving their earlier academic research.

~~~
votingprawn
> I'd be interested to see in this thread, who here has actually studied
> aeronautical engineering

I studied Aerospace Engineering (PhD in Aerodynamics), and I stay out of
internet conversations over "how" lift is generated. For me it is one of those
topics that is just not worth debating. It seems that people get _really_
attached to their personally preferred theory of lift.

~~~
dhimes
Can you point to a source for those of us who want to know the right answer
(like, sailors)?

~~~
jabl
Not the previous poster, but this was on HN a week ago:

[http://ljjensen.net/Maritimt/A%20Review%20of%20Modern%20Sail...](http://ljjensen.net/Maritimt/A%20Review%20of%20Modern%20Sail%20Theory.pdf)

[https://news.ycombinator.com/item?id=13829625](https://news.ycombinator.com/item?id=13829625)

~~~
dhimes
Perfect. Thank you!

------
lutorm
This is a reminder that the announcement that you should "keep your seat belt
fastened at all times when you're in your seat" isn't just something someone
made up. It's a small price to pay in case you ever encounter severe
turbulence en route, but it might be one of these things that most people
don't realize until it happens to them. Hitting your head against the cabin
ceiling can seriously put a damper on your trip.

~~~
taejavu
Yeah I'm pretty sure that's the first rule that goes out the window when
you're on a private jet.

~~~
M_Grey
There's a reason that people with money and power don't always experience good
outcomes. Sure, you can do what you like on your jet, and therefore expose
yourself to risk that most people never experience. Likewise skiing off-piste
or a number of other equally silly activities that you _can_ do, but
absolutely shouldn't.

~~~
fulafel
Probably they have a different idea about risk management than more risk-
averse people. Worrying a lot about very low probability events is not
compatible with the risk-taking typically required to make a lot of money.
After all millionaires are largely a "survivor club" filtered from high risk
appetite workaholics.

~~~
M_Grey
I don't know about that. I think mostly it has to do with having the power to
pick and choose critical service providers, bully them, etc. If Michael
Jackson and Steve Jobs had not been as wealthy and powerful as they had been,
they would also both probably be alive.

Neither has much to do with being risk-takers, although you might be right
that a higher arousal threshold desensitized them to risk. It may also be that
people used to winning, on some level, expect to keep winning. Either way,
we're not just talking about Fortune 500 C-levels here, plenty of people with
loads of money and power did nothing to get it, and have no special qualities
associated with that ability to get it.

They still often have bad outcomes.

~~~
komali2
I feel like Steve Jobs is an odd choice... He turned down treatment I thought?

~~~
redler
He wasted precious time indulging quackery.

~~~
tluyben2
Anecdotal but I notice in my circles only less financially well off people
endulge in quackery. The latest is that you do not need treatment for anything
if you do enough marijuana and reiki (not to mention a lot of poor people burn
their last money on reiki training....) especially not doing chemo when they
sbould is hard to witness.

~~~
pm
I can't say I know anyone who's indulged reiki, but I've got a lot of flak
from my brother telling me that cannabis cures cancer, when I told him that I
was doing chemoradiotherapy for my Stage 3 rectal cancer. Today I've finished
a cycle of six weeks of treatment, and while I'm extremely tired, the signs
are good that it's in remission. If I'm lucky, I'll have a full pathological
response, i.e., it's gone.

Despite the number of people who go through cancer, it's rarely brought up in
polite conversation. It wasn't until I got it myself that all manner of people
came out of the woodwork to talk about how someone they knew had gone through
the same thing. Many of them have been using concentrated cannabis oil (which
my brother also said I should do). After reading a couple of studies, it does
have a positive effect on cancers, but the level depends on the type of
cancer. In the case of colorectal cancers, it seems to stop the cancer but not
kill it, most likely due to the CB1 receptors in the tumour being
hypermethylated (as in, the gene isn't being expressed). The level of evidence
isn't that of a systematic review, but it's enough for me to give it a go and
certainly enough for further research. Unfortunately, the two sides of the
argument seem to think that it either doesn't do anything (there's not enough
evidence) or that the medical establishment is just a ruse and that cannabis
cures all cancer. I prefer to use my critical thinking skills and get the best
of both worlds.

I can understand why people might indulge in quackery - I've got surgeons
telling me they need to cut out my rectum and part of my lower intestine, even
with a full pathological response. Possible side effects are shitting 3 times
a day (not so bad) and erectile dysfunction (worse). This has been the gold
standard of care for 15+ years now, and the surgeons don't give a fuck about
my quality of life, they just want to cut. There's mounting evidence to show
this might be overtreating the problem, and that you can get away with a
heavier dose of chemo with the radiotherapy. Frankly, I don't want anyone
cutting anything out of me unless it's absolutely necessary, but it's hard
finding an advocate who would be willing to tell the surgeons to fuck off.

I'm lucky, in this sense: I understand the research and I have access to
upcoming studies (I used to work at an institute that did systematic reviews
of evidence). Most people won't have such advantages, so they just sit there
and do what the surgeons tell them to do, as if they don't have any options
other than no treatment. If that's all the choice I got, I'd be wary of the
medical establishment too.

~~~
komali2
I'm not sure about cannabis _curing_ cancer, but there's ample research to
support that it can help tremendously with the side effects of chemo.
Basically, it can make life more comfortable while you go through treatment.

~~~
tluyben2
I would advocate, for many reasons, taking regular treatment and cannabis at
the same time, but refusing regular treatment because cannabis will do it is a
bit over the top. I am a cancer survivor so people tend to talk to me about
it.

------
uptownfunk
Had to google around to understand wake turbulence. If I read the wiki
correctly, it's basically a horizontal tornado that emanates from the wings.
That would explain the rolling that the aircraft encountered.

On another note, I fly every week for work, can't imagine rolling five times
and engines losing power with a drop of 10k feet. That's absolutely insane.
I've had engines lose power before, but it was quickly regained such that the
drop was more moderate.

~~~
phumbe
It's helpful to think of an aircraft's wake in two parts.

The wing is deflecting air downward to provide lift; this creates a volume of
downward-moving air behind the aircraft.

There's higher pressure under the wing and lower pressure on top, so air from
below tries to get above the wing at the wingtips. This causes circulatory
motion, yielding wingtip vortices (see my top-level comment for some
visualizations).

~~~
nb777
Do you happen to know how arial refueling works then ? E.g. in this image [1]
the jet is flying where I would expect a lot of deflected air to be moving to
? Or is it just deflected much more steeply ?

[1]:
[https://upload.wikimedia.org/wikipedia/commons/d/d6/US_Navy_...](https://upload.wikimedia.org/wikipedia/commons/d/d6/US_Navy_041104-N-3799S-001_An_F-A-18F_Super_Hornet_conducts_in-
flight_refueling_from_an_U.S._Air_Force_KC-135_Stratotanker_assigned_to_the_Alaska_Air_National_Guard.jpg)

~~~
phumbe
The other two replies covered your questions well, so I'll just add that wakes
don't descend particularly fast. According to the FAA's Pilot's Handbook of
Aeronautical Knowledge[1] (page 14-28), "Tests have also shown that the
vortices sink at a rate of several hundred feet per minute, slowing their
descent and diminishing in strength with time and distance behind the
generating aircraft."

Considering the Challenger's encounter with the A380's wake, it took 1-2
minutes for the Challenger to hit the wake, so the wake probably had 1-3
minutes to make the 1000-foot descent. That very roughly fits the expected
"several hundred feet per minute" descent rate.

Considering the case of refueling, the wake's motion downward is much slower
than the aircrafts' horizontal motion, so it wouldn't have descended much by
the time it's left behind entirely.

[1] Available for free at
[https://www.faa.gov/regulations_policies/handbooks_manuals/a...](https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/)

------
jmts
This is quite interesting. I've been living underneath a flight plan for the
last few years, and every now and then I've noticed a strange noise that seems
to come from the air a few seconds after a plane has passed overhead on
approach. The best way I can describe it is as a tearing noise, somewhat like
a long stretched version of a tear in paper, or fabric. I've long suspected
that it may be due to turbulence, and this article certainly suggests that the
turbulence for some aircraft is much more powerful than I'd suspected.

~~~
dredmorbius
That's likely the sound of jetwash striking (nearly) stationary air as it
exits the engine.

I'm familiar with the roar of jets taking off. Some years back I happened to
be biking past an airport, at the end of the runway, just as a passenger jet
was lining up for takeoff, headed away from me. I thought I'd pause to watch.

Only as the engines spooled up did I think, "hrm, this could get loud".

 _It didn 't._

Instead, what I heard was ... the engines spooling up. Loud, yes, but not a
roar, just an increasing pitch, until the airplane started accelerating down
the runway.

It wasn't until some 15-20 seconds later that I heard the familiar roar,
echoing off of hills five or so miles away. That's when I realised that the
_whine_ was the sound of the turbines, but the _roar_ was the sound of exhaust
gas, streaming out of the engines, hitting stationary air and generating
intense turbulence, _and radiating outward in a perpendicular line to that
jetwash_. So I didn't hear it directly (it was moving away from me), only the
reflection (as that wall of noise, now reflected off the hills, was directed
back toward me.

I doubt the vortex would make any particularly loud sound, though you might
hear the rushing of air. Speeds are in the tens of miles per hour rather than
hundreds as with jetwash.

------
clueless123
Big problem is the use of autopilot navigation locked to the GPS route.. this
pretty much guarantees that you will fly right below the wake of the above
plane on the same route! (Before GPS it will be _very_ odd to flight exactly
the same path) ..

~~~
antubbs
Eh. e.g. the north atlantic tracks have been around since the 1960s. GPS
wasn't available to the public until Korean Air Lines Flight 007 in the 1980s.

~~~
dingaling
The OP means that satnav ensures that two aircraft on a reciprocal or
identical track will now pass over one another, whereas there used to be
navigational slop that would give some unintentional but useful lateral
displacement.

~~~
cjrp
Ironic that you should use the term 'slop', since that's exactly how they
avoid flying the same route across the Atlantic tracks for example (Strategic
Lateral Offset Procedure).

~~~
phumbe
Also worth noting for the transatlantic paths is the direction of traffic.
When it's morning in North America, traffic is predominately westbound. When
it's night, traffic is predominately eastbound.

Right now, it's the middle of the day (12:50p Central). There's a bit of a
mix[1], but it's still predominately westbound.

The consequence of this is that most traffic will be separated by at least
2000 feet. Eastbound traffic will (generally) be at odd Flight Levels (so
29000 feet, 31000 feet, etc.) while Westbound traffic will be at even FLs
(30000 feet, etc)[2]. This assumes RVSM airspace.

[1] I'm just looking at the transatlantic traffic on
[https://flightaware.com/live/](https://flightaware.com/live/)

[2]
[https://www.law.cornell.edu/cfr/text/14/91.179](https://www.law.cornell.edu/cfr/text/14/91.179)

------
jacquesm
The wakes of large aircraft are such that even big passenger planes make sure
to keep plenty of separation.

[https://en.wikipedia.org/wiki/American_Airlines_Flight_587](https://en.wikipedia.org/wiki/American_Airlines_Flight_587)

Is another example (though pilot error likely made a bad situation worse in
that particular incident).

~~~
cr4ig_
I was looking at FlightRadar24 and listening to ATC while an A380 took off
from Dulles near DC. Not only did they warn for wake turbulence when the plane
was already well away, they held other aircraft for a runway inspection after
the plane took off. I'd imagine that kind of wake could kick up some
significant debris on the ground as well.

~~~
Zombieball
I believe warning of wake turbulence is very common after take off of any
large and heavy aircraft.

Wingtip vorticies can sit over a runway (or even drift over to parallel
runways) for minutes after a takeoff. They are very dangerous to smaller
aircrafts.

The key to avoiding vorticies is to take off at a point earlier than the
previous aircraft and to climb at a steeper angle (vorticies travel behind and
downwards from the aircraft that made them).

Example: [http://www.boldmethod.com/images/learn-to-
fly/aerodynamics/a...](http://www.boldmethod.com/images/learn-to-
fly/aerodynamics/avoid-wake-turbulence-during-takeoff-and-landing/takeoff-
profile.jpg)

Helicopters can also produce serious turbulence as well!

~~~
mnw21cam
Helicopters. Indeed - there is a state known as "settling with power"
[https://en.wikipedia.org/wiki/Vortex_ring_state](https://en.wikipedia.org/wiki/Vortex_ring_state)
where a helicopter is sitting inside its own vortex, and is incapable of
climbing straight up with full power.

~~~
Zombieball
Super interesting! Never knew this about helicopters. Thanks.

------
jseip
The physics of this are insane. Then again, by my calculation the A380
displaces roughly 11 million cubic feet of air per second at the max landing
weight.

~~~
rjurney
Why does the landing weight effect the air it displaces?

~~~
thrill
Not displacement (volume), but pressure from velocity: lift. The amount of
lift by definition has to equal the weight of the aircraft at 1G.

~~~
vpribish
... and the force of that lift on the plane has an equal and opposite on the
air. A Heavier plane disturbs the air more.

------
foliveira
Good video of the same (similar?) effect on a small plane after taking off
after an Antonov-2

[http://www.youtube.com/watch?v=KXlv16ETueU](http://www.youtube.com/watch?v=KXlv16ETueU)

~~~
paganel
I just love An-2 planes. They can take off and land almost everywhere, they're
one of the slowest and lowest flying planes that I've ever seen (which I find
cool), plus the propeller/engine has a special sound. There's a couple of them
stationed just outside my parents' village in Eastern Europe, if you look on
the GMaps link that thing close to them it's actually a sheepfold
([https://www.google.ro/maps/@44.2288052,27.5250523,386m/data=...](https://www.google.ro/maps/@44.2288052,27.5250523,386m/data=!3m1!1e3?hl=en)).

~~~
mrkgnao
"It's Russian, hah."

------
peteretep
I've been on a widebody caught in an A380 wake before. Some seriously violent
turbulence for a few seconds, and the pilot came on afterwards to tell us what
happened.

------
gigatexal
Holy smokes that must have been terrifying. Glad nobody died. I hate flying as
it is (not that I'm likely to ever find myself in a private jet anytime soon).

------
Animats
Wow. Uncontrolled roll at least 3 times, maybe 5. G-loads severe enough to
damage the airframe beyond repair. And this was a 9-passenger bizjet, not a
tiny light single.

~~~
xaldir
Compared to an A-380 a 9-passengers bizjet _is_ a tiny feather.

------
lutusp
Pilots should be aware of wake turbulence and wingtip vortices in particular,
and should be aware that being at a lower altitude than the generating
aircraft is the most dangerous position (the vortex pattern is denser than the
surrounding air and therefore descends).

Also, an invisible vortex is no less turbulent for its invisibility.

------
bfrog
Landing at O'Hare in a smaller bombardier 2x2 (crj 700 I think) jet following
a jumbo was an interesting (white knuckle) ride I had in recent memory. The
plane turned over lake michigan east of the city and felt like it went
completely 90deg to the ground losing a good amount of altitude which I do not
believe was the pilots intention. I definitely heard a few gasps, the
stewardess curse and my wife grip my hand hard. Followed by 10 minutes of
bumps, drops, and wing waggling and a landing that felt like we simply dropped
10 feet on to the tarmac.

Those little jets man... they're fine most of the time but what a spooky
experience that was.

------
dbalan
IMO this has slightly better info:
[https://avherald.com/h?article=4a5e80f3&opt=0](https://avherald.com/h?article=4a5e80f3&opt=0)

------
itsdevlin
Tangentally related - We deal with this a lot in Wingsuit BASE jumping (well,
in wingsuit skydiving as well, but wake vortices and turbulence (aka
'burbles') have killed more than a few extremely talented pilots in the last
year).

It's fucking wild how small of a wing can put off a sizable wake. With
wingsuits, if you fly behind and slightly above a buddy, you're going to hit
his burble and you're going to immediately lose lift and possibly start
spinning. There's a clip floating around of a bunch of us on a training jump
in race suits and one of the guys hits a burble from the group and just gets
dropped a few hundred feet damn near immediately.

EDIT: Found it -
[http://giphy.com/gifs/cBP3YE9hf9oVa](http://giphy.com/gifs/cBP3YE9hf9oVa)

Here's a solid article that touches on it w/r/t lift - [http://base-
book.com/speed-to-fly](http://base-book.com/speed-to-fly)

...and here's one that's a bit more applied that has to do with how burbles
affect canopy deployments - [http://base-book.com/some-thoughts-on-wingsuit-
openings](http://base-book.com/some-thoughts-on-wingsuit-openings)

------
gingerbread-man
Right now, the vertical separation minima for aircraft worldwide are not
conditional on size. At altitudes above 28,000ft MSL, the minimum vertical
separation is 1000ft, even for superjumbos. It is probably a rare event that
two aircraft come so close both vertically _and_ horizontally, but I wonder if
there will be a rule change because of this incident nonetheless.

By contrast, the _horizontal_ separation minima vary dramatically based on the
size of the leading aircraft.

~~~
theWatcher37
The way the FAA tends to run things is rules are either written in blood or
incident reports.

------
nsgoetz
I don't know much about aviation, but 1000ft seems kinda close to pass another
aircraft. How normal is that distance?

~~~
goodcanadian
By law, 5 (nautical) miles horizontal separation or 1000 feet vertical
separation is required. When aircraft were smaller, that was probably more
than sufficient. The A380 is another beast entirely, though.

~~~
alkonaut
The question is then - are there any systems that can ensure that two airraft
aren't passing eachother at just 1000 feet if one of them is a behemoth? Will
the corridors magically widen when an A380 enters it?

Will nearby aircraft be warned when crossing right under an A380 that they are
basically on a collision course, while had it been a small aircraft it
wouldn't be a problem?

~~~
LoSboccacc
I never understood why corridors at opposing directions aren't by default
offseted both in altitude and lateral separation - there have been quite many
collision already because navigation aid reduced the positional error within a
corridor to few meters

------
paulannesley
> one thousand feet above

Are the imperial units of measurement an aviation thing, or an American thing,
or a bit of both?

~~~
errantspark
Mostly an aviation thing but descended from the fact that many early airplanes
were American/British. IIRC only China, Russia and the DPRK use metric units.

EDIT: ahahaha <3 HN commenters

~~~
sneak
Containers are also sadly measured in TEU (twenty foot equivalent units)
stemming from their American design.

Global, impossible to upgrade standards that mean we are stuck with imperial
units for a hundred years yet or more.

------
EGreg
"until the crew was able to recover the aircraft exercising raw muscle force"

Any more info on that??

~~~
tbabb
Under normal flight conditions, the aircraft's engine supplies hydraulic power
to the flight controls (flaps, ailerons, elevator), like power steering in
your car. Very necessary for big/fast aircraft, as the plane is heavy and the
force of the air resisting the movement of those control surfaces is very
high.

If the engines fail, you still need to be able to control the plane, so there
is something called a ram air turbine[1] which can be deployed out of the side
of the aircraft. It is basically just a little propeller which spins in the
breeze, which powers a pump, which supplies the hydraulic pressure to control
the plane. So if the power goes out, you can still deploy that thing and have
"power" assistance in controlling the plane.

The article says the ram air turbine did not deploy, possibly because the
g-forces were holding it in, or perhaps because the g-forces or aerodynamic
stresses were flexing the body of the plane so much that the turbine was held
in place by the bending. So the pilots did not have "power steering" on the
plane, and had to pull on the controls with "raw muscle force".

There is probably some mechanical advantage, probably both from the leverage
afforded by the mechanics of actuation, and from the aerodynamics of the wing,
that allow a single human to move the whole plane around. But it would still
be very, very hard to control the plane without power assist, especially under
such extreme conditions.

(Any pilots/aerospace engineers feel free to chime in/correct mistakes here).

[1]
[https://en.wikipedia.org/wiki/Ram_air_turbine](https://en.wikipedia.org/wiki/Ram_air_turbine)

~~~
gingerbread-man
Cessna pilot here-- I've never flown an aircraft with hydraulic controls.
(Small planes use pushrods or cables to actuate the controls. It's all muscle
power for us.)

The physics of flight produce a very useful convenience: the amount of force
needed to effect a particular degree of attitude change (e.g. a 10 degree
bank) remains the same, regardless of speed. Planes up to the size of small
jets (the Cessna Mustang, for instance) use fully manual controls with no
power assistance. The Challenger is a bit bigger, but even after the remaining
pressure in the hydraulic system completely dissipated, I doubt more than
30lbs of pressure would have been required to actuate the controls. And the
rotational inertia of the turbines should have provided at least some
assistance on top of that. (I have no idea what would have happened if an
airliner lost both engines simultaneously in a stall.)

------
nunez
I thought controllers space aircraft based on their takeoff weight for this
reason. Is this true?

A380s are HUGE, so this isn't surprising. wake turbulence is a killer

~~~
wwalser
The (current) top thread in the comments section references the reduced
vertical separation minima (RVSM):
[https://en.wikipedia.org/wiki/Reduced_vertical_separation_mi...](https://en.wikipedia.org/wiki/Reduced_vertical_separation_minima)

It appears that there is a section of air between 29,000ft and 41,000ft, where
flights are allowed to be closer than is normally allowed. Instead of 2,000ft
apart, they are allowed to fly 1,000ft apart. In order to operate continually
in this airspace, a plane must be "RVSM approved". Otherwise they have to
either request special permission or make a continuous climb through said
airspace while complying with their usual 2,000ft requirements.

The article mentions that the A380 and Challenger 604 were 1,000ft apart. So,
I would assume they were both RVSM approved. This event could call the RVSM
into question.

------
gadders
That was some flying by the Challenger pilots (to my layman's eyes at least).
I'm glad I wasn't on that flight.

------
elberto34
I wonder the private plane had to be written off...was the damage that bad?
It's like the plane broke apart ..maybe the probems were mostly internal

~~~
CPLX
When an airframe is stressed beyond its design limits it can't be put back
into service. It's conceivable that it could be put through a "C-check" type
process of disassembly and inspection, but given the age and residual value of
the plane that might not have been cost effective.

------
arrty88
this is horrifying. does anyone have a sketch of how many flips the jet
underwent before regaining control?

