Sport Today

http://www.washingtonpost.com/wp-dyn/articles/A27697-2005Jan21.html

Jet's Presence Noted in Copter Crash
Survivor's Account Raises Wake Turbulence Issue, Report Says

By Michelle Boorstein
Washington Post Staff Writer
Saturday, January 22, 2005; Page B01

A preliminary report on the Jan. 10 medevac helicopter crash near the
Woodrow Wilson Bridge says that a 70-passenger jet passed the area less
than two minutes before the helicopter went down and notes that the
only survivor, a flight nurse, wondered whether it might have left a
wake of dangerous air turbulence.

The nurse, Jonathan Godfrey, 36, of Chesapeake Beach told investigators
for the National Transportation Safety Board soon after the crash that
"we must have hit something," leading to initial speculation that the
helicopter hit one of the construction cranes being used to build a new
bridge.

But the transportation board's report says a traffic surveillance video
shows an aircraft flying over the bridge about the time of the crash
and descending after it had passed above and beyond the cranes being
used to build a new bridge.

The nurse said he called the pilot's attention to the lights on the
cranes, according to the report, "and the pilot acknowledged him." The
report said Godfrey "remembered being over the outer loop of the span
of the bridge, and then being submerged in the water with his seatbelt
on, and his helmet off.

"He stated, 'I don't remember striking something, but my initial
reaction was that we must have hit something.' "

The report does not conclude whether the LifeEvac helicopter -- which
the report described as properly maintained -- encountered wake
turbulence, an invisible whirlwind that comes off a plane's wings, then
sinks and dissipates. The crash killed the other two crew members,
pilot Joseph E. Schaefer III, 56, of Sterling and Nichole Kielar, 29,
of Henrico County.

Wake turbulences can be very powerful and stretch for miles, so much so
that planes are required to travel at certain distances from one
another to avoid them. An Airbus A30-600 that crashed into a Queens,
N.Y., neighborhood in 2001 encountered wake turbulence seconds before
it went down. Airbus said the pilot's use of the rudder after the wake
turbulence caused the tail of the aircraft to come off.

Phone calls to the transportation safety board were not immediately
returned last night.

One air-safety expert said the report did not point to obvious wake
turbulence from the jet, which passed over the bridge 105 seconds
before the helicopter did and which was 900 feet directly overhead.

"Without further study, I would not consider that to be an obvious
danger," said Peter Goelz, former managing director of the
transportation board.

But Todd Curtis, a former Boeing safety official who runs a Web site
about air safety, noted that wake turbulence is more likely to cause
problems when two aircraft are of different sizes. He said it is also
significant that wake turbulence sinks.

"The risk factors are lining up. The question is, how much wake
turbulence was generated by the jet?" he said. "These are the kinds of
conditions that are associated with wake turbulence."

Airflow along a swept wing is not purely forward to back.  There is
also a spanwise (from the wing root toward the wingtip) component of
airflow.  The air releases from near the tip of the wing in what would
look more like a tornado than what you might imagine.  In fact if you
have ever been sitting in a window seat on a aircraft landing or
takeing off in a humid environment you might have noticed the vortice
is "fleshed" out by the combination of cool air and humidity.  That
"tornado" or votice has the potential to be very damaging depending on
the configuration of the aircraft creating it.  The worst situation is
a heavy aircraft, cleanly configured (no landing gear, flaps or slats)
flying very slowly, ie.  a prelanding scenario or post takeoff
scenario.  At altitude we do sometimes encounter wake vortices but it
is not nearly as *** as when aircraft are preparing for landing.
Oddly enough once the aircraft initiates lowering the flaps and landing
gear the vortices are minimized.

Not to worry.  Generally a transport category aircraft (airliner) has
enough mass and momentum to withstand the worst of wake vortices
created by like sized aircraft.  However as evidenced by the crash of
the American Airlines 587 (referenced above) near JFK back in November
2001 the vortices can be severe enough to contribute to a crash even if
they are not the actual causal factor.  It is widely accepted that the
Second Officer (co-pilot) responded too aggressively to the wake
turbulence that the flight encountered and aggravated the situation by
full control inputs causing the crash.

http://SportToday.org/

Now the pisser about wake turbulence is that in my experience it is a
very selective event.  The absolute worst wake turbulence I ever
experienced was while flying a medium sized twin engine business
aircraft into Sarasota Fl on a very calm morning.  The Aircraft just
ahead of me was similarly sized and generally of a weight not
considered to be a hazard where wake turbulence is concerned.  I  had
ensured adequate spacing between myself and the aforementioned aircraft
(probably about 90 to 100 seconds).  But I'll be damned if their wake
turbulence didn't roll me past 90 degress in close proximity to the
ground.  It was a very... ummmm... exciting moment of my life.  And
that is what the Ambulance Helo crew had to deal with.  They had
probably flown in close proximity to the approach path to Reagan Intl.
on a number of occasions without any previous negative effects.  In
fact there is a route that all aircraft must follow when flying the
Potomac so as not to violate the protected airspace near the White
House and associated DC landmarks which would put the one aircraft
almost directly above the other.  This was probably a case of being in
the wrong place at the wrong instant.
A real shame.  My prayers go out to the families.
Tom

Pete

1. In light aircraft the rudder pedals are connected to the rudder with
control cables, and there is direct correlation between rudder pedal travel
and the amount of deflection of the rudder. On large aircraft, especially
fly-by-wire aircraft such as the Airbus, the flight control system changes
the amount of pedal travel and pedal effort with the airspeed. In the
systems I'm familiar with, the flight control system limits rudder
deflection and rate of change of deflection as the airspeed increases. This
is done to prevent overloading of the vertical stabilizer, as loading
increases with airspeed. Pilots have the expectation that the limiting
system will prevent overloading the rudder, and convey this limiting through
the feel of the controls (pedal travel and resistance). It seems in the case
of Airbus this is not true. At the speed of the incident, rather low pedal
effort and deflection can effect large and rapid rudder deflections which
can cause overload.

2. FAA certification of transport aircraft only requires that an airframe
can withstand a single maximum rudder deflection in one direction, followed
by a return to neutral, and Airbus met this standard. However, Airbus knew
that rapid oscillations between full left and full right rudder could cause
structural failure. (Note that in normal air transport flying, pilots have
no reason to rapidly go from full left to full right rudder.)

3. Neither Airbus documentation, nor American Airlines training emphasized 1
and 2  above.

4. The flight data recorder (FDR) on the aircraft recorded filtered data.
That is, it recorded flight data as presented on the pilots instruments,
which has been processed, rather than raw data. Remember, this is a
fly-by-wire system: if the sensor inputs are wrong, or the data is processed
incorrectly, the rudder response could have been greater than the feedback
the system gave the pilot. Without the raw data, the investigators can't be
sure what happened.

5. There have been other accidents in which Airbus aircraft have crashed
where it appears that the flight control system did not react the way the
pilots expected. (Although these incidents did not involve rudder control,
but, I believe, the pitch channel). I believe Airbus had the first
fly-by-wire system for a conventional aircraft (Concorde had the first
fly-by-wire system, but it was a delta-wing supersonic aircraft, and that's
a whole nother story). Although the system seems to have mapped system
response to pilot input well in normal flight conditions, its behavior in
some extreme situations may appear anomalous to pilots.

As a person who has repaired many automatic flight control system failures,
I am not so inclined to rule out system failure or design deficiency, and
look instead for pilot error. As an Airbus passenger I can recall a couple
of flights in which the aircraft was doing low-amplitude Dutch rolls,
indicated to me that the yaw damper was not performing well, and needed
repair or recalibration. (I've never had this experience on a Boeing
aircraft, even though most of my flying has been on Boeing planes.) That's
why this event provoked my interest.

Although the sound-bite summation of the FAA report is "pilot error", a
deeper reading reveals major design/system contributions to the event, as
well as some uncertainty due to the way the flight data was recorded. First
Officer Sten Molin is not here to explain or defend his actions, so it is
all to easy to point at him as the cause of the accident. In the interest of
flight safety, and respect for his survivors, we have look deeper than that.

I can't tell if you feel that I was blaming F/O Molin for the crash.  I
was not.  I worked for the aforementioned airline for 2 years after
they purchased my prior employer... TWA.  The corporate and safety
culture were very different there than where I came from.  It is my
opinion that your comments are very valid and are reflected in the NTSB
findings.  I agree that S. Molin probably received too much of the
blame.

In light of the crash of the Air Evac helo my point was that wake
turbulence is not as much a danger to large transport category aircraft
(airliners), which most people here would be familiar with.  Didn't
want anyone to get skittish about flying into Kahalui ;-)
FWIW
Tom

jeff feehan

But since we are on the topic...

I would assume that nearly once a week (probably underestimating) an
A-300 somewhere in the world encounters a significant wake turbulence
event. And they have all flown away also except for AA 587.  What is
the difference?

Here is a link to another near miss.
http://www.iasa.com.au/folders/Safety_Issues/others/perilousparallel....
Notice the airline?

As I said in my opinion AA was teaching some concepts that were counter
the norm in the airline biz regarding wake turbulence.  Concepts that
were very different than what I was taught at my previous airline and
what I was taught from the beginning of my civilian flight training
back in the day.  This could be a coincidence or it could be an
indication that someone was getting some bad info on controlling
airplanes.

Another story relating to the AA training.
http://www.slackdavis.com/news_article.php/news_id/argval/960/argname...

And a more indepth look at the data with some great counter points made
regarding who was at fault.
http://www.iasa.com.au/folders/Safety_Issues/RiskManagement/crowinsta...

I think Bob Jacobson's summation above covered the situation well.
Without raw data from the FDR there is no way of telling whether Molin
went stop to stop on purpose or by accident.  And there is certainly no
way of telling what it was that made him touch the rudder in the first
place.  However the data that is available seems to indicate that the
Flight Control System was functioning properly in flight.

An article in support of Molin.
http://www.latimes.com/news/opinion/commentary/la-oe-garrison11jan11,...

Peter Garrison is a respected aviation columnist.  He wrote a very nice
article about Sten Molin.  I think that what he left out however is why
would the F/O use the rudder pedals to arrest a roll event?  The main
point of Garrison's article and Bob Jacobson's summary is valid.  It
shouldn't matter what Molin did with the controls.  The damned airplane
is supposed to be engineered in a way that prevents it from falling
apart at those speeds even if full control input is used.

I started flying at 17.  Put myself through a junior college program
and followed the career path of a civilian commercial pilot.  Line boy,
Flight Instructor, Charter Pilot, Corporate Pilot, Commuter Pilot,
Airline Pilot, Furloughed Pilot, Pilot for the Federal Gov't.  That is
a career of 17 years and counting.  And God willing I will die an
ornery old windsurfing pilot.  But, in all my years of civilian flying
I have never heard of using the rudder pedal to arrest a significant
roll event outside of military ops, have you?  I have flown with some
old salts that used only rudder on their F-4's because using the
aileron at high speed on the early models initiated a departure from
controlled flight.  But in the passenger biz we usually just use the
aileron and a touch of rudder if necessary.

When it comes to Sten Molin I think he should have known better.  I
DON'T think the accident was his fault.  He was taught how to use the
rudder pedal by the operator of the aircraft.  He was taught that using
the rudder at those speeds was perfectly safe, no matter the amount of
input.

The training was wrong at the very least.

The question was "Why was it Sten Molin's fault?"  When it comes to the
official finger pointing you have to remember that when you get paid
the big bucks (this is a sarcastic comment that only another airline
pilot could appreciate) you take the blame when the airplane ends up
somewhere it isn't supposed to be.  It is unfortunate, but it is the
norm in our industry.

And finally if anyone thinks that I am boasting that I wouldn't have
crashed that airplane if I were in Molin's shoes then you are
absolutely wrong.  I live by the motto "There but for the grace of God
go I."

I appreciate the opportunity to discuss the event and consider the
opinions and counterpoints.

Take it easy
Tom

That was 2001.  I have been furloughed and out of the loop since 2003.
I have no idea what the culture is like over there today.  I tried to
reinforce that thought by using past tense.  Sorry that I wasn't more
clear.

I am sure things are very safe as a result of increased Federal
oversight in the wake of the industry's financial problems.  Anytime
airlines have financial problems the FAA jumps all over themselves to
assure that training, maintenance and other matters aren't allowed to
suffer as a result of tight finances.  Trust me on this.  I worked for
TWA for 6 years and we were always seemingly one step from financial
ruin.  I have never had the FAA on my jumpseat so many times as when
the winter cash crunch would hit the company.

AA has great crews and solid procedures.  How about the crew and
passengers that averted the Richard Reid disaster?  Heads up thinking
and excellent use of resources.  

AA is a good airline.

Tom

In general the airlines have gotten so bad that I won't even bother to
fly unless it's impossible (time wise) to get there by car.  Part of it
has to do with all the nonsense security measures that are obviously
only there to make you feel better about flying, and have nothing to do
with actual security.

As a bonus, if you drive, it's far easier to bring toys such as
Windsurfing gear. :-)

Sorry, I am feeling rather chatty today.  Southern Arizona needs more
water.

Well I agree with your feelings about airlines in general.  They are
very poorly run businesses from a customer service point of view.  And
getting worse.  Let me tell you from the "Crew" point of view it was
tremendously frustrating seeing your passengers "screwed over".
Maddening.  And the power has been taken away from the crew to do
anything about it.   It seems that Southwest and Jetblue may be
different but I haven't had the opportunity to ride on either airline.

I used to fly with the guys and girls who really had POWER as flight
crew members back in the 60's and 70's.  Even the early 80's.  The
stories they would tell about making the gate agents do things right or
not leaving the gate.  Demanding that the aircraft were cleaned
properly or parking the plane until it was done correctly...  but now
Management has pretty much eliminated the crewmembers ability to make
right a situation that is obviously wrong.  And it really bothered most
people that I worked with... if that is of any consolation.

I am not going to comment on AA other than they are about par for the
course in my experiences, and that isn't a compliment.

I will say however that most airlines have just become the equivalent
to Greyhound service for the leisure traveller.  Unfortunately Business
travellers are stuck with the fallout.  I just bought tickets from
Phoenix to Boston for a family of four for this summer for
$238.00/ticket round trip.  How the hell is that possible?  I couldn't
drive it for that if all you counted were the gas stops not to mention
wear and tear on the car and hotel stops.  Am I going to complain about
no meal and dirty airplanes?  Not for $238.00 I'm not.  Hell, I would
ride in cargo for that price.  And my attitude as a consumer is part of
the problem.

So between the airline employees the passengers and management we have
pretty much done it to ourselves in my opinion.  The airlines are
giving away the product on domestic just to kill off the weak sister
right now.  They need to regain some control over their pricing.  And
until capacity is reduced that isn't going to happen.  Even when
capacity is reduced I doubt there will be any return to the perks that
used to be available... like hot towels and lukewarm meals.

Here's hoping to a return of wind soon!
Tom

I am happy that I am out of the business.  But I did enjoy those Maui
layovers.

I do believe your original post gave the impression that the FO was
responsible for the crash.  From your subsequent posts I can see that you
have a more nuanced and informed view of the situation. I appreciate your
considered and informed viewpoint. Your link to the International Air
Traffic Safety Association is very informative and basically is in sync with
my earlier post.

I believe that after a similar incident in 1997 (which did not result in
failure, but led Airbus to conclude that rapid rudder reversals within the
design limits could lead to structural failure) , Airbus did not did not
make sufficient efforts to make the carriers aware of the danger in sudden
rudder reversals, and to work with the carriers to ensure that training
programs imparted that information to pilots. Seems to me that the Airbus
communications were close to being in the CYA category.

I also believe that Airbus should change the flight control system to reduce
rudder control sensitivity at airspeed. It makes no sense to me that rudder
control sensitivity should increase with airspeed. (I used to own a Peugeot
that had speed-sensitive variable-ratio power steering. Maybe the Airbus
guys should talk with the Peugeot guys. Wouldn't even require a translator.)

I appreciate the fact that pilots believe that since they have command, they
will be blamed if something goes wrong. This can be a good thing if it keeps
pilots sharp. (Although the fact that the pilots are always the first to
arrive at the scene of a crash seems motivation enough to me.) However, as a
passenger, I want to be assured that the manufacturer, the carrier and the
pilot are all doing their best and working in together for safety.