Today’s Illustration: Lost Lift

NTSB_Colgan_Air_Flight_3407_Crash_Animation.ogv  It Was Avoidable!

On This Day: February 12, 2009 – Fight 3407 crashes.

“On a winter night in February 2009, Colgan Air Flight 3407 crashed just outside of Buffalo, N.Y., killing all 49 passengers and crew aboard and one person on the ground. An investigation by the National Transportation Safety Board determined that the turbo-prop aircraft experienced many factors contributing to the crash, including an aerodynamic stall from which the aircraft couldn’t recover.”

Facts & Information About The Crash:

Flight # 3407 — Contential Connection flight 3407 left Newark, NJ (Liberty International) bound for Buffalo, New York (Buffalo Niagara International)

Airplane: DHC-8-400 (Colgan – Q400) – a smaller commercial Turbo-prop

Pilot: Marvin Renslow – age 47 – of Lutz, Florida

Approximately3,000 flying hours
Approximately100 flying hours flying the Q400
He was properly certified but had “failed check rides — four times!

First Officer/ Co-pilot:  Rebecca Shaw, age 24  — Maple Valley Washington

Approximately 2,200 flying hours
Approximately 800 of those hours flying the Q400
Commuted from Seattle to Newark before this flight
Indicated that she was not feeling well before the flight

The airplane was approximately three to four miles out when they began experiencing difficulties.

The de-icing system was turned on (It was a rubber boot system which expands and contracts to break up the ice on the leading edge of the wings.)

On the plane’s initial approach, the plane was going too fast, and therefore power and airspeed were reduced —–  rapidly —– to 150 mph.

The airspeed continued to decrease upon approach (which required that the wing flaps be extended 15 degrees — However, slower airspeed can also create or heighten a stall).

The warning system indicating a possible stall activated.

The “stick pusher” attempted to push the nose down to avoid a stall condition.

The pilot over-rode the “stick pusher” and pulled the nose up 19 degrees (that would only heighten the problem!).

The airplane began to roll left and right.

The passengers would have experience around 2G’s as the airplane was gyrating.

Twenty-five seconds later it crashed.

Forty-nine passengers died, along with the pilot, first officer, and two flight attendants.  Forty-one passengers were Americans

Two Flight Attendants also died.

The commercial airplane crashed into a house ( Douglas and Karen Wielinski – along with their daughter Jill), seriously injuring all three occupants, Douglas – husband and dad –  died in the hospital.

“. . . . the pilot, Captain Marvin Renslow, 47, repeatedly reacted contrary to how he should have when the plane began to stall, pulling back on the control column rather than pushing it. . . . Meanwhile, First Officer Rebecca Shaw, 24, didn’t correct the captain’s mistake.”

“Investigators pinned the cause of the crash primarily on errors by the pilots. They said Captain Marvin Renslow should have been able to recover from the stall if he had taken the correct actions, but that he did the opposite of what he should have done.

In the final seconds of the flight, two pieces of safety equipment activated – a stick shaker to alert the crew their plane was nearing a stall and a stick pusher that points a plane’s nose down so it can recover speed, investigators said. The correct response to both situations would have been to push forward on the control column to increase speed, they said.

But Renslow pulled back on the stick shaker, investigators said. When the plane stalled and the pusher activated, and then reactivated two more times, Renslow again pulled back all three times.

“It wasn’t a split-second thing,” NTSB safety investigator Roger Cox said. “I think there was time to evaluate the situation and intitiate a recovery, but I can’t give you a number of seconds.”

Seventy percent of pilots who had experienced the stick-pusher activation in training responded by pulling back instead of pushing forward – the opposite of the correct response – even though they knew ahead of time to expect a stall, investigators said.

The first officer, Rebecca Shaw, 24, should have stepped in to push the plane’s nose down herself when Renslow responded improperly, but she may not have because she was a relatively inexperienced pilot, investigators said.

Peter Grant – professor of Aerospace Studies and expert on flight simulation – University of Toronto:

“In most cases, a lot of things go wrong before a plane actually crashes. . . . . Part of the challenge is that pilots are often trained on simulations that take an aircraft right up to the point of aerodynamic stall but not past it.”

“Commercial aircraft have various safeguards in place to prevent stall, such as alarms, a “shaker” mechanism or built-in “pusher” system that prompts the pilot to direct the nose down to lower the angle of attack. By lowering the aircraft’s nose, it re-establishes lift, making the airplane easier to control and giving pilots a chance to correct even a severe roll. Some large jets are also equipped with “envelope protection” measures designed to keep the plane flying within safe parameters.”

 

Facts & Information About A “Stall”:

Losing Lift — (A “How It Works” Illustration)

While teaching at a Christian College in Minnesota, I took flight lessons from a Northwest Orient Captain who offered lessons to the professors at the college, like me, at a reduced cost.  Learning a little about aerodynamics and/or flying an airplane can be of great illustrative value for use in a speech or a message.

Here is some information about “lift” and/or “stalling” an airplane.

Typically, the first steps in learning how to fly involve being taught basic laws of aerodynamics.  Class instruction covers such topics as “airfoils,” “angle of attack,” “wing structure,” “yaw,” “pitch,” “altitude,” “attitude,” and “lift,” “drag,” and “thrust.”

One of the most misunderstood concepts of flight is what is called “stalling,” or the loss of “lift.”

A stall is a condition in aerodynamics and aviation wherein the angle of attack increases beyond a certain point such that lift begins to decrease. The angle at which this occurs is called the critical angle of attack.”

When we think of “stalling” we often relate the concept to driving a car — the car engine stops running.  Perhaps, some remember the days of using a clutch and manually changing or shifting gears, one let the clutch out too fast, and the car “stalled.”

However, that is not how it works with an airplane.  The stall of a car engine has nothing to do with the “stalling” of an airplane.  The airplane’s engine is fully operational and working.  In fact, a pilot typically needs to increase the speed of the airplane and power its engine(s).

There are several ways to think about “losing lift” or “stalling.”

#1)  The air is no longer flowing across the top surface of the wing properly, and therefore the wing (or airfoil) is not doing what it is supposed to do, pull the rest of the airplane upward.

#2) The air is not presenting its self from front to back, from the leading edge of the wing to the back of the wing.  But the air is moving from another direction faster than front to back.  For instance, the air is moving faster from the bottom of the wing because the airplane is dropping in altitude faster than the airplane is moving forward.

#3) Think of “stalling” an airplane as what happens when a boat sail is not catching the wind, when the wind is not filling the sail and is limp.  An airplane wing is just a sail which is horizontally instead of vertically situated.   The angel of the air flowing across the wing or sail determines whether the wing or sail will perform its intended function.

#4) Turbulence:  The reason an airplane experiences “turbulence” is because the airflow over the surface of the wings has been upset.  The airflow over the surface of the wings is being upset by other and faster burst of air coming from another direction, other than from the front to the back of the wings.

#5) Lift-off:  The reason a plane must travel down a runway, to a speed of around 150 mph is before the pilot can pull back on the “wheel” (yoke) is because the air needs to be moving across the wings fast enough.  If the pilot tries to lift the plane upward too soon — nose-high —  which then changes the airflow, the needed lift will be lost, and the airplane will stall.

“Stalling” involves the loss of lift, or the loss of proper airflow across the surface of the wing.*  A “stall” happens when the air is no longer traveling across the wings at a proper angle (i.e. “angle of attack”). When an airplane “stalls” gravity takes over and it begins to drop like a stone in the air.

“Pilots practice stalls and recovery as part of their training, and they must perform a stall and recovery to earn a private or commercial certificate. However, routine flight reviews often do not involve stalls, and as a result, pilots may forget how to recognize the indications that an airplane is going into a stall. Practicing stalls and recovery at slow speeds—and at sufficient altitude to recover, of course—helps pilots recognize the early signs of a stall condition so that they can make the proper corrections.”

When the air is no longer traveling across the wing surfaces from front to back, the wings lose lift.  It is the movement of the air across the curved upper surface of the wings which suck the wings upward.  When that “suction” is lost the result is that lift is lost.

Stalling by a loss of lift (assuming no structural damage or change) is caused by four general situations . . . . .

#1) Moving too slowly through the air — Which is why an airplane has to reach a certain speed down the runway before pulling back on the controls (yoke) and lifting off the runway.  At higher altitudes, the airplane needs to fly even faster because the air is thinner.  You could stall an airplane which was flying at 350 knots but was at 36,000 feet.  A better speed is about 500 knots.

#2) Pulling or pointing the nose of the airplane upward too soon or fast while flying —  If a pilot were to pull back on the “yoke” and try to gain altitude too fast, the flow of the air across the wings would be disrupted, and the airplane would lose lift and drop in altitude.

#3) Dropping in altitude too fast, typically in landing — If a pilot were to drop in altitude too fast in the air as he sought to land, the air movement across the wings would be disrupted, and the airplane would lose lift.

#4)  Change of Wing Dynamics — If there is significant ice or snow buildup on the leading edge of the wings so that the required flow of air over the wings is changed, a stall can occur.

 

Key Illustrative Thoughts:

• It was avoidable
• Only “If”
• nose-down, not nose up
• lost lift
• people crash the same way – nose up
• moving too slow
• ice on the wings
• he had time to recover
• the co-pilot failed to warn and correct
• other people also get hurt
• It started out as a normal day
• Who knew?
• a few miles out from landing
• did the opposite of what should have been done
• the warning system worked
• ignoring the warning system
• over-riding the warning system
• crash & burn

 



Other Information & Links:

Bernoulli’s Law Simply Stated:

Benoulin’s Law: Benoulin’s Law is what explains “lift”

“Bernoulli’s principle can be used to calculate the lift force on an airfoil . . . For example, if the air flowing past the top surface of an aircraft wing is moving faster than the air flowing past the bottom surface, then Bernoulli’s principle implies that the pressure on the surfaces of the wing will be lower above than below. This pressure difference results in an upwards lifting force.”

In essence, an airplane is being sucked upward by its wings, by the aerodynamic force called “lift.

A pilot has to keep the airflow moving across the front to back edges of the wing’s surface.

The flow of the air must move properly across the wing surface to create lift, to cause the wing to pull the weight of the airplane upward.

If a pilot attempts to point the airplane up too fast, the air flow changes and lift is lost.

If the airplane is moving too slow as it lands, it loses lift and lands hard!

When the airplane is building up speed down the runway, more and more lift is being created so that the nose of the airplane can be directed upward while still having sufficient and needed lift.

Buffalo Crash Links:

https://en.wikipedia.org/wiki/Colgan_Air_Flight_3407

https://phys.org/news/2018-06-plane-crashresearch-aerodynamic-stalls.html

https://www.npr.org/sections/thetwo-way/2010/02/colganbuffalo_plane_crash_erro.html

https://airfactsjournal.com/2014/03/double-tragedy-colgan-air-flight-3407/

 

♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦

*The airplane’s “wings” or airfoils are multiple since the tail surfaces are also airfoils by design.

Typically, an airplane is safe within 15-20 degrees of level or a vertical position.  In that range, moving forward, the air will flow over the angle properly and maintain lift.

Military jets can exceed that angle because they are powered by engines which can rocket them upward.  When passenger jets are tested, they can also exceed that angel because they are not carrying the weight of passengers and luggage.

Sometimes, landing an airplane is called “a controlled stall” because as the pilot lands, there is a drop in airspeed and therefore the flow of air from going across the surface of the wings of the airplane is changed and lessened.  Have you wondered why a pilot suddenly increases the airspeed of the airplane as he/she is landing?  Why are we going faster when we are landing?

If you lack enough altitude when you go into a stall condition, your will not have enough time and space to recover lift.  That happens because when you lose lift, the airplane needs to be maneuvered in such a way as to regain the flow of air across the wings.  To do that, it usually takes pointing the plane at such an angle that the air is properly cutting across the wings — usually in a sort of nose dive direction — pointing the nose down and/or adding power — and then pulling out of the dive as lift is regained.

Pointing the nose down towards the ground and this makes the airplane go faster AND gets the air moving over the wings again, from front to back, creating enough lift to allow the plane to fly again.

In the almost 50 years that I’ve been flying, I have never unintentionally stalled an airplane. I came close — once. It was at Morristown (New Jersey) Municipal Airport, where I was training in the Cessna 150. I was in the pattern doing touch-and-goes. As I lifted off after a landing, the tower called and said that the pilot of an airplane on downwind couldn’t tell if his gear was down or not. The controller asked if I could make a climbing turn and come up under and behind the airplane to see if the gear appeared down. Could I! So I did. But as I was banking and climbing, I was fixated on the gear of the other airplane. Suddenly, luckily, I became aware of the turbulence that foreshadows a stall. With the practice Jack had insisted on, I quickly lowered the nose, reduced the angle of attack (AOA) and got the wing happy again. With everything under control, I reported the gear looked down. But what was more important, I had learned how easily a distraction can get you into trouble.” — Why all pilots should keep practicing slow flight and stalls. — By Tom Benenson

Practicing A Stall & Recovery:

Make sure you have plenty of altitude to practice — that you are at least 1500 to 3000 feet above the ground if it a small aircraft.

Make sure there are no other airplanes in your area so that you can maneuver as needed without endangering another aircraft.

Trust your instruments as you keep you seek to keep your wings level to the horizon on the indicator while in a stall condition.

 

https://www.flyingmag.com/technique/proficiency/airwork-dont-quit-stalling

https://www.decodedscience.org/airplane-wings-how-lift-is-created/6595

http://howthingsfly.si.edu/aerodynamics/factors-affecting-lift

https://en.wikipedia.org/wiki/Stall_(fluid_mechanics)

https://www.thebalancecareers.com/what-is-an-aircraft-stall-282603

http://www.aviationsafetymagazine.com/issues/36_10/features/Aircraft-Stalling-3-Basic-Kinds_11245-1.html

https://en.wikipedia.org/wiki/Bernoulli%27s_principle

https://www.businessinsider.com/the-airasia-crash-was-most-likely-caused-by-an-aircraft-stall-2015-1

http://www.pilotfriend.com/training/flight_training/fxd_wing/stalls.htm

https://www.usnews.com/news/best-states/wyoming/articles/2018-05-17/ntsb-determines-engine-stall-cause-of-2016-plane-crash

 

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