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From the Det News: Preliminary report on the cause of the Hatch accident

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July 2nd, 2011 at 9:47 PM
#1
Njia
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Joined: 09/15/2009
MGoPoints: 6038
From the Det News: Preliminary report on the cause of the Hatch accident

The Detroit News tonight posted a small story on the NTSB's preliminary report into the crash that killed Austin Hatch's father and step mother. You can find it here:

The story mentions that a flight instructor from Indianapolis is speculating that the cause could have been a stall following a missed approach. From my experience, this is as good an explanation at this point as any, though the NTSB will continue to examine all of the available evidence before issuing its final report. It may yet turn out to be something other than the CFI's best guess.

For those of you who are not pilots, a "missed approach" is a procedure, documented in what are called Standard Terminal Arrival Routes, or STARs, that a pilot follows when his initial attempt to land at an airport under Instrument Flight Rules (IFR) is aborted due to weather, other traffic, etc. We'll often called these STARs "approach plates", because in printed form, they are about 5"x7" and fit a board (or "plate") that can be strapped to the leg of the pilot or mounted on the control yoke.

A stall occurs when the smooth ("laminar") flow of air begins to separate from the top of the wing, as shown below:

The angle between the "relative wind" and an imaginary line that runs from the wing's leading edge to its farthest back point is known as the "Angle of Attack". When the Critical Angle is reached, lift abruptly begins to decrease.

"Relative wind" is also important to understand, because it is the angle between the wing's imaginary front-to-back line (called the "chord") and the direction of the on-coming air relative to the wing.

So what does all of this mean for the instructor's speculated cause of the crash?

When a pilot executes a Missed Approach Procedure, she/he transitions from a descent to land to - usually - a climbing turn toward a fixed point called a "navigation fix". It is during this time, low and slow, that the pilot is vulnerable to a stall. That is because the Angle of Attack increases during a turn. Additionally, the aircraft is executing a climb, which also means a "nose-high" attitude and higher Angle of Attack. Assuming that Dr. Hatch executed the MAP successfully, later turns, possibly while descending, could have caused the same conditions.

When I learned to fly - both for my Private Pilot and, later, my Instrument rating - I, like all pilots, practiced stalls with both a clear view of the horizon and "under the hood" (the student's view of the world outside the aircraft obscured by special glasses or an adjustable hood that let me see the instrument panel, but nothing else). An experienced pilot, Dr. Hatch practiced them as well. It is essential for a pilot to recognize the onset of a stall and to correct the aircraft's pitch, roll, power and airspeed to avoid it.

All stall recoveries, though, take time at some loss of altitude. The standard by which pilots are judged during training is that not more than 50 ft. of altitude can be lost during a stall recovery. In "real world" IFR conditions and close to the ground, such as Dr. Hatch found himself last weekend, there just isn't much margin for error. He had to detect the onset (which is aided by a stall warning horn), mentally process the correct situation he was in, determine the appropriate response, and fly the recovery in a split second. Unless he had recently been practicing stalls, either on his own or with an instructor, chances are pretty good that his skills were rusty. That's not an indictment of his skills as a pilot. Most private pilots, myself included, are similarly one unfortunate chain of events from the same outcome.

I pointed out in an earlier thread that I am constantly aware that, "There, but for the grace of God, go I." Hopefully, if anything positive can come from this, it is an increasing awareness among private pilots like me that we must remain vigilant and continue to practice, hoping for the best, but fearing the worst.

"If life is the road, then Ohio is simply a place to stop for gas." -- Scott Burgess, Detroit News, 9/16/2010
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July 2nd, 2011 at 9:55 PM | Excellent insights... (Score:3 Normal)
MGoShoe
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Joined: 04/23/2009
MGoPoints: 19230

...into the challenges of an instrument landing and the complexities of the Missed Approach Procedure.

Also, not OT.

LSA '89 - MBB Natl Champions, Big 10/Rose Bowl Champions | @MGoShoe

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July 2nd, 2011 at 9:58 PM | Those interested may want (Score:3 Normal)
Raoul
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Joined: 09/29/2009
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Those interested may want to see the original article from the Fort Wayne Journal Gazette on this, rather than the Detroit News item. See: Hatch attempting instrument approach before crash

Twitter: @Raoul_000

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July 2nd, 2011 at 10:02 PM | Thank you Njia, well done (Score:1)
skunk bear
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Thank you Njia, well done explanation.

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July 2nd, 2011 at 10:42 PM | Great Post (Score:1)
BlueAggie
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This is an excellent write up, thank you.

 

(One note: The flow doesn't have to be laminar to remain attached.  In fact, after a certain point, it is advantageous for the flow over the wing to be turbulent because the drag due to a turbulent boundary layer grows more slowly than the drag due to laminar boundary layer.  This is why golf balls have dimples.  The dimples cause the laminar boundary layer to become turbulent.  Less drag means that the ball goes farther.  I'll stop being an Aero nerd now.  Sorry.)

M BSE '05, A&M PhD '11
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July 2nd, 2011 at 10:59 PM | You're right, of course (Score:2 Normal)
Njia
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Joined: 09/15/2009
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I'm an aero nerd as well (B.S. Aero. E., U-M, '90). It's just easier to describe the separation of laminar flow as an explanation of what happens at high-alpha with respect to the onset of stall.

I saw a Mythbusters (I think that's where I saw it) experiment with golf balls in a water tunnel with UV dye. It showed the characteristics of turbulent flow very well, including how laminar flow detaches sooner than turbulent flow. Thus, less drag with turbulent flow around a golf ball.

"If life is the road, then Ohio is simply a place to stop for gas." -- Scott Burgess, Detroit News, 9/16/2010
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July 2nd, 2011 at 11:07 PM | Between the way you wrote (Score:1)
BlueAggie
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Joined: 11/17/2008
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Between the way you wrote this up and your avatar, I suspected you were an Aero and not just a pilot.  I was an '05 myself (then an '11 at A&M, wooo grad school).

Speaking of your avatar, are you involved with the shuttle program?  I and a couple of friends won the ticket lottery and are heading over to the Cape this week for the launch.  I am excited to say the least.

M BSE '05, A&M PhD '11
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July 2nd, 2011 at 11:16 PM | Sadly, the avatar is not me (Score:2 Normal)
Njia
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Joined: 09/15/2009
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One of my closest friends, an Aero classmate, works at JSC in Mission Ops. He has a way cooler job than I do.

Have a great time at the liftoff! I took my family last year for STS-132 (also Atlantis). We had Causeway passes together with our friends, which put us about 3.5-4.0 miles from Pad 39A. It was amazing.

"If life is the road, then Ohio is simply a place to stop for gas." -- Scott Burgess, Detroit News, 9/16/2010
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July 3rd, 2011 at 10:58 PM | Damn (Score:1)
MichAeroGirl
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Joined: 08/27/2010
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I may be your female doppleganger.  Aero grad ('00); private pilot (somewhat lapsed); got a classmate at JSC with a way cooler job than mine; did the causeway thing for STS-133 in February.  Hope I'm not screwing up the space/time continuum or anything.

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July 3rd, 2011 at 12:06 AM | Spring graduation? I'm an (Score:2)
kdhoffma
Joined: 07/10/2008
MGoPoints: 579

Spring graduation? I'm an '05 Aero as well.

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July 3rd, 2011 at 12:18 AM | Yes, graduated in the (Score:1)
BlueAggie
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Joined: 11/17/2008
MGoPoints: 618

Yes, graduated in the Spring.  We probably had a ton of classes together, although I don't recognize your username.

My name is Tom, I was in the Airplane senior design section if that helps place me.

M BSE '05, A&M PhD '11
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July 3rd, 2011 at 2:03 AM | I don't recall a Tom, but its (Score:2)
kdhoffma
Joined: 07/10/2008
MGoPoints: 579

I don't recall a Tom, but its been a few years. I took the space systems design class... but we probably were in other classes.

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July 2nd, 2011 at 11:40 PM | So if the boundry layer is (Score:1)
skunk bear
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Joined: 03/09/2010
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So if the boundry layer is turbulent there is less drag. But if it detaches altogether there is more drag? Or is it just that you lose lift?

Obviously, I'm not an Aero nerd.

Is there a way to make the boundry layer turbulent?

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July 2nd, 2011 at 11:54 PM | Generally you make the (Score:2 Informative)
BlueAggie
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Joined: 11/17/2008
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Generally you make the boundary layer turbulent by having a non-smooth surface.  Nothing is perfectly smooth, so eventually all boundary layers become turbulent, but you can cause the transition further ahead on the body if you want to.

As I understand it, there are two effects.  First, separated flow causes a lot of drag.  Turbulent flow is less likely separate.  This is because high momentum flow is being "mixed" in from the free stream.  So, turbulent flow can be advantageous if you are trying to avoid separation.

Secondly, for a given boundary layer thickness, there is more drag from a turbulent boundary layer than a laminar boundary layer.  But, laminar boundary layers tend to grow more quickly in thickness than turbulent boundary layers.  (More quickly meaning as the air moves down the wing.)  So, in some situations the turbulent boundary layer can produce less drag than the laminar boundary layer.

M BSE '05, A&M PhD '11
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July 3rd, 2011 at 12:01 AM | So would there then be an (Score:1)
skunk bear
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So would there then be an advantage to having an irregular wing surface?

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July 3rd, 2011 at 12:18 AM | No (Score:1)
Njia
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Joined: 09/15/2009
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While laminar flow may separate from the wing surface earlier than turbulent flow, it also required to produce lift (there are some exceptions, such as with the Harrier, but none in practical aircraft of the type flown by mere mortals).

Lift and drag are inseparable. You can't have lift without drag, but you can have drag without lift. So, although turbulent flow might create less drag, that's not really the point. It doesn't create enough lift to keep an aircraft airborne.

One means of keeping the flow laminar and attached longer is to use flaps. Flaps increase both the chord length (that imaginary front-to-back line) of the wing and the Angle of Attack. So, more lift is created by the wing at a given airspeed with flaps extended. However, more drag is created, as well. Thus, flaps are used at slower speeds to both to provide more lift (e.g. during take-off and landing) and also to allow for steeper descents without gaining airspeed (i.e. due to the additional drag).

 

"If life is the road, then Ohio is simply a place to stop for gas." -- Scott Burgess, Detroit News, 9/16/2010
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July 3rd, 2011 at 1:49 PM | I think the confusion here is (Score:2)
gbdub
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I think the confusion here is that we're throwing around "laminar" and "attached" as if they are synonymous. They're not. I'll take a stab at a layman's definition (it won't be quite perfect, other aeroheads).

Basically, "attached" flow means that air is following the surface shape of your wing / golfball / whatever. Flow stays attached due to various forces, particularly pressure differentials and viscous friction between the air and the object surface. As you can imagine, keeping flow attached over a surface curving away from the air flow (such as the back half of a golf ball or a wing (particularly at high angle of attack)) requires more force than keeping it attached to a flat plate or a curve into the airflow (e.g. the front half of a golf ball). If the curve is severe enough, the force required to turn the flow overcomes the available friction forces and the flow "detaches" - it stops following the surface shape.

Detached flow creates a big "bubble" where there is essentially no air flow. This is why things don't blow out of your truck bed contantly - the cab, being squared off, forms a separated bubble behind it. This bubble has very low pressure compared to the air in front of the object, and thus "sucks" backward - this suction is pressure drag. You can feel this when you stick you hand out a car window. If your palm is perpendicular to the flow, the pressure in front of your hand will be higher than the pressure behind, and your hand will be pushed back.

Detached flow is bad for a wing because (generalizing here a bit) a wing can't produce lift very well unless flow is attached across its whole surface. When flow starts to detach, it's a stall (see OP's graphic) and the lift is reduced dramatically while drag goes up a lot, causing you to fall out of the air.

Now, turbulent versus laminar: When flow is attached, it forms a "boundary layer". This is because, due to friction, the flow infintesimally close to the surface actually "stops" on the surface. The boundary layer is the layer where the velocity increases from zero (relative to the surface) back to the velocity of the main flow some distance above the surface. You can see a similar effect by sliding a knife through peanut butter. The friction of the blade pulls along some of the peanut butter. Peanut butter very close to the blade travels almost as far as the blade, while peanut butter farther away goes a shorter distance. A boundary layer can either be laminar, meaning the flow is smooth and completely tangential to the surface (laminar means "layers"), or turbulent, with swirling eddies etc.

Lower boundary layers are thinner and produce less friction with the wing surface (and therefore lower "viscous drag", the drag component due to friction). This is good most of the time. However turbulent flows have one advantage: They are "stickier" (being higher friction and thicker) and less likely to detach from a wing surface when the surface is curving away from the flow. So they have more drag than an attached boundary layer, but much less drag than detached flow.

So either laminar or turbulent boundary layers can be attached. Flow detachment is a separate phenomenon that is less likely to occur when the boundary layer is turbulent.

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July 3rd, 2011 at 1:51 PM | Never again (Score:1)
Njia
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Will I view peanut butter the same way. 

"If life is the road, then Ohio is simply a place to stop for gas." -- Scott Burgess, Detroit News, 9/16/2010
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July 3rd, 2011 at 3:38 PM | It's not a perfect analogy, (Score:5 Funny)
gbdub
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It's not a perfect analogy, since peanut butter is a non-Newtonian fluid. Chunky peanut butter presents its own problems.

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July 2nd, 2011 at 11:02 PM | Disclosure (Score:1)
Njia
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All of this would have come out in the NTSB report anyway. Just about the worst thing, though, is that it will go down as "pilot error" if Dr. Hatch stalled the aircraft. That is almost always the net-net in an accident involving loss of control.

"If life is the road, then Ohio is simply a place to stop for gas." -- Scott Burgess, Detroit News, 9/16/2010
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July 2nd, 2011 at 11:08 PM | Your beef should really be (Score:1)
Raoul
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Your beef should really be with the Fort Wayne News Gazette and the article they published that I linked above. The writer of that article had a flight instructor take a look at the NTSB's preliminary report and speculate about the cause of the crash. (The NTSB report did not state a cause for the crash.) The AP and other news services picked up the News Gazette item, and now other newspapers, including the Detroit News, are running items based on the news services items.

But I have the same reservations you do. Couldn't the News Gazette have waited until at least after the memorial service for Austin Hatch's father and stepmother before going out and finding someone to speculate about the cause of the crash?

Twitter: @Raoul_000

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July 2nd, 2011 at 11:23 PM | I agree that this speculation (Score:2 Normal)
TheVictors97
Joined: 10/27/2008
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I agree that this speculation is premature.  I am an airline pilot with thousands upon thousands of hours of flight time and also work in our training department instructing on our airliners.  The fact that someone who is a flight instructor thinks this "may" have happened is a pretty bold statement.  Most flight instructors are recently just out of flight school and have very little experience.  They instruct to build flight time so they can fly for the airlines someday.  It's similar as to when an airliner crashes and someone with a private pilots license, who has never flown an airliner, comes on CNN and acts as their aviation "professional."

I won't speculate as to what I think happened because I think that is unfair to the NTSB professionals and the family involved, but I will say that I don't think the cause is what the "instructor" is speculating.  Is it possible?  Yes.  But at this point there could be a variety of reasons. 

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July 2nd, 2011 at 11:31 PM | The instructor struck me as (Score:3 Normal)
BlueAggie
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The instructor struck me as more than a little bit smug.  Also, it strikes me as ridiculous to speculate on the cause of the crash before they even know why they diverted to Charlevoix. 

M BSE '05, A&M PhD '11
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July 2nd, 2011 at 11:35 PM | Excellent point Aggie.  Why (Score:4 Normal)
TheVictors97
Joined: 10/27/2008
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Excellent point Aggie.  Why they were diverting may provide answers to a lot of unanswered questions.

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July 2nd, 2011 at 11:50 PM | As a pilot with lots 'o (Score:4 Normal)
Zone Left
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As a pilot with lots 'o flight time, I can assure you that pilots are smug. It's basically a universal character trait.

It's all John Navarre's fault.

 

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July 2nd, 2011 at 11:54 PM | There are old pilots (Score:3 Normal)
Njia
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And bold pilots ...

You know the rest.

"If life is the road, then Ohio is simply a place to stop for gas." -- Scott Burgess, Detroit News, 9/16/2010
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July 3rd, 2011 at 12:09 AM |   "A superior pilot uses (Score:5 Normal)
Zone Left
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"A superior pilot uses his superior judgement to avoid situations which require the use of his superior skill."

That's my favorite and one to live by.

 

It's all John Navarre's fault.

 

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July 3rd, 2011 at 5:01 AM | Too true... (Score:3 Normal)
ArchieF16
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It's poor technique to make suppositions as to what may or may not have happened until an entire investigation has been completed........

It's easy to sit in a "1-G" environment and guess as to what may or may not have happened.......but for the grace of God, go I..........

All pilots, if you've flown enough have had close call--whether it's for mechanical, weather or piloting issues.......

Regardless of the reason for the crash--it's irrelevant to Hatch now........what's important is that he gets better--whether basetball is in his future or not is too, not as important as that he has the support of his friends and family to get through this difficult time.........

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July 2nd, 2011 at 11:42 PM | I agree with everything you've written (Score:1)
Njia
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My purpose in writing up my explanation of the story wasn't to endorse the CFI's opinion. Rather, it was to describe why he would have offered this particular scenario in the first place. But, in his defense, the reporter probably asked for various possibilities, and he provided one. As I originally wrote, at this point, it's as good as any other (i.e. not much).

I think the gold standard for reporting on aviation accidents goes to two media outlets: ABC and WXYZ (Channel 7). ABC uses John Nance, who himself has "thousands upon thousands" of hours in airliners. Still, he is often asked his opinion, and if he feels at all comfortable in doing so, gives it.

Back in the '80s and early '90s, Channel 7 would call upon U-M's Professor of Aerospace Engineering, Charles Kauffman (like Harm Buning and Gerry Faeth, one of my favorites). Among his many areas of expertise was aviation accident investigation. Like Mr. Nance, he would offer an opinion if he thought the known facts warranted one.

EDIT: One funny-but-not-so-funny anecdote about Prof. Kauffman: After I'd graduated, I got a job that involved a lot of travel to Europe. He asked me whether I ever had to fly there on a DC-10. Since I was flying on American Airlines to Europe almost exclusively, and it was the early '90s, I told him I did. He said, "If you ever again find your foot about to fall on the door sill of a DC-10 again, do an about-face back up the jet way." Considering his background, I think it made my blood run cold.

"If life is the road, then Ohio is simply a place to stop for gas." -- Scott Burgess, Detroit News, 9/16/2010
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July 3rd, 2011 at 12:07 AM | I taught a class at A&M this (Score:1)
BlueAggie
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I taught a class at A&M this spring that was basically Kauffman's Intro to Propulsion course.  I'm still kicking myself for misplacing the notes that I took in his class.  If you could get past his verbal tics (instead of um or uh, he used okay and all right) he had an incredible ability to weave practical examples into his lectures.  It was humbling to realize how far I need to go to teach at that level.

I somehow managed to take 4 Kauffman courses at UM and loved every one (Propulsion, Internal Combustion Engines, Energetic Materials (his way of making Explosives! sound acceptable to the college I suspect) and Rocket Propulsion).

M BSE '05, A&M PhD '11
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July 3rd, 2011 at 12:23 AM | I took Prop II and III... (Score:1)
Njia
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With Werner Dahm. I'm still black and blue.

As we were studying for our Prop III final in the old Aero lounge (before FXB existed), one of the other profs (I think it was Gerry Faeth) walked into the copy room where Werner was running copies of the exam. Since we were only yards away from the door, we could hear the conversation (which I think they knew, of course).

Prof Faeth asked to see the exam. We heard him say, "Jesus Christ, Werner!"

I think at that point, I wept.

"If life is the road, then Ohio is simply a place to stop for gas." -- Scott Burgess, Detroit News, 9/16/2010
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July 3rd, 2011 at 12:34 AM | Dr. Faeth was a great guy.  (Score:1)
BlueAggie
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Dr. Faeth was a great guy.  He was my academic advisor until he passed in the Spring of my senior year.

I was meeting with him at the end of my junior year to pick classes for the next year.  He looks at my GPA (which was terrible) then at my GRE score (which was really good) then back at the GPA, then back at the GRE.  Finally he looks up and says, "Been having a little too much fun in college have we?"

He encouraged me to apply to grad school (and to work my butt off my senior year) and treat it like a second chance.  That remains some of the best and most influential advice I've recieved.

M BSE '05, A&M PhD '11
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July 3rd, 2011 at 1:58 AM | I liked Kauffman, always (Score:4 Normal)
kdhoffma
Joined: 07/10/2008
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I liked Kauffman, always thought a lot of the other students overlooked him because of his quirks... but what prof wasn't a bit quirky... after seeing Bernstein zip around north campus on a segway with those massive blue blocker sunglasses, I just assumed being quirky came with the PhD.

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July 2nd, 2011 at 11:21 PM | I would have to find the (Score:2)
kdhoffma
Joined: 07/10/2008
MGoPoints: 579

I would have to find the article put I believe an eyewitness from the neighborhood mentioned it sounding like the engine was cutting out prior to the crash... I'm curious if thrust is lost on a missed approach like that, might it have quickly dropped him below the "stall speed"?

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July 2nd, 2011 at 11:30 PM | Due to the reports of the (Score:1)
TheVictors97
Joined: 10/27/2008
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Due to the reports of the engine sputtering is one of the reasons why I don't think it was only related to the aircraft stalling on a missed approach.  Yes, a sputtering engine could cause an aircraft to stall as the airspeed decreases but an aircraft stalling won't cause the engine to sputter.  A sputtering engine is usually fuel related.  Again, I'm not speculating.  Just trying to provide clarity. 

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July 3rd, 2011 at 10:41 AM | posted from iPhone (Score:1)
Rabbit21
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Agree on the fuel cause as it's unlikely that a stall would cut out the engines(unless it was a negative g stall that would cut the fuel flow, but I can't come up with a reasonable way to do that in IFR conditions). If he had to divert and go missed approach he may have been in a situation in which fuel was tight. Also speculation on my part(former Air Force pilot).

Chaos is found in greatest abundance wherever order is being sought.  It always defeats order because it is better organized. 

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July 3rd, 2011 at 1:57 PM | On the other hand a (Score:2)
gbdub
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On the other hand a sputtering engine is one reason why you might stall on a missed approach - if you attempt to follwo the normal profile you might stall if you don't have enough thrust.

A stall is still likely if the engine was out - presumably the pilot would be looking for a safe place to put down or trying to gan altitude to avoid something, and if he couldn't make it, would stall out as the airspeed dropped too low.

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July 2nd, 2011 at 11:59 PM | Something doesn't add up. The (Score:4 Normal)
Zone Left
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Something doesn't add up. The Journal Gazette says the ceiling was at 200 ft and that the GPS approach mins were 500 ft. The only other approach is an NDB, which typically doesn't go even that low. Military rules would have made the manuever described there illegal, but who knows how not informed the reporter was.

It's all John Navarre's fault.

 

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July 3rd, 2011 at 12:27 AM | Very interesting thread... (Score:4 Normal)
ppToilet
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Joined: 04/18/2011
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I'm not a pilot or Aero and it's very informative to learn about this...

FWIW, a pilot friend of mine who was up in Charlevoix at the time and saw the aftermath of the accident pulled me aside the other day and said he thought it was a stall on a missed approach or a stall from a sudden veer at too low of a speed (my friend used more technical language and I'm probably not doing him justice here). He didn't believe it was engine failure because of the lack of a debris field and the location of where it happened.  Basically the plane dropped out of the sky, were his words.

Obviously the folks at NTSB are in the best position to determine the cause and I plan on waiting for their judgment.

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July 3rd, 2011 at 8:03 AM | The Journal Gazette has (Score:4 Normal)
Raoul
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The Journal Gazette has posted an updated version of its original story. The new version can be found here. A couple of paragraphs in particular were significantly changed, including the following, which highlight that the NTSB has yet to draw any conclusions:

The National Transportation Safety Board’s preliminary report, posted on the agency’s website, did not say why the plane was diverted. The preliminary report also did not give a cause of the crash.

NTSB officials declined to speak about the report Saturday. A final and more thorough report about the crash isn’t expected for several months.

In addition, the following paragraph was deleted from the updated version. I'm guessing an editor eventually decided the flight instructor's speculation had gone too far.

The fact that Hatch had to divert may have played into why he tried to turn the plane around and land. He may have been low on fuel, Wulfenspein speculated.

For those interested, the NTSB's preliminary report can be found here.

Twitter: @Raoul_000

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July 4th, 2011 at 10:49 AM | I remember (Score:1)
MGoSoftball
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Joined: 10/18/2010
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when I performed my first stall, darned near soiled myself.  But that was at 3000agl.  My first 3-rotation spin was from about 4000 agl.   Now they are actually fun to perform.

However a stall/spin on approach or missed approached is usually fatal.  Rule #1 fiy the plane.

May God give peace to the living and the deceased.  It is always painful to see another fellow pilot have an uncontrolled contact with the ground.

 

From the Red Cedar Message Board:  "God hates us."  Yes He does Lil Bro, yes he does.  Everyone hates you.

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