3 posts tagged “accident”
Part 1 explained what happened; Part 2 will try to explain why it happened.
It took me a while to figure this out and still, I can't guarantee that this is 100% accurate. Nevertheless I'm pretty sure this is why the car ultimately lost control and rolled over. It bugs me because I'm a fairly conservative poor-weather driver and the accident occurred on a straightaway - it's something I would've never imagined could happen in an AWD vehicle but I think the Honda Pilot's AWD was part of the problem...
Initial conditions:
- two-lane state highway
- straight stretch of road
- 35 degrees and snowing
- 2" unplowed snow created a "two-track" effect
- driving 40-45 mph
- going east with a 20-30 mph NE wind (left quartering headwind)
- nobody in front or behind in our lane
- one car in the oncoming lane
1. Oncoming car passes, causing an air draft that combined with the already strong crosswind, nudges our car toward the shoulder.
2. I steer slightly to the left and take my foot off the pedal, trying to re-center the car in our lane.
3. The front wheels begin to "plow" as our car enters the snowy parts of the "two track".
4. Our car starts to weather-vane into the quartering headwind; i.e. the back end is moving closer to the shoulder than the front end.
5. Sensitive to a possible oversteer condition, I return the steering wheel to neutral and lightly step on the gas. I intended to "drive" back into the snow-less two-track and then straighten out the car there, where there was more traction.
6. The back end begins to fishtail toward the shoulder, catching me by surprise. It was only later that I figured this out: The Honda Pilot AWD system operates in FWD (front wheel drive) but will direct power to the rear wheels when the front wheels start slipping. When I straightened the wheel and applied some power, the fronts were already plowing so power was directed to the rears. However, due to the weather-vane effect there was swing momentum on the back end and with the rear tires already in snow they must've slipped, causing a fishtail.
7. Still I wasn't too concerned; the front wheels hit the dry two-track and regained traction, pulling us back into the center of the lane.
8. I steered a bit to the right, intending to straighten out the car and I thought that this minor event was all but over.
9. Here's where I made my mistake: I kept my foot on the accelerator, assuming that the front wheels on dry pavement would pull the car into alignment. I didn't realize that the rear wheels had been spinning - I'm not sure when the Pilot's AWD reverts back to FWD, but since it doesn't have traction control or stability control, it's not as "intelligent" as a more modern system. The rear wheels were probably still spinning as I steered right and the front wheels caught dry pavement, allowing the rear end to fishtail strongly to the left.
10. The back end is now across the center line to the left; I assumed that I hadn't centered the steering wheel - turning it too far to the right in step 8, so I turned it to the left thinking that I was centering the wheels. In hindsight I had centered it in step 8, so when I turned it left here I inadvertently set us up for an oversteer.
11. With the car somewhere around 45 degrees sideways, turning the front wheels pointed them along the direction of the road. Since they were still on pavement and still under power, they tried to pull the back end back toward center.
12. Mistake #2: I took my foot off the gas, but too late. The back end had already started swinging back to the right by the time I removed power from the wheels. Coupled with the strong crosswind, the back end swung severely to the right.
13. The back end swings almost all the way around, not quite 180 degrees - we were coasting backwards in our lane but with the back end a bit closer to the shoulder than the front.
14. The wind continues to push, causing the car to drift onto, and off of, the shoulder.
15. This wouldn't be so bad in most places, but we happened to go off the road at a 12-foot embankment with a 45-degree slope. I was hoping we'd just coast along the slope at an oblique angle and come to a nice stop when it flattened out...
16. Alas, the back left corner of the car dug into the tall grass and soft dirt, stopping our rearward movement rather abruptly.
17. We still had some kinetic energy that had to dissipate somewhere, so the car began to roll. It wasn't perfectly sideways - when the rear left corner dug in, the car pivoted a bit around that corner and the resulting roll was somewhat back-left-bumper to front-right-windshield as we rolled down the slope, hence the damage on the passenger side of the front roof.
None of this would've happened if I had better understood how the AWD would react, and it's a good case for why an AWD without traction control can be confusing. Amanda's Subaru Forester has full-time AWD where all four wheels are getting 25% of the engine's power under normal conditions so when one wheel begins to slip, it's more predictable and controllable.
Yet most AWD systems are FWD in normal conditions, meaning that when wheels slip it's hard to conceptualize what will happen next. These systems are mostly meant for accelerating from a stop in slippery conditions, not maintaining control, which is why most of them come with traction control these days. My 2003 Honda Pilot didn't have it, but I believe all Pilots since 2006 have the more advanced AWD systems.
Last Sunday Amanda and I set out for my Grandma's to eat our third Thanksgiving dinner within four days. However the real turkey turned out to be me! Grandma lives about 20 miles away but we only made it one mile...
Half an hour before we left it began to snow but the temperature was still holding at 35 degrees. Heading out of the driveway I stepped on the brakes to do a slipperiness test and yep, it was slick. Turning onto the two-lane state highway I took it slow, going 10-15 mph below the 55 mph speed limit on the unplowed road.
Still too fast, apparently. Barely one mile departed on our trip on a arrow-straight stretch of road, our car (a 2003 Honda Pilot) began to fishtail. Despite my attempts to hold the car steady in hopes of riding out the oscillations, the amplitude of each swing of the rear end progressively increased.
Right, left, right, then a big 180-degree swing to the left had us going down the road backwards! Looking out my driver's side window I saw us approach the edge of the road where a 45-degree, 12-foot downward slope awaited. I called out to Amanda "Hang on, we're gonna roll!" but secretly I hoped that the car, still riding backwards, would merely drive itself diagonally across the embankment.
Strangely - but not surprisingly if you know me - I felt extremely calm during the event. In high-pressure, high-action situations for whatever reason I don't panic. I simply observe and react, as if the world has just slowed down a few ticks and my logical reasoning deploys itself at a lightning-fast subconscious level.
My warning to Amanda was accurate. The left rear dug into the weeds and soft ground and the car began its roll onto the driver's side. Amanda screamed just like she did on our first roller coaster ride together years ago!
My eyes focused out the windshield I watched the sky roll around and felt my head clunk the B-pillar but instantly I knew it was a harmless knock.
The impact was harder when the roof hit the ground but I felt nothing, not even the seatbelt. Later I would realize that the minor bruises on my knees probably happened at this point. I noticed that the windshield shattered but remained intact and in place.
The roll onto the passenger's side was quite mild, and then slowly but somewhat jarringly the car plunked back onto its wheels and the accident was over.
I felt 100% OK and after double-checking for a split-second I concluded that I was unhurt. I looked over to Amanda and asked if she was OK and she muttered "Yeah, I guess" but didn't seem convinced. Then she says "I have blood coming from somewhere!" and I see blood on her right hand. Quickly I check her head and face but seeing nothing, I figure it was a cut finger from the shattered passenger's window. Luckily that's all it was.
Amanda had been on the phone with her mom at the time of the accident so I asked her if she were still connected. Amanda retrieves her phone from the floor and says "No, it hung up" so I urged her "You better call them back!" Even though we called back within a minute or two, her parents later would say that it felt like our callback took days!
For good reason - here's what Amanda's mom heard on her end of the phone:
Amanda: "Hold on a sec, there's a problem on the road..."
[pause]
Andrew: [in the background] "Hang on, we're gonna roll!"
Amanda: [SCREAM]
[call disconnects]
Thanks to our networked world Amanda's mom probably suffered the worst injury despite being over 100 miles away!
I shut off the engine and we got out - amazingly our doors opened just fine. Already there were four good samaritans checking on us! Two drivers and two neighbors, including the one who's field we ended up in. I assure them we're OK and the drivers began to leave.
Then a woman comes running up to me on the verge of hysteria and doing all she can to not break down sobbing. She explains that she had just passed us in the oncoming direction and then looked into the rearview mirror to see our car flipping over. She was certain we were dead - I guess the roll looked worse than it felt!
Although Amanda did suffer some injuries - mainly a mild concussion, but also some rather impressive bruises from the seatbelt and various other locations. My worst injury was a moderately strained rib cage but Amanda got the brunt of the impact - just the the photos below and it's easy to see why.
The homeowners were super nice and let us sit in their house while we waited and they even gave Amanda a bandaid for her finger. After being put on hold several times by Allstate's roadside assistance (yeah, thanks for the timely help... not) they finally sent out a tow truck. The guy was able to drive my car right up to the wrecker! I was surprised that it could drive at all, especially after getting a closer look at the windshield and seeing the extent of the damage.
My parents, brother and his wife arrived - they, too, were on their way to Grandma's and diverted to us when I called about the crash. They drove Amanda back home while I waited... and waited...
The police took forever to arrive. Not initially - within five minutes of the accident the Ionia county sherriff showed up but we were literally 100 yards short of the county line. Not that he wouldn't have helped if we were hurt, but there was a multiple-injury accident that he was heading to so he called the Lowell city police for us.
About 10-15 minutes later a Lowell officer arrives and guess what, we're just outside the city limits. He explains that he gladly would've handled our accident except that the Michigan state police called him off! Yep, the state troopers had the jurisdiction on this state highway and rather than elect to delegate to Lowell, they insisted on taking our case. The Lowell officer drove off and we waited for the Michigan trooper who was "on his way".
45 minutes later he finally arrives! The tow truck driver had to wait, too - everything was ready to go except for the police. I know it was a busy time with several accidents due to the bizarre weather but Lowell was more than willing to help. I just don't get it.
Anyway the cop sends me off with a "too fast for conditions" ticket because, he explained: "Obviously you lost control, so you were going too fast." Thank you Captain Obvious!
Actually it wasn't nearly so obvious. I was frustrated for the rest of the day trying to figure out exactly why we crashed - after all, I was well below the speed limit, the road was straight, and I wasn't doing anything stupid. After much rumination I think I now have it figured out, but I'll save that for Part 2 of this recap.
As your reward for reading all the way to the end, here are photos I took of the car today as it sits in the wrecker yard waiting for the insurance adjuster to declare its fate.
Yesterday was the 20th anniversary of Northwest Airlines Flight 255, a flight that ended in disaster during takeoff from Detroit Metro Airport. I bring this up for personal reasons: this was the first major plane crash in my memory - I was about to enter 6th grade - and I had just begun an interest in aviation. My family and I lived less than an hour's drive from the airport and this accident was a prominent news story for a long time locally.
What Happened?
Flight 255 was an MD-82 loaded with 149 passengers and 6 crew bound for Phoenix from Detroit that evening. The aircraft was unable to gain altitude after liftoff and ultimately crashed inverted into a highway overpass just outside the airport property. 156 people died; 154 on the aircraft and 2 on the ground who were driving on the road at the time. Amazingly a 4-year-old girl survived (with serious burns and other injuries) what was essentially an unsurvivable accident.
How Did It Happen?
The short story is that the aircrew forgot to extend the flaps and slats for takeoff. Extension of the flaps and slats on the wings increases lift, which can be crucial when an aircraft is filled to near capacity as Flight 255 was that night. The aircraft was able to take off - barely - but didn't have much extra lift for climbing. As the aircrew continued to pull up on the control column, they inadvertently raised the wings to an angle of attack that was unsustainable without the flaps and slats extended. Airflow over the wings stalled, losing lift, and the left wing clipped a light pole which severed 17 feet of wing - at which point the crash was inevitable.
Why Did It Happen?
The details are spelled out in the full, 146-page NTSB report on the accident. A way I like to answer this is to look at the chain of events contributing to the accident; had any one of these events been different, the flight likely would've been able to take off safely:
- The aircrew did not extend the flaps and slats as was listed in their "before takeoff" checklist.
- The central aural warning system (CAWS) was non-functional due to an unexplained loss of power.
- The flight was almost fully loaded and would require flaps and slats for a successful takeoff.
- When the aircraft didn't gain altitude, the pilot continued to pull up, stalling the airflow over the wings.
- As the wings began to stall, the aircraft "wobbled" - rolling left and right upwards of 30 degrees - and on the 5th "wobble" as the left wing rolled 22 degrees, it contacted a 42-foot light pole 5 feet below the top.
And now to explore the "what if" scenarios that correspond to the above causal events:
- If the aircrew had remembered to extend the flaps and slats, the takeoff would've been perfectly normal.
- If the CAWS had been functional, it would've alerted the aircrew that the flaps and slats weren't in the takeoff configuration before they got on the runway.
- If the flight had been lightly loaded, it likely would've taken off safely even without flaps or slats extended.
- If the pilot had resisted the natural temptation to pull up, the aircraft would've still climbed slowly but would've cleared the light pole by 80 feet.
- If the left wing had dipped just 4 degrees less, it would've cleared the light pole by a couple feet and the aircraft might have been able to continue its slow climb to safety.
Who Was Affected?
Friends and family of the Flight 255 victims were clearly affected. So too was the entire airline industry and aviation community. That much is obvious, but there was at least one other non-involved person upon whom an impression was made...
As an 11-year-old back then I was captivated not only by the drama surrounding a huge flying machine, but also the highly improbable chain of events that led to the crash. Since then I've read literally thousands of accident reports and during college was even considering a career as an NTSB accident investigator. I still read accident reports and follow such news with interest, and it all started with Flight 255.
