Thursday, October 12, 2006

Killing Zone

In my spare time, I've been reading a book entitled The Killing Zone by Paul Craig. The book's thesis is that pilots whose number of flight hours fall within a particular range are more likely to be involved in fatal accidents that other pilots with more or less experience. The book draws heavily on NTSB reports and statistics, presenting a compelling argument for several types of flying that pilots should treat with a great deal of respect and care, given their level of experience.

According to the Nall Report, an analysis of GA accident data published each year by the Aircraft Owners and Pilots Association's Air Safety Foundation, the popular ways to get into trouble in a small plane are to run out of fuel, attempt to continue VFR flight into deteriorating weather conditions, and low-level maneuvering flight. The highest risk last year was low-level maneuvering flight and the most likely to lead to a fatality was continued flight into deteriorating weather. While it's early in the accident investigation process, it seems that the crash of an SR20 yesterday into a high-rise building on New York's Upper East Side involved the intersection of at least two of these risk factors - low level flight and marginal VFR weather conditions.

Several other factors have been cited that should have helped mitigate the risks of that flight. News stories have latched onto the fact that the SR20 was equipped with an aircraft parachute that could have saved the day. Even if the 'cute had been deployed, it's unclear whether or not the aircraft would have avoided damage or injury to people on the ground during the descent. I think many Cirrus pilots are hesitant to consider pulling that parachute handle because doing so is guaranteed to total the airframe. The parachute is really a last resort when you can no longer fly the plane. Based on witness reports, it appears the pilot and instructor were still trying to fly the plane.

This brings up the second factor that should have made the flight less risky - the report that there was a flight instructor on board. According to the Nall Report, flying with a flight instructor is statistically the safest GA flying you can do. I haven't yet seen an attempt to quantify the instructor's level of experience with the level of safety, but it is my experience is that younger, low-time instructors are hungry. Many of these instructors seem willing to fly in marginal weather since flying is how they earn their meager income and build the flight time required to move on to better paying, more respectable flying. Add to this equation a client who really wants to fly that day and you have the potential for some risky decision making.

The last factor that has been mentioned is the advanced avionics found in Cirrus aircraft, which some say should have prevented the crash. I don't know the vintage of the SR20 involved in the accident, but some of the older SR20s are steam gauge planes and lack many of the advanced features of the later models. And this just in - a glass panel cannot keep a pilot from hitting an obstruction. Used properly, terrain awareness can increase the safety of flight, but it is no guarantee.

After learning of the accident, I did a quick check of the surface weather observations for Tereboro Airport, where the flight originated, for the time period before and after the accident.

KTEB 111551Z 10007KT 060V120 7SM OVC015 17/12 A2994 RMK AO2 SLP139 T01670117
KTEB 111651Z 11007KT 7SM OVC015 17/12 A2993 RMK AO2 SLP133 T01670122
KTEB 111751Z 09007KT 7SM OVC017 17/12 A2990 RMK AO2 SLP125 T01670122 10172 20150 58017
KTEB 111851Z 08007KT 7SM OVC019 17/13 A2987 RMK AO2 SLP115 T01720128
KTEB 111951Z COR 09008KT 3SM DZ OVC019 17/13 A2986 RMK AO2 DZB48 SLP109 P0000 T01720128
KTEB 112031Z 07004KT 2SM RA OVC017 17/13 A2985 RMK AO2 DZE02RAB02 P0005
KTEB 112051Z VRB05KT 2SM -RA OVC019 16/13 A2984 RMK AO2 DZE02RAB02 SLP106 P0010 60010 T01610133 56020

It's too early to know all the details of this particular crash, but it clearly was not a good day to be flying VFR. While the visibly at times was more than 5 miles, the cloud ceiling was never above 2000 feet.

The probability of a technically advanced aircraft with a qualified and appropriately rated flight instructor on board flying into a building at a low altitude in marginal VFR conditions is very, very low, but that probability is not zero. If you think it can't happen to you, think again.


Anonymous said...

"The Killing Zone" is an excellent book and should be assigned to every student as required reading by CFI's.

I had the exact same thought when they were talking about the chute, which doesn't save the plane from pilot error.

Well said.

Neil said...

Well said indeed.

Ive tried to answer alot of questions about yesterdays events from co-workers and friends, being the only pilot they know, apparently, and also as a pilot preparing to fly a new Cirrus. I avoid speculation in cases such as this at all costs, but I point out exactly what you have done here. Parachutes, the avionics suite, an instructor in the right seat, all great steps towards safety in GA aircraft, but you will never be able to foolproof the system to where pilot error is no longer a factor. We just continue to learn and respect the responsibilty of flying an aircraft, and hope everyone else does too. The fallout in the media from this event has been as expected I suppose, but incredibly disapointing none the less...

Nicely done as always, John, and I'll look into that book.

Jack said...

I've heard good things about the book John...definitely on my list of things to read.

It will be interesting to read the NTSB's final report on this one.

Dave Starr said...

Thanks for the tip on the book as well, John. I often remember rule of thumb conclusions along the same lines from some of my instructors back in the dim and distant past.

The TEB sequences are born out by the news videos within minutes after the crash ... in fact before the flight history was known I thought the accident aircraft might have been just out of or inbound to LGA, and the camera views I saw certainly didn't look very much like VFR.

I haven't been current for years, but I stay mentally active. I learned to fly out of N07, I've been in and out of TEB often and we used to go over to LGA late in the evening and get ASR's from the long-suffering controllers after the evening pushes were over.

According to reports and looking at the map the flight was probably technically legal, but flying down the East River into a "box canyon" of uncontrolled air space and only an 1100' "lid" is one of the other risk factors to think about ... it's akin to the high-speed "lane splitting" one sees adventurous motorcyclists demonstrating on California freeways ... probably technically legal but with absolutely no margin of error.

One thing that might keep a lot of pilot's safer is to think as if there were no insurance and the whole cost of a $300K Cirrus would come out of your own pocket. If I were able to buy an SR-20 I wouldn't be flying it over a river with no place to land at <1,100 feet ... what if the engine hiccuped? I'd need three lifetimes to pay off that debt. I'd rather fly it where I had someplace to land.

Kevin said...

I was in that area at that time on that day. I am a Cherokee Six pilot and will be taking my IFR checkride on December 6th.

I would not have been flying on that day.

It is also perhaps worthy of note that the location of the accident was exactly opposite (on the other side of the East River) from the Yankee Stadium - where the P-I-C was a pitcher. Perhaps a buzzing gone wrong?

Just a thought.

Greybeard said...

With time in Cirrus aircraft, you are a good one to advise....
Does it seem like there are an awful lot of accidents in Cirrus machines lately?
The Ballistic 'chute is a great idea, but it sure seems like Cirrus aircraft are involved in more than their fair share of incidents/accidents recently.
I'm hearing insurance rates on them are terrible.
I'd like your thoughts, please.

John said...


I don't know if there have been a disproportionately high number of Cirrus accidents. There certainly are a lot of these aircraft in service now, given that Cirrus has sold more single-engine aircraft than any other manufacturer for the last couple of years.

While the ballistic parachute has saved several lives, it can't always save a pilot who has made poor aeronautical decisions and has gotten him/herself into a tight spot. Many non-Cirrus pilot don't realize there are airspeed and altitude limitations for a successful parachute deployment - It is a parachute, after all, not a whole-plane airbag.

There is research that suggests that new automobile features like airbags and anti-lock brakes have resulted in some people driving more aggressively, effectively canceling out the added margin of safety these devices are meant to provide. I've often wondered if the inclusion of features like the parachute, non-certified anti-icing equipment, glass panel, terrain awareness, and XM weather has led some Cirrus pilots to make some risky aeronautical conclusions.

I remind Cirrus pilots that while you are flying a high-performance, go-somewhere kind of aircraft with a lot of capability and safety features, you are not invincible. A Cirrus is a single-engine (predominantly non-turbocharged), fixed gear airplane and is heir to all of the same dangers faced by a 35 year old Cessna or Piper or Beechcraft or Mooney.

Neil said...

I think those are great points, and echo my thoughts exactly. As ive mentioned on my blog, I will soon be the PIC of a Cirrus SR-22. Im keeping it in my head all the time that:

A) You still need to look out the bloody window, despite the huge amount of information available inside the aircraft.

B) A parachute means nothing until you are ready to give up your airplane and your life.

I alos feel like Cirrus may be a little irresponsible in the marketing of these aircraft. They are marketing them as super safe (It has a parachute! What could possibly go worng!?) and they are targeting new pilots. I also beleive that with all that information infront of you, you can forget the basics of safe flying, and develop an invincibility complex. All pitfalls I plan to avoid in my SR-22.

It also concerns me that other companies appear to be taking the same marketing approach, except they are selling VLJ's...(Eclipse, et al)

Eric Gideon said...

I agree - Cirrus targeting new pilots is irresponsible. It's a ridiculously high-performance machine, and in my experience the side-yoke is remarkably sensitive to the slightest pitch input.

Cessna's thinking with their LSA design - using it as an entry-level aircraft much like the good old 150/152 - is a lot more logical and probably a lot safer. It's much easier to put a 160 knot airplane in the wrong place at the wrong time than it is a 90 or 100 knot one, and a lot harder to get it out again.

Stephen Wilson said...

Dead pilots dont lie.  NTSB reports show Cirrus planes advertised with a safety parachute are three times more deadly than their aluminum rival without.

eric said...

Great comments and posts!
I agree with Eric Gideon and I'm finding people coming to me as a CFI, and saying "I'm going to buy an SR22 and I want you to train me. By the way, I have been in a small plane only a couple of times." Marketing is implying that this SR22 will look good next to your BMW, so why not?! It goes 180kts!! It has a parachute!! What could go wrong?? The problem is that these individuals are thinking about whether they can, when they should be asking themselves whether they should. Terrifying...I truly hope that the strong work of COPA, and their push for training, more training, and recurrent training (along with Cirrus) will turn the tables on the chain of events that have led to numerous recent Cirrus fatalities.

William Knecht said...

Unfortunately, Craig repeatedly commits a rather serious statistical error in this book. He uses accident frequency counts, rather than accident rates, as the statistical basis for his conclusions about the range of the "killing zone." Frequency counts are interesting, of course, but they don't account for the number of pilots at each range of flight hours (which accounts for most of the effect he claims). Therefore, they say little about the risk that you yourself face as your flight experience increases. My concern is the nature of that zone, and that we use the right methodologies to explore the issue. You'll have to forgive me for being geeky about this. It's just that it's part of what I do for a well-known agency having to do with aviation (which can't be named, because I'm speaking here as a private citizen).
Statistically, rates aren't interchangeable with frequencies. Rates subtract the effect of how many individuals are present in each "bin" of a frequency distribution (in this case, the y-axis, where the x-axis would be flight hours). In fact, it appears that about 70% of the "zone" may be an artifact, and can be explained just by the fact that the frequency distribution of NON-accident pilots looks nearly identical to the distribution of accident pilots. See my paper regarding this.

Bottom line: The kind of analysis we use on data like these is very tricky, is all I'm saying.