In Denver Friday, two small private planes crashed into one another over the city. They took off from different airports and had different destinations. It was about 4 p.m., I believe. How is this possible? They had an entire sky to miss each other in. They were not on approach to an airport or anything.
I mean it’s not like they had a highway and had to stay on the pavement. Why were they traveling on the same altitude plane? Why did they not see one another?
I am not a pilot and there is probably a logical pilot response to this but asking as a land-based lifeform. How come?
>> They took off from different airports and had different destinations.
So? Why is this relevant? All that counts is that their paths crossed.
>> They had an entire sky to miss each other in.
There are thousands of small airplanes in the sky at any given time and most do not crash, but with those numbers it is statistically not improbable that a couple of them will crash.
>> Why were they traveling on the same altitude plane?
I believe small airplanes just fly by ear and are not subject to any control from outside.
>> Why did they not see one another?
Maybe bad visibility. Maybe a distraction from the pilots. . . Who knows?
The whole thing does not sound as strange to me as it does to you. Accidents happen.
I’ve read that pilots and drivers often fail to see other vehicles on a collision course. The reason is that the peripheral vision of the human eye is only sensitive to movement. Something on a collision course is moving straight towards you, so it doesn’t move across your field of vision. It just sits on one part of your field of view and slowly grow larger. This can even happen to cars if there is an intersection with clear visibility. If two cars approach a 90-degree intersection at the same steady speed, each driver would see the the other car 45 degrees away from straight ahead. It stays at 45 degrees and steadily grow larger, but since it doesn’t move across your field of view you don’t notice it.
First, let’s keep in mind we know very little of the actual circumstances here. What follows is rampant speculation and examples from my own experience as a small plane pilot.
Yes, the sky is a big place. And there are a LOT of airplanes in it! But aside from that, there ARE “rules of the sky” just like “rules of the road”. Not all that open sky is open to pilots.
For instance, where I fly (around Chicago) I pretty much steer clear of both military training airspace and where the commercial passenger lines fly. Since we have both O’Hare and Midway, not to mention Great Lakes Naval Base and so forth in the area, that alone takes away a fair amount of airspace. Although I can fly through much of those areas, it’s a hassle and subtly discouraged unless you have a reason. For instance, I am legally allowed to land my small plane at Midway airport, but I will be charged a landing fee for doing so - and that fee exceeds the amount I spend per hour renting the airplane. On the other hand, one of my friends recently flew a person from downstate Indiana to Midway in his (my friend’s) small plane so he could get medical treatment at the University of Chicago hospitals. Midway waived the landing fee in that instance, having made prior arrangements with the charitable agency that helped arrange the flight. If I were flying a small airplane into Midway for business-related reasons I could deduct at least some of the fees as a business expense (and hopefully my business profits would exceed costs in such a situation). See how that works? Medical flights often get a break, everyone else pays, and unless you can deduct the fees that cost tends to discourage idle pleasure cruises into the busy airspace.
Here’s the trick - about 25 miles due west of my home airport the commercial traffic “owns” the space from about 2500 feet above mean sea level up to about 8000 feet. They don’t REALLY own it, but that airspace is full of big jets. You are strongly advised to talk to air traffic control, and you’ll have to stay out of the way of the big airplanes. Really, it’s safer for all to just avoid that airspace unless you have a specific reason to be there. This forces the small planes into a “choke point” of about 2000 vertical feet. It’s like a busy road. You have to pay attention.
So, given that this was the Dever area - which has a major airline hub - it’s possible that these two planes were in such a “choke” and therefore much more likely to occupy the same space at the same time.
These “chokes” aren’t a wonderful thing - they do get crowded. But as horrible as a mid-air between small planes is, it’s much better than one involving a big jet with a couple hundred passengers. In part, keeping the bigger, more populated airplanes safe may at times increase the risk somewhat for smaller airplanes. I wouldn’t call it a good thing, but it might be the lesser of two evils.
Mid-airs usually occur near or over airports - that’s where airplanes congregate. It’s hard to get in a fender-bender if no one else is on the road, it’s hard to hit another airplane unless there’s another one nearby. Airplanes converge on airports.
As to why they couldn’t see each other… you know how your car has blind spots? So do airplanes. After all, you can’t see through a metal wing. One classic set up for a mid-air is a high-wing airplane (where the blind spot is above the pilot) and a low-wing (where the blind spot is below the pilot). If the pilots are in each other’s blind spot they of course can’t see each other.
If the news reports are accurate (which they aren’t always) this crash involved a Cessna Skyhawk, a high-wing, and a Piper Cheyenne, a low-wing. It might have been a contributing factor…
I don’t know what the weather was like that day, but a low ceiling of clouds can also compress the small plane traffic into a smaller volume of air. This is offset (usually) by fewer people flying small planes in such weather, but obviously the more room you have to fly in the less likely you are to hit someone else.
As for “same altitude plane” - there are what can be roughly described as “traffic lanes” in the sky. As a general rule, east-bound flights (compass heading 0-179) fly at odd thousands or odd thousands plus 500 (that’s 3000, 3500, 5000, 5500) and west-bound (heading 180-359) fly at even thousands or even thousands plus 500 (4000, 4500, 6000, 6500). But if you’re changing course, turning, or acsending and descending from an airport or cruise altitude you’re “changing lanes”. When do most road accidents occur on the freeway? Lane changes. Likewise, a pilot must exercise caution when 'changing lanes" in the sky. (actually, you exercise caution all the time, it’s what details you emphasize that differ).
So… we have “lots of planes in the neighborhood” as a possible contribution, “blind spots”, and “lane changes”. Kind of all the things that can contribute to accidents on the freeway, if you think about it, but translated into aviation.
About flight plans and air traffic control (ATC): private airplanes (of any size) are not required to be on a flight plan of any sort (although it’s often a good idea) nor are they always required to talk to air traffic control (although, again, it’s often a good idea). Certain types of airspace require contact with ATC - for instance, there’s a nearby Military Operations Area and whenever I’ve flown through it (either on my own or with another pilot) we always make to contact their control tower to make SURE it’s OK for us to pass through, they know we’re there, and have some idea who we are. Flying into airports of a certain size you also need to talk to ATC. But in between you don’t have to. And the system couldn’t handle everyone trying to. There are times ATC is at full capacity under the current rules and on a typical day for every passenger or cargo jet you see overhead there are five other airplanes flying along that are privately owned. Some are talking to ATC, some aren’t. Most aren’t, in fact, unless the weather is really crappy. Even “talking to ATC” may not involve as much contact as you think. Sometimes it’s a matter of saying “Hey, control tower, I’m taking pictures over here but I’ll say east of this road and north of that one so I shouldn’t interfere with your traffic, but if you need me to move just say so” and the two parties don’t talk past that because they don’t see a need to do so.
Even when you ARE talking to ATC, the final responsibility for pilots to avoid hitting each other rests with the pilots. A pilot is well within his/her authority to refuse to obey a request from ATC if it would put someone in danger, and they are supposed to avoid collisions first and render explanations second. Having had to alter course once or twice for safety reasons, let me assure you that as soon as you deviate from your assigned path ATC will call you and ask what’s wrong and do you require assistance - the assumption being you probably did that for a good reason. (If you didn’t, you could be penalized.)
But if you’re away from the busiest airspace, where radio contact is not required, you “assign” your own altitude and are wholly responsible for your own safety. It’s up to you to minimize your risk, and it’s still possible something might go wrong. If you can’t handle that risk you shouldn’t be in a small airplane.
Believe me, pilots want mid-air collisions less than anyone. But the unfortunate fact is that accidents do happen. What, exactly, happened here we won’t know for awhile (if ever).
This is a good observation. In nautical navigation often the question comes up of how can you tell if your vessel is on a collision course with another vessel. The asnwer is: Constant bearings and diminishing range indicate a collission course. If the bearing moves forward the othr vessel will pass you by the bow and if the bearing moves aft the other vessel will pass you by the stern but if the bearing is constant, then you are on a collission course. And you are very right that animal vision is sensitive to movement. When you can’t find the cursor you move the mouse and the cursor immediately becomes apparent.
The “see and avoid” concept only works if you actually see the other airplane. I have a photo of a low-wing airplane that ended up on top of a high-wing airplane, and the high-wing airplane landed successfully with the low-wing “piggybacked” on top. It’s a perfect illustration of blind spots, but I can’t find the picture online…all the links are old. Anyone know how to get an image from my hard drive into a link?
People also sometimes refer to the “big sky theory”, which is pretty much what the OP referred to - with so much sky out there, how can two airplanes possibly occupy the same space at the same time? I am NOT a believer in this theory - I have come too close to other aircraft enough times to make me a believer in TCAS and vigilant scanning outside.
My experience is different than broomstick’s in that all of my flying has been military and commercial, but the problem areas are the same: busy areas near airports or at key “intersections” of airspace. Kudos to broomstick for talking on the radios before entering MOAs and other airspace - some people forgo even this common-sense approach. The radios can be your friend and give you a clue as to where other airplanes are - but you have to use them.
The “non-movement” in your windscreen factor is also true. I lost a friend in 1997 when his C-141 had a mid-air with a German ariplane off the west coast of Africa. The airplanes hit head-on in daylight at 33,000ft. Numerous factors contributed to this crash, but investigators determined that at the closure rate they had and given normal human visual acuity they had at most 4 seconds from when the other was visible (as an airplane, not a speck) until impact was unaviodable. Granted, this is two jets at high speed coming head-on, but even at prop speeds you can have very little time to recognize that an impact is imminent.
Big sky theory - BAH! With enough airplanes and given enough time, someone will hit someone else.
I am a pilot also but another way to look at it is that they had the entire sky to crash also,and this time they did.It’s possible to miss but possible also to hit,we must always be vigilant.
Virtually Yours
Keep in mind they keep changing around their video clips…search out the video with ** “Former NTSB investigator Greg Feith talks about plane crash investigations, Sat., 8 a.m. Jan. 25, 2003.”** and the guy gave a great explanation.
Basically, he says the conditions were ideal for mid air collisions. The time of day as twilight, the lack of use of the instrumentation, the other planes may look like part of the city lights, etc…
Hope that helps, not sure how long that will remain up though, so catch it quickly.
No - but could you mail me that picture? People ask me why I fly Cessna 150’s. They’re old, they’re slow, they’re unsexy, they’ve hardly changed since 1955… well, yeah, but they can also land with an airplane twice their size on their backs. In a word, they’re tough little planes. (For the record, the one on top is a Piper Warrior or Cherokee. I fly those, too. I don’t think the Piper could carry a plane on top of itself as well at the Cessna did)
Same here - I’ve had several near misses, one so close I could look down and read the other guy’s instrument panel (and my poor husband was watching at the time - from the ground it looked like we had hit. Think he might have been more shook up than me). I don’t have access to TCAS on my little airplanes, but I’m quite cautious about the airspace I’m in or about to enter and if things are especially busy I’ll take an extra person along just to help me look for other airplanes. Heck, going into Oshkosh during the big convention it’s not at all unusual for an airplane with four people in it to have three dliligently looking out the windows and reporting traffic to the pilot - who is also looking. Whatever it takes to stay safe.
What I can’t figure out is why so many DON’T do this. Last thing I need is a F-16 up my backside. Cripes, just the wake from a military jet could rip my plane apart if they’re going fast enough - and they often are. Sure, if the military authorities say “Sorry, the MOA is hot” it’s a pain to go around, but most of the time it’s not an issue. I’ve always found the folks in our local MOA’s quite professional and curteous. Even if the area is being used, if they can still accomodate you they do so - perhaps by assigning you a specific altitude or route - which is well within reason by my way of thinking. Nobody wants a mid-air.
And what everybody said about non-movement meaning a collision course. That’s tough enough at freeway speeds - when you’re dealing with objects traveling at 100 mph, 200, 300, or even faster the problem is much worse. You have an incredibly short period of time to recognize there IS a problem and take the correct action.
My computer doesn’t have sound, so video isn’t terribly useful to me. Are you SURE you have that quote about instrumentation correct?
See, the bit about twilight is straight on - there’s a period between full daylight and full night when you’re vision is in a transition state and doesn’t always register things as it should (a lot of car accidents happen at twilight or dawn, too) And at night (or even twilight) you certainly CAN mistake airplane lights for city lights - and vice versa.
However, too much focus on instruments can contribute to mid-airs as well. If the weather is clear you HAVE TO look out those windows.
I think there is a misunderstanding between using instruments and being on an instrument flight plan.
An instrument flight plan is where you specifically lay out altitutdes and routes, navigate by radio beacons or GPS, and you’re in contact with ATC the whole way. You’re told when to take off, you’re expected to be at certain places at certain times, and so forth. It’s a very controlled experience. In clouds and fogs everyone (well, everyone with more than two brain cells) is on an instrument flight plan, and it’s radar and ATC that keeps them from colliding. (It also creeps me out when I’m in a cockpit with someone flying through the clouds and ATC says “Turn to XX now - EXPEDITE!” It essentially means turn before you whack into someone else. Fortunately, that’s a rare occurrance. And, actually, there are usually literally a mile or more between you and the other guy. It’s just that you don’t take chances in those circumstances.)
The other kind of flying is visual flight rules or VFR. In that sort of flying you don’t ever have to talk to ATC. As I said, YOU, the pilot, determine when you take off, how high you fly, where you go, and so forth - and you take full resposibility for keeping your butt safe. In that sort of flying the instruments are an aid, but you need to keep looking outside. It isn’t just a matter of other airplanes. For instance, there is a 1400 foot building in my area, it would be a real bummer to smack into it (not to mentionthe uproar such an accident would cause). There are big radio towers. In some places there are mountains (like Colorado) so you have to be careful not to fly into rising terrain. As a result, you spend more time looking outside than at the instruments. And that’s perfectly OK and it’s the only safe way to fly in this manner.
Why the two different styles? Well, why do some intersections have stop signs and some have elaborate street lights? It’s a function of traffic volume. Certain training manuvers are always done in daylight and as VFR because it’s not practical or safe to do them on an instrument flight plan or in bad weather. Also, flying on instruments alone is NOT an easy skill to acquire. There’s a sequence involved in learning to fly, and instrument flight plans come considerably after the beginning point. Those who fly only VFR (and I am one) are careful to fly safely - that means stay out of the clouds, and out of the way of the major instrument routes. And if you DO blunder into weather conditions you can’t handle take immediate action to get yourself safely to the ground. Remember that the vast majority of the time this all works.
Anyhow - for very busy areas there is a third option called VFR Flight Following. It’s not an instrument flight plan, but it does provide you a little more protection. You call ATC and request flight following. That lets them know where you are, what you’re flying, and where you want to go. This makes ATC’s job a little easier, and they’re more likely to tell you “hey, jog left to miss that 747”. Unfortunately, this is offered only as ATC workload allows, so sometimes they’ll just flat out say 'sorry, we can’t give you that now". In which case you might want to re-consider your route - that means it’s REALLY busy in there.
Some airspace a VFR pilot is required to contact ATC. Happens all the time: “Fort Wayne approach, this is Cessna XXXXX, I’d like to transit your airspace at 3500 feet, going to ZZZZ, Ohio” Even where it’s not required, even where there is no control tower, pilot’s will often do the same: “Porter County traffic, Cessna XXXX passing overhead at 3000 feet, just passing through”. And that’s one way pilots try to avoid mid-airs - we let each other know where we are, where we’re going, and what we’re doing.
All of which gets back to my question about “instrumentation”. I’d be curious if these folks involved where talking on the radio, if they were using flight following, just what was going on. It IS true that mid-airs are most likely to occur in good weather near airports. Why? In part because in good weather there are more airplanes flying, and they converage on airports. They also converage on route intersections (these locations would not be apparent from the ground). Mid-airs usually occur near urban areas - because there are more planes near urban areas (for the same reason there are more cars in urban areas - there are more people, and more going to and from that location than Nowhere, Idaho). When the weather is good the less-experienced pilots are more likely to be airborne, and in general the less experience the more likely an accident (which is not to say low-time pilots are inherently dangerous, just that the more experience you get the more adept you tend to be at avoiding problems. Just like in driving a car). When the weather is good you are more likely to be distracted by scenery (in a cloud you concentrate on the instruments like your life depends on it - because it does).
The main difference between a head-on car accident and an airplane mid-air is that cars don’t fall hundreds of feet onto someone’s house. Your chances of surviving a head-on in a car might also be marginally greater than an airplane mid-air - two cars meeting head-on at 70 mph makes a heck of a bang. And people have survived airplane mid-airs. In either case, it’s a really BAD accident.
Pilot141: You can’t link directly to an image on your drive-it has to be on a server accessible to the viewer. If you e-mail it to me, I’ll put it up & post a link to this thread …
[quote]
However, too much focus on instruments can contribute to mid-airs as well. If the weather is clear you HAVE TO look out those windows.**
Oh and prior, I was pretty much taking the words that the former NTSB guy said verbatim, maybe a little different but pretty close.
A pilot here in C Springs, said, on our local news last night that one of the planes has pretty good visual (I think the Cesna 172) and the other doesn’t have that good of visual (I think the Cheyenne) which could have been a big factor seeing as it wasn’t a head on collison (still speculation at this point however.)
But, yes, it was twilight so the planes flying at 8,000 feet tend to blend into the surrrounding lights and since Denver doesn’t end at the mountains, I can see this becoming more of an issue.
Also, there are only two standard flight paths from Jeffco Airport to Centennial Airport. But one plane was headed to Cheyenne and I don’t know that flight path.
I spose I could talk to one of my brother’s company pilots (they have two corporate planes, one a single engine and one has two engines which I flew in in 2001) about the conditions in Denver and what they think about what happened. Since they fly around Colorado and other places all the time, I gather they have a good scoop.
Ya, know, I just listened to the clip again…I may have mistaken the words and quoted someone else. He basically said that you do rely more upon visual than instrumentation in clear weather but the twilight may have played a bigger role.
Hmmm, wish I could type fast enough to give you the exact words or they had a transcript on line for those that can’t hear or see the clips.
The visibility in a C172 varies somewhat with the model year. The earlier models, which had fewer flight instruments and therefore had a smaller panel, allowed more of a view than the late-70’s/early-80’s which, in my opinion, built up the instrument panel at the expense of visibility. Post new production (if I recall correctly, no single-engine Cessnas were built 1986- 1998, more or less) there’s still considerable instrumentation (and better instruments!) but they’ve tweaked things so the view is improved. Even the worst C172’s, though, offer a view comparable (in my opinion) to a pickup truck or mini-van. Unsual for airplanes, post-mid-60’s the C172’s offer a rear window, which is very helpful as well.
As a general rule, I’ve found high-performance and small twin engine airplanes to have a poorer view than single-engine airplanes. Since the small singles are much more likely to be a mostly-VFR or entirely-VFR airplane having the bigger windows makes a lot of sense. Small twins are much more often owned by instrument-trained pilots (although not always) and tend to be more often flown in clouds and such where visilbility isn’t such an issue. Even the biggest planes - like airliners, which are flown exclusively on instrument flight plans no matter how nice the weather - still have plenty of window space IF you’re remembering to use it.
I really doubt it was a head-on collision, although I did use that anology earlier. From what I gather (more speculation, of course) the Cessna lost part of the wing - most likely sheared through a fuel tank, accounting for the fire prior to impact - but the Cheyenne didn’t. If it was a true head-on I would have expected fuel tanks on both planes to rupture, or at least more major damage to the Cheyenne (that’s damage before slamming into the ground which, naturally, caused a LOT of damage). Going by the pictures I’ve seen and eye witness reports, I might guess the tail of the Cheyenne sheared off the wing of the Cessna. It is possible one or both planes was turning or diving or both to attempt to avoid a collision, but did so too late.
Although Cessnas have lost the outer third of a wing and landed successfully, those accidents did not involve fuel tanks - or at least not ones with signifcant gas in them. If you slice through the wing close enough to the fuselage to hit a fuel tank you’ve lost at least half the wing and probably the supporting strut as well. Under those circumstances, it’s highly unlikely you’d have enough airplane left to be able to steer. Add rapidly spreading fire from spraying fuel, a plastic windshield that will melt when exposed to burning fuel (I know someone who is an eye witness to melting airplane windows) which will further screw up the aerodynamics… that’s not a survivable situation.
Meanwhile, the Cheyenne seems to have retained functional wings, but if the tail was heavily damaged (likely, if it sheared off another airplane’s wing) you again don’t have enough airplane to steer with. Sort of like Flight 587 crashing over New York after losing it’s vertical stabilizer and rudder. So even without fire you don’t have something you’re going to survive.
That “Crunch!” situation, however, illustrates a survivable mid-air. Obviously, the planes did not hit each other with great violence. Nothing sheared off. This is not very surprising, since the normal airport area speeds of those two airplanes are only about 5-10 miles different in normal operation. They hit slowly. If they had not been in each other’s blind spot they would have had ample time to see this coming and avoid it. The landing gear on the bottom airplane is obviously stressed, but remained intact despite carrying three times it’s designed load (They do add a substantial safety factor to most airplane structures. It can really pay off) Steering was undoubtabley… um… interesting but you have intact wings, tails, and flaps. In other words, you still have a means to make a controlled landing. If I recall, after they got a hoist to get the top airplane off the bottom one they found only minor damage to the aircraft involved. In other words, it’s an arial fender-bender.
Not that that would lessen the pucker-factor at all. If something like that happened to me I think my butthole would squinch up to the point it would suck the entire seat cushion up into my lower intestine. Yowza!
