Black holes and little grey cells - Spatial disorientation during NVFR
Black holes and little grey cells
Spatial disorientation during NVFR
Ah! Bonjour! Let me introduce myself. My name is Poirot. Hermes Poirot. Yes that’s right. You have probably heard of my famous brother, the detective Hercule Poirot. You know, Murder on the Orient Express? Or most likely, you have seen him on TV. He catches crooks as he keeps saying, "by using his little grey cells” [puts finger to his temple]. So what is usual about that? You are all pilots like me, no? You use your grey cells every time you fly. With each takeoff, you use the knowledge and wisdom of your training and experience, but, listen to this.
When these aircraft crashed they were being flown by well-trained experienced pilots whose skills and talents had made them a success in their profession. So how did they all end up as aviation safety statistics? Well, there was another common factor involved here. They were all flying at night. Mind you, they all had their night endorsements. That alone calls for 10 hours of instrument training.
Similar to this pair, off to visit some relatives up north. Both pilots, with several hundred hours to their credit, and well trained for night flying, they seem to have done all the right things. It’s a long flight, so they both got some rest beforehand. When they filed their flight plan, they picked out an alternative destination, organized their maps and flight supplements for swift and easy access in a darkened cockpit.
They saw to it that, along with the taxi and landing lights, the interior lights were also working, and that they were carrying the required number of spare fuses. Finally, they checked their flashlights.
They certainly will want to be able to see the panel clearly, but not so much that it interferes with their night vision.
Takeoff. All is well, EXCEPT…
A few hundred feet ahead lurks a trap that has caught many who were convinced they were doing all the right things.
It’s called the somatogravic illusion, and it works its nastiness this way:
As you pick up speed down the runway and then rotate, the gravitational pull and the acceleration affects your inner ear in such a way you have the sensation that your pitch up is continuing to increase. It’s no problem in the daytime, all that visual information outside the aircraft lets you ignore the sensation. But at night, that information isn’t there and if you fall for the sensation, you’re going to push the nose down with disastrous results.
Such was the case with this Piper Chieftain taking off one January night from Rainbow Lake in Alberta. The runway had low intensity edge lights, and red end lights. It was a somatogravic illusion, which in the dark beyond the runway convinced the pilot he was pitching up and caused him to push the nose down. They found the plane in the trees some 3000 feet from the airport. It had been in a 3-degree descent at the time.
This is a VFR flight, yes, but they still keep a rigorous cross check on their instruments- on the ASI, the vertical speed indicator, and the altimeter- to ensure the aircraft maintains a positive rate of climb.
Spatial disorientation at night can give rotary wing pilots their own special problems. All that glass around the pilot during a daytime takeoff provides a number of visual references, but at night, it can become a handicap. Fact is, whether it’s a starry sky above and blackness below, or black above and lights below, both set of circumstances can play tricks on the human eye. So, maintain a close check on your flight instruments, and whatever your style may be during daytime takeoffs, at night the wisest rule is “altitude over airspeed”.
While you’re on route, a night flight can be a real dream. Especially on moonlit nights- no turbulence. That cozy feeling you can get from the panel and cockpit light. But never forget, it’s still a night flight with all of its risks. So as they did during takeoff, our couple are making use of all the information their instrument panel offers. From VORs and NDPs to GPS, they know they’d be foolish to ignore such resources. Especially, since their flight plan is taking them over large uninhabited areas as well as some mountainous terrain.
And then there’s weather. It can be bad enough in the daytime. At night, chances are you won’t see it coming. Indeed, VFR into IMC accounts for close to 30% of nighttime accidents. Stay away from it. But if you do inadvertently run into weather, then do the next best thing, get out of it. Because if you don’t, well, an aviation study with 20 student pilots at the University of Illinois found that life expectancy in such circumstances is less than 3 minutes.
Anyone flying VFR at night should at the very least know how to execute an immediate rate 1-180 degree turn. That by the way demands some instrument proficiency.
Helicopter pilots aren’t the only ones a starry night can play tricks on. A fixed-wing pilot can often find it difficult to distinguish between lights on the ground and the stars. The result is you no longer know where the horizon is, until of course you fly straight into it.
Finally, as you approach your destination, there is possibly one more illusion awaiting you- the most insidious of all- it’s called the black hole. No matter how much training and experience you may have, it’s an effect that just won’t go away.
It happens when an aircraft is making its final approach over a body of water or over dark ground. In such circumstances, most pilots will overestimate their altitude. Unless they follow their instruments, they’ll lower their glide path and take the aircraft straight into the water or the ground short of the runway.
It’s an illusion which is particularly pronounced around airports in sparsely settled areas as well as those on a coast or lakeshore. Even an airport near a city can trap you. When its bright lights are stretched out on the far side of the airport and your approach is over dark featureless terrain.
Take what happened one early spring night to a Beechcraft C99 on approach to Moosonee. The trip on route had been flown IFR in cloudy, often overcast weather. Now on approach, the crew elected to do a VOR approach to Runway 24. They were 5 miles outbound when they intercepted the 061 radial and started their descent. Breaking through the lower cloud at 900 feet, and with the airport lights clearly in sight, the captain switched to a visual approach. Later, they found the crash approximately 6 miles short of the threshold.
So, what happened?
To begin with, the terrain below the aircraft was under 2 feet of water from a spring runoff. This, and the cloud cover, had created a dark, featureless landscape. At the other end of the airport were the city lights. Moosonee happens to be spread out on a North-South axis. All this makes it difficult to perceive angles when on approach at night from the East. The crew had fallen victim to the black hole illusion.
How do you beat it? There are several things you can do. First, if there is no glide slope guidance such as VASI or PAPI, then avoid a straight in approach. Keep a close watch on your altimeter, your airspeed indicator, and vertical speed indicator indicating your rate of descent. But before all that, come in at an altitude that is high enough for you to have a clear view of the airport and the runway lighting. And remember, if you are flying an IFR approach and the runway becomes visible, do not be in a hurry to disregard your instruments or to descend below the glide path that you have been flying. Continue to use the information your instruments are telling you. It may prevent you from landing short.
So now you’re over the fence. Use the lights at the end of the runway as your cue when to flare. It’s even easier to do this at night. Also, be prepared to overshoot which brings you right back to the beginning. You’re going to hit the throttle, pull up the nose, and there’ll be the somatogravic illusion all over again. Don’t let it seduce you. Believe your instruments and adhere to that positive rate of climb.
Ironically, experience can also work against you in night flying. It can happen when you’ve flown into a particular airport more times than you can remember. Beware of complacency.
There it is. All that experience and training… Like all of us who fly at night, we are well aware of the risks. From failing to see other traffic, going off course, or even losing power. But all that safely tucked away in those little grey cells [puts finger to temple] was fooled by something that’s not even real- an illusion. But what is real, is right there in front of you: in your flight planning and cockpit organization, in what you read on your instrument panel- both during takeoff and landing- and in your MET reports and NOTAMS.
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© Minister of Public Works and Government Services Canada, 2000