Dancing in the Dark
Night vision goggles can save a pilot's life or, if he hasn't had adequate training, take it.
- By John Croft
- Air & Space magazine, November 2004
USAF/Tech. SGT. Scott Reed
"YOU READY FOR THIS?" THE EARPHONES INSIDE MY HELMET CRACKLED. It was a cold, moonless night over Texas and I was at 1,200 feet in a jet-black Bell 407 helicopter with Scott Baxter, an instructor with the Fort Worth-based Bell Helicopter Training Academy. From the left seat Baxter was teaching me the finer points of flying with night vision goggles, and it was time to demonstrate their usefulness during one of the more hair-raising events one can experience in a helicopter: autorotation after a simulated engine failure.
Well, was I ready? I had come to Bell's training facility to sample the thrills and chills of flying with night vision goggles. Bell's school is one of only two approved to teach civilian pilots like me how to fly with NVGs. I also wanted to learn why, over the past three decades, pilots have both praised and cursed the devices.
But I didn't come to drop like a rock into the Texas scrub. Fortunately, Baxter had 1,500 hours of NVG time, much of it in situations much more demanding than this, so I nodded: Ready. Simulating engine failure, Baxter chopped the power and the bottom fell out.
There's an old adage instructors use when they teach night flying: If you lose your engine, switch on your landing light and turn toward an area that's dark—presumably there are no houses there. If you don't like what you see when the ground comes into view, turn the light off. There's truth in the dark humor: You can't see the touchdown area with the landing light until you're about 100 feet above the ground, too late to change course very much and almost too late to halt an unpowered helicopter's steep descent.
Baxter planned to show me how NVGs change the equation. But to drive home his point, he wanted me to experience autorotation the old-fashioned way: with the unaided eyeball. So as we plummeted toward a landing at about 2,000 feet per minute, my job was to scour the depths until the landing light revealed whatever we'd be landing on. For an autorotation, you first drop rapidly, so airflow through the rotor disc increases rotor speed, then you convert the rotational energy to lift by pulling up on the collective control to increase the pitch of the blades. Finally, at just the right height above touchdown, you flare—pull the helicopter's nose up with the cyclic control. Start too low and too late and you hit the ground hard. Start too high and too early and you run out of rotor blade energy and hit harder.
Having flown with the NVGs on for only 20 minutes, I already missed them: I couldn't see anything. What looks like black emptiness to the naked eye is revealed in startlingly bright detail with NVGs. Earlier, Baxter had flown over a dark patch at 1,200 feet and had me view what looked like a large puddle of ink, possibly a good spot for an emergency landing. After clicking my NVGs into place, I could see that the ink was actually a lake with a bridge running across it. And there were fine ripples on the surface of the water, indicating wind direction.
I could see the lake, bridge, and ripples because the NVGs extended my visibility range from 690 nanometers, the high end for the human eye, to about 930, which is in the near-infrared region of the electromagnetic spectrum. A broader range renders visible objects illuminated by scattered light from natural sources—starlight, chemical reactions in the upper atmosphere, and auroras, for example—as well as objects lit by artificial sources, like city lights, headlights, fires, and flares.
The moment of enlightenment comes when you look into the darkness with NVGs and see a circular 40-degree emerald-green field of view in which night becomes not quite day but something like twilight. Though Baxter calls it "looking through a toilet paper roll," the view is quite engaging, despite the bulk of a flight helmet with an additional 1.2 pounds of hardware hanging off the front.