Jaun Browne and Dan Gryder have mentioned ground rush as the probable cause leading to inadvertent stall in recent accidents. This seems logical, but also got me thinking about low altitude maneuvering work.

I got to thinking about my lack of ground rush experience in 17,000 hours of crop dusting and pipeline patrolling. There is a bit of ground rush when looking down to clear the wing going over wires. Very quick look and then the turn downwind to set up the teardrop energy management turn back to the crop row fifty feet upwind. On pipeline a quick look out the side window to clear a turn, but obstructions are up into the horizon thus no ground rush. Ground rush should not be a low altitude maneuvering flight problem because effective reconnaissance is out the front windscreen and not out the side window or under the wing. Low altitude raids and reconnaissance across the English Channel in Hurricanes. Spitfires, and P-47s were in low wing airplanes and effective. Crop dusting and patrolling pipeline is just as effective in low wing airplanes.

The optical ground rush or increasing apparent rate of closure is observation of very close terrain out the side window. Normal observation forward encounters targets that appear to close with us at a brisk walk. The advantage of looking out front, if actually low, is that we have more time to dwell on the individual target. Also we can see relevant targets and obstructions. What is beside us is a done deal and no longer relevant.

I understand that shooting forward from non-combat airplanes is difficult. It is illegal, I would think, for civilians. As far as low altitude maneuvering and reconnaissance out the side window goes, physics does not support it. And nothing in aviation is as dangerous as continued level turning around a target looking at ground rush out the side window.

Whether Ag, pipeline patrol, combat reconnaissance, aerial gunnery, or recreational reconnaissance; the only safe to engage target is to the front. Ground rush negates effective abeam reconnaissance down low. It amazes me how well we have learned this driving automobiles, yet have not seemed to pick up on apparent rate of closure problems out the side window. High wing is not necessary for effective patrolling. At high altitude where there is no ground rush, omnivision Cessnas are the cat's meow. Down low, an out the side window point of view is extremely dangerous.

The energy management turn, whether steep or shallow , puts the nose onto the target in a steep (steep turn) or shallow (shallow turn) dive. Since the nose is allowed to go down naturally in all turns, there is no chance that airspeed will deteriorate in the turn as always happens with the level turn about a point.

Is there any usefulness of ground rush? Yes: When we observe ground rush while looking at the numbers on short final, we know we have failed to decelerate enough to land there. We know that next time we need to decelerate on short final in order to continue to close with the numbers at what appears to be a brisk walk. Yes, the same apparent brisk walk rate of closure that we observed further out. Getting slowed down enough to land on the beginning of the runway is all about deceleration on short final to prevent ground rush.

Ground rush, the speed up of the apparent brisk walk rate of closure when close to a target, is the enemy of the high altitude oriented pilot. As Jaun and Dan claim, it is probable cause in many stall fatalities. Ground rush is the friend of the "Stick and Rudder" pilot who uses ground rush to get "all slowed up and ready to squat." At 400', where the stall fatality begins, there should be no ground rush. The pilot should be looking out the front windscreen where the rate of closure with the desired emergency landing zone appears to be a brisk walk. And for the low altitude oriented pilot in an eighty degree bank with the nose well down, 400' is a world of vertical space available.