RansS9,
I've been flying ag and doing low altitude operations such as firefighting for many years now. That includes crop dusting, animal tracking and a host of other duties which required flying close to terrain. Some of my flying has been in flat terrain such as doing corn, wheat, and other row crops...but most of it has been in mountainous terrain. I've done this in light piston singles, medium turbine singles, all the way up through large four engine piston and turbine airplanes.
I'm rather leary of counseling someone over an anonymous web board regarding how to fly their airplane at low level. Extended flight at low level isn't really a skill applicable to making a force landing. For the private pilot, it's more something one might use to scud run or go play. Both can be a dangerous undertaking without proper preparation, training, and experience.
I'm not going to attempt to teach you how to do this over the internet, but I will discuss some common pitfalls and mistakes in the hopes one doesn't repeat them.
For a new ag pilot, one of the most common errors is striking the wheels on the furrows in the field, or dragging them in the crop. This comes from the inability to hold altitude properly, and in ag flying, a precise ground track and a precise altitude is very important (for several reasons, not all of which are applicable here). Part of this is lack of experience in judging height above ground...if you're low, flying is very much a heads-up endevor, and you need to have an intuitive understanding of your altitude...which can be measured in inches, or feet (or centimeters and meters, I suppose). This becomes particularly important when flying near intervening obstacles such as fences, powerlines, etc. You need to know you can clear those obstacles and by how much, as well as changes in the terrain beneath you.
I was spraying in Kansas (USA) when the Dromader was first introduced in the USA. At the time it was the biggest thing out there, with a 600 gallon hopper and a big russian/polish version of the R-1820 motor on it. A gentleman just south of us was working one. He was entering a field which had some tall weeds growing up along fenceline where he entered the field. He was experienced, and he was flying a large, heavy, fully loaded airplane. He dragged his wheels slightly through the tips of the weeds on his entry back into the field.
Unbeknownst to him, a corral was in the weeds, and he caught the top of a cedar post fence with one wheel. One would think the fencepost would have been pulled right out of the ground or at least broken off, but it wasn't. It stopped him so quickly that the airplane hardly skidded. It flipped over, broke the spar over the cockpit, cracked the hopper, and he drowned in the chemical. It doesn't take much to bring your flight to a crashing halt sooner than you might like.
obviously getting too low is bad. But how do you know when you're too low? You can fly over level ground fairly easily enough, but what about crossing obstacles such as fences, vehicles, and powerlines? Wires are a big hazard that bring down a number of airplanes ever year, and result in a number of fatalities. These can slice up your airplane like a knife through butter, or simply tear it apart. I've seen airplanes shredded, and thick parts such as the propeller cut as cleanly as though they'd been pushed through a band saw. Canopies shattered, wingtips removed, wings and horizontal stabs and vertical stabs removed, spray booms stripped off, and airplanes destroyed. Powerlines, guy wires on towers, support lines, etc...often can be nearly invisible. Very hard to see. Often there are more than you think, and they may come off at unusual angles or places where you don't expect them.
One rule of thumb is always looking for the highest obstacle or point, and clearing that. In the case of a powerline, one shouldn't attempt to cross any lower than the top of the pole. Yes, the wires sag in between, but there may be wires you don't see, and gauging a suspended obstacle for clearance is not easy. Additionally, some wires use smaller, nearly invisible supports on top of the poles for additional wires you may not see, and wires do extend from poles as supports when they change direction or experience a change in tension. In ag work, illegal powertaps without any poles to warn the wire is there can be especially dangerous.
One requirement in ag is to occasionally work underneath powerlines. This is something to not be taken lightly, and increases the hazards from a number of angles. You should consider any straight line you see on the ground as having a fence or a powerline with it. This means if you're making a forced landing, try not to do so where you'll be crossing straight lines such as roads, divisions between fields, etc...these nearly always have a fence or a powerline, or both, that you won't always see until it's too late. Assume any straight line has obstacles.
We used to do a lot of operating from roads. Farm roads, country roads, highways. Light general aviation airplanes, ag aircraft, et. Again, your wings stick out there farther than you think. If you've ever wandered from the centerline during a takeoff or landing, you can perhaps imagine what the increased consequences might be of signage alongside the road, powerlines crossing overhead, ditches alongside the road, fences, and other vehicles in your path. Where you have room to deviate around on a runway, you don't on a road. This applies to landing on one, or taking off. If a road looks attractive during a forced landing, it might be a good choice, but it may also be a trap.
Another common problem of low altitude flight is turning. It seems intuitive enough; bank and turn. However, part of banking is raising one wing and lowering the other. In low level flight however, you have to be sure to raise one wing and not lower the other. This involves a small climb in the turn, increasing with the angle of bank, to prevent the wingtip from striking the ground. Forgetting wingtips is a big thing in low altitude flight. The same comes in making turns or crosswind corrections close to the ground. The wings MUST stay parallel to the ground and the corrections made with the rudder, if you're within a wingspan of the ground. Dipping a wing just slightly, when you're concentrating on avoiding the ground and obstacles, with your attention diverted, can quickly roll you up in a ball.
Perspective during turns at low altitude is different than your perspective at higher altitudes. You may have done your ground reference maneuvers as a student at 500 to 800', but this is high altitude compared to flying close to the ground. Among other things, you have the ground rushing by in your perepherial vision. It's easy to let the sensation of the ground as a reference influence the way you make your turn, and you may find yourself pulling turns tighter because of various illusions or perceptions that occur down low. You may find yourself concentrating on the objects on the ground and losing altitude; you can lose a hundred feet in normal maneuvering and not thing twice about it, but fifteen feet during low altitude flying can kill you.
The US Border Patrol had a series of crashes in Husky's when they first started using the airplane. Most of them were traced to pilots flyin the airpalne into the ground while turning about a point. It's one thing to do this at 800', but it's another to do this at 30'. They were making these turns while chasing people on the ground or tracking people, and with a focus on the job at hand, altitude awareness went out the window. At one point the Border Patrol decided the airplanes must be unsafe...but it wasn't the airplane. It was the pilots.
You've already addressed some of the salient points of flying low; you know it's potentially dangerous, and you know you shouldn't be doing it. I'll add to that by stressing the same things you already mentioned. Low altitude operations can be conducted safely if you have the experience and the training and are prepared to do it. If not, it can be deadly. There's nothing down low that isn't at altitude (save for obstacles, windshear, cetain illusions, ground effect, etc)...but it's the pilot that's the most dangerous component in the airplane. As always.
A technique that many use when down low is to roll in a little "up" trim. That is, I'm always holding a little forward pressure on the stick. In a moment of inattention, the airplane will climb. Zero or neutral trim...no. Positive, or up trim, yes. I tend to fly the same way for takeoff and landing, too.
A very important point to consider is that you need to be prepared to put the airplane down at any time. Right here, right now. No holding off while seeking best glide speed, no searching for an appropriate road or field. When the engine fails, if you've failed to keep it in the forefront of your mind all the tiem, you're committed to whatever is in front of you. Good or bad. If you do keep it in the forefront of your mind, you'll always keep a viable option in front of you, and always plan an "out" or an escape.
Flying low places you at risk for birds, powerlines, trees, etc. A bird strike at a higher altitude is usually a distraction. It's a distraction down low, too, but you can't afford distractions, or to allow your prioritizing of flying the airplane to be affected by the distractions that may occur.
When flying low, you're going to need to look somewhere aside from straight ahead. When you do, your natural tendency is to compensate with your hands and feet, but looking one way, especially with the ground rushing by, can cause you turn turn the other, or vary your altitude (climbing usually is a lot safer than descending...what if you descend?). The tendency to do this is compounded even more in a turn.
Avoid obstacles. Judging your distance from a powerline, fence, or tree when you're flying by at 120 knots or higher can be difficult. It's very easy to drift laterally and end up catching a wingtip. Don't do that. Stay away from obstacles.
I'd caution you again and again to stay away from low level flying without the proper training, experience and preparation. I've discussed a few things to avoid. Some things are not to be avoided, and that included proper training from a competent and experienced instructor. Preparation for me means putting on a quality, approved helmet and flying gear. I wear nomex when I'm at low altitude, because having been in the position to make forced landings from low altitude before, I know anything is possible. I carry seat belt cutters, and a large knife to cut and break my way out of the airplane if the canopy won't release. I wear nomex and leather gloves, full length leather boots, and eye protection. These aren't things I would normally wear if flying a 172 from A to B, but things which have proven very beneficial, even lifesaving.
Low altitude planning includes becoming familiar with the place where you'll be flying. This often includes a visit to the area you'll be flying before hand, a close survey for obstacles, entry points, escape points, etc. It also occurs when you approach the area you'll be flying; circling the area at a safe altitude, looking for obstacles and obstructions, noting the lay of land, unusual wind currents, etc. This can be especially critical in mountainous terrain where there may be only one way in, and one way out.
Low altitude planning includes flying the right equipment for what it is that you're trying to do. Low altitude and low light calls for different equipment (instrumentation, lighting, etc) than strictly day flights, and so forth. The right kind of airplane with adequate power is also important. Arriving at an obstacle and being unable to outclimb it can hurt or kill you. You can do it safely in a J-3 cub if you're prepared to manage the airplane's energy adequately...but you can also get yourself into a real pickle. (That pickle can kill you).
Preparation includes having enough rest. It includes knowing where the sun will be and what you will and won't be able to see. It includes keeping a clean windshield. It includes becoming blindfold familiar with your cockpit; you don't always have the option of looking around for a control or knob when you're down low, and especially if you end up in a crash. You can't reach for the prop knob and grab the mixture; you've got to be right every time, and this means intimate knowledge of your cockpit...if you can be blindfolded and reach and touch any instrument or control on command without feeling for it, then you're getting there.
Experience...there's never any substitute for experience, but there's also only one way to get it...by experiencing it. This is best done under close supervision, following close, discriminating training. And of course, with proper preparation.
There's a certain enjoyment and pleasure to be had flying low, and to be honest, some of my favorite teenage times were chasing around the countryside in a J-3 cub with the doors open smelling fresh cut alfalfa and feeling the wind. I was also employed as an ag pilot then, and had a solid background in low level flight. If one seeks that enjoyment without the proper preparation, training, and experience, one may not have the opportunity to enjoy it for long. Many years ago the National Aerial Applicator's Association published an article detailing the statistical lifespan of an ag pilot At the time the average was seven years. That accounts for pilots who lasted seven years before they got killed on the job, those who lasted not quite their first spray season, and those who went their entire life, trouble free...few ag pilots have gone long without a mishap. I don't know what the statistics are today, but there are a lot of very experienced aviators running around out there who have had one or more mishaps due to low level flight. Don't join them. I lost a friend this year to this very thing. There are many more in times past. I'd just as soon never see another added to the list.
Fly safe.
--I believe Chuck, who posts here regularly, has a fairly lengthy low level background, as well.
Last edited by SNS3Guppy; 30th Nov 2008 at 09:47.