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Serrated blades have their uses and strong points, but not as a primary wilderness blade, in my opinion. Stick to a plain edge for general use. Serrated blades do not lend themselves to many of the carving and chopping chores a knife may be used for. Their forte is slicing, or sawing or tearing, as the case may be. They are particularly good at slicing nylon and similar slick synthetic line, rope and webbed belts and harnesses, as well as clothes and flesh. In other words, they are great for paramedic or law enforcement use or as a defensive blade. They are an acceptable choice for marine survival use which is less demanding of a knife edge and where cutting lines and slicing open fish are the primary uses.
My personal experience is that a well-sharpened plain edge will cut these sorts of materials as well as a serrated edge. However, given that typical public safety users do not care to have to make the effort to maintain an edge (yes, there are always exceptions), serrated blades may be a better choice for these users.
While they would seem to hold their "edge" longer, in fact they do so by relying so much on "sawing" that they will still work for these uses even when quite dull. In addition, the serrations effectively lengthen the cutting edge which means for any given use, it will stay sharp longer, all other things being equal.
Serrated blades can be much more difficult to sharpen in the field, though the right sharpener (round or tapered round, depending upon serration style) and practice will solve this problem. If you're caught out in the field without a knife sharpener, then you are out of luck. You can do a respectable job sharpening a plain edge blade using natural stone. You'll not have much success trying to do that with a serrated blade.
If you feel you just cannot live without a serrated edge, but don't wnat to give up entirely the advantages of a plain edge, look for a blade with something like a 70/30 or 60/40 split between the plain and serrated edge. Or, better yet, carry a separate serrated edge knife, or a knife with a separate serrated blade. I accomplish this by also carrying a multi-purpose tool that includes a serrated blade.
There will be those that argue the need for a serrated blade as the best way to ensure you aren't trapped in your safety harness. Admittedly, a serrated edge knife would do the job better than a plain edge, if you can get to it in the first place. After the impact you may not be able to get it out of its sheath or your pocket. I know of at least one instance where the crash damage prevented the trapped pilot from getting to his knife he kept in his pant pocket (even worse, he was underwater). With a normally configured knife you also risk the possibility of injuring yourself or others in the confusion and disorientation that is likely in a crash severe enough to trap you in your harness.
The solution is simple and
inexpensive. You can easily and safely cut yourself or
others free, if you have a "seat belt safety knife" (also called a "seat belt cutter" or "harness safety knife") readily at hand.
These are rectangular plastic devices with a razor blade embedded at the bottom of an angled
slot. A finger hole or hand grip enables you to easily draw the knife through the belt, slicing
the webbing. It is, essentially, an overgrown version of the envelope openers which have
become so popular in the past few years.
You can find these safety knives at safety and emergency medical supply houses (search the Web using the term "seat belt cutter") for about $5.00. Velcro the safety knife to the shoulder harness or an easily reached spot in the cockpit and it will be there if you ever need it. There are also folding knives available with line cutter blades for this sort of use.
The shape of the blade is the other area subject to considerable disagreement among experts. Just as with blade length, for many experienced woodsmen and many knife makers as well, whatever they are used to using or producing is what they will prefer, no matter how well suited, or not, it may be for others. It will do just fine for them. We can, however, define what attributes in blade shape are best, all around, and what represent less desirable compromises.
A drop point blade, or modifications of this style, is the all around best blade. In a drop point design the back (dull) edge of the blade is generally straight for approximately 1/2 of its length, proceeding toward the tip from the handle of the knife. This edge then slopes gently downward in a mild, continuous curve, much in the same manner as the nose of a shark or the front of an aerodynamically designed sports car. The sharpened edge curves upward to meet the back edge, forming the point of the blade which will be somewhat higher than the longitudinal center or midpoint of the blade's width, from which we get the description, "drop point." This is the most versatile design and is much stronger than the relatively weak, but very common, severe or deep clip point pattern as often epitomized in Bowie style knives and many "traditional" American hunting and pocket knives.
Some clip point blades will do just fine, provided they have a relatively short and straight clip of a robust blade, the net result being a blade shape not far removed from a true drop point. In a severe clip, the clipped portion starts further back on the blade, often only 1/4 to 1/3 of the length away from the handle and then proceeds straight to the point, which is generally located well below the midpoint of the blade's width. With a deep clip the clipped portion of the blade has a concave shape, looking like someone took a scoop out of the forward part of the blade. Both these designs leave the tip relatively narrow and without much mass, relatively speaking, resulting in a weaker tip that is more likely to break off if abused. The deep clip is generally the worse of the two. It is also not quite as functional as a drop point for some survival chores.
The spear point, where the upper and lower portion of the blade meet at the exact midpoint, can be stronger than the traditional deep clip point, if the point at which the edges start to curve towards the tip is well along the length of the blade. While I don't find it as versatile as a drop point, it is still an acceptable choice.
The "tanto" style blade (a chisel point style with oriental influences, not the Lone Ranger's sidekick) is also a very strong design, but it is not nearly as versatile and it really isn't well suited for wilderness survival use. Other common shapes such as skinners, straight point and the like are plenty strong, but lack the versatility of the drop point design.
The bottom line is that what you want to avoid at all costs is a point that is relatively thin, narrow, and therefore, weak, relatively speaking. You want a sturdy point that can take plenty of abuse, yet can still be used for a multitude of survival chores, an effective and versatile compromise. You need a certain amount of edge curve, called "belly," for many tasks. The differences will be obvious when you examine a few knives of various designs. Any good knife catalog or knife shop will be able to illustrate or demonstrate the differences.
Before discussing proportions, let's consider what a knife is used for. It is primarily a slicing tool, not a pry bar. While a knife may be abused and used for tasks other than what it is primarily designed for in a survival situation, it still has to be an effective slicer. Slicing ability depends upon two primary characteristics. First is edge geometry. The more acute the edge angle, the easier it will slice through material. Blade thickness will have an effect as well; the thicker the blade, generally the less acute the edge angle will be, all other things being equal. This varies to a degree by how the blade is ground, so the thickness isn't as important, but can have a detrimental effect if it is too thick.
For an all around survival knife you want a blade which is solid and stiff, rather than flexible, and tough enough to stand up to reasonable abuse. This doesn't mean you need a so-called "sharpened prybar," though some prefer that style.
While there are always exceptions, I'm inclined to say that for a fixed blade knife a minimum thickenss of 1/8 inch (0.1250 in. / 3.2 mm) is probably the place to start. If robustness is more critical to you, 3/16 inch (0.1875 in / 4.8 mm) is probably a good compromise in strength, weight and utility. However, many will find this too thick and too heavy. Some blades even go up to 1/4 inch (0.250 in / 6.4mm) thick, but that's getting almost too heavy, literally in many cases. Thick blades tend to be more difficult to use for fine work, though this can be compensated for by ensuring you carry an auxiliary thinner small fixed blade or folder.
The blade also needs depth, as well, for added strength. A blade with skinny proportions is inherently weaker than one which is deeper. The back or spine should be full for added strength, not sharpened with a false edge or narrowed down, though rounding the top is fine. If the grind doesn't go all the way to the top, that adds strength as well. Hollow ground blades provide a somewhat thinner and therefore keener edge, but lose some strength along the way. However, some excellent knives are hollow ground, that shouldn't elminiate a knife from consideration all by itself. A simple bevel or "vee" ground blade is probably a better choice for survival use. The blade should carry as much of the blade's depth and thickness as close to the tip as possible. Again, avoid styles, like the severe clip point, which have an extended, narrow point. Given the abuse a survival blade can be subjected to, this weaker point design is a serious liability.
A saw back is not essential, nor even desireable, for a survival knife. Saw backs were originally designed into the USAF survival knife to allow for rapid sawing of aluminum aircraft skins and Plexiglas for escape purposes and are nearly useless for wood or bones. Most saw backs these days are designed primarily for the latter uses and many are useless for cutting sheet metal and not very useful for curring wood. Mostly they exist to sell to the unknowledgeable because they look "cool." Hollywood has played an important role in popularizing this style knife, which ought to thereby suggest how undesireable it is. Avoid knives with saw backs.
Splitting wood in a survival situation is typically done by pounding the knife's edge into the end of a log, using a stout branch to hammer on the back spine of the blade. This is referred to as "batoning." Split wood is often crucial for fire building and oftne the only way to find dry wood. Keep that in mind as you select a knife. Saw back designs do not lend themselves to this type of use.
The primary reason you want a solid metal butt or a tang extension beyond the end of the handle material is so you can hammer on the end of the knife if necessary to drive it into something without damaging the handle. This is a useful attribute for a survival knife. A solid pommel or butt can also be used as an improvised hammer, particularly if it is flat sided or flat ended. Steel is much better than brass or aluminum for this purpose. A rock or even a stout piece of wood serves a lot better as a hammer, if available, but there are times when one isn't to be found.
A full or half cross guard (also sometimes referred to as a hilt) will prevent accidental cuts if your hand slips, something you definitely don't need in a survival situation. A half guard is much preferred because it allows better control of the blade when finesse is called for. Some makers machine a small portion of the top back end of the blade with grooves or ridges to create a non-slip spot to put a thumb or finger when needed for such work, a nice touch.
Many knives have a small "choil" (a small diameter cut out) at the back end of the sharp edge, which makes it easier to sharpen the blade. It allows you to sharpen the entire edge without damaging either the stone or the knife. Some designers carry this a step further and cut a larger "finger choil." This allows the user to choke up on the blade by placing the forefinger ahead of the handle and directly at the end of the sharp edge. Some prefer this to allow for more control of the blade for detail work. Others, myself included, see this as a waste of useful edge, which on a smaller blade such as I recommend, is a significant detriment. I've never found a finger choil to be worth the disadvantages it brings. I'be enever had difficulty doing detail work with a fixed blade knife having a conventional finger guard.
A lanyard hole is an important feature to prevent loss of the knife. You don't need to accidentally lose your most valuable survival tool. Always use a wrist lanyard while working with a knife over water or anywhere else where it might be dropped and lost. This wrist lanyard should cinch tight to the wrist (see photo). A simple loop will not prevent loss of the knife, the lanyard will simply slip off your wrist.
The handle should be comfortable to hold in any position, which argues against very deep finger grooves. The best handles are designed to provide a frim grip and to be slip-resistant, especially when wetted with water or blood. This can be accomplished by a design and/or materials. If a handle is too grippy, has too agressive a material or surface, it can cause hot spots and blisters in heavy use. If you are sure you will be wearing gloves, you reduce this possibility, but I prefer to consider worst case and assume I will be using bare hands.
Uncovered metal handles can be a bit of a disadvantage in the desert and similar areas where, if the knife is left in the sun for even a short time, the temperature can rise to the point that it can literally cause burns when picked up with bare hands. You don't need that, especially under survival conditions. Skeletonized knives, made from a single piece of steel with no grips, do offer the advantage of lighter weight. They are a bit less comfortable to use, but that may be an acceptable tradeoff, if weight or size is an important factor. The handle can also be wrapped in parachute cord for better and a more comfortable grip, without much weight gain.
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