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Stinson L-5 Sentinel
by Budd Davisson, courtesy of www.airbum.com

Contrary to popular belief, L-Birds (as in L-3, L-4, L-5, etc.) don't have to be ugly but it does seem to help. Look at legends like the German Fieseler Storch, now there is a case of real specialized ugly. American designers never got quite as specialized so they never made an airplane that hurt so badly in the looks department. While other countries had some specialized liaison airplanes, the US mass-produced only one special purpose liaison/STOL aircraft: The Stinson L-5. Most of our War Two liaison machines were off-the-shelf civilian birds given some draft papers, a coat of olive drab paint and told to go fight a war with only 65 horsepower.

The L-5 evolved when someone from the military approached the Stinson Division of Vultee Aircraft and said "Build me an airplane that lets me land short. And make the plane so I can really see out of the cockpit. And the aircraft has to be as functional as a jeep. And oh yeah, while you're doing this, to make sure the concept really works, make it ugly!" (Actually, the military asked for a modification of an existing airplane, but Stinson said they could build a better one from scratch, and they did.)

Ugly, obviously, is a subjective term but, in the case of the faithful old L-5 Sentinel, it has to be applied only to aesthetics since, when trees loom large in the windshield, the L-5 is truly a beautiful airplane in which to be aviating. A lot of adjectives can be used to describe a Stinson L-5, but "petite" isn't one of them. In fact there is nothing about the airplane that even comes close to being dainty. Where the L-5's peer group of Piper and Taylorcraft putt-putts derived all of their STOL performance (such as it was) from 65 horsepower and lightweight, the L-5 got its reputation from pure brute force and tank-like strength. Its broad snout covers a six cylinder 0-435-1 Lycoming engine pumping out 190 Clydesdales. That powerplant is bolted to a fuselage tubing structure that looks like it was laid out and executed by a vocational agriculture trade school, using tubing twice the size of that in any other L-Bird, and it is all arc-welded together with farm machinery techniques. Keeping all that bulk off the ground are two gear legs as big around as the average Green Bay Packer's forearm, and each of these gear legs is given a least a foot of vertical travel to transmit big bumps to the inboard shock struts.

It only takes a minimum of investigating and common sense to know the L-5 is the airplane to be flying when you find you have to go through the trees and not over them.

From a prospective buyer's point of view, the wings and tail of the L-5 are by far the most critical components since they are made out of wood, and were part of a wartime philosophy in which machines such as the L-5 were considered expendable. Nobody thought these wooden structures would still be flying over forty years after the fact, so they have to be inspected closely.

THE WINGS USE A TYPE OF STRUCTURE THAT IS almost unique to the L-5 in that they are fabric-covered rib and spar affairs, but they have none of the usual drag anti-drag wires. Instead, these forces are taken out by plywood shear panels which cover the entire bottom of the wings. This imparts great strength and weight to the wings, however, the drain holes at the back of each rib bay absolutely must be clean or a huge amount of water is trapped which eventually can rot all the wood within reach. The same keep-the-drain-holes-clean philosophy applies to the tail. The entire empennage is of plywood monocoque construction with no brace wires so any amount of rot or fungus could help your wife collect on your insurance policy.

If there is one under-designed portion of the airplane, it is the brake system. True to late 1930s/1940s design concepts; the brakes are the old fashion bladder type, ie: a flattened rubber bagel snuggles inside the brake drums with blocks around the outer circumference. As you pump fluid (it must be mineral oil) into the bladder, it expands and forces the blocks against the brake drum which is supposed to stop the airplane. This is not always the case. When using freshly rust-free, turned drums with the rest of the system up to par, the brakes are adequate. However, as soon as you go up in tire size the brakes become increasingly marginal until, when you go out bush-busting with the 10 x 6 tires, your expander tube brakes have all they can do to hold in place during the mag check. That is one reason you see so many of the airplane now fitted with Cleveland disc conversions.

It makes almost no difference what your experience is in aviation or what you are currently flying, you can be guaranteed of getting a real charge out of saddling up an L-5. It is a fun airplane in every possible sense. In the first place when climbing aboard, you actually do "climb aboard." You scramble up the gear leg and the strut, grabbing a hold of fistfuls of steel tubing to hoist your butt up into the formed plywood seat (non-critical materials, remember?). Once on board you are sitting really high in what has to be one of the most starkly finished cockpits you'll ever encounter. "Military Crude" is probably the best way to describe the furnishings. Everything in front and behind you is a maze of tubing, giving the impression of being stuck in a chromate green jungle gym. One of the reasons for noticing the tubing is because, from the waist up, the airplane is entirely plexiglass-so the cockpit is constantly bathed in sunlight and tubing shadows.

Under your left elbow, a flap handle that would do justice to a wheelbarrow juts forward-challenging the pilot to give it a hefty heave, engaging one of the notches in the vertical gate in which it rides. The stick is even bigger than the flap handle and boot-size rudder pedals are on the far end of aluminium clad wooden trays. If the airplane is correctly restored, an archaic-looking carbon pile regulator should be occupying all the space between your feet while your head would be framed by variations of old black boxes that held tube and crystal radio sets.

In the late models-the E and G ambulance version - a crank hangs out of the overhead directly in front of the pilot's forehead which, when turned, will droop the ailerons 15 degrees to make them into "flaperons" for full span additional lift in high pucker factor situations. The ambulance models also have one of the more hysterical military placards you'll run across. It states, "Intentional spinning with litter patients is prohibited." Makes you wonder what ambulance pilots had been doing to fight boredom when returning with a casualty, doesn't it?

One of the very neatest features of the L-5 is the way in which the side windows fold down, letting the crew cruise along with elbows up on the door sill just like doing Van Nuys Boulevard on Saturday night.

O-435 Lycomings are not known for a mellow exhaust tone. They have a very distinct tractor sound that fits very well with the airplane's funky ambiance. You don't notice the noise on first flight, because you're preoccupied watching the way all the glass panels are dancing in unison to the engine rpm. Most of the rattling and clattering is a function of propeller balance. If the airplane has been parked for any length of time with the prop in the vertical position, one blade will pick up water and treat you to a vibrating massage every time you crank it up. We once ferried an L-5 that had sat dormant for a few years and the prop was so far out of balance, the old B-16 compass on top the instrument looked like it was full of root beer foam.

When taxiing out, the high seating position, the jungle gym effect and all the goings on occasioned by the Lycoming melt together to give the feeling you're truly flying a Warbird since there is absolutely nothing even vague civilian about this machine. At this point, the L-5 rates right up there with the Mustangs and Texans in terms of impact but you are getting a much bigger bang for the buck-if only because the bucks are much smaller!

Takeoff is simply a matter of poking the tractor in the rear and waiting. Even though the L-5 has plenty of ponies up front, it's dragging along a pretty good-size carcass so the plane isn't going to leap forward. The Lycoming generates so much wind that you can hoist the tail in the air almost instantaneously and, if any flaps are down, you'll be off the ground almost before you're ready. If a no flap takeoff is elected, with the tail hoisted up past level you'll find she'll run on the mains until ready for a lunch break. Put her in a slightly tail down position and she'll growl down the center line until a suitable speed is found and you're up and flying. During the takeoff a minimum amount of attention is required with your feet unless there is a crosswind, at which point that tiny rudder will be used to try to make up for all that side area.

Don't expect the L-5 to go clawing upstairs like an autogyro. Yes, technically it is a STOL airplane, but you have to apply a little common sense. Just for the heck of it, why don't you give a little bit of margin and not try to make this forty-year-old go hopping high hurdles right off the bat. Incidentally, one variation of the climb-over-the-trees routine is possible but not recommended with the L-5. You can gently cross control, forcing the plane to climb in a corkscrew fashion, making believe you're climbing out of a milk bottle.

If you didn't notice the lack of control friction on the ground, you certainly will in the air because the Stinson L-5 has one of the very best sets of controls of any airplane from that period. In typical Stinson fashion, every single bolt in the control system runs through a bearing. Even the control stick has a bearing stuffed into it which reduces system friction to absolutely zero, totally out of keeping with airplane's appearance. You'd expect something a little heavy, a little crude, a little scratchy, but that is definitely not the case.

Years ago we took delivery of a rather bedraggled G-model after buying it from the Civil Air Patrol on a sealed bid ($1777.77!). The CAP was getting rid of the L-5 because they were having handling difficulties on the pavement with the big tires. I took the bird around the patch to make sure everything worked and was surprised at the controls. On down wind, the controls felt so good I pulled the nose up and did two aileron rolls. The colonel in charge turned to my partner and said, "I've always wanted to do that but never had the guts." He should have done it.

In level flight the L-5 is a joy and then some. With the windows folded down and the breeze whipping around inside the airplane, you have an incredible view of everything. Regardless of what anybody says, there is something to be said for sitting on top of the world in an L-Bird. It is a feeling that doesn't exist in every airplane. Even though the L-5 is incredibly spartan in creature comforts, a careful selection of cushions will make the airplane as comfortable as any you've flown. Be advised that a good intercom is essential if you expect to talk to the passenger because the noise level is very definitely pre-OSHA and very World War Two authentic.

As a cross-country machine, the L-5 is several giant notches above other L-Birds for travelling (with the possible exception of the L-19). Depending on how well the airplane is rigged and you're willingness to lie, the machine will give you an honest 100-115 miles an hour. The downside is you'll be burning in the neighbourhood of 12 gallons an hour, give or take a little.

The L-5 is fun no matter what, but especially fun when you come into land. This can depend on your definition of "fun." Any airspeed number on final is perfectly workable . . . if you are off the ground and flying, you have enough speed in the L-5. The manual does recommend flaps for short field approaches. In reality, the L-5 isn't that fussy, but the slower you approach, the higher the rate of sink and more throttle will be needed to keep from flopping on to the ground like a ton of surplus tank treads. The wing slots give plenty of aileron at all times so don't worry about that aspect of slow air speed. When the flaps and flaperons are out, a near vertical final approach path can be assumed. One of the nicest things about the aircraft is that it can build up an incredible rate of descent, and the pilot can wait until the very last second to nail the throttle which will break the rate of descent almost instantly-allowing a less than spine-crushing arrival. As soon as hitting the ground, stand on the brakes almost as hard as you like and turn the airplane around to find only a few hundred feet of runway have been used. Then you can send your underwear to the laundry. This ability to build up a very controllable high rate of descent makes the airplane much more suited to getting into short fields than even a Super Cub, which just refuses to sink at a high rate.

In more normal approaches to a paved runway, it is worthwhile to pay attention to the directional control. The L-5 is not a difficult airplane to land, but it doesn't have much going for it if you lose control. The rudder is small and has a difficult time overcoming all that vertical fin area while the stock brakes on big wheels will not straighten out a well-developed ground loop. The tail wheel assembly also needs some looking after to make sure the unit is doing its share of steering duties. If you go to sleep at the switch, allowing the airplane to get away, the best you can do is just take off at an angle. If this happens, it's your own fault since the airplane is doing everything so slowly.

As a point of information: The giant 10 x 6 tires look great on L-5s and allow landings on anything up to and including railroad tracks but, as mentioned earlier, they do reduce braking efficiency which is a minor problem compared to what they do to landing gear geometry. When the landing gear extends on takeoff, the bottom edge of the 10 x 6 tire actually swings in and is inside the pivot points of the gear legs. If you make a grease job touch down, it is quite possible for one gear leg to go out and the other one pull in. This creates spectacular ground handling problems. When flying with the big tires it is generally better to make a somewhat sudden arrival, either a wheel landing or a fairly firm three-point to make sure both legs spread. As another point of information, the 10 x 6 tires are reportedly DC-3 tail wheel tires and they are darned expensive.

L-birds in general have become much more popular, a fact easily seen at Oshkosh '86 where everything from L-2s to L-19s seemed to be coming out of the woodwork. Many pilots have discovered the fun of military aviation isn't limited to the big iron and big bucks. And they have discovered the personality lurking behind the curious looks of the lowly L-5. More and more of the hulking Stinsons are being taken out of their glider and tug roles to be restored, refurbished, and refinished until they are far superior to the planes which hopped around the battle-fields of World War Two. Accompanying its popularity, naturally is the tremendous escalation in value. Today it is not unusual to see L-5s in the $20 to $30,000 bracket when only five years ago they were a $4000 machine at the very outside.

As Warbird projects go there is probably no better value than the L-5 . . . especially if you're willing to do much of the work yourself. The supply of spares is rapidly dwindling but it still exceeds the demand in most areas. The airplane requires the builder to check the wood carefully but that is easily balanced by the fact the 0-435 Lycoming is a nearly useless engine since it was used in very few airplanes, making the engine inexpensive to buy. There is an STC for a constant speed propeller but some of the STC parts, ie: cooling eyebrows, are extremely hard to find.

Of the various models of L-5s available, the E and G ambulance variants seem to be most numerous. It should be pointed out that the back seats were second-ary considerations since the airplanes were primarily designed to carry litter patients. The earlier models-the As, Bs and Cs-were designed specifically to allow observers to paste their noses against the side window and report troop movements, etc. Therefore it would seem logical that those back seats would be much more accommodating to the average size body. That's up for verification since most of our flight time is in G-models. With a G-model you can forget about the cramped rear seat and just lay down in the litter position. Who knows. Put a reading lamp back there or a portable TV and your wife might even like it!

If you cut to the bottom line what you have in the Stinson L-5 is an incredibly fun-flying airplane that restores like a really big Cub but has twice the fun and twice the size for practically no increase in purchase price. If you really want to appreciate the airplane as a warbird put its operating budget up against that of a T-6 or a P-51 or B-25, or . . . you get the idea. Go out and put your hands on an L-5 and you'll find it to be one of the most overlooked and underrated airplanes you'll ever have a chance to strap on.