Though not exactly a household name, Maules have been around seemingly forever, having found a niche that they fill pretty well: if you want a new four-place taildragger, there arent too many choices any more. While the big manufacturers were dropping like flies in the 1980s, Maule stuck with it, chugging along and producing airplanes at relative bargain prices.
First and foremost, the Maule is a busHPlane, meant to be operated out of extreme airfields while requiring little maintenance. Maules as a group fulfill that mission well. History shows a high accident rate, but given the environment in which these airplanes are typically used, that shouldnt be too much of a surprise.
Maules are a bit like Saabs in that they are decidedly unlike the mainstream, are reliable, and engender great owner loyalty. But, like a Saab, they can have some idiosyncrasies.
There are four basic variations of the Maule, but all are similar enough to cover together: the M-4, M-5, M-6 and M-7, equipped at various times with a variety of powerplants. Construction of all is much the same, with all-metal wings (fabric covered on early M-4s) and a fabric-covered steel-tube fuselage. All are taildraggers except the MXT-7, which is covered in a separate report.
The current model, the M-7, has been in production since 1983. Available with engines ranging from 160 to 235 HP, prices for new ones are anywhere from about $120,000 to roughly $175,000.
The basic round-tailed M-4 Jetasen was born in Michigan in 1962, powered by a 145-HP Continental O-300. 1965 brought the Rocket, a version with a 210-HP Continental IO-360A and constant-speed prop, giving the buyer two airplanes to choose from. The 1967 model year brought with it another choice, the Strata Rocket, with a 220-HP Franklin 6A-350-C1. During these model changes gross weight was raised to 2,300 lbs., and serial production began in Moultrie, Georgia, where the company remains today. The Rocket was dropped for the 1970-72 model years, returning in 1973 as the Lunar Rocket. Also in 1970, a 180-HP version (the Astro Rocket) appeared, with a Franklin 6A-335-B1 and a constant-speed prop; it lasted only two years. The M-4 series stayed in production through 1973.
The M-5 series, which made its appearance in 1974, had the same gross weight, but added quite a bit more tail area, increasing longitudinal and directional stability, while keeping about the same control power. Fuel capacity went from 40 to 70 gallons with the addition of optional tip fuel tanks.
With the demise of the Franklin Engine Co. (and its sale to Poland), the 220-HP version was discontinued after the 1975 model year, leaving only the 210-HP version. To replace it, the Lycoming O-540 series of 235 HP was added to the eligible engine list in 1977, and in 1979 a 180-HP mill was brought back, this time a Lycoming O-360-C1F. 1980 brought a third powerplant choice, a 210-HP turbocharged Lycoming TO-360-C1A6D.
The M-6 came along in 1981 as a companion to the M-5. It bumped the gross weight to 2,500 pounds and lengthened the wings two feet. The flaps were redesigned from the M-5s two-position mode (20 and 40 degrees) to have four positions: 24, 40 and 48 degrees with seven degrees negative to improve cruise drag. Initially, only the big 235-HP Lycoming 540 engine was available on the M-6; in 1985, the 180-HP Lycoming was put on it. The empty weight was raised because of the structural changes, so useful load didnt increase by the full 200 pounds.
In 1984 the M-7 added another nine inches to the wing span thanks to modified wingtips. Since the roll rate of the M-6 was degraded when the plane got its longer span, the M-7 was given new ailerons with more span, and the roll rate was restored.
During the mid-1980s, Maules lineup consisted of the three variants – M-5, M-6 and M-7 – each available with either a 180-HP or 235-HP engine. The M-5 was dropped after 1988, and the M-6 disappeared a couple of years later.
A tricycle gear 180-HP version was added in 1990. Longer ailerons came in with the tri-gear model. The early 1990s saw a variant that didnt catch on, the M-8-235. The latest price guides indicate that there are now no fewer than twelve different versions of the M-7 (the only remaining variant) available, with a choice of three engines (160-HP Lycoming, 180-HP Lycoming, 235-HP Lycoming), fixed or constant-speed props, and conventional or tricycle gear.
Despite the bewildering variety of variations, though, all are still basically Maules. The only significant differences (aside from the gear) lie in the propulsion packages.
The Maule manuals are modest to a fault (though one loyal owner went so far as to excuse this by saying the company was in the airplane manufacturing business, not the publishing business) with no performance figures. Pilots reported such a wide spread of cruise speeds, we hesitate to pass them along. But for the 235-HP versions they ranged from 140 to 165 MPH.
For what its worth, The Aviation Consumer some years ago raced an M-5C 235-HP Maule against an almost equally loaded Piper Dakota to see which was faster. The Dakota walked away from the Maule, flying at least five MPH faster in level flight with both engines firewalled. No surprise here, given the Dakotas all-metal, semi-monococque design that it aerodynamically superior to anything possible with tube and fabric. The 235-HP Dakota also climbed better, though, which was a surprise given the Maules hefty STOL reputation.
One note about cruise performance: the pitot-static system in the early airplanes had a weakness. The static ports were located in the aft part of the engine cowling, and manufacturing tolerances and service wear on the cowling could result in large airspeed errors (and reasonably large altimeter errors, too). By and large, consider this: a good, legal Maule system had the characteristic of being five knots in error at approach speed (reads five knots slow) and five knots fast in cruise.
Those are the limits for FAA certification, and the cowling static port location was just barely able to fit these limits if it was tuned right. It doesnt take much deviation in cowling shape to get this error curve shifted 5-10 knots one way or the other, resulting either in completely unrealistic perceived stall speeds, or seemingly phenomenal cruise performance, but not both at once.
Production tuning was accomplished by first determining the error for each individual airplane in flight test, then jamming an ice pick into the static hole and twisting either forward or backwards, depending on which way the error curve needed to be shifted. Creating a lip of about 0.5 mm on the aft side of the static hole could shift the airspeed curve about five knots toward slower indicated stall and cruise speeds, while twisting the other way could move the curve the other direction. Now, about the probability that this tuning could survive decades of service….
The later aft-fuselage-mounted static ports were much more stable, and the likelihood of service-induced error much less, although they still had the characteristic of indicating about 3-5 knots slow for stall and 3-4 knots fast for cruise. In both types of systems (as in most airplanes), the error at slow speed with big power gets terribly large.
Another note about the Maules legendary weight hauling capability: Way up North, where Maules are popular for easy maintenance, easy starting, and high power loading, you often hear stories of people in the boonies flying out with 1,000 pounds or more of moose in the back. (Who really knows? There arent any scales around.)
Given enough field length and no obstacles, the Maule can do this. But in most cases it isnt legal to go overgross (though there are ways to get ferry permits and such), and the Maule certainly isnt structurally certified for anything more than the nominal 2,300 to 2,500 pounds of the series (heavier for float planes). But way up North, they do it and get away with it most of the time. What do we mean by most of the time? Check the accident statistics; most of those come from northern Canada and Alaska bush operations, going into and out of unimproved fields with big loads.
A brief summary:
Entry: normal pilot and passenger entry is sort of awkward, just as youd expect in a taildragger. But cargo loading is exceptional: the whole side of the airplane opens up, offering easy access to the rear-seat area and the baggage area behind the seats, tempting you to haul much more stuff than the weight limits would allow.
Over-the-nose visibility: excellent for a tail-dragger. No need to zig-zag while taxiing.
Flight visibility: downward is excellent, as you would expect in a high-wing aircraft. The high wing is fairly far forward, reducing visibility into a turn. Plexiglas doors are available as an option, and are useful for ground-spotting work.
Interior noise: bad, about 95 dBA in cruise with the big engines. Headsets and intercom are a must to mitigate this, or earplugs if you fly by yourself.
Seats: The front seats are welded steel tube with a fiberglass casing, and reader feedback seems to indicate no small amount of trouble with either tube or fiberglass cracking. It seems that the seat backs are easy to grab onto for entry and exit, and can get over stressed if somebody pulls real hard. Some years ago Maule beefed up the steel tube structure, adding stronger tubes and gussets; since then, complaints to the factory have died down.
Heating/Venting: Cabin heat comes from a standard exhaust muff, but in older airplanes theres no extra plumbing for heat distribution to the back seat. The windows come equipped with simple circular Plexiglas cutouts that can be positioned to create about as much outside airflow (and noise) as you can stand.
Instruments: The old Stewart-Warner engine cluster gauges could best be described as barely adequate: small dials with nonexistent scales, prone to a fair amount of error, and horrible replacement cost. But they were stable, so that after becoming accustomed to a particular airplane, you also became accustomed to where the gauges normally read.
Fuel gauges: Float type, and sensitive to instantaneous sideslip angle. As in any welded steel-tube airplane, magnetic compasses are hard to calibrate. The compass calibration card says radios on or off. In reality, battery charging current and lighting loads have a much greater effect on compass accuracy than almost any installed radio or accessory (except maybe the Night-Sun spotlights).
Controls: Most switches are standard aircraft hardware items, easy to replace. Maule-manufactured controls such as door-knobs and heater controls need to be ordered from the factory if beyond repair. Engine controls are standard replacement items.
The Maules are characterized by having lots of control power, but not too much stability. That combination usually translates to a maneuvering mans dream. However, there are a few hidden quirks. First and foremost has to be the aileron-rudder connection, manifested by a small rudder tab driven by aileron deflection. The purpose of this is to counter adverse yaw generated by aileron deflection, but in practice it does this only precisely at one speed.
Below this magic speed (maybe around 90 knots in the Maule) there is a slight excess of adverse yaw, and you still need to add rudder for coordinated turns just as with any other airplane, except maybe somewhat less. Above this speed, there is excess rudder force commanded by this fixed-gain device, so what results is proverse yaw, not usually seen on anything but spoiler-equipped aircraft.
The way this proverse yaw is generated, however, results in a characteristic bothersome to some people in cruise, specially in light to moderate turbulence where aileron corrections are constantly being put in. Each roll correction results in a small amount of sideslip in the non-customary direction, causing some pilots to want to continuously fight the system with sympathetic rudder corrections. Most people ignore this and let the airplane find its own way directionally; others have a hard time with it. Its a small item, but for some people small items can become big aggravations. Its a matter of taste.
At low speeds, it can seem that the rudder tab, which in the grand compromise is undersized for this speed regime, is actually subtracting rudder power from the capability to sideslip for crosswinds. That really isnt the case; sideslip capability in all the Maule line is excellent, dominated by larger-than-usual rudder power. The only real glitch in the sideslip area came with early M-7s and the ailerons that were a bit short for the increased span.
When sideslipping in turbulence at low airspeed, you could just about run out of aileron, bouncing off the aileron stop for gust corrections. Full sideslips with full flaps dont hold any surprises as the airplane remains fully controllable down to below stall warning. But depending on the turbulence level, if youre operating at the Maules customary slow approach speeds, you can get gusted to below stall warning speed awfully quick. Unfortunately, nature usually combines gusts with crosswinds, so these approach speeds need to be bumped up to compensate.
There is no magic formula for this, other than to add the amount of gust (if reported) to the approach speed. For the Maule (and all other STOL types), this exacts a pretty big penalty compared to other more conventional aircraft, because the Maules basic approach speed in calm air can be safely, but hair-raisingly slow.
Center of gravity and water stability dictate where floats need to be installed. This usually means that the airborne directional stability suffers, and the Maule is no exception. All of the various float mods reduce directional stability quite a bit, and the airplane feels really loose directionally. The rudder tab still works as it does in the landplane versions, but the objectionable qualities of the tab at high speed seem to be emphasized as directional stability goes down. Ski modifications dont affect directional stability nearly as much as floats, handling almost like the wheel version.
Longitudinal handling qualities didnt vary much as the tail evolved from the round M-4 to the angular tails of the M-5 and later. Elevator forces are light throughout the flight regime, and generally well harmonized with the ailerons. With big loads at aft CG there isnt a whole lot of longitudinal static stability, but the airplane does remain stable as long as you remain within weight and CG limits. Elevator force changes with power can be quite large, specially with the bigger engines such as the Lycoming 235, but still not nearly as large as you might expect to find in a Cessna 182, for instance.
The Maules stall characteristics are excellent: lots of aileron, elevator and rudder control all the way to the stall. However, at light weights and the most forward center of gravity with power off, the airplane can run out of elevator prior to stall. But as with most aircraft, the law of nature that says airplanes with good stall characteristics dont necessarily have good spin characteristics still prevails. The Maule isnt approved for spins.
The short-field capabilities of the Maule can be described as legendary, hair-raising, phenomenal, require a lot of practice, etc. Nothing magic here. The Maules characteristics are dictated by high power loading (lots of power for the amount of weight hauled) and low wing loading (lots of wing area, or lift capability, for the weight).
One of the Maules weaknesses was getting sufficient drag in the landing configuration so that approach angles over obstacles could match the slow-speed short ground roll capabilities available. Various flap angles have been tried and are available as retrofits. Generally speaking, the higher the M-number in the series, the more flap drag there is available.
Low wing loading translates directly to low stall speeds, with corresponding low approach and takeoff speeds. Another law of nature says that the lower the approach speed, the higher the sideslip angle required for a given amount of crosswind. The Maule has a large amount of sideslip capability, but at crosswinds over about 15 knots, youll need to give up some of that slow-speed and short-field capability to be able to maintain sideslip control for landing.
The Maule isnt magic in its short-field capability, but in direct airplane-to-airplane comparisons, its power loading, wing loading and sideslip control make it better than most. The difficulty of flaring out of a steep power-off short-field approach varies as the atmosphere varies. From a slow speed, there isnt a lot of energy or excess lift available to turn the corner and float, so flaring needs to be done precisely at the right altitude, or a hard landing plus bounce will result. Gusty conditions make this harder to judge, as well as randomly robbing you of margin above stall warning speed and flare lift capability. This isnt peculiar to the Maule, but is true of any airplane operated in the 50- to 60-knot range on final with power off.
Groundloops are the big bugaboo of all taildraggers, because the center of gravity of the airplane is behind the main gear. That means the airplane wants to swap ends if it gets a little sideways. The Maule groundloop and gear-collapse rate is pretty big, probably for several reasons: it is used a lot for taildragger training, the normally slow approach speeds and high flap settings that people are accustomed to using in calm air are just plain inappropriate for large crosswinds. Furthermore, we suspect (this is completely unproved and unsubstantiated) that since the Maule is a current production airplane, it is flown by a pilot population of an average age that is quite a bit younger than the other taildragger antiques and classics.
Closer inspection shows that almost all groundloops occur on hard, dry paved runways. This neatly matches theory, which says that any surface that doesnt allow a little sideways slip, like concrete opposed to grass, will help a tail-dragger going a little bit sideways continue on around in a high-speed turn.
But it goes counter to the belief of lots of Maule defenders that the preponderance of the aircrafts landing accidents and groundloops occur in bush operations on bad terrain. Thats not so.
Owners who responded to our request for feedback reported the Maules were generally low-maintenance aircraft, and the factory provided good backup service. Most of the factory people are, literally, family, and theyre pleasant to deal with.
However, there were some areas of concern. One of them was paint. A typical comment: The paint leaves much to be desired-lots of cracking and poorly applied. Another was mufflers. Said one owner: I burn up and crack my exhaust muffs and tailpipes in 500-600 hours. They are cheaply constructed but expensively priced at the factory. One pilot said they cost him $400 each. A third complaint concerned the seats, with reports of both steel frame and fiberglass casing cracking. And another was tailwheel shimmy.
And of course, the fabric covering the fuselage and empennage (the wings are all metal) will have to be replaced after a number of years determined by exposure to the elements, or shelter in a hangar. And new covering is not cheap.
The Maules AD history isnt bad, with only one major type-specific AD in recent history. Its 95-26-18, which calls for inspection and possible replacement of the wing lift struts.
Most mods for small airplanes are intended to give them what the Maule already has: STOL capability. So its no surprise that theres only one notable mod available. Its a good one, though: Micro Aerodynamics makes vortex generators for the airplane, which are in our opinion a no-brainer buy. Wed love to hear from anyone whos had them installed.
For info, theres a Maule newsletter published by Dave Neumeister, 5630 Washington, Lansing, Michigan, 48911-4999. 517 882-8433.
It is a neat little airplane, inexpensive to buy and maintain, and my mechanic loves it because its easy to work on. It has lots of options you can get from the factory without going through a lot of paperwork, such as different doors, swing-out windows, extra lights and fuel tanks, big tires, etc. Its hard to find any other four-seat taildragger thats so economical and versatile.
On the other hand, both of the Maules Ive had (M5-180Cs) have been sloppy-flying airplanes. The controls are light, but not particularly responsive, and there is no feel of real positive control. It flies great when the air is smooth, and the winds are calm, or steady down the runway.
When conditions are less than ideal, landing and takeoffs become quite exciting, which seems a strange characteristics for a so-called bush plane. It runs out of aileron and rudder authority long before you land, and this makes it trickier than you would think a taildragger like this should be.
Ive been mighty anxious when landing Maules in situations that a Pitts or Decathlon or C-152 could handle with ease. (Im a commercial pilot with about 4,500 hours, most of that in taildraggers, mainly Pitts, Decathlons, Citabrias and Great Lakes.)
A high percentage of Maules have been damaged, and I suspect that the poor handling qualities at slow speeds, during takeoffs and landings, are the reason.
The aileron-rudder interconnect makes the airplane squirrelly in cruise. Anytime you put in a hair of right aileron, for instance, you get a hair of right rudder with it, which seems to make the plane hunt all the time. Of course, when landing in a crosswind, the interconnect works against. (For instance, in a left crosswind, you would land with left aileron, left rudder trim, and right rudder.)
I hate the fuel system. My Maule has four tanks, two inboard (main) that hold 20 gals. each, and two outboard (aux) that hold 11.5 gals. each. You can run the engine off the left, right or both mains, and thats fine. The way the aux tanks work, you drain enough fuel out of the mains, and each aux tank has an electric pump that pumps the aux fuel into the mains. This means three things: 1.) For about 2-1/2 hours, until you run enough fuel out of the mains, you have to wallow around in the sky with 70 pounds out on each wingtip, which makes the handling characteristics even more cumbersome. 2). If the electric goes out, or an aux pump fails (both have happened to me), you have up to 23 gals of fuel that you cant use. 3.) You have to pay real close attention to the fuel situation, to keep all the fuel use even. On the plus side, this gives you something to do on long trips.
In my opinion, to improve the airplane 1,000%, Maule should: 1.) Install larger, more effective ailerons and rudders and possibly the elevator as well. 2.) Get rid of the aileron rudder interconnect. 3.) Change the fuel system so you could run the engine directly off any fuel tank. 4.) Market it as a utility airplane rather than a bush plane. 5.) Find somewhat at the factory who can paint. Be all that as it may, I still love Maules!
-Robert A. Sears
We bought this aircraft (a 77 M-235) because it was the most aircraft for the money, and have not been disappointed. Dont expect much help from the flight manual.: only checklist, weight and balance table and emergency procedures. The parts and service manuals reflect the same brevity. Kind of the its your aircraft; you figure it out philosophy. The factory has been very helpful with my questions, and parts are no problem.
Cruise yields an honest 120 knots at 23 squared, 7,000 feet, 12-14 GPH. Maintenance costs have been minimal. Overall, the Maule is a great aircraft, very forgiving, and a joy to fly.
-C. E. Johnson
The Maule does what the factory says it will do. I operate both of my Maules (a MX-7 180 and a MXT-7 180 Tri-gear) off a 2,000-foot strip with trees on one end and a 250-foot hill at the other. The Maule will clear these obstacles with room to spare even on hot days. I have flown a Cessna 172 off the same strip, and it will barely make it.
The only problems I have had with the taildragger are 1.) that I could not stop the Maule tailwheel from shimmying. I replaced the leaf spring, put on a Scott tailwheel. After that, no more problems. 2.) The other problem was the piece of fabric placed between the elevator and tail to eliminate flutter. Every time the elevator moved, the paint would crack, and flake off. On my new Maule I put leading edge tape in this area to fix it. Quality on the Maule is good. Compared to the Pipers and Cessnas I have seen and flown, the Maule is just as good, or better.
-Mark B. Allen
I was hooked on the performance of the Maule from the start. My 85 M-6 on Aqua floats was a strong water performer, but was difficult to land in crosswinds. On land the tailwheel shimmy was annoying.
The most undesirable feature of the Maules is the flimsy door knobs, which work about half the time and are either missing or bent the rest of the time. The best paint jobs on Maules are unfortunately the second or third coat, applied by someone other than the factory.
Anyone considering a Maule as a seaplane ought to go for a checkout in the mud puddle next to the factory. If the puddle doesnt scare you out of float flying, you will be sold on the seaplane performance.
Overall, the Maules are excellent and reliable machines. No frills and plenty of chills (poor heat distribution to rear seats.). After water time in Cubs and SeaBees, I happily return to Maules.
-John A. Dellinger, Director
Lake Superior Research Institute
Also With This Article
Click here to view charts for Resale Values, Payload Compared and Prices Compared.
Click here to view the Maule M-7-235 features guide.
Click here to view “This stuff just doesn’t happen anymore.”.