The Maule M7 is an American-made single-engine conventional gear STOL airplane designed by B.D Maule. This is a primer if you are considering ownership.
The first M-7 took flight in 1984 when they sold for $30,000. Since then, there have been seven variations to the model that currently averages $180,000 for a new aircraft. The M7 seats five including the pilot, has 139 knot top speed and a fuel burn rate of 14 gph.
As a CFII and avgeek, I have long admired the Maule M7 family ever since my wife bought me a scale model of the aircraft for my desk. In fact, I’m sitting next to it whilst I’m writing this article!
Maule M-7 Background
The M-7 evolved from the previous model by Maule Air Inc, the M-4. Built with straight wings and low-wing loading, rugged landing gear assembly, and a high-powered engine, its purpose was to conquer rough terrain and unpaved landing strips while carrying heavy loads.
On the ramp, its outline and features are easily distinguishable from other single-engine high-wing models. Its characteristic dual struts per wing, beefy landing gear, and relatively stubby empennage crowned with a large vertical stabilizer tell a story of high-performance capability.
If the M-7 were a ground vehicle, it would be a dump truck. It is beefy, rough-and-tumble, and sturdy, with raw power to spare. Even the switches and knobs on the panel are bulky in the earlier models, as are the seats. Gunning the throttle for take-off delivers the same message. The M-7’s unique rumble once you advance the throttles feels like a Harley with wings.
The underlying principle of navigating bush country dictates that it be designed with the prop as far away from the ground as possible. That’s the reason behind most bush planes are taildraggers.
The Maule M7 is not just one model of Maule Air’s offering. It is actually a family of planes that includes the original M-7, followed by the M-7-235 and the M-7-235B which were built in 1988 (both were called the Super Rocket), followed by the M-7-235C that came in 1998.
Then came the M-7-260, the 260C Bothe with 260 horsepower. Following this came the Mt-7-235 Tri-Gear. As the name would imply, the Mt-7-235 Tri-Gear was a tricycle landing gear variant of the M-7-235B, sometimes known as the “Super Rocket”.
Finally, Maule Air designed and built the M-7-420 Starcraft Turboprop, the variant with an M-7-235 body but fitted with an Allison 250 turboprop. The slight difference in dimensions comes from the extension of the engine compartment to allow for a constant Center of Gravity (CG) location. This came with 420 shaft horsepower.
Subsequent members of the M-7 family are known as the Maule MX-7. These use an M-6 fuselage with an M-5 wing, whilst using the wingtips, fuel tanks and the operational flaps of the M-7.
Regardless of which model and what minor changes the M-7 underwent as it continued to evolve, the one thing that remained consistent was that it was designed to be used on all terrain year round.
Depending on whether it’s landing/taking off from smooth or rough surfaces, it can be installed with regular or oversized wheels to aid it in its role. If it’s flying into snowy or icy conditions, skis can also be added too.
And the M-7 doesn’t just lend itself to land. Indeed, both factory and after-market alterations allow for the addition of an optional use float set. This float set allows it to be used as a seaplane for amphibious use should the pilot want that.
Some of these float sets can be equipped with a water rudder for added water maneuverability, whilst others can have float/wheel combos so they can be used on both land and water.
Regardless of the variant and landing gear configuration, the lightweight yet durable airframe design allows it to enjoy thrust to weight ratios most other aircraft can only dream of, making it perfect for short take off and landing (STOL).
Aesthetically, the Maule M-7 keeps up with its design philosophy. Looking at it, you can tell that it lacks the refined finishing of more expensive aircraft. From its hardware-store switches on the panel to its functional seat covers to the wrinkles on the metal sheet, not riveted panels, covering the wings the Maule is not known for its refined lines and craftsmanship.
Even the airspeed indicator is not accurate. And this is because of the location of the static port on the front cowling. Altimeter readings are also not precise and anyone who flies a Maule already knows this and builds a fudge factor into all their settings and calculations.
The factory installed power system is also second to none. Whilst the power system of many of the original rivals from the 1980s are failing due to their age, the power system on the M-7 was designed for longevity and many original models can still be found with their original systems installed (though some modifications do require it to be replaced or upgraded).
Aerodynamically, the M-7 is as straightforward as it gets. The wing is a truly rectangular structure, offering no tapering or thinning. While its rectangular form factor may suggest a lack of refinement, there is a functional purpose behind it. Truly rectangular wing shapes alter the progression of a stall across the wing.
By making sure the Maule’s wing stalled at the root first, they ensured that the ailerons would remain effective and not escalate into a spin. The large vertical fin and short moment arm from the CG to the aerodynamic center of the vertical tail also necessitated a larger tail.
Aside from the FAA-mandated LED lights pilots use for visual detection, other exterior features include vortex generators installed on the wingtips, which are there to help with fuel efficiency.
While Maule may not be that detail oriented when it comes to the exterior, the interior detail is exquisite. The M7 features crystal clear cabin windows which are a delight for pilots and passengers alike!
Maule M-7 Specifications
The Maule M-7 is a marvel of aeronautical engineering. Not bad for something a guy sat in a quiet country corner developing while America geared up for speed above all else! Indeed, it has renowned STOL capability and offers outstanding slow flight performance. It is just as comfortable hauling cargo as it is hauling passengers, making it a favorite all round.
Maule M7 Flight Characteristics
The most forward CG location on the Maule is just behind the main gear and about a foot aft of the leading edge of the wing. A rear center of gravity has two pronounced effects on the flight characteristics of the Maule M-7.
The first is that it makes the M-7 inherently less stable. This is not a bad thing. It just means that you can be lazy when you’re at the controls. The second is that it reduces its drag considerably by having dual lifting surfaces. When the CG is forward, the tail has to have a downforce to keep the nose up. When the CG is moved behind the center of life, the tail has to push up to keep the plane level.
With dial lifting surfaces the M-7’s wing generates less induced drag and the same thrust from the M7’s powerful generates more forward speed, resulting in better fuel burn, range, and endurance.
One point to note though is that if you have not flown a taildragger before, much less a high-performance tail dragger, then it would be a good idea to have a good tailwheel instructor take you up and run through all the maneuvers until you get a visceral feel for the different flight characteristics of a high powered tailwheel plane.
One of the things you will notice in your research of the Mauls is that there are quite a few accident reports. Don’t let that scare you away from this solid-built tank of a plane. The M-7 is harder to handle than a typical docile high-wing plane that was built intentionally for low-time pilots, or for training. The Maule is not built for that and can be unforgiving.
Also, a lot of the accidents and incidents you will find happen predominantly in the bush when pilots go too far in pushing the M-7’s weight and balance envelope. They get overly confident of how much the plane can carry and exceed its aerodynamic capability.
The other thing you have to remember is that the M-7, as you have now seen, comes in a total of seven variants, one of which is a turboprop. While the characteristics of flight for both are surprisingly similar, the way you need to manage power is a little different.
While it is not necessary to acquire a type rating for turboprops, it is necessary that you understand its powers and limitations. Or else you could wreck the powerplant the first time you start up. It is also necessary to understand high-altitude flying and be prepared to supplement your flight with oxygen since the M7 can easily attain 20,000 feet.
Even if you don’t need a high-altitude endorsement in your logbook to fly the M07 turboprop, you should still go through ground school and understand the symptoms of high-altitude flight.
The turboprop version has so much excess horsepower, generating 430 shaft horsepower at sea level, it does not need full throttle at take-off. The Maule M-7-420 has a power loading of 5.8. To contrast this, a Pilatus PC-12 has a power loading of 8.5 but has an MTOW that is more than 4 times the M-7.
Maule M-7 Price
With seven variants, the M-7 differs widely in price. The fact that there is also a turboprop in its ranks, skews the average price considerably.
A brand new M-7 from the factory now is $299,000 while a turboprop exceeds $600,000 for ones coming off the factory floor. It is still one of the least expensive planes you will be able to find that can be classified as a workhorse.
What doesn’t figure into the calculations is that the M-7 is not a sensitive plane, speaking from a maintenance standpoint. It doesn’t need to be put in the shop too often, and wonders are quick to note that, aside from the scheduled maintenance that is mandatory, there is hardly any need to head to the nearest A&P.
That was not by accident. It was the way BD Maule wanted the M7 to be. As far away from fancy and as close to zero maintenance as was practical.
Prices in the secondary market are erratic at best. I’ve found Maule’s from 1990 for under $20,000 without the need for much work, other than an Annual and an overhaul around the corner. I’ve also seen good-condition, amphibious M-7-235C models for $268,000. I’ve even come across close to pristine M-7 turboprops for just under half a million dollars.
What I have learned in M-7 shopping is to never go by the advertised price from a distance. It’s always best to have a mechanic by your side and determine how good the rigging is, look at the books, and take it for a test flight if the owner will let you. If it's straight and true, tight, and sounds burly, you’re in the ballpark.
Whenever it comes to planes that work hard in the bush, it's always best to be thorough and know what you are getting into. You don’t need to be looking for a mint-condition M-7, but you should know the extent of what to expect.
The cost to operate the M-7, whether it is the original or one of the other variants does not differ widely. Except, of course, if we are talking about the turboprop. The only thing you have to be aware of is the high premiums you will face for owning a taildragger, and since Maules are prone to accidents because of overconfident pilots, there is an added actuarial cost that insurance premiums will reflect.
Insurance premiums are based also on hull value and are determined by the insurer in most cases. Just because a new owner dumps a large sum into upgrades and modifications does not mean that the insurance company will be willing to insure more than what they believe the replacement cost for the original M-7 would be.
For this reason, a $200,000 M-7 currently has premiums in the $4,000 range. That is almost four times the amount on a typical high-wing plane.
The M-7 turboprop easily doubles that, with a $400,000 aircraft demanding between $8,000 to $10,000 in annual premiums.
The assumption as I proceed to review direct and fixed costs here is that you plan to buy it for personal use and that you are not renting it out. In this case, you save on having to do 100-hour inspections. You also will save on the insurance premium and most likely, the hourly fuel burn.
Direct Operating Cost
The largest line item in operating costs that is directly impacted by use is fuel.
Running the M7 up at 7,000 feet and setting the power to 75% will burn 13 gallons per hour. Takeoff and climb to 7,000 feet consume approximately 4 gallons and need about 10 minutes. The first hour averages 11 gallons for 50 minutes at cruise plus 4 gallons for the climb which is 15 gallons for the first hour. The second hour is 13 gallons at that power setting.
If you regularly use 3 hours at a time, 14 gallons per hour is a good average to use as your fuel cost. At my airport, I pay $7.60 per gallon which translates to $106.4 per hour.
Another cost that you should add is engine oil. Engine oils burn differently in different engines and with different flying styles, and of course maintenance levels. On average, pilots report that the 235C burns about 2 quarts every 5 hours of flight. At $10 per quart, that works out to be $4 per hour of flight.
This works out to be $110.40 per hour.
Fixed costs are any costs that you will incur regardless of use. So even if you just left your plane in the hangar, there are some costs that will go on adding up. These are specifically, the price of an annual, the premium for insurance, and hangar costs.
For the sake of simplicity, I also add any incidental maintenance costs here since they are not strictly incurred based on hourly flight. In this category, I look at unscheduled maintenance, for instance.
Surveying Maule pilots, they report that the average unscheduled maintenance expense for M-7s is around $1200 per year. Assuming you fly 400 hours a year, that works out to be $30 per hour that you should set aside for maintenance costs.
The largest cost that is best to tackle upfront is the future cost of an overhaul. If you purchase a plane that’s midway to its overhaul just divide the rest of the hours with the cost of the overhaul.
An overhaul for a typical Lycoming 0-540 is $50,000. The engine also has a TBO - time between overhauls - of 1800 hours. While you don’t incur the cost right away, it is best to set aside an overhaul fund of $50,000/1800 hours which is $27.7 per hour.
Thankfully, the M7 offers easy access to most of the key features an aircraft mechanic would need to inspect or fix, like the firewall and flight battery, meaning even difficult maintenance jobs on the M7 are much easier than on rival planes, further enhancing its reputation as what some have called a full size marvel (in reference to the many small, scale models of the M7 somewhat jokingly referred to by some as “marvels”).
Using 400 hours per year as a benchmark, I can break down all other costs and get a good idea of how much it costs me every time I go up.
Insurance, as we said, is $4,000 a year. Flying it at an average of 400 a year means I should set aside $10 for insurance for every hour I fly.
An M-7’s annual is about $1,000, or $5 per hour.
Add to that the cost of a T-hangar which typically runs about $300 a month, giving you an annual cost of $3,600. Divide that into 400 hours and you get $9 per hour.
The total Fixed costs that you would incur in one year, excluding your monthly payments on a loan, if you took one out, would be $30 for unscheduled maintenance, $27.7 for the overhaul fund, $10 for insurance, $5 for the annual, and $9 for the hangar. These total up to $81.7 per hour.
Adding that to the Direct Operating Cost we calculated earlier of $110.40 per hour, it should cost you a total of $192.10 per hour to operate the M7.
Keep in mind that this is for the piston models and not the turboprop. Operating costs for the turboprop models are significantly higher given their high fuel consumption and better performance.
Maule M-7 Speed
The main thing you need to know about speeds in a Maule M-7 is that they are highly inaccurate. It’s a thing among Maule M-7 pilots that they know to add a few knots or subtract them based on the condition and attitude of flight.
The main problem, as mentioned a little earlier, is related to the static port and where it is located. If you remember your early ground school days, your airspeed is derived from the difference between the total pressure collected from the pitot tube and the static pressure collected from the static port.
When there is a discrepancy in the static port it affects a number of your instruments, most importantly your airspeed indicator and your altimeter. But most Maule pilots account for this and can tell where they need to be on approach, or in climb after take off.
You still need to refer to the published speeds and the arcs on your airspeed indicator, and it's always best to commit them to memory.
All the M-7 models, even the turboprop version, have similar speeds and similar handling characteristics.
The key speed you have to get to know is your stall speed and the best way to do that is to practice them as many times as you can with an instructor before you finally fly the M-7 solo.
Approach speed in an M-7 should be five knots above stall in landing configuration with power still coming from the powerplant, albeit a little above idle. That extra power gives your elevator the needed effectiveness when you come into ground effect, or else it's going to be mushy.
Aim to touch down after the stall horn comes on. Wheel landings on the M-7 are not easy and require lots of practice, but three-point landings are easy to master if you remember stall+5, crossing the threshold with full flaps.
The one thing peculiar about this plane is that it has something called negative flaps. It is meant for cruise flights when the flaps are set at negative 7 degrees. In a climb, they are set to 0.
Maule M-7 Fuel Burn
The M-7 is typically flown between 7,000 and 10,000 feet. It seems to offer the best combination of factors depending on the load being carried.
At those altitudes, fuel burn at a 75%-power setting will be 13 gallons per hour. Fuel burn with 65% power will be 12.5 gph.
The M-7 has an 84-gallon fuel tank and flies at 120 knots true airspeed at the 75 % power setting at 7,000 feet.
If you haven’t worked it out yet, the M-7 was designed to be a mixture of high-spec performance and fuel efficiency.
About THE AUTHOR
After spending years watching every video I could find about flying, I finally scratched the itch and got my pilots license. Now I fly every chance I get, and share the information I learn, here.Read More About Joe Haygood