|Aircraft Evaluation Report
Test Pilot - Flying the M20F
Ed. Note: This article is the third in a series of evaluation reports on the various Mooney models owned by MAPA’s membership. Our first report was for the M20C, the second for the M20E. Both of these “original Mooneys” proved to be great airplanes, but with one major shortcoming - the lack of room for the rear seat passengers. The C and E are very nice two-place airplanes with lots of baggage space. But with rear seat passengers on board, the C and E models leave a lot to be desired in the area of cabin comfort. Mooney realized this and in 1967 released the first airplane with really enough room inside for four - the M20F. Combining the 200 horsepower Lycoming IO-360-A1A from the M20E with a fuselage stretched 10 inches (5 of which are in the rear seat legroom area) gave the Mooney factory an airplane they could truly market as a useable four-place airplane.
So for this third in a series of pilot reports, let’s take a look at a representative M20F loaned to MAPA by All American Aircraft. We’ll apply some basic flight test procedures to determine the real world performance of the airplane and take a look at the design and its compromises with a “hard nosed” attitude. Our goal here is not to make the airplane and the design appear perfect - there is no “perfect” airplane. So, pros and cons both considered, let’s go out and fly our representative M20F to see what it will do.
For these series of reports, we have tried to bring you honest, real world performance and opinions on the various Mooney models our association represents. We pulled no punches with the C and E models flown earlier. Now let’s apply those same hard nosed, real world evaluation techniques to the M20F. Using some basic flight test principles and procedures, we will take a look at honest climb and cruise performance on our test M20F.
Right up front, let’s discuss the number one reason to chose an F model over an E model - cabin space. An E model will do everything an F model will - same engine, same aerodynamics, same wing. The only difference between the two is that the F model has a ten inch stretch in the fuselage compared the E model. That doesn’t sound like much, but when it comes to the F model, size does matter. Those ten inches of fuselage stretch make a huge difference in comfort for the rear seat passengers. Five inches of the stretch are directly applied to the rear seat legroom area. If you don’t think this sounds like much, go sit in an E model and then go sit in an F model. We did and the accompanying photos show the difference. Impressive.
|These two photos show the improvement in rear seat room between the short body C and E models (left) and the F model (right). David McGee of All American Aircraft sits in the pilot's seat while Leo Sarinana of Lone Star Aviation (who is 5'6") sits in the back. Imagine how uncomfortable a 6-footer would be in the backseat.|
First, we had to find a nice, nearly stock F model to evaluate. All American Aircraft here in San Antonio again came to our rescue. They always carry excellent pre-owned Mooneys in their extensive inventory. They happened to have a very nice, nearly stock 1967 model M20F setting on the showroom floor. N353JT, M20F serial number 67-0353, was about as close as possible to a stock M20F as you’ll find today, with the exception of a cowling inlet closure installed several years ago. This airplane had 3900 hours total time and only 435 hours on the IO-360-A1A engine. Avionics were useable and the airplane had the electric gear option installed at the factory way back in 1967.
The only non-stock item on the airplane was the installation of a cowling closure to eliminate some of the excess inlet area seen on all pre-J model cowlings. I really like these cowl closures. I’m not sure if they improve cruise performance or engine cooling, but they sure make the front end of the airplane look better. Short of installing a J model cowling (expensive), cowling inlet closures are the next best choice for improving the looks of a pre-J model Mooney without breaking the bank. The photos show just how much an improvement they are over the stock cowling.
Walking around our test M20F reveals a standard Mooney airframe configuration. Simple and strong. Low maintenance. Superb wing. One thing you’ll notice is the amount of fuel carried in the M20F. The F model carries 64 gallons of fuel compared to 52 gallons in the M20E. This adds another hour of endurance over the E model, making the M20F one of the best of all Mooneys in that department. Count on the F model being a solid 4hr 30min airplane with at least another hour in the tanks for reserve with full fuel. Even compared to today’s airplanes, that’s excellent range and endurance.
|The installation of a cowling closure on our test airplane really improved the looks up front (left). Compare that to a standard cowl (right).|
Another nice change with the F model is an increase in maximum allowable gross weight compared to the E model. The F is a 2740 lb airplane - the E model is 2575 lbs. That’s a 165 pound advantage for the F model. Since the F model’s empty weight is only about 15 pounds heavier than an E model, that translates into a 150 lb increase in useful load over an E. But the 12 extra gallons of full fuel in the F subtracts 72 lbs from that. So, in reality, the F model has a 78 pound increase in useful load over an E model when both airplanes have the tanks full or a 150 lb increase when filled to 52 gallons.
Externally, the F model looks a little better balanced with the 10” stretch in the fuselage and the third window on the side. Whereas the C and E appear short and stubby to some, the F model gives a better look on the ramp. I asked several non-flying friends to comment on the appearance of the C, E and F for a different “ramp appeal” perspective. The F model won the contest every time.
Up front, we come across another pre-J model cowling to content with. I won’t harp anymore on the difficulty in pre-flighting the engine with the cowling design on early Mooneys. I think I’ve beat that subject to death in the articles on the C and E models. At least our test F model had “quick turn” fasteners installed around the upper cowling half instead of sheet metal screws. Even so, a screwdriver was required to do a basic oil level check. Removing and reinstalling the upper cowling, even with the quick turn fasteners, proved to be a 20 minute job. Looking at your engine and accessories before flying shouldn’t be this difficult. And as our airplanes age, looking underneath the cowling often becomes very important to our well being and safety.
Except for the stretched fuselage and the extra window on the side, the C, E and F models are really about the same on the outside. But it’s a whole different story when you open the cabin door and look inside. With the F model, we have a realistic four-place Mooney. If you’re going to carry four people in your airplane often, buy an F model over a C or E. There is no comparison in comfort with three or four people on board - the F model wins hands down.
Seated in our favorite chair (the forward, left one), let’s settle in and look around. N353JT did not have shoulder harnesses. That instrument panel is awfully close to your face. In even a minor accident, you’re going to pivot around the lap belt and your head is going to hit the panel. I know that’s not a pleasant thought, but please think about installing shoulder harnesses for the front seats. Lake Aero Styling in California has them (1-800-954-5619). This modification to your older Mooney could be one of the most important from a safety standpoint.
|Our test M20F had the full length rudder configuration, standard beginning in '67 with the F model.|
A scan of the panel in our test airplane shows another pre-1969 instrument arrangement. This means that everything is spread haphazardly from one side of the panel to the other. The basic-T arrangement didn’t come until 1969, so expect any pre’69 airplane to have instrumentation spread out all over the place. On 353JT, the panel in front of the pilot contained all the essential flight instruments, in no particular order. This makes basic airplane control in IFR conditions a challenge until you get comfortable with the panel layout. The center and right side of the panel contained the avionics and engine instruments. The manifold/fuel pressure gage was located on the far right side of the panel, almost impossible to read.
The 10' stretch in the cabin makes a big improvement in the looks at the M20F (tleft) compared to their M20C and E (right).
Ergonomics and panel design in personal airplanes have come a long way since 1967. If you fly a lot of IFR in your pre’69 Mooney, an updated panel instrument panel will add logic and consistency to your IFR flying. Otherwise, be prepared to do a lot of head moving and neck straining, neither being a good idea when flying in clouds.
After my difficulties in starting the engine in the E model for last month’s article, I kind of dreaded starting the exact same engine in our test airplane. But I was pleasantly surprised. Don’t ask me why, but the problems I had starting the E model were not present in the F. Hot or cold, the IO-360-A1A engine started quickly and easily in N353JT. The E model was difficult for me to get started. The F was easy. If the two airplanes I flew are representative of the fleet, the F model wins the engine start contest with ease.
After engine start, I leaned the mixture out aggressively for smooth and clean engine operation on the ground. You should do this with any Mooney. Most engines are set up too rich at or near idle. Aggressive leaning will make the engine run smoother and will keep the spark plugs much cleaner. Most spark plug fouling occurs during ground operations with a too rich mixture. You can remedy this by simply leaning the mixture after engine start for all ground operations. We always wanted to put this procedure in the POH while I was flying engineering flight test at the factory, but we were concerned that too many pilots would forget to enrichen the mixture before rolling onto the runway for takeoff. But do it anyway - your engine will run much smoother and cleaner on the ground. Just don’t forget to enrichen prior to takeoff.
|A look at the F model cowling. A screwdriver is required for even a basic oil level check.|
While taxiing to the runway (with the mixture leaned), another early Mooney characteristic becomes obvious. One thing our early Mooneys aren’t - smooth on the ground. The ride to the runway in N353JT was a rough one. Minor bumps on the taxiway were transmitted through the gear into the airframe and you could feel every one in the seat. Maybe this airplane had rubber biscuits that needed replacing (see Don Maxwell’s article in this issue on how to replace them), but for whatever reason, N353JT rode like a wagon on the ground. This isn’t a big deal, unless you plan on operating from unimproved or grass runways a lot of the time. A Mooney isn’t the best airplane for these kinds of operations.
Runup and preflight checklist complete (don’t forget that mixture control prior to takeoff) and it’s on the runway for takeoff. Of all the Mooneys I’ve flown, the E model has absolutely the best runway acceleration and shortest takeoff distance of all - it’s light weight and 200 horsepower results in an airplane that really gets with the program from 0 to 80 knots. The second best is the F model. N353JT really scooted out. Not at a breathtaking rate, but as good as any Mooney made today. As with all Mooneys, a little pull on the wheel (about 5 pounds aft) during the takeoff roll resulted in a really nice feel as the airplane accelerated. Takeoff distances averaged around 900 feet at our weight (full fuel, single pilot, 20 lbs of gear, 1200 ft density altitude).
Positive rate of climb established and it’s time to raise the gear. N353JT has the electric gear option that the factory began installing as an option in 1966 and made standard in 1969. Gear switch up and - wham! This has got to be the fastest gear retraction system in the world. It really took me by surprise. I always thought that late model Mooneys had fast gears, but the system in N353JT was just unbelievable. Maybe 2 seconds or so, but that’s all it took from the time the gear switch was placed in the up position until the gear was in the wells. Same for gear down. And there was no mistaking if the gear had come up or gone down. You could feel it in the floorboard and seat. Pow! - gear up. Wham! - gear down. Bill Wheat at Mooney said that this rather violent gear operation is a characteristic of the Dukes actuator installed in the early Mooneys. I guess it’s okay, but it makes you wonder how the structure and the linkages can take these kinds of up and down loads. We’ve never heard a report of anything breaking in the system, but this has to be the most violent gear retraction system in the general aviation fleet.
|The panel from the pilot's perspective. The haphazard layout makes for difficult IFR operations until becoming familiar with the instrument locations.|
Out to the flight test area and let’s look at some climb performance data. As we did with the C and E models, we performed two continuous climbs from 1500 feet to 10,000. We climbed in the most efficient manner in any normally aspirated Mooney - full throttle, max RPM (2700 for the F model), mixture leaned to 100 degrees rich of peak EGT, cowl flaps full open and airspeed higher than Vy. Forget the old “25 squared” idea. You loose climb performance and get nothing in return.
Concerning airspeeds, we used two for the continuous climb tests. They were 100MIAS and 120MIAS, same as we did for the C and E models. Loading was full fuel (64 gallons), a single pilot (me) and about 20 pounds of gear. Here is the observed data obtained on our test M20F airplane:
Continuous Climb Data 1967 M20F N353JT Full throttle, 2700 rpm, mixture leaned to 100 degrees rich of peak, cowl flaps full open, airspeed as noted, ram air off
Climb #1 Airspeed at Constant 100 MIAS
|Climb #2 Airspeed at Constant 120 MIAS|
Let’s compare this data to that we obtained for the C and E model. Keep in mind that this data for the F model was obtained on a day a little bit cooler than the days when we flew the C and E models, so it will show a little bit better performance. Nevertheless, let’s compare the climb data for the C, E and F and see what we get:
Climb Performance Comparisons M20C, M20E and M20F
So our data shows the M20E remains the champ in the climb performance category of all the pre-J model Mooneys flown to date. That figures - the E has a short fuselage, light weight and 200 horsepower. The F model has the same horsepower, but in a longer, heavier fuselage with 12 more gallons of fuel when full. The C model trails both the E and F in climb performance, but that is to be expected with 20 less horsepower. But isn’t it interesting to note that all three airplanes do very well in the climb category. It’s pretty awesome to be able to average these rates of climb with the relatively small horsepower engines we fly behind. Don’t look for too many other 180 to 200 horsepower airplanes to even come close to these numbers. They can’t.
Don’t put too much emphasis on the engine temperature data. This data came from each aircraft’s cluster gage instrumentation, which is notoriously inaccurate. These gages are approaching 33-35 years in age and can’t be relied on for accurate temperature readings - only trends. Especially out of line are the oil temperature readings for the E model. I suspect that the oil temp gage in our test E model was way off.
One final word on the climb performance tests. The data obtained for the E and F model was obtained with the ram air control off. With ram air on, probably another 15-20 FPM rate of climb could have been available. But I just hate running an engine using unfiltered induction air and I won’t do it while climbing in dirty air at lower altitudes
Now let’s look at cruise speeds in the F model and compare it with the C and E. Again, we set the cruise power in the F identical to the C and E models. That’s full throttle, 2500 RPM, mixture leaned to 50 degrees rich of peak, cowl flaps closed. As I said in the previous two articles on the C and E, if you want to run your normally aspirated Mooney in the most efficient manner, use this power setting at all altitudes, regardless of OAT. There are technical reasons for this. Full throttle is where the induction and exhaust systems were designed for the most efficiency. 2500 RPM gives excellent propeller efficiency and thrust at the speeds we fly. 50 degrees rich of peak EGT is a perfect compromise between best power (100 degrees rich of peak EGT) and best economy (peak EGT). And the cowl flaps should be closed in cruise at all times.
I did obtain cruise data with the F model with the ram air both off and on. Opening the ram air door does add about 1” manifold pressure and 10 horsepower when activated. As I mentioned in the article on the E model, the ram air idea was and still is a bad one. Mooney’s primary induction system on the early airplanes was a bad one. Loosing 1” of manifold pressure through the primary induction system is an unacceptable design and the ram air bypass is simply a bandaid for this poor design. Regardless, here are the numbers obtained with the F model in level cruise flight.
Level Flight Cruise Performance 1967 M20F N353JT
Full throttle, 2500 rpm, 50 degrees rich of peak, cowl flaps closed
Average GS/TAS (ram air on): 145.25 kts
Average GS/TAS (ram air off): 144.00 kts
Average GS/TAS (ram air on): 150.5 kts
Average GS/TAS (ram air off): 147.00 kts
Average GS/TAS (ram air on): 151.25 kts
Average GS/TAS (ram air off): 148.00 kts
So there we have it - GPS derived true airspeed data for our test M20F. N353JT had accumulated a lot of antennas over the years, but all things considered I think the airplane was a good sample airplane for our performance runs.
We used the four-way GPS speed run method to determine true airspeeds. That procedure is to set the cruise power setting you want to check and fly N,E,W,and S headings on the compass (DG). Don’t correct for any wind - simply fly the four cardinal headings on the DG. Hold airspeed and altitude very accurately. Note the stabilized GPS groundspeed on each heading and write it down. Add those four groundspeeds, divide by four and the result is the aircraft’s true airspeed for the altitude and power setting you are flying. And it’s very accurate - as good as any test pilot can do flying over a speed course.
|N353JT had lots of external antennas that probably slowed it down a few knots.|
Using the cruise speed data we obtained for the C and E models previously, let’s take a look and see how the F model compares:
Comparative Cruise Speeds M20C, M20E, M20F
Level flight, full throttle, 2500 RPM, 50 degrees rich of peak EGT, cowl flaps closed
|Altitude||Ram Air||GPS Derived Cruise Speed KTAS|
Interesting, isn’t it? When it’s all said and done, these three airplanes are separated by a maximum of 10 knots or so (7000’). The difference is even less at 4500 feet and 10000 feet. The 180 horsepower C model holds its own against the 200 horsepower E and F. Certainly the E and F are faster, but not by that much. Between the E and F, the E is still the speed champ. The short fuselage and the 200 horsepower engine give the fastest configuration of all three. But the F model is within a couple of knots of an E, and two knots is insignificant. So you don’t give up any real speed moving up to an F, but you gain lots of cabin volume and rear seat legroom. Sounds like a pretty good deal to me.
Handling quality wise, the F flies just about like the C and E. I don’t think the average pilot could tell the three apart with his eyes closed. They all fly similar. Don’t expect really high roll rates in either airplane, but who needs them in the type of flying we do. But the control harmony is good in pitch, roll and yaw - controllability about all three axes seem to have about the same force/response characteristics. Push/pull tubes generally result in a tighter control system than a pulley and cable one. That’s why Mooneys feel so much better than a Cessna or Piper - control “slop” in a Mooney is much less. But Beeches are different - Bonanzas have a superior design in their cable/pulley system. Bonanzas handle the best. But Mooneys are a close second.
With our speed runs completed, it’s time to descend for some stall speed and characteristic checks. Hurray! Our test M20F has a top of the green arc on the airspeed indicator at 175 MPH, standard for that model since its inception in 1967. The C and E models we flew were stuck with a top of the green arc of 150 MPH (increased to 175 MIAS for the 1969 model year). Too much flying in pre’69 C and E models is done with indicated airspeeds well into the yellow arc. Not so in the F models - our test F model was comfortably descended with airspeed readings always in the green. All Mooneys are strong and flying a pre’69 in the yellow arc is not going to hurt anything. But there is something about descending in rough air with the airspeed well into the yellow arc that is unsettling. I enjoyed the ride down from altitude in the F model with airspeeds in the green rather than the yellow.
Stall speeds in our test F model were almost identical to those in the E. Clean and idle power, the stall break occurred at 64 MIAS in the F (compared to 67 MIAS in the E, but I suspect indicator error). Dirty, the stall break occurred at 60 MIAS in the F (61 MIAS in the E). Characteristics at the stall were benign and docile. Relaxing back pressure immediately unstalls the wing. A little nose down to regain speed and the airplane can be returned to level flight with an altitude loss not exceeding 200 feet. Whoever started the rumor many years ago that Mooneys have rather harsh stall characteristics was just wrong. You might get a wing drop (less than 15 degrees) in a Mooney and it’s important to keep the ball centered with the rudder during the entry and stall, but a Mooney is just a docile stalling airplane. It’s not a fat winged Cessna with indicated stall speeds in the 50’s, but any pilot who describes a Mooney as having “scary” stall characteristics just isn’t doing them properly (or is bragging).
|N353JT had the "twisted" wing seen on '67 F and G models. It did nothing for the airplane's stall characteristics and was dropped in '68.|
Using our rule of setting threshold approach speeds at 1.2 times the stall speed, I tried several approaches using threshold speeds of 77 MIAS (1.2 x 64) with the flaps up and 72 MIAS (1.2 x 60) with the flaps down. Surprise - the F model felt a little mushy during the flare using these threshold speeds, which were within a few knots of those used for the C and E. I had enough airspeed and energy left to adequately flare and land, but I didn’t feel like I had a comfortable airspeed and energy “cushion” using these speeds like I did in the C and E models. So I tried using 80 MIAS as a threshold speed with the flaps full down in the F model and things felt much better. Even with a pretty strong crosswind, 80 MIAS over the threshold in the landing configuration felt perfect. So with the F model, I think you might try a threshold speed of 80 MIAS for normal landings with the flaps down - you will probably feel more comfortable at 80 MIAS.
I must pause here and talk a little bit about our number one accident/incident area in the MAPA community. We’re having way too many landing overshoots and prop strikes these days. Every one of these incidents involves excessive airspeed during the landing flare (I’m hearing numbers like 100-120MIAS!). These accidents and incidents are really expensive, since they usually involve an engine teardown and rebuild. As a result, everyone is paying much higher insurance premiums.
So on your next flight when you don’t have anything to do, climb up to a safe altitude and perform a flaps up and a flaps down stall with the gear down. And stall the airplane properly - trim to 80 MIAS power off, decelerate slowly with increasing aft stick pressure using a 1 mph/second deceleration rate and note the indicated airspeed at the stall break. Write those two stall speeds down. Multiply them times 1.2 or 1.3. If you like to land with the flaps up, use 1.2 or 1.3 times your flaps up stall speed as your threshold speed. If you land flaps full down, use 1.2 or 1.3 times your flaps down stall speed as your threshold speed. I am confident your airplane will give you a much better feel during the landing flare, your brakes will last a lot longer and your landing distances will be less than the runway you are landing on - always a good thing.
And remember, we’re talking threshold speeds, not pattern speeds. I personally like to fly the pattern in a pre-J Mooney at 100 MIAS or so. At busy airports, this can even be 120 MIAS. But I always shoot for 1.2 or 1.3 Vso as a target speed as I fly over the end of the runway. Anything faster in a Mooney and my landing distance will double or even triple. Even worse, I might get into a float a few feet above the runway because of the extra speed, see the end of the runway approaching and then try to force the airplane to land by pushing the wheel forward. At least, that will result in a terrible landing. At worse, it will result in a series of bad bounces which ends up with the nosewheel striking the ground in such a nose low condition that the prop strikes the pavement. Ouch - that’s a $25,000 repair bill and 3 months downtime waiting on the rebuilt engine.
So that’s a look at the climb and cruise performance of the M20F and some of its characteristics and handling qualities. So, after flying the C, E and F, what does it all boil down to? Which is the best?
The C model is probably the best value, giving the most performance and capability for the least money. But carburetor ice and a small cabin are its two main drawbacks. The E model has proven to be the performance champ. But it too has the small cabin and a fuel- injected engine that eliminated the carb ice issue but is difficult to start hot. The F model is the cabin comfort champ. It gives up very little performance to the E model, has an hour extra endurance and more useful load than either the C or E. And its injected engine seems easier to start than the E model.
If your flying is mainly VFR or light IFR and you don’t carry more than two people in the airplane, buy a C model. If your flying includes a lot of IFR, you’re flying in conditions where takeoff and climb performance is important and you mainly fly with two people on board, the E model is the better choice. But if you plan on flying with three or more in the airplane more than just occasionally, the F model is the best. The F gives you a reasonably comfortable four-place airplane with performance almost matching the shorter E model. Overall, it has to be judged the winner.
Prices for F model Mooneys continue to skyrocket. Our test airplane, N353JT, is a good example of current prices for F models. Good paint, useable interior, below average avionics, good engine and airframe times. This airplane is priced at $63,500 and worth every penny.
Our next airplane to evaluate is the M20J. The J model was the next version of the M20F, incorporating several aerodynamic and system improvements resulting on one of the all-time lightplane success stories. But an M20F will do 90% of what an M20J will for $30,000 to $50,000 less initial purchase price. That’s a hard deal to beat and what makes the M20F such a sought after airplane.
The M20F isn’t the perfect airplane. But it comes pretty darn close.