Blue Side Up

As I’ve written about before, I started my training in Diamond DA20s and later transitioned to the Cessna 172 after I switched flight schools. At the time, I had no other experience in any other aircraft so I couldn’t write a valid comparison between the two. Now however, I have about 60 hours in the DA20 and a little over 40 hours in the 172, so I feel I’m now allowed to express my opinion and provide a brief look at some of the differences. Take note that the 172s that I fly were both made in the late 1970s, so my comments are strictly related to these models and not the newer models.

The C172 is the most popular training aircraft in the world, hands down. First introduced in the mid 1950s, over 43,000 have been produced according to wikipedia. For this reason, I’m going to assume that the DA20 is the least known aircraft in this comparison, so I’ll be focusing more on it’s characteristics compared to the 172’s. So let’s get started.

The first big difference you’ll notice about the DA20 is that it’s made from carbon fibre and glass fibre, not metal. The Diamond POH (Pilot’s Operating Handbook) calls the material Carbon Fibre Reinforced Plastic (CFRP) and Glass Fibre Reinforced Plastic (GFRP). From a pilot’s perspective, I love the carbon fibre. The approximate empty weight of the DA20 is 1,153 lbs compared to the 172 which weighs in at around 1,530 lbs, depending on equipment installed. A two seater will obviously weigh less than a four seater, but the reduction in weight is definitely beneficial for a number of reasons (fuel consumption, maneuverability, etc.)

The second thing you’ll notice right away is that the DA20 is a low-wing aircraft while the 172 is a high-wing aircraft. In fact, you’ll probably notice by the end of this post that pretty much every design option is opposite between the two airplanes. There are certain advantages and disadvantages to both wing designs. Visibility is a big one. Low wing, combined with a bubble canopy on the DA20 gives you great upper visibility but seeing the ground or traffic at your 3 o’clock and 9 o’clock low positions is tough. Conversely, the same statement applies for the 172 at positions above to your left and right. It’s much easier to inspect the wing and landing gear in a high wing aircraft as well; with the DA20, you have to get down on your hands and knees to see everything. The big factor in the high vs low wing debate for me is handling characteristics. I find the DA20 to be a little more responsive and snappier than the high wing Cessna. Don’t get me wrong… the 172 is a very stable airplane, but when it comes to having a little fun or making quicker maneuverable turns, the DA20 wins.

Maneuverability usually comes with a cost though. Just as most fighters are design to be inherently unstable, the low wing is inherently a bit less stable than the high wing in this case. Where you’ll really notice the difference is on the ground during your takeoff roll. I’ve noticed the DA20 is a bit edgier throughout the yaw axis while taking off, so good rudder control is important. The 172 is a bit more relaxed and doesn’t tend to swing about as much. It’s not so much of a hindrance as it is something you have to get used to. In the air, the DA20 has a quicker roll-rate than the 172 I’ve found, but this can also be attributed to the smaller size and lighter weight. It’s the same thing you encounter in a car: lighter two seater vs a four seater sedan. The two seater will win in the turns but the sedan usually has a higher top speed. I’ll get to the speed bit later. Oh, and the DA20 is way more fun to spin than the 172!

Moving on from the wings, the empennage (tail section) is different as well. The DA20 has a high T-tail while the 172 has a conventional low tail. Again, both have their own advantages and disadvantages which I’m not going to comment on.

Let’s move from outside to inside the aircraft. Again, we’ll see that the design choices made here tend to be a little different. The DA20 uses a Continential IO-240 engine. This engine is a four cylinder, fuel injected, four stroke engine with horizontally opposed air cooled cylinders and heads producing 125 HP at 2800 RPM. The C172N uses an Lycoming O-320-H2AD engine. This engine is a four cylinder, carbureted, four stroke engine with horizontally opposed air cooled cylinders and heads producing 160 HP at 2700 RPM. Most of these characteristics are the same, but you’ll notice that the DA20 engine is fuel injected and the 172 engine is carbureted.

When it comes to fuel injected vs carbureted, I’ll take the fuel injected engine any day. It’s easier to use, gives you better performance, and is safer when it comes to icing conditions. With a carbureted engine, you have to always be conscious of icing conditions and the application of carb heat is essential. In the DA20, I don’t have to be as worried about carb icing. Of course, like any other decision, fuel injection has it draw backs. It’s harder to maintain the system; dirt in the fuel lines can adversely affect fuel flow to the cylinders. Starting the DA20 is also an art you have to master compared to starting the 172. A five year old could start the 172, but starting the DA20 is a little bit more of an experience.

Coming to the control surfaces, there isn’t too much of a difference. All three major control surfaces in the 172 are controlled by cable and pulley. In the DA20, the rudder is controlled by cables, but the ailerons and elevator are controlled by push rods. Inside the cockpit, the 172 uses a yoke control column while the DA20 uses a stick.

When it comes to stick vs yoke, I’m a stick man. There’s just something about the stick that I like more than a steering wheel. While sitting in the DA20 cockpit can be a little weird compared to the 172, I find that it’s easier to operate the aircraft in general. The throttle lever is located comfortably between the two seats whereas the 172 throttle knob is located on the dash. I’m someone who likes to keep my hand on the throttle most of the time, so having to hold my arm out in front me in the 172, just to rest my hand on the throttle, is extremely annoying. In fact, it’s the first thing I noticed when I started flying the Cessnas. I couldn’t figure out why the designers would make such an uncomfortable design decision. Having the stick sit comfortably between your legs is a plus too. To be fair to Cessna, there is much more room in the 172 cabin if you’ve got charts, clipboards, a CFS, an E6B, etc. floating around that you’ll need to access at different times throughout your flight. The DA20 cabin is a little cramped when it comes to this. In the end, I still like the design of the Diamond cockpit better.

I think I’ve gone over most of the major talking points when it comes to Diamond vs Cessna. Now let’s have a look at some of the numbers. Here is a sample of the main V Speeds between both aircraft:

Best angle (Vx) and best rate (Vy) of climb are within 5 knots of each other for both aircraft. The DA20 climbs out at a slower airspeed which makes sense due to its lower max weight and lower fuel capacity. However, maneuvering speed (Va) is higher for the DA20 meaning the control surfaces can be deflected fully at a higher airspeed should you ever need to. This brings up the issue of load factors. The DA20 can sustain G forces of -2.2 to +4.4 Gs while the 172 can sustain -1.7 to +4.4 Gs. Not much of a difference here.

The maximum flaps extended speed (Vfe) for full flaps is a bit higher in the 172 which can come in useful. The 172 is great at dropping altitude and airspeed if you’re too high on final. With flaps down to 40º (or 30º), a nice slip with make it drop like a rock. The DA20 is a bit harder to slow down and reduce altitude at the same time.

The maximum safe operating speed (Vno) is 10 knots higher in the 172 as well, giving it an edge in that category. It’s always nice to have the option of going a bit faster when you need to. To be fair, this speed can be exceeded in calm air should you ever need to. Finally, the top of top speeds to never exceed (Vne) is 4 knots higher in the DA20. This likely won’t ever affect anyone but if you’ve ever come close to Vne, then you’ve got 4 extra knots in the DA20.

Looking at the big picture, you’ll notice the speeds in general are a bit higher for the 172. The DA20 has a less powerful engine, smaller fuel tanks, and a smaller range. When given the choice of which aircraft I would take on a cross country, I’d probably take the 172. It can go further, with almost twice the fuel capacity of the DA20, and it can do so at a faster cruising speed. Now obviously there will be situations where the DA20 will be faster, but in terms of taking passengers and cargo on a cross country, the 172 is more capable in my opinion.

When all is said and done, I’m a DA20 fan. I haven’t flown them in a while but I plan to start again soon. I hope to be able to do the majority of my next 100 hours in a DA20 while working towards my commercial license. They’re a bit trickier to master, but they’re also a bit more fun to play around in. The design choices in my opinion are better in the DA20, but it’s hard to knock the most successful aircraft ever produced. To be clear, I like the 172. I think it’s good at certain things and bad at others. Same goes for the DA20. But when it comes down to which one I would choose on a regular basis for a training aircraft, I’ll take the Diamond.