By Rick Durden
When pilots argue which general aviation trainer is best there are usually one or two more opinions on the subject than there are speakers. If someone asks what trainer those present flew, the almost unanimous answer is the Cessna 150 or its step-brother, the 152. But it has been more than 20 years since the last 152 flew away from the assembly line in Winfield, Kan., and since then, companies seeking to build two-place trainers have had a difficult time of it. One notable exception is Diamond Aircraft with its steady-selling DA20-C1, formerly known as the Katana, now called the Evolution or Eclipse (for the better equipped model).
But now Diamond is facing some determined competition. Pilots and flight schools currently in the market for a trainer that doesnt lug around a couple of extra seats like the Cessna Skyhawk or New Piper Warrior have two more options: the 125-hp Liberty XL2 and the 160-hp Symphony 160. (At this writing, Symphony was attempting to reorganize in bankruptcy. Well presume Symphony manages to place its financial house in order and, using the Cessna 150/152 as a baseline, compare the safety of these newest two-seat trainers to each other.)
The Training Environment
To evaluate the probable level of safety of these new airplanes, its appropriate to look at their risk environment. The AOPA Air Safety Foundations 2005 Nall Report shows that single-engine aircraft accidents are most likely to involve the maneuvering, takeoff/climb, VFR-into-IMC or descent/approach flight phases. Because these airplanes will be used for training, that accident history is relevant: There, weather-related accidents were almost nonexistent; the true risk was on go-arounds, landings, the descent/approach and takeoff/climb flight phases, and, amazingly enough, preflight and taxi.
Fatal accidents clustered heavily into those associated with maneuvering, landing and descent/approach operations. Maneuvering and weather accidents were almost invariably fatal, as one might expect with ground impact being at a significant speed. Close behind in fatal accidents was descent/approach accidents, with about 50 percent of landing accidents being fatal.
So, what can we expect from the new breeds safety? Out of the box, well point out that the Cessna 150/152 always had an accident and fatality rate well below the average for single-engine airplanes, probably due to its robust structure, relatively slow stall speed and use in the generally safer training environment. The Diamond DA20 fleet has been in the field long enough to rack up over two million flight hours and has only four fatal accidents. That works out to .2 per 100,000 flying hours, the lowest by far of any general aviation aircraft in widespread use and well below the overall average of 1.31 fatals per 100,000 flying hours. Diamond has set the standard. The 150/152 is comparatively in the dust behind. What can we expect from the Symphony and Liberty?
When it comes to risk of accident, a low stall speed may help a pilot remain in control of the airplane and avoid an accident-or keep it survivable if an impact does occur. The DA20-C1s stall speed is 44 knots. That by itself cannot explain the low accident rate, because the stall speed of a Cessna 152 is only slightly lower at 43 knots. The Liberty also stalls at 43 knots, with the Symphony at 51, a speed more consistent with the old Grumman AA-1 Trainer, which did not have an enviable accident rate.
If low stall speeds are not, by themselves, the variable that affects accident rate, we are willing to go out on a limb and suggest that the use of control sticks, instead of wheels, with their more intuitive input and response and the lesser likelihood of inappropriate carryover from driving an automobile to flying when it most matters, may be a factor. Also, instructors have long recognized that students learn more and do a better job of flying when they can see well, having fewer successful lessons on hazy days. We cannot help but wonder whether the panoramic view from a canopy helps a pilot better handle difficult situations.
Because trainers are often flown with two aboard, the useful load is important because-in the real world-the airplanes are more likely to be overloaded. This means they are also more likely to stall or hit something after takeoff. With full fuel, the 152 has a useful load of about 350 pounds, not enough for two adult males. The Symphony and DA-20 are the best in this category, at 460 pounds. The Liberty, at 311 pounds, will have to be flown with partial fuel in training situations. The 152, Liberty and Symphony all have large baggage areas, something that we have observed leads to overloading. The Eclipse has a very small baggage area making it less likely to be overloaded. We think Diamonds approach to avoiding overloading a small airplane may have contributed to the very low accident rate for the DA20.
Fuel mismanagement annually leads to a number of airplanes becoming unintended gliders, with varying outcomes, some of them fatal. Historically, the fewer fuel selection decisions available to the pilot, the lower the chance of an accident. All three trainers, as with the Cessna 150/152, have a dirt-simple fuel system. The choices are on or off.
Related to the fuel mismanagement accidents is the fact that a lot of pilots either dont know how to lean the mixture in cruise or refuse to do so, often from bad instruction. As a result, they are more likely to run out of fuel. This will probably be the case for some folks in the Symphony or the Eclipse. It is less likely to occur in the Liberty because the engine is equipped with FADEC. While we arent crazy about the fact the pretakeoff and runup checks require a total of some 45 separate checklist items because of the FADEC-which will lead to pilots skipping items-we like FADEC a great deal. It automatically leans the mixture so that the pilot can be assured of matching book fuel burns for flight planning purposes.
All three trainers have fuel injected engines, eliminating one of the powerplant management tasks facing the pilot of the Cessna 150: carburetor icing. While induction system icing could occur, it is so rare as to probably not be a consideration in these airplanes.
The POHs of all the trainers contain some erroneous information simply because manufacturers copy old material, which may cause accidents. Some call for reduced flaps in crosswind landings, which means that pilots are more likely to lose control on rollout than if they had touched down slower, with full flaps. The DA20 POH calls for full rich mixture upon starting the descent, which may cause power loss or make the difference between running out of fuel and making the runway.
The BRS parachute is available on the Symphony. With the larger engine on the Symphony as opposed to the Eclipse and Liberty, the weight of the BRS parachute is not as much of a consideration as it might be on the lighter airplanes. The BRS has saved lives and will continue to do so. Having one extra, very effective, safety device in the airplane that can be used when all else has failed, and which does not otherwise increase the risk of an accident, is a very good thing, in our opinion.
A small thing, but for airplanes used for training the one thing that a student does that causes accidents and that an instructor cannot undo is to misuse the brakes. Thirty years ago, the Chinese Nanching CJ-6 trainer had a button on the instructors stick that disabled the students brakes. Why cant such a simple thing be on current U.S. trainers?
The reality is that there will be accidents. How the airplane is designed and built to protect the occupants in the expected calamities matters. Maneuvering and weather-related crashes seem to occur at such speeds that even the most crashworthy structure isnt going to help. For approach, landing and takeoff events, where speeds are near the stall, crashworthiness means the difference between life and death.
The Cessna 150/152 did a pretty good job of protecting its occupants, especially once Cessna took the step to make its optional three-point shoulder harnesses standard, years before the FAA mandate. A four-point harness would have been better and was used on the Aerobat. While the cabin is small, it is quite strong, with what amounts to a box around the occupants, between the landing gear, firewall and wing spars. A lot of properly restrained pilots survived some significant impacts. Helping them out was that the metal fuel tanks were out in the wings, between the spars, and the fuel lines ran along the strongest parts of the structure, which helped protect against post-crash fire. Do these new trainers do crashworthiness any better?
The seats in the new trainers are fixed, which should eliminate the seat-slip accident risk, and the restraint systems are four-point, a definite step up from the 150 series. We would prefer that inertia reel shoulder harnesses be standard fare and were, frankly, dismayed to find that they were not, except on the Symphony. Overlooking such a basic safety installation causes us to wonder if other, less obvious shortcuts were taken. The Symphony has load attenuating devices under the occupant seats, needed because of its stall speed. Otherwise, because of the slow stall speed, the Liberty and DA20 did not have to do dynamic seat impact tests. Not having impact-absorbing seats, or at least seat cushions made of the current, load attenuating materials, is a step backwards, in our opinion.
Because each is a fixed-gear airplane, the gear will do a lot to absorb vertical impact forces. That is valuable because a large proportion of pilots making an emergency landing actually stall the airplane well before touchdown, leading to major vertical impact loads and more than a few badly compressed spines. The low stall speeds of the DA20 and Liberty (and Cessna 150/152) should bode well for protecting the occupants even if the restraint systems are not top of the line.
Even though these are small airplanes, there is space for occupants to flail during an impact sequence, reducing the chance that they will hit interior structure. Using control sticks instead of yokes means that there is not an object sticking out of the panel to impale occupants during a sudden stop. While sticks are an improvement, they are still behind the times when it comes to crashworthiness; side sticks should have been used. For the prices for these airplanes, we expected that more thought would have gone into occupant restraint and protection. The sticks in the DA20 are a part of the seats themselves, and unless they are frangible, they may well emasculate a male in a forward impact event.
And The Winner Is…
Which is the safest? Right now, the DA20 has a wide lead over every GA aircraft ever built in avoiding accidents. We want to watch accident stats to see how it does on those rare occasions it does come to grief, and how it protects its occupants. We like the Liberty because it had to go through the tough current certification requirements for occupant protection (but not for seat testing). And we like the Symphony because it went through dynamic seat testing and has the BRS parachute.
If we have to ride through an accident, we want the inertial reel shoulder harnesses on the Symphony, and the strong steel tube framework chassis of the Liberty, but we also want seat-belt mounted airbags and side sticks so that we are less likely to hit the interior structure.
Diamond is doing something right with its single-engine airplanes, and is remarkably successful in accident avoidance. If it can be identified and bottled, wed like to buy some. However, for occupant protection in a crash, each manufacturer had a chance to step up to the state of the art with side sticks, air bags, inertial reel harnesses and heavily protected fuel systems.We feel that they only went part of the way. Well be watching the accident statistics to see if they have made safer trainers than the venerable Cessna 150.