At just so happened that, on the German forum, someone posted something about the Tercel. I followed a link and wound up on their website. Skipping the marketing parts I quickly found myself reading the technical specs and starting to scratch my head. I found some glaring discrepancies between what is on the manufacturer's homepage, what is written in the POH and what my own experience tells me.
Curiosity piqued, I visited the homepages of other manufacturers and got very mixed results. Where available I downloaded the POHs and tried to ascertain the accuracy of technical specs given on the internet.
I do NOT want to denigrate any particular type of gyro. They all have their pros and cons and, across the board, fly reasonably well. However, I would like for other people to become aware of the fact that even technical specs given by the manufacturer need to be taken with a grain of salt and questioned.
Without further ado, this is what I found:
The empty weight of the Tercel is given as 285 kg and the MTOW as 560 kg. Curiously enough, payload is not the expected 275 kg (the difference) but only 240 kg. That's what got me to consult the POH which is available for download off the webpage. Here, empty weight is 295 kg, MTOW is 560 kg and payload is 265 kg, the expected difference between MTOW and empty weight.
Vmin on the webpage is 40 km/h while it is 60 km/h in the POH. Vne is 210 km/h on the webpage and 200 km/h in the POH.
Climb rate is speced at 1200 fpm, the same on webpage and POH. However, from my own (admittedly limited) experience, it would be pretty hard to coax 1200 fpm sustained climb rate at MTOW from a Tercel (at standard atmospheric conditions, of course). A Tercel pilot on the forum surmised that it might be the solo climb rate. That would be more realistic, of course, but still misleading. There are certain definitions for how to measure particular quantities. And climb rate is to be given at MTOW. The manufacturer may choose to give climb rate figures for other configruations, too, but that it is purely optional. If nothing else is specified, a climb rate figure applies to MTWO and ISA.
Landing distance is given as 0-5 m. Here we have another problem with definitions. Landing distance (in the absence of any other modifiers) is to be quoted for a dry, level asphalt surface, at MTOW, over a 50 ft obstacle, windstill and ISA. Clearly, the 0-5 m from the website include only the landing roll. The POH is better in this respect and gives 45-55 m. The question begs, however, which one it is? 45 or 55 m. Still, even this number is quite short and I question if it is really possible to land over a 50 ft obstacle and bring the gyro to a stop in 45 m. The point is, it has to be done using average pilot skills and the procedure set forth in the POH. So no stunts or loading the rotor. Just standard procedure.
Take-off distance is given on the web as 100 m. In the POH it is 115. This sounds reasonable albeit a bit short in my experience. At MTOW, and using the procedure given in the POH I would not want to rely on clearing a 50 ft tree 115 m down the runway. The BCAR Section-T specifies a safety factor of 1.5 for the quoted take-off distance in the manual. I doubt whether this factor was applied (although the manual was not meant to be to Section-T standards).
Next we come to cruise speeds. Before I do, however, I want to stress the importance of properly calibrating the ASI. I have seen deviations of 10% on my MT03. So, while seeing 140 km/h on my ASI, I was really only doing 126 km/h. A similar problem might exist with other gyros. Therefore, in the absence of an ASI calibration curve, I have no way of knowing the calibrated airspeed, which I need to know accurately for my flight planning.
Unfortunately, for the Tercel, no calibration curve is given in the POH. Cruise speed is cited at 140 km/h at 75% power, at a fuel flow of 20 l/h. According to my (limited) experience, these numbers are too optimistic. You may be seeing 140 km/h on the ASI but in actuality I found cruise speeds more in range between 110-130 km/h at 75% power and MTOW. The fuel flow of 20 l/h is that of a Rotax 914 at 75% continous power. The Tercel has a turbo boosted Rotax 912 which outputs a mayimum of 135 HP. I wonder if, at 75%, fuel flow should not be higher than 20 l/h.
-- Chris.
Curiosity piqued, I visited the homepages of other manufacturers and got very mixed results. Where available I downloaded the POHs and tried to ascertain the accuracy of technical specs given on the internet.
I do NOT want to denigrate any particular type of gyro. They all have their pros and cons and, across the board, fly reasonably well. However, I would like for other people to become aware of the fact that even technical specs given by the manufacturer need to be taken with a grain of salt and questioned.
Without further ado, this is what I found:
The empty weight of the Tercel is given as 285 kg and the MTOW as 560 kg. Curiously enough, payload is not the expected 275 kg (the difference) but only 240 kg. That's what got me to consult the POH which is available for download off the webpage. Here, empty weight is 295 kg, MTOW is 560 kg and payload is 265 kg, the expected difference between MTOW and empty weight.
Vmin on the webpage is 40 km/h while it is 60 km/h in the POH. Vne is 210 km/h on the webpage and 200 km/h in the POH.
Climb rate is speced at 1200 fpm, the same on webpage and POH. However, from my own (admittedly limited) experience, it would be pretty hard to coax 1200 fpm sustained climb rate at MTOW from a Tercel (at standard atmospheric conditions, of course). A Tercel pilot on the forum surmised that it might be the solo climb rate. That would be more realistic, of course, but still misleading. There are certain definitions for how to measure particular quantities. And climb rate is to be given at MTOW. The manufacturer may choose to give climb rate figures for other configruations, too, but that it is purely optional. If nothing else is specified, a climb rate figure applies to MTWO and ISA.
Landing distance is given as 0-5 m. Here we have another problem with definitions. Landing distance (in the absence of any other modifiers) is to be quoted for a dry, level asphalt surface, at MTOW, over a 50 ft obstacle, windstill and ISA. Clearly, the 0-5 m from the website include only the landing roll. The POH is better in this respect and gives 45-55 m. The question begs, however, which one it is? 45 or 55 m. Still, even this number is quite short and I question if it is really possible to land over a 50 ft obstacle and bring the gyro to a stop in 45 m. The point is, it has to be done using average pilot skills and the procedure set forth in the POH. So no stunts or loading the rotor. Just standard procedure.
Take-off distance is given on the web as 100 m. In the POH it is 115. This sounds reasonable albeit a bit short in my experience. At MTOW, and using the procedure given in the POH I would not want to rely on clearing a 50 ft tree 115 m down the runway. The BCAR Section-T specifies a safety factor of 1.5 for the quoted take-off distance in the manual. I doubt whether this factor was applied (although the manual was not meant to be to Section-T standards).
Next we come to cruise speeds. Before I do, however, I want to stress the importance of properly calibrating the ASI. I have seen deviations of 10% on my MT03. So, while seeing 140 km/h on my ASI, I was really only doing 126 km/h. A similar problem might exist with other gyros. Therefore, in the absence of an ASI calibration curve, I have no way of knowing the calibrated airspeed, which I need to know accurately for my flight planning.
Unfortunately, for the Tercel, no calibration curve is given in the POH. Cruise speed is cited at 140 km/h at 75% power, at a fuel flow of 20 l/h. According to my (limited) experience, these numbers are too optimistic. You may be seeing 140 km/h on the ASI but in actuality I found cruise speeds more in range between 110-130 km/h at 75% power and MTOW. The fuel flow of 20 l/h is that of a Rotax 914 at 75% continous power. The Tercel has a turbo boosted Rotax 912 which outputs a mayimum of 135 HP. I wonder if, at 75%, fuel flow should not be higher than 20 l/h.
-- Chris.