Comments on Dynon D-10 EFIS - I performed a short evaluation flight on a Dynon D-10 EFIS with software 1.04.00, installed in Mark Nielsen’s RV-6, N121MN. The flight was from Green Bay on July 28, 2003. I had previously ordered the Dynon EFIS, but I wanted to evaluate it in flight before confirming the order. In summary, I will confirm my order, but there are some aspects of the display and user interface that should be improved. The following comments were forwarded to Dynon for their consideration.
Read on for more.
The EFIS was installed in front of the left seat, but I was in the right seat for the flight, which put me about 45 deg off axis. I did lean my head over in front of the left seat occasionally to get a better view. The perceived display contrast was slightly lower from 45 deg off axis than it was when viewed from the left seat. The ideal viewing angle appeared to be about 35 deg off axis or less.
Sunlight readability - even with the off-axis viewing angle, the sunlight readability was quite good. The aircraft was manoeuvred to place the sunlight on the display - the display was still quite readable. In fact the sunlight readability was better than I have seen with the EFIS in some Transport Category aircraft (Challenger 604 and Canadair Regional Jet).
The aircraft was also manoeuvred to place the sun on the nose (this was about one hour before sunset, so the sun was low on the horizon). This reduced the perceived display contrast, but the display was still readable.
Attitude Indicator - The attitude indicator appeared to be correct and stable. There was about a 10 deg lag between the displayed and actual horizons during a roll with full aileron deflection roll, but this magnitude lag is also found on fighter aircraft with inertial reference systems and multi-million dollars of avionics. The displayed and actual horizons matched again as soon as the roll rate decreased to values typical of IFR flight.
It was noted that the attitude display was very difficult to interpret when the nose was very high or very low, as the display was either all blue or all brown, and it was not possible to determine which way to roll to the horizon. The only clue as to which way the horizon is comes from the bank angle pointer, which is very inconspicuous. EFIS displays found on Transport Category aircraft address this issue in two ways. First, they are designed to always show part of the horizon, no matter what the pitch attitude is. Second, they have a series of large red chevrons that come into view at about 30 deg nose up and 20 deg nose down (typical values). These chevrons point towards the horizon - they serve to tell the pilot which way to move the nose, and they help indicate which way is the shortest way to roll to get to the horizon. It is strongly recommended that the attitude display be modified to always show part of the horizon, and to have large red chevrons at high or low pitch attitudes.
The horizontal white lines on the pitch attitude scale had good contrast, and were easy to see even when the visibility was impaired by heading into the sun. However, there was no white line at the zero degrees pitch attitude position - this position was indicated by the transition from brown to blue on the attitude display. The zero degrees pitch attitude position was difficult to see quickly in low contrast conditions, such as when heading into the sun. It is recommended that there be a white line at the transition from brown to blue. If necessary, this line could be the same length as the other lines that comprise the pitch scale, rather than extend across the whole display.
The bank index pointer is a hollow triangle, which was slightly too inconspicuous. It may be better to fill in the triangle to make it stand out a bit more. It is recommended that a solid bank index be tested to determine whether it is an improvement.
Airspeed display - The airspeed digital readout was easy to read. The tape was moderately easy to read, and the amber and red coloured bands at the high speed end provide excellent visual cues that the speed was approaching critical values. In the future, once the AOA function is working, it would be useful to add a red low speed cue as well, driven by the AOA. The idea would be to use the difference between the current AOA and the AOA at the stall to position the top of the low speed cue (a red band). If the actual AOA was equal to the stall AOA, the top of the low speed cue would be equal to the current speed. If required, I can probably provide the equations necessary to calculate the position of the top of the low speed cue as a function of the AOA.
Altimeter display - The altimeter was difficult to use. The thousands digits on the digital readout were quite readable, but the hundreds and tens digits were much smaller, which made them difficult to read quickly. The digits on the altitude tape were so small that it was difficult to read them quickly. The altitude tape appeared to be a bit over damped, making it slow to react to altitude changes. It was much, much easier to accurately fly a desired altitude using the round dial altimeter than it was when using the altitude tape on the Dynon D-10. It is recognized that there is only a limited amount of display area that can be dedicated to the altimeter display, so it may be difficult to make major improvements. If possible, it is recommended to increase the size of the digits for the hundreds and tens in the altitude digital readout. It is also recommended, if possible, to slightly increase the size of the digits beside the altitude tape. The damping of the vertical tape should be reviewed to ensure it responds to altitude changes without undue delay.
It was noted that the altimeter setting is only displayed while it is being adjusted. For IFR operations, it is recommended that there be an option to allow full time display of the altimeter setting.
Vertical speed display - the vertical speed display consists of a digital readout of vertical speed, with an arrow that pointed up or down. It was very difficult to use it to fly a desired vertical speed, as when flying an instrument approach. But, there is only a limited amount of screen real estate, so it would be difficult to make major improvements.
Heading Display - The remote compass module had only been calibrated the day before, so Mark Nielsen did not yet have enough flight time on it to determine how well it really worked. But the initial impression was that it worked well, and appeared to correspond reasonably closely to the magnetic compass.
The heading index (i.e. the thing that indicates the current heading) is a small, upwards pointing white triangle. The heading bug is the same size, colour and shape, but is flipped 180 degrees, so it is pointing downwards. The heading bug was somewhat inconspicuous, and could benefit from being somewhat larger.
Potential Software Version for IFR installations? - The concerns about the attitude display in unusual attitudes were discussed quickly with Doug Medema (Dynon VP of Engineering) at OSH. He said that the software was bumping up against memory limitations, which would seriously constrain the types of changes that could be made.
The current software provides a large number of possible display items. However, anyone who intends to use the D-10 in an IFR application should have other instruments installed to display many of these functions, to mitigate the potential failure of the EFIS system. It may be advantageous to eventually develop a parallel software version that was intended for IFR use. This version would not have the code for some display items, as those items should be displayed on other instruments (e.g. altimeter, accelerometer, rate of turn, slip ball, etc). Dropping some display items from the IFR software version might free up space to address items such as improved attitude display when in unusual attitudes - i.e. adding red chevrons and making part of the horizon always visible.
