I’m a bit surprised that you’ve chosen such a simple and cheap flight controller for such an ambitious task. I have really bad experiences with Matek H743-Wing. The CPU is of course great, but the whole FC too cheap and cutting corners. Baro is not protected, not much redundancy, too simple power supply circuitry, the board not secured against environment factors (and air pressure issues can be relevant at those speeds).
I haven’t had any issues with Matek boards. In my experience they are much more suitable for small planes than offerings from CubePilot or CUAV as they have their own BEC for servos which makes it much easier to power. Their current measurement setup (on wing boards) is also better than what CubePilot provides. The only meaningful improvement from them is vibration isolation which typically isn’t critical on foam planes.
The loiter radius is mathematically correct. However, you must add the maximum wind speed at which you still want to fly. The center of the loiter circles is a fixed point that does not move with the wind (except in CIRCLE mode). On the arc above ground, you fly with the wind at almost airspeed + wind speed, and on the opposite side at airspeed - wind speed.
Why don’t you fly the aircraft manually for the maiden flight (or, if that’s not possible because it becomes too small too quickly in this case) in autotune mode? The latter behaves like FBWA anyway.
This allows you to improve the PID values for attitude control before you start working on the autothrottle modes.
If you enter the loiter circle immediately in takeoff mode, it may work, but it may not. This is because correctly adjusted speed and TECS parameters are important for speed and altitude control, which can only work well with good attitude control.
I do agree with with @LupusTheCanine regarding Matek board, they are very reliable.
Barometerer is protected by a piece a foam to filter wind and direct airflow noise, maybe its not ideal but it has been working fine for me for cursing up to 125kmh. Do you have clues that it would not be enought for higher crusing speed , up to 250kmh in my case ?
There is no redundancy indeed but I don’t seen how a power failure could happen since it is direct wiring from P50B cells, with only 1 xt60 connector.
@maciek252 the main drawnback of this well known matek H743-WING is the lack of thermal control and active heating. This is the price to pay for such a compact and cost effective FC, with multiples embedded BEC and IOs.
Regarding finding the best location that fit with TBS MOJITO, it is all about the battery size and weight… each build is very different. In my case, it did fit in the frame this way:
The main defect of this implementatio was the GPS+Compass location. I did it a quick and dirty way, but it was too close from other electronic component and too close from ESC power cable…
@Rolf Your are probably right regarding the maiden flight sequence and proposal to flight manual mode first.
On previous flight that led to crash, I did prefer to use autotakeoff, since it had always worked fine for maiden (for sub 200kmh vehicule).
And I didn’t voluntarily use RTL mode, it is just the default behavior of auto-takeoff once altitude and distance are reached.
By the way, i would love to have a setting to choose the next flight mode after altitude and distance are reached when using autotakeoff mode:
RTL (default)
FBWA
ACRO
STABILIZE
MANUAL (risky)
I am currently doing some training to fly in manual mode with FPV google, to do upcoming maiden in manual mode.
@Rolf would you consider help me to add implement & test this feature:
Emit a alert message to the pilot like : [GROUND/AIR]SPEED ABOVE MAX AIRSPEED, SLOW DOWN TO <AIRSPEED_MAX>
The idea behind this feature is to notify pilot while flying that loss of control may occur due to speed scaling affecting servo gains.
Notification may occurs when ground speed (or airspeed if available) is 25% (TBD) above AIRSPEED_MAX
Another benefit would be to leave a message in bin logs order to ease post processing and highlight the misconfiguration on AIRSPEED_MAX. It would have save me from crashing…
I had a situation where a faulty ExpressLRS receiver was causing all the GPS to loose signal randomly with Matek H743 Wing (and also Kakute H743 Wing but not Holybro Durandal). Took me ages to track this down. Also the SD card slot without a click is bad. And even soldering the pins (and the cables connecting the boards) on your own and not during the manufacturing process makes it more likely to fail. I prefer the solution like in Kakute H743 Wing, where there is a connector between two boards and not cables.
If you are flying with a digital OSD, it is best to place OSD1_ASPEED_EN in a clearly visible position in the OSD. This will give you the airspeed value being used by TECS (fused value). You can use it regardless of whether you are using none, one, or two airspeed sensors.
Of course, you could write a LUA script that displays the message “Overspeed” when a certain airspeed is exceeded. However, I don’t think that makes much sense if you can display the airspeed in the OSD.
Do you have telemetry to the ground station? I find it helpful to have a second person monitoring flight datas during maiden flights.
interesting to hear the “not best choice” comment. My 1.5m big versa / kraken wing flew very well with ardupilot 3.??? 10y ago. It definitely wasnt doing 200kph, but it flew very well. Did a few 40km round trips also.
