Fool unmasked?

[PAW]

Alright, I'm putting myself out here like an idiot, but relying on the charity of the "constructive criticism" I've seen in these forums I must ask these questions. I've only flown for two months and have 82 successful flights logged. 90% of those flights originated and terminated from my mobile launch/recovery platform (MLRP)(okay, I made up that acronym). Having seen repeated forum comments about metallic interference e.g. rebar in sidewalks, wristwatches, etc. I need to know:

1. Have I been very lucky and am flirting with disaster?
2. Does the Chevy Silverado possess more plastic than metal?

I only get the "interference/recalibrate" warning when I have traveled 20 miles or so from my last flight location. After recalibration, my flight direction arrow matches my true heading and the home point sets correctly. I use auto take-off and RTH is accurate to less than 2 meters (I always take over control when the AC is overhead).

I hate to give up this MLRP as it gets 16-22 mpg, delivers 355 hp @ 5600 rpm, has a 2068 lb. payload, and is 4WD. But, I don't want to trash my M2P either...

 

[Thomas B]

My initial thoughts are, if it works without error messages then no problem, but if you’re concerned just launch from the ground 10-12 feet away from your truck. The latter is my habit as I get compass error messages when I try to launch from the top or hood of my car.

 

[THE CYBORG]

Got to agree with Thomas B

“ If it works without error messages then no problem, but if you’re concerned just launch from the ground 10-12 feet away from your truck”

 

[BigAl07]

I think you'll appreciate the input from @dirkclod as he is VERY experienced with this exact situation.

 

[timinator]

Taking off from the cover you probably have enough distance such that you are not getting magnetic interference. 82 flights is indicative of a good pattern. Have you ever checked to see what the compass interference is like before takeoff?

 

[zocalo]

Also agree with @Thomas B - no warning, no problem. While RF sources and magnetic materials like iron can cause issues, that's only likely to be an issue if you are either right on top of a major source and/or calibrating your device before pushing the envelope.
Of the two things that can be interfered with, GPS and the link between RC and controller:

If the GPS signal is getting thrown off, once your airborne and away from the source of the interference it'll achieve a stable lock, so initial problems are not that serious. It may cause issues with the RTH location being slightly off, but that's basically where you are most likely going to be in order to recover the drone anyway, so you can intervene (cancel and manual landing) if required.

If the RC-AC link is being disrupted, the RC will inform your of this by beeping and displaying a message on the Go4 screen. If you get this pre-flight, fairly obviously you should find a different take off location, or try adjusting your position relative to the drone. If you're already airborne, it'll do so with plenty of margin before the signal is swamped by noise/interference, so again you can intervene if necessary by retracing your flight path or increasing the distance from any obvious sources of interference. Generally this is only going to be a problem if there is a significant distance between the RC and aircraft, or the antennae are not pointing in the right direction. There's also a corner case where you can actually have too strong a signal, but that's not really applicable here.

 

[AMann]

1. This takeoff pad position is (a) a good idea, (b) the last time this drone will ever fly (c) obviously the idea of a beginner and its good he didn’t really try it.

 

[AMann]

Also keep in mind that if you take off from a table or any other elevated position, your altimeter/barometer will not accurately measure ground distance as it resets whenever you takeoff. I’m not sure, but could this affect landings if the bottom sensors are not working correctly since your drone will think it’s lower than it actually is?

 

[timinator]

Also keep in mind that if you take off from a table or any other elevated position, your altimeter/barometer will not accurately measure ground distance as it resets whenever you takeoff. I’m not sure, but could this affect landings if the bottom sensors are not working correctly since your drone will think it’s lower than it actually is?

This won't make a difference at all.

 

[Thomas B]

Also keep in mind that if you take off from a table or any other elevated position, your altimeter/barometer will not accurately measure ground distance as it resets whenever you takeoff. I’m not sure, but could this affect landings if the bottom sensors are not working correctly since your drone will think it’s lower than it actually is?

The drone will land in expected fashion at launch point even if it is an elevated point. I routinely launch from a picnic table (wooden) and no problems experienced with RTH or manual landing on the table or any othe point. Just FYI of my experience.

 

[Cloudhopper]

DJI Go will only throw an error if the local magnetic field strength is abnormal. It cannot tell you if the direction of the local field is wrong WRT magnetic north.

Taking off with a compromised initial magnetic bearing risks a switch to ATTI mode that could happen at any time during the flight.

You can sweep a pocket compass over the bed of your truck to observe what steel panels do to the local magnetic field (you probably won't like what you see!).

 

[AMann]

This won't make a difference at all.

Think about it- If your bottom sensors are not working and your drone is auto lending, the barometer/altimeter will tell the drone that it’s at ground level at the elevated takeoff height, and the motors will shut off too soon making your drone fall the remainder of the distance. It’s sort of like what happened to the Mars Polar Lander.

 

[AMann]

The drone will land in expected fashion at launch point even if it is an elevated point. I routinely launch from a picnic table (wooden) and no problems experienced with RTH or manual landing on the table or any othe point. Just FYI of my experience.

But what if it’s an emergency landing somewhere else? I was just throwing out an idea if someone is using a mobile platform and the platform moves during the flight or the drone has to land at a different location due to low battery or something like that.

 

[Thomas B]

Think about it- If your bottom sensors are not working and your drone is auto lending, the barometer/altimeter will tell the drone that it’s at ground level at the elevated takeoff height, and the motors will shut off too soon making your drone fall the remainder of the distance. It’s sort of like what happened to the Mars Polar Lander.

See my post, #10, above. I can imagine the concern, but have not seen it in practice with my Spark, my MPP nor my M2P. It lands where I tell it, never had a motor shutoff in the air whether RTH or manual landing in any location.

 

[timinator]

Think about it- If your bottom sensors are not working and your drone is auto lending, the barometer/altimeter will tell the drone that it’s at ground level at the elevated takeoff height, and the motors will shut off too soon making your drone fall the remainder of the distance. It’s sort of like what happened to the Mars Polar Lander.

The motors will not shut off at some predetermined point from takeoff. The aircraft will continue to descend until it touches down. The motors only shut off after downward stick inputs for three seconds with zero descent (vertical speed) detected.

 

[timinator]

Sorry, missed the autolanding part but the logic is still the same - the aircraft knows when it is ascending or descending so it won't shut down the motors while there is still some vertical speed.

 

[FormerMember07122019_2]

I think I have the exact same bed cover (bakflip) on my Ford F-150. I believe it is made of aluminum and composite plastic and might be why it is not causing a problem.

 

[BigAl07]

The Flight Controller (FC) has lots of checks & balances and several things have to be 'Green' before it will shut off the motors. Fortunately "altitude" is not one of them.

Until the aircraft "senses" no motion and you have commanded "Down Stick" it's not going to kill the motors.

 

[AMann]

I understand, Then the only thing that will happen sooner is it will start to slow its descent at a slightly higher level than normal, right? Obviously that wouldn’t affect the landing at all.

 

[IShouldBeWorking]

I do the same thing from the plastic bed cover of my Toyota Tundra. I've been doing it for years with my original Mavic Pro and now my Mavic 2 Pro. Never had a single problem. Not even so much as a warning.

Although, sadly I only get 12 to 13 mpg out of the Tundra as a mobile launch platform.